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Sample records for reflected shock waves

  1. A note on weak shock wave reflection

    NASA Astrophysics Data System (ADS)

    Viero, D. P.; Susin, F. M.; Defina, A.

    2013-09-01

    This work discusses the possibility of reconstructing, both numerically and experimentally, the steady state flow field and shock reflection pattern close to the triple point of von Neumann, Guderley and Vasilev reflections. First, a criterion for the orientation of shock wave fronts, even in the case of subcritical/subsonic flow downstream the front, is introduced and formalized. Then, a technique for obtaining a close view of the above reflection patterns centered about the triple point is described and a numerical example, within the framework of shallow water flow, is presented and discussed.

  2. On Reflection of Shock Waves from Boundary Layers

    NASA Technical Reports Server (NTRS)

    Liepmann, H W; Roshko, A; Dhawan, S

    1952-01-01

    Measurements are presented at Mach numbers from about 1.3 to 1.5 of reflection characteristics and the relative upstream influence of shock waves impinging on a flat surface with both laminar and turbulent boundary layers. The difference between impulse and step waves is discussed and their interaction with the boundary layer is compared. General considerations on the experimental production of shock waves from wedges and cones and examples of reflection of shock waves from supersonic shear layers are also presented.

  3. The physical nature of weak shock wave reflection

    NASA Astrophysics Data System (ADS)

    Skews, Beric W.; Ashworth, Jason T.

    2005-10-01

    For weak shock waves and small wedge angles the application of three-shock (von Neumann) theory gives no physically realistic solutions and yet experiments clearly show a pattern of reflection of three shocks meeting at a triple point. This disagreement is referred to as the von Neumann paradox, and the reflection pattern as von Neumann reflection (vNR). Some recent numerical computations have indicated the existence of an expansion wave immediately behind the reflected wave as originally suggested by Guderley over fifty years ago. Furthermore, a recent solution of the inviscid transonic equations has indicated the possible existence of a very small, multi-wave structure immediately behind the three-shock confluence. A special shock tube has been constructed which allows Mach stem lengths to be obtained which are more than an order of magnitude larger than those obtainable in conventional shock tubes. Schlieren photographs do indeed show a structure consisting of an expansion wave followed by a small shock situated behind the confluence point, with some indication of smaller scale structures in some tests. This indicates that some of the earlier models of vNR, in the parameter space tested, are incorrect. The size of the region influenced by this small wave system is about 2% of the Mach stem length and it is therefore not surprising that it has not been detected before in conventional shock tube facilities.

  4. A new configuration of irregular reflection of shock waves

    NASA Astrophysics Data System (ADS)

    Gvozdeva, L. G.; Gavrenkov, S. A.

    2015-06-01

    A new configuration of shock waves has been found in the reflection of shock waves in a stationary supersonic gas flow in addition to the wellknown regular and Mach reflections. This new three-shock configuration occurs with a negative angle of reflection and Mach numbers greater than 3 and an adiabatic index smaller than 1.4. It has been shown that this new configuration is unstable and leads to a radical change of the total flow pattern. The emergence of this new kind of instability can negatively affect operation of aircraft and rocket engines due to the failure of the flow to be as conventionally predicted.

  5. Classification of pseudo-steady shock wave reflection types

    NASA Astrophysics Data System (ADS)

    Semenov, A. N.; Berezkina, M. K.; Krassovskaya, I. V.

    2012-07-01

    Classification of various types of the reflections of a shock wave over a straight wedge is proposed. The idea about entire reflection phenomenon as a result of interaction of two processes—the shock wave reflection process and the flow deflection process—serves as a basis for the classification. To recognize the types of reflection, changes in the shapes of the reflected wave, Mach stem, and contact surface (slipstream) are taken into account. The boundaries and domains of existence for various types of reflection configuration are reported. New terms for some types of reflection are proposed. The domain of irregular non-Mach reflection is analyzed carefully. It is shown that the von Neumann reflection pattern can result from not only the weak shock reflection but also the strong shock reflection over thin wedges. Shadowgraph images of different types of irregular reflection that illustrate the suggested classification are presented. Emphasis is placed on near-wall behavior of the contact discontinuity in the Mach configuration.

  6. Shock wave reflection over convex and concave wedge

    NASA Astrophysics Data System (ADS)

    Kitade, M.; Kosugi, T.; Yada, K.; Takayama, Kazuyoshi

    2001-04-01

    It is well known that the transition criterion nearly agrees with the detachment criterion in the case of strong shocks, two-dimensional, and pseudosteady flow. However, when the shock wave diffracts over a wedge whose angle is below the detachment criterion, that is, in the domain of Mach reflection, precursory regular reflection (PRR) appears near the leading edge and as the shock wave propagates, the PRR is swept away by the overtaking corner signal (cs) that forces the transition to Mach reflection. It is clear that viscosity and thermal conductivity influences transition and the triple point trajectory. On the other hand, the reflection over concave and convex wedges is truly unsteady flow, and the effect of viscosity and thermal conductivity on transition and triple point trajectory has not been reported. This paper describes that influence of viscosity over convex and concave corners investigated both experiments and numerical simulations.

  7. Radiative transfer effects on reflected shock waves. II - Absorbing gas.

    NASA Technical Reports Server (NTRS)

    Su, F. Y.; Olfe, D. B.

    1972-01-01

    Radiative cooling effects behind a reflected shock wave are calculated for an absorbing-emitting gas by means of an expansion procedure in the small density ratio across the shock front. For a gray gas shock layer with an optical thickness of order unity or less the absorption integral is simplified by use of the local temperature approximation, whereas for larger optical thicknesses a Rosseland diffusion type of solution is matched with the local temperature approximation solution. The calculations show that the shock wave will attenuate at first and then accelerate to a constant velocity. Under appropriate conditions the gas enthalpy near the wall may increase at intermediate times before ultimately decreasing to zero. A two-band absorption model yields end-wall radiant-heat fluxes which agree well with available shock-tube measurements.

  8. Visualization of shock-wave formation processes during shock reflection at obstacles with multiple steps

    NASA Astrophysics Data System (ADS)

    Kobayashi, Susumu; Adachi, Takashi

    According to standard textbooks on compressible fluid dynamics, a shock wave is formed by an accumulation of compression waves. However, the process by which an accumulated compression wave grows into a shock wave has never been visualized. In the present paper, the authors tried to visualize this process using a model wedge with multiple steps. This model is useful for generating a series of compression waves and can simulate a compression process that occurs in a shock tube. By estimating the triple-point trajectory angle, we demonstrated visually that an accumulated compression wave grows into a shock wave. Further reflection experiments over a rough-surface wedge confirmed the tendency for the triple point trajectory angle χ to reach the asymptotic value χs in the end.

  9. Auto-ignition of hydrocarbons behind reflected shock waves.

    NASA Technical Reports Server (NTRS)

    Vermeer, D. J.; Meyer, J. W.; Oppenheim, A. K.

    1972-01-01

    The paper reports on the study of auto-ignition of hydrocarbon-oxygen mixtures behind reflected shock waves. Because of their bearing on the problem of knock in internal combustion engines, n-heptane and iso-octane were chosen as the combustible species. Their stoichiometric mixtures with oxygen had to be diluted with 70% argon to reduce the influence of the boundary layer. Photographic records demonstrated the existence of two different modes of ignition, as has been previously established for the hydrogen-oxygen system. The pressure-temperature limits between these regions of mild and strong ignition were determined. From the same experimental tests, induction time data were obtained over the pressure range of 1-4 atm and the temperature interval of 1200-1700 K.

  10. Microscopic structure of the Mach-type reflection of weak shock waves

    NASA Astrophysics Data System (ADS)

    Walenta, Z. A.

    The purpose of the present work was to investigate the microscopic structure of the three-shock inter-action region generated in a low-density shock tube during the Mach-type reflection of a weak shock wave. The experimental conditions corresponded to the case when Von Neumann's theory fails to predict the existence of reflection while Guderley's theory predicts the presence of a rarefaction wave behind the reflected shock. The experiment shows that under such conditions the Mach-type reflection does exist, and no rarefaction wave is present. A possible reason for this disagreement is the influence of viscosity, neglected in Von Neumann's and Guderley's theories.

  11. Symmetry of spherically converging shock waves through reflection, relating to the shock ignition fusion energy scheme.

    PubMed

    Davie, C J; Evans, R G

    2013-05-01

    We examine the properties of perturbed spherically imploding shock waves in an ideal fluid through the collapse, bounce, and development into an outgoing shock wave. We find broad conservation of the size and shape of ingoing and outgoing perturbations when viewed at the same radius. The outgoing shock recovers the velocity of the unperturbed shock outside the strongly distorted core. The results are presented in the context of the robustness of the shock ignition approach to inertial fusion energy. PMID:23683207

  12. Comparison of weak-shock reflection factors for wedges, cylinders and blast waves

    SciTech Connect

    Reichenbach, H.; Kuhl, A.L.

    1992-07-01

    Ernst Mach (1838--1916) was the first to discover an irregular reflection phenomenon of shock waves, as is well known in our community. In fact, this occurred in 1875 -- three years earlier than usually assumed in the literature. A facsimile of the paper in which he mentioned a special shock wave behavior is shown in a figure. However, it is correct that Mach gave the physical interpretation of this phenomenon in 1878. Since Mach`s discovery of an irregular shock reflection pattern 117 years ago, new shock configurations have been discovered -- one of the most recent examples is the so-called {open_quotes}von Neumann reflection{close_quotes} for weak shocks as reported by Colella and Henderson in 1990. Due to active research efforts related to shock reflection, especially in the last two decades, we now have a relatively detailed understanding of reflection phenomena and of transition conditions from one reflection configuration to another. The purpose of this paper is to compare reflection factors for weak shocks from various surfaces, and to focus attention on some unsolved questions. Three different cases are considered: (1) square-wave planar shock reflection from wedges, (2) square-wave planar shock reflection from cylinders and (3) spherical blast wave reflection from a planar surface. The authors restrict themselves to weak shocks. Following Henderson`s definition, shocks with a Mach number of M{sub 0} < 1.56 in air or with an overpressure of {Delta}p{sub I} < 25 psi (1.66 bar) under normal ambient conditions are called weak.

  13. Comparison of weak-shock reflection factors for wedges, cylinders and blast waves

    SciTech Connect

    Reichenbach, H. , Freiburg im Breisgau ); Kuhl, A.L. )

    1992-07-01

    Ernst Mach (1838--1916) was the first to discover an irregular reflection phenomenon of shock waves, as is well known in our community. In fact, this occurred in 1875 -- three years earlier than usually assumed in the literature. A facsimile of the paper in which he mentioned a special shock wave behavior is shown in a figure. However, it is correct that Mach gave the physical interpretation of this phenomenon in 1878. Since Mach's discovery of an irregular shock reflection pattern 117 years ago, new shock configurations have been discovered -- one of the most recent examples is the so-called [open quotes]von Neumann reflection[close quotes] for weak shocks as reported by Colella and Henderson in 1990. Due to active research efforts related to shock reflection, especially in the last two decades, we now have a relatively detailed understanding of reflection phenomena and of transition conditions from one reflection configuration to another. The purpose of this paper is to compare reflection factors for weak shocks from various surfaces, and to focus attention on some unsolved questions. Three different cases are considered: (1) square-wave planar shock reflection from wedges, (2) square-wave planar shock reflection from cylinders and (3) spherical blast wave reflection from a planar surface. The authors restrict themselves to weak shocks. Following Henderson's definition, shocks with a Mach number of M[sub 0] < 1.56 in air or with an overpressure of [Delta]p[sub I] < 25 psi (1.66 bar) under normal ambient conditions are called weak.

  14. Time-resolved spectroscopic measurements behind incident and reflected shock waves in air and xenon

    NASA Technical Reports Server (NTRS)

    Yoshinaga, T.

    1973-01-01

    Time-resolved spectra have been obtained behind incident and reflected shock waves in air and xenon at initial pressures of 0.1 and 1.0 torr using a rotating drum spectrograph and the OSU (The Ohio State University) arc-driven shock tube. These spectra were used to determine the qualitative nature of the flow as well as for making estimates of the available test time. The (n+1,n) and (n,n) band spectra of N2(+) (1st negative) were observed in the test gas behind incident shock waves in air at p1=1.0 torr and Us=9-10 km/sec. Behind reflected shock waves in air, the continuum of spectra appeared to cover almost the entire wavelength of 2,500-7,000 A for the shock-heated test gas. For xenon, the spectra for the incident shock wave cases for p1=0.1 torr show an interesting structure in which two intensely bright regions are witnessed in the time direction. The spectra obtained behind reflected shock waves in xenon were also dominated by continuum radiation but included strong absorption spectra due to FeI and FeII from the moment the reflected shock passed and on.

  15. Numerical and Experimental Investigation of Oblique Shock Wave Reflection from a Water Wedge

    NASA Astrophysics Data System (ADS)

    Wan, Qian; Jeon, Hongjoo; Eliasson, Veronica

    2015-11-01

    Shock wave interaction with solid wedges at different inclination angles has been an area of much research studied in the past, but not many results have been obtained for shock wave reflection from liquid wedges. To find the transition angle from regular to irregular reflection of shock wave reflection over liquid wedges - both Newtonian and non-Newtonian liquids - we used a combination of experimental and numerical methods. In experiments, an inclined shock tube with adjustable inclination angle and a test section filled with the liquid of interest was used. Simulations were performed using a collection of CFD and CSD solvers to simulate the same situation as in the experiments. Results show that the transition angles for liquid wedges is different from smooth solid wedges, but agree fairly well if one assumes a certain surface roughness of the solid wedge.

  16. Numerical solutions of several reflected shock-wave flow fields with nonequilibrium chemical reactions

    NASA Technical Reports Server (NTRS)

    Hanson, R. K.; Presley, L. L.; Williams, E. V.

    1972-01-01

    The method of characteristics for a chemically reacting gas is used in the construction of the time-dependent, one-dimensional flow field resulting from the normal reflection of an incident shock wave at the end wall of a shock tube. Nonequilibrium chemical reactions are allowed behind both the incident and reflected shock waves. All the solutions are evaluated for oxygen, but the results are generally representative of any inviscid, nonconducting, and nonradiating diatomic gas. The solutions clearly show that: (1) both the incident- and reflected-shock chemical relaxation times are important in governing the time to attain steady state thermodynamic properties; and (2) adjacent to the end wall, an excess-entropy layer develops wherein the steady state values of all the thermodynamic variables except pressure differ significantly from their corresponding Rankine-Hugoniot equilibrium values.

  17. Optical measurements of the mutual reflection of two-plane shock waves

    SciTech Connect

    Barbosa, F.J.; Skews, B.W.

    1995-12-31

    A bifurcated shock tube is used to create two synchronized waves of equal strength. Essentially a single shock wave is split symmetrically in two, the two waves then are later brought back together at a trailing edge of a wedge to interact, the plane of symmetry acting as an ideal rigid wall. The normal method of studying mach reflections is to allow a plane shock wave to impinge on a wedge, however the boundary layer growth on the wedge surface effectively ensures that the flow direction behind the Mach stem does not have to satisfy the boundary condition of being parallel to the surface of the wedge. Thus the transition from regular to Mach reflection occurs at higher angles of incidence than theory allows. The present experiment was initiated to generate data on the ideal cause of reflection off a plane wall. The advantage of the new system is that like classical theory and computational solutions of the inviscid Euler equations, the boundary layer no slip condition is not imposed at the plane of reflection. Optical methods are used to investigate the post-shock flow, as well as to help explain the complex interactions which occur when the two shock waves are not synchronized. These interactions show many very interesting features and clearly indicate the need for higher resolution measurements such as are obtained using holographic interferometry, and also to extend the work to different wedge angles and Mach numbers.

  18. Weak-shock reflection factors

    SciTech Connect

    Reichenbach, H.; Kuhl, A.L.

    1993-09-07

    The purpose of this paper is to compare reflection factors for weak shocks from various surfaces, and to focus attention on some unsolved questions. Three different cases are considered: square-wave planar shock reflection from wedges; square-wave planar shock reflection from cylinders; and spherical blast wave reflection from a planar surface. We restrict ourselves to weak shocks. Shocks with a Mach number of M{sub O} < 1.56 in air or with an overpressure of {Delta}{sub PI} < 25 psi (1.66 bar) under normal ambient conditions are called weak.

  19. Computer simulation of irregular surface reflection of an underwater shock wave

    SciTech Connect

    Kamegai, Minqo

    1986-09-01

    Computational studies are given for the behavior of a fluid set in motion by a shallow underwater nuclear explosion. Of particular interest is the interaction of the incident shock wave with the reflected rarefaction wave. Under certain conditions, the rarefaction wave can overtake the shock front beneath the water surface in a manner that is analogous to Mach stem formation in shock reflection from a rigid wall. This phenomenon, referred to as irregular surface rarefaction, has important implications in naval tactics, because it can limit the effective range of shallow underwater explosions. The boundary of the region where irregular rarefaction has occurred is determined by a rarefaction fan generated at the point of surface interaction. This fan resembles the Prandtl-Meyer fan for a supersonic flow through a rapidly expanding jet nozzle. A Lagrangian code and the ALE code were applied to simulate explosions of 10/sup 15/ joules at depths of burst of 3 m, 21 m, and 6.5 m, and to compute the underwater shock wave until the peak pressure decays to less than 0.1 GPa. The results show that the portion of the wave unperturbed by rarefaction closely follows Snay's theoretical description of a shock wave generated by a point explosion in infinite homogeneous water. The onset of the irregular surface rarefaction and the envelope which separates the irregular rarefaction region from the regular rarefaction one are calculated. The theoretical model that developed predicts quite well the onset point at the surface for all three cases plus the region boundary for weak shocks. However, the theory does not match the region boundary with the computed results at large distances for strong shocks. 14 refs., 26 figs.

  20. Effects of trapped electrons on ion reflection in an oblique shock wave

    SciTech Connect

    Toida, Mieko; Inagaki, Junya

    2015-06-15

    A magnetosonic shock wave propagating obliquely to an external magnetic field can trap electrons and accelerate them to ultrarelativistic energies. The trapped electrons excite two-dimensional (2D) electromagnetic fluctuations with finite wavenumbers along the shock front. We study effects of the trapped electrons on ion motions through the 2D fluctuations. It is analytically shown that the fraction of ions reflected from the shock front is enhanced by the 2D fluctuations. This is confirmed by 2D (two space coordinates and three velocities) relativistic, electromagnetic particle simulations with full ion and electron dynamics and calculation of test ions in the electromagnetic fields averaged along the shock front. A comparison between 2D and one-dimensional electromagnetic particle simulations is also shown.

  1. Visual studies of characteristics of slip stream in Mach reflection of a shock wave

    NASA Astrophysics Data System (ADS)

    Matsuo, Kazuyasu; Aoki, Toshiyuki; Hirahara, Hiroyuki

    The slip stream in the Mach reflection of a shock wave is presently visualized by the shadowgraph method. The effect of Reynolds number on the transition from laminar to turbulent mixing layers is experimentally considered, together with the growth rate of a fully developed turbulent mixing layer with a large difference in component velocities. The visual transition length from laminar to turbulent mixing layers is noted to strongly depend on the velocity-difference parameter, whose increase leads to a decrease of the transition number based on the transition length, the velocity difference on both sides of the layer, and the kinematic viscosity of the high velocity side.

  2. A State-of-the-Knowledge Review on Pseudo-Steady Shock-Wave Reflections and their Transition Criteria

    NASA Astrophysics Data System (ADS)

    Ben-Dor, G.

    2006-07-01

    The distinguished philosopher Ernst Mach published the first known paper on the phenomenon of planar shock-wave reflections over straight wedges over 125 years ago in 1878. In his publication he presented two wave configurations that could result from this reflection process, a regular reflection (RR) and a configuration that was later named after him and called Mach reflection (MR) in the early 1940s. In 1945, Smith reported on an additional wave configuration, which had a reflected shock wave that was slightly different from that of the just-mentioned Mach reflection. Smith (OSRD Rep. 6271, Off. Sci. Res. Dev., 1945) did not ascribe any special importance to the wave configuration that he observed. The wave configuration that was observed and reported by Smith (OSRD Rep. 6271, Off. Sci. Res. Dev., 1945) was recognized as an independent one only about 5 years later when White (Tech. Rep. II-10, Princeton Univ. Dept. Phys., 1951) reported on the discovery of a new wave configuration that was named double-Mach reflections (DMR) because it had similar features to that of the Mach reflection wave configuration but all the features were doubled. For this reason the Mach reflection wave configuration has been re-named single-Mach reflection (SMR). (Until the late 1970s it was called simple-Mach reflection although nothing is simple about it.). The discovery of the double-Mach reflection revealed that the wave configuration that was first observed by Smith was an intermediate wave configuration between the SMR and the DMR wave configurations. For this reason it was named transitional-Mach reflection (TMR) (Until the early 1980s it was called complex-Mach reflection although it is not the most complex one.). Since the discovery of the DMR many investigations were aimed at elucidating the exact transition criteria between the above-mentioned four different wave configurations as well as some additional configurations and sub-configurations that were discovered later. In

  3. Analytical reconsideration of the von Neumann paradox in the reflection of a shock wave over a wedge

    NASA Astrophysics Data System (ADS)

    Vasilev, Eugene I.; Elperin, Tov; Ben-Dor, Gabi

    2008-04-01

    The reflection of weak shock waves has been reconsidered analytically using shock polars. Based on the boundary condition across the slipstream, the solutions of the three-shock theory (3ST) were classified as "standard-3ST solutions" and "nonstandard-3ST solutions." It was shown that there are two situations in the nonstandard case: A situation whereby the 3ST provides solutions of which at least one is physical and a situation when the 3ST provides a solution which is not physical, and hence a reflection having a three-shock confluence is not possible. In addition, it is shown that there are initial conditions for which the 3ST does not provide any solution. In these situations, a four-wave theory, which is also presented in this study, replaces the 3ST. It is shown that four different wave configurations can exist in the weak shock wave reflection domain, a Mach reflection, a von Neumann reflection, a ?R (this reflection is not named yet!), and a modified Guderley reflection (GR). Recall that the wave configuration that was hypothesized by Guderley ["Considerations of the structure of mixed subsonic-supersonic flow patterns," Air Materiel Command Technical Report No. F-TR-2168-ND, ATI No. 22780, GS-AAF-Wright Field No. 39, U.S. Wright-Patterson Air Force Base, Dayton, OH (October 1947); Theorie Schallnaher Strömungen (Springer-Verlag, Berlin, 1957)] and later termed Guderley reflection did not include a slipstream (see Fig. 7). Our numerical study revealed that the wave structure proposed by Guderley must be complemented by a slipstream (see Fig. 4) in order to be relevant for explaining the von Neumann paradox. Hereafter, for simplicity, this modified GR wave configuration will be also termed Guderley reflection. The domains and transition boundaries between these four types of reflection are elucidated.

  4. Shock wave reflection induced detonation (SWRID) under high pressure and temperature condition in closed cylinder

    NASA Astrophysics Data System (ADS)

    Wang, Z.; Qi, Y.; Liu, H.; Zhang, P.; He, X.; Wang, J.

    2016-07-01

    Super-knock is one of the major obstacles for improving power density in advanced internal combustion engines (ICE). This work studied the mechanism of super-knock initiation using a rapid compression machine that simulated conditions relevant to ICEs and provided excellent optical accessibility. Based on the high-speed images and pressure traces of the stoichiometric iso-octane/oxygen/nitrogen combustion under high-temperature and high-pressure conditions, it was observed that detonation was first initiated in the near-wall region as a result of shock wave reflection. Before detonation was initiated, the speed of the combustion wave front was less than that of the Chapman-Jouguet (C-J) detonation speed (around 1840 m/s). In the immediate vicinity of the initiation, the detonation speed was much higher than that of the C-J detonation.

  5. Hydrodynamics of shock waves with reflected particles. I. Rankine-Hugoniot relations and stationary solutions

    SciTech Connect

    Dasgupta, B.; Burrows, R.; Zank, G. P.; Webb, G. M.

    2006-08-15

    In this work we investigate how reflected particles modify the Rankine-Hugoniot (RH) relations in a simple hydrodynamical framework. It is assumed that the ions are specularly reflected by the cross-shock potential. For simplicity, an exactly perpendicular shock is assumed, thus other reflection mechanisms, such as magnetic mirroring, can be neglected. Momentum and energy terms are introduced to model reflected particles at the shock and the RH conditions are examined using a geometrical entropy condition to distinguish the physically relevant states. Although such shocks have some common features with combustion shocks within a narrow range of reflection parameters, for a wide range of reflection parameters, particularly for highly oblique shocks, Chapman-Jouguet solutions do not exist. It is conjectured that these shocks comprise a distinct class. Decelerated solutions of the RH conditions are shown to exist only under specific conditions for shocks with reflected particles. Velocity flows both parallel and oblique to the perpendicular shock (with respect to an upstream magnetic field) are considered and found to be strongly sheared.

  6. Diffraction of a shock wave by a compression corner; regular and single Mach reflection

    NASA Technical Reports Server (NTRS)

    Vijayashankar, V. S.; Kutler, P.; Anderson, D.

    1976-01-01

    The two dimensional, time dependent Euler equations which govern the flow field resulting from the injection of a planar shock with a compression corner are solved with initial conditions that result in either regular reflection or single Mach reflection of the incident planar shock. The Euler equations which are hyperbolic are transformed to include the self similarity of the problem. A normalization procedure is employed to align the reflected shock and the Mach stem as computational boundaries to implement the shock fitting procedure. A special floating fitting scheme is developed in conjunction with the method of characteristics to fit the slip surface. The reflected shock, the Mach stem, and the slip surface are all treated as harp discontinuities, thus, resulting in a more accurate description of the inviscid flow field. The resulting numerical solutions are compared with available experimental data and existing first-order, shock-capturing numerical solutions.

  7. Weak shock reflection

    NASA Astrophysics Data System (ADS)

    Hunter, John K.; Brio, Moysey

    2000-05-01

    We present numerical solutions of a two-dimensional inviscid Burgers equation which provides an asymptotic description of the Mach reflection of weak shocks. In our numerical solutions, the incident, reflected, and Mach shocks meet at a triple point, and there is a supersonic patch behind the triple point, as proposed by Guderley for steady weak-shock reflection. A theoretical analysis indicates that there is an expansion fan at the triple point, in addition to the three shocks. The supersonic patch is extremely small, and this work is the first time it has been resolved.

  8. Temperature measurements behind reflected shock waves in air. [radiometric measurement of gas temperature in self-absorbing gas flow

    NASA Technical Reports Server (NTRS)

    Bader, J. B.; Nerem, R. M.; Dann, J. B.; Culp, M. A.

    1972-01-01

    A radiometric method for the measurement of gas temperature in self-absorbing gases has been applied in the study of shock tube generated flows. This method involves making two absolute intensity measurements at identical wavelengths, but for two different pathlengths in the same gas sample. Experimental results are presented for reflected shock waves in air at conditions corresponding to incident shock velocities from 7 to 10 km/s and an initial driven tube pressure of 1 torr. These results indicate that, with this technique, temperature measurements with an accuracy of + or - 5 percent can be carried out. The results also suggest certain facility related problems.

  9. Comparison between holographic interferometry and high-speed videography techniques in the study of the reflection of plane shock waves

    NASA Astrophysics Data System (ADS)

    Barbosa, Filipe J.; Skews, Beric W.

    1997-05-01

    Double exposure holographic interferometry and high speed laser shadowgraph photography and videography are used to investigate the mutual reflection of two plane shock waves. Normally research on the transition from regular to Mach reflection is undertaken by allowing a plane shock wave to impinge on a wedge. However due to the boundary layer growth on the wedge, regular reflection persists at wedge angles higher than that allowed for by inviscid shock wave theory. Several bifurcated shock tubes have been constructed, wherein an initially planar shock wave is split symmetrically into two and then recombined at the trailing edge of a wedge. The plane of symmetry acts as an ideal rigid wall eliminating thermal and viscous boundary layer effects. The flow visualization system used needs to provide high resolution information on the shockwave, slipstream, triple point and vortex positions and angles. Initially shadowgraph and schlieren methods, with a Xenon light source, were used. These results, while proving useful, are not of a sufficient resolution to measure the Mach stem and slipstream lengths accurately enough in order to determine the transition point between regular and Mach reflection. To obtain the required image resolution a 2 joule double pulse ruby laser, with a 30 ns pulse duration, was used to make holographic interferograms. The combined advantages of holographic interferometry and the 30 ns pulse laser allows one to obtain much sharper definition, and more qualitative as well as quantitative information on the flow field. The disadvantages of this system are: the long time taken to develop holograms, the difficulty of aligning the pulse laser and the fact that only one image per test is obtained. Direct contact shadowgraphs were also obtained using the pulse ruby laser to help determine triple point trajectory angles. In order to provide further information a one million frames per second CCD camera, which can take up to 10 superimposed images, was

  10. Interstellar shock waves

    NASA Technical Reports Server (NTRS)

    Mckee, C. F.; Hollenbach, D. J.

    1980-01-01

    The structure of interstellar shocks driven by supernova remnants and by expanding H II regions around early-type stars is discussed. Jump conditions are examined, along with shock fronts, post-shock relaxation layers, collisional shocks, collisionless shocks, nonradiative shocks, radiative atomic shocks, and shock models of observed nebulae. Effects of shock waves on interstellar molecules are examined, with reference to the chemistry behind shock fronts, infrared and vibrational-rotational cooling by molecules, and observations of shocked molecules. Some current problems and applications of the study of interstellar shocks are summarized, including the initiation of star formation by radiative shock waves, interstellar masers, the stability of shocks, particle acceleration in shocks, and shocks in galactic nuclei.

  11. Planar Reflection of Detonations Waves

    NASA Astrophysics Data System (ADS)

    Damazo, Jason; Shepherd, Joseph

    2012-11-01

    An experimental study examining normally reflected gaseous detonation waves is undertaken so that the physics of reflected detonations may be understood. Focused schlieren visualization is used to describe the boundary layer development behind the incident detonation wave and the nature of the reflected shock wave. Reflected shock wave bifurcation-which has received extensive study as it pertains to shock tube performance-is predicted by classical bifurcation theory, but is not observed in the present study for undiluted hydrogen-oxygen and ethylene-oxygen detonation waves. Pressure and thermocouple gauges are installed in the floor of the detonation tube so as to examine both the wall pressure and heat flux. From the pressure results, we observe an inconsistency between the measured reflected shock speed and the measured reflected shock strength with one dimensional flow predictions confirming earlier experiments performed in our laboratory. This research is sponsored by the DHS through the University of Rhode Island, Center of Excellence for Explosives Detection.

  12. Computer simulation studies on free surface reflection of underwater shock waves

    SciTech Connect

    Kamegai, M.; Rosenkilde, C.E.; Klein, L.S.

    1987-07-01

    A computer simulation was used to study the irregular surface rarefaction phenomena produced by an underwater shock wave generated from a strong point explosion. We simulated the explosions with energies near 10/sup 15/ joules at three depths (3 m, 21 m, and 66.5 m) and computed the shock propagation until the peak pressure decayed to less than 0.1 GPa (1 Kbar). The simulations permitted the determination of the onset point of irregular rarefaction on the surface, and of the envelope separating the irregular and regular-rarefaction regions. The theoretical predictions of the onset points are consistent with the code results for all three cases. However, the predicted region boundaries, which are calculated from the arrival of the first rarefaction signal, are in agreement with the simulation results only in the weak shock case (DOB = 66.5 m). For the strong and intermediate shock cases (DOB = 3 m and 21 m, respectively), agreement was not obtained. The implication of the discrepancy in these cases is discussed. 9 refs., 8 figs.

  13. Flow control of an oblique shock wave reflection with micro-ramp vortex generators: Effects of location and size

    NASA Astrophysics Data System (ADS)

    Giepman, R. H. M.; Schrijer, F. F. J.; van Oudheusden, B. W.

    2014-06-01

    This study investigates the influences of micro-ramp size and location on its effectiveness as a flow control device for oblique shock wave reflections. The effectiveness is measured in terms of the size of the shock-induced separation bubble and the reflected shock unsteadiness. Particle image velocimetry measurements were carried out on the interaction region and the mixing region between micro-ramp and interaction. The separation bubble is shown to be most sensitive to the momentum flux contained in the lower 43% of the incoming boundary layer. The momentum flux added to this region scales linearly with micro-ramp height and larger micro-ramps are shown to be more effective in stabilizing the interaction. Full boundary layer mixing is attained 5.7δ downstream of the micro-ramp and this forms a lower limit on the required distance between micro-ramp and the start of the interaction region. Typical reductions in the average separated area and the shock unsteadiness of 87% and 51%, respectively, were recorded. Results, however, depend strongly upon the spanwise location, with the micro-ramp being most effective along its centerline.

  14. Shock wave interaction with turbulence: Pseudospectral simulations

    SciTech Connect

    Buckingham, A.C.

    1986-12-30

    Shock waves amplify pre-existing turbulence. Shock tube and shock wave boundary layer interaction experiments provide qualitative confirmation. However, shock pressure, temperature, and rapid transit complicate direct measurement. Computational simulations supplement the experimental data base and help isolate the mechanisms responsible. Simulations and experiments, particularly under reflected shock wave conditions, significantly influence material mixing. In these pseudospectral Navier-Stokes simulations the shock wave is treated as either a moving (tracked or fitted) domain boundary. The simulations assist development of code mix models. Shock Mach number and pre-existing turbulence intensity initially emerge as key parameters. 20 refs., 8 figs.

  15. Optical signal measurement of iso-octane autoignition behind reflected shock wave

    NASA Astrophysics Data System (ADS)

    Chen, Qisheng; Dou, Zhiguo; Li, Lan

    2015-03-01

    Ignition delay time of diluted iso-octane/Air mixtures were measured in a single pulse reflected shock tube. In this work, the onset of ignition was determined by monitoring both the pressure history and the emitted light corresponding to OH* emission. The photomultiplier tube (PMT) in specially designed housing at CaF2 window were used with 310±5nm filters to measure the ultraviolet OH* emission. Experiments were performed at temperatures between 1295K and 2487K, pressures about 1 atm. and varying equivalence ratios (Φ=0.25, 0.5, 1.0, 2.0). Long shock tube dwell time (about 15ms) was achieved by tailored contact surface operation under such conditions. To simulate real engine environment, liquid fuel aerosol was generated by the supersonic atomizer, and the size of fuel droplet in aerosol was measured. Both pressure and OH*emission histories were obtained to determine the ignition delay time and the relative strength of the ignition process. The OH* emission time history data showed that there were different behaviors of iso-octane in ignition process under varying temperatures. Several potential chemical kinetics mechanisms were used to simulated iso-octane autoignition under the same conditions. Analysis of the experiments results and simulations supported the validation of those chemical kinetics mechanisms. The experimental data was consistent with the prediction of mechanism in low temperatures and the experiment data showed that the factors of temperature and equivalent ratio have different effect on the ignition delay time

  16. Attosecond shock waves.

    PubMed

    Zhokhov, P A; Zheltikov, A M

    2013-05-01

    Shock-wave formation is a generic scenario of wave dynamics known in nonlinear acoustics, fluid dynamics, astrophysics, seismology, and detonation physics. Here, we show that, in nonlinear optics, remarkably short, attosecond shock transients can be generated through a strongly coupled spatial and temporal dynamics of ultrashort light pulses, suggesting a pulse self-compression scenario whereby multigigawatt attosecond optical waveforms can be synthesized. PMID:23683197

  17. When shock waves collide

    DOE PAGESBeta

    Martinez, D.; Hartigan, P.; Frank, A.; Hansen, E.; Yirak, K.; Liao, A. S.; Graham, P.; Foster, J.; Wilde, B.; Blue, B.; et al

    2016-06-01

    Supersonic outflows from objects as varied as stellar jets, massive stars, and novae often exhibit multiple shock waves that overlap one another. When the intersection angle between two shock waves exceeds a critical value, the system reconfigures its geometry to create a normal shock known as a Mach stem where the shocks meet. Mach stems are important for interpreting emission-line images of shocked gas because a normal shock produces higher postshock temperatures, and therefore a higher-excitation spectrum than does an oblique shock. In this paper, we summarize the results of a series of numerical simulations and laboratory experiments designed tomore » quantify how Mach stems behave in supersonic plasmas that are the norm in astrophysical flows. The experiments test analytical predictions for critical angles where Mach stems should form, and quantify how Mach stems grow and decay as intersection angles between the incident shock and a surface change. While small Mach stems are destroyed by surface irregularities and subcritical angles, larger ones persist in these situations and can regrow if the intersection angle changes to become more favorable. Furthermore, the experimental and numerical results show that although Mach stems occur only over a limited range of intersection angles and size scales, within these ranges they are relatively robust, and hence are a viable explanation for variable bright knots observed in Hubble Space Telescope images at the intersections of some bow shocks in stellar jets.« less

  18. When Shock Waves Collide

    NASA Astrophysics Data System (ADS)

    Hartigan, P.; Foster, J.; Frank, A.; Hansen, E.; Yirak, K.; Liao, A. S.; Graham, P.; Wilde, B.; Blue, B.; Martinez, D.; Rosen, P.; Farley, D.; Paguio, R.

    2016-06-01

    Supersonic outflows from objects as varied as stellar jets, massive stars, and novae often exhibit multiple shock waves that overlap one another. When the intersection angle between two shock waves exceeds a critical value, the system reconfigures its geometry to create a normal shock known as a Mach stem where the shocks meet. Mach stems are important for interpreting emission-line images of shocked gas because a normal shock produces higher postshock temperatures, and therefore a higher-excitation spectrum than does an oblique shock. In this paper, we summarize the results of a series of numerical simulations and laboratory experiments designed to quantify how Mach stems behave in supersonic plasmas that are the norm in astrophysical flows. The experiments test analytical predictions for critical angles where Mach stems should form, and quantify how Mach stems grow and decay as intersection angles between the incident shock and a surface change. While small Mach stems are destroyed by surface irregularities and subcritical angles, larger ones persist in these situations and can regrow if the intersection angle changes to become more favorable. The experimental and numerical results show that although Mach stems occur only over a limited range of intersection angles and size scales, within these ranges they are relatively robust, and hence are a viable explanation for variable bright knots observed in Hubble Space Telescope images at the intersections of some bow shocks in stellar jets.

  19. Kinetics of the Thermal Decomposition of Tetramethylsilane behind the Reflected Shock Waves in a Single Pulse Shock Tube (SPST) and Modeling Study

    NASA Astrophysics Data System (ADS)

    Parandaman, A.; Sudhakar, G.; Rajakumar, B.

    Thermal reactions of Tetramethylsilane (TMS) diluted in argon were studied behind the reflected shock waves in a single-pulse shock tube (SPST) over the temperature range of 1085-1221 K and pressures varied between 10.6 and 22.8 atm. The stable products resulting from the decomposition of TMS were identified and quantified using gas chromatography and also verified with Fourier Transform Infrared (FTIR) spectrometer. The major reaction products are methane (CH4) and ethylene (C2H4). The minor reaction products are ethane (C2H6) and propylene (C3H6). The initiation of mechanism in the decomposition of TMS takes plays via the Si-C bond scission by ejecting the methyl radicals (CH3) and trimethylsilyl radicals ((CH3)3Si). The measured temperature dependent rate coefficient for the total decomposition of TMS was to be ktotal = 1.66 ×1015 exp (-64.46/RT) s-1 and for the formation of CH4 reaction channel was to be k = 2.20 × 1014 exp (-60.15/RT) s-1, where the activation energies are given in kcal mol-1. A kinetic scheme containing 17 species and 28 elementary reactions was used for the simulation using chemical kinetic simulator over the temperature range of 1085-1221 K. The agreement between the experimental and simulated results was satisfactory.

  20. Dissociation of 1,1,1-trifluoroethane behind reflected shock waves :shock tube/time-of-flight mass spectrometry experiments.

    SciTech Connect

    Giri, B. R.; Tranter, R. S.; Chemistry

    2007-01-01

    The dissociation of 1,1,1,-trifluoroethane, a potential non-RRKM reaction, has been studied at 600 and 1200 Torr and high temperatures (1500-1840 K) using a new shock tube/time-of-flight mass spectrometer (ST/TOF-MS). These data obtained by an independent method are in good agreement with the laser schlieren, LS, experiments of Kiefer et al. [J. Phys. Chem. A 2004, 108, 2443-2450] and extend the range of that experimental dataset. The data have been simulated by both standard RRKM calculations and the non-RRKM model reported by Kiefer et al. but with <{Delta}E{sub down}> = 750 cm{sup -1}. Both the RRKM and non-RRKM calculations provide equally good fits to the ST/TOF-MS data. Neither model simulates the combined ST/TOF-MS and LS datasets particularly well. However, the non-RRKM model predicts a pressure dependency closer to that observed in the experiments than the RRKM model.

  1. TIMING OF SHOCK WAVES

    DOEpatents

    Tuck, J.L.

    1955-03-01

    This patent relates to means for ascertaining the instant of arrival of a shock wave in an exploslve charge and apparatus utilizing this means to coordinate the timing of two operations involving a short lnterval of time. A pair of spaced electrodes are inserted along the line of an explosive train with a voltage applied there-across which is insufficient to cause discharge. When it is desired to initiate operation of a device at the time the explosive shock wave reaches a particular point on the explosive line, the device having an inherent time delay, the electrodes are located ahead of the point such that the ionization of the area between the electrodes caused by the traveling explosive shock wave sends a signal to initiate operation of the device to cause it to operate at the proper time. The operated device may be photographic equipment consisting of an x-ray illuminating tube.

  2. Methane oxidation behind reflected shock waves: Ignition delay times measured by pressure and flame band emission

    NASA Technical Reports Server (NTRS)

    Brabbs, T. A.; Robertson, T. F.

    1986-01-01

    Ignition delay data were recorded for three methane-oxygen-argon mixtures (phi = 0.5, 1.0, 2.0) for the temperature range 1500 to 1920 K. Quiet pressure trances enabled us to obtain delay times for the start of the experimental pressure rise. These times were in good agreement with those obtained from the flame band emission at 3700 A. The data correlated well with the oxygen and methane dependence of Lifshitz, but showed a much stronger temperature dependence (phi = 0.5 delta E = 51.9, phi = 1.0 delta = 58.8, phi = 2.0 delta E = 58.7 Kcal). The effect of probe location on the delay time measurement was studied. It appears that the probe located 83 mm from the reflecting surface measured delay times which may not be related to the initial temperature and pressure. It was estimated that for a probe located 7 mm from the reflecting surface, the measured delay time would be about 10 microseconds too short, and it was suggested that delay times less than 100 microsecond should not be used. The ignition period was defined as the time interval between start of the experimental pressure rise and 50 percent of the ignition pressure. This time interval was measured for three gas mixtures and found to be similar (40 to 60 micro sec) for phi = 1.0 and 0.5 but much longer (100 to 120) microsecond for phi = 2.0. It was suggested that the ignition period would be very useful to the kinetic modeler in judging the agreement between experimental and calculated delay times.

  3. Theoretical study of the self-similar traits, hysteresis phenomenon, and stability of reflected shock waves associated with inlet flow patterns

    NASA Astrophysics Data System (ADS)

    Smolinski, Gregory J.

    Of interest to the analytical study of Mach stem heights is the shock patterns that form in a simple inlet flow. A simple inlet flow is defined as a flow in which the inlet height is of such a size such that the incident wave does not interact with the expansion fan, and that the inlet wedge face is small enough that a reflected shock does not impinge upon it. The condition for which the incident wave intersects the leading edge of the expansion fan, and for the case where a reflected wave intersects the trailing edge of the inlet wedge were found in the form of a ratio between the inlet height and wedge face length. The various wave angle limits for both cases were also studied and presented. Once the limits for a simple inlet flow were defined, the problem of solving for Mach stem heights was studied. Quantitatively, past analytical studies were able to achieve moderate success at predicting stem heights for a very limited range of Mach numbers. Inherent to a quantitative study regarding Mach stems is the lack of a physical length scale. Therefore, the present study approached the problem of Mach Reflections in a qualitative way. The self-similar aspects of the Mach stem were revealed and a solution for Mach stems was found. The explicit dependence of the Mach stem on the freestream Mach number, wedge angle, and ratio of specific heats were noted. Additionally, the theoretical lower and upper limits of the Regular and Mach Reflection flowfields were studied. In addition to solving qualitatively for Mach stem heights, a study was done on the stability of the shock waves pertaining to the reflection patterns that form. In the region betaN ≤ beta ≤ beta D it is possible for either a Regular Reflection or a Mach Reflection to form for a given freestream Mach number. Of practical interest, besides the stability of the shock pattern, is the transition from a Regular Reflection to a Mach Reflection and vice versa. The transition between the two reflection patterns

  4. Shock wave control using liquid curtains

    NASA Astrophysics Data System (ADS)

    Colvert, Brendan; Tao, Xingtian; Eliasson, Veronica

    2014-11-01

    The effectiveness of a planar wall of liquid as a blast mitigation device is examined using a shock tube and a custom-designed and -built shock test chamber. Experimental data collection methods being used include high-speed schlieren photography and high-frequency pressure sensors. During the relevant shock interaction time periods, the liquid-gas interface is examined to determine its effect on shock waves. The characteristic quantities that reflect these effects include reflected-to-incident shock strength ratio, transmitted-to-incident shock strength ratio, transmitted and reflected impulse, and peak pressure reduction. These parameters are examined for correlations to incident wave speed, liquid mass, liquid density, and liquid viscosity. Initial results have been obtained that show a correlation between fluid mass and peak pressure reduction. More experiments are being performed to further explore this relationship as well as examine the effects of altering the other parameters such as liquid-gas interface geometry and using dilatant fluids.

  5. A midsummer-night's shock wave

    NASA Astrophysics Data System (ADS)

    Hargather, Michael; Liebner, Thomas; Settles, Gary

    2007-11-01

    The aerial pyrotechnic shells used in professional display fireworks explode a bursting charge at altitude in order to disperse the ``stars'' of the display. The shock wave from the bursting charge is heard on the ground as a loud report, though it has by then typically decayed to a mere sound wave. However, viewers seated near the standard safety borders can still be subjected to weak shock waves. These have been visualized using a large, portable, retro-reflective ``Edgerton'' shadowgraph technique and a high-speed digital video camera. Images recorded at 10,000 frames per second show essentially-planar shock waves from 10- and 15-cm firework shells impinging on viewers during the 2007 Central Pennsylvania July 4th Festival. The shock speed is not measurably above Mach 1, but we nonetheless conclude that, if one can sense a shock-like overpressure, then the wave motion is strong enough to be observed by density-sensitive optics.

  6. Unsteady interaction of shock and detonation waves in gases

    NASA Astrophysics Data System (ADS)

    Korobeinikov, Viktor P.

    Recent theoretical and experimental investigations of unsteady shock-wave interactions (SWIs) in gases are discussed in chapters contributed by leading Soviet experts. Topics addressed include the thermodynamic and electrophysical parameters of gas flow behind shock waves, the effect of nonequilibrium physicochemical processes on the flow parameters behind a shock wave, shock-tube investigations of unsteady SWI, SWI with a porous compressible medium, and the reflection of shock waves by a plane surface. Consideration is given to the diffraction of a shock wave at a convex corner, unsteady SWIs with curvilinear surfaces, numerical simulations of SWIs with bodies of various shapes, and the unsteady interaction of detonation waves. Diagrams, graphs, and photographs.

  7. The carbon dioxide chaperon efficiency for the reaction H + O2 + M yields HO2 + M from ignition delay times behind reflected shock waves

    NASA Technical Reports Server (NTRS)

    Brabbs, Theodore A.; Robertson, Thomas F.

    1987-01-01

    Ignition delay times for stoichiometric hydrogen-oxygen in argon with and without carbon dioxide were measured behind reflected shock waves. A 20-reaction kinetic mechanism models the measured hydrogen-oxygen delay times over the temperature range 950 to 1300 K. The chaperon efficiency for carbon dioxide determined for the hydrogen-oxygen carbon dioxide mixture was 7.0. This value is in agreement with literature values but much less than a recent value obtained from flow tube experiments. Delay times measured behind a reflected shock wave were about 20% longer than those measured behind incident shock waves. The kinetic mechanism successfully modeled the high-pressure data of Skinner and the hydrogen-air data of Stack. It is suggested that the lowest temperature points for the hydrogen-air data of Slack are unreliable and that the 0.27-atm data may illustrate a case where vibrational relaxation of nitrogen is important. The reaction pathway HO2 yields H2O2 yields OH yields H was required to model the high-pressure data of Skinner. The successful modeling of the stoichiometric hydrogen-air data demonstrates the appropriateness of deriving kinetic models from data for gas mixtures highly diluted with argon. The technique of reducing a detailed kinetic mechanism to only the important reactions for a limited range of experimental data may render the mechanism useless for other test conditions.

  8. Radiative Shock Waves In Emerging Shocks

    NASA Astrophysics Data System (ADS)

    Drake, R. Paul; Doss, F.; Visco, A.

    2011-05-01

    In laboratory experiments we produce radiative shock waves having dense, thin shells. These shocks are similar to shocks emerging from optically thick environments in astrophysics in that they are strongly radiative with optically thick shocked layers and optically thin or intermediate downstream layers through which radiation readily escapes. Examples include shocks breaking out of a Type II supernova (SN) and the radiative reverse shock during the early phases of the SN remnant produced by a red supergiant star. We produce these shocks by driving a low-Z plasma piston (Be) at > 100 km/s into Xe gas at 1.1 atm. pressure. The shocked Xe collapses to > 20 times its initial density. Measurements of structure by radiography and temperature by several methods confirm that the shock wave is strongly radiative. We observe small-scale perturbations in the post-shock layer, modulating the shock and material interfaces. We describe a variation of the Vishniac instability theory of decelerating shocks and an analysis of associated scaling relations to account for the growth of these perturbations, identify how they scale to astrophysical systems such as SN 1993J, and consider possible future experiments. Collaborators in this work have included H.F. Robey, J.P. Hughes, C.C. Kuranz, C.M. Huntington, S.H. Glenzer, T. Doeppner, D.H. Froula, M.J. Grosskopf, and D.C. Marion ________________________________ * Supported by the US DOE NNSA under the Predictive Sci. Academic Alliance Program by grant DE-FC52-08NA28616, the Stewardship Sci. Academic Alliances program by grant DE-FG52-04NA00064, and the Nat. Laser User Facility by grant DE-FG03-00SF22021.

  9. Shock waves data for minerals

    NASA Technical Reports Server (NTRS)

    Ahrens, Thomas J.; Johnson, Mary L.

    1994-01-01

    Shock compression of the materials of planetary interiors yields data which upon comparison with density-pressure and density-sound velocity profiles constrain internal composition and temperature. Other important applications of shock wave data and related properties are found in the impact mechanics of terrestrial planets and solid satellites. Shock wave equation of state, shock-induced dynamic yielding and phase transitions, and shock temperature are discussed. In regions where a substantial phase change in the material does not occur, the relationship between the particle velocity, U(sub p), and the shock velocity, U(sub s), is given by U(sub s) = C(sub 0) + S U(sub p), where C(sub 0) is the shock velocity at infinitesimally small particle velocity, or the ambient pressure bulk sound velocity. Numerical values for the shock wave equation of state for minerals and related materials of the solar system are provided.

  10. Shock-wave surfing

    SciTech Connect

    Laurence, Stuart J; Deiterding, Ralf

    2011-01-01

    A phenomenon referred to as shock-wave surfing , in which a body moves in such a way as to follow the shock wave generated by another upstream body, is investigated numerically and theoretically. This process can lead to the downstream body accumulating a significantly higher lateral velocity than would otherwise be possible, and thus is of importance in situations such as meteoroid fragmentation, in which the fragment separation behaviour following disruption is determined to a large extent by aerodynamic effects. The surfing effect is first investigated in the context of interactions between a sphere and a planar oblique shock. Numerical simulations are performed and a simple theoretical model is developed to determine the forces acting on the sphere. A phase-plane description is employed to elucidate features of the system dynamics. The theoretical model is then generalised to the more complex situation of aerodynamic interactions between two spheres, and, through comparisons with further computations, is shown to adequately predict, in particular, the final separation velocity of the surfing sphere in initially touching configurations. Both numerical simulations and theory indicate a strong influence of the body radius ratio on the separation process and predict a critical radius ratio for initially touching fragments that delineates entrainment of the smaller fragment within the larger fragment s shock from expulsion; this critical ratio also results in the most extended surfing. Further, these results show that an earlier prediction for the separation velocity to scale with the square root of the radius ratio does not accurately describe the separation behaviour. The theoretical model is then employed to investigate initial configurations with varying relative sphere positions and initial velocities. A phase-space description is also shown to be useful in elucidating the dynamics of the sphere-sphere system. With regard to meteoroid fragmentation, it is shown

  11. Shock transmission and reflection from a material interface and subsequent reflection from a hard boundary

    SciTech Connect

    Hurricane, O A; Miller, P L

    1998-11-20

    As a shock wave passes through a material interface into a region of higher density (the receiver material), a trans- mitted and reflected shock wave are both generated and the interface is set into motion. The speeds of the transmitted shock, reflected shock, and interface are related to the ini- tial shock speed and material properties via a set of coupled nonlinear equations that, in general, cannot be easily solved analytically. In this report, we derive the equations which describe this process and we document a numerical routine which solves the nonlinear equations. We then go on to solve the problem of finding the position where the interface col- lides with the transmitted shock wave once the transmitted shock wave is reflected from an impenetrable boundary lo- cated somewhere away from the initial material interface. Fi- nally, we compare the analytical predictions with the CALE simulation running in 1-D.

  12. Shock-tube experiments on the stability of regular reflection in the dual-solution domain

    NASA Astrophysics Data System (ADS)

    Kobayashi, S.; Adachi, T.

    2016-05-01

    Regular reflection (RR) and Mach reflection (MR) are theoretically both possible in the dual-solution domain of oblique shock reflection. The physical difference between the two types of reflection is the pressure behind the reflected shock wave: that of MR is lower than that of RR for strong shock reflection. The magnitude relation of these pressures is inverted for weak shock reflection. In the present paper, we performed two kinds of experiment, depending on whether the oblique shock reflection is weak or strong. For strong shock reflection, we decreased the pressure behind the reflected wave of RR using a convex double-wedge. For weak shock reflection, we increased this pressure using a concave double-wedge. Thus, we investigated the stability of RR against pressure disturbances. The results indicate that RR in a shock tube is stable, in the dual-solution domain, for both weak and strong incident shocks.

  13. Ignition of mixtures of SiH sub 4, CH sub 4, O sub 2, and Ar or N sub 2 behind reflected shock waves

    NASA Technical Reports Server (NTRS)

    Mclain, A. G.; Jachimowski, C. J.; Rogers, R. C.

    1985-01-01

    Ignition delay times in mixtures of methane, silane, and oxygen diluted with argon and nitrogen were measured behind reflected shock waves generated in the chemical kinetic shock tube at Langley Research Center. The delay times were inferred from the rapid increase in pressure that occurs at ignition, and the ignition of methane was verified from the emission of infrared radiation from carbon dioxide. Pressures of 1.25 atm and temperatures from 1100 K to 1300 K were generated behind the reflected shocks; these levels are representative of those occurring within a supersonic Ramjet combustor. Expressions for the ignition delay time as a function of temperature were obtained from least squares curve fits to the data for overall equivalence ratios of 0.7 and 1.0. The ignition delay times with argon as the diluent were longer than those with nitrogen as the diluent. The infrared wavelength observations at 4.38 microns for carbon dioxide indicated that silane and methane ignited simultaneously (i.e., within the time resolution of the measurement). A combined chemical kinetic mechanism for mixtures of silane, methane, oxygen, and argon or nitrogen was assembled from one mechanism that accurately predicted the ignition of methane and a second mechanism that accurately predicted silane hydrogen ignition. Comparisons between this combined mechanism and experiment indicated that additional reactions, possibly between silyl and methyl fragments, are needed to develop a good silane methane mechanism.

  14. Current topics in shock waves; Proceedings of the International Symposium on Shock Waves and Shock Tubes, 17th, Lehigh University, Bethlehem, PA, July 17-21, 1989

    SciTech Connect

    Kim, Y.W.

    1990-01-01

    Various papers on shock waves are presented. The general topics addressed include: shock formation, focusing, and implosion; shock reflection and diffraction; turbulence; laser-produced plasmas and waves; ionization and shock-plasma interaction; chemical kinetics, pyrolysis, and soot formation; experimental facilities, techniques, and applications; ignition of detonation and combustion; particle entrainment and shock propagation through particle suspension; boundary layers and blast simulation; computational methods and numerical simulation.

  15. Some aspects of shock-wave research

    NASA Astrophysics Data System (ADS)

    Glass, I. I.

    1986-01-01

    The major portion of the paper is devoted to a specific shock-wave research problem, namely, pseudostationary oblique shock-wave reflections in perfect and imperfect gases. Consideration is given to what has been achieved to date by using two- and three-shock theory to predict what type of reflection results when a planar shock wave M(S), in a shock tube, collides with a sharp compressive wedge of angle, theta(W). Expermental (interferometric and other optical) data are presented in (M(S), theta(W))-plots for argon, nitrogen, oxygen, air, carbon-dioxide, Freon-12 and sulfurhexafluoride, in order to check the validity of the analytically predicted regions and transition lines of the four types of reflection. Some disagreements are noted and discussed. The present interferometric isopycnic data are also compared with state-of-the-art computational results from a solution of the inviscid Euler equations using a CRAY I computer. Good agreement was obtained; it would be important, however, to obtain new data by solving the Navier-Stokes equations, as well as the rate equations for imperfect-gas excitations, in order to judge the improvement obtained with real-flow interferograms.

  16. Damage mechanisms in shock wave lithotripsy (SWL)

    NASA Astrophysics Data System (ADS)

    Lokhandwalla, Murtuza

    Shock wave lithotripsy is a 'non-invasive' therapy for treating kidney stones. Focused shock waves fragment stones to a size that can be passed naturally. There is, however, considerable tissue injury, and the mechanisms of stone fragmentation and tissue injury are not well understood. This work investigates potential tissue damage mechanisms, with an aim towards enhancing stone fragmentation and minimizing tissue damage. Lysis of red blood cells (RBC's) due to in vitro exposure to shock waves was investigated. Fluid flow-fields induced by a non-uniform shock wave, as well as radial expansion/implosion of a bubble was hypothesized to cause cell lysis. Both the above flow-fields constitute an unsteady extensional flow, exerting inertial as well as viscous forces on the RBC membrane. The resultant membrane tension and the membrane areal strain due to the above flow-fields were estimated. Both were found to exert a significantly higher inertial force (50--100 mN/m) than the critical membrane tension (10 mN/m). Bubble-induced flow-field was estimated to last for a longer duration (˜1 microsec) compared to the shock-induced flow (˜1 ns) and hence, was predicted to be lytically more effective, in typical in vitro experimental conditions. However, in vivo conditions severely constrain bubble growth, and cell lysis due to shock-induced shear could be dominant. Hemolysis due to shock-induced shear, in absence of cavitation, was experimentally investigated. The lithotripter-generated shock wave was refocused by a parabolic reflector. This refocused wave-field had a tighter focus (smaller beam-width and a higher amplitude) than the lithotripter wave-field. Cavitation was eliminated by applying overpressure to the fluid. Acoustic emissions due to bubble activity were monitored by a novel passive cavitation detector (HP-PCD). Aluminum foils were also used to differentiate cavitational from non-cavitational mode of damage. RBC's were exposed to the reflected wave-field from

  17. Underwater Shock Wave Research Applied to Therapeutic Device Developments

    NASA Astrophysics Data System (ADS)

    Takayama, K.; Yamamoto, H.; Shimokawa, H.

    2013-07-01

    The chronological development of underwater shock wave research performed at the Shock Wave Research Center of the Institute of Fluid Science at the Tohoku University is presented. Firstly, the generation of planar underwater shock waves in shock tubes and their visualization by using the conventional shadowgraph and schlieren methods are described. Secondly, the generation of spherical underwater shock waves by exploding lead azide pellets weighing from several tens of micrograms to 100 mg, that were ignited by irradiating with a Q-switched laser beam, and their visualization by using double exposure holographic interferometry are presented. The initiation, propagation, reflection, focusing of underwater shock waves, and their interaction with various interfaces, in particular, with air bubbles, are visualized quantitatively. Based on such a fundamental underwater shock wave research, collaboration with the School of Medicine at the Tohoku University was started for developing a shock wave assisted therapeutic device, which was named an extracorporeal shock wave lithotripter (ESWL). Miniature shock waves created by irradiation with Q-switched HO:YAG laser beams are studied, as applied to damaged dysfunctional nerve cells in the myocardium in a precisely controlled manner, and are effectively used to design a catheter for treating arrhythmia.

  18. Shock wave interactions between slender bodies - Some aspects of three-dimensional shock wave diffraction

    NASA Astrophysics Data System (ADS)

    Hooseria, S. J.; Skews, B. W.

    2016-04-01

    A complex interference flowfield consisting of multiple shocks and expansion waves is produced when high-speed slender bodies are placed in close proximity. The disturbances originating from a generator body impinge onto the adjacent receiver body, modifying the local flow conditions over the receiver. This paper aims to uncover the basic gas dynamics produced by two closely spaced slender bodies in a supersonic freestream. Experiments and numerical simulations were used to interpret the flowfield, where good agreement between the predictions and measurements was observed. The numerical data were then used to characterise the attenuation associated with shock wave diffraction, which was found to be interdependent with the bow shock contact perimeter over the receiver bodies. Shock-induced boundary layer separation was observed over the conical and hemispherical receiver bodies. These strong viscous-shock interactions result in double-reflected, as well as double-diffracted shock wave geometries in the interference region, and the diffracting waves progress over the conical and hemispherical receivers' surfaces in "lambda" type configurations. This gives evidence that viscous effects can have a substantial influence on the local bow shock structure surrounding high-speed slender bodies in close proximity.

  19. Shock wave structure in heterogeneous reactive media

    SciTech Connect

    Baer, M.R.

    1997-06-01

    Continuum mixture theory and mesoscale modeling are applied to describe the behavior of shock-loaded heterogeneous media. One-dimensional simulations of gas-gun experiments demonstrate that the wave features are well described by mixture theory, including reflected wave behavior and conditions where significant reaction is initiated. Detailed wave fields are resolved in numerical simulations of impact on a lattice of discrete explosive {open_quotes}crystals{close_quotes}. It is shown that rapid distortion first occurs at material contact points; the nature of the dispersive fields includes large amplitude fluctuations of stress over several particle pathlengths. Localization of energy causes {open_quotes}hot-spots{close_quotes} due to shock focusing and plastic work as material flows into interstitial regions.

  20. Rayleigh-Taylor Shock Waves

    SciTech Connect

    Olson, B J; Cook, A W

    2007-08-30

    Beginning from a state of hydrostatic equilibrium, in which a heavy gas rests atop a light gas in a constant gravitational field, Rayleigh-Taylor instability at the interface will launch a shock wave into the upper fluid. The rising bubbles of lighter fluid act like pistons, compressing the heavier fluid ahead of the fronts and generating shocklets. These shocklets coalesce in multidimensional fashion into a strong normal shock, which increases in strength as it propagates upwards. Large-eddy simulations demonstrate that the shock Mach number increases faster in three dimensions than it does in two dimensions. The generation of shocks via Rayleigh-Taylor instability could have profound implications for astrophysical flows.

  1. Dual Mode Shock-Expansion/Reflected-Shock Tunnel

    NASA Technical Reports Server (NTRS)

    Erdos, John I.; Bakos, Robert J.; Castrogiovanni, Anthony; Rogers, R. Clayton

    1998-01-01

    NASA s HYPULSE facility at GASL has been reconfigured to permit free jet testing of the Hyper-X flowpath at flight Mach numbers of 7 and 10. Among the required changes are addition of a converging-diverging nozzle to permit operation in a reflected shock tunnel mode, a 7 ft. diameter test cabin and a 30 in. diameter contoured nozzle. However, none of these changes were allowed to interfere with rapid recovery of the prior shock-expansion tunnel mode of operation, and indeed certain changes should enhance facility usefulness and productivity in either mode. A previously-developed shock-induced detonation mode of driving the facility has been successfully applied to both reflected shock tunnel operation at Mach 10 flight conditions, with tailored interface operation, and shock-expansion tunnel operation at flight conditions corresponding to Mach numbers from 12 to 25. Tailored interface operation at Mach 7 has been achieved with an unheated helium driver. In the present paper, the rationale for a dual mode shock expansion/reflected shock tunnel is discussed, and the capabilities and limitations for each mode are outlined. The physical changes in the HYPULSE facility to achieve dual mode capability are also described. Limited calibration data obtained to date in the new reflected shock tunnel mode are presented and the anticipated flight simulation map with dual mode operation is also outlined.

  2. Review of methods to attenuate shock/blast waves

    NASA Astrophysics Data System (ADS)

    Igra, O.; Falcovitz, J.; Houas, L.; Jourdan, G.

    2013-04-01

    Quick and reliable shock wave attenuation is the goal of every protection facility and therefore it is not surprising that achieving this has drawn much attention during the past hundred years. Different options have been suggested; their usefulness varying from a reasonable protection to the opposite, a shock enhancement. An example for a suggestion for shock mitigation that turned out to be an enhancement of the impinging shock wave was the idea to cover a protected object with a foam layer. While the pressure behind the reflected shock wave from the foam frontal surface was smaller than that recorded in a similar reflection from a rigid wall [25], the pressure on the “protected” surface, attached to the foam's rear-surface, was significantly higher than that recorded in a similar reflection from a bare, rigid wall [11]. In protecting humans and installations from destructive shock and/or blast waves the prime goal is to reduce the wave amplitude and the rate of pressure increase across the wave front. Both measures result in reducing the wave harmful effects. During the past six decades several approaches for achieving the desired protection have been offered in the open literature. We point out in this review that while some of the suggestions offered are practical, others are impractical. In our discussion we focus on recent schemes for shock/blast wave attenuation, characterized by the availability of reliable measurements (notably pressure and optical diagnostics) as well as high-resolution numerical simulations.

  3. Model for shock wave chaos.

    PubMed

    Kasimov, Aslan R; Faria, Luiz M; Rosales, Rodolfo R

    2013-03-01

    We propose the following model equation, u(t) + 1/2(u(2)-uu(s))x = f(x,u(s)) that predicts chaotic shock waves, similar to those in detonations in chemically reacting mixtures. The equation is given on the half line, x<0, and the shock is located at x = 0 for any t ≥ 0. Here, u(s)(t) is the shock state and the source term f is taken to mimic the chemical energy release in detonations. This equation retains the essential physics needed to reproduce many properties of detonations in gaseous reactive mixtures: steady traveling wave solutions, instability of such solutions, and the onset of chaos. Our model is the first (to our knowledge) to describe chaos in shock waves by a scalar first-order partial differential equation. The chaos arises in the equation thanks to an interplay between the nonlinearity of the inviscid Burgers equation and a novel forcing term that is nonlocal in nature and has deep physical roots in reactive Euler equations. PMID:23521260

  4. Augmented shock wave fracture/severance of materials

    NASA Technical Reports Server (NTRS)

    Schimmel, Morry L. (Inventor); Bement, Laurence J. (Inventor)

    1995-01-01

    The present invention related generally to severing materials, and more particularly to severing or weakening materials through explosively induced, augmented shock waves. Explosive cords are placed in grooves on the upper surface of the material to be severed or weakened. The explosive cords are initiated simultaneously to introduce explosive shock waves into the material. These shock waves progress toward the centerline between the explosive cords and the lower surface of the material. Intersecting and reflected waves produce a rarefaction zone on the centerline to fail the material in tension. A groove may also be cut in the lower surface of the material to aid in severing or weakening the material.

  5. Multichannel fiber-based diffuse reflectance spectroscopy for the rat brain exposed to a laser-induced shock wave: comparison between ipsi- and contralateral hemispheres

    NASA Astrophysics Data System (ADS)

    Miyaki, Mai; Kawauchi, Satoko; Okuda, Wataru; Nawashiro, Hiroshi; Takemura, Toshiya; Sato, Shunichi; Nishidate, Izumi

    2015-03-01

    Due to considerable increase in the terrorism using explosive devices, blast-induced traumatic brain injury (bTBI) receives much attention worldwide. However, little is known about the pathology and mechanism of bTBI. In our previous study, we found that cortical spreading depolarization (CSD) occurred in the hemisphere exposed to a laser- induced shock wave (LISW), which was followed by long-lasting hypoxemia-oligemia. However, there is no information on the events occurred in the contralateral hemisphere. In this study, we performed multichannel fiber-based diffuse reflectance spectroscopy for the rat brain exposed to an LISW and compared the results for the ipsilateral and contralateral hemispheres. A pair of optical fibers was put on the both exposed right and left parietal bone; white light was delivered to the brain through source fibers and diffuse reflectance signals were collected with detection fibers for both hemispheres. An LISW was applied to the left (ipsilateral) hemisphere. By analyzing reflectance signals, we evaluated occurrence of CSD, blood volume and oxygen saturation for both hemispheres. In the ipsilateral hemispheres, we observed the occurrence of CSD and long-lasting hypoxemia-oligemia in all rats examined (n=8), as observed in our previous study. In the contralateral hemisphere, on the other hand, no occurrence of CSD was observed, but we observed oligemia in 7 of 8 rats and hypoxemia in 1 of 8 rats, suggesting a mechanism to cause hypoxemia or oligemia or both that is (are) not directly associated with CSD in the contralateral hemisphere.

  6. Interaction of a converging spherical shock wave with isotropic turbulence

    NASA Astrophysics Data System (ADS)

    Bhagatwala, Ankit; Lele, Sanjiva K.

    2012-08-01

    Simulations of converging spherical shock waves propagating through a region of compressible isotropic turbulence are carried out. Both converging and reflected phases of the shock are studied. Effect of the reflected phase of the shock is found to be quite different from the expanding shock in the Taylor blast wave-turbulence interaction problem. Vorticity and turbulent kinetic energy are amplified due to passage of the shock. Similar to the latter problem, the vorticity-dilatation term is primarily responsible for the observed behavior. This is confirmed through Eulerian and Lagrangian statistics. Transverse vorticity amplification is compared with linear planar shock-turbulence theory. The smallest eddies, represented by the Kolmogorov scale, decrease in size after passing through the converging shock and this is shown to be related to a decrease in kinematic viscosity and increase in dissipation behind the converging shock. Distortion of the shock due to turbulence is also investigated and quantified. Turbulence also affects maximum compression achieved at the point of shock reflection, when the shock radius is at a minimum. This decrease in compression is quantified by comparing with pure shock simulations.

  7. Corrugation of Relativistic Magnetized Shock Waves

    NASA Astrophysics Data System (ADS)

    Lemoine, Martin; Ramos, Oscar; Gremillet, Laurent

    2016-08-01

    As a shock front interacts with turbulence it develops corrugation, which induces outgoing wave modes in the downstream plasma. For a fast shock wave, the incoming wave modes can either be fast magnetosonic waves originating downstream, outrunning the shock, or eigenmodes of the upstream plasma drifting through the shock. Using linear perturbation theory in relativistic MHD, this paper provides a general analysis of the corrugation of relativistic magnetized fast shock waves resulting from their interaction with small amplitude disturbances. Transfer functions characterizing the linear response for each of the outgoing modes are calculated as a function of the magnetization of the upstream medium and as a function of the nature of the incoming wave. Interestingly, if the latter is an eigenmode of the upstream plasma, we find that there exists a resonance at which the (linear) response of the shock becomes large or even diverges. This result may have profound consequences on the phenomenology of astrophysical relativistic magnetized shock waves.

  8. Bow shock and magnetosheath waves at Mercury

    NASA Technical Reports Server (NTRS)

    Fairfield, D. H.; Behannon, K. W.

    1975-01-01

    Mariner 10 measurements at the Mercury bow shock provide examples where the magnetic field is approximately parallel or perpendicular to the bow shock normal. Upstream of a broad irregular parallel shock, left hand circularly polarized waves are observed which cut off very sharply at approximately 4 Hz. Upstream of a perpendicular shock, right hand circularly polarized waves are observed which persist up to the Nyquist frequency of 12 Ha. Determination of the wave propagation vector as a function of frequency helps conclusively identify the waves as whistler mode waves propagating from the shock. The magnetosheath downstream of the parallel shock is disturbed more than that downstream of the perpendicular shock particularly below 1 Hz. In the latter case regular left hand polarized waves observed slightly above the proton gyrofrequency are identified as ion cyclotron waves with wavelength approximately 300 km which are Doppler shifted up to their observed frequency.

  9. August Toepler — The first who visualized shock waves

    NASA Astrophysics Data System (ADS)

    Krehl, P.; Engemann, S.

    1995-06-01

    The scientific investigation of the nature of shock waves started 130 years ago with the advent of the schlieren method which was developed in the period 1859 1864 by August Toepler. At the very beginning applied to the visualization of heat and flow phenomena, he immediately turned to air shock waves generated by electric sparks, and subjectively studied the propagation, reflection and refraction of shock waves. His new delay circuit in the microsecond time regime for the first time made it possible to vary electrically the delay time between a spark generating a shock wave and a second spark acting as a flash light source in his chlieren setup. In 1870 Toepler, together with Boltzmann, applied Jamin's interferometric refractometer and extended the visualization to very weak sound waves at the threshold of hearing. Toepler's pioneering schlieren method stimulated Ernst Mach and his team to objectively investigate the nature of shock waves: they improved Toepler's time delay circuit; continued the study on the reflection of shock waves; introduced shadowgraphy as a modification of the schlieren method; photographed the propagation of shock waves generated by an electric spark and by supersonic projectiles, and improved interferometry. Based on a large number of original documents the paper illuminates the concomitant circumstances of the invention of the schlieren method and its first applications by others.

  10. Fiber Bragg Grating sensor for shock wave diagnostics

    NASA Astrophysics Data System (ADS)

    Ravid, Avi; Shafir, Ehud; Zilberman, Shlomi; Berkovic, Garry; Glam, Benny; Appelbaum, Gabriel

    2013-06-01

    Fiber Bragg Grating (FBG) sensor response was studied in gas-gun shock wave experiments. The sensors were embedded in PMMA target subjected to planar shock waves under 1 GPa. Two orientations of the FBG sensor with respect to the shock plane were examined: parallel and perpendicular. The shift of the reflected wavelength was measured with a system based on commonly available communication grade add-drop filters that covered the maximal expected wavelength swing. The FBG sensors survived the shock and their strain-to-wavelength response was determined by comparison to the calculated strain based on the known PMMA EOS and VISAR measurements.

  11. Oblique shock reflection from an axis of symmetry

    NASA Astrophysics Data System (ADS)

    Hornung, H. G.

    2000-04-01

    An exploratory computational study of the reflection of an inward-facing conical shock wave from its axis of symmetry is presented. This is related to more complex practical situations in both steady and unsteady flows. The absence of a length scale in the problem studied makes features grow linearly with time. The ensuing flow is related to the Guderley singularity in a cylindrical imploding shock. The problem is explored by making a large number of computations of the Euler equations. Distinct reflection configurations are identified, and the regions of parameter space in which they occur are delineated.

  12. The influence of incident shock Mach number on radial incident shock wave focusing

    NASA Astrophysics Data System (ADS)

    Chen, Xin; Tan, Sheng; He, Liming; Rong, Kang; Zhang, Qiang; Zhu, Xiaobin

    2016-04-01

    Experiments and numerical simulations were carried out to investigate radial incident shock focusing on a test section where the planar incident shock wave was divided into two identical ones. A conventional shock tube was used to generate the planar shock. Incident shock Mach number of 1.51, 1.84 and 2.18 were tested. CCD camera was used to obtain the schlieren photos of the flow field. Third-order, three step strong-stability-preserving (SSP) Runge-Kutta method, third-order weighed essential non-oscillation (WENO) scheme and adaptive mesh refinement (AMR) algorithm were adopted to simulate the complicated flow fields characterized by shock wave interaction. Good agreement between experimental and numerical results was observed. Complex shock wave configurations and interactions (such as shock reflection, shock-vortex interaction and shock focusing) were observed in both the experiments and numerical results. Some new features were observed and discussed. The differences of structure of flow field and the variation trends of pressure were compared and analyzed under the condition of different Mach numbers while shock wave focusing.

  13. Propagation of shock waves through petroleum suspensions

    NASA Astrophysics Data System (ADS)

    Mukuk, K. V.; Makhkamov, S. M.; Azizov, K. K.

    1986-01-01

    Anomalous shock wave propagation through petroleum with a high paraffin content was studied in an attempt to confirm the theoretically predicted breakdown of a forward shock wave into oscillating waves and wave packets as well as individual solitons. Tests were performed in a shock tube at 10, 20, and 50 to 60 C, with pure kerosene as reference and with kerosene + 5, 10, 15, and 20% paraffin. The addition of paraffin was found to radically alter the rheodynamic characteristics of the medium and, along with it, the pattern of shock wave propagation. The integro-differential equation describing a one dimensional hydraulic shock process in viscoelastic fluids is reduced to the Burgers-Korteweg-deVries equation, which is solved numerically for given values of the system parameters. The results indicate that the theory of shock wave propagation through such an anomalous suspension must be modified.

  14. Shock wave formation in the collapse of a vapor nanobubble.

    PubMed

    Magaletti, F; Marino, L; Casciola, C M

    2015-02-13

    In this Letter, the dynamics of a collapsing vapor bubble is addressed by means of a diffuse-interface formulation. The model cleanly captures, through a unified approach, all the critical features of the process, such as phase change, transition to supercritical conditions, thermal conduction, compressibility effects, and shock wave formation and propagation. Rather unexpectedly for pure vapor bubbles, the numerical experiments show that the process consists in the oscillation of the bubble associated with the emission of shock waves in the liquid, and with the periodic disappearance and reappearance of the liquid-vapor interface due to transition to super- or subcritical conditions. The results identify the mechanism of shock wave formation as strongly related to the transition of the vapor to the supercritical state, with a progressive steepening of a focused compression wave evolving into a shock which is eventually reflected as an outward propagating wave in the liquid. PMID:25723223

  15. Shock Wave Formation in the Collapse of a Vapor Nanobubble

    NASA Astrophysics Data System (ADS)

    Magaletti, F.; Marino, L.; Casciola, C. M.

    2015-02-01

    In this Letter, the dynamics of a collapsing vapor bubble is addressed by means of a diffuse-interface formulation. The model cleanly captures, through a unified approach, all the critical features of the process, such as phase change, transition to supercritical conditions, thermal conduction, compressibility effects, and shock wave formation and propagation. Rather unexpectedly for pure vapor bubbles, the numerical experiments show that the process consists in the oscillation of the bubble associated with the emission of shock waves in the liquid, and with the periodic disappearance and reappearance of the liquid-vapor interface due to transition to super- or subcritical conditions. The results identify the mechanism of shock wave formation as strongly related to the transition of the vapor to the supercritical state, with a progressive steepening of a focused compression wave evolving into a shock which is eventually reflected as an outward propagating wave in the liquid.

  16. Electron physics in shock waves

    NASA Astrophysics Data System (ADS)

    Kilian, Patrick

    2014-05-01

    The non-relativistic shocks that we find in the solar wind (no matter if driven by CMEs or encounters with planets) are dominated by ion dynamics. Therefore a detailed treatment of electrons is often neglegted to gain significant reductions in computational effort. With recent super computers and massively parallel codes it is possible to perform self-consistent kinetic simulations using particle in cell code. This allows to study the heating of the electrons as well as the acceleration to superthermal energies. These energetic electrons are interesting for couple of reasons. e.g. as an influence on plasma instabilities or for the generation of plasma waves.

  17. Interplanetary shock waves associated with solar flares

    NASA Technical Reports Server (NTRS)

    Chao, J. K.; Sakurai, K.

    1974-01-01

    The interaction of the earth's magnetic field with the solar wind is discussed with emphasis on the influence of solar flares. The geomagnetic storms are considerered to be the result of the arrival of shock wave generated by solar flares in interplanetary space. Basic processes in the solar atmosphere and interplanetary space, and hydromagnetic disturbances associated with the solar flares are discussed along with observational and theoretical problems of interplanetary shock waves. The origin of interplanetary shock waves is also discussed.

  18. Oblique interaction of waves with shocks

    NASA Astrophysics Data System (ADS)

    Morro, A.

    The oblique interaction between plane waves and shocks in materials described by a system of conservation equations is investigated. Two results are found. First, a straightforward geometric-kinematic analysis of the interaction yields a relation for each emergent mode (i.e., the outgoing wave) which determines the relation of propagation once the incident wave is given. Second, the shock may undergo an angular velocity which is ultimately related to the shock acceleration

  19. Analysis of shock-wave propagation in aqueous foams using shock tube experiments

    NASA Astrophysics Data System (ADS)

    Jourdan, G.; Mariani, C.; Houas, L.; Chinnayya, A.; Hadjadj, A.; Del Prete, E.; Haas, J.-F.; Rambert, N.; Counilh, D.; Faure, S.

    2015-05-01

    This paper reports experimental results of planar shock waves interacting with aqueous foams in a horizontal conventional shock tube. Four incident shock wave Mach numbers are considered, ranging from 1.07 to 1.8, with two different foam columns of one meter thickness and expansion ratios of 30 and 80. High-speed flow visualizations are used along with pressure measurements to analyse the main physical mechanisms that govern shock wave mitigation in foams. During the shock/foam interaction, a precursor leading pressure jump was identified as the trace of the liquid film destruction stage in the foam fragmentation process. The corresponding pressure threshold is found to be invariant for a given foam. Regarding the mitigation effect, the results show that the speed of the shock is drastically reduced and that wetter is the foam, slower are the transmitted waves. The presence of the foam barrier attenuates the induced pressure impulse behind the transmitted shock, while the driest foam appears to be more effective, as it limits the pressure induced by the reflected shock off the foam front. Finally, it was found that the pressure histories in the two-phase gas-liquid mixture are different from those previously obtained within a cloud of droplets. The observed behavior is attributed to the process of foam fragmentation and to the modification of the flow topology past the shock. These physical phenomena occurring during the shock/foam interaction should be properly accounted for when elaborating new physical models.

  20. The role of divergences for shock waves

    NASA Astrophysics Data System (ADS)

    Uribe, Francisco

    2013-11-01

    Several continuum theories for shock waves give rise to a set of differential equations in which the analysis of the underlying vector field can be done using the tools of the theory of dynamical systems. We illustrate the importance of the divergences associated with the vector field by considering the ideas by Maxwell and Cattaneo and applied them to study shock waves in dilute gases. Different theoretical descriptions for shock waves are mentioned and some of them are compared with experimental data and computer simulations. Our goal is to derive conditions under which the shock wave problem has a solution by analyzing the singularities of the vector field.

  1. A study of slipstreams in triple shock wave configurations

    NASA Astrophysics Data System (ADS)

    Gvozdeva, L.; Gavrenkov, S.; Nesterov, A.

    2015-05-01

    A shock wave appearing in supersonic gas flow reflects in different ways depending on flow conditions. It can take the form of regular or irregular reflection. For the irregular reflection configuration of three shock waves and a slipstream arises. Mathematical investigations of the development of parameters across slipstream in triple shock configuration have been made with variation of the angle of incidence of the shock wave, the shock wave Mach number and the adiabatic index of the gas. It has been shown that the characteristic mixing parameters of the slipstream increase with the increase of Mach number of the flow and the decrease of the heat capacity ratio. This leads to an increase of vortex formation and an increase of the angular spread of the slipstream. It also has been shown that the angle between the reflected wave and the slipstream diminishes with the decrease in heat capacity ratio so that the value may become of the same order as the spread angle. This may lead to quantitative changes in the whole reflection pattern near the triple point. The evident dependence of slipstream instability magnitude on the physical and chemical transformation intensity in the fluid was previously experimentally observed. The results of an analytical investigation appeared to be in good agreement with the experimental data.

  2. Implications of pressure diffusion for shock waves

    NASA Technical Reports Server (NTRS)

    Ram, Ram Bachan

    1989-01-01

    The report deals with the possible implications of pressure diffusion for shocks in one dimensional traveling waves in an ideal gas. From this new hypothesis all aspects of such shocks can be calculated except shock thickness. Unlike conventional shock theory, the concept of entropy is not needed or used. Our analysis shows that temperature rises near a shock, which is of course an experimental fact; however, it also predicts that very close to a shock, density increases faster than pressure. In other words, a shock itself is cold.

  3. Shock Waves Impacting Composite Material Plates: The Mutual Interaction

    NASA Astrophysics Data System (ADS)

    Andreopoulos, Yiannis

    2013-02-01

    High-performance, fiber-reinforced polymer composites have been extensively used in structural applications in the last 30 years because of their light weight combined with high specific stiffness and strength at a rather low cost. The automotive industry has adopted these materials in new designs of lightweight vehicles. The mechanical response and characterization of such materials under transient dynamic loading caused with shock impact induced by blast is not well understood. Air blast is associated with a fast traveling shock front with high pressure across followed by a decrease in pressure behind due to expansion waves. The time scales associated with the shock front are typically 103 faster than those involved in the expansion waves. Impingement of blast waves on structures can cause a reflection of the wave off the surface of the structure followed by a substantial transient aerodynamic load, which can cause significant deformation and damage of the structure. These can alter the overpressure, which is built behind the reflected shock. In addition, a complex aeroelastic interaction between the blast wave and the structure develops that can induce reverberation within an enclosure, which can cause substantial overpressure through multiple reflections of the wave. Numerical simulations of such interactions are quite challenging. They usually require coupled solvers for the flow and the structure. The present contribution provides a physics-based analysis of the phenomena involved, a critical review of existing computational techniques together with some recent results involving face-on impact of shock waves on thin composite plates.

  4. Shock Wave Technology and Application: An Update☆

    PubMed Central

    Rassweiler, Jens J.; Knoll, Thomas; Köhrmann, Kai-Uwe; McAteer, James A.; Lingeman, James E.; Cleveland, Robin O.; Bailey, Michael R.; Chaussy, Christian

    2012-01-01

    Context The introduction of new lithotripters has increased problems associated with shock wave application. Recent studies concerning mechanisms of stone disintegration, shock wave focusing, coupling, and application have appeared that may address some of these problems. Objective To present a consensus with respect to the physics and techniques used by urologists, physicists, and representatives of European lithotripter companies. Evidence acquisition We reviewed recent literature (PubMed, Embase, Medline) that focused on the physics of shock waves, theories of stone disintegration, and studies on optimising shock wave application. In addition, we used relevant information from a consensus meeting of the German Society of Shock Wave Lithotripsy. Evidence synthesis Besides established mechanisms describing initial fragmentation (tear and shear forces, spallation, cavitation, quasi-static squeezing), the model of dynamic squeezing offers new insight in stone comminution. Manufacturers have modified sources to either enlarge the focal zone or offer different focal sizes. The efficacy of extracorporeal shock wave lithotripsy (ESWL) can be increased by lowering the pulse rate to 60–80 shock waves/min and by ramping the shock wave energy. With the water cushion, the quality of coupling has become a critical factor that depends on the amount, viscosity, and temperature of the gel. Fluoroscopy time can be reduced by automated localisation or the use of optical and acoustic tracking systems. There is a trend towards larger focal zones and lower shock wave pressures. Conclusions New theories for stone disintegration favour the use of shock wave sources with larger focal zones. Use of slower pulse rates, ramping strategies, and adequate coupling of the shock wave head can significantly increase the efficacy and safety of ESWL. PMID:21354696

  5. Ultra low frequency waves at the Earth's bow shock

    NASA Technical Reports Server (NTRS)

    Russell, C. T.; Farris, M. H.

    1995-01-01

    The Earth's bow shock is a bountiful generator of waves. Some of these waves have group velocities that exceed the solar wind velocity directed into the shock and can propagate upstream against the flow. Upstream whistlers observed close to one Hertz in the spacecraft frame have been seen many Earth radii upstream. A second whistler mode wave, called the precursor, propagates upstream along the shock normal but is phase standing in the solar wind flow. The damping of both whistler mode waves is consistent with Landau damping. At low Mach numbers the precursor is connected to the non-coplanarity component in the shock ramp. At higher Mach numbers the upstream waves cannot propagate upstream and ion reflection becomes more important in providing free energy for wave particle interactions. The non-coplanarity component is still present but it now initiates a downstream wave train. Generally the waves just downstream from the bow shock are left hand circularly polarized ion cyclotron waves propagating along the magnetic field at the Alfven velocity. When the upstream Mach number is high and the helium content of the plasma is high, mirror mode waves are observed.

  6. Augmented Shock Wave Severance of Materials

    NASA Technical Reports Server (NTRS)

    Bement, Laurence J.; Schimmel, Morry L.

    1995-01-01

    This paper describes a new approach for severing or weakening a variety of materials. The technique employs embedding explosive cords into parallel grooves that are cut into a surface of a material. The cords are initiated simultaneously to produce shock waves that progress toward the centerline between the cords and the lower surface of the material. Intersecting incident and reflected waves augment at the centerline to fail or weaken the material in tension. No harmful debris is produced on the opposite side of the material from the explosive cords. The primary focus of the effort described in this paper was to fracture the F-16 aircraft trilaminate canopy. Also, complete severance was achieved in 2024-T4 aluminum plate stock. Possible applications are through canopy egress and crew module severance from military aircraft and separation of rocket vehicle stages and payloads. This approach offers important advantages over explosive methods currently in use.

  7. Gigabar shock wave in a laboratory experiment

    NASA Astrophysics Data System (ADS)

    Gus'kov, S. Yu.

    2016-03-01

    The current status of research on generating a powerful shock wave with a pressure of up to several gigabars in a laboratory experiment is reviewed. The focus is on results which give a possibility of shock-wave experiments to study an equation of state of matter (EOS) at the level of gigabar pressure. The proposals are discussed to achieve a plane record-pressure shock wave driven by laser-accelerated fast electrons with respect to EOS-experiment as well as to prospective method of inertial fusion target (ICF) ignition as shock ignition.

  8. Noise transmission along shock-waves

    NASA Astrophysics Data System (ADS)

    Amur Varadarajan, Prasanna

    Shocks at the inlet of scramjet engines are subject to perturbations from their interaction with turbulent boundary layer. DNS results for this interaction indicate the presence of discrete vortices that interact with the shock at its foot. These studies reveal that the vortices cause oscillations of the shock. In this work we examine the propagation of disturbances along a stationary oblique shock following interaction with a two-dimensional vortex. We study the decay of disturbances along a normal shock as measured from Euler computations and compare these with the predictions of Geometrical Shock Dynamics (GSD) for long range propagation. We have incorporated two improvements into the GSD model to tackle the shock-vortex interaction problem. The wave structure of the disturbance resembles N waves, the decay of which follows a power law profile. An extension of the GSD model to predict shock surface propagation in 3-D flows is presented along with the numerical implementation.

  9. Biological Effects of Shock Waves on Infection

    NASA Astrophysics Data System (ADS)

    Gnanadhas, Divya Prakash; Janardhanraj, S.; Chakravortty, Dipshikha; Gopalan, Jagadeesh

    Shock waves have been successfully used for disintegrating kidney stones[1], noninvasive angiogenic approach[2] and for the treatment of osteoporosis[3]. Recently shock waves have been used to treat different medical conditions including intestinal anastomosis[4], wound healing[5], Kienböck's disease[6] and articular cartilage defects[7].

  10. Clinical application of extracorporeal shock wave therapy in orthopedics: focused versus unfocused shock waves.

    PubMed

    Foldager, Casper Bindzus; Kearney, Cathal; Spector, Myron

    2012-10-01

    For the past decade extracorporeal shock wave therapy has been applied to a wide range of musculoskeletal disorders. The many promising results and the introduction of shock wave generators that are less expensive and easier to handle has added to the growing interest. Based on their nature of propagation, shock waves can be divided into two types: focused and unfocused. Although several physical differences between these different types of shock waves have been described, very little is known about the clinical outcome using these different modalities. The aim of the present review is to investigate differences in outcome in select orthopaedic applications using focused and unfocused shock waves. PMID:22920552

  11. Spherical shock waves in general relativity

    SciTech Connect

    Nutku, Y. )

    1991-11-15

    We present the metric appropriate to a spherical shock wave in the framework of general relativity. This is a Petrov type-{ital N} vacuum solution of the Einstein field equations where the metric is continuous across the shock and the Riemann tensor suffers a step-function discontinuity. Spherical gravitational waves are described by type-{ital N} Robinson-Trautman metrics. However, for shock waves the Robinson-Trautman solutions are unacceptable because the metric becomes discontinuous in the Robinson-Trautman coordinate system. Other coordinate systems that have so far been introduced for describing Robinson-Trautman solutions also suffer from the same defect. We shall present the {ital C}{sup 0}-form of the metric appropriate to spherical shock waves using Penrose's approach of identification with warp. Further extensions of Penrose's method yield accelerating, as well as coupled electromagnetic-gravitational shock-wave solutions.

  12. Shock wave mitigation using Newtonian and non-Newtonian fluids

    NASA Astrophysics Data System (ADS)

    Tao, Xingtian; Colvert, Brendan; Eliasson, Veronica

    2014-11-01

    The effectiveness of a wall of liquid as a blast mitigation device is examined using a shock tube and a custom-designed and -built shock test chamber. High-speed schlieren photography and high-frequency pressure sensors allow measurement during the relevant shock interaction time periods of the liquid-gas interface. The characteristic quantities that reflect these effects include reflected-to-incident shock strength ratio, transmitted-to-incident shock strength ratio, transmitted and reflected impulse, and peak pressure reduction. In particular, the effects of viscous properties of the fluid are considered when using non-Newtonian dilatant and pseudoplastic fluids. Experiments have been performed with both Newtonian and non-Newtonian fluids. The impact of a shock waves on Non-newtonian fluids is compared to that of Newtonian fluids. Experiments show that non-Newtonian fluids have very strong reflection properties, acting like solid walls under the impact of a shock wave. Further work is to be performed to compare quantitatively the properties of Newtonian vs. non-Newtonian fluids.

  13. Computing unsteady shock waves for aeroacoustic applications

    NASA Technical Reports Server (NTRS)

    Meadows, Kristine R.; Caughey, David A.; Casper, Jay

    1994-01-01

    The computation of unsteady shock waves, which contribute significantly to noise generation in supersonic jet flows, is investigated. The paper focuses on the difficulties of computing slowly moving shock waves. Numerical error is found to manifest itself principally as a spurious entropy wave. Calculations presented are performed using a third-order essentially nonoscillatory scheme. The effect of stencil biasing parameters and of two versions of numerical flux formulas on the magnitude of spurious entropy are investigated. The level of numerical error introduced in the calculation is quantified as a function of shock pressure ratio, shock speed, Courant number, and mesh density. The spurious entropy relative to the entropy jump across a static shock decreases with increasing shock strength and shock velocity relative to the grid, but is insensitive to Courant number. The structure of the spurious entropy wave is affected by the choice of flux formulas and algorithm biasing parameters. The effect of the spurious numerical waves on the calculation of sound amplification by a shock wave is investigated. For this class of problem, the acoustic pressure waves are relatively unaffected by the spurious numerical phenomena.

  14. Computing unsteady shock waves for aeroacoustic applications

    NASA Technical Reports Server (NTRS)

    Meadows,, Kristine r.; Caughey, David A.; Casper, Jay

    1994-01-01

    The computation of unsteady shock waves, which contribute significantly to noise generation in supersonic jet flows, is investigated. This paper focuses on the difficulties of computing slowly moving shock waves. Numerical error is found to manifest itself principally as a spurious entropy wave. Calculations presented are performed using a third order essentially nonoscillatory scheme. The effect of stencil biasing parameters and of two versions of numerical flux formulas on the magnitude of spurious entropy are investigated. The level of numerical error introduced in the calculation in quantified as a function of shock pressure ratio, shock speed, Courant number, and mesh density. The spurious entropy relative to the entropy jump across a static shock decreases with increasing shock strength and shock velocity relative to the grid, but is insensitive to Courant number. The structure of the spurious entropy wave is affected by the choice of flux formulas and algorithm biasing parameters. The effect of the spurious numerical waves on the calculation of sound amplification by a shock wave is investigated. For this class of problem, the acoustic pressure waves are relatively unaffected by the spurious numerical phenomena.

  15. Whistler Waves Associated with Weak Interplanetary Shocks

    NASA Technical Reports Server (NTRS)

    Velez, J. C. Ramirez; Blanco-Cano, X.; Aguilar-Rodriguez, E.; Russell, C. T.; Kajdic, P.; Jian,, L. K.; Luhmann, J. G.

    2012-01-01

    We analyze the properties of 98 weak interplanetary shocks measured by the dual STEREO spacecraft over approximately 3 years during the past solar minimum. We study the occurrence of whistler waves associated with these shocks, which on average are high beta shocks (0.2 < Beta < 10). We have compared the waves properties upstream and downstream of the shocks. In the upstream region the waves are mainly circularly polarized, and in most of the cases (approx. 75%) they propagate almost parallel to the ambient magnetic field (<30 deg.). In contrast, the propagation angle with respect to the shock normal varies in a broad range of values (20 deg. to 90 deg.), suggesting that they are not phase standing. We find that the whistler waves can extend up to 100,000 km in the upstream region but in most cases (88%) are contained in a distance within 30,000 km from the shock. This corresponds to a larger region with upstream whistlers associated with IP shocks than previously reported in the literature. The maximum amplitudes of the waves are observed next to the shock interface, and they decrease as the distance to the shock increases. In most cases the wave propagation direction becomes more aligned with the magnetic field as the distance to the shock increases. These two facts suggest that most of the waves in the upstream region are Landau damping as they move away from the shock. From the analysis we also conclude that it is likely that the generation mechanism of the upstream whistler waves is taking place at the shock interface. In the downstream region, the waves are irregularly polarized, and the fluctuations are very compressive; that is, the compressive component of the wave clearly dominates over the transverse one. The majority of waves in the downstream region (95%) propagate at oblique angles with respect to the ambient magnetic field (>60 deg.). The wave propagation with respect to the shock-normal direction has no preferred direction and varies similarly to

  16. Shock Wave Dynamics in Weakly Ionized Plasmas

    NASA Technical Reports Server (NTRS)

    Johnson, Joseph A., III

    1999-01-01

    An investigation of the dynamics of shock waves in weakly ionized argon plasmas has been performed using a pressure ruptured shock tube. The velocity of the shock is observed to increase when the shock traverses the plasma. The observed increases cannot be accounted for by thermal effects alone. Possible mechanisms that could explain the anomalous behavior include a vibrational/translational relaxation in the nonequilibrium plasma, electron diffusion across the shock front resulting from high electron mobility, and the propagation of ion-acoustic waves generated at the shock front. Using a turbulence model based on reduced kinetic theory, analysis of the observed results suggest a role for turbulence in anomalous shock dynamics in weakly ionized media and plasma-induced hypersonic drag reduction.

  17. Instability of spherically imploding shock waves

    SciTech Connect

    Chen, H.; Hilko, B.; Zhang, L.; Panarella, E.

    1995-12-31

    The importance of spherically imploding shock waves has increased recently due to their particular applications in inertial confinement fusion (ICF) and the Spherical Pinch (SP). In particular, the stability of spherically imploding shock waves plays a critical role in the ultimate success of ICF and SP. The instability of spherically imploding shock waves is now systematically investigated. The basic state is Guderley and Landau`s unsteady self-similar solution of the implosion of a spherical shock wave. The stability analysis is conducted by combining Chandresakhar`s approach to the stability of spherical flames together. The governing equations for disturbances are derived and they use the condition that perturbed gas flow is potential. The three dimensional perturbation velocity profile and a shock front perturbation are solved by using the kinematic and dynamic boundary conditions in the shock front. The time-dependent amplitudes of the perturbations are obtained by solving the system of ordinary differential equations. This enables them to study the time history of the spherically imploding shock wave subject to perturbations. The relative amplification and decay of the amplitudes of perturbations decides the stability/instability of the spherical imploding shock waves. Preliminary results are presented.

  18. Stability of imploding spherical shock waves

    NASA Astrophysics Data System (ADS)

    Chen, H. B.; Zhang, L.; Panarella, E.

    1995-12-01

    The stability of spherically imploding shock waves is systematically investigated in this letter. The basic state is Guderley and Landau's unsteady self-similar solution of the implosion of a spherical shock wave. The stability analysis is conducted by combining Chandrasekhar's approach to the stability of a viscous liquid drop with Zel'dovich's approach to the stability of spherical flames. The time-dependent amplitudes of the perturbations are obtained analytically by using perturbation method. The relative amplification and decay of the amplitudes of perturbations decides the stability/instability of the spherical imploding shock waves. It is found that the growth rate of perturbations is not in exponential form and near the collapse phase of the shocks, the spherically imploding shock waves are relatively stable.

  19. Stability of imploding spherical shock waves

    SciTech Connect

    Chen, H.B.; Zhang, L.; Panarella, E.

    1995-12-01

    The stability of spherically imploding shock waves is systematically investigated in this letter. The basic state is Guderley and Landau`s unsteady self-similar solution of the implosion of a spherical shock wave. The stability analysis is conducted by combining Chandrasekhar`s approach to the stability of a viscous liquid drop with Zel`dovich`s approach to the stability of spherical flames. The time-dependent amplitudes of the perturbations are obtained analytically by using perturbation method. The relative amplification and decay of the amplitudes of perturbations are obtained analytically by using perturbation method. The relative amplification and decay of the amplitudes of perturbations decides the stability/instability of the spherical imploding shock waves. It is found that the growth rate of perturbations is not in exponential form and near the collapse phase of the shocks, the spherically imploding shock waves are relatively stable. 14 refs., 1 fig.

  20. Relativistic magnetosonic shock waves in synchrotron sources - Shock structure and nonthermal acceleration of positrons

    NASA Technical Reports Server (NTRS)

    Hoshino, Masahiro; Arons, Jonathan; Gallant, Yves A.; Langdon, A. B.

    1992-01-01

    The theoretical properties of relativistic, transverse, magnetosonic collisionless shock waves in electron-positron-heavy ion plasmas of relevance to astrophysical sources of synchrotron radiation are investigated. Both 1D electromagnetic particle-in-cell simulations and quasi-linear theory are used to examine the spatial and kinetic structure of these nonlinear flows. A new process of shock acceleration of nonthermal positrons, in which the gyrating reflected heavy ions dissipate their energy in the form of collectively emitted, left-handed magnetosonic waves which are resonantly absorbed by the positrons immediately behind the ion reflection region, is described. Applications of the results to the termination shocks of pulsar winds and to the termination shocks of jets emanating from the AGN are outlined.

  1. Guderley reflection for higher Mach numbers in a standard shock tube

    NASA Astrophysics Data System (ADS)

    Cachucho, A.; Skews, B. W.

    2012-03-01

    An experimental study shows that the Guderley reflection (GR) of shock waves can be produced in a standard shock tube. A new technique was utilised which comprises triple point of a developed weak Mach reflection undergoing a number of reflections off the ceiling and floor of the shock tube before arriving at the test section. Both simple perturbation sources and diverging ramps were used to generate a transverse wave in the tube which then becomes the weak reflected wave of the reflection pattern. Tests were conducted for three ramp angles (10°, 15°, and 20°) and two perturbation sources for a range of Mach numbers (1.10-1.40) and two shock tube expansion chamber lengths (2.0 and 4.0 m). It was found that the length of the Mach stem of the reflection pattern is the overall vertical distance traveled by the triple point. Images with equivalent Mach stem lengths in the order of 2.0 m were produced. All tests showed evidence of the fourth wave of the GR, namely the expansion wave behind the reflected shock wave. A shocklet terminating the expansion wave was also identified in a few cases mainly for incident wave Mach numbers of approximately 1.20.

  2. Free boundary problems in shock reflection/diffraction and related transonic flow problems.

    PubMed

    Chen, Gui-Qiang; Feldman, Mikhail

    2015-09-13

    Shock waves are steep wavefronts that are fundamental in nature, especially in high-speed fluid flows. When a shock hits an obstacle, or a flying body meets a shock, shock reflection/diffraction phenomena occur. In this paper, we show how several long-standing shock reflection/diffraction problems can be formulated as free boundary problems, discuss some recent progress in developing mathematical ideas, approaches and techniques for solving these problems, and present some further open problems in this direction. In particular, these shock problems include von Neumann's problem for shock reflection-diffraction by two-dimensional wedges with concave corner, Lighthill's problem for shock diffraction by two-dimensional wedges with convex corner, and Prandtl-Meyer's problem for supersonic flow impinging onto solid wedges, which are also fundamental in the mathematical theory of multidimensional conservation laws. PMID:26261363

  3. Ion-acoustic shocks with reflected ions: modelling and particle-in-cell simulations

    NASA Astrophysics Data System (ADS)

    Liseykina, T. V.; Dudnikova, G. I.; Vshivkov, V. A.; Malkov, M. A.

    2015-10-01

    > Non-relativistic collisionless shock waves are widespread in space and astrophysical plasmas and are known as efficient particle accelerators. However, our understanding of collisionless shocks, including their structure and the mechanisms whereby they accelerate particles, remains incomplete. We present here the results of numerical modelling of an ion-acoustic collisionless shock based on the one-dimensional kinetic approximation for both electrons and ions with a real mass ratio. Special emphasis is paid to the shock-reflected ions as the main driver of shock dissipation. The reflection efficiency, the velocity distribution of reflected particles and the shock electrostatic structure are studied in terms of the shock parameters. Applications to particle acceleration in geophysical and astrophysical shocks are discussed.

  4. Overview of shock waves in medicine

    NASA Astrophysics Data System (ADS)

    Cleveland, Robin O.

    2003-10-01

    A brief overview of three applications of shock waves is presented. Shock wave lithotripsy (SWL) has been in clinical use for more than 20 years. In the United States it is used to treat more than 80% of kidney stone cases and has wide acceptance with patients because it is a noninvasive procedure. Despite SWLs enormous success there is no agreement on how shock waves comminute stones. There is also a general acceptance that shock waves lead to trauma to the soft tissue of the kidney. Yet there has been little forward progress in developing lithotripters which provide comminution with less side-effects, indeed the original machine is still considered the gold standard. The last decade has seen the advent of new shock wave devices for treating principally musculoskeletal indications, such as plantar fasciitis, tennis elbow, and bone fractures that do not heal. This is referred to as shock wave therapy (SWT). The mechanisms by which SWT works are even less well understood than SWL and the consequences of bioeffects have also not been studied in detail. Shock waves have also been shown to be effective at enhancing drug delivery into cells and assisting with gene transfection. [Work partially supported by NIH.

  5. Oblique shock reflection from an axis of symmetry: shock dynamics and relation to the Guderley singularity

    NASA Astrophysics Data System (ADS)

    Hornung, H. G.; Schwendeman, D. W.

    2001-07-01

    Oblique shock reflection from an axis of symmetry is studied using Whitham's theory of geometrical shock dynamics, and the results are compared with previous numerical simulations of the phenomenon by Hornung (2000). The shock shapes (for strong and weak shocks), and the location of the shock-shock (for strong shocks), are in good agreement with the numerical results, though the detail of the shock reflection structure is, of course, not resolved by shock dynamics. A guess at a mathematical form of the shock shape based on an analogy with the Guderley singularity in cylindrical shock implosion, in the form of a generalized hyperbola, fits the shock shape very well. The smooth variation of the exponent in this equation with initial shock angle from the Guderley value at zero to 0.5 at 90° supports the analogy. Finally, steady-flow shock reflection from a symmetry axis is related to the self-similar flow.

  6. Magnetohydrodynamic shock waves in molecular clouds

    SciTech Connect

    Draine, B.T.; Roberge, W.G.; Dalgarno, A.

    1983-01-15

    The structure of shock waves in molecular clouds is calculated, including the effects of ion-neutral streaming driven by the magnetic field. It is found that shock waves in molecular clouds will usually be C-type shock waves, mediated entirely by the dissipation accompanying ion-neutral streaming, and in which all of the hydrodynamic variables are continuous. Detailed results are presented for magnetohydrodynamic shock waves propagating at speeds in the range of 5--50 km s/sup -1/ in molecular clouds with preshock densities n/sub H/ = 10/sup 2/, 10/sup 4/, and 10/sup 6/ cm/sup -3/. Graphs are constructed of the effective ''excitation temperatures'' of the rotational and vibrational levels of H/sub 2/ in the shocked gas. The effects of chemical changes in the composition of oxygen-bearing molecules are investigated, and the contributions to the cooling of the shocked gas by emission from H/sub 2/, CO, OH, and H/sub 2/O are evaluated. Predictions are made of the intensities of the rotation-vibration lines of H/sub 2/ and of the fine-structure lines of O I and C I. Magnetic fields may lead to a substantial increase in the limiting shock velocity above which dissociation of H/sub 2/ takes place: for a cloud of density eta/sub H/ = 10/sup 6/ cm/sup -3/, the limiting shock speed is approx.45 km s/sup -1/. The fractional ionization is a critical parameter affecting the shock structure, and the processes acting to change the ionization in the shock are examined. Magnetic field effects enhance the sputtering of grain mantles in dense gas: H/sub 2/O ice mantles can be substantially eroded in v/sub s/> or =25 km s/sup -1/ shock waves. Grain erosion may contribute to the enhancement of some molecular species in the shocked gas.

  7. Ion acoustic shock waves in degenerate plasmas

    SciTech Connect

    Akhtar, N.; Hussain, S.

    2011-07-15

    Korteweg de Vries Burgers equation for negative ion degenerate dissipative plasma has been derived using reductive perturbation technique. The quantum hydrodynamic model is used to study the quantum ion acoustic shock waves. The effects of different parameters on quantum ion acoustic shock waves are studied. It is found that quantum parameter, electrons Fermi temperature, temperature of positive and negative ions, mass ratio of positive to negative ions, viscosity, and density ratio have significant impact on the shock wave structure in negative ion degenerate plasma.

  8. Rarefaction shock waves in shock-compressed diamond <110> crystal

    NASA Astrophysics Data System (ADS)

    Perriot, Romain; Lin, You; Zhakhovsky, Vasily; White, Carter; Oleynik, Ivan

    2013-03-01

    Piston-driven shock compression of diamond <110> crystal was simulated by molecular dynamics using the REBO potential. At piston velocities between 2 and 5 km/s and corresponding pressures 117 GPA < P < 278 GPa, diamond sample undergoes a polymorphic phase transition, characterized by the coexistence of two elastically compressed phases, low-pressure phase A and high-pressure phase B. This phase transition results in the splitting of the shock wave into two elastic shock waves, composed of pure phase A and a mixture of phases A and B. Upon removal of the piston, a release wave is observed at the rear of the sample, turning into a rarefaction shock wave where the material undergoes the reverse phase transition from coexisting phases to the original low-pressure phase. For strong plastic waves induced by larger piston velocities the release wave propagates as a rarefaction wave without any phase transition corresponding to the adiabatic expansion along the plastic branch of the Hugoniot.

  9. Investigation of the hysteresis phenomena in steady shock reflection using kinetic and continuum methods

    NASA Astrophysics Data System (ADS)

    Ivanov, M.; Zeitoun, D.; Vuillon, J.; Gimelshein, S.; Markelov, G.

    1996-05-01

    The problem of transition of planar shock waves over straight wedges in steady flows from regular to Mach reflection and back was numerically studied by the DSMC method for solving the Boltzmann equation and finite difference method with FCT algorithm for solving the Euler equations. It is shown that the transition from regular to Mach reflection takes place in accordance with detachment criterion while the opposite transition occurs at smaller angles. The hysteresis effect was observed at increasing and decreasing shock wave angle.

  10. Unsteady oblique interaction of a shock wave with a plane disturbance

    NASA Technical Reports Server (NTRS)

    Moore, Franklin K

    1954-01-01

    Analysis is made of the flow field produced by oblique impingement of weak plane disturbances of arbitrary profile on a plane normal shock. Three types of disturbance are considered: (a) sound wave propagating in the gas at rest into which the shock moves; (b) sound wave overtaking the shock from behind,(The sound wave reflects as a sound wave, and a stationary vorticity wave is produced); (c) an incompressible vorticity wave stationary in the gas ahead of the shock. The incident wave refracts as a stationary vorticity wave, and either a sound wave or attenuating pressure wave is also produced. Computations are presented for the first two types of incident wave, over the range of incidence angles, for shock Mach numbers of 1, 1.5, and infinity.

  11. Shock wave dispersion in weakly ionized gas

    NASA Astrophysics Data System (ADS)

    Kessaratikoon, Prasong

    2003-10-01

    Electrodeless microwave (MW) discharge in two straight, circular cylindrical resonant cavities in TE1,1,1 and TM0,1,2 modes were introduced to perform additional experimental studies on shock wave modification in non-equilibrium weakly ionized gases and to clarify the physical mechanisms of the shock wave modification process. The discharge was generated in 99.99% Ar at a gas pressure between 20 and 100 Torr and at a discharge power density less than 10.0 Watts/cm3. Power density used for operating the discharge was rather low in the present work, which was determined by evaluating the power loss inside the resonant cavity. It was found that the shock wave deflection signal amplitude was decreased while the shock wave local velocity was increased in the presence of the discharge. However, there was no apparent evidence of the multiple shock structure or the widening of the shock wave deflection signal, as observed in the d.c. glow discharge [3,5]. The shock wave always retained a more compact structure even in the case of strong dispersion in both the TE and the TM mode. The shock wave propagated faster through the discharge in the TE mode than in the TM mode. Discharge characteristics and local parameters such as gas temperature T g, electron density Ne, local electric field E, and average power density, were determined by using the MW discharge generated from an Argon gas mixture that contains 95% Ar, 5% H2, and traces of N2. The gas temperature was evaluated by using the amplitude reduction technique and the emission spectroscopy of Nitrogen. The gas temperature distribution was flat in the central region of the cavity. By comparing the gas temperature calculated from the shock wave local velocity and from the amplitude reduction technique, the present work was sufficiently accurate to indicate that the thermal effect is dominant. The electron density was obtained from measured line shapes of hydrogen Balmer lines by using the gas temperature and the well

  12. Incidence of cavitation in the fragmentation process of extracorporeal shock wave lithotriptors

    NASA Astrophysics Data System (ADS)

    Rink, K.; Delacrétaz, G.; Pittomvils, G.; Boving, R.; Lafaut, J. P.

    1994-05-01

    The fragmentation mechanism occurring in extracorporeal shock wave lithotripsy (ESWL) is investigated using a fiber optic stress sensing technique. With our technique, we demonstrate that cavitation is a major cause of fragmentation in ESWL procedures. When a target is placed in the operating area of the lithotriptor, two shock waves are detected. The first detected shock wave corresponds to the incoming shock wave generated by the lithotriptor. The second shock wave, detected some hundreds of microseconds later, is generated in situ. It results from the collapse of a cavitation bubble, formed by the reflection of the incoming shock wave at the target boundary. This cavitation induced shock wave generates the largest stress in the target area according to our stress sensing measurements.

  13. Mach stem formation in reflection and focusing of weak shock acoustic pulses.

    PubMed

    Karzova, Maria M; Khokhlova, Vera A; Salze, Edouard; Ollivier, Sébastien; Blanc-Benon, Philippe

    2015-06-01

    The aim of this study is to show the evidence of Mach stem formation for very weak shock waves with acoustic Mach numbers on the order of 10(-3) to 10(-2). Two representative cases are considered: reflection of shock pulses from a rigid surface and focusing of nonlinear acoustic beams. Reflection experiments are performed in air using spark-generated shock pulses. Shock fronts are visualized using a schlieren system. Both regular and irregular types of reflection are observed. Numerical simulations are performed to demonstrate the Mach stem formation in the focal region of periodic and pulsed nonlinear beams in water. PMID:26093452

  14. The microphysics of collisionless shock waves.

    PubMed

    Marcowith, A; Bret, A; Bykov, A; Dieckman, M E; Drury, L O'C; Lembège, B; Lemoine, M; Morlino, G; Murphy, G; Pelletier, G; Plotnikov, I; Reville, B; Riquelme, M; Sironi, L; Novo, A Stockem

    2016-04-01

    Collisionless shocks, that is shocks mediated by electromagnetic processes, are customary in space physics and in astrophysics. They are to be found in a great variety of objects and environments: magnetospheric and heliospheric shocks, supernova remnants, pulsar winds and their nebulæ, active galactic nuclei, gamma-ray bursts and clusters of galaxies shock waves. Collisionless shock microphysics enters at different stages of shock formation, shock dynamics and particle energization and/or acceleration. It turns out that the shock phenomenon is a multi-scale non-linear problem in time and space. It is complexified by the impact due to high-energy cosmic rays in astrophysical environments. This review adresses the physics of shock formation, shock dynamics and particle acceleration based on a close examination of available multi-wavelength or in situ observations, analytical and numerical developments. A particular emphasis is made on the different instabilities triggered during the shock formation and in association with particle acceleration processes with regards to the properties of the background upstream medium. It appears that among the most important parameters the background magnetic field through the magnetization and its obliquity is the dominant one. The shock velocity that can reach relativistic speeds has also a strong impact over the development of the micro-instabilities and the fate of particle acceleration. Recent developments of laboratory shock experiments has started to bring some new insights in the physics of space plasma and astrophysical shock waves. A special section is dedicated to new laser plasma experiments probing shock physics. PMID:27007555

  15. The microphysics of collisionless shock waves

    NASA Astrophysics Data System (ADS)

    Marcowith, A.; Bret, A.; Bykov, A.; Dieckman, M. E.; O'C Drury, L.; Lembège, B.; Lemoine, M.; Morlino, G.; Murphy, G.; Pelletier, G.; Plotnikov, I.; Reville, B.; Riquelme, M.; Sironi, L.; Stockem Novo, A.

    2016-04-01

    Collisionless shocks, that is shocks mediated by electromagnetic processes, are customary in space physics and in astrophysics. They are to be found in a great variety of objects and environments: magnetospheric and heliospheric shocks, supernova remnants, pulsar winds and their nebulæ, active galactic nuclei, gamma-ray bursts and clusters of galaxies shock waves. Collisionless shock microphysics enters at different stages of shock formation, shock dynamics and particle energization and/or acceleration. It turns out that the shock phenomenon is a multi-scale non-linear problem in time and space. It is complexified by the impact due to high-energy cosmic rays in astrophysical environments. This review adresses the physics of shock formation, shock dynamics and particle acceleration based on a close examination of available multi-wavelength or in situ observations, analytical and numerical developments. A particular emphasis is made on the different instabilities triggered during the shock formation and in association with particle acceleration processes with regards to the properties of the background upstream medium. It appears that among the most important parameters the background magnetic field through the magnetization and its obliquity is the dominant one. The shock velocity that can reach relativistic speeds has also a strong impact over the development of the micro-instabilities and the fate of particle acceleration. Recent developments of laboratory shock experiments has started to bring some new insights in the physics of space plasma and astrophysical shock waves. A special section is dedicated to new laser plasma experiments probing shock physics.

  16. Shock waves on complex networks

    PubMed Central

    Mones, Enys; Araújo, Nuno A. M.; Vicsek, Tamás; Herrmann, Hans J.

    2014-01-01

    Power grids, road maps, and river streams are examples of infrastructural networks which are highly vulnerable to external perturbations. An abrupt local change of load (voltage, traffic density, or water level) might propagate in a cascading way and affect a significant fraction of the network. Almost discontinuous perturbations can be modeled by shock waves which can eventually interfere constructively and endanger the normal functionality of the infrastructure. We study their dynamics by solving the Burgers equation under random perturbations on several real and artificial directed graphs. Even for graphs with a narrow distribution of node properties (e.g., degree or betweenness), a steady state is reached exhibiting a heterogeneous load distribution, having a difference of one order of magnitude between the highest and average loads. Unexpectedly we find for the European power grid and for finite Watts-Strogatz networks a broad pronounced bimodal distribution for the loads. To identify the most vulnerable nodes, we introduce the concept of node-basin size, a purely topological property which we show to be strongly correlated to the average load of a node. PMID:24821422

  17. Shock waves on complex networks.

    PubMed

    Mones, Enys; Araújo, Nuno A M; Vicsek, Tamás; Herrmann, Hans J

    2014-01-01

    Power grids, road maps, and river streams are examples of infrastructural networks which are highly vulnerable to external perturbations. An abrupt local change of load (voltage, traffic density, or water level) might propagate in a cascading way and affect a significant fraction of the network. Almost discontinuous perturbations can be modeled by shock waves which can eventually interfere constructively and endanger the normal functionality of the infrastructure. We study their dynamics by solving the Burgers equation under random perturbations on several real and artificial directed graphs. Even for graphs with a narrow distribution of node properties (e.g., degree or betweenness), a steady state is reached exhibiting a heterogeneous load distribution, having a difference of one order of magnitude between the highest and average loads. Unexpectedly we find for the European power grid and for finite Watts-Strogatz networks a broad pronounced bimodal distribution for the loads. To identify the most vulnerable nodes, we introduce the concept of node-basin size, a purely topological property which we show to be strongly correlated to the average load of a node. PMID:24821422

  18. The physics of interstellar shock waves

    NASA Technical Reports Server (NTRS)

    Shull, J. Michael; Draine, Bruce T.

    1987-01-01

    This review discusses the observations and theoretical models of interstellar shock waves, in both diffuse cloud and molecular cloud environments. It summarizes the relevant gas dynamics, atomic, molecular and grain processes, radiative transfer, and physics of radiative and magnetic precursors in shock models. It then describes the importance of shocks for observations, diagnostics, and global interstellar dynamics. It concludes with current research problems and data needs for atomic, molecular and grain physics.

  19. Shock compaction of magnet powder using underwater shock wave

    SciTech Connect

    Kubota, Shiro; Fujita, Masahiro; Itoh, Shigeru

    1996-12-31

    In order to get a high plug density (over 90%), the authors tried a direct consolidation of the magnet powder using the converging underwater shock wave created by the underwater explosion of explosives. The processes of the consolidation of the magnet powder were investigated by numerical calculation. They obtained the parameters of the EOS (Petrie-Page model) for Magnet powder using quasi-static loading experiments. Moreover, the characteristics of the shock compaction assembly were also verified.

  20. Shock waves: The Maxwell-Cattaneo case.

    PubMed

    Uribe, F J

    2016-03-01

    Several continuum theories for shock waves give rise to a set of differential equations in which the analysis of the underlying vector field can be done using the tools of the theory of dynamical systems. We illustrate the importance of the divergences associated with the vector field by considering the ideas by Maxwell and Cattaneo and apply them to study shock waves in dilute gases. By comparing the predictions of the Maxwell-Cattaneo equations with shock wave experiments we are lead to the following conclusions: (a) For low compressions (low Mach numbers: M) the results from the Maxwell-Cattaneo equations provide profiles that are in fair agreement with the experiments, (b) as the Mach number is increased we find a range of Mach numbers (1.27≈M_{1}shock wave solutions to the Maxwell-Cattaneo equations cannot be found, and PMID:27078450

  1. Beamwidth measurement of individual lithotripter shock waves

    PubMed Central

    Kreider, Wayne; Bailey, Michael R.; Ketterling, Jeffrey A.

    2009-01-01

    New lithotripters with narrower foci and higher peak pressures than the original Dornier HM3 electrohydraulic lithotripter have proven to be less effective and less safe. Hence, accurate measurements of the focal characteristics of lithotripter shock waves are important. The current technique for measuring beamwidth requires a collection of single-point measurements over multiple shock waves, thereby introducing error as a result of any shock-to-shock variability. This work reports on the construction of a hydrophone array sensor and on array measurements of individual lithotripter shock waves. Beamwidths for an electrohydraulic lithotripter with a broad-focus HM3-style reflector and a narrow-focus modified reflector were measured using both new and worn electrodes as well as two different electrical charging potentials. The array measured the waveform, beamwidth, and focal location of individual shock waves. The HM3-style reflector produced repeatable focal waveforms and beam profiles at an 18 kV charging potential with new and worn electrodes. Corresponding measurements suggest a narrower beamwidth than reported previously from averaged point measurements acquired under the same conditions. In addition, a lack of consistency in the measured beam profiles at 23 kV underscores the value of measuring individual shock waves. PMID:19206897

  2. Ion-acoustic shocks with self-regulated ion reflection and acceleration

    NASA Astrophysics Data System (ADS)

    Malkov, M. A.; Sagdeev, R. Z.; Dudnikova, G. I.; Liseykina, T. V.; Diamond, P. H.; Papadopoulos, K.; Liu, C.-S.; Su, J. J.

    2016-04-01

    An analytic solution describing an ion-acoustic collisionless shock, self-consistently with the evolution of shock-reflected ions, is obtained. The solution extends the classic soliton solution beyond a critical Mach number, where the soliton ceases to exist because of the upstream ion reflection. The reflection transforms the soliton into a shock with a trailing wave and a foot populated by the reflected ions. The solution relates parameters of the entire shock structure, such as the maximum and minimum of the potential in the trailing wave, the height of the foot, as well as the shock Mach number, to the number of reflected ions. This relation is resolvable for any given distribution of the upstream ions. In this paper, we have resolved it for a simple "box" distribution. Two separate models of electron interaction with the shock are considered. The first model corresponds to the standard Boltzmannian electron distribution in which case the critical shock Mach number only insignificantly increases from M ≈1.6 (no ion reflection) to M ≈1.8 (substantial reflection). The second model corresponds to adiabatically trapped electrons. They produce a stronger increase, from M ≈3.1 to M ≈4.5 . The shock foot that is supported by the reflected ions also accelerates them somewhat further. A self-similar foot expansion into the upstream medium is described analytically.

  3. Shock wave sensors: I. Requirements and design.

    PubMed

    Lewin, P A; Schafer, M E

    1991-01-01

    In the last 9 years, extracorporeal shock wave lithotripsy has become one of the preferred procedures for the treatment of urinary and gallbladder calculi. While there is still uncertainty as to the mechanisms of stone fragmentation, current hypotheses suggest that acoustical shock wave parameters such as rise time, peak compressional and rarefactional pressure, and frequency content may all influence the treatment's efficiency. Thus, optimization of lithotripsy treatment needs pressure sensors that can adequately characterize the shock wave field. This article presents and discusses the design of reliable, wideband, quantitative shock wave sensors made of piezoelectric material. The development, design, and performance characteristics of the sensors are presented. Sensor construction details are described, as are the methods used to characterize the sensor's acoustical performance. The key acoustical parameters of the sensor, its frequency response, and directivity pattern are presented; theory indicates that the probes feature uniform sensitivity over the frequency range up to 100 MHz. Preliminary experimental results indicate that piezoelectric polymer sensors made of polyvinylidene fluoride (PVDF) with a low acoustical impedance backing are suitable for lithotripter field measurements. The applicability of sensors based on fiber optics to shock wave measurements is also briefly discussed. In a companion article, shock wave measurement techniques are outlined and selected lithotripter test data are presented. PMID:10149140

  4. Free boundary problems in shock reflection/diffraction and related transonic flow problems

    PubMed Central

    Chen, Gui-Qiang; Feldman, Mikhail

    2015-01-01

    Shock waves are steep wavefronts that are fundamental in nature, especially in high-speed fluid flows. When a shock hits an obstacle, or a flying body meets a shock, shock reflection/diffraction phenomena occur. In this paper, we show how several long-standing shock reflection/diffraction problems can be formulated as free boundary problems, discuss some recent progress in developing mathematical ideas, approaches and techniques for solving these problems, and present some further open problems in this direction. In particular, these shock problems include von Neumann's problem for shock reflection–diffraction by two-dimensional wedges with concave corner, Lighthill's problem for shock diffraction by two-dimensional wedges with convex corner, and Prandtl-Meyer's problem for supersonic flow impinging onto solid wedges, which are also fundamental in the mathematical theory of multidimensional conservation laws. PMID:26261363

  5. Generation of ultrafast optical fiducials for shock-wave experiments

    NASA Astrophysics Data System (ADS)

    Dodson, B. W.

    Recent advances in high time resolution optical diagnostic instrumentation for shock wave experiments in condensed media (especially timing resolved spectroscopy) have resulted in new challenges concerning the timing of such experiments. A technique for detecting the presence of a shock wave through the generation of an optical fiducial signal, which is detected and recorded directly by the optical recording device (typically a streak camera) is presented. This technique, which is based on Stress Induced Defeat of Total Internal Reflection (SIDTIR), requires only simple apparatus and set up, and offers fiducial transition times as short as 50 psec in a reasonable experimental configuration.

  6. Finite Mach number spherical shock wave, application to shock ignition

    SciTech Connect

    Vallet, A.; Ribeyre, X.; Tikhonchuk, V.

    2013-08-15

    A converging and diverging spherical shock wave with a finite initial Mach number M{sub s0} is described by using a perturbative approach over a small parameter M{sub s}{sup −2}. The zeroth order solution is the Guderley's self-similar solution. The first order correction to this solution accounts for the effects of the shock strength. Whereas it was constant in the Guderley's asymptotic solution, the amplification factor of the finite amplitude shock Λ(t)∝dU{sub s}/dR{sub s} now varies in time. The coefficients present in its series form are iteratively calculated so that the solution does not undergo any singular behavior apart from the position of the shock. The analytical form of the corrected solution in the vicinity of singular points provides a better physical understanding of the finite shock Mach number effects. The correction affects mainly the flow density and the pressure after the shock rebound. In application to the shock ignition scheme, it is shown that the ignition criterion is modified by more than 20% if the fuel pressure prior to the final shock is taken into account. A good agreement is obtained with hydrodynamic simulations using a Lagrangian code.

  7. Finite Mach number spherical shock wave, application to shock ignition

    NASA Astrophysics Data System (ADS)

    Vallet, A.; Ribeyre, X.; Tikhonchuk, V.

    2013-08-01

    A converging and diverging spherical shock wave with a finite initial Mach number Ms0 is described by using a perturbative approach over a small parameter Ms-2. The zeroth order solution is the Guderley's self-similar solution. The first order correction to this solution accounts for the effects of the shock strength. Whereas it was constant in the Guderley's asymptotic solution, the amplification factor of the finite amplitude shock Λ(t)∝dUs/dRs now varies in time. The coefficients present in its series form are iteratively calculated so that the solution does not undergo any singular behavior apart from the position of the shock. The analytical form of the corrected solution in the vicinity of singular points provides a better physical understanding of the finite shock Mach number effects. The correction affects mainly the flow density and the pressure after the shock rebound. In application to the shock ignition scheme, it is shown that the ignition criterion is modified by more than 20% if the fuel pressure prior to the final shock is taken into account. A good agreement is obtained with hydrodynamic simulations using a Lagrangian code.

  8. Dynamics of Laser-Driven Shock Waves in Solid Targets

    NASA Astrophysics Data System (ADS)

    Aglitskiy, Y.; Karasik, M.; Velikovich, A. L.; Serlin, V.; Weaver, J.; Schmitt, A. J.; Obenschain, S. P.; Grun, J.; Metzler, N.; Zalesak, S. T.; Gardner, J. H.; Oh, J.; Harding, E. C.

    2009-11-01

    Accurate shock timing is a key issue of both indirect- and direct-drive laser fusions. The experiments on the Nike laser at NRL presented here were made possible by improvements in the imaging capability of our monochromatic x-ray diagnostics based on Bragg reflection from spherically curved crystals. Side-on imaging implemented on Nike makes it possible to observe dynamics of the shock wave and ablation front in laser-driven solid targets. We can choose to observe a sequence of 2D images or a continuous time evolution of an image resolved in one spatial dimension. A sequence of 300 ps snapshots taken using vanadium backlighter at 5.2 keV reveals propagation of a shock wave in a solid plastic target. The shape of the shock wave reflects the intensity distribution in the Nike beam. The streak records with continuous time resolution show the x-t trajectory of a laser-driven shock wave in a 10% solid density DVB foam.

  9. Turbulence in argon shock waves

    NASA Technical Reports Server (NTRS)

    Johnson, J. A., III; Santiago, J. P.; I, L.

    1981-01-01

    Irregular density fluctuations with turbulent-like behaviors are found in ionizing shock fronts produced by an arc-driven shock tube. Electric probes are used as the primary diagnostic. Spectral analyses show statistical patterns which seem frozen-in and characterizable by a dominant mode and its harmonics.

  10. Whistler waves observed upstream from collisionless shocks

    NASA Technical Reports Server (NTRS)

    Fairfield, D. H.

    1973-01-01

    Waves in the frequency range 0.5 - 4 Hz were studied in the region upstream of the earth's bow shock using data from the fluxgate magnetic field experiment on IMP-6. Analysis of 150 examples of these waves during a three month interval indicates that amplitudes are generally less than 1 or 2 gammas and propagation directions generally make angles of between 20 and 40 degrees with the field direction. The waves as measured in the spacecraft frame of reference are either left or right hand polarized with respect to the average field direction. It is concluded that the observed waves are right handed waves in the plasma frame of reference with wavelengths of approximately 100 km propagating upstream in the whistler mode. Doppler shifting reduces the observed frequencies in the spacecraft frame and reverses the observed polarization for those waves propagating more directly upstream. Similar waves are seen ahead of most interplanetary shocks.

  11. Numerical simulation of shock wave diffraction by TVD schemes

    NASA Technical Reports Server (NTRS)

    Young, Victor Y. C.; Yee, H. C.

    1987-01-01

    An upwind total variation diminishing (TVD) scheme and a predictor-corrector symmetric TVD scheme were used to numerically simulate the blast wave diffraction on a stationary object. The objective is to help design an optimum configuration so that lateral motion is minimized and at the same time vortex shedding and flow separation are reduced during a blast wave encounter. Results are presented for a generic configuration for both a coarse grid and a fine grid to illustrate the global and local diffraction flow fields. Numerical experiments for the shock wave reflection on a wedge are also included to validate the current approach. Numerical study indicated that these TVD schemes are more stable and produced higher shock resolution than classical shock capturing methods such as the explicit MacCormack scheme.

  12. Exhaust Nozzle Plume and Shock Wave Interaction

    NASA Technical Reports Server (NTRS)

    Castner, Raymond S.; Elmiligui, Alaa; Cliff, Susan

    2013-01-01

    Fundamental research for sonic boom reduction is needed to quantify the interaction of shock waves generated from the aircraft wing or tail surfaces with the exhaust plume. Both the nozzle exhaust plume shape and the tail shock shape may be affected by an interaction that may alter the vehicle sonic boom signature. The plume and shock interaction was studied using Computational Fluid Dynamics simulation on two types of convergent-divergent nozzles and a simple wedge shock generator. The nozzle plume effects on the lower wedge compression region are evaluated for two- and three-dimensional nozzle plumes. Results show that the compression from the wedge deflects the nozzle plume and shocks form on the deflected lower plume boundary. The sonic boom pressure signature of the wedge is modified by the presence of the plume, and the computational predictions show significant (8 to 15 percent) changes in shock amplitude.

  13. Stishovite: Synthesis by shock wave

    USGS Publications Warehouse

    De Carli, P. S.; Milton, D.J.

    1965-01-01

    Small amounts of stishovite were separated from specimens of explosively shocked sandstones, novaculite, and single-crystal quartz. Estimated peak pressures for the syntheses ranged from 150 to 280 kilobars, and shock temperatures were from 150?? to 900??C. No coesite was detected in any sample. It is suggested that quartz can invert during shock to a short-range-order phase, with sixfold coordination. A small portion of this phase may develop the long-range order of stishovite, and, during the more protracted decrease of the pressure pulse through the stability field of coesite accompanying meteorite crater formation, a portion may invert to coesite.

  14. Oscillations of a standing shock wave generated by the Richtmyer-Meshkov instability

    NASA Astrophysics Data System (ADS)

    Mikaelian, Karnig O.

    2016-07-01

    In a typical Richtmyer-Meshkov experiment a fast moving flat shock strikes a stationary perturbed interface between fluids A and B creating a transmitted and a reflected shock, both of which are perturbed. We propose shock tube experiments in which the reflected shock is stationary in the laboratory. Such a standing perturbed shock undergoes well-known damped oscillations. We present the conditions required for producing such a standing shock wave, which greatly facilitates the measurement of the oscillations and their rate of damping. We define a critical density ratio Rcritical, in terms of the adiabatic indices of the two fluids, and a critical Mach number Mscritical of the incident shock wave, which produces a standing reflected wave. If the initial density ratio R of the two fluids is less than Rcritical then a standing shock wave is possible at Ms=Mscritical . Otherwise a standing shock is not possible and the reflected wave always moves in the direction opposite the incident shock. Examples are given for present-day operating shock tubes with sinusoidal or inclined interfaces. We consider the effect of viscosity, which affects the damping rate of the oscillations. We point out that nonlinear bubble and spike amplitudes depend relatively weakly on the viscosity of the fluids and that the interface area is a better diagnostic.

  15. Oscillations of a standing shock wave generated by the Richtmyer-Meshkov instability

    DOE PAGESBeta

    Mikaelian, Karnig O.

    2016-07-13

    In a typical Richtmyer-Meshkov experiment a fast moving flat shock strikes a stationary perturbed interface between fluids A and B creating a transmitted and a reflected shock, both of which are perturbed. We propose shock tube experiments in which the reflected shock is stationary in the laboratory. Such a standing perturbed shock undergoes well-known damped oscillations. We present the conditions required for producing such a standing shock wave, which greatly facilitates the measurement of the oscillations and their rate of damping. We define a critical density ratio Rcritical, in terms of the adiabatic indices of the two fluids, and amore » critical Mach number Mcriticals of the incident shock wave, which produces a standing reflected wave. If the initial density ratio R of the two fluids is less than Rcritical then a standing shock wave is possible at Ms=Mcriticals. Otherwise a standing shock is not possible and the reflected wave always moves in the direction opposite the incident shock. Examples are given for present-day operating shock tubes with sinusoidal or inclined interfaces. We consider the effect of viscosity, which affects the damping rate of the oscillations. Furthermore, we point out that nonlinear bubble and spike amplitudes depend relatively weakly on the viscosity of the fluids and that the interface area is a better diagnostic.« less

  16. Unsteady relativistic shock-wave diffraction by cylinders and spheres.

    PubMed

    Tsai, I-Nan; Huang, Juan-Chen; Tsai, Shang-Shi; Yang, J Y

    2012-02-01

    The unsteady relativistic shock-wave diffraction patterns generated by a relativistic blast wave impinging on a circular cylinder and a sphere are numerically simulated using some high-resolution relativistic kinetic beam schemes in a general coordinate system for solving the relativistic Euler equations of gas dynamics. The diffraction patterns are followed through about 6 radii of travel of the incident shock past the body. The complete diffraction patterns, including regular reflection, transition from regular to Mach reflection, slip lines, and the complex shock-on-shock interaction at the wake region resulting from the Mach shocks collision behind the body are reported in detail. Computational results of several incident shock Mach numbers covering the near ultrarelativistic limit are studied. Various contours of flow properties including the Lorentz factor and velocity streamline plots are also presented to add a better understanding of the complex diffraction phenomena. The three-dimensional relieving effects of the sphere cases are evident and can be quantitatively evaluated as compared with the corresponding cylinder cases. PMID:22463327

  17. Unsteady relativistic shock-wave diffraction by cylinders and spheres

    NASA Astrophysics Data System (ADS)

    Tsai, I.-Nan; Huang, Juan-Chen; Tsai, Shang-Shi; Yang, J. Y.

    2012-02-01

    The unsteady relativistic shock-wave diffraction patterns generated by a relativistic blast wave impinging on a circular cylinder and a sphere are numerically simulated using some high-resolution relativistic kinetic beam schemes in a general coordinate system for solving the relativistic Euler equations of gas dynamics. The diffraction patterns are followed through about 6 radii of travel of the incident shock past the body. The complete diffraction patterns, including regular reflection, transition from regular to Mach reflection, slip lines, and the complex shock-on-shock interaction at the wake region resulting from the Mach shocks collision behind the body are reported in detail. Computational results of several incident shock Mach numbers covering the near ultrarelativistic limit are studied. Various contours of flow properties including the Lorentz factor and velocity streamline plots are also presented to add a better understanding of the complex diffraction phenomena. The three-dimensional relieving effects of the sphere cases are evident and can be quantitatively evaluated as compared with the corresponding cylinder cases.

  18. Turbulent Water Coupling in Shock Wave Lithotripsy

    PubMed Central

    Lautz, Jaclyn; Sankin, Georgy; Zhong, Pei

    2013-01-01

    Previous studies have demonstrated that stone comminution decreases with increased pulse repetition frequency as a result of bubble proliferation in the cavitation field of a shock wave lithotripter (Pishchalnikov et al., 2011). If cavitation nuclei remain in the propagation path of successive lithotripter pulses, especially in the acoustic coupling cushion of the shock wave source, they will consume part of the incident wave energy, leading to reduced tensile pressure in the focal region and thus lower stone comminution efficiency. We introduce a method to remove cavitation nuclei from the coupling cushion between successive shock exposures using a jet of degassed water. As a result, pre-focal bubble nuclei lifetime quantified by B-mode ultrasound imaging was reduced from 7 s to 0.3 s by a jet with an exit velocity of 62 cm/s. Stone fragmentation (percent mass < 2 mm) after 250 shocks delivered at 1 Hz was enhanced from 22 ± 6% to 33 ± 5% (p = 0.007) in water without interposing tissue mimicking materials. Stone fragmentation after 500 shocks delivered at 2 Hz was increased from 18 ± 6% to 28 ± 8% (p = 0.04) with an interposing tissue phantom of 8 cm thick. These results demonstrate the critical influence of cavitation bubbles in the coupling cushion on stone comminution and suggest a potential strategy to improve the efficacy of contemporary shock wave lithotripters. PMID:23322027

  19. Shock wave interaction with interfaces between materials having different acoustic impedances

    NASA Astrophysics Data System (ADS)

    Hosseini, H.; Moosavi-Nejad, S.; Akiyama, H.; Menezes, V.

    2014-03-01

    We experimentally examined interaction of blast waves with water-air/air-water interfaces through high-speed-real-time visualization and measurement of pressure across the waves. The underwater shock wave, which was expected to reflect totally at the water-air interface, was observed transmitting a shock front to air. Transmission of a blast wave from air to water was also visualized and evaluated. Underwater shock waves are used in several medical/biological procedures, where such unforeseen transmissions can result in detriments. The details provide a guideline to evaluate blast wave transmissions, which can induce tissue and brain injuries. The results explain mechanisms behind blast-induced traumatic brain injury.

  20. Shock waves: The Maxwell-Cattaneo case

    NASA Astrophysics Data System (ADS)

    Uribe, F. J.

    2016-03-01

    Several continuum theories for shock waves give rise to a set of differential equations in which the analysis of the underlying vector field can be done using the tools of the theory of dynamical systems. We illustrate the importance of the divergences associated with the vector field by considering the ideas by Maxwell and Cattaneo and apply them to study shock waves in dilute gases. By comparing the predictions of the Maxwell-Cattaneo equations with shock wave experiments we are lead to the following conclusions: (a) For low compressions (low Mach numbers: M ) the results from the Maxwell-Cattaneo equations provide profiles that are in fair agreement with the experiments, (b) as the Mach number is increased we find a range of Mach numbers (1.27 ≈M1shock wave solutions to the Maxwell-Cattaneo equations cannot be found, and (c) for greater Mach numbers (M >M2) shock wave solutions can be found though they differ significantly from experiments.

  1. Nonplanar Shock Waves in Dusty Plasmas

    SciTech Connect

    Mamun, A. A.; Shukla, P. K.

    2011-11-29

    Nonplanar (viz. cylindrical and spherical) electro-acoustic [dust-ion-acoustic (DIA) and dust-acoustic (DA)] shock waves have been investigated by employing the reductive perturbation method. The dust charge fluctuation (strong correlation among highly charged dust) is the source of dissipation, and is responsible for the formation of the DIA (DA) shock structures. The effects of cylindrical and spherical geometries on the time evolution of DIA and DA shock structures are examined and identified. The combined effects of vortex-like electron distribution and dust charge fluctuation (dust-correlation and effective dust-temperature) on the basic features of nonplanar DIA (DA) shock waves are pinpointed. The implications of our results in laboratory dusty plasma experiments are briefly discussed.

  2. Nonplanar Shock Waves in Dusty Plasmas

    NASA Astrophysics Data System (ADS)

    Mamun, A. A.; Shukla, P. K.

    2011-11-01

    Nonplanar (viz. cylindrical and spherical) electro-acoustic [dust-ion-acoustic (DIA) and dust-acoustic (DA)] shock waves have been investigated by employing the reductive perturbation method. The dust charge fluctuation (strong correlation among highly charged dust) is the source of dissipation, and is responsible for the formation of the DIA (DA) shock structures. The effects of cylindrical and spherical geometries on the time evolution of DIA and DA shock structures are examined and identified. The combined effects of vortex-like electron distribution and dust charge fluctuation (dust-correlation and effective dust-temperature) on the basic features of nonplanar DIA (DA) shock waves are pinpointed. The implications of our results in laboratory dusty plasma experiments are briefly discussed.

  3. Lower hybrid waves at the shock front: a reassessment

    NASA Astrophysics Data System (ADS)

    Walker, S. N.; Balikhin, M. A.; Alleyne, H. St. C. K.; Hobara, Y.; André, M.; Dunlop, M. W.

    2008-03-01

    The primary process occurring at a collisionless shock is the redistribution of the bulk upstream energy into other degrees of freedom. One part of this process results in the acceleration of electrons at the shock front. Accelerated electrons are observed at the terrestrial and other planetary shocks, comets, and their effects are observed in astrophysical phenomena such as supernova remnants and jets in the form of X-ray bremsstrahlung radiation. One of the physical models for electron acceleration at supercritical shocks is based on low-hybrid turbulence due to the presence of reflected ions in the foot region. Since lower hybrid waves propagate almost perpendicular to the magnetic field they can be simultaneously in resonance with both the unmagnetised ions (ω=Vik⊥) and magnetised electrons (ω=Vek||). In this paper, Cluster observations of the electric field are used to study the occurrence of lower hybrid waves in the front of the terrestrial bow shock. It is shown that the lower hybrid waves exist as isolated wave packets. However, the very low level of the observed lower hybrid turbulence is too small to impart significant energisation to the electron population.

  4. A numerical investigation of polygonal converging shock waves

    NASA Astrophysics Data System (ADS)

    Eliasson, Veronica; Henshaw, William D.

    2007-11-01

    Numerical simulations of cylindrically converging shock waves were performed. The converging shocks impinged upon a set of zero to sixteen regularly spaced cylindrical obstacles. For more than two obstacles, the resulting diffracted shock fronts formed polygonal-shaped patterns near the point of focus. For three obstacles, a triangular-shaped shock was observed during the last stages of the focusing process. The triangle was subjected to regular reflection, and thus the shape remained unchanged until it had focused. Guderley's self-similar solution for the radius, R, as a function of time, t, can be expressed as R=ɛ0( tc-t )^α. The self similar exponent, α, was close to the expected value of unity for the triangular case. For the square-shaped shock undergoing Mach reflection, the self-similar exponent was found to be α=0.844, which agrees well with Guderley's solution for cylindrical shocks (α=0.834). Also, the maximum pressure and temperature as a function of number of obstacles were studied. The highest maximum pressure and temperature occurred with no obstacles. This should be expected, since in all other cases, part of the flow is reflected by the obstacles and never reaches the focal point.

  5. Reflection of cylindrical surface waves.

    PubMed

    Gordon, Reuven

    2009-10-12

    The reflection of the radially polarized surface wave on a metal wire at an abrupt end is derived. This theory allows for straightforward calculation of the reflection coefficient, including the phase and the amplitude, which will prove useful to the many applications in nanoplasmonics and terahertz spectroscopy. The theory shows excellent quantitative agreement with past comprehensive numerical simulations for small wires and for predicting the minima in reflection for larger wires. Using this theory, the wavelength dependent reflection is calculated for gold rods of diameter 10 nm, 26 nm and 85 nm, from which the Fabry-Perot resonance wavelengths are found. The Fabry-Perot resonances show good agreement with experimentally measured surface plasmon resonances in nanorods. This demonstrates the predictive ability of the theory for applications involving widely-used nanorods, optical antennas and plasmonic resonators. PMID:20372593

  6. Modification of the edge wave in shock wave lithotripsy

    NASA Astrophysics Data System (ADS)

    Zhou, Yufeng

    2012-10-01

    To reduce the bubble cavitation and the consequent vascular injury of shock wave lithotripsy (SWL), a new method was devised to modify the diffraction wave generated at the aperture of a Dornier HM-3 lithotripter. Subsequently, the duration of the tensile wave was shortened significantly (3.2±0.54 μs vs. 5.83±0.56 μs). However, the amplitude and duration of the compressive wave of LSW between these two groups as well as the -6 dB beam width and the amplitude of the tensile wave are almost unchanged. The suppression on bubble cavitation was confirmed using the passive cavitation technique. At the lithotripter focus, while 30 shocks can cause rupture of blood vessel phantom using the HM-3 lithotripter at 20 kV; no rupture could be found after 300 shocks with the edge extender. On the other hand, after 200 shocks the HM-3 lithotripter at 20 kV can achieve a stone fragmentation of 50.4±2.0% on plaster-of-Paris stone phantom, which is comparable to that of using the edge extender (46.8±4.1%, p=0.005). Altogether, the modification on the diffraction wave at the lithotripter aperture can significantly reduce the bubble cavitation activities. As a result, potential for vessel rupture in shock wave lithotripsy is expected.

  7. Magnetoacoustic shock waves in dissipative degenerate plasmas

    SciTech Connect

    Hussain, S.; Mahmood, S.

    2011-11-15

    Quantum magnetoacoustic shock waves are studied in homogenous, magnetized, dissipative dense electron-ion plasma by using two fluid quantum magneto-hydrodynamic (QMHD) model. The weak dissipation effects in the system are taken into account through kinematic viscosity of the ions. The reductive perturbation method is employed to derive Korteweg-de Vries Burgers (KdVB) equation for magnetoacoustic wave propagating in the perpendicular direction to the external magnetic field in dense plasmas. The strength of magnetoacoustic shock is investigated with the variations in plasma density, magnetic field intensity, and ion kinematic viscosity of dense plasma system. The necessary condition for the existence of monotonic and oscillatory shock waves is also discussed. The numerical results are presented for illustration by using the data of astrophysical dense plasma situations such as neutron stars exist in the literature.

  8. Laser Light Scattering by Shock Waves

    NASA Technical Reports Server (NTRS)

    Panda, J.; Adamovsky, G.

    1995-01-01

    Scattering of coherent light as it propagates parallel to a shock wave, formed in front of a bluff cylindrical body placed in a supersonic stream, is studied experimentally and numerically. Two incident optical fields are considered. First, a large diameter collimated beam is allowed to pass through the shock containing flow. The light intensity distribution in the resultant shadowgraph image, measured by a low light CCD camera, shows well-defined fringes upstream and downstream of the shadow cast by the shock. In the second situation, a narrow laser beam is brought to a grazing incidence on the shock and the scattered light, which appears as a diverging sheet from the point of interaction, is visualized and measured on a screen placed normal to the laser path. Experiments are conducted on shocks formed at various free-stream Mach numbers, M, and total pressures, P(sub 0). It is found that the widths of the shock shadows in a shadowgraph image become independent of M and P(sub 0) when plotted against the jump in the refractive index, (Delta)n, created across the shock. The total scattered light measured from the narrow laser beam and shock interaction also follows the same trend. In the numerical part of the study, the shock is assumed to be a 'phase object', which introduces phase difference between the upstream and downstream propagating parts of the light disturbances. For a given shape and (Delta)n of the bow shock the phase and amplitude modulations are first calculated by ray tracing. The wave front is then propagated to the screen using the Fresnet diffraction equation. The calculated intensity distribution, for both of the incident optical fields, shows good agreement with the experimental data.

  9. Wave reflections from duct terminations.

    PubMed

    Selamet, A; Ji, Z L; Kach, R A

    2001-04-01

    The reflection coefficients and inertial end corrections of several duct terminations, including finite length duct extensions perpendicular to an infinite wall, as well as at a number of angles, curved interface surfaces, and annular cavities, are determined and analyzed in the absence of flow by employing the boundary element method. Predictions for the classical unflanged and flanged circular ducts show good agreement with analytical and computational results available in the literature. The predictions for curved interface surfaces (bellmouth or horn) are also consistent with the available experimental data. In view of its high reflection coefficient, the duct termination with an annular cavity may be suggested for the suppression of noise radiation in a specific frequency band or for an effective wave reflection from the termination. PMID:11325101

  10. Shock-wave properties of brittle solids

    SciTech Connect

    Grady, D.E.

    1995-10-01

    Extensive experimental investigation in the form of large-amplitude, nonlinear wave-profile measurements which manifest the shock strength and equation-of-state properties of brittle solids has been performed. Brittle materials for which a base of dynamic property data is available include Al{sub 2}O{sub 3}, AlN, B{sub 4}C, CaCO{sub 3}, SiC, Si{sub 3}N{sub 4}, SiO{sub 2} (quartz and glass), TiB{sub 2}, WC and ZrO{sub 2}. Planar impact methods and velocity interferometry diagnostics have been used exclusively to provide the high-resolution shock-profile data. These wave-profile data are providing engineering dynamic strength and equation-of-state properties as well as controlled, shock-induced motion histories for the validation of theoretical and Computational models. Of equal importance, such data are providing a window into the physics of a newly emerging understanding of the compression and deformation behavior of high-strength brittle solids. When considered along with a rich assortment of strength and deformation data in the literature, a systematic assessment of this shock-wave data lends strong support for failure waves and concomitant high-confinement dilatancy as a general mechanism of inelastic deformation in the shock compression of ceramics. Phase transformation in selected brittle solids appears to be a critical state phenomenon strongly controlled by kinetics. The risetime and structure of deformation shock waves in brittle solids are controlled by viscous effects which at present are still poorly understood. The shockwave data also suggest that both crystalline plasticity and brittle fracture may play important and interconnected roles in the dynamic failure process.

  11. Plasma waves downstream of weak collisionless shocks

    NASA Technical Reports Server (NTRS)

    Coroniti, F. V.; Greenstadt, E. W.; Moses, S. L.; Smith, E. J.; Tsurutani, B. T.

    1993-01-01

    In September 1983 the International Sun Earth Explorer 3 (ISEE 3) International Cometary Explorer (ICE) spacecraft made a long traversal of the distant dawnside flank region of the Earth's magnetosphere and had many encounters with the low Mach number bow shock. These weak shocks excite plasma wave electric field turbulence with amplitudes comparable to those detected in the much stronger bow shock near the nose region. Downstream of quasi-perpendicular (quasi-parallel) shocks, the E field spectra exhibit a strong peak (plateau) at midfrequencies (1 - 3 kHz); the plateau shape is produced by a low-frequency (100 - 300 Hz) emission which is more intense behind downstream of two quasi-perpendicular shocks show that the low frequency signals are polarized parallel to the magnetic field, whereas the midfrequency emissions are unpolarized or only weakly polarized. A new high frequency (10 - 30 kHz) emission which is above the maximum Doppler shift exhibit a distinct peak at high frequencies; this peak is often blurred by the large amplitude fluctuations of the midfrequency waves. The high-frequency component is strongly polarized along the magnetic field and varies independently of the lower-frequency waves.

  12. Magnetically accelerated foils for shock wave experiments

    NASA Astrophysics Data System (ADS)

    Neff, Stephan; Ford, Jessica; Martinez, David; Plechaty, Christopher; Wright, Sandra; Presura, Radu

    2008-04-01

    The interaction of shock waves with inhomogeneous media is important in many astrophysical problems, e.g. the role of shock compression in star formation. Using scaled experiments with inhomogeneous foam targets makes it possible to study relevant physics in the laboratory, to better understand the mechanisms of shock compression and to benchmark astrophysical simulation codes. Experiments with flyer-generated shock waves have been performed on the Z machine in Sandia. The Zebra accelerator at the Nevada Terawatt Facility (NTF) allows for complementary experiments with high repetition rate. First experiments on Zebra demonstrated flyer acceleration to sufficiently high velocities (around 2 km/s) and that laser shadowgraphy can image sound fronts in transparent targets. Based on this, we designed an optimized setup to improve the flyer parameters (higher speed and mass) to create shock waves in transparent media. Once x-ray backlighting with the Leopard laser at NTF is operational, we will switch to foam targets with parameters relevant for laboratory astrophysics.

  13. Optical shock waves in silica aerogel.

    PubMed

    Gentilini, S; Ghajeri, F; Ghofraniha, N; Di Falco, A; Conti, C

    2014-01-27

    Silica aerogels are materials well suited for high power nonlinear optical applications. In such regime, the non-trivial thermal properties may give rise to the generation of optical shock waves, which are also affected by the structural disorder due to the porous solid-state gel. Here we report on an experimental investigation in terms of beam waist and input power, and identify various regimes of the generation of wave-breaking phenomena in silica aerogels. PMID:24515173

  14. Shock wave amplification by fabric materials

    NASA Astrophysics Data System (ADS)

    Thom, C. G.; Cronin, D. S.

    2009-04-01

    It has been shown that, when exposed to air shock waves, soft materials such as fabrics can lead to amplification of the peak pressure measured on a reflecting surface behind the fabric. This occurs for a wide range of fabric configurations, including those used in soft-ballistic protection. The goal of this study was to validate a numerical model to develop an improved understanding of this phenomenon and investigate different fabric parameters, including density, permeability and standoff, and their influence on blast amplification. The investigation of fabric parameters was carried out using numerical simulations in an explicit finite element code with coupled fluid-structure interaction. The benefit of this method was the ability to isolate individual parameters. The model predicted similar trends to existing experimental data, though the numerically predicted peak pressures were consistently higher than the experimental values. The parametric study showed that low permeability fabrics result in the highest pressure amplifications. At areal densities on the order 100 g/m2, typical of single layer fabrics, amplification also increased with areal density for low permeability materials.

  15. Chromospheric heating by acoustic shock waves

    NASA Technical Reports Server (NTRS)

    Jordan, Stuart D.

    1993-01-01

    Work by Anderson & Athay (1989) suggests that the mechanical energy required to heat the quiet solar chromosphere might be due to the dissipation of weak acoustic shocks. The calculations reported here demonstrate that a simple picture of chromospheric shock heating by acoustic waves propagating upward through a model solar atmosphere, free of both magnetic fields and local inhomogeneities, cannot reproduce their chromospheric model. The primary reason is the tendency for vertically propagating acoustic waves in the range of allowed periods to dissipate too low in the atmosphere, providing insufficient residual energy for the middle chromosphere. The effect of diverging magnetic fields and the corresponding expanding acoustic wavefronts on the mechanical dissipation length is then discussed as a means of preserving a quasi-acoustic heating hypothesis. It is argued that this effect, in a canopy that overlies the low chromosphere, might preserve the acoustic shock hypothesis consistent with the chromospheric radiation losses computed by Anderson & Athay.

  16. Magnetically accelerated foils for shock wave experiments

    NASA Astrophysics Data System (ADS)

    Neff, S.; Ford, J.; Wright, S.; Martinez, D.; Plechaty, C.; Presura, R.

    2009-08-01

    Many astrophysical phenomena involve the interaction of a shock wave with an inhomogeneous background medium. Using scaled experiments with inhomogeneous foam targets makes it possible to study relevant physics in the laboratory to better understand the mechanisms of shock compression and to benchmark astrophysical simulation codes. First experiments on Zebra at the Nevada Terawatt Facility (NTF) have demonstrated flyer acceleration to sufficiently high velocities (up to 5 km/s) and that laser shadowgraphy can image sound fronts in transparent targets. Based on this, we designed an optimized setup to improve the flyer parameters (higher speed and mass) to create shock waves in transparent media. Once x-ray backlighting with the Leopard laser at NTF is operational, we will switch to foam targets with parameters relevant for laboratory astrophysics.

  17. International Shock-Wave Database: Current Status

    NASA Astrophysics Data System (ADS)

    Levashov, Pavel

    2013-06-01

    Shock-wave and related dynamic material response data serve for calibrating, validating, and improving material models over very broad regions of the pressure-temperature-density phase space. Since the middle of the 20th century vast amount of shock-wave experimental information has been obtained. To systemize it a number of compendiums of shock-wave data has been issued by LLNL, LANL (USA), CEA (France), IPCP and VNIIEF (Russia). In mid-90th the drawbacks of the paper handbooks became obvious, so the first version of the online shock-wave database appeared in 1997 (http://www.ficp.ac.ru/rusbank). It includes approximately 20000 experimental points on shock compression, adiabatic expansion, measurements of sound velocity behind the shock front and free-surface-velocity for more than 650 substances. This is still a useful tool for the shock-wave community, but it has a number of serious disadvantages which can't be easily eliminated: (i) very simple data format for points and references; (ii) minimalistic user interface for data addition; (iii) absence of history of changes; (iv) bad feedback from users. The new International Shock-Wave database (ISWdb) is intended to solve these and some other problems. The ISWdb project objectives are: (i) to develop a database on thermodynamic and mechanical properties of materials under conditions of shock-wave and other dynamic loadings, selected related quantities of interest, and the meta-data that describes the provenance of the measurements and material models; and (ii) to make this database available internationally through the Internet, in an interactive form. The development and operation of the ISWdb is guided by an advisory committee. The database will be installed on two mirrored web-servers, one in Russia and the other in USA (currently only one server is available). The database provides access to original experimental data on shock compression, non-shock dynamic loadings, isentropic expansion, measurements of sound

  18. Shock Wave Dynamics in Weakly Ionized Gases

    NASA Technical Reports Server (NTRS)

    Johnson, Joseph A., III

    1998-01-01

    We have begun a comprehensive series of analyses and experiments to study the basic problem of shock wave dynamics in ionized media. Our objective is to isolate the mechanisms that are responsible for the decrease in the shock amplitude and also to determine the relevant plasma parameters that will be required for a drag reduction scheme in an actual high altitude hypersonic flight. Specifically, we have initiated a program of analyses and measurements with the objective of (i) fully characterizing the propagation dynamics in plasmas formed in gases of aerodynamic interest, (ii) isolating the mechanisms responsible for the decreased shock strength and increased shock velocity, (iii) extrapolating the laboratory observations to the technology of supersonic flight.

  19. Colliding electromagnetic shock waves in general relativity

    SciTech Connect

    Halilsoy, M.

    1988-04-15

    We derive a new, exact solution for the Einstein-Maxwell equations that describes the collision (interaction) of two arbitrarily polarized electromagnetic shock waves. In the limit that the polarization angle vanishes, our solution reduces to the Bell-Szekeres solution.

  20. Uncovering the Secret of Shock Wave Lithotripsy

    NASA Astrophysics Data System (ADS)

    Zhong, P.

    Shock wave lithotripsy (SWL) is an engineering innovation that has revolutionized the treatment of kidney stone disease since the early 1980s [1] - [3]. Today, SWL is the first-line therapy for millions of patients worldwide with renal and upper urinary stones [3, 4].

  1. Shock wave absorber having a deformable liner

    DOEpatents

    Youngdahl, C.K.; Wiedermann, A.H.; Shin, Y.W.; Kot, C.A.; Ockert, C.E.

    1983-08-26

    This invention discloses a shock wave absorber for a piping system carrying liquid. The absorber has a plastically deformable liner defining the normal flow boundary for an axial segment of the piping system, and a nondeformable housing is spaced outwardly from the liner so as to define a gas-tight space therebetween. The flow capacity of the liner generally corresponds to the flow capacity of the piping system line, but the liner has a noncircular cross section and extends axially of the piping system line a distance between one and twenty times the diameter thereof. Gas pressurizes the gas-tight space equal to the normal liquid pressure in the piping system. The liner has sufficient structural capacity to withstand between one and one-half and two times this normal liquid pressures; but at greater pressures it begins to plastically deform initially with respect to shape to a more circular cross section, and then with respect to material extension by circumferentially stretching the wall of the liner. A high energy shock wave passing through the liner thus plastically deforms the liner radially into the gas space and progressively also as needed in the axial direction of the shock wave to minimize transmission of the shock wave beyond the absorber.

  2. Density Shock Waves in Confined Microswimmers

    NASA Astrophysics Data System (ADS)

    Tsang, Alan Cheng Hou; Kanso, Eva

    2016-01-01

    Motile and driven particles confined in microfluidic channels exhibit interesting emergent behavior, from propagating density bands to density shock waves. A deeper understanding of the physical mechanisms responsible for these emergent structures is relevant to a number of physical and biomedical applications. Here, we study the formation of density shock waves in the context of an idealized model of microswimmers confined in a narrow channel and subject to a uniform external flow. Interestingly, these density shock waves exhibit a transition from "subsonic" with compression at the back to "supersonic" with compression at the front of the population as the intensity of the external flow increases. This behavior is the result of a nontrivial interplay between hydrodynamic interactions and geometric confinement, and it is confirmed by a novel quasilinear wave model that properly captures the dependence of the shock formation on the external flow. These findings can be used to guide the development of novel mechanisms for controlling the emergent density distribution and the average population speed, with potentially profound implications on various processes in industry and biotechnology, such as the transport and sorting of cells in flow channels.

  3. Density Shock Waves in Confined Microswimmers.

    PubMed

    Tsang, Alan Cheng Hou; Kanso, Eva

    2016-01-29

    Motile and driven particles confined in microfluidic channels exhibit interesting emergent behavior, from propagating density bands to density shock waves. A deeper understanding of the physical mechanisms responsible for these emergent structures is relevant to a number of physical and biomedical applications. Here, we study the formation of density shock waves in the context of an idealized model of microswimmers confined in a narrow channel and subject to a uniform external flow. Interestingly, these density shock waves exhibit a transition from "subsonic" with compression at the back to "supersonic" with compression at the front of the population as the intensity of the external flow increases. This behavior is the result of a nontrivial interplay between hydrodynamic interactions and geometric confinement, and it is confirmed by a novel quasilinear wave model that properly captures the dependence of the shock formation on the external flow. These findings can be used to guide the development of novel mechanisms for controlling the emergent density distribution and the average population speed, with potentially profound implications on various processes in industry and biotechnology, such as the transport and sorting of cells in flow channels. PMID:26871357

  4. 21 CFR 876.5990 - Extracorporeal shock wave lithotripter.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... focuses ultrasonic shock waves into the body to noninvasively fragment urinary calculi within the kidney... Notifications (510(k)'s) for Extracorporeal Shock Wave Lithotripters Indicated for the Fragmentation of...

  5. 21 CFR 876.5990 - Extracorporeal shock wave lithotripter.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... focuses ultrasonic shock waves into the body to noninvasively fragment urinary calculi within the kidney... Notifications (510(k)'s) for Extracorporeal Shock Wave Lithotripters Indicated for the Fragmentation of...

  6. 21 CFR 876.5990 - Extracorporeal shock wave lithotripter.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... focuses ultrasonic shock waves into the body to noninvasively fragment urinary calculi within the kidney... Notifications (510(k)'s) for Extracorporeal Shock Wave Lithotripters Indicated for the Fragmentation of...

  7. 21 CFR 876.5990 - Extracorporeal shock wave lithotripter.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... focuses ultrasonic shock waves into the body to noninvasively fragment urinary calculi within the kidney... Notifications (510(k)'s) for Extracorporeal Shock Wave Lithotripters Indicated for the Fragmentation of...

  8. 21 CFR 876.5990 - Extracorporeal shock wave lithotripter.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... focuses ultrasonic shock waves into the body to noninvasively fragment urinary calculi within the kidney... Notifications (510(k)'s) for Extracorporeal Shock Wave Lithotripters Indicated for the Fragmentation of...

  9. Shock wave propagation in glow discharges

    NASA Astrophysics Data System (ADS)

    Ganguly, B. N.

    1998-10-01

    The modification of acoustic shock wave propagation characteristics in a 25 cm long positive column low pressure (10 to 50 Torr), low current density (2 to 10 mA/cm^2) argon and N2 dc discharges have been measured by laser beam deflection technique. The simultaneous multi point shock velocity, dispersion and damping have been measured both inside and outside the glow discharge region. The local shock velocity is found to increase with the increased propagation path length through the discharge; for Mach number greater than 1.7 the upstream velocity exceeded the downstream velocity in contrast to the opposite behavior in neutral gas. The damping and dispersion are also dependent on the propagation distance. The recovery of the shock dispersion and damping in the post discharge region, for a given discharge condition, are functions of the initial Mach number. The optical measurement of the wall and the gas (rotational) temperatures suggest the observed shock features can not be solely explained by the gas heating in a self sustained discharge. The results are similar for both Ar and N2 discharges showing that vibrational excitation and relaxation are not essential^1. The explanation of the observed weak shock propagation properties in a glow discharge appears to require long range cooperative interactions that enhance heavy particle collisional energy transfer rates for the measured discharge conditions. Unlike collisional shock wave propagation in highly ionized plasmas^2,3, the exact energy coupling mechanism between the nonequilibrium weakly ionized plasma and shock is not understood. 1. A.I. Osipov and A.V. Uvarov, Sov. Phys. Usp. 35, 903 (1992) and other references there in. 2. M. Casanova, O. Larroche and J-P Matte, Phys. Rev. Lett. 67, 2143 (1991). 3. M.C.M. van de Sanden, R. van den Bercken and D.C. Schram, Plasma Sources Sci.Technol. 3, 511 (1994).

  10. Chirped pulse reflectivity in laser driven shock experiments

    NASA Astrophysics Data System (ADS)

    Benuzzi, Alessandra; Koenig, Michel; Faral, Bernard; Batani, Dimitri; Scianitti, Francesca; di Santo, Domenico; Hall, Tom

    1998-11-01

    We performed an experiment based on using two pulses delivered by the 100 TW LULI laser. The first one is an uncompressed (FWHM =89 600 ps) chirped main pulse generating a shock wave in a CH-Al target coated into 2 mm fused quartz. The target rear side emissivity was recorded by a visible streak camera in order to check the shock uniformity. The second one is a partially compressed (FWHM =89 100 ps) chirped probe pulse which irradiates the rear face of the target (the quartz side). We measured on the same laser shot a)the chirped pulse reflectometry(1) which allowed us to obtain a very high temporal resolution, thus a good precision in the shock breakout time determination b) the reflected probe phase change as a function of time using the frequency domain interferometry technique(2). Such measurement allowed us to deduce the interface Al-quartz displacement velocity which yields information on preheating effects and on fluid velocity. [1] D. M. Gold, A. Sullivan, R. Sheperd, J. Dunn & R. Stewart, Proceedings of 26th Annual Anomalous Absorption Conference, Fairbanks, Alaska (1996). [2] J. P. Geindre, P. Audebert, A. Rousse, F. Falli=E8s, J. C. Gauthier, A. Mysyrowicz, A. D. Santos, G. Hammoniaux & A. Antonetti, Optics Lett. 19, 1997 (1994).

  11. Shock wave generated by high-energy electric spark discharge

    NASA Astrophysics Data System (ADS)

    Liu, Qingming; Zhang, Yunming

    2014-10-01

    Shock wave generated by electric spark discharge was studied experimentally and the shock wave energy was evaluated in this paper. A pressure measurement system was established to study the pressure field of the electric spark discharge process. A series of electric spark discharge experiments were carried out and the energy of the electric spark used in present study was in the range of 10 J, 100 J, and 1000 J, respectively. The shock wave energy released from the electric spark discharge process was calculated by using the overpressure values at different measurement points near the electric spark discharge center. The good consistency of shock wave energies calculated by pressure histories at different measuring points in the same electric spark discharge experiment illustrates the applicability of the weak shock wave theory in calculating the energy of shock wave induced by electric spark discharge process. The result showed that shock wave formed at the initial stage of electric spark discharge process, and the shock wave energy is only a little part of electric spark energy. From the analysis of the shock wave energy and electric spark energy, a good linear relationship between shock wave energy and electric spark energy was established, which make it possible to calculate shock wave energy by measuring characteristic parameters of electric spark discharge process instead of shock wave. So, the initiation energy of direct initiation of detonation can be determined easily by measuring the parameters of electric spark discharge process.

  12. Analysis of gas flow evolution and shock wave decay in detonation thermal spraying systems

    NASA Astrophysics Data System (ADS)

    Ramadan, K.; Butler, P. Barry

    2004-06-01

    The reactive Euler equations with variable gas properties are solved in both axisymmetric and plane two-dimensional flows to analyze the gas flow evolution, shock wave decay, and shock reflections in pulsed detonation thermal spraying (PDTS) systems. The gas phase governing equations are numerically solved using a high-resolution shock capturing numerical method. Expansion-compression waves are formed upon external gas expansion and persist for a long time (on the time scale of a PDTS cycle) with wide fluctuations in the gas velocity and temperature. The results show that the reflected shock wave from the substrate dies out extremely fast that micron-sized particles used in PDTS do not encounter these transients. The external shock wave decay is also analyzed for different reactive mixtures and flow geometries and is related to the truncation of the computational domain and the implementation of numerical boundary conditions at the open end boundaries.

  13. Tailoring the Blast Exposure Conditions in the Shock Tube for Generating Pure, Primary Shock Waves: The End Plate Facilitates Elimination of Secondary Loading of the Specimen.

    PubMed

    Kuriakose, Matthew; Skotak, Maciej; Misistia, Anthony; Kahali, Sudeepto; Sundaramurthy, Aravind; Chandra, Namas

    2016-01-01

    The end plate mounted at the mouth of the shock tube is a versatile and effective implement to control and mitigate the end effects. We have performed a series of measurements of incident shock wave velocities and overpressures followed by quantification of impulse values (integral of pressure in time domain) for four different end plate configurations (0.625, 2, 4 inches, and an open end). Shock wave characteristics were monitored by high response rate pressure sensors allocated in six positions along the length of 6 meters long 229 mm square cross section shock tube. Tests were performed at three shock wave intensities, which was controlled by varying the Mylar membrane thickness (0.02, 0.04 and 0.06 inch). The end reflector plate installed at the exit of the shock tube allows precise control over the intensity of reflected waves penetrating into the shock tube. At the optimized distance of the tube to end plate gap the secondary waves were entirely eliminated from the test section, which was confirmed by pressure sensor at T4 location. This is pronounced finding for implementation of pure primary blast wave animal model. These data also suggest only deep in the shock tube experimental conditions allow exposure to a single shock wave free of artifacts. Our results provide detailed insight into spatiotemporal dynamics of shock waves with Friedlander waveform generated using helium as a driver gas and propagating in the air inside medium sized tube. Diffusion of driver gas (helium) inside the shock tube was responsible for velocity increase of reflected shock waves. Numerical simulations combined with experimental data suggest the shock wave attenuation mechanism is simply the expansion of the internal pressure. In the absence of any other postulated shock wave decay mechanisms, which were not implemented in the model the agreement between theory and experimental data is excellent. PMID:27603017

  14. Whistler waves observed upstream from collisionless shocks

    NASA Technical Reports Server (NTRS)

    Fairfield, D. H.

    1974-01-01

    Waves in the frequency range 0.5-4. Hz have been studied in the region upstream of the earth's bow shock with data from the flux-gate magnetic field experiment on Imp 6. Such waves are invariably detected adjacent to the shock, persisting upstream for intervals often less than a minute but occasionally of the order of many hours. Analysis of 150 examples of these waves during a 3-month interval indicates that propagation directions generally make angles of between 20 and 40 deg with the field direction. The waves as measured in the spacecraft frame of reference are either left- or right-hand-polarized with respect to the average field direction. The left-handed waves generally have lower frequencies than the right-handed waves, and the left-handed frequencies never exceed 2.5 Hz. The measured sense of polarization is found to depend on the propagation direction (or alternatively, the field direction) relative to the solar wind direction.

  15. Resonant wavepackets and shock waves in an atomtronic SQUID

    NASA Astrophysics Data System (ADS)

    Wang, Yi-Hsieh; Kumar, A.; Jendrzejewski, F.; Wilson, Ryan M.; Edwards, Mark; Eckel, S.; Campbell, G. K.; Clark, Charles W.

    The fundamental dynamics of ultracold atomtronic devices are reflected in their phonon modes of excitation. We probe such a spectrum by applying a harmonically driven potential barrier to a 23Na Bose-Einstein condensate in a ring-shaped trap. This perturbation excites phonon wavepackets. When excited resonantly, these wavepackets display a regular periodic structure. The resonant frequencies depend upon the particular configuration of the barrier, but are commensurate with the orbital frequency of a Bogoliubov sound wave traveling around the ring. Energy transfer to the condensate over many cycles of the periodic wavepacket motion causes enhanced atom loss from the trap at resonant frequencies. Solutions of the time-dependent Gross-Pitaevskii equation exhibit quantitative agreement with the experimental data. We also observe the generation of supersonic shock waves under conditions of strong excitation, and collisions of two shock wavepackets. Work supported by the U. S. Army Research Office Atomtronics MURI program.

  16. Stability of spherical converging shock wave

    SciTech Connect

    Murakami, M.; Sanz, J.; Iwamoto, Y.

    2015-07-15

    Based on Guderley's self-similar solution, stability of spherical converging shock wave is studied. A rigorous linear perturbation theory is developed, in which the growth rate of perturbation is given as a function of the spherical harmonic number ℓ and the specific heats ratio γ. Numerical calculation reveals the existence of a γ-dependent cut-off mode number ℓ{sub c}, such that all the eigenmode perturbations for ℓ > ℓ{sub c} are smeared out as the shock wave converges at the center. The analysis is applied to partially spherical geometries to give significant implication for different ignition schemes of inertial confinement fusion. Two-dimensional hydrodynamic simulations are performed to verify the theory.

  17. Stability of spherical converging shock wave

    NASA Astrophysics Data System (ADS)

    Murakami, M.; Sanz, J.; Iwamoto, Y.

    2015-07-01

    Based on Guderley's self-similar solution, stability of spherical converging shock wave is studied. A rigorous linear perturbation theory is developed, in which the growth rate of perturbation is given as a function of the spherical harmonic number ℓ and the specific heats ratio γ. Numerical calculation reveals the existence of a γ-dependent cut-off mode number ℓc, such that all the eigenmode perturbations for ℓ > ℓc are smeared out as the shock wave converges at the center. The analysis is applied to partially spherical geometries to give significant implication for different ignition schemes of inertial confinement fusion. Two-dimensional hydrodynamic simulations are performed to verify the theory.

  18. Optimizing Shock Wave Lithotripsy: A Comprehensive Review

    PubMed Central

    McClain, Paul D; Lange, Jessica N; Assimos, Dean G

    2013-01-01

    Shock wave lithotripsy is a commonly used procedure for eradicating upper urinary tract stones in patients who require treatment. A number of methods have been proposed to improve the results of this procedure, including proper patient selection, modifications in technique, adjunctive therapy to facilitate elimination of fragments, and changes in lithotripter design. This article assesses the utility of these measures through an analysis of contemporary literature. PMID:24082843

  19. Scattering of shock waves in QCD

    SciTech Connect

    Ian Balitsky

    2004-09-01

    The cross section of heavy-ion collisions is represented as a double functional integral with the saddle point being the classical solution of the Yang-Mills equations with boundary conditions/sources in the form of two shock waves corresponding to the two colliding ions. I develop the expansion of this classical solution in powers of the commutator of the Wilson lines describing the colliding particles and calculate the first two terms of the expansion.

  20. Quartz structure transformation under a shock wave

    NASA Astrophysics Data System (ADS)

    Vettegren', V. I.; Kuksenko, V. S.; Shcherbakov, I. P.; Mamalimov, R. I.

    2015-12-01

    The structure of a fragment formed after quartz single-crystal fracture under a shock wave has been studied using the Fourier transform infrared spectroscopy (FTIR) method. The wave is initiated by electrical breakdown of air in a hole within the single crystal. It has been found that a layer ~0.15 μm thick consisting of "diaplectic glass," i.e., quartz with a strongly distorted lattice, is formed on the fragment surface. A layer 2 μm thick with a compressed quartz lattice is located under it.

  1. Ionospheric shock waves triggered by rockets

    NASA Astrophysics Data System (ADS)

    Lin, C. H.; Lin, J. T.; Chen, C. H.; Liu, J. Y.; Sun, Y. Y.; Kakinami, Y.; Matsumura, M.; Chen, W. H.; Liu, H.; Rau, R. J.

    2014-09-01

    This paper presents a two-dimensional structure of the shock wave signatures in ionospheric electron density resulting from a rocket transit using the rate of change of the total electron content (TEC) derived from ground-based GPS receivers around Japan and Taiwan for the first time. From the TEC maps constructed for the 2009 North Korea (NK) Taepodong-2 and 2013 South Korea (SK) Korea Space Launch Vehicle-II (KSLV-II) rocket launches, features of the V-shaped shock wave fronts in TEC perturbations are prominently seen. These fronts, with periods of 100-600 s, produced by the propulsive blasts of the rockets appear immediately and then propagate perpendicularly outward from the rocket trajectory with supersonic velocities between 800-1200 m s-1 for both events. Additionally, clear rocket exhaust depletions of TECs are seen along the trajectory and are deflected by the background thermospheric neutral wind. Twenty minutes after the rocket transits, delayed electron density perturbation waves propagating along the bow wave direction appear with phase velocities of 800-1200 m s-1. According to their propagation character, these delayed waves may be generated by rocket exhaust plumes at earlier rocket locations at lower altitudes.

  2. Shock Waves and Commutation Speed of Memristors

    NASA Astrophysics Data System (ADS)

    Tang, Shao; Tesler, Federico; Marlasca, Fernando Gomez; Levy, Pablo; Dobrosavljević, V.; Rozenberg, Marcelo

    2016-01-01

    Progress of silicon-based technology is nearing its physical limit, as the minimum feature size of components is reaching a mere 10 nm. The resistive switching behavior of transition metal oxides and the associated memristor device is emerging as a competitive technology for next-generation electronics. Significant progress has already been made in the past decade, and devices are beginning to hit the market; however, this progress has mainly been the result of empirical trial and error. Hence, gaining theoretical insight is of the essence. In the present work, we report the striking result of a connection between the resistive switching and shock-wave formation, a classic topic of nonlinear dynamics. We argue that the profile of oxygen vacancies that migrate during the commutation forms a shock wave that propagates through a highly resistive region of the device. We validate the scenario by means of model simulations and experiments in a manganese-oxide-based memristor device, and we extend our theory to the case of binary oxides. The shock-wave scenario brings unprecedented physical insight and enables us to rationalize the process of oxygen-vacancy-driven resistive change with direct implications for a key technological aspect—the commutation speed.

  3. Turbulent magnetized plasmas from ionizing shock waves

    NASA Astrophysics Data System (ADS)

    Liang, Zuohua

    Turbulent argon plasmas produced behind hypersonic shock waves (10 less than M less than 60) are studied in the presence of weak magnetic fields at various strengths between 0 and 600 gauss, parallel and antiparallel to the shock tube's axis. The experiment is performed in a cylindrical arc discharge shock tube of 5 cm diameter and 210 cm overall length. Laser induced fluorescence and an electric probe are used as diagnostics of the ion density. Turbulent fluctuations behind the shock front are observed which persist for a time in the order of 10 msec. Using standard turbulent and chaotic analytical procedures, the influence of the magnetic field on the characterizing parameters is determined under circumstances of changing Mach number and pressure. These parameters include spectral index, correlation time scales, turbulent intensity and chaotic dimensionality. The parameters of turbulence obtained from the two diagnostics are quite consistent. Fluctuation power spectra follow a P approx. f(sup -n) behavior with 1.3 less than n less than 2.8; this agrees with theoretical predictions as well as the results of other investigators. An increasing magnetic field increases the characterizing correlation time, the turbulent intensity, and the chaotic dimension but decreases the small correlation time. Therefore the magnetic field decreases the order (increases the dimensionality) in the turbulent plasma, independent of the direction of the field parallel or antiparallel to the direction of the shock wave. A turbulent velocity-field-coupling model is proposed. A dispersion relation shows that, in the presence of an external magnetic field, varieties of new modes in a turbulent plasma are generated. The model predicts an increasing complexity of the turbulent system with increasing strength of the field and is in very good qualitative agreement with our experiment results.

  4. Turbulent magnetized plasmas from ionizing shock waves

    SciTech Connect

    Liang, Zuohua.

    1992-01-01

    Turbulent argon plasmas produced behind hypersonic shock waves (10 less than M less than 60) are studied in the presence of weak magnetic fields at various strengths between 0 and 600 gauss, parallel and antiparallel to the shock tube's axis. The experiment is performed in a cylindrical arc discharge shock tube of 5 cm diameter and 210 cm overall length. Laser induced fluorescence and an electric probe are used as diagnostics of the ion density. Turbulent fluctuations behind the shock front are observed which persist for a time in the order of 10 msec. Using standard turbulent and chaotic analytical procedures, the influence of the magnetic field on the characterizing parameters is determined under circumstances of changing Mach number and pressure. These parameters include spectral index, correlation time scales, turbulent intensity and chaotic dimensionality. The parameters of turbulence obtained from the two diagnostics are quite consistent. Fluctuation power spectra follow a P approx. f(sup -n) behavior with 1.3 less than n less than 2.8; this agrees with theoretical predictions as well as the results of other investigators. An increasing magnetic field increases the characterizing correlation time, the turbulent intensity, and the chaotic dimension but decreases the small correlation time. Therefore the magnetic field decreases the order (increases the dimensionality) in the turbulent plasma, independent of the direction of the field parallel or antiparallel to the direction of the shock wave. A turbulent velocity-field-coupling model is proposed. A dispersion relation shows that, in the presence of an external magnetic field, varieties of new modes in a turbulent plasma are generated. The model predicts an increasing complexity of the turbulent system with increasing strength of the field and is in very good qualitative agreement with our experiment results.

  5. Large-Amplitude Electrostatic Waves Observed at a Supercritical Interplanetary Shock

    NASA Technical Reports Server (NTRS)

    Wilson, L. B., III; Cattell, C. A.; Kellogg, P. J.; Goetz, K.; Kersten, K.; Kasper, J. C.; Szabo, A.; Wilber, M.

    2010-01-01

    We present the first observations at an interplanetary shock of large-amplitude (> 100 mV/m pk-pk) solitary waves and large-amplitude (approx.30 mV/m pk-pk) waves exhibiting characteristics consistent with electron Bernstein waves. The Bernstein-like waves show enhanced power at integer and half-integer harmonics of the cyclotron frequency with a broadened power spectrum at higher frequencies, consistent with the electron cyclotron drift instability. The Bernstein-like waves are obliquely polarized with respect to the magnetic field but parallel to the shock normal direction. Strong particle heating is observed in both the electrons and ions. The observed heating and waveforms are likely due to instabilities driven by the free energy provided by reflected ions at this supercritical interplanetary shock. These results offer new insights into collisionless shock dissipation and wave-particle interactions in the solar wind.

  6. Nonlinear interactions in superfluid dynamics: Nonstationary heat transfer due to second sound shock waves

    NASA Technical Reports Server (NTRS)

    Liepmann, H. W.; Torczynski, J. R.

    1983-01-01

    Second sound techniques were used to study superfluid helium. Second sound shock waves produced relative velocities in the bulk fluid. Maximum counterflow velocities produced in this way are found to follow the Langer-Fischer prediction for the fundamental critical velocity in its functional dependence on temperature and pressure. Comparison of successive shock and rotating experiments provides strong evidence that breakdown results in vorticity production in the flow behind the shock. Schlieren pictures have verified the planar nature of second sound shocks even after multiple reflections. The nonlinear theory of second sound was repeatedly verified in its prediction of double shocks and other nonlinear phenomena.

  7. Reflectometric detection of shock wave propagation within a concrete wall

    NASA Astrophysics Data System (ADS)

    Biele, Joachim K.

    2000-04-01

    A reflectometer device was set up in order to observe shock wave propagation in concrete. Reflective elements were comprised of an upper edge of the concrete wall and the front of an embedded conduit which ran through the thickness of the wall. The reflectometer then was completed by two PVDF film sensors. The first one was located directly in the rectangular center of the vertical plane above the conduit center line. Thus, all its four corners were of equal distance, equal to the wall width of 40 cm. The second one was placed on a plug closing the intake area of the conduit in order to take face-on measurement of the blast from a HE charge to initiate shock waves in the concrete material. Measurements were taken after detonating HE face-on in front of the intake area sensor. From the reflectometer geometry and times between shocks, velocities within this type of concrete were deduced. The pulse profile is found to represent detailed material behavior under shock loading.

  8. Mechanochemistry for Shock Wave Energy Dissipation

    NASA Astrophysics Data System (ADS)

    Shaw, William; Ren, Yi; Su, Zhi; Moore, Jeffrey; Suslick, Kenneth; Dlott, Dana

    2015-06-01

    Using our laser-driven flyer-plate apparatus we have developed a technique for detecting mechanically driven chemical reactions that attenuate shock waves. In these experiments 75 μm laser-driven flyer-plates travel at speeds of up to 2.8 km/s. Photonic Doppler velocimetry is used to monitor both the flight speed and the motions of an embedded mirror behind the sample on the supporting substrate. Since the Hugoniot of the substrate is known, mirror motions can be converted into the transmitted shock wave flux and fluence through a sample. Flux shows the shock profile whereas fluence represents the total energy transferred per unit area, and both are measured as a function of sample thickness. Targets materials are micrograms of carefully engineered organic and inorganic compounds selected for their potential to undergo negative volume, endothermic reactions. In situ fluorescence measurements and a suite of post mortem analytical methods are used to detect molecular chemical reactions that occur due to impact.

  9. Modeling Propagation of Shock Waves in Metals

    SciTech Connect

    Howard, W M; Molitoris, J D

    2005-08-19

    We present modeling results for the propagation of strong shock waves in metals. In particular, we use an arbitrary Lagrange Eulerian (ALE3D) code to model the propagation of strong pressure waves (P {approx} 300 to 400 kbars) generated with high explosives in contact with aluminum cylinders. The aluminum cylinders are assumed to be both flat-topped and have large-amplitude curved surfaces. We use 3D Lagrange mechanics. For the aluminum we use a rate-independent Steinberg-Guinan model, where the yield strength and shear modulus depend on pressure, density and temperature. The calculation of the melt temperature is based on the Lindermann law. At melt the yield strength and shear modulus is set to zero. The pressure is represented as a seven-term polynomial as a function of density. For the HMX-based high explosive, we use a JWL, with a program burn model that give the correct detonation velocity and C-J pressure (P {approx} 390 kbars). For the case of the large-amplitude curved surface, we discuss the evolving shock structure in terms of the early shock propagation experiments by Sakharov.

  10. Direct Visualization of Shock Waves in Supersonic Space Shuttle Flight

    NASA Technical Reports Server (NTRS)

    OFarrell, J. M.; Rieckhoff, T. J.

    2011-01-01

    Direct observation of shock boundaries is rare. This Technical Memorandum describes direct observation of shock waves produced by the space shuttle vehicle during STS-114 and STS-110 in imagery provided by NASA s tracking cameras.

  11. Convergence of shock waves between conical and parabolic boundaries

    NASA Astrophysics Data System (ADS)

    Yanuka, D.; Zinowits, H. E.; Antonov, O.; Efimov, S.; Virozub, A.; Krasik, Ya. E.

    2016-07-01

    Convergence of shock waves, generated by underwater electrical explosions of cylindrical wire arrays, between either parabolic or conical bounding walls is investigated. A high-current pulse with a peak of ˜550 kA and rise time of ˜300 ns was applied for the wire array explosion. Strong self-emission from an optical fiber placed at the origin of the implosion was used for estimating the time of flight of the shock wave. 2D hydrodynamic simulations coupled with the equations of state of water and copper showed that the pressure obtained in the vicinity of the implosion is ˜7 times higher in the case of parabolic walls. However, comparison with a spherical wire array explosion showed that the pressure in the implosion vicinity in that case is higher than the pressure in the current experiment with parabolic bounding walls because of strong shock wave reflections from the walls. It is shown that this drawback of the bounding walls can be significantly minimized by optimization of the wire array geometry.

  12. Numerical investigation of inviscid shock wave dynamics in an expansion tube

    NASA Astrophysics Data System (ADS)

    Chang, Keun-Shik; Kim, Jong-Kwan

    1995-06-01

    Highly complicated shock wave dynamics has been numerically calculated by solving the Euler equations for a circular shock tube suddenly expanded three times of the original tube diameter at x=0. Shock waves of different shock Mach number, M s =1.5 and 2.0, have produced remarkably distinct blast jet structures. A planar shock wave took its final form after the blast by repeated Mach reflections of the blast wave: the first one at the wall and the second one at the central axis. The central Mach disc overtook and merged with the annular Mach stem before the planar shock wave was formed. In contrast to the blast wave which would propagate spherically in an open space, the present blast wave undergoes complex morphological transformation in the restricted flow passage, resulting in an unstable and oscillatory blast jet structure of highly rotational nature. The slipstream tube emanating from the shock tube exit corner decomposed into a chain of small vortex rings that interacted with the barrel shock of the jet, which caused periodic collapse of the jet structure. The finite volume-FCT formulation equipped with the time-dependent h-refinement adaptive unstructured triangular mesh technique in the present paper has contributed to resolution of the intricate physical discontinuities developing in the blast flow fields.

  13. EXPERIMENTAL STUDY OF SHOCK WAVE DYNAMICS IN MAGNETIZED PLASMAS

    SciTech Connect

    Nirmol K. Podder

    2009-03-17

    In this four-year project (including one-year extension), the project director and his research team built a shock-wave-plasma apparatus to study shock wave dynamics in glow discharge plasmas in nitrogen and argon at medium pressure (1–20 Torr), carried out various plasma and shock diagnostics and measurements that lead to increased understanding of the shock wave acceleration phenomena in plasmas. The measurements clearly show that in the steady-state dc glow discharge plasma, at fixed gas pressure the shock wave velocity increases, its amplitude decreases, and the shock wave disperses non-linearly as a function of the plasma current. In the pulsed discharge plasma, at fixed gas pressure the shock wave dispersion width and velocity increase as a function of the delay between the switch-on of the plasma and shock-launch. In the afterglow plasma, at fixed gas pressure the shock wave dispersion width and velocity decrease as a function of the delay between the plasma switch-off and shock-launch. These changes are found to be opposite and reversing towards the room temperature value which is the initial condition for plasma ignition case. The observed shock wave properties in both igniting and afterglow plasmas correlate well with the inferred temperature changes in the two plasmas.

  14. Bragg reflection of ocean waves from sandbars

    NASA Astrophysics Data System (ADS)

    Elgar, Steve; Raubenheimer, B.; Herbers, T. H. C.

    2003-01-01

    Resonant Bragg reflection of ocean surface waves by a field of natural shore-parallel sandbars was observed in Cape Cod Bay, MA. Waves transmitted through the bars were reflected strongly from the steep shoreline, and the observed cross-shore variations in the onshore- and offshore-directed energy fluxes are consistent with theory for resonant Bragg reflection, including a 20% decay of the incident wave energy flux that is an order of magnitude greater than expected for wave-orbital velocity induced bottom friction. Bragg reflection was observed for a range of incident wave conditions, including storms when sediment transported toward and away from nodes and antinodes caused by the reflecting waves might result in growth and maintenance of the sandbars.

  15. Nonequilibrium ionization phenomena behind shock waves

    SciTech Connect

    Panesi, Marco; Magin, Thierry; Huo, Winifred

    2011-05-20

    An accurate investigation of the behavior of electronically excited states of atoms and molecules in the post shock relaxation zone of a trajectory point of the FIRE II flight experiment is carried out by means of a one-dimensional flow solver coupled to a collisional-radiative model. In the rapidly ionizing regime behind a strong shock wave, the high lying bound electronic states of atoms are depleted. This leads the electronic energy level populations of atoms to depart from Boltzmann distributions which strongly affects the non-equilibrium ionization process as well as the radiative signature. The importance of correct modeling of the interaction of radiation and matter is discussed showing a strong influence on the physico-chemical properties of the gas. The paper clearly puts forward the shortcomings of the simplified approach often used in literature which strongly relies on the escape factors to characterize the optical thickness of the gas.

  16. Shock wave absorber having apertured plate

    DOEpatents

    Shin, Yong W.; Wiedermann, Arne H.; Ockert, Carl E.

    1985-01-01

    The shock or energy absorber disclosed herein utilizes an apertured plate maintained under the normal level of liquid flowing in a piping system and disposed between the normal liquid flow path and a cavity pressurized with a compressible gas. The degree of openness (or porosity) of the plate is between 0.01 and 0.60. The energy level of a shock wave travelling down the piping system thus is dissipated by some of the liquid being jetted through the apertured plate toward the cavity. The cavity is large compared to the quantity of liquid jetted through the apertured plate, so there is little change in its volume. The porosity of the apertured plate influences the percentage of energy absorbed.

  17. Shock wave absorber having apertured plate

    DOEpatents

    Shin, Y.W.; Wiedermann, A.H.; Ockert, C.E.

    1983-08-26

    The shock or energy absorber disclosed herein utilizes an apertured plate maintained under the normal level of liquid flowing in a piping system and disposed between the normal liquid flow path and a cavity pressurized with a compressible gas. The degree of openness (or porosity) of the plate is between 0.01 and 0.60. The energy level of a shock wave travelling down the piping system thus is dissipated by some of the liquid being jetted through the apertured plate toward the cavity. The cavity is large compared to the quantity of liquid jetted through the apertured plate, so there is little change in its volume. The porosity of the apertured plate influences the percentage of energy absorbed.

  18. Particle Acceleration in SN1006 Shock Waves

    NASA Technical Reports Server (NTRS)

    Raymond, John C.; Ghavamian, Parviz; Sonneborn, George (Technical Monitor)

    2003-01-01

    This grant is for the analysis of FUSE observations of particle acceleration in supernova remnant SN1006 shock waves. We have performed quick look analysis of the data, but because the source is faint and because the O VI emission lines on SN1006 are extremely broad, extreme care is needed for background subtraction and profile fitting. Moreover, the bulk of the analysis in will consist of model calculations. The Ly beta and O VI lines are clearly detected at the position in the NW filament of SN1006, but not in the NE position where non-thermal X-rays are strong. The lack of O VI emission in the NE places an upper limit on the pre-shock density there.

  19. Nonplanar electrostatic shock waves in dense plasmas

    SciTech Connect

    Masood, W.; Rizvi, H.

    2010-02-15

    Two-dimensional quantum ion acoustic shock waves (QIASWs) are studied in an unmagnetized plasma consisting of electrons and ions. In this regard, a nonplanar quantum Kadomtsev-Petviashvili-Burgers (QKPB) equation is derived using the small amplitude perturbation expansion method. Using the tangent hyperbolic method, an analytical solution of the planar QKPB equation is obtained and subsequently used as the initial profile to numerically solve the nonplanar QKPB equation. It is observed that the increasing number density (and correspondingly the quantum Bohm potential) and kinematic viscosity affect the propagation characteristics of the QIASW. The temporal evolution of the nonplanar QIASW is investigated both in Cartesian and polar planes and the results are discussed from the numerical stand point. The results of the present study may be applicable in the study of propagation of small amplitude localized electrostatic shock structures in dense astrophysical environments.

  20. Wave and particle evolution downstream of quasi-perpendicular shocks

    NASA Technical Reports Server (NTRS)

    Mckean, M. E.; Omidi, N.; Krauss-Varban, D.; Karimabadi, H.

    1995-01-01

    Distributions of ions heated in quasi-perpendicular bow shocks have large perpendicular temperature anisotropies that provide free energy for the growth of Alfven ion cyclotron (AIC) and mirror waves. These modes are often obsreved in the Earth's magnetosheath. Using two-dimensional hybrid simulations, we show that these waves are produced near the shock front and convected downstream rather than being produced locally downstream. The wave activity reduces the proton anisotropy to magnetosheath levels within a few tens of gyroradii of the shock but takes significantly longer to reduce the anisotropy of He(++) ions. The waves are primarily driven by proton anisotropy and the dynamics of the helium ions is controlled by the proton waves. Downstream of high Mach number shocks, mirror waves compete effectively with AIC waves. Downstream of low Mach number shocks, AIC waves dominate.

  1. Supersonic shock wave/vortex interaction

    NASA Technical Reports Server (NTRS)

    Settles, G. S.; Cattafesta, L.

    1993-01-01

    Although shock wave/vortex interaction is a basic and important fluid dynamics problem, very little research has been conducted on this topic. Therefore, a detailed experimental study of the interaction between a supersonic streamwise turbulent vortex and a shock wave was carried out at the Penn State Gas Dynamics Laboratory. A vortex is produced by replaceable swirl vanes located upstream of the throat of various converging-diverging nozzles. The supersonic vortex is then injected into either a coflowing supersonic stream or ambient air. The structure of the isolated vortex is investigated in a supersonic wind tunnel using miniature, fast-response, five-hole and total temperature probes and in a free jet using laser Doppler velocimetry. The cases tested have unit Reynolds numbers in excess of 25 million per meter, axial Mach numbers ranging from 2.5 to 4.0, and peak tangential Mach numbers from 0 (i.e., a pure jet) to about 0.7. The results show that the typical supersonic wake-like vortex consists of a non-isentropic, rotational core, where the reduced circulation distribution is self similar, and an outer isentropic, irrotational region. The vortex core is also a region of significant turbulent fluctuations. Radial profiles of turbulent kinetic energy and axial-tangential Reynolds stress are presented. The interactions between the vortex and both oblique and normal shock waves are investigated using nonintrusive optical diagnostics (i.e. schlieren, planar laser scattering, and laser Doppler velocimetry). Of the various types, two Mach 2.5 overexpanded-nozzle Mach disc interactions are examined in detail. Below a certain vortex strength, a 'weak' interaction exists in which the normal shock is perturbed locally into an unsteady 'bubble' shock near the vortex axis, but vortex breakdown (i.e., a stagnation point) does not occur. For stronger vortices, a random unsteady 'strong' interaction results that causes vortex breakdown. The vortex core reforms downstream of

  2. Electrostatic waves in the bow shock at Uranus

    SciTech Connect

    Moses, S.L.; Coroniti, F.V.; Kennel, C.F.; Scarf, F.L. ); Bagenal, F. ); Lepping, R.P. ); Quest, K.B. ); Kurth, W.S. )

    1989-10-01

    Electrostatic emissions measured by the Voyager 2 plasma wave detector (PWS) during the inbound crossing of the Uranian bow shock are shown to differ in some aspects from the waves measured during bow shock crossings at Jupiter and Saturn. The wave amplitudes in the foot of the bow shock at Uranus are in general much lower than those detected at the other out planets due to the unusually enhanced solar wind ion temperature during the crossing. This reduces the effectiveness of wave-particle interactions in heating the incoming electrons. Strong wave emissions are observed in the shock ramp that possibly arise from currents producing a Buneman mode instability. Plasma instrument (PLS) and magnetometer (MAG) measurements reveal a complicated shock structure reminiscent of computer simulations of high-Mach number shocks when the effects of anomalous resistivity are reduced, and are consistent with high ion temperatures restricting the growth of electrostatic waves.

  3. Nonlinear waves and shocks in a rigid acoustical guide.

    PubMed

    Fernando, Rasika; Druon, Yann; Coulouvrat, François; Marchiano, Régis

    2011-02-01

    A model is developed for the propagation of finite amplitude acoustical waves and weak shocks in a straight duct of arbitrary cross section. It generalizes the linear modal solution, assuming mode amplitudes slowly vary along the guide axis under the influence of nonlinearities. Using orthogonality properties, the model finally reduces to a set of ordinary differential equations for each mode at each of the harmonics of the input frequency. The theory is then applied to a two-dimensional waveguide. Dispersion relations indicate that there can be two types of nonlinear interactions either called "resonant" or "non-resonant." Resonant interactions occur dominantly for modes propagating at a rather large angle with respect to the axis and involve mostly modes propagating with the same phase velocity. In this case, guided propagation is similar to nonlinear plane wave propagation, with the progressive steepening up to shock formation of the two waves that constitute the mode and reflect onto the guide walls. Non-resonant interactions can be observed as the input modes propagate at a small angle, in which case, nonlinear interactions involve many adjacent modes having close phase velocities. Grazing propagation can also lead to more complex phenomena such as wavefront curvature and irregular reflection. PMID:21361419

  4. Large amplitude MHD waves upstream of the Jovian bow shock

    NASA Technical Reports Server (NTRS)

    Goldstein, M. L.; Smith, C. W.; Matthaeus, W. H.

    1983-01-01

    Observations of large amplitude magnetohydrodynamics (MHD) waves upstream of Jupiter's bow shock are analyzed. The waves are found to be right circularly polarized in the solar wind frame which suggests that they are propagating in the fast magnetosonic mode. A complete spectral and minimum variance eigenvalue analysis of the data was performed. The power spectrum of the magnetic fluctuations contains several peaks. The fluctuations at 2.3 mHz have a direction of minimum variance along the direction of the average magnetic field. The direction of minimum variance of these fluctuations lies at approximately 40 deg. to the magnetic field and is parallel to the radial direction. We argue that these fluctuations are waves excited by protons reflected off the Jovian bow shock. The inferred speed of the reflected protons is about two times the solar wind speed in the plasma rest frame. A linear instability analysis is presented which suggests an explanation for many of the observed features of the observations.

  5. Internal energy relaxation in shock wave structure

    SciTech Connect

    Josyula, Eswar Suchyta, Casimir J.; Boyd, Iain D.; Vedula, Prakash

    2013-12-15

    The Wang Chang-Uhlenbeck (WCU) equation is numerically integrated to characterize the internal structure of Mach 3 and Mach 5 shock waves in a gas with excitation in the internal energy states for the treatment of inelastic collisions. Elastic collisions are modeled with the hard sphere collision model and the transition rates for the inelastic collisions modified appropriately using probabilities based on relative velocities of the colliding particles. The collision integral is evaluated by the conservative discrete ordinate method [F. Tcheremissine, “Solution of the Boltzmann kinetic equation for high-speed flows,” Comput. Math. Math. Phys. 46, 315–329 (2006); F. Cheremisin, “Solution of the Wang Chang-Uhlenbeck equation,” Dokl. Phys. 47, 487–490 (2002)] developed for the Boltzmann equation. For the treatment of the diatomic molecules, the internal energy modes in the Boltzmann equation are described quantum mechanically given by the WCU equation. As a first step in the treatment of the inelastic collisions by the WCU equation, a two- and three-quantum system is considered to study the effect of the varying of (1) the inelastic cross section and (2) the energy gap between the quantum energy states. An alternative method, the direct simulation Monte Carlo method, is used for the Mach 3 shock wave to ensure the consistency of implementation in the two methods and there is an excellent agreement between the two methods. The results from the WCU implementation showed consistent trends for the Mach 3 and Mach5 standing shock waves simulations. Inelastic contributions change the downstream equilibrium state and allow the flow to transition to the equilibrium state further upstream.

  6. Mitigating Shock Waves Using Solid Obstacles with Semi-Circular Grooves

    NASA Astrophysics Data System (ADS)

    Amen, Nicholas; Cajal, Arturo; Eliasson, Veronica

    2015-11-01

    An experimental investigation was performed to assess the effectiveness of multiple obstacles with semi-circular grooves placed along a logarithmic spiral curve as a method to attenuate a shock wave. Previous research has shown that the use of multiple obstacles arranged in a log spiral configuration can attenuate a shock wave by reducing the energy of the wave. In this study, four different obstacle cross-sections in the same log spiral configuration were considered. All spirals had square cross-sections with zero, one, two, or three semi-circular grooves in each face. They were placed inside a shock tube where the incident, reflected, and transmitted shocks were visualized with high-speed schlieren imaging and the pressure histories were recorded with four pressure transducers. Each case was studied varying shock Mach numbers between M =1.1 and M =1.5. The pressure traces were used to establish incident, reflected, and transmitted shock strength and wave speed. Results for the zero groove case were compared to that of the one, two, and three groove cross-sections which show that increasing the number of grooves has a profound effect on the generation of the reflected wave and impacts the transmitted wave via vortex generation behind the spiral.

  7. A multi-scale approach to molecular dynamics simulations of shock waves

    SciTech Connect

    Reed, E J; Fried, L E; Manaa, M R; Joannopoulos, J D

    2004-09-03

    Study of the propagation of shock waves in condensed matter has led to new discoveries ranging from new metastable states of carbon [1] to the metallic conductivity of hydrogen in Jupiter, [2] but progress in understanding the microscopic details of shocked materials has been extremely difficult. Complications can include the unexpected formation of metastable states of matter that determine the structure, instabilities, and time-evolution of the shock wave. [1,3] The formation of these metastable states can depend on the time-dependent thermodynamic pathway that the material follows behind the shock front. Furthermore, the states of matter observed in the shock wave can depend on the timescale on which observation is made. [4,1] Significant progress in understanding these microscopic details has been made through molecular dynamics simulations using the popular non-equilibrium molecular dynamics (NEMD) approach to atomistic simulation of shock compression. [5] The NEMD method involves creating a shock at one edge of a large system by assigning some atoms at the edge a fixed velocity. The shock propagates across the computational cell to the opposite side. The computational work required by NEMD scales at least quadratically in the evolution time because larger systems are needed for longer simulations to prevent the shock wave from reflecting from the edge of the computational cell and propagating back into the cell. When quantum mechanical methods with poor scaling of computational effort with system size are employed, this approach to shock simulations rapidly becomes impossible.

  8. Observability of Multiply Reflected P Waves

    NASA Astrophysics Data System (ADS)

    Foundotos, Michel; Nolet, Guust

    2010-05-01

    In order to constrain the shallow structure of the Earth in global tomography, Love and Rayleigh waves are often used. However these waves are mostly sensitive to the S wave velocity structure. P-wave energy is either evanescent, or leaking away at every surface reflection that generates an S wave which travels much deeper into the mantle. For that reason, to study the shallow P velocity structure of the Earth, we need to study P-waves at regional distances if a good seismic station coverage is available. Otherwise we can use multiple P reflections at teleseismic distance when regional data are not available (as in the oceans for instance). The major aim of this work was first of all to ensure that these multiply reflected P waves can adequately be observed in real data and also to investigate how many reflections at the surface these reflected waves can still be seen and to investigate how strongly the amplitude of multiply reflected P diminishes because of energy loss into S waves. For this study we are comparing the synthetic predictions computed with a Spectral Element Method for a spherically symmetric earth (Nissen-Meyer et al, 2007) with observed data. Attention will be made on Synthetics with and without oceanic reflection points and compare these with observations. We used 300 events recorded (90000 seismograms) from the dense network of US ARRAY, which allows us to make a very large number of observations. Our study shows that three times reflected PPP waves are very well observed for epicentral distances > 60 degrees and for events with Mw > 5.5 , despite the ray-theoretical prediction that at certain distances almost all of their compressional energy is converted to shear waves. However, the four times reflected PPPP waves do not appear everywhere clearly. PPPP can be observed for epicentral distances > 90 degrees.

  9. Shock waves and nucleosynthesis in type II supernovae

    NASA Technical Reports Server (NTRS)

    Aufderheide, M. B.; Baron, E.; Thielemann, F.-K.

    1991-01-01

    In the study of nucleosynthesis in type II SN, shock waves are initiated artificially, since collapse calculations do not, as yet, give self-consistent shock waves strong enough to produce the SN explosion. The two initiation methods currently used by light-curve modelers are studied, with a focus on the peak temperatures and the nucleosynthetic yields in each method. The various parameters involved in artificially initiating a shock wave and the effects of varying these parameters are discussed.

  10. AN EXPERIMENTAL STUDY OF SHOCK WAVES RESULTING FROM THE IMPACT OF HIGH VELOCITY MISSILES ON ANIMAL TISSUES

    PubMed Central

    Harvey, E. Newton; McMillen, J. Howard

    1947-01-01

    The spark shadowgram method of studying shock waves is described. It has been used to investigate the properties of such waves produced by the impact of a high velocity missile on the surface of water. The method can be adapted for study of behavior of shock waves in tissue by placing the tissue on a water surface or immersing it in water. Spark shadowgrams then reveal waves passing from tissue to water or reflected from tissue surfaces. Reflection and transmission of shock waves from muscle, liver, stomach, and intestinal wall are compared with reflection from non-living surfaces such as gelatin gel, steel, plexiglas, cork, and air. Because of its heterogeneous structure, waves transmitted by tissue are dispersed and appear as a series of wavelets. When the accoustical impedance (density x wave velocity) of a medium is less than that in which the wave is moving, reflection will occur with inversion of the wave; i.e., a high pressure wave will become a low pressure wave. This inversion occurs at an air surface and is illustrated by shadowgrams of reflection from stomach wall, from a segment of colon filled with gas, and from air-filled rubber balloons. Bone (human skull and beef ribs) shows good reflection and some transmission of shock waves. When steel is directly hit by a missile, clearly visible elastic waves pass from metal to water, but a similar direct hit on bone does not result in elastic waves strong enough to be detected by a spark shadowgram. PMID:19871617

  11. Multiscale whistler waves within Earth's perpendicular bow shock

    NASA Astrophysics Data System (ADS)

    Hull, A. J.; Muschietti, L.; Oka, M.; Larson, D. E.; Mozer, F. S.; Chaston, C. C.; Bonnell, J. W.; Hospodarsky, G. B.

    2012-12-01

    We present observations of intense whistler waves made by Polar in the frequency range from a few Hz to 600 Hz within Earth's nearly perpendicular bow shock. The long duration burst data provided by Polar reveal the detailed properties of whistler waves in context with the macrostructure of the layer of this supercritical shock. We show that the pedestal and ramp have superposed quasiperiodic, large amplitude precursor substructure occurring at a cadence of ˜3 sec, which is near the ion cyclotron period. With increasing penetration into the shock front, the amplitude of this substructure increases and ultimately reaches downstream values. The nonlinear substructure is shown to be concentrated regions of intense whistler wave activity. Power spectra in the whistler range show strong enhancements in two distinct bands: a relatively broadband lower frequency component occurring near the lower hybrid frequency (a few tens of Hertz) and a higher frequency component at a few hundred Hertz. The lower frequency component is composed of right-hand polarized whistler wave packets propagating quasiparallel to the magnetic coplanarity plane at oblique angles with respect to both the magnetic field and shock normal, with respective anglesθkb varying from 50°-70° and θkn ˜ 50°. These waves generally have relatively large amplitude (δB/B0˜ 0.1-0.4) magnetic fields ranging from a few nT to 15 nT. Given their preferential upstream propagation near the magnetic coplanarity plane, they are likely generated by a kinetic cross-field streaming instability driven by the relative drift between the reflected ion beam and the electrons. The high-frequency component appears to be the shock analog of whistler "lion roars" often observed in the magnetosheath. The lion roars occur within the foot and into the shock ramp in regions where sufficiently intense low-frequency whistlers exist. These are right-hand circularly polarized wave packets lasting up to ˜10 cycles, with amplitudes

  12. Shock wave processes in collisional gas particle mixtures

    NASA Astrophysics Data System (ADS)

    Khmel, T. A.; Fedorov, A. V.

    2016-06-01

    Structures and propagation of shock waves in high density particle suspensions in gas are investigated theoretically and numerically. A physical and mathematical model which takes into account integral collisions between the particles on the basis of molecular-kinetic approaches of theory of granular materials is applied. The possibility of different types of shock waves, including double front structures is revealed. The role of particle collisions in the dynamics of particle dense layer expansion under an influence of divergent shock wave and in processes of shock wave diffraction past a backward-facing step is analyzed.

  13. Biodamage via shock waves initiated by irradiation with ions.

    PubMed

    Surdutovich, Eugene; Yakubovich, Alexander V; Solov'yov, Andrey V

    2013-01-01

    Radiation damage following the ionising radiation of tissue has different scenarios and mechanisms depending on the projectiles or radiation modality. We investigate the radiation damage effects due to shock waves produced by ions. We analyse the strength of the shock wave capable of directly producing DNA strand breaks and, depending on the ion's linear energy transfer, estimate the radius from the ion's path, within which DNA damage by the shock wave mechanism is dominant. At much smaller values of linear energy transfer, the shock waves turn out to be instrumental in propagating reactive species formed close to the ion's path to large distances, successfully competing with diffusion. PMID:23411473

  14. Magnetosonic shock wave in collisional pair-ion plasma

    NASA Astrophysics Data System (ADS)

    Adak, Ashish; Sikdar, Arnab; Ghosh, Samiran; Khan, Manoranjan

    2016-06-01

    Nonlinear propagation of magnetosonic shock wave has been studied in collisional magnetized pair-ion plasma. The masses of both ions are same but the temperatures are slightly different. Two fluid model has been taken to describe the model. Two different modes of the magnetosonic wave have been obtained. The dynamics of the nonlinear magnetosonic wave is governed by the Korteweg-de Vries Burgers' equation. It has been shown that the ion-ion collision is the source of dissipation that causes the Burgers' term which is responsible for the shock structures in equal mass pair-ion plasma. The numerical investigations reveal that the magnetosonic wave exhibits both oscillatory and monotonic shock structures depending on the strength of the dissipation. The nonlinear wave exhibited the oscillatory shock wave for strong magnetic field (weak dissipation) and monotonic shock wave for weak magnetic field (strong dissipation). The results have been discussed in the context of the fullerene pair-ion plasma experiments.

  15. Multi-reflective acoustic wave device

    DOEpatents

    Andle, Jeffrey C.

    2006-02-21

    An acoustic wave device, which utilizes multiple localized reflections of acoustic wave for achieving an infinite impulse response while maintaining high tolerance for dampening effects, is disclosed. The device utilized a plurality of electromechanically significant electrodes disposed on most of the active surface. A plurality of sensors utilizing the disclosed acoustic wave mode device are also described.

  16. Developments in strong shock wave position tracking

    NASA Astrophysics Data System (ADS)

    Rae, Philip; Glover, Brain; Perry, Lee; WX-6; WX-7 Team

    2011-06-01

    This poster will highlight several modified techniques to allow the position vs. time to be tracked in strong shock situations (such as detonation). Each is a modification or improvement of existing ideas either making use of advances in specialist materials availability or recent advances in electronics.) Shorting embedded mini-coaxial cable with a standing microwave pattern. This technique is a modified version of an old LANL method of shock position tracking making use of a traveling short imposed in an embedded coaxial cable. A high frequency standing wave (3-8GHz) is present in the cable and the moving short position can be tracked by monitoring the output voltage envelope as a function of time. A diode detector is used to allow the envelope voltage to be monitored on a regular low frequency digitizer significantly reducing the cost. The small and cheap high frequency voltage generators now available allow much greater spatial resolution than possible previously. 2) Very thin shorting resistance track gauges. Parallel tracks of constantan resistance material are etched on a thin dielectric substrate. The gauges are less than 0.2 mm thick. The ionized gas present in a detonation front sweeps up the tracks lowering the measured resistance. A potential divider circuit allows the shock position vs. time to be monitored on a regular digitizer after easy calibration. The novel feature is the thin section of the gauge producing minimal perturbation in the detonation front.

  17. Particle Acceleration in SN1006 Shock Waves

    NASA Technical Reports Server (NTRS)

    Sonneborn, George (Technical Monitor); Raymond, John C.

    2004-01-01

    The FUSE data have been reduced, and a paper on the results is in progress. The main results have been presented in a poster at the January 2004 AAS meeting and an ApJ paper in press. The primary result is that the widths of the 0 VI lines in the NW filament are a bit less than the width expected if the oxygen kinetic temperature is 16 times the proton temperature (mass proportional heating). This is at variance with measurements of shocks in the heliosphere, where preferential heating of oxygen and other heavy species is observed. The paper discusses the theoretical implications for collisionless shock wave physics. A secondary result is that no O VI emission was observed from the NE filament. While the very different particle distribution in that region can partially account for the weakness of the O VI lines, the simplest interpretation is that the pre-shock density in the NE is less than 0.22 times the density in the NW.

  18. Radial Shock Wave Devices Generate Cavitation

    PubMed Central

    Császár, Nikolaus B. M.; Angstman, Nicholas B.; Milz, Stefan; Sprecher, Christoph M.; Kobel, Philippe; Farhat, Mohamed; Furia, John P.; Schmitz, Christoph

    2015-01-01

    Background Conflicting reports in the literature have raised the question whether radial extracorporeal shock wave therapy (rESWT) devices and vibrating massage devices have similar energy signatures and, hence, cause similar bioeffects in treated tissues. Methods and Findings We used laser fiber optic probe hydrophone (FOPH) measurements, high-speed imaging and x-ray film analysis to compare fundamental elements of the energy signatures of two rESWT devices (Swiss DolorClast; Electro Medical Systems, Nyon, Switzerland; D-Actor 200; Storz Medical, Tägerwillen, Switzerland) and a vibrating massage device (Vibracare; G5/General Physiotherapy, Inc., Earth City, MO, USA). To assert potential bioeffects of these treatment modalities we investigated the influence of rESWT and vibrating massage devices on locomotion ability of Caenorhabditis elegans (C. elegans) worms. Results FOPH measurements demonstrated that both rESWT devices generated acoustic waves with comparable pressure and energy flux density. Furthermore, both rESWT devices generated cavitation as evidenced by high-speed imaging and caused mechanical damage on the surface of x-ray film. The vibrating massage device did not show any of these characteristics. Moreover, locomotion ability of C. elegans was statistically significantly impaired after exposure to radial extracorporeal shock waves but was unaffected after exposure of worms to the vibrating massage device. Conclusions The results of the present study indicate that both energy signature and bioeffects of rESWT devices are fundamentally different from those of vibrating massage devices. Clinical Relevance Prior ESWT studies have shown that tissues treated with sufficient quantities of acoustic sound waves undergo cavitation build-up, mechanotransduction, and ultimately, a biological alteration that “kick-starts” the healing response. Due to their different treatment indications and contra-indications rESWT devices cannot be equated to vibrating

  19. Shock wave propagation in semi-crystalline polyethylene: An atomic-scale investigation

    NASA Astrophysics Data System (ADS)

    Elder, Robert M.; O'Connor, Thomas C.; Yeh, In-Chul; Chantawansri, Tanya L.; Sirk, Timothy W.; Robbins, Mark O.; Andzelm, Jan W.

    Highly oriented polyethylene (PE) fibers are used in protection applications, therefore elucidation of their response under high strain-rate impact events is vital. Although PE fibers can have high crystallinity (>95%), they also contain defects such as amorphous domains. Using molecular dynamics simulations, we investigate shock propagation through crystalline, amorphous, and semi-crystalline PE. We generate compressive shock waves of varying strength, quantify their dynamics, and characterize their effect on material properties at the atomic scale. In the semi-crystalline PE model, the differing density and molecular order of amorphous PE and crystalline PE result in differing shock impedances, which causes reflection and refraction of shock waves at interfaces between the phases. We quantify the properties (e.g. pressure, velocity) of the reflected and refracted waves, which differ from those of the incident wave, and compare with results from impedance matching. We also examine the reflection, absorption, and transmission of energy at the crystalline-amorphous interface. Depending on shock strength, amorphous defects can dissipate shock energy, which attenuates the shock and leads to effects such as localized heating.

  20. Mercury's bow shock and foreshock waves observed by Messenger

    NASA Astrophysics Data System (ADS)

    Blanco-Cano, X.; Le, G.; Boardsen, S.; Chi, P.; Slavin, J. A.; Anderson, B. J.; Korth, H.

    2013-09-01

    The region upstream from a planetary bow shock is a natural plasma laboratory containing a variety of wave particle phenomena. The study of foreshocks other than the Earth's is important for extending our understanding of collisionless shocks and foreshock physics since the bow shock strength varies with heliocentric distance from the Sun, and the sizes of the bow shocks are different at different planets. Mercury's bow shock is unique in our solar system as it is produced by moderate Mach number and low plasma beta solar wind blowing over a small magnetized body with a predominately radial interplanetary magnetic field. We use Messenger high resolution (20 samples per second) magnetic field data to study Mercury's bow shock structure, and the characteristics of ultra low frequency waves observed at the foreshock. Bow shock profiles depend on the upstream Mach number, on shock geometry with respect to the upstream magnetic field, and on the plasma beta. Mercury's bow shock is weaker than Earth's with a Mach number MA ˜ 3, and is 10 times smaller. Thus, a more laminar shock is expected and a less complex foreshock may develop. A preliminary study has shown the existence of at least three types of waves: 1) whistler waves at frequencies near 2 Hz; 2) waves with frequencies ~ 0.1 Hz; 3) fluctuations with broad spectral peaks centered at ~ 0.6 Hz. Whistler waves propagate at angles up to 30 degrees, and lower frequency waves are more parallel propagating. We investigate wave properties such as polarization, ellipticity and compressibility. We also discuss wave origin and evolution. While whistler waves may be generated at the bow shock, the origin of lower frequency waves can be attributed to local generation by kinetic ion-ion instabilities. Due to the small scale size of Mercury's foreshock it is possible that waves suffer less steepening than at Earth.

  1. Shock-wave boundary layer interactions

    NASA Technical Reports Server (NTRS)

    Delery, J.; Marvin, J. G.; Reshotko, E.

    1986-01-01

    Presented is a comprehensive, up-to-date review of the shock-wave boundary-layer interaction problem. A detailed physical description of the phenomena for transonic and supersonic speed regimes is given based on experimental observations, correlations, and theoretical concepts. Approaches for solving the problem are then reviewed in depth. Specifically, these include: global methods developed to predict sudden changes in boundary-layer properties; integral or finite-difference methods developed to predict the continuous evolution of a boundary-layer encountering a pressure field induced by a shock wave; coupling methods to predict entire flow fields; analytical methods such as multi-deck techniques; and finite-difference methods for solving the time-dependent Reynolds-averaged Navier-Stokes equations used to predict the development of entire flow fields. Examples are presented to illustrate the status of the various methods and some discussion is devoted to delineating their advantages and shortcomings. Reference citations for the wide variety of subject material are provided for readers interested in further study.

  2. Oxy-acetylene driven laboratory scale shock tubes for studying blast wave effects.

    PubMed

    Courtney, Amy C; Andrusiv, Lubov P; Courtney, Michael W

    2012-04-01

    This paper describes the development and characterization of modular, oxy-acetylene driven laboratory scale shock tubes. Such tools are needed to produce realistic blast waves in a laboratory setting. The pressure-time profiles measured at 1 MHz using high-speed piezoelectric pressure sensors have relevant durations and show a true shock front and exponential decay characteristic of free-field blast waves. Descriptions are included for shock tube diameters of 27-79 mm. A range of peak pressures from 204 kPa to 1187 kPa (with 0.5-5.6% standard error of the mean) were produced by selection of the driver section diameter and distance from the shock tube opening. The peak pressures varied predictably with distance from the shock tube opening while maintaining both a true blast wave profile and relevant pulse duration for distances up to about one diameter from the shock tube opening. This shock tube design provides a more realistic blast profile than current compression-driven shock tubes, and it does not have a large jet effect. In addition, operation does not require specialized personnel or facilities like most blast-driven shock tubes, which reduces operating costs and effort and permits greater throughput and accessibility. It is expected to be useful in assessing the response of various sensors to shock wave loading; assessing the reflection, transmission, and absorption properties of candidate armor materials; assessing material properties at high rates of loading; assessing the response of biological materials to shock wave exposure; and providing a means to validate numerical models of the interaction of shock waves with structures. All of these activities have been difficult to pursue in a laboratory setting due in part to lack of appropriate means to produce a realistic blast loading profile. PMID:22559580

  3. Oxy-acetylene driven laboratory scale shock tubes for studying blast wave effects

    NASA Astrophysics Data System (ADS)

    Courtney, Amy C.; Andrusiv, Lubov P.; Courtney, Michael W.

    2012-04-01

    This paper describes the development and characterization of modular, oxy-acetylene driven laboratory scale shock tubes. Such tools are needed to produce realistic blast waves in a laboratory setting. The pressure-time profiles measured at 1 MHz using high-speed piezoelectric pressure sensors have relevant durations and show a true shock front and exponential decay characteristic of free-field blast waves. Descriptions are included for shock tube diameters of 27-79 mm. A range of peak pressures from 204 kPa to 1187 kPa (with 0.5-5.6% standard error of the mean) were produced by selection of the driver section diameter and distance from the shock tube opening. The peak pressures varied predictably with distance from the shock tube opening while maintaining both a true blast wave profile and relevant pulse duration for distances up to about one diameter from the shock tube opening. This shock tube design provides a more realistic blast profile than current compression-driven shock tubes, and it does not have a large jet effect. In addition, operation does not require specialized personnel or facilities like most blast-driven shock tubes, which reduces operating costs and effort and permits greater throughput and accessibility. It is expected to be useful in assessing the response of various sensors to shock wave loading; assessing the reflection, transmission, and absorption properties of candidate armor materials; assessing material properties at high rates of loading; assessing the response of biological materials to shock wave exposure; and providing a means to validate numerical models of the interaction of shock waves with structures. All of these activities have been difficult to pursue in a laboratory setting due in part to lack of appropriate means to produce a realistic blast loading profile.

  4. On imploding cylindrical and spherical shock waves in a perfect gas

    NASA Astrophysics Data System (ADS)

    Ponchaut, N. F.; Hornung, H. G.; Pullin, D. I.; Mouton, C. A.

    2006-08-01

    The problem of a cylindrically or spherically imploding and reflecting shock wave in a flow initially at rest is studied without the use of the strong-shock approximation. Dimensional arguments are first used to show that this flow admits a general solution where an infinitesimally weak shock from infinity strengthens as it converges towards the origin. For a perfect-gas equation of state, this solution depends only on the dimensionality of the flow and on the ratio of specific heats. The Guderley power-law result can then be interpreted as the leading-order, strong-shock approximation, valid near the origin at the implosion centre. We improve the Guderley solution by adding two further terms in the series expansion solution for both the incoming and the reflected shock waves. A series expansion, valid where the shock is still weak and very far from the origin, is also constructed. With an appropriate change of variables and using the exact shock-jump conditions, a numerical, characteristics-based solution is obtained describing the general shock motion from almost infinity to very close to the reflection point. Comparisons are made between the series expansions, the characteristics solution, and the results obtained using an Euler solver. These show that the addition of two terms to the Guderley solution significantly extends the range of validity of the strong-shock series expansion.

  5. Dynamic reflectance of tin shocked from its beta to BCT phase

    NASA Astrophysics Data System (ADS)

    Stevens, Gerald; La Lone, Brandon; Veeser, Lynn; Turley, Dale

    2015-06-01

    Shock-induced phase transitions have historically been inferred by features in loading/unloading velocity wave profiles, which arise due to volume or sound speed differences between phases. In 2010, we used a flash-lamp illuminated multi-band reflectometer to demonstrate that iron, tin, cerium, and gallium have measureable reflectance changes at phase boundaries. We have improved upon our prior technique, utilizing an integrating sphere with an internal xenon flash lamp to illuminate a shocked metal beneath a LiF window. The new reflectance system is insensitive to motion, tilt, or curvature and measures the absolute (not relative) reflectance within five bands centered at 500, 700, 850, 1300, and 1550 nm. We have made dynamic reflectance measurements of tin samples shocked to pressures above and below the beta-bct phase transition using either high explosives or a gas gun. Below the transition, the visible reflectance decreases with pressure. At and above the transition, the visible reflectance increases to values higher than the ambient values. Reflectance can therefore be used to locate the beta-bct phase transition boundary for tin, independent of the velocity wave profile. This work was done by National Security Technologies, LLC, under Contract No. DE-AC52-06NA25946 with the U.S. Department of Energy, and supported by the Site-Directed Research and Development Program.

  6. Planar shock wave sliding over a water layer

    NASA Astrophysics Data System (ADS)

    Rodriguez, V.; Jourdan, G.; Marty, A.; Allou, A.; Parisse, J.-D.

    2016-08-01

    In this work, we conduct experiments to study the interaction between a horizontal free water layer and a planar shock wave that is sliding over it. Experiments are performed at atmospheric pressure in a shock tube with a square cross section (200× 200 mm^2) for depths of 10, 20, and 30 mm; a 1500-mm-long water layer; and two incident planar shock waves having Mach numbers of 1.11 and 1.43. We record the pressure histories and high-speed visualizations to study the flow patterns, surface waves, and spray layers behind the shock wave. We observe two different flow patterns with ripples formed at the air-water interface for the weaker shock wave and the dispersion of a droplet mist for the stronger shock wave. From the pressure signals, we extract the delay time between the arrival of the compression wave into water and the shock wave in air at the same location. We show that the delay time evolves with the distance traveled over the water layer, the depth of the water layer, and the Mach number of the shock wave.

  7. Waves in low-beta plasmas - Slow shocks

    NASA Technical Reports Server (NTRS)

    Steinolfson, R. S.; Hundhausen, A. J.

    1989-01-01

    Results from wave theory and numerical simulation of the nonlinear MHD equations are used to study the response of a conducting fluid containing an embedded magnetic field with beta less than 1 to the sudden injection of material along the field lines. It is shown that the injection produces slow shocks with configurations which are concave toward the ejecta driver. Fast-mode waves which have not steepened into the shock precede the slow shock and alter the ambient medium. When beta equals 0.1, the fast mode becomes a transverse wave for parallel propagation, while the slow wave approaches a longitudinal, or sound, wave.

  8. Reflection properties of gravito-acoustic waves

    NASA Astrophysics Data System (ADS)

    Jovanović, Gordana

    2016-03-01

    We derive the dispersion equation for gravito-acoustic waves in an isothermal gravitationally stratified nonmagnetized atmosphere. In this model, with constant sound speed, it is possible to derive analytically the equations for gravito-acoustic waves. The large value of the viscous Reynolds number in the solar atmosphere imply that the dissipative terms in HD (hydrodynamics) equations are negligible. We consider the plane boundary z = 0 between two isothermal atmosphere regions and using the boundary conditions we derive the equation for the reflection coeffcient of gravito-acoustic waves. For the frequencies much greater than acoustic cutoff frequency, the reflection coefficient of the acoustic waves modified by gravity is the same as in the case of the pure acoustic waves. Reflection coefficient for the gravity waves is very high, R ≈ 1.

  9. Interplanetary shock waves and the structure of solar wind disturbances

    NASA Technical Reports Server (NTRS)

    Hundhausen, A. J.

    1972-01-01

    Observations and theoretical models of interplanetary shock waves are reviewed, with emphasis on the large-scale characteristics of the associated solar wind disturbances and on the relationship of these disturbances to solar activity. The sum of observational knowledge indicates that shock waves propagate through the solar wind along a broad, roughly spherical front, ahead of plasma and magnetic field ejected from solar flares. Typically, the shock front reaches 1 AU about two days after its flare origin, and is of intermediate strength. Not all large flares produce observable interplanetary shock waves; the best indicator of shock production appears to be the generation of both type 2 and type 4 radio bursts by a flare. Theoretical models of shock propagation in the solar wind can account for the typically observed shock strength, transit time, and shape.

  10. Steady state risetimes of shock waves in the atmosphere

    NASA Technical Reports Server (NTRS)

    Raspet, Richard; Bass, Henry; Yao, Lixin; Wu, Wenliang

    1992-01-01

    A square wave shape is used in the Pestorius algorithm to calculate the risetime of a step shock in the atmosphere. These results agree closely with steady shock calculations. The healing distance of perturbed shocks due to finite wave effects is then investigated for quasi-steady shocks. Perturbed 100 Pa shocks require on the order of 1.0 km travel distance to return to within 10 percent of their steady shock risetime. For 30 Pa shocks, the minimum recovery distance increases to 3.0 km. It is unlikely that finite wave effects can remove the longer risetimes and irregular features introduced into the sonic boom by turbulent scattering in the planetary boundary layer.

  11. IPShocks: Database of Interplanetary Shock Waves

    NASA Astrophysics Data System (ADS)

    Isavnin, Alexey; Lumme, Erkka; Kilpua, Emilia; Lotti, Mikko; Andreeova, Katerina; Koskinen, Hannu; Nikbakhsh, Shabnam

    2016-04-01

    Fast collisionless shocks are one of the key interplanetary structures, which have also paramount role for solar-terrestrial physics. In particular, coronal mass ejection driven shocks accelerate particles to high energies and turbulent post-shock flows may drive intense geomagnetic storms. We present comprehensive Heliospheric Shock Database (ipshocks.fi) developed and hosted at University of Helsinki. The database contains currently over 2000 fast forward and fast reverse shocks observed by Wind, ACE, STEREO, Helios, Ulysses and Cluster spacecraft. In addition, the database has search and sort tools based on the spacecraft, time range, and several key shock parameters (e.g., shock type, shock strength, shock angle), data plots for each shock and data download options. These features allow easy access to shocks and quick statistical analyses. All current shocks are identified visually and analysed using the same procedure.

  12. Compression of High Porosity Aluminum by Strong Shock Waves

    SciTech Connect

    Vildanov, V. G.; Gorshkov, M. M.; Slobodenjukov, V. M.; Borshchevsky, A. O.; Petrovtsev, A. V.

    2006-08-03

    Measuring results on shock compression of porous aluminum with initial density of {rho}00 = 0.6 g/cm3 up to pressures of 170 GPa are presented under shock wave velocity measurement scale of 40 mm. High underground explosion was used as a shock wave source. Obtained results were described in shock wave velocity (D) -- particle velocity (u) coordinates by linear dependence of D = 0.647 + 1.26 u at 4.6 {<=} u {<=} 14.8 km/s.

  13. A numerical scheme for ionizing shock waves

    SciTech Connect

    Aslan, Necdet . E-mail: naslan@yeditepe.edu.tr; Mond, Michael

    2005-12-10

    A two-dimensional (2D) visual computer code to solve the steady state (SS) or transient shock problems including partially ionizing plasma is presented. Since the flows considered are hypersonic and the resulting temperatures are high, the plasma is partially ionized. Hence the plasma constituents are electrons, ions and neutral atoms. It is assumed that all the above species are in thermal equilibrium, namely, that they all have the same temperature. The ionization degree is calculated from Saha equation as a function of electron density and pressure by means of a nonlinear Newton type root finding algorithms. The code utilizes a wave model and numerical fluctuation distribution (FD) scheme that runs on structured or unstructured triangular meshes. This scheme is based on evaluating the mesh averaged fluctuations arising from a number of waves and distributing them to the nodes of these meshes in an upwind manner. The physical properties (directions, strengths, etc.) of these wave patterns are obtained by a new wave model: ION-A developed from the eigen-system of the flux Jacobian matrices. Since the equation of state (EOS) which is used to close up the conservation laws includes electronic effects, it is a nonlinear function and it must be inverted by iterations to determine the ionization degree as a function of density and temperature. For the time advancement, the scheme utilizes a multi-stage Runge-Kutta (RK) algorithm with time steps carefully evaluated from the maximum possible propagation speed in the solution domain. The code runs interactively with the user and allows to create different meshes to use different initial and boundary conditions and to see changes of desired physical quantities in the form of color and vector graphics. The details of the visual properties of the code has been published before (see [N. Aslan, A visual fluctuation splitting scheme for magneto-hydrodynamics with a new sonic fix and Euler limit, J. Comput. Phys. 197 (2004) 1

  14. Impact-shocked zircons: Discovery of shock-induced textures reflecting increasing degrees of shock metamorphism

    NASA Technical Reports Server (NTRS)

    Bohor, B. F.; Betterton, W. J.; Krogh, T. E.

    1993-01-01

    Textural effects specifically characteristic of shock metamorphism in zircons from impact environments have not been reported previously. However, planar deformation features (PDF) due to shock metamorphism are well documented in quartz and other mineral grains from these same environments. An etching technique was developed that allows scanning electron microscope (SEM) visualization of PDF and other probable shock-induced textural features, such as granular (polycrystalline) texture, in zircons from a variety of impact shock environments. These textural features in shocked zircons from K/T boundary distal ejecta form a series related to increasing degrees of shock that should correlate with proportionate resetting of the U-Pb isotopic system.

  15. Impact-shocked zircons: discovery of shock-induced textures reflecting increasing degrees of shock metamorphism

    USGS Publications Warehouse

    Bohor, B.F.; Betterton, W.J.; Krogh, T.E.

    1993-01-01

    Textural effects specifically characteristic of shock metamorphism in zircons from impact environments have not been reported previously. However, planar deformation features (PDF) due to shock metamorphism are well documented in quartz and other mineral grains from these same environments. An etching technique was developed that allows SEM visualization of PDF and other probable shock-induced textural features, such as granular (polycrystalline) texture, in zircons from a variety of impact shock environments. These textural features in shocked zircons from K/T boundary distal ejecta form a series related to increasing degrees of shock that should correlate with proportionate resetting of the UPb isotopic system. ?? 1993.

  16. Shock Waves for Possible Application in Regenerative Medicine

    NASA Astrophysics Data System (ADS)

    Hosseini, S. H. R.; Nejad, S. Moosavi; Akiyama, H.

    The paper reports experimental study of underwater shock waves effects in modification and possible control of embryonic stem cell differentiation and proliferation. The study is motivated by its application in regenerativemedicine. Underwater shock waves have been of interest for various scientific, industrial, and medical applications.

  17. Optical distortion in the field of a lithotripter shock wave

    NASA Astrophysics Data System (ADS)

    Carnell, M. T.; Emmony, D. C.

    1995-10-01

    The schlieren observation of cavitation phenomena produced in the tail of a lithotripter shock wave has indicated the presence of some interesting features. The images produced appear to indicate that cavitation transients in the field of a shock wave propagate nonsymmetrically; this is not the case. The apparent lack of symmetry exhibited by the primary cavitation transients is due to a complex optical lensing effect, which is brought about by the change in refractive index associated with the pressure profile of the shock wave. Objects seen through or immersed in the shock-wave field of an electromagnetic acoustic transducer, such as cavitation, appear highly distorted because of the strong positive and negative lensing effects of the compression and rarefaction cycles of the shock wave. A modification of the schlieren technique called the scale method has been used to model the distortion introduced by the shock wave and consequently explain the cavitation distortion. The technique has also been used to quantitatively analyze and partially reconstruct the lithotripter shock wave. The combination of schlieren and scale imaging gives more information about the refractive index field and therefore the shock-wave structure itself.

  18. Tandem shock wave cavitation enhancement for extracorporeal lithotripsy.

    PubMed

    Loske, Achim M; Prieto, Fernando E; Fernandez, Francisco; van Cauwelaert, Javier

    2002-11-21

    Extracorporeal shock wave lithotripsy (ESWL) has been successful for more than twenty years in treating patients with kidney stones. Hundreds of underwater shock waves are generated outside the patient's body and focused on the kidney stone. Stones fracture mainly due to spalling, cavitation and layer separation. Cavitation bubbles are produced in the vicinity of the stone by the tensile phase of each shock wave. Bubbles expand, stabilize and finally collapse violently, creating stone-damaging secondary shock waves and microjets. Bubble collapse can be intensified by sending a second shock wave a few hundred microseconds after the first. A novel method of generating two piezoelectrically generated shock waves with an adjustable time delay between 50 and 950 micros is described and tested. The objective is to enhance cavitation-induced damage to kidney stones during ESWL in order to reduce treatment time. In vitro kidney stone model fragmentation efficiency and pressure measurements were compared with those for a standard ESWL system. Results indicate that fragmentation efficiency was significantly enhanced at a shock wave delay of about 400 and 250 micros using rectangular and spherical stone phantoms, respectively. The system presented here could be installed in clinical devices at relatively low cost, without the need for a second shock wave generator. PMID:12476975

  19. Optical observation of shock waves and cavitation bubbles in high intensity laser-induced shock processes

    SciTech Connect

    Marti-Lopez, L.; Ocana, R.; Porro, J. A.; Morales, M.; Ocana, J. L.

    2009-07-01

    We report an experimental study of the temporal and spatial dynamics of shock waves, cavitation bubbles, and sound waves generated in water during laser shock processing by single Nd:YAG laser pulses of nanosecond duration. A fast ICCD camera (2 ns gate time) was employed to record false schlieren photographs, schlieren photographs, and Mach-Zehnder interferograms of the zone surrounding the laser spot site on the target, an aluminum alloy sample. We recorded hemispherical shock fronts, cylindrical shock fronts, plane shock fronts, cavitation bubbles, and phase disturbance tracks.

  20. Plasma Shock Wave Modification Experiments in a Temperature Compensated Shock Tube

    NASA Technical Reports Server (NTRS)

    Vine, Frances J.; Mankowski, John J.; Saeks, Richard E.; Chow, Alan S.

    2003-01-01

    A number of researchers have observed that the intensity of a shock wave is reduced when it passes through a weakly ionized plasma. While there is little doubt that the intensity of a shock is reduced when it propagates through a weakly ionized plasma, the major question associated with the research is whether the reduction in shock wave intensity is due to the plasma or the concomitant heating of the flow by the plasma generator. The goal of this paper is to describe a temperature compensated experiment in a "large" diameter shock tube with an external heating source, used to control the temperature in the shock tube independently of the plasma density.

  1. On cylindrically converging shock waves shaped by obstacles

    SciTech Connect

    Eliasson, V; Henshaw, W D; Appelo, D

    2007-07-16

    Motivated by recent experiments, numerical simulations were performed of cylindrically converging shock waves. The converging shocks impinged upon a set of zero to sixteen regularly space obstacles. For more than two obstacles the resulting diffracted shock fronts formed polygonal shaped patterns near the point of focus. The maximum pressure and temperature as a function of number of obstacles were studied. The self-similar behavior of cylindrical, triangular and square-shaped shocks were also investigated.

  2. Laser control of filament-induced shock wave in water

    NASA Astrophysics Data System (ADS)

    Potemkin, F. V.; Mareev, E. I.; Podshivalov, A. A.; Gordienko, V. M.

    2014-09-01

    We discovered that tight focusing of Cr:forsterite femtosecond laser radiation in water provides the unique opportunity of long filament generation. The filament becomes a source of numerous spherical shock waves whose radius tends to saturate with the increase of energy. These overlapping waves create a contrast cylindrical shock wave. The laser-induced shock wave parameters such as shape, amplitude and speed can be effectively controlled by varying energy and focusing geometry of the femtosecond pulse. Aberrations added to the optical scheme lead to multiple dotted plasma sources for shock wave formation, spaced along the optical axis. Increasing the laser energy launches filaments at each dot that enhance the length of the entire filament and as a result, the shock impact on the material.

  3. Shock wave convergence in water with parabolic wall boundaries

    SciTech Connect

    Yanuka, D.; Shafer, D.; Krasik, Ya.

    2015-04-28

    The convergence of shock waves in water, where the cross section of the boundaries between which the shock wave propagates is either straight or parabolic, was studied. The shock wave was generated by underwater electrical explosions of planar Cu wire arrays using a high-current generator with a peak output current of ∼45 kA and rise time of ∼80 ns. The boundaries of the walls between which the shock wave propagates were symmetric along the z axis, which is defined by the direction of the exploding wires. It was shown that with walls having a parabolic cross section, the shock waves converge faster and the pressure in the vicinity of the line of convergence, calculated by two-dimensional hydrodynamic simulations coupled with the equations of state of water and copper, is also larger.

  4. The Role of Large Amplitude Upstream Low-frequency Waves in the Generation of Superthermal Ions at a Quasi-parallel Collisionless Shock: Cluster Observations

    NASA Astrophysics Data System (ADS)

    Wu, Mingyu; Hao, Yufei; Lu, Quanming; Huang, Can; Guo, Fan; Wang, Shui

    2015-07-01

    The superthermal ions at a quasi-parallel collisionless shock are considered to be generated during the reformation of the shock. Recently, hybrid simulations of a quasi-parallel shock have shown that during the reformation of a quasi-parallel shock the large-amplitude upstream low-frequency waves can trap the reflected ions at the shock front when they try to move upstream, and then these reflected ions can be accelerated several times to become superthermal ions. In this paper, with the Cluster observations of a quasi-parallel shock event, the relevance between the large-amplitude upstream low-frequency waves and the superthermal ions (about several keV) have been studied. The observations clearly show that the differential energy flux of superthermal ions in the upstream region is modulated by the upstream low-frequency waves, and the maxima of the differential energy flux are usually located between the peaks of these waves (including the shock front and the peak of the upstream wave just in front of the shock front). These superthermal ions are considered to originate from the reflected ions at the shock front, and the modulation is caused due to the trapping of the reflected ions between the upstream waves or the upstream waves and the shock front when these reflected ions try to travel upstream. It verifies the results from hybrid simulations, where the upstream waves play an important role in the generation of superthermal ions in a quasi-parallel shock.

  5. Dispersive shock wave interactions and asymptotics.

    PubMed

    Ablowitz, Mark J; Baldwin, Douglas E

    2013-02-01

    Dispersive shock waves (DSWs) are physically important phenomena that occur in systems dominated by weak dispersion and weak nonlinearity. The Korteweg-de Vries (KdV) equation is the universal model for systems with weak dispersion and weak, quadratic nonlinearity. Here we show that the long-time-asymptotic solution of the KdV equation for general, steplike data is a single-phase DSW; this DSW is the "largest" possible DSW based on the boundary data. We find this asymptotic solution using the inverse scattering transform and matched-asymptotic expansions. So while multistep data evolve to have multiphase dynamics at intermediate times, these interacting DSWs eventually merge to form a single-phase DSW at large time. PMID:23496590

  6. Spectroscopy During Laser Induced Shock Wave Lithotripsy

    NASA Astrophysics Data System (ADS)

    Engelhardt, R.; Meyer, W.; Hering, P.

    1988-06-01

    In the course of laser induced shock wave lithotripsy (LISL) by means of a flashlamp pumped dye laser a plasma is formed on the stone's surface. Spectral analysis of the plasma flash leads to chemical stone analysis during the procedure. A time resolved integral analysis of scattered and laser induced fluorescence light makes stone detection possible and avoids tissue damage. We used a 200 μm fiber to transmit a 2 μs, 50 mJ pulse to the stone's surface and a second 200 μ fiber for analysis. This transmission system is small and flexible enough for controlled endoscopic use in the treatment of human ureter or common bile duct stones. Under these conditions the stone selective effect of lasertripsy leads only to minor tissue injury.

  7. Modelling Shock Waves in Composite Materials

    NASA Astrophysics Data System (ADS)

    Vignjevic, Rade; Campbell, J. C.; Bourne, N.; Matic, Ognjen; Djordjevic, Nenad

    2007-12-01

    Composite materials have been of significant interest due to widespread application of anisotropic materials in aerospace and civil engineering problems. For example, composite materials are one of the important types of materials in the construction of modern aircraft due to their mechanical properties. The strain rate dependent mechanical behaviour of composite materials is important for applications involving impact and dynamic loading. Therefore, we are interested in understanding the composite material mechanical properties and behaviour for loading rates between quasistatic and 1×108 s-1. This paper investigates modelling of shock wave propagation in orthotropic materials in general and a specific type of CFC composite material. The determination of the equation of state and its coupling with the rest of the constitutive model for these materials is presented and discussed along with validation from three dimensional impact tests.

  8. Shock-wave properties of soda-lime glass

    SciTech Connect

    Grady, D.E.; Chhabildas, L.C.

    1996-11-01

    Planar impact experiments and wave profile measurements provided single and double shock equation of state data to 30 GPa. Both compression wave wave profile structure and release wave data were used to infer time-dependent strength and equation of state properties for soda-lime glass.

  9. Detecting Fragmentation of Kidney Stones in Lithotripsy by Means of Shock Wave Scattering

    NASA Astrophysics Data System (ADS)

    Sapozhnikov, Oleg A.; Trusov, Leonid A.; Owen, Neil R.; Bailey, Michael R.; Cleveland, Robin O.

    2006-05-01

    Although extracorporeal shock wave lithotripsy (a procedure of kidney stone comminution using focused shock waves) has been used clinically for many years, a proper monitoring of the stone fragmentation is still undeveloped. A method considered here is based on recording shock wave scattering signals with a focused receiver placed far from the stone, outside the patient body. When a fracture occurs in the stone or the stone becomes smaller, the elastic waves in the stone will propagate differently (e.g. shear waves will not cross a fracture) which, in turn, will change the scattered acoustic wave in the surrounding medium. Theoretical studies of the scattering phenomenon are based on a linear elastic model to predict shock wave scattering by a stone, with and without crack present in it. The elastic waves in the stone and the nearby liquid were modeled using a finite difference time domain approach. The subsequent acoustic propagation of the scattered waves into the far-field was calculated using the Helmholtz-Kirchhoff integral. Experimental studies were conducted using a research electrohydraulic lithotripter that produced the same acoustic output as an unmodified Dornier HM3 clinical lithotripter. Artificial stones, made from Ultracal-30 gypsum and acrylic, were used as targets. The stones had cylindrical shape and were positioned co-axially with the lithotripter axis. The scattered wave was measured by focused broadband PVDF hydrophone. It was shown that the size of the stone noticeably changed the signature of the reflected wave.

  10. A new shock wave assisted sandalwood oil extraction technique

    NASA Astrophysics Data System (ADS)

    Arunkumar, A. N.; Srinivasa, Y. B.; Ravikumar, G.; Shankaranarayana, K. H.; Rao, K. S.; Jagadeesh, G.

    A new shock wave assisted oil extraction technique from sandalwood has been developed in the Shock Waves Lab, IISc, Bangalore. The fragrant oil extracted from sandalwood finds variety of applications in medicine and perfumery industries. In the present method sandal wood specimens (2.5mm diameter and 25mm in length)are subjected to shock wave loading (over pressure 15 bar)in a constant area shock tube, before extracting the sandal oil using non-destructive oil extraction technique. The results from the study indicates that both the rate of extraction as well as the quantity of oil obtained from sandal wood samples exposed to shock waves are higher (15-40 percent) compared to non-destructive oil extraction technique. The compressive squeezing of the interior oil pockets in the sandalwood specimen due to shock wave loading appears to be the main reason for enhancement in the oil extraction rate. This is confirmed by the presence of warty structures in the cross-section and micro-fissures in the radial direction of the wood samples exposed to shock waves in the scanning electron microscopic investigation. In addition the gas chromatographic studies do not show any change in the q uality of sandal oil extracted from samples exposed to shock waves.

  11. The von Neumann paradox in weak shock reflection

    NASA Astrophysics Data System (ADS)

    Zakharian, A. R.; Brio, M.; Hunter, J. K.; Webb, G. M.

    2000-11-01

    We present a numerical solution of the Euler equations of gas dynamics for a weak-shock Mach reflection in a half-space. In our numerical solutions, the incident, reflected, and Mach shocks meet at a triple point, and there is a supersonic patch behind the triple point, as proposed by Guderley. A theoretical analysis supports the existence of an expansion fan at the triple point, in addition to the three shocks. This solution is in complete agreement with the numerical solution of the unsteady transonic small-disturbance equations obtained by Hunter & Brio (2000), which provides an asymptotic description of a weak-shock Mach reflection. The supersonic patch is extremely small, and this work is the first time it has been resolved in a numerical solution of the Euler equations. The numerical solution uses six levels of grid refinement around the triple point. A delicate combination of numerical techniques is required to minimize both the effects of numerical diffusion and the generation of numerical oscillations at grid interfaces and shocks.

  12. Diffraction of a shock into an expansion wavefront for the transonic self-similar nonlinear wave system in two space dimensions

    NASA Astrophysics Data System (ADS)

    Jang, Juhi; Kim, Eun Heui

    2016-01-01

    We consider a configuration where a planar shock reflects and diffracts as it hits a semi-infinite rigid screen. The diffracted reflected shock meets the diffracted expansion wave, created by the incident shock that does not hit the screen, and changes continuously from a shock into an expansion. The governing equation changes its type and becomes degenerate as the wave changes continuously from a shock to an expansion. Furthermore the governing equation has multiple free boundaries (transonic shocks) and an additional degenerate sonic boundary (the expansion wave). We develop an analysis to understand the solution structure near which the shock strength approaches zero and the shock turns continuously into an expansion wavefront, and show the existence of the global solution to this configuration for the nonlinear wave system. Moreover we provide an asymptotic analysis to estimate the position of the change of the wave, and present intriguing numerical results.

  13. A numerical study of shock wave diffraction by a circular cylinder

    NASA Technical Reports Server (NTRS)

    Yang, J.-Y.; Liu, Y.; Lomax, H.

    1986-01-01

    The nonstationary shock wave diffraction patterns generated by a blast wave impinging on a circular cylinder are numerically simulated using a second-order hybrid upwind method for solving the two-dimensional inviscid compressible Euler equations of gasdynamics. The complete diffraction patterns, including the transition from regular to Mach reflection, trajectory of the Mach triple point and the complex shock-on-shock interaction at the wake region resulting from the Mach shocks collision behind the cylinder are reported in detail. Pressure-time history and various contour plots are also included. Comparison between the work of Bryson and Gross (1961) which included both experimental schlieren pictures and theoretical calculations using Whitham's ray-shock theory and results of the present finite difference computation indicate good agreement in every aspect except for some nonideal gas and viscous effects which are not accounted for by the Euler equations.

  14. Weak-wave analysis of shock interaction with a slipstream

    NASA Technical Reports Server (NTRS)

    Barger, Raymond L.

    1988-01-01

    A weak wave analysis of shock interaction with a slipstream is presented. The theory is compared to that for the acoustic case and to the exact nonlinear analysis. Sample calculations indicate that the weak wave theory yields a good approximation to the exact solution when the shock waves are sufficiently weak that the associated entropy increase is negligible. A qualitative discussion of the case of counterflowing streams is also included.

  15. Shock wave loading of a magnetic guide

    NASA Astrophysics Data System (ADS)

    Kindt, L.

    2011-10-01

    velocities and a shock wave is created between the two velocity regions. In order to conserve number of particle, momentum and enthalpy the density of the atomic beam passing through the shock wave must increase. We have build such a shock wave in an atomic beam and observed the density increase due to this. As an extra feature having a subsonic beam on a downward slope adds an extra density increase due to gravitational compression. Loading ultra cold atoms into a 3D trap from the dense subsonic beam overcomes the problem with 2D cooling and thermal conductivity. This was done and evaporative cooling was applied creating an unprecedented large number rubidium BEC.

  16. Medical applications and bioeffects of extracorporeal shock waves

    NASA Astrophysics Data System (ADS)

    Delius, M.

    1994-09-01

    Lithotripter shock waves are pressure pulses of microsecond duration with peak pressures of 35 120 MPa followed by a tensile wave. They are an established treatment modality for kidney and gallstone disease. Further applications are pancreatic and salivary stones, as well as delayed fracture healing. The latter are either on their way to become established treatments or are currently under investigation. Shock waves generate tissue damage as a side effect which has been extensively investigated in the kidney, the liver, and the gallbladder. The primary adverse effects are local destruction of blood vessels, bleedings, and formation of blood clots in vessels. Investigations on the mechanism of shock wave action revealed that lithotripters generate cavitation both in vitro and in vivo. An increase in tissue damage at higher pulse administration rates, and also at shock wave application with concomitant gas bubble injection suggested that cavitation is a major mechanism of tissue damage. Disturbances of the heart rhythm and excitation of nerves are further biological effects of shock waves; both are probably also mediated by cavitation. On the cellular level, shock waves induce damage to cell organelles; its extent is related to their energy density. They also cause a transient increase in membrane permeability which does not lead to cell death. Administered either alone or in combination with drugs, shock waves have been shown to delay the growth of small animal tumors and even induce tumor remissions. While the role of cavitation in biological effects is widely accepted, the mechanism of stone fragmentation by shock waves is still controversial. Cavitation is detected around the stone and hyperbaric pressure suppresses fragmentation; yet major cracks are formed early before cavitation bubble collapse is observed. The latter has been regarded as evidence for a direct shock wave effect.

  17. Dynamics of concerted bubble cluster collapse in shock wave lithotripsy

    NASA Astrophysics Data System (ADS)

    Pishchalnikov, Yuri A.; McAteer, James A.; Evan, Andrew P.; Sapozhnikov, Oleg A.; Cleveland, Robin O.; Colonius, Tim; Bailey, Michael R.; Crum, Lawrence A.

    2003-10-01

    Cavitation bubble cluster collapse at the surface of artificial kidney stones during shock wave lithotripsy was investigated in vitro by means of multiframe high-speed photography, passive cavitation detection (PCD), and pressure waveform measurements using a fiber-optic probe hydrophone (FOPH). It was observed that after the passage of the lithotripter shock pulse the stone was covered by numerous individual bubbles. During their growth phase the bubbles coalesced into bubble clusters, with the biggest cluster at the proximal face of the stone. High-speed camera images suggested that cluster collapse started at the periphery and ended with a violent collapse in a small region in the center of the surface of the stone. Shadowgraphy resolved numerous secondary shock waves emitted during this focused collapse. Shock wave emission during cluster collapse was confirmed by PCD. Measurement with the FOPH showed that these shock waves were typically of short duration (0.2 μs). The majority of the shock waves emanating from cluster collapse were low amplitude but some shock waves registered amplitudes on the order of the incident shock pulse (tens of MPa). [Work supported by NIH DK43881, DK55674.

  18. The Observational Consequences of Proton-Generated Waves at Shocks

    NASA Technical Reports Server (NTRS)

    Reames, Donald V.

    2000-01-01

    In the largest solar energetic particle (SEP) events, acceleration takes place at shock waves driven out from the Sun by fast coronal mass ejections. Protons streaming away from strong shocks generate Alfven waves that trap particles in the acceleration region, limiting outflowing intensities but increasing the efficiency of acceleration to higher energies. Early in the events, with the shock still near the Sun, intensities at 1 AU are bounded and spectra are flattened at low energies. Elements with different charge-to-mass ratios, Q/A, differentially probe the wave spectra near shocks, producing abundance ratios that vary in space and time. An initial rise in He/H, while Fe/O declines, is a typical symptom of the non-Kolmogorov wave spectra in the largest events. Strong wave generation can cause cross-field scattering near the shock and unusually rapid reduction in anisotropies even far from the shock. At the highest energies, shock spectra steepen to form a "knee." For protons, this spectral knee can vary from approx. 10 MeV to approx. 1 GeV depending on shock conditions for wave growth. In one case, the location of the knee scales approximately as Q/A in the energy/nucleon spectra of other species.

  19. Schlieren imaging of shock waves from a trumpet

    NASA Astrophysics Data System (ADS)

    Pandya, Brian H.; Settles, Gary S.; Miller, James D.

    2003-12-01

    A sensitive, large-aperture schlieren optical instrument is applied to observe gas-dynamic phenomena at the exit of a trumpet. Shock waves are seen, especially for loud, high-pitched trumpet notes, and several illustrations are given. Microphone waveforms are given for representative examples. These shock waves arise from the shock-tube-like effect of the performer's intermittent breath pressure driving the cylindrical duct of the trumpet, and are the result of cumulative nonlinear acoustic propagation inside the trumpet bore. They are, however, very weak, traveling only marginally above the acoustic speed. In the 118-124 peak dB(A) range, they are near the weak limit of shock wave visibility by schlieren optics. The schlieren evidence confirms that the frequency of the emitted shock waves corresponds to the frequency of the note being played. Ancillary laminar and turbulent jet phenomena associated with the performer's breath are also visible in the images.

  20. Kinematical Compatibility Conditions for Vorticity Across Shock Waves

    NASA Astrophysics Data System (ADS)

    Baty, Roy

    2015-11-01

    This work develops the general kinematical compatibility conditions for vorticity across arbitrary shock waves in compressible, inviscid fluids. The vorticity compatibility conditions are derived from the curl of the momentum equation using singular distributions defined on two-dimensional shock wave surfaces embedded in three-dimensional flow fields. The singular distributions are represented as generalized differential operators concentrated on moving shock wave surfaces. The derivation of the compatibility conditions for vorticity requires the application of second-order generalized derivatives and elementary tensor algebra. The well-known vorticity jump conditions across a shock wave are then shown to follow from the general kinematical compatibility conditions for vorticity by expressing the flow field velocity in vectorial components normal and tangential to a shock surface.

  1. Schlieren imaging of shock waves from a trumpet.

    PubMed

    Pandya, Brian H; Settles, Gary S; Miller, James D

    2003-12-01

    A sensitive, large-aperture schlieren optical instrument is applied to observe gas-dynamic phenomena at the exit of a trumpet. Shock waves are seen, especially for loud, high-pitched trumpet notes, and several illustrations are given. Microphone waveforms are given for representative examples. These shock waves arise from the shock-tube-like effect of the performer's intermittent breath pressure driving the cylindrical duct of the trumpet, and are the result of cumulative nonlinear acoustic propagation inside the trumpet bore. They are, however, very weak, traveling only marginally above the acoustic speed. In the 118-124 peak dB(A) range, they are near the weak limit of shock wave visibility by schlieren optics. The schlieren evidence confirms that the frequency of the emitted shock waves corresponds to the frequency of the note being played. Ancillary laminar and turbulent jet phenomena associated with the performer's breath are also visible in the images. PMID:14714816

  2. Particles and waves Upstream of ICME Driven Interplanetary Shocks

    NASA Astrophysics Data System (ADS)

    Kajdic, P.; Blanco-Cano, X.; Aguilar-Rodriguez, E.; Russell, C. T.; Jian, L.; Opitz, A.; Luhmann, J. G.; Galvin, A. B.

    2011-12-01

    We use STEREO data to study interplanetary shocks driven by coronal mass ejections. We have found ultra-low frequency (ULF, f ~ 0.01 - 0.2 Hz) waves and high-frequency (HF, f ~ 1 Hz) fluctuations in regions upstream and downstream of these shocks. Some of the upstream HF fluctuations were classified as whistler waves. In the past whistler origin has been explained in terms of shock generation. The variety of waves found in the studied regions suggests that some of them may be generated by particle populations (electrons, ions) that can be unstable to different types of instabilities. In this work we study ions and electrons in regions immediately upstream of ten IP shocks of our sample. We use the STEREO SWEA data for electrons and STEREO PLASTIC data for ions. We study particle distributions in different points upstream of the shocks (anisotropies, temperatures, etc.) and investigate which of the observed waves can be generated by backstreaming particles.

  3. Fundamental structure of steady plastic shock waves in metals

    NASA Astrophysics Data System (ADS)

    Molinari, A.; Ravichandran, G.

    2004-02-01

    The propagation of steady plane shock waves in metallic materials is considered. Following the constitutive framework adopted by R. J. Clifton [Shock Waves and the Mechanical Properties of Solids, edited by J. J. Burke and V. Weiss (Syracuse University Press, Syracuse, N.Y., 1971), p. 73] for analyzing elastic-plastic transient waves, an analytical solution of the steady state propagation of plastic shocks is proposed. The problem is formulated in a Lagrangian setting appropriate for large deformations. The material response is characterized by a quasistatic tensile (compression) test (providing the isothermal strain hardening law). In addition the elastic response is determined up to second order elastic constants by ultrasonic measurements. Based on this simple information, it is shown that the shock kinetics can be quite well described for moderate shocks in aluminum with stress amplitude up to 10 GPa. Under the later assumption, the elastic response is assumed to be isentropic, and thermomechanical coupling is neglected. The model material considered here is aluminum, but the analysis is general and can be applied to any viscoplastic material subjected to moderate amplitude shocks. Comparisons with experimental data are made for the shock velocity, the particle velocity and the shock structure. The shock structure is obtained by quadrature of a first order differential equation, which provides analytical results under certain simplifying assumptions. The effects of material parameters and loading conditions on the shock kinetics and shock structure are discussed. The shock width is characterized by assuming an overstress formulation for the viscoplastic response. The effects on the shock structure of strain rate sensitivity are analyzed and the rationale for the J. W. Swegle and D. E. Grady [J. Appl. Phys. 58, 692 (1985)] universal scaling law for homogeneous materials is explored. Finally, the ability to deduce information on the viscoplastic response of

  4. Characteristics of coronal shock waves and solar type 2 radio bursts

    NASA Technical Reports Server (NTRS)

    Mann, G.; Classen, H.-T.

    1995-01-01

    In the solar corona shock waves generated by flares and/or coronal mass ejections can be observed by radio astronomical methods in terms of solar type 2 radio bursts. In dynamic radio spectra they appear as emission stripes slowly drifting from high to low frequencies. A sample of 25 solar type 2 radio bursts observed in the range of 40 - 170 MHz with a time resolution of 0.1 s by the new radiospectrograph of the Astrophvsikalisches Institut Potsdam in Tremsdorf is statistically investigated concerning their spectral features, i.e, drift rate, instantaneous bandwidth, and fundamental harmonic ratio. In-situ plasma wave measurements at interplanetary shocks provide the assumption that type 2 radio radiation is emitted in the vicinity of the transition region of shock waves. Thus, the instantaneous bandwidth of a solar type 2 radio burst would reflect the density jump across the associated shock wave. Comparing the inspection of the Rankine-Hugoniot relations of shock waves under coronal circumstances with those obtained from the observational study, solar type 2 radio bursts should be regarded to be generated by weak supercritical, quasi-parallel, fast magnetosonic shock waves in the corona.

  5. In vitro interaction of lithotripter shock waves and cytotoxic drugs.

    PubMed Central

    Gambihler, S.; Delius, M.

    1992-01-01

    The effect of a combination of lithotripter shock waves and cytotoxic drugs was examined in vitro. L1210 cells in suspension were exposed to shock waves during incubation with cislatin, doxorubicin, daunorubicin, THP-doxorubicin, or aclacinomycin. Proliferation was determined using the 3-4,5 dimethylthiazol-2,5 diphenyl tetrazolium bromide assay. Dose enhancement ratios were calculated for each drug in order to determine the effect of the additional exposure to shock waves. In addition, partition coefficients and IC50s of the drugs were determined. It was found, that the dose enhancement ratios increased for the drugs with decreasing cytotoxicity. The effect of all five drugs was enhanced by shock waves to a higher degree at 7 min incubation as compared to 50 min incubation. The effect of cisplatin was most significantly enhanced, with a dose enhancement ratio of 6.7 at 7 min incubation. The enhancement increased with the operating voltage used for generating the shock waves, and was only present when cells were exposed to shock waves during the incubation with the drug. An increase in cellular membrane permeability is proposed as the mechanism of interaction between shock waves and drugs. PMID:1637679

  6. What is a Shock Wave to an Explosive Molecule?

    SciTech Connect

    Tarver, C M

    2001-06-12

    An explosive molecule is a metastable chemical species that reacts exothermically given the correct stimulus. Impacting an explosive with a shock wave is a ''wake-up call'' or ''trigger'' which compresses and heats the molecule. The energy deposited by the shock wave must be distributed to the vibrational modes of the explosive molecule before chemical reaction can occur. If the shock pressure and temperature are high enough and last long enough, exothermic chemical decomposition can lead to the formation of a detonation wave. For gaseous, liquid, and perfect single crystal solid explosives, after an induction time, chemical reaction begins at or near the rear boundary of the charge. This induction time can be calculated by high pressure, high temperature transition state theory. A ''superdetonation'' wave travels through the preshocked explosive until it overtakes the initial shock wave and then slows to the steady state Chapman-Jouguet (C-J) velocity. In heterogeneous solid explosives, initiation of reaction occurs at ''hot spots'' created by shock compression. If there is a sufficient number of large and hot enough ''hot spots,'' these ignition sites grow creating a pressure pulse that overtakes the leading shock front causing detonation. Since the chemical energy is released well behind the leading shock front of a detonation wave, a mechanism is required for this energy to reinforce the leading shock front and maintain its overall constant velocity. This mechanism is the amplification of pressure wavelets in the reaction zone by the process of de-excitation of the initially highly vibrationally excited reaction product molecules. This process leads to the development of the three-dimensional structure of detonation waves observed for all explosives. In a detonation wave, the leading shock wave front becomes a ''burden'' for the explosive molecule to sustain by its chemical energy release.

  7. Shock Formation of Slow Magnetosonic Waves in Coronal Plumes

    NASA Technical Reports Server (NTRS)

    Cuntz, Manfred; Suess, Steve; Rose, M. Franklin (Technical Monitor)

    2000-01-01

    We investigate the height of shock formation in coronal plumes for slow magnetosonic waves. The models take into account plume geometric spreading, heat conduction, and radiative damping. The wave parameters as well as the spreading functions of the plumes and the base magnetic field strengths are given by empirical constraints mostly from Solar and Heliospheric Observatory (SOHO)/ Ultraviolet Coronograph Spectrometer (UVCS), Extreme Ultraviolet Imaging Telescope (EIT), Michelson Doppler Imager (MDI), and Large Angle Spectrometric Coronagraph (LASCO). Our models show that shock formation occurs at relatively low coronal heights, typically within 1.2 RsuN, depending on the model parameters. The shock formation is calculated using the well-established wave breaking criterion given by the intersection of C+ characteristics in the space-time plane. Our models show that shock heating by slow magnetosonic waves is expected to be relevant at most heights in solar coronal plumes, although such waves are probably not the main energy supply mechanism.

  8. Shock Formation of Slow Magnetosonic Waves in Coronal Plumes

    NASA Technical Reports Server (NTRS)

    Cuntz, Manfred; Suess, Steven T.; Rose, M. Franklin (Technical Monitor)

    2001-01-01

    We investigate the height of shock formation in coroner plumes for slow magnetosonic waves. The models take into account plume geometric spreading, heat conduction and radiative damping. The wave parameters as well as the spreading functions of the plumes and the base magnetic field strengths are given by empirical constraints mostly from Solar and Heliospheric Observatory/Ultraviolet Coronagraph Spectrometer (SOHO/UVCS). Our models show that shock formation occurs at low coronal heights, i.e., within 1.3 solar radius, depending on the model parameters. The shock formation is calculated using the well-established wave breaking condition given by the intersection of C+ characteristics in the space-time plane. Our models show that shock heating by slow magnetosonic waves is expected to be relevant at most heights in solar coronal plumes, although slow magnetosonic waves are most likely not a solely operating energy supply mechanism.

  9. Convection of a pattern of vorticity through a shock wave

    NASA Technical Reports Server (NTRS)

    Ribner, H S

    1954-01-01

    An arbitrary weak spatial distribution of vorticity can be represented in terms of plane sinusoidal shear waves of all orientations and wave lengths (Fourier integral). The analysis treats the passage of a single representative weak shear wave through a plane shock and shows refraction and modification of the shear wave with simultaneous generation of an acoustically intense sound wave. Applications to turbulence and to noise in supersonic wind tunnels are indicated.

  10. Shock Waves in a Bose-Einstein Condensate

    NASA Technical Reports Server (NTRS)

    Kulikov, Igor; Zak, Michail

    2005-01-01

    A paper presents a theoretical study of shock waves in a trapped Bose-Einstein condensate (BEC). The mathematical model of the BEC in this study is a nonlinear Schroedinger equation (NLSE) in which (1) the role of the wave function of a single particle in the traditional Schroedinger equation is played by a space- and time-dependent complex order parameter (x,t) proportional to the square root of the density of atoms and (2) the atoms engage in a repulsive interaction characterized by a potential proportional to | (x,t)|2. Equations that describe macroscopic perturbations of the BEC at zero temperature are derived from the NLSE and simplifying assumptions are made, leading to equations for the propagation of sound waves and the transformation of sound waves into shock waves. Equations for the speeds of shock waves and the relationships between jumps of velocity and density across shock fronts are derived. Similarities and differences between this theory and the classical theory of sound waves and shocks in ordinary gases are noted. The present theory is illustrated by solving the equations for the example of a shock wave propagating in a cigar-shaped BEC.

  11. High-frequency electrostatic waves near earth's bow shock

    NASA Technical Reports Server (NTRS)

    Onsager, T. G.; Holzworth, R. H.; Koons, H. C.; Bauer, O. H.; Gurnett, D. A.

    1989-01-01

    Electrostatic wave measurements from the Active Magnetospheric Particle Tracer Explorer Ion Release Module have been used to investigate the wave modes and their possible generation mechanisms in the earth's bow shock and magnetosheath. It is demonstrated that electrostatic waves are present in the bow shock and magnetosheath with frequencies above the maximum frequency for Doppler-shifted ion acoustic waves, yet below the plasma frequency. Waves in this frequency range are tentatively identified as electron beam mode waves. Data from 45 bow shock crossings are then used to investigate possible correlations between the electrostatic wave properties and the near-shock plasma parameters. The most significant relationships found are anticorrelations with Alfven Mach number and electron beta. Mechanisms which might produce electron beams in the shock and magnetosheath are discussed in terms of the correlation study results. These mechanisms include acceleration by the cross-shock electric field and by lower hybrid frequency waves. A magnetosheath 'time of flight' mechanism, in analogy to the electron foreshock region, is introduced as another possible beam generation mechanism.

  12. Entropy jump across an inviscid shock wave

    NASA Technical Reports Server (NTRS)

    Salas, Manuel D.; Iollo, Angelo

    1995-01-01

    The shock jump conditions for the Euler equations in their primitive form are derived by using generalized functions. The shock profiles for specific volume, speed, and pressure are shown to be the same, however density has a different shock profile. Careful study of the equations that govern the entropy shows that the inviscid entropy profile has a local maximum within the shock layer. We demonstrate that because of this phenomenon, the entropy, propagation equation cannot be used as a conservation law.

  13. Mechanism of fragmentation of urinary stones by underwater shock wave.

    PubMed

    Kambe, K; Kuwahara, M; Orikasa, S; Takayama, K

    1988-01-01

    The focusing of an underwater shock wave, generated by an underwater microexplosion, has been studied by several methods, such as holography, pressure measurement and pressure print. It has been shown that the shock wave could be focused within the range of a few millimeters and with an amplitude of 1 kbar. The acoustic impedances of various kinds of urinary stones were measured by the original graphical method using holographic interferrometry. The process of breaking a stone by a focused underwater shock wave was observed with high-speed cinematography. It was supposed that the main mechanism of breaking the stone is the tensile stress at the solid-water acoustic interface. PMID:3201639

  14. Constant Density Approximations for the Flow Behind Axisymmetric Shock Waves

    NASA Technical Reports Server (NTRS)

    Munson, Albert G.

    1961-01-01

    The incompressible rotational flow equations are used to obtain solutions for the flow behind axisymmetric shock waves with conic longitudinal sections. The nonlinear part of the term due to rotation is retained in the analysis. Numerical results for standoff distance and stagnation point velocity gradient are presented for the case in which the shock wave is a paraboloid, a sphere, or an oblate or prolate ellipsoid. A similarity parameter is proposed which correlates approximately the flow behind geometrically similar shock waves at different free-stream conditions.

  15. Confinement effects of shock waves on laser-induced plasma from a graphite target

    SciTech Connect

    Huang, Feiling; Liang, Peipei; Yang, Xu; Cai, Hua; Wu, Jiada; Xu, Ning; Ying, Zhifeng; Sun, Jian

    2015-06-15

    The spatial confinement effects of shock waves on the laser-induced plasma (LIP) from a graphite target in air were studied by probe beam deflection (PBD) measurements and optical emission spectroscopy (OES). A clear relationship between the confinement of the LIP by the shock wave and the effects on the LIP emission was observed, and the underlying mechanisms are discussed. PBD monitoring revealed that the laser-ablation induced shock wave could be well analogized to the shock wave generated by a point explosion and would be reflected by a block. OES measurements indicated that the optical emission of the LIP exhibited significant variations with the block placement. A first enhancement and then a fast decay of CN molecular emission as well as a suppression of carbon atomic emission were observed in the presence of the block. The results revealed that the reflected shock wave spatially confined the expansion of the LIP and compressed the LIP after encountering it, pushing back the species of the LIP and changing the density of the LIP species including luminous carbon atoms and CN molecules. It is suggested that the change of the LIP emission is attributed to the density variation of the LIP species due to the compression of the LIP and the reactions occurring in the plasma.

  16. Isentropic "Shock Waves" in Numerical Simulations of Astrophysical Problems

    NASA Astrophysics Data System (ADS)

    Bisnovatyi-Kogan, G. S.; Moiseenko, S. G.

    2016-03-01

    Strong discontinuities in solutions of the gas dynamic equations under isentropic conditions, i.e., with continuity of entropy at the discontinuity, are examined. Solutions for a standard shock wave with continuity of energy at the discontinuity are compared with those for an isentropic "shock wave." It is shown that numerical simulation of astrophysical problems in which high-amplitude shock waves are encountered (supernova explosions, modelling of jets) with conservation of entropy, rather than of energy, leads to large errors in the shock calculations. The isentropic equations of gas dynamics can be used only when there are no strong discontinuities in the solution or when the intensity of the shocks is not high and they do not significantly affect the flow.

  17. Numerical simulation of the April 24, 1981 interplanetary shock wave

    NASA Astrophysics Data System (ADS)

    Odstrcil, Dusan

    1991-06-01

    The paper deals with the application of the 1D HD computer code to the simulation of the interplanetary shock wave generated on April 24, 1981. This event is simulated, in terms of density, velocity and temperature, by a pulse introduced at 18 Rs into a steady-state solar wind. The observed data were used to specify all significant parameters of the steady-state solar wind and the introduced shock wave. The short duration of the input pulse caused the shock wave to be initially highly decelerated. Special attention is given to the type II radio emission associated with this shock and measured by the Czechoslovak-Soviet experiment aboard the Prognoz-8 satellite. From the given analysis it follows that the emission is generated in front of the shock front at the blended fundamental and harmonic plasma frequency.

  18. Low Frequency Waves at and Upstream of Collisionless Shocks

    NASA Astrophysics Data System (ADS)

    Wilson, L. B.

    2016-02-01

    This chapter focuses on the range of low frequency electromagnetic modes observed at and upstream of collisionless shocks in the heliosphere. It discusses a specific class of whistler mode wave observed immediately upstream of collisionless shock ramps, called a whistler precursor. Though these modes have been (and are often) observed upstream of quasi-parallel shocks, the authors limit their discussion to those observed upstream of quasi-perpendicular shocks. The chapter discusses the various ion velocity distributions observed at and upstream of collisionless shocks. It also introduces some terminology and relevant instabilities for ion foreshock waves. The chapter discusses the most common ultra-low frequency (ULF) wave types, their properties, and their free energy sources. It discusses modes that are mostly Alfvénic (i.e., mostly transverse but can be compressive) in nature.

  19. Viscous solution of the triple-shock reflection problem

    NASA Astrophysics Data System (ADS)

    Lau-Chapdelaine, S. S.-M.; Radulescu, M. I.

    2016-07-01

    The reflection of a triple-shock configuration was studied numerically in two dimensions using the Navier-Stokes equations. The flow field was initialized using three shock theory, and the reflection of the triple point on a plane of symmetry was studied. The conditions simulated a stoichiometric methane-oxygen detonation cell at low pressure on time scales preceding ignition when the gas was assumed to be inert. Viscosity was found to play an important role on some shock reflection mechanisms believed to accelerate reaction rates in detonations when time scales are small. A small wall jet was present in the double Mach reflection and increased in size with Reynolds number, eventually forming a small vortex. Kelvin-Helmholtz instabilities were absent, and there was no Mach stem bifurcation at Reynolds numbers corresponding to when the Mach stem had travelled distances on the scale of the induction length. Kelvin-Helmholtz instabilities are found to not likely be a source of rapid reactions in detonations at time scales commensurate with the ignition delay behind the Mach stem.

  20. Shock wave perturbation decay in granular materials

    SciTech Connect

    Vogler, Tracy J.

    2015-11-05

    A technique in which the evolution of a perturbation in a shock wave front is monitored as it travels through a sample is applied to granular materials. Although the approach was originally conceived as a way to measure the viscosity of the sample, here it is utilized as a means to probe the deviatoric strength of the material. Initial results for a tungsten carbide powder are presented that demonstrate the approach is viable. Simulations of the experiments using continuum and mesoscale modeling approaches are used to better understand the experiments. The best agreement with the limited experimental data is obtained for the mesoscale model, which has previously been shown to give good agreement with planar impact results. The continuum simulations indicate that the decay of the perturbation is controlled by material strength but is insensitive to the compaction response. Other sensitivities are assessed using the two modeling approaches. The simulations indicate that the configuration used in the preliminary experiments suffers from certain artifacts and should be modified to remove them. As a result, the limitations of the current instrumentation are discussed, and possible approaches to improve it are suggested.

  1. Shock wave perturbation decay in granular materials

    DOE PAGESBeta

    Vogler, Tracy J.

    2015-11-05

    A technique in which the evolution of a perturbation in a shock wave front is monitored as it travels through a sample is applied to granular materials. Although the approach was originally conceived as a way to measure the viscosity of the sample, here it is utilized as a means to probe the deviatoric strength of the material. Initial results for a tungsten carbide powder are presented that demonstrate the approach is viable. Simulations of the experiments using continuum and mesoscale modeling approaches are used to better understand the experiments. The best agreement with the limited experimental data is obtainedmore » for the mesoscale model, which has previously been shown to give good agreement with planar impact results. The continuum simulations indicate that the decay of the perturbation is controlled by material strength but is insensitive to the compaction response. Other sensitivities are assessed using the two modeling approaches. The simulations indicate that the configuration used in the preliminary experiments suffers from certain artifacts and should be modified to remove them. As a result, the limitations of the current instrumentation are discussed, and possible approaches to improve it are suggested.« less

  2. Observation of cavitation during shock wave lithotripsy

    NASA Astrophysics Data System (ADS)

    Bailey, Michael R.; Crum, Lawrence A.; Pishchalnikov, Yuri A.; McAteer, James A.; Pishchalnikova, Irina V.; Evan, Andrew P.; Sapozhnikov, Oleg A.; Cleveland, Robin O.

    2005-04-01

    A system was built to detect cavitation in pig kidney during shock wave lithotripsy (SWL) with a Dornier HM3 lithotripter. Active detection, using echo on B-mode ultrasound, and passive cavitation detection (PCD), using coincident signals on confocal, orthogonal receivers, were equally sensitive and were used to interrogate the renal collecting system (urine) and the kidney parenchyma (tissue). Cavitation was detected in urine immediately upon SW administration in urine or urine plus X-ray contrast agent, but in tissue, cavitation required hundreds of SWs to initiate. Localization of cavitation was confirmed by fluoroscopy, sonography, and by thermally marking the kidney using the PCD receivers as high intensity focused ultrasound sources. Cavitation collapse times in tissue and native urine were about the same but less than in urine after injection of X-ray contrast agent. Cavitation, especially in the urine space, was observed to evolve from a sparse field to a dense field with strong acoustic collapse emissions to a very dense field that no longer produced detectable collapse. The finding that cavitation occurs in kidney tissue is a critical step toward determining the mechanisms of tissue injury in SWL. [Work sup ported by NIH (DK43881, DK55674, FIRCA), ONRIFO, CRDF and NSBRI SMS00203.

  3. Shock wave synthesis of aluminium nitride with rocksalt structure

    NASA Astrophysics Data System (ADS)

    Keller, K.; Schlothauer, T.; Schwarz, M.; Heide, G.; Kroke, E.

    2012-03-01

    The high pressure phase of aluminium nitride with rocksalt structure (rs) is a ceramic with high potential and a challenging material to investigate. The rs-AlN was synthesised and recovered by shock wave experiments using the flyer-plate method with multiple reflections at peak pressures between 15 and 43 GPa. Successful syntheses were carried out using AlN nanopowder with ambient pressure wurtzite structure (w-AlN) as starting material. The high pressure modification could, however, not be obtained when starting from submicron w-AlN. The recovery of rs-AlN is sensitive to the synthesis conditions as these influence the reconversion of rs-AlN to w-AlN.

  4. Interaction Between Oblique Whistlers and Reflected Ions in a Supercritical Quasiperpendicular Shock: Evidences from Themis

    NASA Astrophysics Data System (ADS)

    Muschietti, L.; Hull, A. J.

    2014-12-01

    Whistler waves are characteristic of collisionless fast mode shocks. Recent Polar observations at Earth's bow shock have revealed copious whistlers in the lower-hybrid frequency range [Hull et al., JGR, 2012]. The waves have wavelengths comparable to the ion inertia length and propagate obliquely to both the magnetic field B0 and the shock normal. Earth's bow shock being supercritical, reflected ions play a fundamental role and, in particular, determine its macrostructure which consists of a foot, a ramp, and an overshoot region. Here, we investigate the possible interaction between the oblique whistlers and the reflected ions in the shock's foot. The problem considered is characterized by a double anisotropy: one defined by the direction of B0, the other by that of the reflected beam. Let Ψ be the plane defined by these two directions, presumably the magnetic coplanarity plane. The Cerenkov resonance condition reads ω = k Ure sin θbk cos ψvk , where Ure denotes the drift of the beam of reflected ions seen in the solar wind frame, θbk is the angle between the wavevector and B0, and ψvk is the angle between the wavevector and the plane Ψ. We exploit Themis burst mode and its three-axis field measurements in order to simultaneously characterize the whistlers (wavevector direction and module) and the ion beam (velocity direction and module). The resonance condition above is then examined in this light. Modelling the ion beam, we use our electromagnetic dispersion code [see companion paper in this session] to compute the linear characteristics of the oblique whistlers that can be excited and compare them with the observations. Moreover, waveforms and hodograms obtained from an electromagnetic PIC simulation are also compared with Themis measurements.

  5. Whistler wave bursts upstream of the Uranian bow shock

    NASA Technical Reports Server (NTRS)

    Smith, Charles W.; Goldstein, Melvyn L.; Wong, Hung K.

    1989-01-01

    Observations of magnetic field wave bursts upstream of the Uranian bow shock are reported which were recorded prior to the inbound shock crossing. Three wave types are identified. One exhibits a broad spectral enhancement from a few millihertz to about 50 mHz and is seen from 17 to 10 hr prior to the inbound shock crossing. It is argued that these waves are whistler waves that have propagated upstream from the shock. A second wave type has a spacecraft frame frequency between 20 and 40 mHz, is seen only within or immediately upstream of the shock pedestal, is right-hand polarized in the spacecraft frame, and has a typical burst duration of 90 s. The third wave type has a spacecraft frame frequency of about 0.15 Hz, is seen exclusively within the shock pedestal, is left-hand polarized in the spacecraft frame, and has a burst duration lasting up to 4 min. It is argued that the low-frequency bursts are whistler waves with phase speed comparable to, but in excess of, the solar wind speed.

  6. An analysis of combustion studies in shock expansion tunnels and reflected shock tunnels

    NASA Technical Reports Server (NTRS)

    Jachimowski, Casimir J.

    1992-01-01

    The effect of initial nonequilibrium dissociated air constituents on the combustion of hydrogen in high-speed flows for a simulated Mach 17 flight condition was investigated by analyzing the results of comparative combustion experiments performed in a reflected shock tunnel test gas and in a shock expansion tunnel test gas. The results were analyzed and interpreted with a one-dimensional quasi-three-stream combustor code that includes finite rate combustion chemistry. The results of this study indicate that the combustion process is kinetically controlled in the experiments in both tunnels and the presence of the nonequilibrium partially dissociated oxygen in the reflected shock tunnel enhances the combustion. Methods of compensating for the effect of dissociated oxygen are discussed.

  7. Simulation of shock wave boundary layer interaction in flat channel with jet injection

    NASA Astrophysics Data System (ADS)

    Shakhan, Nurtoleu; Beketaeva, Asel; Naimanova, Altynshash

    2016-08-01

    A multispecies supersonic gas flow in the flat channel with perpendicular jet injection is numerically simulated by using the Favre-averaged Navier-Stokes equations coupled with k - ω turbulence model. High order WENO scheme is applied to approximate convective terms. During the investigation of flow physics in detail, the three shock-wave structures are observed: in the region of the jet (barrel, bow, oblique and closing shocks), on the upper boundary layer (reflection, transmitted and reattachment shocks), and new structures behind the jet on the lower boundary layer, which are analogous to the structures on the upper boundary layer.

  8. Density inhomogeneity driven electrostatic shock waves in planetary rings

    SciTech Connect

    Masood, W.; Siddiq, M.; Rizvi, H.; Haque, Q.; Hasnain, H.

    2011-05-15

    Dust inertia and background density driven dust drift shock waves are theoretically studied in a rotating planetary environment and are subsequently applied to the planetary rings where the collisional effects are pronounced. It has been found that the system under consideration admits significant shock formation if the collision frequency is of the order of or less than the rotational frequency of the Saturn's rings.

  9. Electrical instrument measures position and velocity of shock waves

    NASA Technical Reports Server (NTRS)

    Dannenberg, R. E.; Humphry, D. E.

    1971-01-01

    Instrument employs a sensor consisting of twin-electrode probe mounted in shock tube wall, with small dc voltage impressed across electrodes. Power supply, amplifier, and gate pulse generator complete the system. Instrument provides data for construction of wave diagrams, as well as measurement of shock velocity.

  10. Nonstandard jump functions for radially symmetric shock waves

    SciTech Connect

    Baty, Roy S.; Tucker, Don H.; Stanescu, Dan

    2008-10-01

    Nonstandard analysis is applied to derive generalized jump functions for radially symmetric, one-dimensional, magnetogasdynamic shock waves. It is assumed that the shock wave jumps occur on infinitesimal intervals, and the jump functions for the physical parameters occur smoothly across these intervals. Locally integrable predistributions of the Heaviside function are used to model the flow variables across a shock wave. The equations of motion expressed in nonconservative form are then applied to derive unambiguous relationships between the jump functions for the physical parameters for two families of self-similar flows. It is shown that the microstructures for these families of radially symmetric, magnetogasdynamic shock waves coincide in a nonstandard sense for a specified density jump function

  11. Nonstandard jump functions for radically symmetric shock waves

    SciTech Connect

    Baty, Roy S; Tucker, Don H; Stanescu, Dan

    2008-01-01

    Nonstandard analysis is applied to derive generalized jump functions for radially symmetric, one-dimensional, magnetogasdynamic shock waves. It is assumed that the shock wave jumps occur on infinitesimal intervals and the jump functions for the physical parameters occur smoothly across these intervals. Locally integrable predistributions of the Heaviside function are used to model the flow variables across a shock wave. The equations of motion expressed in nonconservative form are then applied to derive unambiguous relationships between the jump functions for the physical parameters for two families of self-similar flows. It is shown that the microstructures for these families of radially symmetric, magnetogasdynamic shock waves coincide in a nonstandard sense for a specified density jump function.

  12. A new class of solutions for interstellar magnetohydrodynamic shock waves

    NASA Technical Reports Server (NTRS)

    Roberge, W. G.; Draine, B. T.

    1990-01-01

    An analysis is presented of the equations of motion for steady MHD shock waves proopagating in interstellar clouds, for boundary conditions that preclude C shocks. In addition to J shocks, in which the neutral fluid component becomes subsonic at an adiabatic jump front, the equations admit a new class of solutions, called C-asterisk shocks, in which the transition to subsonic flow occurs continuously at a sonic point. Numerical methods are developed for computing the structure of J and C-asterisk shocks propagating in diffuse interstellar clouds. The effects of chemical, ionization, and recombination processes are included in this treatment. An alternative numerical method, which uses artificial viscosity to facilitate integration through sonic points, is analyzed and shown to be invalid. A set of exemplary solutions, computed for realistic shock parameters, shows that C-asterisk shocks occur for a broad range of conditions relevant to diffuse interstellar clouds.

  13. A new class of solutions for interstellar magnetohydrodynamic shock waves

    SciTech Connect

    Roberge, W.G.; Draine, B.T. Princeton Univ. Observatory, NJ )

    1990-02-01

    An analysis is presented of the equations of motion for steady MHD shock waves propagating in interstellar clouds, for boundary conditions that preclude C shocks. In addition to J shocks, in which the neutral fluid component becomes subsonic at an adiabatic jump front, the equations admit a new class of solutions, called C-asterisk shocks, in which the transition to subsonic flow occurs continuously at a sonic point. Numerical methods are developed for computing the structure of J and C-asterisk shocks propagating in diffuse interstellar clouds. The effects of chemical, ionization, and recombination processes are included in this treatment. An alternative numerical method, which uses artificial viscosity to facilitate integration through sonic points, is analyzed and shown to be invalid. A set of exemplary solutions, computed for realistic shock parameters, shows that C-asterisk shocks occur for a broad range of conditions relevant to diffuse interstellar clouds. 27 refs.

  14. Grain destruction in a supernova remnant shock wave

    SciTech Connect

    Raymond, John C.; Gaetz, Terrance J.; Ghavamian, Parviz; Williams, Brian J.; Blair, William P.; Borkowski, Kazimierz J.; Sankrit, Ravi

    2013-12-01

    Dust grains are sputtered away in the hot gas behind shock fronts in supernova remnants (SNRs), gradually enriching the gas phase with refractory elements. We have measured emission in C IV λ1550 from C atoms sputtered from dust in the gas behind a non-radiative shock wave in the northern Cygnus Loop. Overall, the intensity observed behind the shock agrees approximately with predictions from model calculations that match the Spitzer 24 μm and the X-ray intensity profiles. Thus, these observations confirm the overall picture of dust destruction in SNR shocks and the sputtering rates used in models. However, there is a discrepancy in that the C IV intensity 10'' behind the shock is too high compared with the intensities at the shock and 25'' behind it. Variations in the density, hydrogen neutral fraction, and the dust properties over parsec scales in the pre-shock medium limit our ability to test dust destruction models in detail.

  15. Grain Destruction in a Supernova Remnant Shock Wave

    NASA Technical Reports Server (NTRS)

    Raymond, John C.; Ghavamian, Parviz; Williams, Brian J.; Blair, William P.; Borkowski, Kazimierz J.; Gaetz, Terrance J.; Sankrit, Ravi

    2014-01-01

    Dust grains are sputtered away in the hot gas behind shock fronts in supernova remnants, gradually enriching the gas phase with refractory elements. We have measured emission in C IV (lambda)1550 from C atoms sputtered from dust in the gas behind a non-radiative shock wave in the northern Cygnus Loop. Overall, the intensity observed behind the shock agrees approximately with predictions from model calculations that match the Spitzer 24 micron and the X-ray intensity profiles. Thus these observations confirm the overall picture of dust destruction in SNR shocks and the sputtering rates used in models. However, there is a discrepancy in that the CIV intensity 10'' behind the shock is too high compared to the intensities at the shock and 25'' behind it. Variations in the density, hydrogen neutral fraction and the dust properties over parsec scales in the pre- shock medium limit our ability to test dust destruction models in detail.

  16. Shock waves in luminous early-type stars

    SciTech Connect

    Castor, J.I.

    1986-07-01

    Shock waves that occur in stellar atmospheres have their origin in some hydrodynamic instability of the atmosphere itself or of the stellar interior. In luminous early-type stars these two possibilities are represented by shocks due to an unstable radiatively-accelerated wind, and to shocks generated by the non-radial pulsations known to be present in many or most OB stars. This review is concerned with the structure and development of the shocks in these two cases, and especially with the mass loss that may be due specifically to the shocks. Pulsation-produced shocks are found to be very unfavorable for causing mass loss, owing to the great radiation efficiency that allows them to remain isothermal. The situation regarding radiatively-driven shocks remains unclear, awaiting detailed hydrodynamics calculations. 20 refs., 2 figs.

  17. Attenuation of shock waves propagating through nano-structured porous materials

    NASA Astrophysics Data System (ADS)

    Al-Qananwah, Ahmad K.; Koplik, Joel; Andreopoulos, Yiannis

    2013-07-01

    Porous materials have long been known to be effective in energy absorption and shock wave attenuation. These properties make them attractive in blast mitigation strategies. Nano-structured materials have an even greater potential for blast mitigation because of their high surface-to-volume ratio, a geometric parameter which substantially attenuates shock wave propagation. A molecular dynamics approach was used to explore the effects of this remarkable property on the behavior of traveling shocks impacting on solid materials. The computational setup included a moving piston, a gas region and a target solid wall with and without a porous structure. The gas and porous solid were modeled by Lennard-Jones-like and effective atom potentials, respectively. The shock wave is resolved in space and time and its reflection from a solid wall is gradual, due to the wave's finite thickness, and entails a self-interaction as the reflected wave travels through the incoming incident wave. Cases investigated include a free standing porous structure, a porous structure attached to a wall and porous structures with graded porosity. The effects of pore shape and orientation have been also documented. The results indicate that placing a nano-porous material layer in front of the target wall reduced the stress magnitude and the energy deposited inside the solid by about 30 percent, while at the same time substantially decreasing the loading rate.

  18. More efficient focusing for extracorporeal shock wave lithotripsy

    NASA Astrophysics Data System (ADS)

    Loske, Achim M.; Prieto, Fernando E.

    2001-10-01

    The purpose of this study was to generate alternative pressure waveforms in order to increase efficiency during non-invasive treatments of nephrolithiasis. Two new systems for electrohydraulic shock wave generators were tested. These devices generate two pressure pulses, instead of only one positive peak, followed by a trough, as in conventional systems. Pressure measurements and stone fragmentation efficiency were compared to that of conventional shock wave generators, using needle hydrophones and kidney-stone models.

  19. In vivo transfection of melanoma cells by lithotripter shock waves.

    PubMed

    Bao, S; Thrall, B D; Gies, R A; Miller, D L

    1998-01-15

    The potential for gene transfection during shock wave tumor therapy was evaluated by searching for shock wave-induced DNA transfer in mouse tumor cells. B16 mouse melanoma cells were cultured by standard methods and implanted s.c. in female C57BL/6 mice 10-14 days before treatment. A luciferase reporter vector was used as the DNA plasmid for intratumoral injection at 0.2 mg/ml tumor. Air at 10% of tumor volume was injected after the DNA in some tumors to enhance acoustic cavitation activity. The shock wave generation system was similar to a Dornier HM-3 lithotripter with pressure amplitudes of 24.4 MPa peak positive and 5.2 MPa peak negative. Luciferase production in isolated tumor cells was measured with a luminometer 1 day after treatment to assess gene transfer and expression. Exposure to 800 shock waves, followed by immediate isolation and culture of tumor cells for 1 day, yielded 1.1 (0.43 SE) pg/10(6) cells for plasmid injection only and 7.5 (2.5 SE) pg/10(6) cells for plasmid plus air injection. Significantly increased luciferase production, relative to shams, occurred for 200-, 400-, 800-, and 1200-shock wave treatments with plasmid and air injection. Exposure with the isolation of tumor cells delayed for a day to allow gene expression within the growing tumors gave increased luciferase production for 100- and 400-shock wave exposures without and with air injection. Gene transfer therefore can be induced during lithotripter shock wave treatment in vivo, particularly with enhanced acoustic cavitation, which supports the concept that gene and shock wave therapy might be advantageously merged. PMID:9443395

  20. Interaction of turbulent plasma flow with a hypersonic shock wave

    SciTech Connect

    Belay, K.; Valentine, J.M.; Williams, R.L.; Johnson, J.A. III

    1997-02-01

    A transient increase is observed in both the spectral energy decay rate and the degree of chaotic complexity at the interface of a shock wave and a turbulent ionized gas. Even though the gas is apparently brought to rest by the shock wave, no evidence is found either of prompt relaminarization or of any systematic influence of end-wall material thermal conductivities on the turbulence parameters. {copyright} {ital 1997 American Institute of Physics.}

  1. Temperature maxima in stable two-dimensional shock waves

    SciTech Connect

    Kum, O.; Hoover, W.G.; Hoover, C.G.

    1997-07-01

    We use molecular dynamics to study the structure of moderately strong shock waves in dense two-dimensional fluids, using Lucy{close_quote}s pair potential. The stationary profiles show relatively broad temperature maxima, for both the longitudinal and the average kinetic temperatures, just as does Mott-Smith{close_quote}s model for strong shock waves in dilute three-dimensional gases. {copyright} {ital 1997} {ital The American Physical Society}

  2. The role of extracorporeal shock wave on plantar fasciitis.

    PubMed

    Roehrig, Gregory J; Baumhauer, Judith; DiGiovanni, Benedict F; Flemister, Adolph S

    2005-12-01

    Extracorporeal shock wave therapy for chronic plantar fasciitis has been under investigation since its advent in the early 1990s. Its use has been approved by the U.S. Food and Drug Administration; however, much controversy exists surrounding its mechanism of action, treatment protocols, and clinical efficacy. This article reviews some of the existing theories, opinions, and data in an attempt to summarize the current role that shock wave therapy plays in the treatment of plantar fasciitis. PMID:16297828

  3. Efficiency of shock wave attenuation in ducts by various methods

    NASA Astrophysics Data System (ADS)

    Frolov, S. M.

    1993-02-01

    Different methods of shock wave attenuation in ducts are compared in terms of efficiency. The methods investigated include expansion of the duct cross section, the use of perforated side walls, and the use of porous screens and screen cascades. The attentuation of air shock waves is estimated by using a unified approach which provides satisfactory agreement with experimental data. Based on the results of the study, a nomogram is plotted which can be used for practical calculations.

  4. Tracking kidney stones with sound during shock wave lithotripsy

    NASA Astrophysics Data System (ADS)

    Kracht, Jonathan M.

    The prevalence of kidney stones has increased significantly over the past decades. One of the primary treatments for kidney stones is shock wave lithotripsy which focuses acoustic shock waves onto the stone in order to fragment it into pieces that are small enough to pass naturally. This typically requires a few thousand shock waves delivered at a rate of about 2 Hz. Although lithotripsy is the only non-invasive treatment option for kidney stories, both acute and chronic complications have been identified which could be reduced if fewer shock waves were used. One factor that could be used to reduce the number of shock waves is accounting for the motion of the stone which causes a portion of the delivered shock waves to miss the stone, yielding no therapeutic benefit. Therefore identifying when the stone is not in focus would allow tissue to be spared without affecting fragmentation. The goal of this thesis is to investigate acoustic methods to track the stone in real-time during lithotripsy in order to minimize poorly-targeted shock waves. A relatively small number of low frequency ultrasound transducers were used in pulse-echo mode and a novel optimization routine based on time-of-flight triangulation is used to determine stone location. It was shown that the accuracy of the localization may be estimated without knowing the true stone location. This method performed well in preliminary experiments but the inclusion of tissue-like aberrating layers reduced the accuracy of the localization. Therefore a hybrid imaging technique employing DORT (Decomposition of the Time Reversal Operator) and the MUSIC (Multiple Signal Classification) algorithm was developed. This method was able to localize kidney stories to within a few millimeters even in the presence of an aberrating layer. This would be sufficient accuracy for targeting lithotripter shock waves. The conclusion of this work is that tracking kidney stones with low frequency ultrasound should be effective clinically.

  5. Dust acoustic shock waves in two temperatures charged dusty grains

    SciTech Connect

    El-Shewy, E. K.; Abdelwahed, H. G.; Elmessary, M. A.

    2011-11-15

    The reductive perturbation method has been used to derive the Korteweg-de Vries-Burger equation and modified Korteweg-de Vries-Burger for dust acoustic shock waves in a homogeneous unmagnetized plasma having electrons, singly charged ions, hot and cold dust species with Boltzmann distributions for electrons and ions in the presence of the cold (hot) dust viscosity coefficients. The behavior of the shock waves in the dusty plasma has been investigated.

  6. Shock wave interaction with an abrupt area change

    NASA Technical Reports Server (NTRS)

    Salas, Manuel D.

    1991-01-01

    The wave patterns that occur when a shock wave interacts with an abrupt area changed are analyzed in terms of the incident shock wave Mach number and area-jump ratio. The solutions predicted by a semi-similar models are in good agreement with those obtained numerically from the quasi-one-dimensional time-dependent Euler equations. The entropy production for the wave system is defined and the principle of minimum entropy production is used to resolve a nonuniqueness problem of the self-similar model.

  7. Particle Acceleration by Cme-driven Shock Waves

    NASA Technical Reports Server (NTRS)

    Reames, Donald V.

    1999-01-01

    In the largest solar energetic particle (SEP) events, acceleration occurs at shock waves driven out from the Sun by coronal mass ejections (CMEs). Peak particle intensities are a strong function of CME speed, although the intensities, spectra, and angular distributions of particles escaping the shock are highly modified by scattering on Alfven waves produced by the streaming particles themselves. Element abundances vary in complex ways because ions with different values of Q/A resonate with different parts of the wave spectrum, which varies with space and time. Just recently, we have begun to model these systematic variations theoretically and to explore other consequences of proton-generated waves.

  8. Reflected-wave maser. [low noise amplifier

    NASA Technical Reports Server (NTRS)

    Clauss, R. C. (Inventor)

    1976-01-01

    A number of traveling-wave, slow-wave maser structures, containing active maser material but absent the typical ferrite isolators, are immersed in a nonuniform magnetic field. The microwave signal to be amplified is inserted at a circulator which directs the signal to a slow-wave structure. The signal travels through the slow-wave structure, being amplified according to the distance traveled. The end of the slow-wave structure farthest from the circulator is arranged to be a point of maximum reflection of the signal traveling through the slow-wave structure. As a consequence, the signal to be amplified traverses the slow-wave structure again, in the opposite direction (towards the circulator) experiencing amplification equivalent to that achieved by a conventional traveling-wave maser having twice the length. The circulator directs the amplified signal to following like stages of amplification. Isolators are used in between stages to prevent signals from traveling in the wrong direction, between the stages. Reduced signal loss is experienced at each stage. The high gain produced by each slow-wave structure is reduced to a moderate value by use of a nonuniform magnetic field which also broadens the line width of the maser material. The resulting bandwidth can be exceptionally wide. Cascaded stages provide high gain, exceptionally wide bandwith and very low noise temperature.

  9. Energetic Particle Abundances as Probes of an Interplanetary Shock Wave

    NASA Technical Reports Server (NTRS)

    Reames, D. V.; Tylka, A. J.; White, Nicholas E. (Technical Monitor)

    2002-01-01

    We examine the unique abundance variations of Fe/O and He/H in solar energetic particles from a W09 event of 2001 April 10, that have leaked through the flank of an interplanetary shock launched from W04 on April 9. Shock waves from both events reach the Wind spacecraft on April 11. During the second event, both Fe/O and He/H begin at low values and rise to maxima near the time of passage of the shock waves, indicating greater scattering for the species with the highest rigidity at a given velocity. Strong modulation of Fe/O suggests preferential scattering and trapping of Fe by the wave spectrum near and behind the intermediate shock. A significant factor may be the residual proton-generated waves from the very hard proton spectrum accelerated by the early shock wave prior to the onset of the second event. Thus, ion abundances from the later event probe the residual wave spectrum at the earlier shock.

  10. Belt-snap and towel-snap shock waves

    NASA Astrophysics Data System (ADS)

    Settles, Gary; Hargather, Michael; Lawson, Michael; Bigger, Rory

    2007-11-01

    Traditional simple means of generating shock waves are examined by high-speed imaging. A leather belt is folded upon itself at mid-length and the ends are grasped firmly in each hand. When pushed together a loop forms, and when quickly pulled apart the loop closes rapidly, producing a sharp ``crack'' similar to the cracking of a whip (Shock Waves 8(1), 1998). The towel-snap mimics whip cracking by causing the towel end to rotate supersonically. We investigated these phenomena using a high-speed digital camera (10k and 30k frames/sec, 4 microsec exposure) and a sensitive schlieren optical system of 1m aperture. Results show that compression of the air between the two rapidly-approaching leather belt bands first causes a spherical shock wave to form near one hand. The compression then runs along the belt length toward the other hand at supersonic speed, producing an oblique shock wave that is responsible for the audible crack. In the towel-snap, shock waves are visible from tip motion in open air as well as from the compression due to snapping the towel against a surface. There are no known useful applications of these simple phenomena, but they do address how weak shock waves can be generated by muscle power alone. Several other related examples are also mentioned.

  11. Computation of Thermally Perfect Oblique Shock Wave Properties

    NASA Technical Reports Server (NTRS)

    Tatum, Kenneth E.

    1997-01-01

    A set of compressible flow relations describing flow properties across oblique shock waves, derived for a thermally perfect, calorically imperfect gas, is applied within the existing thermally perfect gas (TPG) computer code. The relations are based upon the specific heat expressed as a polynomial function of temperature. The updated code produces tables of compressible flow properties of oblique shock waves, as well as the original properties of normal shock waves and basic isentropic flow, in a format similar to the tables for normal shock waves found in NACA Rep. 1135. The code results are validated in both the calorically perfect and the calorically imperfect, thermally perfect temperature regimes through comparisons with the theoretical methods of NACA Rep. 1135. The advantages of the TPG code for oblique shock wave calculations, as well as for the properties of isentropic flow and normal shock waves, are its ease of use and its applicability to any type of gas (monatomic, diatomic, triatomic, polyatomic, or any specified mixture thereof).

  12. Computation of Thermally Perfect Properties of Oblique Shock Waves

    NASA Technical Reports Server (NTRS)

    Tatum, Kenneth E.

    1996-01-01

    A set of compressible flow relations describing flow properties across oblique shock waves, derived for a thermally perfect, calorically imperfect gas, is applied within the existing thermally perfect gas (TPG) computer code. The relations are based upon a value of cp expressed as a polynomial function of temperature. The updated code produces tables of compressible flow properties of oblique shock waves, as well as the original properties of normal shock waves and basic isentropic flow, in a format similar to the tables for normal shock waves found in NACA Rep. 1135. The code results are validated in both the calorically perfect and the calorically imperfect, thermally perfect temperature regimes through comparisons with the theoretical methods of NACA Rep. 1135, and with a state-of-the-art computational fluid dynamics code. The advantages of the TPG code for oblique shock wave calculations, as well as for the properties of isentropic flow and normal shock waves, are its ease of use, and its applicability to any type of gas (monatomic, diatomic, triatomic, polyatomic, or any specified mixture thereof).

  13. Shock wave lithotripsy: advances in technology and technique

    PubMed Central

    Lingeman, James E.; McAteer, James A.; Gnessin, Ehud; Evan, Andrew P.

    2010-01-01

    Shock wave lithotripsy (SWL) is the only noninvasive method for stone removal. Once considered as a primary option for the treatment of virtually all stones, SWL is now recognized to have important limitations that restrict its use. In particular, the effectiveness of SWL is severely limited by stone burden, and treatment with shock waves carries the risk of acute injury with the potential for long-term adverse effects. Research aiming to characterize the renal response to shock waves and to determine the mechanisms of shock wave action in stone breakage and renal injury has begun to suggest new treatment strategies to improve success rates and safety. Urologists can achieve better outcomes by treating at slower shock wave rate using a step-wise protocol. The aim is to achieve stone comminution using as few shock waves and at as low a power level as possible. Important challenges remain, including the need to improve acoustic coupling, enhance stone targeting, better determine when stone breakage is complete, and minimize the occurrence of residual stone fragments. New technologies have begun to address many of these issues, and hold considerable promise for the future. PMID:19956196

  14. Reflectivities of Four Shock-Compressed Alkali Halides

    NASA Astrophysics Data System (ADS)

    Diamond, M. R.; McWilliams, R. S.; Eggert, J.; Jeanloz, R.; Ali, S. J.; Collins, G. W.

    2015-12-01

    Laser-shock compression on four alkali halides has been used to probe the transition from insulating to metallic states, a high-pressure transition in chemical bonding that has fundamental implications for planetary formation and structure. Collectively, pressures up to 450 GPa and densities up to three-fold compression were explored across a total of fourteen single-crystal samples of CsI, CsBr, KBr and NaCl. Velocity interferometry was used to record shock velocities and reflectivities at 532 nm during decaying shock compression. The data show up to 40% (or higher) reflectivity, corresponding to notable electrical conductivities, in response to high pressures and temperatures. Furthermore, band-gap closure, dependent on density, can be examined from the reflectivity data. Ionic salts are simple model systems amenable to first-principles theory and serve as analog materials for predicting whether specific chemical constituents can reside in the rocky mantles or metallic cores of planets. A key objective is to disentangle the complementary roles of temperature and compression in transforming ionic into metallic bonding. Furthermore, at high pressures CsI becomes analogous to Xe: they are isoelectronic and follow matching equations of state. Therefore, studies on CsI could inform understanding of noble-gas geochemistry at conditions deep inside planets.

  15. Shock Waves in Outflows from Young Stars

    NASA Astrophysics Data System (ADS)

    Hartigan, Patrick

    This review focuses on physics of the cooling zones behind radiative shocks and the emission line diagnostics that can be used to infer physical conditions and mass loss rates in jets from young stars. Spatial separations of the cooling zones from the shock fronts, now resolvable with HST, and recent evidence for C-shocks have greatly increased our understanding of how shocks in outflows interact with the surrounding medium and with other material within the flow. By combining multiple epoch HST images, one can create `movies' of flows like those produced from numerical codes, and learn what kinds of instabilities develop within these systems.

  16. Turbulent Magnetic Field Amplification behind Strong Shock Waves in GRB and SNR

    NASA Astrophysics Data System (ADS)

    Inoue, Tsuyoshi

    2012-09-01

    Using three-dimensional (special relativistic) magnetohydrodynamics simulations, the amplification of magnetic field behind strong shock wave is studied. In supernova remnants and gamma-ray bursts, strong shock waves propagate through an inhomogeneous density field. When the shock wave hit a density bump or density dent, the Richtmyer-Meshkov instability is induced that cause a deformation of the shock front. The deformed shock leaves vorticity behind the shock wave that amplifies the magnetic field due to the stretching of field lines.

  17. Wind Observations of Wave Heating and/or Particle Energization at Supercritical Interplanetary Shocks

    NASA Technical Reports Server (NTRS)

    Wilson, Lynn Bruce, III; Szabo, Adam; Koval, Andriy; Cattell, Cynthia A.; Kellogg, Paul J.; Goetz, Keith; Breneman, Aaron; Kersten, Kris; Kasper, Justin C.; Pulupa, Marc

    2011-01-01

    We present the first observations at supercritical interplanetary shocks of large amplitude (> 100 mV/m pk-pk) solitary waves, approx.30 mV/m pk-pk waves exhibiting characteristics consistent with electron Bernstein waves, and > 20 nT pk-pk electromagnetic lower hybrid-like waves, with simultaneous evidence for wave heating and particle energization. The solitary waves and the Bernstein-like waves were likely due to instabilities driven by the free energy provided by reflected ions [Wilson III et al., 2010]. They were associated with strong particle heating in both the electrons and ions. We also show a case example of parallel electron energization and perpendicular ion heating due to a electromagnetic lower hybrid-like wave. Both studies provide the first experimental evidence of wave heating and/or particle energization at interplanetary shocks. Our experimental results, together with the results of recent Vlasov [Petkaki and Freeman, 2008] and PIC [Matsukyo and Scholer, 2006] simulations using realistic mass ratios provide new evidence to suggest that the importance of wave-particle dissipation at shocks may be greater than previously thought.

  18. ULF waves upstream of the Venus bow shock - Properties of one-hertz waves

    NASA Technical Reports Server (NTRS)

    Orlowski, D. S.; Russell, C. T.

    1991-01-01

    Pioneer Venus Orbiter data are used here to study the properties of a class of ULF upstream waves with relatively high observed frequencies. These waves show significant similarity to 'one-Hz' waves identified at earth in the ISEE 1 and 2 observations and the whistler waves identified earlier by IMP 6 observations. The waves appear almost immediately after the spacecraft crosses the magnetic field tangent line to the bow shock surface into the region of connected field lines. The wave amplitude decreases with distance from the shock measured along the magnetic field line. Group velocities calculated using the cold plasma dispersion relation indicate that the waves have sufficient upstream velocities to propagate form the shock into the solar wind. The totality of observations seem best explained by a source of right-handed whistler mode waves at the bow shock.

  19. Fractionated Repetitive Extracorporeal Shock Wave Therapy: A New Standard in Shock Wave Therapy?

    PubMed Central

    Kisch, Tobias; Sorg, Heiko; Forstmeier, Vinzent; Mailaender, Peter; Kraemer, Robert

    2015-01-01

    Background. ESWT has proven clinical benefit in dermatology and plastic surgery. It promotes wound healing and improves tissue regeneration, connective tissue disorders, and inflammatory skin diseases. However, a single treatment session or long intervals between sessions may reduce the therapeutic effect. The present study investigated the effects of fractionated repetitive treatment in skin microcirculation. Methods. 32 rats were randomly assigned to two groups and received either fractionated repetitive high-energy ESWT every ten minutes or placebo shock wave treatment, applied to the dorsal lower leg. Microcirculatory effects were continuously assessed by combined laser Doppler imaging and photospectrometry. Results. In experimental group, cutaneous tissue oxygen saturation was increased 1 minute after the first application and until the end of the measuring period at 80 minutes after the second treatment (P < 0.05). The third ESWT application boosted the effect to its highest extent. Cutaneous capillary blood flow showed a significant increase after the second application which was sustained for 20 minutes after the third application (P < 0.05). Placebo group showed no statistically significant differences. Conclusions. Fractionated repetitive extracorporeal shock wave therapy (frESWT) boosts and prolongs the effects on cutaneous hemodynamics. The results indicate that frESWT may provide greater benefits in the treatment of distinct soft tissue disorders compared with single-session ESWT. PMID:26273619

  20. Development of a broadband reflectivity diagnostic for laser driven shock compression experiments

    DOE PAGESBeta

    Ali, S. J.; Bolme, C. A.; Collins, G. W.; Jeanloz, R.

    2015-04-01

    A normal - incidence visible and near - infrared Shock Wave Optical Reflectivity Diagnostic (SWORD) was constructed to investigate changes in the optical properties of materials under dynamic laser compression . Documenting wavelength - and time - dependent changes in the optical properties of laser - shock compressed samples has been difficult, primarily due to the small sample sizes and short time scales involved , but we succeeded in doing so by broadening a series of time delayed 800 - nm pulses from an ultra fast Ti: sapphire laser to generate high - intensity broadband light at nanosecond time scalesmore » . This diagnostic was demonstrated over the wavelength range 450 to 1150 nm with up to 16 time displaced spectra during a single shock experiment. Simultaneous off - normal incidence velocity interferometry (VISAR) characterize d the sample under laser - compression , and also provide d a n independent reflectivity measurement at 532 nm wavelength . Lastly, the shock - driven semiconductor - to - metallic transition in germanium was documented by way of reflectivity measurements with 0.5 ns time resolution and a wavelength resolution of 10 nm .« less

  1. Development of a broadband reflectivity diagnostic for laser driven shock compression experiments

    SciTech Connect

    Ali, S. J.; Bolme, C. A.; Collins, G. W.; Jeanloz, R.

    2015-04-01

    A normal - incidence visible and near - infrared Shock Wave Optical Reflectivity Diagnostic (SWORD) was constructed to investigate changes in the optical properties of materials under dynamic laser compression . Documenting wavelength - and time - dependent changes in the optical properties of laser - shock compressed samples has been difficult, primarily due to the small sample sizes and short time scales involved , but we succeeded in doing so by broadening a series of time delayed 800 - nm pulses from an ultra fast Ti: sapphire laser to generate high - intensity broadband light at nanosecond time scales . This diagnostic was demonstrated over the wavelength range 450 to 1150 nm with up to 16 time displaced spectra during a single shock experiment. Simultaneous off - normal incidence velocity interferometry (VISAR) characterize d the sample under laser - compression , and also provide d a n independent reflectivity measurement at 532 nm wavelength . Lastly, the shock - driven semiconductor - to - metallic transition in germanium was documented by way of reflectivity measurements with 0.5 ns time resolution and a wavelength resolution of 10 nm .

  2. Development of a broadband reflectivity diagnostic for laser driven shock compression experiments

    NASA Astrophysics Data System (ADS)

    Ali, S. J.; Bolme, C. A.; Collins, G. W.; Jeanloz, R.

    2015-04-01

    A normal-incidence visible and near-infrared shock wave optical reflectivity diagnostic was constructed to investigate changes in the optical properties of materials under dynamic laser compression. Documenting wavelength- and time-dependent changes in the optical properties of laser-shock compressed samples has been difficult, primarily due to the small sample sizes and short time scales involved, but we succeeded in doing so by broadening a series of time delayed 800-nm pulses from an ultrafast Ti:sapphire laser to generate high-intensity broadband light at nanosecond time scales. This diagnostic was demonstrated over the wavelength range 450-1150 nm with up to 16 time displaced spectra during a single shock experiment. Simultaneous off-normal incidence velocity interferometry (velocity interferometer system for any reflector) characterized the sample under laser-compression and also provided an independent reflectivity measurement at 532 nm wavelength. The shock-driven semiconductor-to-metallic transition in germanium was documented by the way of reflectivity measurements with 0.5 ns time resolution and a wavelength resolution of 10 nm.

  3. In the footsteps of Ernst Mach - A historical review of shock wave research at the Ernst-Mach-Institut

    NASA Astrophysics Data System (ADS)

    Reichenbach, H.

    The aim of this paper is to recall some of the historical work on shock waves and to give a brief survey of research activities at the Ernst-Mach-Institut (EMI). Some fundamental results of Ernst Mach (1838 - 1916) are demonstrated and historical remarks are given to the shock tube as an important tool in shock wave research. The activity at EMI in this field was initiated by Prof. H. Schardin (1902 - 1965) in 1955 and has since been continued. Propagation processes of shock and blast waves, blast loading phenomena, shock attenuation, shock reflection at various surfaces, development of new types of blast simulators, electromagnetically driven T-tubes, precursor and decursor phenomena are only a few examples of research topics at EMI that will be discussed.

  4. Waves associated with interplanetary shocks: Types and properties

    NASA Astrophysics Data System (ADS)

    Goncharov, Oleksandr; Nemecek, Zdenek; Safrankova, Jana; Prech, Lubomir; Koval, Andriy; Wilson, Lynn B., III; Zastenker, Georgy N.

    2016-04-01

    Interplanetary (IP) shocks are often associated with high-frequency (several Hz) wave packets in both upstream and downstream regions. These waves could be resolved in Wind fast magnetic field data but the time resolution of plasma instruments is insufficient for their detection. The BMSW instrument onboard the Spektr-R spacecraft measures solar wind parameters with a resolution of 32 ms and it allows a detailed analysis of these waves. Our previous analysis of subcritical low-Mach-number fast forward shocks has shown that the both upstream and downstream waves conserve over the spacecraft separation of the order of 200 Re and their wavelengths are directly proportional to the shock ramp thickness that is controlled by the ion thermal gyroradius. Comparing observations of both Wind and Spektr-R spacecraft, we discuss a nature of these waves in both regions and their properties and their dependence on upstream solar wind and magnetic field parameters.

  5. Numerical Simulation of Low-Density Shock-Wave Interactions

    NASA Technical Reports Server (NTRS)

    Glass, Christopher E.

    1999-01-01

    Computational Fluid Dynamics (CFD) numerical simulations of low-density shock-wave interactions for an incident shock impinging on a cylinder have been performed. Flow-field density gradient and surface pressure and heating define the type of interference pattern and corresponding perturbations. The maximum pressure and heat transfer level and location for various interaction types (i.e., shock-wave incidence with respect to the cylinder) are presented. A time-accurate solution of the Type IV interference is employed to demonstrate the establishment and the steadiness of the low-density flow interaction.

  6. Nonstandard Analysis and Jump Conditions for Converging Shock Waves

    NASA Technical Reports Server (NTRS)

    Baty, Roy S.; Farassat, Fereidoun; Tucker, Don H.

    2008-01-01

    Nonstandard analysis is an area of modern mathematics which studies abstract number systems containing both infinitesimal and infinite numbers. This article applies nonstandard analysis to derive jump conditions for one-dimensional, converging shock waves in a compressible, inviscid, perfect gas. It is assumed that the shock thickness occurs on an infinitesimal interval and the jump functions in the thermodynamic and fluid dynamic parameters occur smoothly across this interval. Predistributions of the Heaviside function and the Dirac delta measure are introduced to model the flow parameters across a shock wave. The equations of motion expressed in nonconservative form are then applied to derive unambiguous relationships between the jump functions for the flow parameters.

  7. Development of an Explosively Driven Sustained Shock Generator for Shock Wave Studies

    NASA Astrophysics Data System (ADS)

    Taylor, P.; Cook, I. T.; Salisbury, D. A.

    2004-07-01

    Investigation of explosive initiation phenomena close to the initiation threshold with explosively driven shock waves is difficult due to the attenuative nature of the pressure input. The design and experimental testing of a sustained shock wave generator based on an explosive plane wave lens and impedance mismatched low density foam and high impedance layers is described. Calibration experiments to develop a 1-D calculational model for the plane wave lens and booster charge were performed. A calculational study was undertaken to determine the sensitivity of the output pulse to plate and foam thicknesses and foam density. A geometry which generates a 24kb almost flat topped shock wave with a duration of over 4μs into the HMX based plastic explosive EDC37 was defined and tested. Experimental shock profile data is compared with pre-shot predictions from the PETRA Eulerian hydrocode incorporating a "snowplough" or simple locking model for the foam. A reasonable match to the observed magnitude and profile of the initial shock is achieved, although the timing of subsequent shock waves is less well matched.

  8. Head-on collision of shock wave induced vortices with solid and perforated walls

    NASA Astrophysics Data System (ADS)

    Kontis, K.; An, R.; Zare-Behtash, H.; Kounadis, D.

    2008-01-01

    An experimental study has been conducted to examine the interaction of shock wave induced vortices with a flat plate and a perforated plate. The experiments were carried out using a 30mm internal diameter shock-tube at Mach numbers 1.31, 1.49, and 1.61 under critical driver conditions. Air was used both in the driver and driven sections. High-speed schlieren photography was employed to study the flow development and the resulting interactions with the plates. Wall pressure measurements on both plates were also carried out in order to study the flow interactions quantitatively. The experimental results indicated that a region of strong flow development is generated near the wall surface, due to the flow interactions of reflected waves and oncoming induced vortices. This flow behavior causes the generation of multiple pressure fluctuations on the wall. In the case of the perforated plate, a weaker initial reflected wave is produced, which is followed by compression waves, due to the internal reflections within the plate. The transmitted wave is reduced in strength, compared to the initial incident shock wave.

  9. Generation of Focused Shock Waves in Water for Biomedical Applications

    NASA Astrophysics Data System (ADS)

    Lukeš, Petr; Šunka, Pavel; Hoffer, Petr; Stelmashuk, Vitaliy; Beneš, Jiří; Poučková, Pavla; Zadinová, Marie; Zeman, Jan

    The physical characteristics of focused two-successive (tandem) shock waves (FTSW) in water and their biological effects are presented. FTSW were ­generated by underwater multichannel electrical discharges in a highly conductive saline solution using two porous ceramic-coated cylindrical electrodes of different diameter and surface area. The primary cylindrical pressure wave generated at each composite electrode was focused by a metallic parabolic reflector to a common focal point to form two strong shock waves with a variable time delay between the waves. The pressure field and interaction between the first and the second shock waves at the focus were investigated using schlieren photography and polyvinylidene fluoride (PVDF) shock gauge sensors. The largest interaction was obtained for a time delay of 8-15 μs between the waves, producing an amplitude of the negative pressure phase of the second shock wave down to -80 MPa and a large number of cavitations at the focus. The biological effects of FTSW were demonstrated in vitro on damage to B16 melanoma cells, in vivo on targeted lesions in the thigh muscles of rabbits and on the growth delay of sarcoma tumors in Lewis rats treated in vivo by FTSW, compared to untreated controls.

  10. Shock wave diagnostics using fluorescent dye probes

    NASA Astrophysics Data System (ADS)

    Banishev, Alexandr; Christensen, James; Dlott, Dana

    2015-06-01

    Fluorescent probes are highly developed, and have found increasing use in a wide variety of applications. We have studied shock compression of various materials with embedded dye probes used as high speed probes of pressure and temperature. Under the right conditions, dye emission can be used to make a map of the pressure distribution in shocked microstructured materials with high time (1 ns) and space (1 micrometer) resolution. In order to accomplish this goal, we started by studying shock compression of PMMA polymer with rhodamine 6G dye (R6G), as a function of shock pressure and shock duration. We observed the shock-induced spectral redshift and the shock-induced intensity loss. We investigated the fundamental mechanisms of R6G response to pressure. We showed that the time response of a dye probe is limited by its photophysical behavior under shock. We developed superemissive ultrafast dye probes by embedding R6G in a silica nanoparticle. More recently, we have searched for dye probes that have better responses. For instance, we have found that the dye Nile Red embedded in the right polymer matrix has 1.7 times larger pressure-induced redshift than R6G.

  11. Growth and decay of weak shock waves in magnetogasdynamics

    NASA Astrophysics Data System (ADS)

    Singh, L. P.; Singh, D. B.; Ram, S. D.

    2015-12-01

    The purpose of the present study is to investigate the problem of the propagation of weak shock waves in an inviscid, electrically conducting fluid under the influence of a magnetic field. The analysis assumes the following two cases: (1) a planar flow with a uniform transverse magnetic field and (2) cylindrically symmetric flow with a uniform axial or varying azimuthal magnetic field. A system of two coupled nonlinear transport equations, governing the strength of a shock wave and the first-order discontinuity induced behind it, are derived that admit a solution that agrees with the classical decay laws for a weak shock. An analytic expression for the determination of the shock formation distance is obtained. How the magnetic field strength, whether axial or azimuthal, influences the shock formation is also assessed.

  12. Hydrodynamic growth and decay of planar shock waves

    NASA Astrophysics Data System (ADS)

    Piriz, A. R.; Sun, Y. B.; Tahir, N. A.

    2016-03-01

    A model for the hydrodynamic attenuation (growth and decay) of planar shocks is presented. The model is based on the approximate integration of the fluid conservation equations, and it does not require the heuristic assumptions used in some previous works. A key issue of the model is that the boundary condition on the piston surface is given by the retarded pressure, which takes into account the transit time of the sound waves between the piston and any position at the bulk of the shocked fluid. The model yields the shock pressure evolution for any given pressure pulse on the piston, as well as the evolution of the trajectories, velocities, and accelerations on the shock and piston surfaces. An asymptotic analytical solution is also found for the decay of the shock wave.

  13. Plasma wave turbulence associated with an interplanetary shock. [wave in solar wind upstream of magnetosphere

    NASA Technical Reports Server (NTRS)

    Gurnett, D. A.; Neubauer, F. M.; Schwenn, R.

    1979-01-01

    The present paper deals with interplanetary shocks, detected and analyzed to date, from the Helios 1 and 2 spacecraft in eccentric solar orbits. The plasma wave turbulence associated with the shock observed on March 30, 1976 is studied in detail. This event is of particular interest because it represents a clearly defined burst of turbulence against a quiet solar wind background both upstream and downstream of the shock. The shock itself is an oblique shock with upstream parameters characterized by a low Mach number, a low beta, and an abnormally large electron to ion temperature ratio. The types of plasma wave detected are discussed.

  14. Setting Time Measurement Using Ultrasonic Wave Reflection

    SciTech Connect

    Chung, Chul-Woo; Suraneni, Prannoy; Popovics, John S.; Struble, Leslie J.

    2012-01-09

    Ultrasonic shear wave reflection was used to investigate setting times of cement pastes by measuring the reflection coefficient at the interface between hydrating cement pastes of varying water-to-cement ratio and an ultrasonic buffer material. Several different buffer materials were employed, and the choice of buffer was seen to strongly affect measurement sensitivity; high impact polystyrene showed the highest sensitivity to setting processes because it had the lowest acoustic impedance value. The results show that ultrasonic shear-wave reflection can be used successfully to monitor early setting processes of cement paste with good sensitivity when such a very low impedance buffer is employed. Criteria are proposed to define set times, and the resulting initial and final set times agreed broadly with those determined using the standard penetration resistance test.

  15. Development of a Novel Shock Wave Catheter Ablation System

    NASA Astrophysics Data System (ADS)

    Yamamoto, H.; Hasebe, Yuhi; Kondo, Masateru; Fukuda, Koji; Takayama, Kazuyoshi; Shimokawa, Hiroaki

    Although radio-frequency catheter ablation (RFCA) is quite effective for the treatment tachyarrhythmias, it possesses two fundamental limitations, including limited efficacy for the treatment of ventricular tachyarrhythmias of epicardial origin and the risk of thromboembolism. Consequently, new method is required, which can eradicate arrhythmia source in deep part of cardiac muscle without heating. On the other hand, for a medical application of shock waves, extracorporeal shock wave lithotripter (ESWL) has been established [1]. It was demonstrated that the underwater shock focusing is one of most efficient method to generate a controlled high pressure in a small region [2]. In order to overcome limitations of existing methods, we aimed to develop a new catheter ablation system with underwater shock waves that can treat myocardium at arbitrary depth without causing heat.

  16. Schlieren imaging of shock waves radiated by a trumpet

    NASA Astrophysics Data System (ADS)

    Rendon, Pablo L.; Velasco-Segura, Roberto; Echeverria, Carlos; Porta, David; Vazquez, Teo; Perez-Lopez, Antonio; Stern, Catalina

    2014-11-01

    The flaring bell section of modern trumpets is known to be critical in determining a wide variety of properties associated with the sound radiated by these instruments. We are particularly interested in the shape of the radiated wavefront, which clearly depends on the bell profile. A horn loudspeaker is used to drive high-intensity sound at different frequencies through a B-flat concert trumpet. The sound intensity is high enough to produce shock waves inside the instrument resonator, and the radiated shocks are then visualised using Schlieren imaging. Through these images we are able to study the geometry of the shock waves radiated by the instrument bell, and also to calculate their propagation speed. The results show that propagation outside the bell is very nearly spherical, and that, as expected, the frequency of the driving signal affects the point at which the shock waves separate from the instrument. We acknowledge financial support from PAPIIT IN109214 and PAPIIT IN117712.

  17. Initiating solar system formation through stellar shock waves

    NASA Technical Reports Server (NTRS)

    Boss, A. P.; Myhill, E. A.

    1993-01-01

    Isotopic anomalies in presolar grains and other meteoritical components require nucleosynthesis in stellar interiors, condensation into dust grains in stellar envelopes, transport of the grains through the interstellar medium by stellar outflows, and finally injection of the grains into the presolar nebula. The proximity of the presolar cloud to these energetic stellar events suggests that a shock wave from a stellar outflow might have initiated the collapse of an otherwise stable presolar cloud. We have begun to study the interactions of stellar shock waves with thermally supported, dense molecular cloud cores, using a three spatial dimension (3D) radiative hydrodynamics code. Supernova shock waves have been shown by others to destroy quiescent clouds, so we are trying to determine if the much smaller shock speeds found in, e.g., asymptotic giant branch (AGB) star winds, are strong enough to initiate collapse in an otherwise stable, rotating, solar-mass cloud core, without leading to destruction of the cloud.

  18. Explosive-driven shock wave and vortex ring interaction with a propane flame

    NASA Astrophysics Data System (ADS)

    Giannuzzi, P. M.; Hargather, M. J.; Doig, G. C.

    2016-02-01

    Experiments were performed to analyze the interaction of an explosively driven shock wave and a propane flame. A 30 g explosive charge was detonated at one end of a 3-m-long, 0.6-m-diameter shock tube to produce a shock wave which propagated into the atmosphere. A propane flame source was positioned at various locations outside of the shock tube to investigate the effect of different strength shock waves. High-speed retroreflective shadowgraph imaging visualized the shock wave motion and flame response, while a synchronized color camera imaged the flame directly. The explosively driven shock tube was shown to produce a repeatable shock wave and vortex ring. Digital streak images show the shock wave and vortex ring propagation and expansion. The shadowgrams show that the shock wave extinguishes the propane flame by pushing it off of the fuel source. Even a weak shock wave was found to be capable of extinguishing the flame.

  19. The anatomy of floating shock fitting. [shock waves computation for flow field

    NASA Technical Reports Server (NTRS)

    Salas, M. D.

    1975-01-01

    The floating shock fitting technique is examined. Second-order difference formulas are developed for the computation of discontinuities. A procedure is developed to compute mesh points that are crossed by discontinuities. The technique is applied to the calculation of internal two-dimensional flows with arbitrary number of shock waves and contact surfaces. A new procedure, based on the coalescence of characteristics, is developed to detect the formation of shock waves. Results are presented to validate and demonstrate the versatility of the technique.

  20. Propagation of acoustic shock waves between parallel rigid boundaries and into shadow zones

    NASA Astrophysics Data System (ADS)

    Desjouy, C.; Ollivier, S.; Marsden, O.; Dragna, D.; Blanc-Benon, P.

    2015-10-01

    The study of acoustic shock propagation in complex environments is of great interest for urban acoustics, but also for source localization, an underlying problematic in military applications. To give a better understanding of the phenomenon taking place during the propagation of acoustic shocks, laboratory-scale experiments and numerical simulations were performed to study the propagation of weak shock waves between parallel rigid boundaries, and into shadow zones created by corners. In particular, this work focuses on the study of the local interactions taking place between incident, reflected, and diffracted waves according to the geometry in both regular or irregular - also called Von Neumann - regimes of reflection. In this latter case, an irregular reflection can lead to the formation of a Mach stem that can modify the spatial distribution of the acoustic pressure. Short duration acoustic shock waves were produced by a 20 kilovolts electric spark source and a schlieren optical method was used to visualize the incident shockfront and the reflection/diffraction patterns. Experimental results are compared to numerical simulations based on the high-order finite difference solution of the two dimensional Navier-Stokes equations.

  1. Propagation of acoustic shock waves between parallel rigid boundaries and into shadow zones

    SciTech Connect

    Desjouy, C. Ollivier, S.; Dragna, D.; Blanc-Benon, P.; Marsden, O.

    2015-10-28

    The study of acoustic shock propagation in complex environments is of great interest for urban acoustics, but also for source localization, an underlying problematic in military applications. To give a better understanding of the phenomenon taking place during the propagation of acoustic shocks, laboratory-scale experiments and numerical simulations were performed to study the propagation of weak shock waves between parallel rigid boundaries, and into shadow zones created by corners. In particular, this work focuses on the study of the local interactions taking place between incident, reflected, and diffracted waves according to the geometry in both regular or irregular – also called Von Neumann – regimes of reflection. In this latter case, an irregular reflection can lead to the formation of a Mach stem that can modify the spatial distribution of the acoustic pressure. Short duration acoustic shock waves were produced by a 20 kilovolts electric spark source and a schlieren optical method was used to visualize the incident shockfront and the reflection/diffraction patterns. Experimental results are compared to numerical simulations based on the high-order finite difference solution of the two dimensional Navier-Stokes equations.

  2. Attenuation of shock waves in copper and stainless steel

    SciTech Connect

    Harvey, W.B.

    1986-06-01

    By using shock pins, data were gathered on the trajectories of shock waves in stainless steel (SS-304L) and oxygen-free-high-conductivity copper (OFHC-Cu). Shock pressures were generated in these materials by impacting the appropriate target with thin (approx.1.5 mm) flying plates. The flying plates in these experiments were accelerated to high velocities (approx.4 km/s) by high explosives. Six experiments were conducted, three using SS-304L as the target material and three experiments using OFHC-Cu as the target material. Peak shock pressures generated in the steel experiments were approximately 109, 130, and 147 GPa and in the copper experiments, the peak shock pressures were approximately 111, 132, and 143 GPa. In each experiment, an attenuation of the shock wave by a following release wave was clearly observed. An extensive effort using two characteristic codes (described in this work) to theoretically calculate the attenuation of the shock waves was made. The efficacy of several different constitutive equations to successfully model the experiments was studied by comparing the calculated shock trajectories to the experimental data. Based on such comparisons, the conclusion can be drawn that OFHC-Cu enters a melt phase at about 130 GPa on the principal Hugoniot. There was no sign of phase changes in the stainless-steel experiments. In order to match the observed attenuation of the shock waves in the SS-304L experiments, it was necessary to include strength effects in the calculations. It was found that the values for the parameters in the strength equations were dependent on the equation of state used in the modeling of the experiments. 66 refs., 194 figs., 77 tabs.

  3. Flash Lamp Integrating Sphere Technique for Measuring the Dynamic Reflectance of Shocked Materials

    SciTech Connect

    Stevens, Gerald; La Lone, Brandon; Veeser, Lynn; Hixson, Rob; Holtkamp, David

    2013-07-08

    Accurate reflectance (R) measurements of metals undergoing shock wave compression can benefit high pressure research in several ways. For example, pressure dependent reflectance measurements can be used to deduce electronic band structure, and discrete changes with pressure or temperature may indicate the occurrence of a phase boundary. Additionally, knowledge of the wavelength dependent emissivity (1 -R, for opaque samples) of the metal surface is essential for accurate pyrometric temperature measurement because the radiance is a function of both the temperature and emissivity. We have developed a method for measuring dynamic reflectance in the visible and near IR spectral regions with nanosecond response time and less than 1.5% uncertainty. The method utilizes an integrating sphere fitted with a xenon flash-lamp illumination source. Because of the integrating sphere, the measurements are insensitive to changes in surface curvature or tilt. The in-situ high brightness of the flash-lamp exceeds the sample’s thermal radiance and also enables the use of solid state detectors for recording the reflectance signals with minimal noise. Using the method, we have examined the dynamic reflectance of gallium and tin subjected to shock compression from high explosives. The results suggest significant reflectance changes across phase boundaries for both metals. We have also used the method to determine the spectral emissivity of shock compressed tin at the interface between tin and a LiF window. The results were used to perform emissivity corrections to previous pyrometry data and obtain shock temperatures of the tin/LiF interface with uncertainties of less than 2%.

  4. Dynamics of shock waves in a superfluid unitary Fermi gas

    NASA Astrophysics Data System (ADS)

    Wen, Wen; Shui, Tiankun; Shan, Yafei; Zhu, Changping

    2015-09-01

    We study the formation and dynamics of shock waves initiated by a repulsive potential in a superfluid unitary Fermi gas by using the order-parameter equation. In the theoretical framework, the regularization process of shock waves mediated by the quantum pressure term is purely dispersive. Our results show good agreement with the experiment of Joseph et al (2011 Phys. Rev. Lett. 106 150401). We reveal that the boxlike-shaped density peak observed in the experiment consists of many vortex rings due to the transverse instability of the dispersive shock wave. In addition, we study the transition from a sound wave to subsonic shock waves as the strength of the repulsive potential increases and show a strong qualitative change in the propagation speed of the wavefronts. For a relatively small strength of the repulsive potential, the propagation speed decreases below the sound speed with the increase of the strength as a scaling behavior. For a large strength where the shock waves are formed by colliding two spatially separated clouds, the speed is still smaller than the sound speed, but remains almost unchanged as the strength increases, which can be interpreted as the same expansion speed of the proliferation of the vortex rings originated from the transverse instability.

  5. Converging shock wave focusing and interaction with a target

    NASA Astrophysics Data System (ADS)

    Nitishinskiy, M.; Efimov, S.; Antonov, O.; Yanuka, D.; Gurovich, V. Tz.; Bernshtam, V.; Fisher, V.; Krasik, Ya. E.

    2016-04-01

    Converging shock waves in liquids can be used efficiently in the research of the extreme state of matter and in various applications. In this paper, the recent results related to the interaction of a shock wave with plasma preliminarily formed in the vicinity of the shock wave convergence are presented. The shock wave is produced by the underwater electrical explosion of a spherical wire array. The plasma is generated prior to the shock wave's arrival by a low-pressure gas discharge inside a quartz capillary placed at the equatorial plane of the array. Analysis of the Stark broadening of Hα and Hβ spectral lines and line-to-continuum ratio, combined with the ratio of the relative intensities of carbon C III/C II and silicon Si III/Si II lines, were used to determine the plasma density and temperature evolution. It was found that during the first ˜200 ns with respect to the beginning of the plasma compression by the shock wave and when the spectral lines are resolved, the plasma density increases from 2 × 1017 cm-3 to 5 × 1017 cm-3, while the temperature remains at the same value of 3-4 eV. Further, following the model of an adiabatically imploding capillary, the plasma density increases >1019 cm-3, leading to the continuum spectra obtained experimentally, and the plasma temperature >30 eV at radii of compression of ≤20 μm. The data obtained indicate that the shock wave generated by the underwater electrical explosion of a spherical wire array retains its uniformity during the main part of its convergence.

  6. Propagation of impact-induced shock waves in porous sandstone using mesoscale modeling

    NASA Astrophysics Data System (ADS)

    GÜLdemeister, Nicole; WÜNnemann, Kai; Durr, Nathanael; Hiermaier, Stefan

    2013-01-01

    Abstract-Generation and propagation of <span class="hlt">shock</span> <span class="hlt">waves</span> by meteorite impact is significantly affected by material properties such as porosity, water content, and strength. The objective of this work was to quantify processes related to the <span class="hlt">shock</span>-induced compaction of pore space by numerical modeling, and compare the results with data obtained in the framework of the Multidisciplinary Experimental and Modeling Impact Research Network (MEMIN) impact experiments. We use mesoscale models resolving the collapse of individual pores to validate macroscopic (homogenized) approaches describing the bulk behavior of porous and water-saturated materials in large-scale models of crater formation, and to quantify localized <span class="hlt">shock</span> amplification as a result of pore space crushing. We carried out a suite of numerical models of planar <span class="hlt">shock</span> <span class="hlt">wave</span> propagation through a well-defined area (the "sample") of porous and/or water-saturated material. The porous sample is either represented by a homogeneous unit where porosity is treated as a state variable (macroscale model) and water content by an equation of state for mixed material (ANEOS) or by a defined number of individually resolved pores (mesoscale model). We varied porosity and water content and measured thermodynamic parameters such as <span class="hlt">shock</span> <span class="hlt">wave</span> velocity and particle velocity on meso- and macroscales in separate simulations. The mesoscale models provide additional data on the heterogeneous distribution of peak <span class="hlt">shock</span> pressures as a consequence of the complex superposition of <span class="hlt">reflecting</span> rarefaction <span class="hlt">waves</span> and <span class="hlt">shock</span> <span class="hlt">waves</span> originating from the crushing of pores. We quantify the bulk effect of porosity, the reduction in <span class="hlt">shock</span> pressure, in terms of Hugoniot data as a function of porosity, water content, and strength of a quartzite matrix. We find a good agreement between meso-, macroscale models and Hugoniot data from <span class="hlt">shock</span> experiments. We also propose a combination of a porosity compaction model (ɛ-α model) that was</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/25615159','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/25615159"><span id="translatedtitle">Asymptotic dynamics of <span class="hlt">reflecting</span> spiral <span class="hlt">waves</span>.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Langham, Jacob; Biktasheva, Irina; Barkley, Dwight</p> <p>2014-12-01</p> <p>Resonantly forced spiral <span class="hlt">waves</span> in excitable media drift in straight-line paths, their rotation centers behaving as pointlike objects moving along trajectories with a constant velocity. Interaction with medium boundaries alters this velocity and may often result in a <span class="hlt">reflection</span> of the drift trajectory. Such <span class="hlt">reflections</span> have diverse characteristics and are known to be highly nonspecular in general. In this context we apply the theory of response functions, which via numerically computable integrals, reduces the reaction-diffusion equations governing the whole excitable medium to the dynamics of just the rotation center and rotation phase of a spiral <span class="hlt">wave</span>. Spiral <span class="hlt">reflection</span> trajectories are computed by this method for both small- and large-core spiral <span class="hlt">waves</span> in the Barkley model. Such calculations provide insight into the process of <span class="hlt">reflection</span> as well as explanations for differences in trajectories across parameters, including the effects of incidence angle and forcing amplitude. Qualitative aspects of these results are preserved far beyond the asymptotic limit of weak boundary effects and slow resonant drift. PMID:25615159</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013ShWav..23..221M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013ShWav..23..221M"><span id="translatedtitle">A comparison between constant volume induction times and results from spatially resolved simulation of ignition behind <span class="hlt">reflected</span> <span class="hlt">shocks</span>: implications for <span class="hlt">shock</span> tube experiments</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Melguizo-Gavilanes, J.; Bauwens, L.</p> <p>2013-05-01</p> <p>The induction time measured in <span class="hlt">shock</span> tube experiments is typically converted into kinetic data assuming that the reaction takes place in a constant volume process, thus neglecting spatial gradients. The actual process of <span class="hlt">shock</span> ignition is, however, both time- and space-dependent; ignition takes place at a well-defined location, and subsequently a front travels, which may couple with the pressure <span class="hlt">wave</span> that it created and forms a detonation <span class="hlt">wave</span> behind the <span class="hlt">shock</span> that <span class="hlt">reflects</span> off the wall. To assess how different the actual processes are compared with the constant volume assumption, a numerical study was performed using a simplified three step chain-branching kinetic scheme. To overcome the difficulties that arise when simulating <span class="hlt">shock</span>-induced ignition due to the initial absence of a domain filled with <span class="hlt">shocked</span> reactive mixture, the problem is solved in a transformed frame of reference. Furthermore, initial conditions are derived from short-time asymptotics, which resolves the initial singularity. The induction times obtained using the full unsteady formulation with those of the homogeneous explosion are compared for various values of the heat release. Results for the spatially dependent formulation show that the evolution of the post-<span class="hlt">shock</span> flow is complex, and that it leads to a gradient in induction times, after the passage of the <span class="hlt">reflected</span> <span class="hlt">shock</span>. For all cases simulated, thermal explosion initially occurs very close to the wall, and the corresponding induction time is found to be larger than that predicted under the constant volume assumption. As the measurement is made further away however, the actual time interval between passage of the <span class="hlt">reflected</span> <span class="hlt">shock</span>, and the specified pressure increase denoting ignition, decreases to a value close to zero, corresponding to that obtained along a Rayleigh line matching that of a steady ZND process (assuming a long enough tube). In situations where the constant volume assumption is expected to be weak, more accurate kinetic data</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19850066354&hterms=application+data+science&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dapplication%2Bdata%2Bscience','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19850066354&hterms=application+data+science&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dapplication%2Bdata%2Bscience"><span id="translatedtitle">Application of <span class="hlt">shock</span> <span class="hlt">wave</span> data to earth and planetary science</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Ahrens, T. J.</p> <p>1985-01-01</p> <p>It is pointed out that <span class="hlt">shock</span> <span class="hlt">wave</span> data for: (1) low temperature condensable gases H2 and He, (2) H2O, CH4, NH3, CO, CO2, and N2 ices, and (3) silicates, metals, oxides and sulfides have many applications in geophysics and planetary science. The present paper is concerned with such applications. The composition of planetary interiors is discussed, taking into account the division of the major constituent of the planets in three groups on the basis of 'cosmic abundance' arguments, the H-He mixtures in the case of Jupiter and Saturn, <span class="hlt">shock</span> <span class="hlt">wave</span> data for hydrogen, and constraints on the internal structure of Uranus and Neptune. Attention is also given to the earth's mantle, <span class="hlt">shock</span> <span class="hlt">wave</span> data for mantle materials, the earth's core, impacts on planetary surfaces, elastic <span class="hlt">wave</span> velocities as a function of pressure along the Hugoniot of iron, and reactions which yield the CO2 bearing atmospheres for Venus, earth, and Mars.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009APS..DFD.K1001C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009APS..DFD.K1001C"><span id="translatedtitle">Unsteadiness of <span class="hlt">Shock</span> <span class="hlt">Wave</span> / Boundary Layer Interactions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Clemens, Noel</p> <p>2009-11-01</p> <p><span class="hlt">Shock</span> <span class="hlt">wave</span> / boundary layer interactions are an important feature of high-speed flows that occur in a wide range of practical configurations including aircraft control surfaces, inlets, missile base flows, nozzles, and rotating machinery. These interactions are often associated with severe boundary layer separation, which is highly unsteady, and exhibits high fluctuating pressure and heat loads. The unsteady motions are characterized by a wide range of frequencies, including low-frequency motions that are about two orders of magnitude lower than those that characterize the upstream boundary layer. It is these low-frequency motions that are of most interest because they have been the most difficult to explain and model. Despite significant work over the past few decades, the source of the low-frequency motions remains a topic of intense debate. Owing to a flurry of activity over the past decade on this single topic we are close to developing a comprehensive understanding of the low-frequency unsteadiness. For example, recent work in our laboratory and others suggests that the driving mechanism is related to low-frequency fluctuations in the upstream boundary layer. However, several recent studies suggest the dominant mechanism is an intrinsic instability of the separated flow. Here we attempt to reconcile these views by arguing that the low-frequency unsteadiness is driven by both upstream and downstream processes, but the relative importance of each mechanism depends on the strength (or length-scale) of separation. In cases where the separation bubble is relatively small, then the flow is intermittently separated, and there exists a strong correlation between upstream velocity fluctuations and the separation bubble dynamics. It appears that superstructures in the upstream boundary layer can play an important role in driving the unsteadiness for this case. It is not clear, however, if the upstream fluctuations directly move the separation point or indirectly couple</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20140010226','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20140010226"><span id="translatedtitle">Hybrid Simulation of the <span class="hlt">Shock</span> <span class="hlt">Wave</span> Trailing the Moon</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Israelevich, P.; Ofman, Leon</p> <p>2012-01-01</p> <p>A standing <span class="hlt">shock</span> <span class="hlt">wave</span> behind the Moon was predicted by Michel (1967) but never observed nor simulated. We use 1D hybrid code in order to simulate the collapse of the plasma-free cavity behind the Moon and for the first time to model the formation of this <span class="hlt">shock</span>. Starting immediately downstream of the obstacle we consider the evolution of plasma expansion into the cavity in the frame of reference moving along with the solar wind. Well-known effects as electric charging of the cavity affecting the plasma flow and counterstreaming ion beams in the wake are reproduced. Near the apex of the inner Mach cone where the plasma flows from the opposite sides of the obstacle meet, a <span class="hlt">shock</span> <span class="hlt">wave</span> arises. We expect the <span class="hlt">shock</span> to be produced at periods of high electron temperature solar wind streams (T(sub i) much less than T(sub e) approximately 100 eV). The <span class="hlt">shock</span> is produced by the interaction of oppositely directed proton beams in the plane containing solar wind velocity and interplanetary magnetic field vectors. In the direction across the magnetic field and the solar wind velocity, the <span class="hlt">shock</span> results from the interaction of the plasma flow with the region of the enhanced magnetic field inside the cavity that plays the role of the magnetic barrier. The appearance of the standing <span class="hlt">shock</span> <span class="hlt">wave</span> is expected at the distance of approximately 7R(sub M) downstream of the Moon.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/6053909','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/6053909"><span id="translatedtitle">Isotope systematics and <span class="hlt">shock-wave</span> metamorphism: I. U-Pb in zircon, titanite, and monazite, <span class="hlt">shocked</span> experimentally up to 59 GPa</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Deutsch, A. ); Schaerer, U. )</p> <p>1990-12-01</p> <p>This study reports the first U-Pb isotope analyses on experimentally <span class="hlt">shocked</span> zircon, titanite, and monazite extracted from Proterozoic granitoid rocks. In all three types of minerals, <span class="hlt">shock-waves</span> produce drastic changes in the crystal lattices, causing strong lowering of birefringence, turbidization, and decolorization of the individual grains. Moreover, X-ray patterns indicate transition of the crystals into polycrystalline aggregates of <10{sup {minus}5} mm block-size. Precisely dated grains with concordant or nearly concordant ages were embedded in KBr and <span class="hlt">shocked</span> at 35, 47.5, and 59 GPa. U-Pb isotope analyses on these grains show that <span class="hlt">shock</span> metamorphism does not fractionate Pb isotopes within the analytical precision of {plus minus}0.1%. As far as chemical fractionation is concerned, there is no difference in degree of concordancy between <span class="hlt">shocked</span> and unshocked monazite, and small degrees (<2%) of relative U/Pb fractionation in <span class="hlt">shocked</span> zircon and titanite are due to time-integrated Pb-loss and not to the <span class="hlt">shock</span> experiment. In consequence, the data document that <span class="hlt">shock-wave</span> metamorphism alone does not measurably effect the U-Pb chronometer, questioning the view that lower intercept ages of discordant U-Pb data <span class="hlt">reflect</span> <span class="hlt">shock</span>-induced re-equilibration of the chronometer in moderately to highly <span class="hlt">shocked</span>, rapidly cooling rocks.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012ShWav..22..253S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012ShWav..22..253S"><span id="translatedtitle">Analysis of <span class="hlt">reflected</span> blast <span class="hlt">wave</span> pressure profiles in a confined room</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sauvan, P. E.; Sochet, I.; Trélat, S.</p> <p>2012-05-01</p> <p>To understand the blast effects of confined explosions, it is necessary to study the characteristic parameters of the blast <span class="hlt">wave</span> in terms of overpressure, impulse and arrival time. In a previous study, experiments were performed using two different scales of a pyrotechnic workshop. The main purpose of these experiments was to compare the TNT equivalent for solid and gaseous explosives in terms of mass to define a TNT equivalent in a <span class="hlt">reflection</span> field and to validate the similitude between real and small scales. To study the interactions and propagations of the <span class="hlt">reflected</span> <span class="hlt">shock</span> <span class="hlt">waves</span>, the present study was conducted by progressively building a confined volume around the charge. In this way, the influence of each wall and the origins of the <span class="hlt">reflected</span> <span class="hlt">shock</span> <span class="hlt">waves</span> can be determined. The purpose of this paper is to report the blast <span class="hlt">wave</span> interactions that resulted from the detonation of a stoichiometric propane-oxygen mixture in a confined room.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016PhFl...28e6102S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016PhFl...28e6102S"><span id="translatedtitle">Plane <span class="hlt">shock</span> <span class="hlt">wave</span> interaction with a cylindrical water column</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sembian, S.; Liverts, M.; Tillmark, N.; Apazidis, N.</p> <p>2016-05-01</p> <p>A complex system of <span class="hlt">waves</span> propagating inside a water column due to the impact of plane <span class="hlt">shock</span> <span class="hlt">wave</span> is investigated both experimentally and numerically. Flow features, such as, focusing of expansion <span class="hlt">waves</span> generating large negative pressure, nucleation of cavitation bubbles, and a re-circulation zone are observed and discussed qualitatively and quantitatively. Experiments are conducted on a 22 mm diametrical water column hit by <span class="hlt">shock</span> <span class="hlt">waves</span> with Mach numbers 1.75 and 2.4 in a newly constructed exploding wire facility. A new technique to create a properly shaped, repeatable, large diameter water column with straight walls is presented. Qualitative features of the flow are captured using the shadowgraph technique. With the aid of numerical simulations the <span class="hlt">wave</span> motions inside the column are analyzed; the spatial location of the expansion <span class="hlt">wave</span> focusing point and the corresponding negative peak pressures is estimated.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/21367305','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/21367305"><span id="translatedtitle">Visualization of <span class="hlt">Shock</span> <span class="hlt">Wave</span> Driven by Millimeter <span class="hlt">Wave</span> Plasma in a Parabolic Thruster</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Yamaguchi, Toshikazu; Shimada, Yutaka; Shiraishi, Yuya; Shibata, Teppei; Komurasaki, Kimiya; Oda, Yasuhisa; Kajiwara, Ken; Takahashi, Koji; Kasugai, Atsushi; Sakamoto, Keishi; Arakawa, Yoshihiro</p> <p>2010-05-06</p> <p>By focusing a high-power millimeter <span class="hlt">wave</span> beam generated by a 170 GHz gyrotron, a breakdown occurred and a <span class="hlt">shock</span> <span class="hlt">wave</span> was driven by plasma heated by following microwave energy. The <span class="hlt">shock</span> <span class="hlt">wave</span> and the plasma around a focal point of a parabolic thruster were visualized by a shadowgraph method, and a transition of structures between the <span class="hlt">shock</span> <span class="hlt">wave</span> and the plasma was observed. There was a threshold local power density to make the transition, and the propagation velocity at the transition was around 800 m/s.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011APS..SHK.F1097L&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011APS..SHK.F1097L&link_type=ABSTRACT"><span id="translatedtitle">International <span class="hlt">Shock-Wave</span> Database: Systematization of Experimental Data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Levashov, Pavel R.; Khishchenko, Konstantin V.; Lomonosov, Igor V.; Minakov, Dmitry V.; Zakharenkov, Alexey S.</p> <p>2011-06-01</p> <p>In this work, we announce the creation of the International <span class="hlt">Shock-Wave</span> Database (ISWDB). <span class="hlt">Shock-wave</span> and related dynamic material response data serve for calibrating, validating, and improving material models over very broad regions of the pressure-temperature-density phase space. Our objectives are (i) to develop a database on thermodynamic and mechanical properties of materials under conditions of <span class="hlt">shock</span> <span class="hlt">wave</span> and other dynamic loadings, selected related quantities of interest, and the meta-data that describes the provenance of the measurements and material models, and (ii) to make this database available internationally thru the Internet, in an interactive form. The development and operation of the ISWDB will be guided by input from a steering committee. The database will be installed on two mirrored web-servers, one in Russia and the other in USA. The database will provide access to original experimental data on <span class="hlt">shock</span> compression, non-<span class="hlt">shock</span> dynamic loadings, isentropic expansion, measurements of sound speed in the Hugoniot state, and time-dependent free-surface or window-interface velocity profiles. We believe that the ISWDB will be a useful tool for the <span class="hlt">shock-wave</span> community.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014ApPhL.105r1111C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014ApPhL.105r1111C"><span id="translatedtitle">Ultrabroadband <span class="hlt">reflective</span> polarization convertor for terahertz <span class="hlt">waves</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cheng, Yong Zhi; Withayachumnankul, Withawat; Upadhyay, Aditi; Headland, Daniel; Nie, Yan; Gong, Rong Zhou; Bhaskaran, Madhu; Sriram, Sharath; Abbott, Derek</p> <p>2014-11-01</p> <p>We design and experimentally demonstrate an ultrathin, ultrabroadband, and highly efficient <span class="hlt">reflective</span> linear polarization convertor or half-<span class="hlt">wave</span> retarder operating at terahertz frequencies. The metamaterial-inspired convertor is composed of metallic disks and split-ring resonators placed over a ground plane. The structure exhibits three neighboring resonances, by which the linear polarization of incident <span class="hlt">waves</span> can be converted to its orthogonal counterpart upon <span class="hlt">reflection</span>. For an optimal design, a measured polarization conversion ratio for normal incidence is greater than 80% in the range of 0.65-1.45 THz, equivalent to 76% relative bandwidth. The mechanism for polarization conversion is explained via decomposed electric field components that couple with different resonance modes of the structure. The proposed metamaterial design for enhancing efficiency of polarization conversion has potential applications in the area of terahertz spectroscopy, imaging, and communications.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4319177','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4319177"><span id="translatedtitle">Radial extracorporeal <span class="hlt">shock</span> <span class="hlt">wave</span> treatment harms developing chicken embryos</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Kiessling, Maren C.; Milz, Stefan; Frank, Hans-Georg; Korbel, Rüdiger; Schmitz, Christoph</p> <p>2015-01-01</p> <p>Radial extracorporeal <span class="hlt">shock</span> <span class="hlt">wave</span> treatment (rESWT) has became one of the best investigated treatment modalities for cellulite, including the abdomen as a treatment site. Notably, pregnancy is considered a contraindication for rESWT, and concerns have been raised about possible harm to the embryo when a woman treated with rESWT for cellulite is not aware of her pregnancy. Here we tested the hypothesis that rESWT may cause serious physical harm to embryos. To this end, chicken embryos were exposed in ovo to various doses of radial <span class="hlt">shock</span> <span class="hlt">waves</span> on either day 3 or day 4 of development, resembling the developmental stage of four- to six-week-old human embryos. We found a dose-dependent increase in the number of embryos that died after radial <span class="hlt">shock</span> <span class="hlt">wave</span> exposure on either day 3 or day 4 of development. Among the embryos that survived the <span class="hlt">shock</span> <span class="hlt">wave</span> exposure a few showed severe congenital defects such as missing eyes. Evidently, our data cannot directly be used to draw conclusions about potential harm to the embryo of a pregnant woman treated for cellulite with rESWT. However, to avoid any risks we strongly recommend applying radial <span class="hlt">shock</span> <span class="hlt">waves</span> in the treatment of cellulite only if a pregnancy is ruled out. PMID:25655309</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19860026497&hterms=Sound+waves&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3D%2528Sound%2Bwaves%2529','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19860026497&hterms=Sound+waves&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3D%2528Sound%2Bwaves%2529"><span id="translatedtitle">Cylindrical sound <span class="hlt">wave</span> generated by <span class="hlt">shock</span>-vortex interaction</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Ribner, H. S.</p> <p>1985-01-01</p> <p>The passage of a columnar vortex broadside through a <span class="hlt">shock</span> is investigated. This has been suggested as a crude, but deterministic, model of the generation of '<span class="hlt">shock</span> noise' by the turbulence in supersonic jets. The vortex is decomposed by Fourier transform into plane sinusoidal shear <span class="hlt">waves</span> disposed with radial symmetry. The plane sound <span class="hlt">waves</span> produced by each shear <span class="hlt">wave/shock</span> interaction are recombined in the Fourier integral. The <span class="hlt">waves</span> possess an envelope that is essentially a growing cylindrical sound <span class="hlt">wave</span> centered at the transmitted vortex. The pressure jump across the nominal radius R = ct attenuates with time as 1/(square root of R) and varies around the arc in an antisymmetric fashion resembling a quadrupole field. Very good agreement, except near the <span class="hlt">shock</span>, is found with the antisymmetric component of reported interferometric measurements in a <span class="hlt">shock</span> tube. Beyond the front r approximately equals R is a precursor of opposite sign, that decays like 1/R, generated by the 1/r potential flow around the vortex core. The present work is essentially an extension and update of an early approximate study at M = 1.25. It covers the range (R/core radius) = 10, 100, 1000, and 10,000 for M = 1.25 and (in part) for M = 1.29 and, for fixed (R/core radius) = 1000, the range M = 1.01 to infinity.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2012AIPC.1503....2K&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2012AIPC.1503....2K&link_type=ABSTRACT"><span id="translatedtitle">Effects of low-dose extracorporeal <span class="hlt">shock</span> <span class="hlt">waves</span> on microcirculation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Khaled, Walaa; Goertz, Ole; Lauer, Henrik; Lehnhardt, Marcus; Hauser, Jörg</p> <p>2012-11-01</p> <p>The extended wounds of burn patients remain a challenge due to wound infection and following septicemia. The aim of this study was to analyze microcirculation, angiogenesis and leukocyte endothelium interaction after burn injury with and without extracorporeal <span class="hlt">shock</span> <span class="hlt">wave</span> application (ESWA). A novel shockwave system was developed based on a commercially available device for orthopedics (Dornier Aries®) that was equipped with a newly developed applicator. This system is based on the electromagnetic <span class="hlt">shock</span> <span class="hlt">wave</span> emitter (EMSE) technology and was introduced to accomplish a localized treatment for wound healing. The system includes a novel field of focus for new applications, with high precision and ease of use. In the animal study, full-thickness burns were inflicted on to the ears of hairless mice (n=51). Intravital fluorescent microscopy was used to assess microcirculatory parameters, angiogenesis and leukocyte behavior. ESWA was performed on day 1, 3 and 7. Values were obtained immediately after burn, as well as at days 1, 3, 7, and 12 post burn. All shockwave treated groups showed an accelerated angiogenesis with a less non-perfused area and an improved blood flow after burn injury compared to the placebo control group. After three treatments, the <span class="hlt">shock</span> <span class="hlt">waves</span> increased the number of rolling leukocytes significantly compared to the non-treated animals. <span class="hlt">Shock</span> <span class="hlt">waves</span> seem to have a positive effect on several parameters of wound healing after burn injury. However, further investigations are necessary to detect positive influence of <span class="hlt">shock</span> <span class="hlt">waves</span> on microcirculation after burn injuries.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_18 --> <div id="page_19" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="361"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003ASAJ..114.2463W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003ASAJ..114.2463W"><span id="translatedtitle">Treatment of nonunions of long bone fractures with <span class="hlt">shock</span> <span class="hlt">waves</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wang, Ching-Jen</p> <p>2003-10-01</p> <p>A prospective clinical study investigated the effectiveness of <span class="hlt">shock</span> <span class="hlt">waves</span> in the treatment of 72 patients with 72 nonunions of long bone fractures (41 femurs, 19 tibias, 7 humeri, 1 radius, 3 ulnas and 1 metatarsal). The doses of <span class="hlt">shock</span> <span class="hlt">waves</span> were 6000 impulses at 28 kV for the femur and tibia, 3000 impulses at 28 kV for the humerus, 2000 impulses at 24 kV for the radius and ulna, and 1000 impulses at 20 kV for the metatarsal. The results of treatment were assessed clinically, and fracture healing was assessed with plain x-rays and tomography. The rate of bony union was 40% at 3 months, 60.9% at 6 months and 80% at 12 months followup. <span class="hlt">Shock</span> <span class="hlt">wave</span> treatment was most successful in hypertrophic nonunions and nonunions with a defect and was least effective in atrophic nonunions. There were no systemic complications or device-related problems. Local complications included petechiae and hematoma formation that resolved spontaneously. In the author's experience, the results of the <span class="hlt">shock</span> <span class="hlt">wave</span> treatment were similar to the results of surgical treatment for chronic nonunions with no surgical risks. <span class="hlt">Shock</span> <span class="hlt">wave</span> treatment is a safe and effective alternative method in the treatment of chronic nonunions of long bones.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015JPhCS.653a2045P&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015JPhCS.653a2045P&link_type=ABSTRACT"><span id="translatedtitle">Numerical investigations of <span class="hlt">shock</span> <span class="hlt">wave</span> propagation in polymethylmethacrylate</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Popova, T. V.; Mayer, A. E.; Khishchenko, K. V.</p> <p>2015-11-01</p> <p>Using the Maxwell model of viscoelastic medium, we numerically investigate the influence of the viscoelastic properties of polymethylmethacrylate on the variation of the <span class="hlt">shock</span> <span class="hlt">wave</span> amplitude with depth. Parameters of the Maxwell model are chosen by comparison with experimental data on the high-speed impact of plates in order to fit the modeling results with the experimentally measured profiles of the free-surface velocity. A caloric equation of state is used to calculate the pressure from density and internal energy. It is shown that at the limit of weak <span class="hlt">shock</span> <span class="hlt">waves</span>, the accounting of the viscoelastic properties allows one to achieve a better agreement between calculated and experimental data for the magnitude of the <span class="hlt">shock</span> <span class="hlt">wave</span> velocity in comparison with the case of hydrodynamic calculations. Using the viscoelastic and hydrodynamic approaches, we investigated the dynamics of <span class="hlt">shock</span> <span class="hlt">waves</span> in polymethylmethacrylate initiated by micro-, nano- and picosecond pulses of pressure on the sample surface. The calculation results show that the changes in the <span class="hlt">shock</span> <span class="hlt">wave</span> amplitude with depth are approximately identical in the hydrodynamic and viscoelastic cases.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014ShWav..24....3S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014ShWav..24....3S"><span id="translatedtitle">Experimental study on a heavy-gas cylinder accelerated by cylindrical converging <span class="hlt">shock</span> <span class="hlt">waves</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Si, T.; Zhai, Z.; Luo, X.; Yang, J.</p> <p>2014-01-01</p> <p>The Richtmyer-Meshkov instability behavior of a heavy-gas cylinder accelerated by a cylindrical converging <span class="hlt">shock</span> <span class="hlt">wave</span> is studied experimentally. A curved wall profile is well-designed based on the <span class="hlt">shock</span> dynamics theory [Phys. Fluids, 22: 041701 (2010)] with an incident planar <span class="hlt">shock</span> Mach number of 1.2 and a converging angle of in a mm square cross-section <span class="hlt">shock</span> tube. The cylinder mixed with the glycol droplets flows vertically through the test section and is illuminated horizontally by a laser sheet. The images obtained only one per run by an ICCD (intensified charge coupled device) combined with a pulsed Nd:YAG laser are first presented and the complete evolution process of the cylinder is then captured in a single test shot by a high-speed video camera combined with a high-power continuous laser. In this way, both the developments of the first counter-rotating vortex pair and the second counter-rotating vortex pair with an opposite rotating direction from the first one are observed. The experimental results indicate that the phenomena induced by the converging <span class="hlt">shock</span> <span class="hlt">wave</span> and the <span class="hlt">reflected</span> <span class="hlt">shock</span> formed from the center of convergence are distinct from those found in the planar <span class="hlt">shock</span> case.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/6525673','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/6525673"><span id="translatedtitle">Plane <span class="hlt">shock</span> <span class="hlt">wave</span> studies of Westerly granite and Nugget sandstone</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Larson, D.B.; Anderson, G.D.</p> <p>1980-12-01</p> <p>Plane <span class="hlt">shock</span> <span class="hlt">wave</span> experiments were performed by using a light-gas gun on dry and water-saturated Westerly granite and dry Nugget sandstone. Changes in the slopes of the <span class="hlt">shock</span> velocity versus particle velocity curves at 2 to 3 GPa and 1 to 2 GPa for dry granite and for dry sandstone, respectively, are attributed to the onset of pore collapse. However, there is little apparent loss of shear strength in either dry rock over the stress range of the experiments (i.e., 9.3 GPa in Westerly granite and 9.2 GPa in Nugget sandstone). Agreement between the <span class="hlt">shock</span> <span class="hlt">wave</span> data and quasistatic, uniaxial strain data for the dry rock implies the absence of rate-dependence in uniaxial strain. The <span class="hlt">shock</span> data on saturated granite agree well with those for dry granite, thus suggesting there was no loss in shear strength as a result of pore pressure buildup.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19750033814&hterms=blast+wave&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dblast%2Bwave','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19750033814&hterms=blast+wave&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dblast%2Bwave"><span id="translatedtitle">Hypersonic flows generated by parabolic and paraboloidal <span class="hlt">shock</span> <span class="hlt">waves</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Schwartz, L. W.</p> <p>1974-01-01</p> <p>A computer algorithm has been developed to determine the blunt-body flowfields supporting symmetric parabolic and paraboloidal <span class="hlt">shock</span> <span class="hlt">waves</span> at infinite free-stream Mach number. Solutions are expressed in an analytic form as high-order power series, in the coordinate normal to the <span class="hlt">shock</span>, whose coefficients can be determined exactly. Analytic continuation is provided by the use of Pade approximations. Test cases provide solutions of very high accuracy. In the axisymmetric case for gamma equals 715 the solution has been found far downstream, where it agrees with the modified blast-<span class="hlt">wave</span> results. For plane flow, on the other hand, a limit line appears within the <span class="hlt">shock</span> layer, a short distance past the sonic line, suggesting the presence of an imbedded <span class="hlt">shock</span>. Local solutions in the downstream limit are discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016PhRvD..94b5004L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016PhRvD..94b5004L"><span id="translatedtitle"><span class="hlt">Shock</span> <span class="hlt">waves</span>, rarefaction <span class="hlt">waves</span>, and nonequilibrium steady states in quantum critical systems</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lucas, Andrew; Schalm, Koenraad; Doyon, Benjamin; Bhaseen, M. J.</p> <p>2016-07-01</p> <p>We reexamine the emergence of a universal nonequilibrium steady state following a local quench between quantum critical heat baths in spatial dimensions greater than one. We show that energy transport proceeds by the formation of an instantaneous <span class="hlt">shock</span> <span class="hlt">wave</span> and a broadening rarefaction <span class="hlt">wave</span> on either side of the interface, and not by two <span class="hlt">shock</span> <span class="hlt">waves</span> as previously proposed. For small temperature differences the universal steady state energy currents of the two-<span class="hlt">shock</span> and rarefaction-<span class="hlt">shock</span> solutions coincide. Over a broad range of parameters, the difference in the energy flow across the interface between these two solutions is at the level of 2%. The properties of the energy flow remain fully universal and independent of the microscopic theory. We briefly discuss the width of the <span class="hlt">shock</span> <span class="hlt">wave</span> in a viscous fluid, the effects of momentum relaxation, and the generalization to charged fluids.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014A%26A...565A..73G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014A%26A...565A..73G"><span id="translatedtitle">Emission lines and <span class="hlt">shock</span> <span class="hlt">waves</span> in RR Lyrae stars</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gillet, D.; Fokin, A. B.</p> <p>2014-05-01</p> <p>Context. Emission lines observed in radially pulsating stars are thought to be produced by atoms de-exciting after being excited by a <span class="hlt">shock</span> <span class="hlt">wave</span> that is traveling into and then compressing, heating, and accelerating the atmospheric gas. Aims: With the help of recent observations, we examine the origin of all the different types of emission lines of hydrogen and helium that appear during a pulsation cycle. Methods: To analyze the physical origin of emission lines, we used the different models of atmospheric dynamics of RR Lyrae stars that have been calculated so far. Results: In contrast to a recent explanation, we propose that the redshifted emission component of Hα, which occurs near the pulsation phase 0.3, is produced by the main <span class="hlt">shock</span>. In this case, the emission is the natural consequence of the large extension of the expanding atmosphere. Therefore, this (weak) emission should only be observed in RR Lyrae stars for which the main <span class="hlt">shock</span> will propagate far enough from the photosphere. It appears as a P-Cygni type profile. We estimate the <span class="hlt">shock</span> front velocity during the <span class="hlt">shock</span> propagation in the atmosphere and show that it decreases by 40% when the Hα emitting-<span class="hlt">shock</span> passes from the photospheric level to the upper atmosphere. The Hα P-Cygni profile observed in long-period Cepheids also seems to be caused by the main <span class="hlt">shock</span> <span class="hlt">wave</span>. Although to date He II has only been detected in some Blazhko stars, a comprehensive survey of RR Lyrae stars is necessary to confirm this trend, so we can say that the most intense <span class="hlt">shocks</span> will only be observed in Blazhko stars. Conclusions: The development of a model of atmospheric pulsation that takes the effects of 2D and 3D convection into account, seems to be a necessary step to fully quantify the effects of <span class="hlt">shock</span> <span class="hlt">waves</span> on the atmospheric dynamics of radially pulsating stars.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19820008935','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19820008935"><span id="translatedtitle">A <span class="hlt">shock</span> <span class="hlt">wave</span> approach to the noise of supersonic propellers</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Dittmar, J. H.; Rice, E. J.</p> <p>1981-01-01</p> <p>To model propeller noise expected for a turboprop aircraft, the pressure ratio across the <span class="hlt">shock</span> at the propeller tip was calculated and compared with noise data from three propellers. At helical tip Mach numbers over 1.0, using only the tip <span class="hlt">shock</span> <span class="hlt">wave</span>, the model gave a fairly good prediction of the noise for a bladed propeller and for a propeller swept for aerodynamic purposes. However for another propeller, which was highly swept and designed to have noise cancellations from the inboard propeller sections, the <span class="hlt">shock</span> strength from the tip over predicted the noise. In general the good agreement indicates that <span class="hlt">shock</span> theory is a viable method for predicting the noise from these supersonic propellers but that the <span class="hlt">shock</span> strengths from all of the blade sections need to be properly included.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19850036956&hterms=theta+waves&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dtheta%2Bwaves','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19850036956&hterms=theta+waves&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dtheta%2Bwaves"><span id="translatedtitle"><span class="hlt">Shock</span> drift acceleration in the presence of <span class="hlt">waves</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Decker, R. B.; Vlahos, L.</p> <p>1985-01-01</p> <p>Attention is given to the initial results of a model designed to study the modification of the scatter-free, <span class="hlt">shock</span> drift acceleration of energetic test particles by <span class="hlt">wave</span> activity in the vicinity of a quasi-perpendicular, fast-mode MHD <span class="hlt">shock</span>. It is emphasized that the concept of magnetic moment conservation is a valid approximation only in the perpendicular and nearly perpendicular regimes, when the angle theta-Bn between the <span class="hlt">shock</span> normal and the upstream magnetic field vector is in the range from 70 deg to 90 deg. The present investigation is concerned with one step in a program which is being developed to combine the <span class="hlt">shock</span> drift and diffusive processes at a <span class="hlt">shock</span> of arbitrary theta-Bn.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19730015974','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19730015974"><span id="translatedtitle">Ion streaming instabilities with application to collisionless <span class="hlt">shock</span> <span class="hlt">wave</span> structure</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Golden, K. I.; Linson, L. M.; Mani, S. A.</p> <p>1973-01-01</p> <p>The electromagnetic dispersion relation for two counterstreaming ion beams of arbitrary relative strength flowing parallel to a dc magnetic field is derived. The beams flow through a stationary electron background and the dispersion relation in the fluid approximation is unaffected by the electron thermal pressure. The dispersion relation is solved with a zero net current condition applied and the regions of instability in the k-U space (U is the relative velocity between the two ion beams) are presented. The parameters are then chosen to be applicable for parallel <span class="hlt">shocks</span>. It was found that unstable <span class="hlt">waves</span> with zero group velocity in the <span class="hlt">shock</span> frame can exist near the leading edge of the <span class="hlt">shock</span> for upstream Alfven Mach numbers greater than 5.5. It is suggested that this mechanism could generate sufficient turbulence within the <span class="hlt">shock</span> layer to scatter the incoming ions and create the required dissipation for intermediate strength <span class="hlt">shocks</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19980223576','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19980223576"><span id="translatedtitle">Effect of Surface Roughness on Characteristics of Spherical <span class="hlt">Shock</span> <span class="hlt">Waves</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Huber, Paul W.; McFarland, Donald R.</p> <p>1959-01-01</p> <p>Measurements of peak overpressure and Mach stem height were made at four burst heights. Data were obtained with instrumentation capable of directly observing the variation of <span class="hlt">shock</span> <span class="hlt">wave</span> movement with time. Good similarity of free air <span class="hlt">shock</span> peak overpressure with larger scale data was found to exist. The net effect of surface roughness on <span class="hlt">shock</span> peak overpressures slightly. Surface roughness delayed the Mach stem formation at the greatest charge height and lowered the growth at all burst heights. A similarity parameter was found which approximately correlates the triple point path at different burst heights.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014JPhCS.500n2029R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014JPhCS.500n2029R"><span id="translatedtitle">Fibre Bragg Grating sensor for <span class="hlt">shock</span> <span class="hlt">wave</span> diagnostics</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ravid, A.; Shafir, E.; Zilberman, S.; Berkovic, G.; Glam, B.; Appelbaum, G.; Fedotov Gefen, A.</p> <p>2014-05-01</p> <p>We measured the response of short FBGs to a weak planar <span class="hlt">shock</span> <span class="hlt">wave</span>. The combined effect of the Photo-Elastic effect and the FBG strain was estimated theoretically depending on its orientation with respect to <span class="hlt">shock</span> front (for 1550 nm FBG, parallel: 0.9 nm/kbar, perpendicular: -1.4 nm/kbar). The experimental results imply that the FBG/fibre survives for more than 1 μs at 5 kbar <span class="hlt">shock</span> stress, and that our assumptions about the FBG behaviour under dynamic loading are valid, though more work is needed to fully quantify the effect.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19860041641&hterms=ohm+law&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dohm%2527s%2Blaw','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19860041641&hterms=ohm+law&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dohm%2527s%2Blaw"><span id="translatedtitle">Hybrid simulation codes with application to <span class="hlt">shocks</span> and upstream <span class="hlt">waves</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Winske, D.</p> <p>1985-01-01</p> <p>Hybrid codes in which part of the plasma is represented as particles and the rest as a fluid are discussed. In the past few years such codes with particle ions and massless, fluid electrons have been applied to space plasmas, especially to collisionless <span class="hlt">shocks</span>. All of these simulation codes are one-dimensional and similar in structure, except for how the field equations are solved. The various approaches that are used (resistive Ohm's law, predictor-corrector, Hamiltonian) are described in detail and results from the various codes are compared with examples taken from collisionless <span class="hlt">shocks</span> and low frequency <span class="hlt">wave</span> phenomena upstream of <span class="hlt">shocks</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1990AIPC..208..831L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1990AIPC..208..831L"><span id="translatedtitle">Air bubble-<span class="hlt">shock</span> <span class="hlt">wave</span> interaction adjacent to gelantine surface</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lush, P. A.; Tomita, Y.; Onodera, O.; Takayama, K.; Sanada, N.; Kuwahara, M.; Ioritani, N.; Kitayama, O.</p> <p>1990-07-01</p> <p>The interaction between a <span class="hlt">shock</span> <span class="hlt">wave</span> and an air bubble-adjacent to a gelatine surface is investigated in order to simulate human tissue damage resulting from extracorporeal <span class="hlt">shock</span> <span class="hlt">wave</span> lithotripsy. Using high speed cine photography it is found that a <span class="hlt">shock</span> <span class="hlt">wave</span> of strength 11 MPa causes 1-3 mm diameter bubbles to produce high velocity microjets with penetration rates of approximately 110 m/s and penetration depths approximately equal to twice the initial bubble diameter. Theoretical considerations for liquid impact on soft solid of similar density indicate that microjet velocities will be twice the penetration rate, i.e. 220 m/s in the present case. Such events are the probable cause of observed renal tissue damage.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19940010727&hterms=phenomena+wave&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dphenomena%2Bwave','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19940010727&hterms=phenomena+wave&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dphenomena%2Bwave"><span id="translatedtitle">Unsteady Phenomena in <span class="hlt">Shock</span> <span class="hlt">Wave</span>/Boundary Layer Interaction</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Dolling, D. S.</p> <p>1993-01-01</p> <p>A brief review is given of the unsteadiness of <span class="hlt">shock</span> <span class="hlt">wave</span>/turbulent boundary layer interaction. The focus is on interactions generated by swept and unswept compression ramps, by flares, steps and incident <span class="hlt">shock</span> <span class="hlt">waves</span>, by cylinders and blunt fins, and by glancing <span class="hlt">shock</span> <span class="hlt">waves</span>. The effects of Mach number, Reynolds number, and separated flow scale are discussed as are the physical causes of the unsteadiness. The implications that the unsteadiness has for interpreting time-average surface and flowfield data, and for comparisons of such experimental data with computation, is also briefly discussed. Finally, some suggestions for future work are given. It is clear that there are large gaps in the data base and that many aspects of such phenomena are poorly understood. Much work remains to be done.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1992JSMET..58..153P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1992JSMET..58..153P"><span id="translatedtitle">Oscillation of circular <span class="hlt">shock</span> <span class="hlt">waves</span> with upstream nonuniformity</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Park, Myeong-Kwan; Oshima, Shuzo; Yamane, Ryuichiro</p> <p>1992-01-01</p> <p>Up to previous reports by Park et al. on the oscillation of the circular <span class="hlt">shock</span> <span class="hlt">waves</span>, the investigations have been concerned with situations where the upstream flow is uniform, and oscillation and deformation were induced by only downstream conditions. But in the centrifugal diffuser of a centrifugal compressor, the flow into the diffuser becomes nonuniform due to the impeller wake and the stall in the upstream impeller, which causes deformation and oscillation of the <span class="hlt">shock</span> <span class="hlt">wave</span>. Here, the above effects are considered, and the upstream disturbance is generated by cylindrical bars. The imperfect circular <span class="hlt">shock</span> <span class="hlt">wave</span> was induced by the effect of the wake, and the oscillation state, along with the oscillation modes caused by forced oscillation, is investigated experimentally. It was found that the basic mode of the oscillation is predominant and that the oscillation is weaker than in the case of uniform upstream.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19770021307','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19770021307"><span id="translatedtitle">Chemical kinetic modeling of propane oxidation behind <span class="hlt">shock</span> <span class="hlt">waves</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Mclain, A. G.; Jachimowski, C. J.</p> <p>1977-01-01</p> <p>The stoichiometric combustion of propane behind incident <span class="hlt">shock</span> <span class="hlt">waves</span> was studied experimentally and analytically over a temperature range from 1700 K to 2600 K and a pressure range from 1.2 to 1.9 atm. Measurements of the concentrations of carbon monoxide (CO) and carbon dioxide (CO2) and the product of the oxygen atom and carbon dioxide concentrations (O)(CO) were made after passage of the incident <span class="hlt">shock</span> <span class="hlt">wave</span>. A kinetic mechanism was developed which, when used in a computer program for a flowing, reacting gas behind an incident <span class="hlt">shock</span> <span class="hlt">wave</span> predicted experimentally measured results quite well. Ignition delay times from the literature were also predicted quite well. The kinetic mechanism consisted of 59 individual kinetic steps.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/24680880','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/24680880"><span id="translatedtitle">Tandem <span class="hlt">shock</span> <span class="hlt">waves</span> to enhance genetic transformation of Aspergillus niger.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Loske, Achim M; Fernández, Francisco; Magaña-Ortíz, Denis; Coconi-Linares, Nancy; Ortíz-Vázquez, Elizabeth; Gómez-Lim, Miguel A</p> <p>2014-08-01</p> <p>Filamentous fungi are used in several industries and in academia to produce antibiotics, metabolites, proteins and pharmaceutical compounds. The development of valuable strains usually requires the insertion of recombinant deoxyribonucleic acid; however, the protocols to transfer DNA to fungal cells are highly inefficient. Recently, underwater <span class="hlt">shock</span> <span class="hlt">waves</span> were successfully used to genetically transform filamentous fungi. The purpose of this research was to demonstrate that the efficiency of transformation can be improved significantly by enhancing acoustic cavitation using tandem (dual-pulse) <span class="hlt">shock</span> <span class="hlt">waves</span>. Results revealed that tandem pressure pulses, generated at a delay of 300 μs, increased the transformation efficiency of Aspergillus niger up to 84% in comparison with conventional (single-pulse) <span class="hlt">shock</span> <span class="hlt">waves</span>. This methodology may also be useful to obtain new strains required in basic research and biotechnology. PMID:24680880</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20000086187&hterms=density+water&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Ddensity%2Bwater','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20000086187&hterms=density+water&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Ddensity%2Bwater"><span id="translatedtitle">Far-Infrared Water Emissions from Magnetohydrodynamic <span class="hlt">Shock</span> <span class="hlt">Waves</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Kaufman, Michael J.; Neufeld, David A.</p> <p>1996-01-01</p> <p>Nondissociative, magnetohydrodynamic, C-type <span class="hlt">shock</span> <span class="hlt">waves</span> are expected to be a prodigious source of far-infrared water emissions in dense interstellar regions. We have constructed a model to calculate the farinfrared H20 line spectra that emerge from such <span class="hlt">shocks</span>. Using the best estimates currently available for the radiative cooling rate and the degree of ion-neutral coupling within the <span class="hlt">shocked</span> gas, we modeled the temperature structure of MHD <span class="hlt">shocks</span> using standard methods in which the charged and neutral particles are treated separately as two weakly coupled, interpenetrating fluids. Then we solved the equations of statistical equilibrium to find the populations of the lowest 179 and 170 rotational states of ortho- and para-H2O We have completed an extensive parameter study to determine the emergent H2O line luminosities as a function of preshock density in the range n(H2) equals 10(exp 4) - 10(sup 6.5)/cc and <span class="hlt">shock</span> velocity in the range upsilon(sub s) = 5 - 40 km/ s. We find that numerous rotational transitions of water are potentially observable using the Infrared Space Observatory and the Submillimeter <span class="hlt">Wave</span> Astronomy Satellite and may be used as diagnostics of the <span class="hlt">shocked</span> gas. We have also computed the rotational and ro-vibrational emissions expected from H2, CO, and OH, and we discuss how complementary observations of such emissions may be used to further constrain the <span class="hlt">shock</span> conditions. In common with previous studies, we come close to matching the observed H2, and high-J CO emissions from the Orion-KL star-forming region on the basis of a single <span class="hlt">shock</span> model. We present our predictions for the strengths of H2O line emission from the Orion <span class="hlt">shock</span>, and we show how our results may be scaled to other regions where molecular <span class="hlt">shocks</span> are likely to be present.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1995FlDyR..17...13K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1995FlDyR..17...13K"><span id="translatedtitle">Examination of the von Neumann paradox for a weak <span class="hlt">shock</span> <span class="hlt">wave</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kobayashi, Susumu; Adachi, Takashi; Suzuki, Tateyuki</p> <p>1995-12-01</p> <p>Oblique <span class="hlt">reflections</span> of a weak <span class="hlt">shock</span> <span class="hlt">wave</span> have been investigated both theoretically and experimentally. A modified three-<span class="hlt">shock</span> theory is introduced to explain the well-known von Neumann paradox for weak Mach <span class="hlt">reflection</span>. As a physical reality, the triple point is not a mathematical point and the slipstream has a finite thickness. Consequently, the effect of the slipstream divergence behind the triple point and the minute pressure differences on both sides of the slipstream are taken into account, and both these effects are examined numerically. The angle of divergence is given parametrically in order to calculate some characteristics around the triple point, e.g., the angle of <span class="hlt">reflection</span>. Numerical results are compared with measurements, and characteristics of solutions are examined. It is found that for weak Mach <span class="hlt">reflection</span> the modified three-<span class="hlt">shock</span> theory gives physically realistic solutions, even when von Neumann's three-<span class="hlt">shock</span> theory has no solution. It is also found that the divergence effect of the slipstream is predominant over the pressure difference. All the experimental data are found to exist in the domain bounded by von Neumann's classical theories and the modified three-<span class="hlt">shock</span> theory proposed here. The experimental evidence of slipstream divergence is presented.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_19 --> <div id="page_20" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="381"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/20821262','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/20821262"><span id="translatedtitle">Potential of <span class="hlt">shock</span> <span class="hlt">waves</span> to remove calculus and biofilm.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Müller, Philipp; Guggenheim, Bernhard; Attin, Thomas; Marlinghaus, Ernst; Schmidlin, Patrick R</p> <p>2011-12-01</p> <p>Effective calculus and biofilm removal is essential to treat periodontitis. Sonic and ultrasonic technologies are used in several scaler applications. This was the first feasibility study to assess the potential of a <span class="hlt">shock</span> <span class="hlt">wave</span> device to remove calculus and biofilms and to kill bacteria. Ten extracted teeth with visible subgingival calculus were treated with either <span class="hlt">shock</span> <span class="hlt">waves</span> for 1 min at an energy output of 0.4 mJ/mm(2) at 3 Hz or a magnetostrictive ultrasonic scaler at medium power setting for 1 min, which served as a control. Calculus was determined before and after treatment planimetrically using a custom-made software using a grey scale threshold. In a second experiment, multispecies biofilms were formed on saliva-preconditioned bovine enamel discs during 64.5 h. They were subsequently treated with <span class="hlt">shock</span> <span class="hlt">waves</span> or the ultrasonic scaler (N = 6/group) using identical settings. Biofilm detachment and bactericidal effects were then assessed. Limited efficiency of the <span class="hlt">shock</span> <span class="hlt">wave</span> therapy in terms of calculus removal was observed: only 5% of the calculus was removed as compared to 100% when ultrasound was used (P ≤ 0.0001). However, <span class="hlt">shock</span> <span class="hlt">waves</span> were able to significantly reduce adherent bacteria by three orders of magnitude (P ≤ 0.0001). The extent of biofilm removal by the ultrasonic device was statistically similar. Only limited bactericidal effects were observed using both methods. Within the limitations of this preliminary study, the <span class="hlt">shock</span> <span class="hlt">wave</span> device was not able to reliably remove calculus but had the potential to remove biofilms by three log steps. To increase the efficacy, technical improvements are still required. This novel noninvasive intervention, however, merits further investigation. PMID:20821262</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19990008041&hterms=Uranus&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3DUranus','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19990008041&hterms=Uranus&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3DUranus"><span id="translatedtitle">A Study of Uranus' Bow <span class="hlt">Shock</span> Motions Using Langmuir <span class="hlt">Waves</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Xue, S.; Cairns, I. H.; Smith, C. W.; Gurnett, D. A.</p> <p>1996-01-01</p> <p>During the Voyager 2 flyby of Uranus, strong electron plasma oscillations (Langmuir <span class="hlt">waves</span>) were detected by the plasma <span class="hlt">wave</span> instrument in the 1.78-kHz channel on January 23-24, 1986, prior to the inbound bow <span class="hlt">shock</span> crossing. Langmuir <span class="hlt">waves</span> are excited by energetic electrons streaming away from the bow <span class="hlt">shock</span>. The goal of this work is to estimate the location and motion of Uranus' bow <span class="hlt">shock</span> using Langmuir <span class="hlt">wave</span> data, together with the spacecraft positions and the measured interplanetary magnetic field. The following three remote sensing analyses were performed: the basic remote sensing method, the lag time method, and the trace-back method. Because the interplanetary magnetic field was highly variable, the first analysis encountered difficulties in obtaining a realistic estimation of Uranus' bow <span class="hlt">shock</span> motion. In the lag time method developed here, time lags due to the solar wind's finite convection speed are taken into account when calculating the <span class="hlt">shock</span>'s standoff distance. In the new trace-back method, limits on the standoff distance are obtained as a function of time by reconstructing electron paths. Most of the results produced by the latter two analyses are consistent with predictions based on the standard theoretical model and the measured solar wind plasma parameters. Differences between our calculations and the theoretical model are discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1991PhDT.......168M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1991PhDT.......168M"><span id="translatedtitle">Heterogeneous <span class="hlt">Shock</span> Energy Deposition in <span class="hlt">Shock</span> <span class="hlt">Wave</span> Consolidation of Metal Powders.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mutz, Andrew Howard</p> <p></p> <p><span class="hlt">Shock</span> <span class="hlt">wave</span> consolidation of powder is a high deformation rate process in which a <span class="hlt">shock</span> <span class="hlt">wave</span> generated by an explosive or a colliding projectile rapidly densifies and bonds together the powder particles into a solid compact. The deposition of the <span class="hlt">shock</span> energy during this process is highly inhomogeneous on the powder particle scale. Evidence of the extent and pattern of the energy deposition was provided by recovery experiments performed using a crystalline metallic glass forming alloy, and analyzed using a heat flow model. The energy deposited during the <span class="hlt">shock</span> <span class="hlt">wave</span> passage was best modeled as deposited partly into the particle bulk and partly onto particle surfaces. To investigate this inhomogeneity, and the powder parameters which influence it, a propellant driven gas gun was designed, built and utilized. The planarity of the <span class="hlt">shock</span> <span class="hlt">waves</span> produced using the targets designed for the gun was established. Powder - powder thermocouples were impacted with powders of varying sizes to establish the effect of particle size on energy deposition. Small particles in contact with large ones were inferred to absorb the greater fraction of <span class="hlt">shock</span> energy. Hardened and unhardened steel powder was <span class="hlt">shocked</span> to investigate the effect of particle hardness on energy distribution. The recovered compacts were not measurably affected by the initial hardness. Compaction experiments were performed on a Ni based super-alloy and on a SiC reinforced Ti matrix composite to test some of the practical applications of the process and the target designs developed. Superior tensile properties were observed in the <span class="hlt">shock</span> consolidated and heat treated Ni based 718 alloy. The SiC reinforced composite was recovered in the intended net shape with no macro-cracks in the compact body, but with fractured SiC particles.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1993P%26SS...41..183S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1993P%26SS...41..183S"><span id="translatedtitle">Simultaneous plasma <span class="hlt">wave</span> and electron flux observations upstream of the Martian bow <span class="hlt">shock</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Skalsky, A.; Grard, R.; Kiraly, P.; Klimov, S.; Kopanyi, V.; Schwingenschuh, K.; Trotignon, J. G.</p> <p>1993-03-01</p> <p>Flux enhancements of electrons with energies between 100 and 530 eV are observed simultaneously with electron plasma <span class="hlt">waves</span> in the upstream region of the Martian bow <span class="hlt">shock</span>. The electron flux appears to reach its maximum when the pitch angle is close to 0 deg, which corresponds to particles <span class="hlt">reflected</span> from the <span class="hlt">shock</span> region and backstreaming in the solar wind along the magnetic field. The correlation between high-frequency <span class="hlt">waves</span> and enhanced electron fluxes is reminiscent of several studies on the electron foreshock of the Earth. Such a similarity indicates that, in spite of major differences between the global <span class="hlt">shock</span> structures, the microscopic processes operating in the foreshocks of Earth and Mars are probably identical.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19970016108&hterms=baker+shock&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dbaker%2Bshock','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19970016108&hterms=baker+shock&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dbaker%2Bshock"><span id="translatedtitle">Effect of Cavity Injection on Wall Drag in a Supersonic Flow with <span class="hlt">Reflecting</span> <span class="hlt">Shocks</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Castiglone, L. A.; Northam, G. B.; Baker, N. R.; Roer, L. A.</p> <p>1996-01-01</p> <p>The wall drag test tunnel at NASA Langley Research Center was used to evaluate simulated scramjet fuel injection into a wall cavity. In this tunnel, one wall consists of interchangeable aluminum plates attached to an air bearing suspension system. The plates were equipped with load cells to measure drag forces and static taps to determine pressure distributions. The plates were exposed to a Mach 2 air stream at a total pressure of 115 psia (793 kPa). This flow field contained a train of weak unsteady, <span class="hlt">reflecting</span> <span class="hlt">shock</span> <span class="hlt">waves</span> that were produced in the nozzle assembly located upstream of the test section.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19950046290&hterms=theta+waves&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dtheta%2Bwaves','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19950046290&hterms=theta+waves&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dtheta%2Bwaves"><span id="translatedtitle">An analysis of whistler <span class="hlt">waves</span> at interplanetary <span class="hlt">shocks</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Lengyel-Frey, D.; Farrell, W. M.; Stone, R. G.; Balogh, A.; Forsyth, R.</p> <p>1994-01-01</p> <p>We present an analysis of whistler <span class="hlt">wave</span> magnetic and electric field amplitude ratios from which we compute <span class="hlt">wave</span> propagation angles and energies of electrons in resonance with the <span class="hlt">waves</span>. To do this analysis, we compute the theoretical dependence of ratios of <span class="hlt">wave</span> components on the whistler <span class="hlt">wave</span> propagation angle Theta for various combinations of orthogonal <span class="hlt">wave</span> components. Ratios of <span class="hlt">wave</span> components that would be observed by a spinning spacecraft are determined, and the effects of arbitrary inclinations of the spacecraft to the ambient magnetic field and to the whistler <span class="hlt">wave</span> vector are studied. This analysis clearly demonstrates that B/E, the ratio of magnetic to electric field amplitudes, cannot be assumed to be the <span class="hlt">wave</span> index of refraction, contrary to assumptions of some earlier studies. Therefore previous interpretations of whistler <span class="hlt">wave</span> observations based on this assumption must be reinvestigated. B/E ratios derived using three orthogonal <span class="hlt">wave</span> components can be used to unambiguously determine Theta. Using spin plane observations alone, a significant uncertainty occurs in the determination of Theta. Nevertheless, for whistler <span class="hlt">waves</span> observed downstream of several interplanetary <span class="hlt">shocks</span> by the Ulysses plasma <span class="hlt">wave</span> experiment we find that Theta is highly oblique. We suggest that the analysis of <span class="hlt">wave</span> amplitude ratios used in conjunction with traditional stability analyses provide a promising tool for determining which particle distributions and resonances are likely to be dominant contributors to <span class="hlt">wave</span> growth.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19720020644','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19720020644"><span id="translatedtitle">The interaction of moderately strong <span class="hlt">shock</span> <span class="hlt">waves</span> with thick perforated walls of low porosity</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Grant, D. J.</p> <p>1972-01-01</p> <p>A theoretical prediction is given of the flow through thick perforated walls of low porosity resulting from the impingement of a moderately strong traveling <span class="hlt">shock</span> <span class="hlt">wave</span>. The model was a flat plate positioned normal to the direction of the flow. Holes bored in the plate parallel to the direction of the flow provided nominal hole length-to-diameter ratios of 10:1 and an axial porosity of 25 percent of the flow channel cross section. The flow field behind the <span class="hlt">reflected</span> <span class="hlt">shock</span> <span class="hlt">wave</span> was assumed to behave as a reservoir producing a quasi-steady duct flow through the model. Rayleigh and Fanno duct flow theoretical computations for each of three possible auxiliary <span class="hlt">wave</span> patterns that can be associated with the transmitted <span class="hlt">shock</span> (to satisfy contact surface compatibility) were used to provide bounding solutions as an alternative to the more complex influence coefficients method. Qualitative and quantitative behavior was verified in a 1.5- by 2.0-in. helium <span class="hlt">shock</span> tube. High speed Schlieren photography, piezoelectric pressure-time histories, and electronic-counter <span class="hlt">wave</span> speed measurements were used to assess the extent of correlation with the theoretical flow models. Reduced data indicated the adequacy of the bounding theory approach to predict <span class="hlt">wave</span> phenomena and quantitative response.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19870025302&hterms=heterogeneous+mixture&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3Dheterogeneous%2Bmixture','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19870025302&hterms=heterogeneous+mixture&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3Dheterogeneous%2Bmixture"><span id="translatedtitle"><span class="hlt">Shock</span> <span class="hlt">waves</span> and <span class="hlt">shock</span> tubes; Proceedings of the Fifteenth International Symposium, Berkeley, CA, July 28-August 2, 1985</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Bershader, D. (Editor); Hanson, R. (Editor)</p> <p>1986-01-01</p> <p>A detailed survey is presented of <span class="hlt">shock</span> tube experiments, theoretical developments, and applications being carried out worldwide. The discussions explore <span class="hlt">shock</span> tube physics and the related chemical, physical and biological science and technology. Extensive attention is devoted to <span class="hlt">shock</span> <span class="hlt">wave</span> phenomena in dusty gases and other multiphase and heterogeneous systems, including chemically reactive mixtures. Consideration is given to techniques for measuring, visualizing and theoretically modeling flowfield, <span class="hlt">shock</span> <span class="hlt">wave</span> and rarefaction <span class="hlt">wave</span> characteristics. Numerical modeling is explored in terms of the application of computational fluid dynamics techniques to describing flowfields in <span class="hlt">shock</span> tubes. <span class="hlt">Shock</span> interactions and propagation, in both solids, fluids, gases and mixed media are investigated, along with the behavior of <span class="hlt">shocks</span> in condensed matter. Finally, chemical reactions that are initiated as the result of passage of a <span class="hlt">shock</span> <span class="hlt">wave</span> are discussed, together with methods of controlling the evolution of laminar separated flows at concave corners on advanced reentry vehicles.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ShWav.tmp....8G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ShWav.tmp....8G"><span id="translatedtitle"><span class="hlt">Shock</span> <span class="hlt">wave</span> emission during the collapse of cavitation bubbles</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Garen, W.; Hegedűs, F.; Kai, Y.; Koch, S.; Meyerer, B.; Neu, W.; Teubner, U.</p> <p>2016-02-01</p> <p><span class="hlt">Shock</span> <span class="hlt">wave</span> emission induced by intense laser pulses is investigated experimentally. The present work focuses on the conditions of <span class="hlt">shock</span> <span class="hlt">wave</span> emission in glycerine and distilled water during the first bubble collapse. Experimental investigations are carried out in liquids as a function of temperature and viscosity. Comparison is made with the theoretical work of Poritsky (Proc 1st US Natl Congress Appl Mech 813-821, 1952) and Brennen (Cavitation and bubble dynamics, Oxford University Press 1995). To the best knowledge of the authors, this is the first experimental verification of those theories.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/428112','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/428112"><span id="translatedtitle">Deformation of metal pipe due to underwater <span class="hlt">shock</span> <span class="hlt">wave</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Itoh, Shigeru; Kira, Akio; Fujita, Masahiro</p> <p>1996-12-31</p> <p>Deformation processes of the metal pipes accelerated by underwater <span class="hlt">shock</span> <span class="hlt">wave</span>, are investigated by both optical measurement and numerical calculation. It is confirmed that the deformation of the metal pipe obtained by the streak photograph quite agrees with that obtained by the numerical calculations. The radial velocity component of the deformation of Al pipe is faster than that of the Cu pipe. The metal pipes which are accelerated up to the maximum velocity by the underwater <span class="hlt">shock</span> <span class="hlt">wave</span>, are deforming with nearly constant velocity.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/16090745','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/16090745"><span id="translatedtitle"><span class="hlt">Shock</span> <span class="hlt">wave</span> interaction with laser-generated single bubbles.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Sankin, G N; Simmons, W N; Zhu, S L; Zhong, P</p> <p>2005-07-15</p> <p>The interaction of a lithotripter <span class="hlt">shock</span> <span class="hlt">wave</span> (LSW) with laser-generated single vapor bubbles in water is investigated using high-speed photography and pressure measurement via a fiber-optic probe hydrophone. The interaction leads to nonspherical collapse of the bubble with secondary <span class="hlt">shock</span> <span class="hlt">wave</span> emission and microjet formation along the LSW propagation direction. The maximum pressure amplification is produced during the collapse phase of the bubble oscillation when the compressive pulse duration of the LSW matches with the forced collapse time of the bubble. PMID:16090745</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005PhRvL..95c4501S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005PhRvL..95c4501S"><span id="translatedtitle"><span class="hlt">Shock</span> <span class="hlt">Wave</span> Interaction with Laser-Generated Single Bubbles</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sankin, G. N.; Simmons, W. N.; Zhu, S. L.; Zhong, P.</p> <p>2005-07-01</p> <p>The interaction of a lithotripter <span class="hlt">shock</span> <span class="hlt">wave</span> (LSW) with laser-generated single vapor bubbles in water is investigated using high-speed photography and pressure measurement via a fiber-optic probe hydrophone. The interaction leads to nonspherical collapse of the bubble with secondary <span class="hlt">shock</span> <span class="hlt">wave</span> emission and microjet formation along the LSW propagation direction. The maximum pressure amplification is produced during the collapse phase of the bubble oscillation when the compressive pulse duration of the LSW matches with the forced collapse time of the bubble.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19770003415','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19770003415"><span id="translatedtitle"><span class="hlt">Shock</span> <span class="hlt">wave</span>-turbulent boundary layer interactions in transonic flow</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Adamson, T. C., Jr.; Messiter, A. F.</p> <p>1976-01-01</p> <p>The method of matched asymptotic expansions is used in analyzing the structure of the interaction region formed when a <span class="hlt">shock</span> <span class="hlt">wave</span> impinges on a turbulent flat plate boundary layer in transonic flow. Solutions in outer regions, governed by inviscid flow equations, lead to relations for the wall pressure distribution. Solutions in the inner regions, governed by equations in which Reynolds and/or viscous stresses are included, lead to a relation for the wall shear stress. Solutions for the wall pressure distribution are reviewed for both oblique and normal incoming <span class="hlt">shock</span> <span class="hlt">waves</span>. Solutions for the wall shear stress are discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19850026602','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19850026602"><span id="translatedtitle">Nuclear reactions in <span class="hlt">shock</span> <span class="hlt">wave</span> front during supernova events</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Lavrukhina, A. K.</p> <p>1985-01-01</p> <p>The new unique isotopic anomalous coponent of Xe(XeX) was found in the carbonaceous chondrites. It is enriched in light shielded isotopes (124Xe and 126Xe) and in heavy nonshielded isotopes (134Xe and 136Xe. All characteristics of Xe-X can be explained by a model of nucleosynthesis of the Xe isotopes in <span class="hlt">shock</span> <span class="hlt">wave</span> front passed through the He envelope during supernova events. The light isotopes are created by p process and the heavy isotopes are created by n process (slow r process). They were captured with high temperature carbon grains condensing by supernova <span class="hlt">shock</span> <span class="hlt">waves</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015shw2.conf.1077B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015shw2.conf.1077B"><span id="translatedtitle">Generation of Cylindrical Converging <span class="hlt">Shock</span> <span class="hlt">Waves</span> in a Conventional <span class="hlt">Shock</span> Tube</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Biamino, L.; Jourdan, G.; Mariani, C.; Houas, L.; Vandenboomgaerde, M.; Souffland, D.</p> <p></p> <p>For ever two decades, the IUSTI laboratory has been known for its investigations [1] dealing with the Richtmyer-Meshkov instability (RMI). Experiments concerning the RMI have been performed in conventional <span class="hlt">shock</span> tubes [2, 3, 4, 5]. All these experiments use a planar <span class="hlt">shock</span> <span class="hlt">wave</span> to generate the instability as perfectly as possible. However, the RMI also occurs in the spherical case where the convergence effects must be taken into account. As far as we know, no conventional (straight section) <span class="hlt">shock</span> tube facility has been used to experimentally study the RMI in a spherical geometry.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015APS..DFDR12003R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015APS..DFDR12003R"><span id="translatedtitle">Plane <span class="hlt">shock</span> <span class="hlt">waves</span> and Haff's law in a granular gas</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Reddy, Lakshminarayana; Alam, Meheboob</p> <p>2015-11-01</p> <p>The Riemann problem of planar <span class="hlt">shock</span> <span class="hlt">waves</span> is analyzed for a dilute granular gas by solving Euler- and Navier-Stokes-order equations numerically. The density and temperature profiles are found to be asymmetric, with the maxima of both density and temperature occurring within the <span class="hlt">shock</span>-layer. The density-peak increases with increasing Mach number and inelasticity, and is found to propagate at a steady speed at late times. The granular temperature at the upstream end of the <span class="hlt">shock</span> decay according to Haff's law [ θ (t) ~t-2 ], but the downstream temperature decays faster than its upstream counterpart. The Haff's law seems to hold inside the <span class="hlt">shock</span> up-to a certain time for weak <span class="hlt">shocks</span>, but deviations occur for strong <span class="hlt">shocks</span>. The time at which the maximum temperature deviates from Haff's law follows a power-law scaling with upstream Mach number and the restitution coefficient. The continual build-up of density inside the <span class="hlt">shock</span> is discussed, the origin of which seems to be tied to a pressure instability in granular gases. It is shown that the granular energy equation must be `regularized' to arrest the maximum density, and the regularized hydrodynamic equations should be used for <span class="hlt">shock</span> calculations (Reddy & Alam, 2015, J. Fluid Mech., to be published).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19980228372','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19980228372"><span id="translatedtitle">Structure of Weak <span class="hlt">Shock</span> <span class="hlt">Waves</span> in a Monatomic Gas</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Sherman, F. S.; Talbot, L.</p> <p>1959-01-01</p> <p>The profiles and thicknesses of normal <span class="hlt">shock</span> <span class="hlt">waves</span> in argon at Mach numbers of 1.335, 1.454, 1.576, and 1-713 were determined experimentally by means of a free-molecule probe whose equilibrium temperature is related by kinetic theory to the local flow properties and their gradients. Comparisons were made between the experimental <span class="hlt">shock</span> profiles and the theoretical profiles calculated from the Navier-Stokes equations, the Grad 13-moment equations, and the Burnett equations. New, very accurate numerical integrations of the Burnett equations were obtained for this purpose with results quite different from those found by Zoller, to whom the solution of this problem is frequently attributed. The experimental <span class="hlt">shock</span> profiles were predicted with approximately equal success by the Navier-Stokes and Burnett theories, while the 13-moment method was definitely less satisfactory. A surprising feature of the theoretical results is the relatively small difference in predictions between the Navier-Stokes and Burnett theories in the present range of <span class="hlt">shock</span> strengths and the contrastingly large difference between predictions of Burnett and the 13-moment theories. It is concluded that the Navier-Stokes equations are correct for weak <span class="hlt">shocks</span> and that within the present <span class="hlt">shock</span> strength range the Burnett equations make no improvement which merits the trouble of solving them. For <span class="hlt">shocks</span> of noticeably greater strength, say with a <span class="hlt">shock</span> Mach number of more than 2.5, it remains fundamentally doubtful that any of these theories can be correct.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19720054774&hterms=SOLITONS&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3DSOLITONS','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19720054774&hterms=SOLITONS&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3DSOLITONS"><span id="translatedtitle">Structure of ion acoustic solitons and <span class="hlt">shock</span> <span class="hlt">waves</span> in a two-component plasma.</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>White, R. B.; Fried, B. D.; Coroniti, F. V.</p> <p>1972-01-01</p> <p>Time-independent solitary <span class="hlt">waves</span> and <span class="hlt">shocks</span> are investigated in a two-component plasma using a fluid model and kinetic theory. It is found that very small concentrations of a light ion can drastically alter the structure, changing the potential maximum by an order of magnitude. For a fixed Mach number, a critical density ratio of light to heavy ions is found at which the potential maximum changes discontinuously from a value large enough to <span class="hlt">reflect</span> the light ions to one which allows them to traverse the <span class="hlt">shock</span> front and enter the downstream flow. The downstream oscillatory structure normally seen in a <span class="hlt">shock</span> is completely quenched by dissipation due to light ion <span class="hlt">reflection</span> at concentrations of 3-8% He in an Ar plasma for typical electron to ion temperature ratios and Mach number values.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19960021262&hterms=ENERGY+SOLAR&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3DENERGY%2BSOLAR','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19960021262&hterms=ENERGY+SOLAR&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3DENERGY%2BSOLAR"><span id="translatedtitle">Electron acceleration to high energies at quasi-parallel <span class="hlt">shock</span> <span class="hlt">waves</span> in the solar corona</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Mann, G.; Classen, H.-T.</p> <p>1995-01-01</p> <p>In the solar corona <span class="hlt">shock</span> <span class="hlt">waves</span> are generated by flares and/or coronal mass ejections. They manifest themselves in solar type 2 radio bursts appearing as emission stripes with a slow drift from high to low frequencies in dynamic radio spectra. Their nonthermal radio emission indicates that electrons are accelerated to suprathermal and/or relativistic velocities at these <span class="hlt">shocks</span>. As well known by extraterrestrial in-situ measurements supercritical, quasi-parallel, collisionless <span class="hlt">shocks</span> are accompanied by so-called SLAMS (short large amplitude magnetic field structures). These SLAMS can act as strong magnetic mirrors, at which charged particles can be <span class="hlt">reflected</span> and accelerated. Thus, thermal electrons gain energy due to multiple <span class="hlt">reflections</span> between two SLAMS and reach suprathermal and relativistic velocities. This mechanism of accelerating electrons is discussed for circumstances in the solar corona and may be responsible for the so-called 'herringbones' observed in solar type 2 radio bursts.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010MNRAS.407.1157Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010MNRAS.407.1157Z"><span id="translatedtitle">Evolution of the Chandra CCD spectra of SNR 1987A: probing the <span class="hlt">reflected-shock</span> picture</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhekov, Svetozar A.; Park, Sangwook; McCray, Richard; Racusin, Judith L.; Burrows, David N.</p> <p>2010-09-01</p> <p>We continue to explore the validity of the <span class="hlt">reflected-shock</span> structure (RSS) picture in SNR 1987A that was proposed in our previous analyses of the X-ray emission from this object. We used an improved version of our RSS model in a global analysis of 14 CCD spectra from the monitoring program with Chandra. In the framework of the RSS picture, we are able to match both the expansion velocity curve deduced from the analysis of the X-ray images and light curve. Using a simplified analysis, we also show that the X-rays and the non-thermal radio emission may originate from the same <span class="hlt">shock</span> structure (the blast <span class="hlt">wave</span>). We believe that using the RSS model in the analysis of grating data from the Chandra monitoring program of SNR 1987A that cover a long enough time interval will allow us to build a more realistic physical picture and model of SNR 1987A.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_20 --> <div id="page_21" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="401"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/20875777','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/20875777"><span id="translatedtitle">Evolution of <span class="hlt">Shock</span> <span class="hlt">Waves</span> in Silicon Carbide Rods</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Balagansky, I. A.; Balagansky, A. I.; Razorenov, S. V.; Utkin, A. V.</p> <p>2006-07-28</p> <p>Evolution of <span class="hlt">shock</span> <span class="hlt">waves</span> in self-bonded silicon carbide bars in the shape of 20 mm x 20 mm square prisms of varying lengths (20 mm, 40 mm, and 77.5 mm) is investigated. The density and porosity of the test specimens were 3.08 g/cm3 and 2%, respectively. <span class="hlt">Shock</span> <span class="hlt">waves</span> were generated by detonating a cylindrical shaped (d=40 mm and 1=40 mm) stabilized RDX high explosive charge of density 1.60 g/cm3. Embedded manganin gauges at various distances from the impact face were used to monitor the amplitude of <span class="hlt">shock</span> pressure profiles. Propagation velocity of the stress pulse was observed to be equal to the elastic bar <span class="hlt">wave</span> velocity of 11 km/s and was independent of the amplitude of the impact pulse. Strong fuzziness of the stress <span class="hlt">wave</span> front is observed. This observation conforms to the theory on the instability of the <span class="hlt">shock</span> formation in a finite size elastic body. This phenomenon of <span class="hlt">wave</span> front fuzziness may be useful for desensitization of heterogeneous high explosives.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19840008422','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19840008422"><span id="translatedtitle"><span class="hlt">Shock</span> conditions and <span class="hlt">shock</span> <span class="hlt">wave</span> structures in a steady flow in a dissipative fluid</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Germain, P.; Guiraud, J. P.</p> <p>1983-01-01</p> <p>More precisely, calling xi the reciprocal of the Reynolds number based on the <span class="hlt">shock</span> <span class="hlt">wave</span> curvature radius, the xi terms of the first order are systematically taken into account. The most important result is a system of formulas giving a correction of order xi for the various RANKINE-HUGONIOT conditions. The suggested formulas may for instance have to be used instead of the conventional ones to evaluate the loss of the total pressure across the detached <span class="hlt">shock</span> <span class="hlt">wave</span> which is found at the nose of a very small probe in supersonic flow.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2014JPhCS.500r2026L&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2014JPhCS.500r2026L&link_type=ABSTRACT"><span id="translatedtitle">The bactericidal effect of <span class="hlt">shock</span> <span class="hlt">waves</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Leighs, J. A.; Appleby-Thomas, G. J.; Wood, D. C.; Goff, M. J.; Hameed, A.; Hazell, P. J.</p> <p>2014-05-01</p> <p>There are a variety of theories relating to the origins of life on our home planet, some of which discuss the possibility that life may have been spread via inter-planetary bodies. There have been a number of investigations into the ability of life to withstand the likely conditions generated by asteroid impact (both contained in the impactor and buried beneath the planet surface). Previously published data regarding the ability of bacteria to survive such applied shockwaves has produced conflicting conclusions. The work presented here used an established and published technique in combination with a single stage gas gun, to <span class="hlt">shock</span> and subsequently recover Escherichia coli populations suspended in a phosphate buffered saline solution. Peak pressure across the sample region was calculated via numerical modelling. Survival data against peak sample pressure for recovered samples is presented alongside control tests. SEM micrographs of <span class="hlt">shocked</span> samples are presented alongside control sets to highlight key differences between cells in each case.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22252089','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22252089"><span id="translatedtitle">Solitary and <span class="hlt">shock</span> <span class="hlt">waves</span> in magnetized electron-positron plasma</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Lu, Ding; Li, Zi-Liang; Abdukerim, Nuriman; Xie, Bai-Song</p> <p>2014-02-15</p> <p>An Ohm's law for electron-positron (EP) plasma is obtained. In the framework of EP magnetohydrodynamics, we investigate nonrelativistic nonlinear <span class="hlt">waves</span>' solutions in a magnetized EP plasma. In the collisionless limit, quasistationary propagating solitary <span class="hlt">wave</span> structures for the magnetic field and the plasma density are obtained. It is found that the <span class="hlt">wave</span> amplitude increases with the Mach number and the Alfvén speed. However, the dependence on the plasma temperature is just the opposite. Moreover, for a cold EP plasma, the existence range of the solitary <span class="hlt">waves</span> depends only on the Alfvén speed. For a hot EP plasma, the existence range depends on the Alfvén speed as well as the plasma temperature. In the presence of collision, the electromagnetic fields and the plasma density can appear as oscillatory <span class="hlt">shock</span> structures because of the dissipation caused by the collisions. As the collision frequency increases, the oscillatory <span class="hlt">shock</span> structure becomes more and more monotonic.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015PhFl...27f6101V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015PhFl...27f6101V"><span id="translatedtitle">Dynamics of cylindrical converging <span class="hlt">shock</span> <span class="hlt">waves</span> interacting with aerodynamic obstacle arrays</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Vignati, F.; Guardone, A.</p> <p>2015-06-01</p> <p>Cylindrical converging <span class="hlt">shock</span> <span class="hlt">waves</span> interacting with an array of aerodynamic obstacles are investigated numerically for diverse <span class="hlt">shock</span> strengths and for different obstacle configurations in air in standard conditions. The considered number of obstacles N is 4, 6, 8, 16, and 24. Obstacles are lenticular airfoils with thickness-to-chord ratios t/c of 0.07, 0.14, and 0.21. The distances of the airfoil leading edge from the <span class="hlt">shock</span> focus point r LE/rLE ref are 1, 2, and 2.5, where rLE ref = 7 is the dimensionless reference distance from the origin. Considered impinging <span class="hlt">shock</span> Mach numbers Ms are 2.2, 2.7, and 3.2 at the reference distance from the origin. The reference experimental configuration ( N = 8 , t/c = 0 . 14 , r LE = 7 , M s = 2 . 7 ) was proposed by Kjellander et al. ["Thermal radiation from a converging <span class="hlt">shock</span> implosion," Phys. Fluids 22, 046102 (2010)]. Numerical results compare fairly well to available one-dimensional models for <span class="hlt">shock</span> propagation and to available experimental results in the reference configuration. Local <span class="hlt">reflection</span> types are in good agreement with the classical criteria for planar <span class="hlt">shock</span> <span class="hlt">waves</span>. The main <span class="hlt">shock</span> reshaping patterns are identified and their dependence on the <span class="hlt">shock</span> strength and obstacle configuration is exposed. In particular, different <span class="hlt">shock</span> patterns are observed after the leading edge <span class="hlt">reflection</span>, which results in polygonal <span class="hlt">shock</span> <span class="hlt">wave</span> with N, 2N, 3N, and 4N sides. The largest temperature peak at the origin is obtained for the 8- and the 16-obstacle configurations and for the smallest thickness to length ratio, 0.07, located at distance from the origin of 2 rLE ref . In terms of compression efficiency at the origin, the 16-obstacle configuration is found to perform slightly better than the reference 8-obstacle configuration—with an efficiency increase of about 2%-3%, which is well within the model accuracy—thus confirming the goodness of the obstacle arrangement proposed by Kjellander and collaborators.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22403239','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22403239"><span id="translatedtitle">Dynamics of cylindrical converging <span class="hlt">shock</span> <span class="hlt">waves</span> interacting with aerodynamic obstacle arrays</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Vignati, F.; Guardone, A.</p> <p>2015-06-15</p> <p>Cylindrical converging <span class="hlt">shock</span> <span class="hlt">waves</span> interacting with an array of aerodynamic obstacles are investigated numerically for diverse <span class="hlt">shock</span> strengths and for different obstacle configurations in air in standard conditions. The considered number of obstacles N is 4, 6, 8, 16, and 24. Obstacles are lenticular airfoils with thickness-to-chord ratios t/c of 0.07, 0.14, and 0.21. The distances of the airfoil leading edge from the <span class="hlt">shock</span> focus point (r{sub LE})/(r{sub LE}{sup ref}) are 1, 2, and 2.5, where r{sub LE}{sup ref}=7 is the dimensionless reference distance from the origin. Considered impinging <span class="hlt">shock</span> Mach numbers M{sub s} are 2.2, 2.7, and 3.2 at the reference distance from the origin. The reference experimental configuration (N=8,t/c =0.14,r{sub LE}=7,M{sub s}=2.7) was proposed by Kjellander et al. [“Thermal radiation from a converging <span class="hlt">shock</span> implosion,” Phys. Fluids 22, 046102 (2010)]. Numerical results compare fairly well to available one-dimensional models for <span class="hlt">shock</span> propagation and to available experimental results in the reference configuration. Local <span class="hlt">reflection</span> types are in good agreement with the classical criteria for planar <span class="hlt">shock</span> <span class="hlt">waves</span>. The main <span class="hlt">shock</span> reshaping patterns are identified and their dependence on the <span class="hlt">shock</span> strength and obstacle configuration is exposed. In particular, different <span class="hlt">shock</span> patterns are observed after the leading edge <span class="hlt">reflection</span>, which results in polygonal <span class="hlt">shock</span> <span class="hlt">wave</span> with N, 2N, 3N, and 4N sides. The largest temperature peak at the origin is obtained for the 8- and the 16-obstacle configurations and for the smallest thickness to length ratio, 0.07, located at distance from the origin of 2r{sub LE}{sup ref}. In terms of compression efficiency at the origin, the 16-obstacle configuration is found to perform slightly better than the reference 8-obstacle configuration—with an efficiency increase of about 2%-3%, which is well within the model accuracy—thus confirming the goodness of the obstacle arrangement proposed by Kjellander and</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/18807077','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/18807077"><span id="translatedtitle">Kidney damage in extracorporeal <span class="hlt">shock</span> <span class="hlt">wave</span> lithotripsy: a numerical approach for different <span class="hlt">shock</span> profiles.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Weinberg, Kerstin; Ortiz, Michael</p> <p>2009-08-01</p> <p>In <span class="hlt">shock-wave</span> lithotripsy--a medical procedure to fragment kidney stones--the patient is subjected to hypersonic <span class="hlt">waves</span> focused at the kidney stone. Although this procedure is widely applied, the physics behind this medical treatment, in particular the question of how the injuries to the surrounding kidney tissue arise, is still under investigation. To contribute to the solution of this problem, two- and three-dimensional numerical simulations of a human kidney under <span class="hlt">shock-wave</span> loading are presented. For this purpose a constitutive model of the bio-mechanical system kidney is introduced, which is able to map large visco-elastic deformations and, in particular, material damage. The specific phenomena of cavitation induced oscillating bubbles is modeled here as an evolution of spherical pores within the soft kidney tissue. By means of large scale finite element simulations, we study the <span class="hlt">shock-wave</span> propagation into the kidney tissue, adapt unknown material parameters and analyze the resulting stress states. The simulations predict localized damage in the human kidney in the same regions as observed in animal experiments. Furthermore, the numerical results suggest that in first instance the pressure amplitude of the <span class="hlt">shock</span> <span class="hlt">wave</span> impulse (and not so much its exact time-pressure profile) is responsible for damaging the kidney tissue. PMID:18807077</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1997APS..DPPgTP215B&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1997APS..DPPgTP215B&link_type=ABSTRACT"><span id="translatedtitle">Possible Implications of Anomalous <span class="hlt">Shock</span> <span class="hlt">Wave</span> Behavior for Laser Fusion</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bates, Jason W.; Montgomery, David C.</p> <p>1997-11-01</p> <p>In ``normal'' materials, <span class="hlt">shocks</span> are compressive because of the inequality (partial^2p / partial V^2)_s> 0, which is, however, not dictated by thermodynamics.(e.g.), Ya. B. Zel'dovich and Yu. P. Raizer, ``Physics of <span class="hlt">Shock</span> <span class="hlt">Waves</span> and High-Temperature Hydrodynamic Phenomena,'' (N.Y., Academic Press, 1967), Vol I, pp. 67-69; Vol II, pp. 750-762. In ``anomalous'' materials, the inequality may go the other way, and exotic phenomena result: rarefactive <span class="hlt">shocks</span>, spreading compressive pulses, and <span class="hlt">shock</span> <span class="hlt">wave</span> ``splitting'' or instability.^2,(N. M. Kuznetsov, Sov. Phys. JETP 61), 275 (1985). Materials tend to behave ``anomalously'' in the vicinities of phase transitions. <span class="hlt">Shock</span>-imploded DT fusion fuels will experience a variety of phase transitions, including melting, vaporization, molecular dissociation, and ionization. Imperfectly explored gas-dynamic problems may require attention to each case. For example, in the <span class="hlt">shock</span> Hugoniot measurements of Da Silva et al. [Phys. Rev. Lett. 78, 483 (1997)], the high-pressure part of Fig. 4b suggests the possibility of ``anomalous'' behavior.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ShWav..26...69H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ShWav..26...69H"><span id="translatedtitle">Response of ocean bottom dwellers exposed to underwater <span class="hlt">shock</span> <span class="hlt">waves</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hosseini, S. H. R.; Kaiho, Kunio; Takayama, Kazuyoshi</p> <p>2016-01-01</p> <p>The paper reports results of experiments to estimate the mortality of ocean bottom dwellers, ostracoda, against underwater <span class="hlt">shock</span> <span class="hlt">wave</span> exposures. This study is motivated to verify the possible survival of ocean bottom dwellers, foraminifera, from the devastating underwater <span class="hlt">shock</span> <span class="hlt">waves</span> induced mass extinction of marine creatures which took place at giant asteroid impact events. Ocean bottom dwellers under study were ostracoda, the replacement of foraminifera, we readily sampled from ocean bottoms. An analogue experiment was performed on a laboratory scale to estimate the domain and boundary of over-pressures at which marine creatures' mortality occurs. Ostracods were exposed to underwater <span class="hlt">shock</span> <span class="hlt">waves</span> generated by the explosion of 100mg PETN pellets in a chamber at <span class="hlt">shock</span> over-pressures ranging up to 44MPa. Pressure histories were measured simultaneously on 113 samples. We found that bottom dwellers were distinctively killed against overpressures of 12MPa and this value is much higher than the usual <span class="hlt">shock</span> over-pressure threshold value for marine-creatures having lungs and balloons.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016EGUGA..1810637M&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016EGUGA..1810637M&link_type=ABSTRACT"><span id="translatedtitle">Stochastic electron acceleration during turbulent reconnection in strong <span class="hlt">shock</span> <span class="hlt">waves</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Matsumoto, Yosuke</p> <p>2016-04-01</p> <p>Acceleration of charged particles is a fundamental topic in astrophysical, space and laboratory plasmas. Very high energy particles are commonly found in the astrophysical and planetary <span class="hlt">shocks</span>, and in the energy releases of solar flares and terrestrial substorms. Evidence for relativistic particle production during such phenomena has attracted much attention concerning collisionless <span class="hlt">shock</span> <span class="hlt">waves</span> and magnetic reconnection, respectively, as ultimate plasma energization mechanisms. While the energy conversion proceeds macroscopically, and therefore the energy mostly flows to ions, plasma kinetic instabilities excited in a localized region have been considered to be the main electron heating and acceleration mechanisms. We present that efficient electron energization can occur in a much larger area during turbulent magnetic reconnection from the intrinsic nature of a strong collisionless <span class="hlt">shock</span> <span class="hlt">wave</span>. Supercomputer simulations have revealed a multiscale <span class="hlt">shock</span> structure comprising current sheets created via an ion-scale Weibel instability and resulting energy dissipation through magnetic reconnection. A part of the upstream electrons undergoes first-order Fermi acceleration by colliding with reconnection jets and magnetic islands, giving rise to a nonthermal relativistic population downstream. The dynamics has shed new light on magnetic reconnection as an agent of energy dissipation and particle acceleration in strong <span class="hlt">shock</span> <span class="hlt">waves</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/15014330','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/15014330"><span id="translatedtitle">SIMULATION OF <span class="hlt">SHOCK</span> <span class="hlt">WAVE</span> PROPAGATION AND DAMAGE IN GEOLOGIC MATERIALS</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Lomov, I; Vorobiev, O; Antoun, T H</p> <p>2004-09-17</p> <p>A new thermodynamically consistent material model for large deformation has been developed. It describes quasistatic loading of limestone as well as high-rate phenomena. This constitutive model has been implemented into an Eulerian <span class="hlt">shock</span> <span class="hlt">wave</span> code with adaptive mesh refinement. This approach was successfully used to reproduce static triaxial compression tests and to simulate experiments of blast loading and damage of limestone. Results compare favorably with experimentally available <span class="hlt">wave</span> profiles from spherically-symmetric explosion in rock samples.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26442143','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26442143"><span id="translatedtitle">Bubbles with <span class="hlt">shock</span> <span class="hlt">waves</span> and ultrasound: a review.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ohl, Siew-Wan; Klaseboer, Evert; Khoo, Boo Cheong</p> <p>2015-10-01</p> <p>The study of the interaction of bubbles with <span class="hlt">shock</span> <span class="hlt">waves</span> and ultrasound is sometimes termed 'acoustic cavitation'. It is of importance in many biomedical applications where sound <span class="hlt">waves</span> are applied. The use of <span class="hlt">shock</span> <span class="hlt">waves</span> and ultrasound in medical treatments is appealing because of their non-invasiveness. In this review, we present a variety of acoustics-bubble interactions, with a focus on <span class="hlt">shock</span> <span class="hlt">wave</span>-bubble interaction and bubble cloud phenomena. The dynamics of a single spherically oscillating bubble is rather well understood. However, when there is a nearby surface, the bubble often collapses non-spherically with a high-speed jet. The direction of the jet depends on the 'resistance' of the boundary: the bubble jets towards a rigid boundary, splits up near an elastic boundary, and jets away from a free surface. The presence of a <span class="hlt">shock</span> <span class="hlt">wave</span> complicates the bubble dynamics further. We shall discuss both experimental studies using high-speed photography and numerical simulations involving <span class="hlt">shock</span> <span class="hlt">wave</span>-bubble interaction. In biomedical applications, instead of a single bubble, often clouds of bubbles appear (consisting of many individual bubbles). The dynamics of such a bubble cloud is even more complex. We shall show some of the phenomena observed in a high-intensity focused ultrasound (HIFU) field. The nonlinear nature of the sound field and the complex inter-bubble interaction in a cloud present challenges to a comprehensive understanding of the physics of the bubble cloud in HIFU. We conclude the article with some comments on the challenges ahead. PMID:26442143</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005ASAJ..117.2372C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005ASAJ..117.2372C"><span id="translatedtitle">Secondary <span class="hlt">shock</span> <span class="hlt">wave</span> emissions from cavitation in lithotripsy</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chitnis, Parag V.; Cleveland, Robin O.</p> <p>2005-04-01</p> <p>We investigate the role of secondary <span class="hlt">shock</span> <span class="hlt">waves</span> (SSWs) generated by cavitation in lithotripsy. Acoustic pressure was measured with a fiber optic probe hydrophone and cavitation using a dual passive cavitation detector (PCD) consisting of two confocal transducers. An artificial stone (~7 mm diameter and ~9 mm length) was placed at the focus of an electrohydraulic lithotripter. The fiber was inserted through a hole drilled through the stone so that the tip was at the proximal surface. SSWs were identified by matching the time of arrival to that of the inertial collapse signature acquired by the PCD. Measurements of SSWs were obtained for 50% of SWs fired at 20 kV and 1 Hz. The peak positive pressure for the SSW was p+=33.7+/-14.8 MPa, which was comparable to the pressure induced by the incident SW (p+=42.6+/-6 MPa). The peak pressure in water was p+=23.2+/-4.4 MPa. The PCD also recorded acoustic emissions from forced collapse of pre-existing bubbles caused by the incident SW. We propose that both the <span class="hlt">reflection</span> from the semi-rigid stone boundary and SSW from the forced collapse contribute to the observed increase in the peak pressure of the incident SW in presence of a stone. [Work supported by NIH.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EPJD...69..259S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EPJD...69..259S"><span id="translatedtitle">Measuring high pressure equation of state of polystyrene using laser driven <span class="hlt">shock</span> <span class="hlt">wave</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Shu, Hua; Huang, Xiuguang; Ye, Junjian; Wu, Jiang; Jia, Guo; Fang, Zhiheng; Xie, Zhiyong; Zhou, Huazhen; Fu, Sizu</p> <p>2015-11-01</p> <p>High precision polystyrene equation of state data were measured using laser-driven <span class="hlt">shock</span> <span class="hlt">waves</span> with pressures from 180 GPa to 700 GPa. α quartz was used as standard material, the <span class="hlt">shock</span> <span class="hlt">wave</span> trajectory in quartz and polystyrene was measured using the Velocity Interferometer for Any Reflector (VISAR). Instantaneous <span class="hlt">shock</span> velocity in quartz and polystyrene was obtained when the <span class="hlt">shock</span> <span class="hlt">wave</span> pass the interface. This provided ~1% precision in <span class="hlt">shock</span> velocity measurements.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/21918295','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/21918295"><span id="translatedtitle"><span class="hlt">Shock</span> <span class="hlt">wave</span>-bubble interaction near soft and rigid boundaries during lithotripsy: numerical analysis by the improved ghost fluid method.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Kobayashi, Kazumichi; Kodama, Tetsuya; Takahira, Hiroyuki</p> <p>2011-10-01</p> <p>In the case of extracorporeal <span class="hlt">shock</span> <span class="hlt">wave</span> lithotripsy (ESWL), a <span class="hlt">shock</span> <span class="hlt">wave</span>-bubble interaction inevitably occurs near the focusing point of stones, resulting in stone fragmentation and subsequent tissue damage. Because <span class="hlt">shock</span> <span class="hlt">wave</span>-bubble interactions are high-speed phenomena occurring in tissue consisting of various media with different acoustic impedance values, numerical analysis is an effective method for elucidating the mechanism of these interactions. However, the mechanism has not been examined in detail because, at present, numerical simulations capable of incorporating the acoustic impedance of various tissues do not exist. Here, we show that the improved ghost fluid method (IGFM) can treat <span class="hlt">shock</span> <span class="hlt">wave</span>-bubble interactions in various media. Nonspherical bubble collapse near a rigid or soft tissue boundary (stone, liver, gelatin and fat) was analyzed. The <span class="hlt">reflection</span> <span class="hlt">wave</span> of an incident <span class="hlt">shock</span> <span class="hlt">wave</span> at a tissue boundary was the primary cause for the acceleration or deceleration of bubble collapse. The impulse that was obtained from the temporal evolution of pressure created by the bubble collapse increased the downward velocity of the boundary and caused subsequent boundary deformation. Results of this study showed that the IGFM is a useful method for analyzing the <span class="hlt">shock</span> <span class="hlt">wave</span>-bubble interaction near various tissues with different acoustic impedance. PMID:21918295</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22408340','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22408340"><span id="translatedtitle"><span class="hlt">Shock</span> <span class="hlt">wave</span> acceleration of protons in inhomogeneous plasma interacting with ultrashort intense laser pulses</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Lecz, Zs.; Andreev, A.</p> <p>2015-04-15</p> <p>The acceleration of protons, triggered by solitary <span class="hlt">waves</span> in expanded solid targets is investigated using particle-in-cell simulations. The near-critical density plasma is irradiated by ultrashort high power laser pulses, which generate the solitary <span class="hlt">wave</span>. The transformation of this soliton into a <span class="hlt">shock</span> <span class="hlt">wave</span> during propagation in plasma with exponentially decreasing density profile is described analytically, which allows to obtain a scaling law for the proton energy. The high quality proton bunch with small energy spread is produced by <span class="hlt">reflection</span> from the <span class="hlt">shock</span>-front. According to the 2D simulations, the mechanism is stable only if the laser pulse duration is shorter than the characteristic development time of the parasitic Weibel instability.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007APS..SHK.G4005H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007APS..SHK.G4005H"><span id="translatedtitle">Solitary and <span class="hlt">shock</span> <span class="hlt">waves</span> in discrete double power law materials</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Herbold, Eric; Nesterenko, Vitali</p> <p>2007-06-01</p> <p>A novel strongly nonlinear metamaterial is composed using a periodic arrangement of toroidal rings between plates. The toroids are considered massless strongly nonlinear springs where the force versus displacement relationship is described by two additive power-law relationships. In these systems the nonlinearity is due to the dramatic change of the contact plane, which starts as an arbitrarily thin circle then increases in thickness with increasing compression. Solitary and <span class="hlt">shock</span> <span class="hlt">waves</span> are examined numerically and experimentally using three different types of polymer or rubber o-rings allowing mitigation of higher amplitude <span class="hlt">shock</span> impulses in comparison with granular systems. In these systems a train of pulses can consist of two separate groups related to two strongly nonlinear regimes with different values of exponents, depending on the amplitude. In experiments two types of <span class="hlt">shock</span> <span class="hlt">waves</span> (monotonic or oscillatory) were observed depending on the type of o-rings.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22130476','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22130476"><span id="translatedtitle"><span class="hlt">Shock</span> <span class="hlt">wave</span> refraction enhancing conditions on an extended interface</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Markhotok, A.; Popovic, S.</p> <p>2013-04-15</p> <p>We determined the law of <span class="hlt">shock</span> <span class="hlt">wave</span> refraction for a class of extended interfaces with continuously variable gradients. When the interface is extended or when the gas parameters vary fast enough, the interface cannot be considered as sharp or smooth and the existing calculation methods cannot be applied. The expressions we derived are general enough to cover all three types of the interface and are valid for any law of continuously varying parameters. We apply the equations to the case of exponentially increasing temperature on the boundary and compare the results for all three types of interfaces. We have demonstrated that the type of interface can increase or inhibit the <span class="hlt">shock</span> <span class="hlt">wave</span> refraction. Our findings can be helpful in understanding the results obtained in energy deposition experiments as well as for controlling the <span class="hlt">shock</span>-plasma interaction in other settings.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/21272745','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/21272745"><span id="translatedtitle"><span class="hlt">Shock</span> <span class="hlt">wave</span> in a two-dimensional dusty plasma crystal</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Ghosh, Samiran</p> <p>2009-10-15</p> <p>Two-dimensional (2D) <span class="hlt">shock</span> structures of longitudinal dust lattice <span class="hlt">wave</span> (LDLW) in a hexagonal Yukawa crystal are studied. The nonlinear evolution equation derived for dusty plasma crystal is found to be a 2D Burgers' equation, where the Burgers' term, i.e., the dissipation is provided by ''hydrodynamic damping'' due to irreversible processes that take place within the system. Analytical and numerical solutions of this equation on the basis of crystal experimental parameters show the development of compressional <span class="hlt">shock</span> structures of LDLW in 2D dusty plasma crystal. The <span class="hlt">shock</span> strength decreases (increases) with the increase in lattice parameter {kappa} (angle of propagation of the nonlinear <span class="hlt">wave</span>). The results are discussed in the context of 2D monolayer hexagonal dusty plasma crystal experiments.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19910067030&hterms=ERI&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3DERI','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19910067030&hterms=ERI&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3DERI"><span id="translatedtitle">The optical emission from oscillating white dwarf radiative <span class="hlt">shock</span> <span class="hlt">waves</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Imamura, James N.; Rashed, Hussain; Wolff, Michael T.</p> <p>1991-01-01</p> <p>The hypothesis that quasi-periodic oscillations (QPOs) are due to the oscillatory instability of radiative <span class="hlt">shock</span> <span class="hlt">waves</span> discovered by Langer et al. (1981, 1092) is examined. The time-dependent optical spectra of oscillating radiative <span class="hlt">shocks</span> produced by flows onto magnetic white dwarfs are calculated. The results are compared with the observations of the AM Her QPO sources V834 Cen, AN UMa, EF Eri, and VV Pup. It is found that the <span class="hlt">shock</span> oscillation model has difficulties with aspects of the observations for each of the sources. For VV Pup, AN UMa, and V834 Cen, the cyclotron luminosities for the observed magnetic fields of these systems, based on our calculations, are large. The strong cyclotron emission probably stabilizes the <span class="hlt">shock</span> oscillations. For EF Eri, the mass of the white dwarf based on hard X-ray observations is greater than 0.6 solar mass.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_21 --> <div id="page_22" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active"><span>22</span></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="421"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19920045571&hterms=Irregular+Structure&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3DIrregular%2BStructure','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19920045571&hterms=Irregular+Structure&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3DIrregular%2BStructure"><span id="translatedtitle">Internal structure of <span class="hlt">shock</span> <span class="hlt">waves</span> in disparate mass mixtures</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Chung, Chan-Hong; De Witt, Kenneth J.; Jeng, Duen-Ren; Penko, Paul F.</p> <p>1992-01-01</p> <p>The detailed flow structure of a normal <span class="hlt">shock</span> <span class="hlt">wave</span> for a gas mixture is investigated using the direct-simulation Monte Carlo method. A variable diameter hard-sphere (VDHS) model is employed to investigate the effect of different viscosity temperature exponents (VTE) for each species in a gas mixture. Special attention is paid to the irregular behavior in the density profiles which was previously observed in a helium-xenon experiment. It is shown that the VTE can have substantial effects in the prediction of the structure of <span class="hlt">shock</span> <span class="hlt">waves</span>. The variable hard-sphere model of Bird shows good agreement, but with some limitations, with the experimental data if a common VTE is chosen properly for each case. The VDHS model shows better agreement with the experimental data without adjusting the VTE. The irregular behavior of the light-gas component in <span class="hlt">shock</span> <span class="hlt">waves</span> of disparate mass mixtures is observed not only in the density profile, but also in the parallel temperature profile. The strength of the <span class="hlt">shock</span> <span class="hlt">wave</span>, the type of molecular interactions, and the mole fraction of heavy species have substantial effects on the existence and structure of the irregularities.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20040046928','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20040046928"><span id="translatedtitle">Survey of Temperature Measurement Techniques For Studying Underwater <span class="hlt">Shock</span> <span class="hlt">Waves</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Danehy, Paul M.; Alderfer, David W.</p> <p>2004-01-01</p> <p>Several optical methods for measuring temperature near underwater <span class="hlt">shock</span> <span class="hlt">waves</span> are reviewed and compared. The relative merits of the different techniques are compared, considering accuracy, precision, ease of use, applicable temperature range, maturity, spatial resolution, and whether or not special additives are required.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1994STIN...9526077H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1994STIN...9526077H"><span id="translatedtitle">Numerical calculations of <span class="hlt">shock-wave</span>/boundary-layer flow interactions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Huang, P. G.; Liou, W. W.</p> <p>1994-08-01</p> <p>The paper presents results of calculations for 2-D supersonic turbulent compression corner flows. The results seem to indicate that the newer, improved kappa-epsilon models offer limited advantages over the standard kappa-epsilon model in predicting the <span class="hlt">shock-wave</span>/boundary-layer flows in the 2-D compression corner over a wide range of corner angles and flow conditions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/6679548','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/6679548"><span id="translatedtitle">Dynamic Theory: some <span class="hlt">shock</span> <span class="hlt">wave</span> and energy implications</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Williams, P.E.</p> <p>1981-02-01</p> <p>The Dynamic Theory, a unifying five-dimensional theory of space, time, and matter, is examined. The theory predicts an observed discrepancy between <span class="hlt">shock</span> <span class="hlt">wave</span> viscosity measurements at low and high pressures in aluminum, a limiting mass-to-energy conversion rate consistent with the available data, and reduced pressures in electromagneticaly contained controlled-fusion plasmas.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20150003513','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20150003513"><span id="translatedtitle">Destruction of Interstellar Dust in Evolving Supernova Remnant <span class="hlt">Shock</span> <span class="hlt">Waves</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Slavin, Jonathan D.; Dwek, Eli; Jones, Anthony P.</p> <p>2015-01-01</p> <p>Supernova generated <span class="hlt">shock</span> <span class="hlt">waves</span> are responsible for most of the destruction of dust grains in the interstellar medium (ISM). Calculations of the dust destruction timescale have so far been carried out using plane parallel steady <span class="hlt">shocks</span>, however that approximation breaks down when the destruction timescale becomes longer than that for the evolution of the supernova remnant (SNR) <span class="hlt">shock</span>. In this paper we present new calculations of grain destruction in evolving, radiative SNRs. To facilitate comparison with the previous study by Jones et al. (1996), we adopt the same dust properties as in that paper. We find that the efficiencies of grain destruction are most divergent from those for a steady <span class="hlt">shock</span> when the thermal history of a <span class="hlt">shocked</span> gas parcel in the SNR differs significantly from that behind a steady <span class="hlt">shock</span>. This occurs in <span class="hlt">shocks</span> with velocities 200 km s(exp -1) for which the remnant is just beginning to go radiative. Assuming SNRs evolve in a warm phase dominated ISM, we find dust destruction timescales are increased by a factor of approximately 2 compared to those of Jones et al. (1996), who assumed a hot gas dominated ISM. Recent estimates of supernova rates and ISM mass lead to another factor of approximately 3 increase in the destruction timescales, resulting in a silicate grain destruction timescale of approximately 2-3 Gyr. These increases, while not able resolve the problem of the discrepant timescales for silicate grain destruction and creation, are an important step towards understanding the origin, and evolution of dust in the ISM.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19840009453','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19840009453"><span id="translatedtitle"><span class="hlt">Shock</span> <span class="hlt">wave</span> properties of anorthosite and gabbro</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Boslough, M. B.; Ahrens, T. J.</p> <p>1984-01-01</p> <p>Hugoniot data on San Gabriel anorthosite and San Marcos gabbro to 11 GPA are presented. Release paths in the stress-density plane and sound velocities are reported as determined from particl velocity data. Electrical interference effects precluded the determination of accurate release paths for the gabbro. Because of the loss of shear strength in the <span class="hlt">shocked</span> state, the plastic behavior exhibited by anorthosite indicates that calculations of energy partitioning due to impact onto planetary surfaces based on elastic-plastic models may underestimate the amount of internal energy deposited in the impacted surface material.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2012AIPC.1474...19C&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2012AIPC.1474...19C&link_type=ABSTRACT"><span id="translatedtitle">Sources and propagation of atmospherical acoustic <span class="hlt">shock</span> <span class="hlt">waves</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Coulouvrat, François</p> <p>2012-09-01</p> <p> within <span class="hlt">shocks</span>, is controlled by humidity, cloudiness or surface properties. Variability is large at all scales, and depends simultaneously on climate, daily meteorology, and local turbulent state, especially near the ground in the planetary boundary layer. Numerous features of outdoor propagation remain to be explored in the nonlinear case, such as complex 3D atmospheric description (role of turbulence, partial <span class="hlt">reflections</span>, gravity <span class="hlt">waves</span>) or topography.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/16230619','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/16230619"><span id="translatedtitle">Potential theory for <span class="hlt">shock</span> <span class="hlt">reflection</span> by a large-angle wedge.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Chen, Gui-Qiang; Feldman, Mikhail</p> <p>2005-10-25</p> <p>When a plane <span class="hlt">shock</span> hits a wedge head on, it experiences a <span class="hlt">reflection</span>, and then a self-similar <span class="hlt">reflected</span> <span class="hlt">shock</span> moves outward as the original <span class="hlt">shock</span> moves forward in time. Experimental, computational, and asymptotic analysis has shown that various patterns of <span class="hlt">reflected</span> <span class="hlt">shocks</span> may occur, including regular and Mach <span class="hlt">reflection</span>. However, most fundamental issues for <span class="hlt">shock</span> <span class="hlt">reflection</span> phenomena have not been understood, such as the transition among the different patterns of <span class="hlt">shock</span> <span class="hlt">reflection</span>; therefore, it is essential to establish a global existence and stability theory for <span class="hlt">shock</span> <span class="hlt">reflection</span>. On the other hand, there has been no rigorous mathematical result on the global existence and stability of solutions to <span class="hlt">shock</span> <span class="hlt">reflection</span>, especially for potential flow, which has widely been used in aerodynamics. The theoretical problems involve several challenging difficulties in the analysis of nonlinear partial differential equations including elliptic-hyperbolic mixed type, free-boundary problems, and corner singularity, especially when an elliptic degenerate curve meets a free boundary. Here we develop a potential theory to overcome these difficulties and to establish the global existence and stability of solutions to <span class="hlt">shock</span> <span class="hlt">reflection</span> by a large-angle wedge for potential flow. The techniques and ideas developed will be useful to other nonlinear problems involving similar difficulties. PMID:16230619</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010APS..DFD.QC007H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010APS..DFD.QC007H"><span id="translatedtitle">Multidimensional detonation propagation modeled via nonlinear <span class="hlt">shock</span> <span class="hlt">wave</span> superposition</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Higgins, Andrew; Mehrjoo, Navid</p> <p>2010-11-01</p> <p>Detonation <span class="hlt">waves</span> in gases are inherently multidimensional due to their cellular structure, and detonations in liquids and heterogeneous solids are often associated with instabilities and stochastic, localized reaction centers (i.e., hot spots). To explore the statistical nature of detonation dynamics in such systems, a simple model that idealizes detonation propagation as an ensemble of interacting blast <span class="hlt">waves</span> originating from spatially random point sources has been proposed. Prior results using this model exhibited features that have been observed in real detonating systems, such as anomalous scaling between axisymmetric and two-dimensional geometries. However, those efforts used simple linear superposition of the blast <span class="hlt">waves</span>. The present work uses a model of blast <span class="hlt">wave</span> superposition developed for multiple-source explosions (the LAMB approximation) that incorporates the nonlinear interaction of <span class="hlt">shock</span> <span class="hlt">waves</span> analytically, permitting the effect of a more physical model of blast <span class="hlt">wave</span> interaction to be explored. The results are suggestive of a universal behavior in systems of spatially randomized energy sources.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007ChPhy..16.3728Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007ChPhy..16.3728Z"><span id="translatedtitle">Evolution of <span class="hlt">shock</span> <span class="hlt">waves</span> formed by laser-induced breakdown in air</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhang, Yi; Li, Yu-Tong; Zheng, Zhi-Yuan; Liu, Feng; Zhong, Jia-Yong; Lin Xiao, Xuan; Liu, Feng; Lu, Xin; Zhang, Jie</p> <p>2007-12-01</p> <p>The evolution of <span class="hlt">shock</span> <span class="hlt">waves</span> produced by 7 ns laser pulses in air is investigated by time-resolved shadowgraph. A nodular structure of the <span class="hlt">shock</span> <span class="hlt">wave</span> is observed. It is found that the origin of the structure is the multi-longitudinal-microfocus caused by the astigmatism of the laser beam. The spherical <span class="hlt">shock</span> <span class="hlt">waves</span> formed by each microfocus expand gradually and collide with each other, resulting in the nodular structure of the <span class="hlt">shock</span> <span class="hlt">wave</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18..200S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18..200S"><span id="translatedtitle">The Saturnian Environment as a Unique Laboratory for Collisionless <span class="hlt">Shock</span> <span class="hlt">Waves</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sulaiman, Ali; Masters, Adam; Dougherty, Michele; Burgess, David; Fujimoto, Masaki; Hospodarsky, George</p> <p>2016-04-01</p> <p>Collisionless <span class="hlt">shock</span> <span class="hlt">waves</span> are ubiquitous in the universe and fundamental to understanding the nature of collisionless plasmas. The interplay between particles (ions and electrons) and fields (electromagnetic) introduces a variety of both physical and geometrical parameters such as Mach numbers (e.g. MA, Mf), β, and θBn. These vary drastically from terrestrial to astrophysical regimes resulting in radically different characteristics of <span class="hlt">shocks</span>. This poses two complexities. Firstly, separating the influences of these parameters on physical mechanisms such as energy dissipation. Secondly, correlating observations of <span class="hlt">shock</span> <span class="hlt">waves</span> over a wide range of each parameter, enough to span across different regimes. Investigating the latter has been restricted since the majority of studies on <span class="hlt">shocks</span> at exotic regimes (such as supernova remnants) have been achieved either remotely or via simulations, but rarely by means of in-situ observations. It is not clear what happens in the higher MA regime. Here we show the parameter space of MA for all bow <span class="hlt">shock</span> crossings from 2004-2012 as measured by the Cassini spacecraft. We found that the Saturnian bow <span class="hlt">shock</span> exhibits characteristics akin to both terrestrial and astrophysical regimes (MA of order 100), which is principally controlled by the upstream magnetic field strength. Moreover, we estimated the θbn of each crossing and were able to further constrain the sample into categories of similar features. Our results demonstrate how MA plays a central role in controlling the onset of physical mechanisms in collisionless <span class="hlt">shocks</span>, particularly reformation. While ongoing studies have investigated this process extensively both theoretically and via simulations, their observations remain few and far between. We show conclusive evidence for cyclic reformation controlled by specular ion <span class="hlt">reflection</span> occurring at the predicted timescale of ˜0.3 τc, where τc is the ion gyroperiod. In addition, we experimentally underpin the relationship between</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015PhPl...22j2307A&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015PhPl...22j2307A&link_type=ABSTRACT"><span id="translatedtitle">Ion acoustic <span class="hlt">shock</span> <span class="hlt">wave</span> in collisional equal mass plasma</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Adak, Ashish; Ghosh, Samiran; Chakrabarti, Nikhil</p> <p>2015-10-01</p> <p>The effect of ion-ion collision on the dynamics of nonlinear ion acoustic <span class="hlt">wave</span> in an unmagnetized pair-ion plasma has been investigated. The two-fluid model has been used to describe the dynamics of both positive and negative ions with equal masses. It is well known that in the dynamics of the weakly nonlinear <span class="hlt">wave</span>, the viscosity mediates <span class="hlt">wave</span> dissipation in presence of weak nonlinearity and dispersion. This dissipation is responsible for the <span class="hlt">shock</span> structures in pair-ion plasma. Here, it has been shown that the ion-ion collision in presence of collective phenomena mediated by the plasma current is the source of dissipation that causes the Burgers' term which is responsible for the <span class="hlt">shock</span> structures in equal mass pair-ion plasma. The dynamics of the weakly nonlinear <span class="hlt">wave</span> is governed by the Korteweg-de Vries Burgers equation. The analytical and numerical investigations revealed that the ion acoustic <span class="hlt">wave</span> exhibits both oscillatory and monotonic <span class="hlt">shock</span> structures depending on the frequency of ion-ion collision parameter. The results have been discussed in the context of the fullerene pair-ion plasma experiments.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22486428','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22486428"><span id="translatedtitle">Ion acoustic <span class="hlt">shock</span> <span class="hlt">wave</span> in collisional equal mass plasma</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Adak, Ashish; Ghosh, Samiran; Chakrabarti, Nikhil</p> <p>2015-10-15</p> <p>The effect of ion-ion collision on the dynamics of nonlinear ion acoustic <span class="hlt">wave</span> in an unmagnetized pair-ion plasma has been investigated. The two-fluid model has been used to describe the dynamics of both positive and negative ions with equal masses. It is well known that in the dynamics of the weakly nonlinear <span class="hlt">wave</span>, the viscosity mediates <span class="hlt">wave</span> dissipation in presence of weak nonlinearity and dispersion. This dissipation is responsible for the <span class="hlt">shock</span> structures in pair-ion plasma. Here, it has been shown that the ion-ion collision in presence of collective phenomena mediated by the plasma current is the source of dissipation that causes the Burgers' term which is responsible for the <span class="hlt">shock</span> structures in equal mass pair-ion plasma. The dynamics of the weakly nonlinear <span class="hlt">wave</span> is governed by the Korteweg-de Vries Burgers equation. The analytical and numerical investigations revealed that the ion acoustic <span class="hlt">wave</span> exhibits both oscillatory and monotonic <span class="hlt">shock</span> structures depending on the frequency of ion-ion collision parameter. The results have been discussed in the context of the fullerene pair-ion plasma experiments.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19980039333','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19980039333"><span id="translatedtitle">Studies of <span class="hlt">Shock</span> <span class="hlt">Wave</span> Interactions with Homogeneous and Isotropic Turbulence</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Briassulis, G.; Agui, J.; Watkins, C. B.; Andreopoulos, Y.</p> <p>1998-01-01</p> <p>A nearly homogeneous nearly isotropic compressible turbulent flow interacting with a normal <span class="hlt">shock</span> <span class="hlt">wave</span> has been studied experimentally in a large <span class="hlt">shock</span> tube facility. Spatial resolution of the order of 8 Kolmogorov viscous length scales was achieved in the measurements of turbulence. A variety of turbulence generating grids provide a wide range of turbulence scales. Integral length scales were found to substantially decrease through the interaction with the <span class="hlt">shock</span> <span class="hlt">wave</span> in all investigated cases with flow Mach numbers ranging from 0.3 to 0.7 and <span class="hlt">shock</span> Mach numbers from 1.2 to 1.6. The outcome of the interaction depends strongly on the state of compressibility of the incoming turbulence. The length scales in the lateral direction are amplified at small Mach numbers and attenuated at large Mach numbers. Even at large Mach numbers amplification of lateral length scales has been observed in the case of fine grids. In addition to the interaction with the <span class="hlt">shock</span> the present work has documented substantial compressibility effects in the incoming homogeneous and isotropic turbulent flow. The decay of Mach number fluctuations was found to follow a power law similar to that describing the decay of incompressible isotropic turbulence. It was found that the decay coefficient and the decay exponent decrease with increasing Mach number while the virtual origin increases with increasing Mach number. A mechanism possibly responsible for these effects appears to be the inherently low growth rate of compressible shear layers emanating from the cylindrical rods of the grid.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19840010505','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19840010505"><span id="translatedtitle">An experimental investigation of the impingement of a planar <span class="hlt">shock</span> <span class="hlt">wave</span> on an axisymmetric body at Mach 3</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Brosh, A.; Kussoy, M. I.</p> <p>1983-01-01</p> <p>An experimental study of the flow caused by a planar <span class="hlt">shock</span> <span class="hlt">wave</span> impinging obliquely on a cylinder is presented. The complex three dimensional <span class="hlt">shock</span> <span class="hlt">wave</span> and boundary layer interaction occurring in practical problems, such as the <span class="hlt">shock</span> <span class="hlt">wave</span> impingement from the shuttle nose on an external fuel tank, and store carriage interference on a supersonic tactical aircraft were investigated. A data base for numerical computations of complex flows was also investigated. The experimental techniques included pressure measurements and oil flow patterns on the surface of the cylinder, and shadowgraphs and total and static pressure surveys on the leeward and windward planes of symmetry. The complete data is presented in tabular form. The results reveal a highly complex flow field with two separation zones, regions of high crossflow, and multiple <span class="hlt">reflected</span> <span class="hlt">shocks</span> and expansion fans.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007APS..SHK.A1001T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007APS..SHK.A1001T"><span id="translatedtitle">Applications of <span class="hlt">Shock</span> <span class="hlt">Wave</span> Research to Developments of Therapeutic Devices.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Takayama, Kazuyoshi</p> <p>2007-06-01</p> <p>Underwater <span class="hlt">shock</span> <span class="hlt">wave</span> research applied to medicine started in 1980 by exploding micro lead azide pellets in water. Collaboration with urologists in the School of Medicine, Tohoku University at the same time was directed to disintegration of kidney stones by controlling <span class="hlt">shock</span> <span class="hlt">waves</span>. We initially proposed a miniature truncated ellipsoidal cavity for generating high-pressures enough to disintegrate the stone but gave up the idea, when encountering the Dornie Systems' invention of an extracorporeal <span class="hlt">shock</span> <span class="hlt">wave</span> lithotripter (ESWL). Then we confirmed its effectiveness by using 10 mg silver azide pellets and constructed our own lithotripter, which was officially approved for a clinical use in 1987. Tissue damage during ESWL was attributable to bubble collapse and we convinced it could be done in a controlled fashion. In 1996, we used 160 mJ pulsed Ho:YAG laser beam focusing inside a catheter for <span class="hlt">shock</span> generation and applied it to the revascularization of cerebral embolism, which is recently expanded to the treatment of pulmonary infarction. Micro water jets discharged in air were so effective to dissect soft tissues preserving small blood vessels. Animal experiments are successfully performed with high frequency water jets driven by an actuator-assisted micro-pump. A metal foil is deformed at high speed by a Q-switched Nd:YAG laser beam loading. We used this technique to project micro-particles or dry drugs attached on its reverse side and extended it to a laser ablation assisted dry drug delivery or DNA introductory system.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009JAP...106h6102M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009JAP...106h6102M"><span id="translatedtitle"><span class="hlt">Shock</span> <span class="hlt">wave</span> driven liquid microjets for drug delivery</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Menezes, Viren; Kumar, Satyam; Takayama, Kazuyoshi</p> <p>2009-10-01</p> <p>A nonintrusive, minimally invasive, needle-less technique to deliver liquids into soft targets is presented. The technique uses a laser-induced <span class="hlt">shock</span> <span class="hlt">wave</span> to drive a liquid microjet at a very high speed such that the jet has sufficient momentum to penetrate soft targets. The method can be used to deliver liquid drugs into soft tissues in the human body. The liquid to be delivered is sandwiched between 200 μm thick aluminum foil and a base plate with a perforation of 100 μm diameter. The aluminum foil is ablated using an Nd:YAG laser beam in order to launch a <span class="hlt">shock</span> <span class="hlt">wave</span> through it. The <span class="hlt">shock</span> <span class="hlt">wave</span> from the foil is transmitted to the sandwiched liquid, which becomes pressurized by the <span class="hlt">shock</span> propagation and emanates as a microjet through the perforation in the base plate. The microjet thus generated has a steady, average speed of over 200 m/s. The technique has been tested on gelatin models (5% gelatin), in which the jet penetrated to a depth of more than a millimeter.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ShWav.tmp...54Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ShWav.tmp...54Z"><span id="translatedtitle">Experimental research on dust lifting by propagating <span class="hlt">shock</span> <span class="hlt">wave</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Żydak, P.; Oleszczak, P.; Klemens, R.</p> <p>2016-05-01</p> <p>The aim of the presented work was to study the dust lifting process from a layer of dust behind a propagating <span class="hlt">shock</span> <span class="hlt">wave</span>. The experiments were conducted with the use of a <span class="hlt">shock</span> tube and a specially constructed, five-channel laser optical device enabling measurements at five positions located in one vertical plane along the height of the tube. The system enabled measurements of the delay in lifting up of the dust from the layer, and the vertical velocity of the dust cloud was calculated from the dust concentration measurements. The research was carried out for various initial conditions and for three fractions of black coal dust. In the presented tests, three <span class="hlt">shock</span> <span class="hlt">wave</span> velocities: 450, 490 and 518 m/s and three dust layer thicknesses, equal to 1.0, 1.5 and 2.0 mm, were taken into consideration. On the grounds of the obtained experimental results, it was assumed that the vertical component of the lifted dust velocity is a function of the dust particle diameter, the velocity of the air flow in the channel, the layer thickness and the dust bulk density. It appeared, however, that lifting up of the dust from the thick layers, thicker than 1 mm, is a more complex process than that from thin layers and still requires further research. A possible explanation is that the <span class="hlt">shock</span> <span class="hlt">wave</span> action upon the thick layer results in its aggregation in the first stage of the dispersing process, which suppresses the dust lifting process.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1998APS..DFD..NF03A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1998APS..DFD..NF03A"><span id="translatedtitle">Vorticity Transfer in <span class="hlt">Shock</span> <span class="hlt">Wave</span> Interactions with Turbulence and Vortices</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Agui, J. H.; Andreopoulos, J.</p> <p>1998-11-01</p> <p>Time-dependent, three-dimensional vorticity measurements of <span class="hlt">shock</span> <span class="hlt">waves</span> interacting with grid generated turbulence and concentrated tip vortices were conducted in a large diameter <span class="hlt">shock</span> tube facility. Two different mesh size grids and a NACA-0012 semi-span wing acting as a tip vortex generator were used to carry out different relative Mach number interactions. The turbulence interactions produced a clear amplification of the lateral and spanwise vorticity rms, while the longitudinal component remained mostly unaffected. By comparison, the tip vortex/<span class="hlt">shock</span> <span class="hlt">wave</span> interactions produced a two fold increase in the rms of longitudinal vorticity. Considerable attention was given to the vorticity source terms. The mean and rms of the vorticity stretching terms dominated by 5 to 7 orders of magnitude over the dilitational compression terms in all the interactions. All three signals of the stretching terms manifested very intermittent, large amplitude peak events which indicated the bursting character of the stretching process. Distributions of these signals were characterized by extremely large levels of flatness with varying degrees of skewness. These distribution patterns were found to change only slightly through the turbulence interactions. However, the tip vortex/<span class="hlt">shock</span> <span class="hlt">wave</span> interactions brought about significant changes in these distributions which were associated with the abrupt structural changes of the vortex after the interaction.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19950002073&hterms=intermolecular+forces&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dintermolecular%2Bforces','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19950002073&hterms=intermolecular+forces&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dintermolecular%2Bforces"><span id="translatedtitle"><span class="hlt">Shock</span> <span class="hlt">wave</span> structure using nonlinear model Boltzmann equations</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Segal, Ben Maurice</p> <p>1971-01-01</p> <p>The structure of a strong plane <span class="hlt">shock</span> <span class="hlt">wave</span> in a monatomic rarefied perfect gas is one of the simplest problems able to be posed in kinetic theory, and one of the hardest to solve. Its simplicity lies in the absence of solid boundaries, geometrical complications, or internal molecular energy. Its difficulty arises from the great departure of the gas from equilibrium within the <span class="hlt">shock</span>, which invalidates many of the techniques used successfully elsewhere in kinetic theory. In addition to this theoretical challenge, the modern development of ballistics and hypersonic flight has helped to stimulate extensive theoretical and experimental interest in the <span class="hlt">shock</span> problem. The experimenters in turn have encountered great difficulties on account of the very small physical dimensions of <span class="hlt">shocks</span>. In fact, until very recently indeed, any close comparisons of theoretical and experimental <span class="hlt">shock</span> structure results have been rather unprofitable due to the inadequacies of both theory and experiment. During the last few years this situation has been appreciably improved by development of the Monte Carlo method. This allows idealized 'experiments' to be performed on large computers instead of in wind tunnels, using a known intermolecular force law. The most developed of these methods has been shown to be equivalent theoretically to the Boltzmann equation and to give results which agree extremely closely with measurements of high accuracy. Thus Monte Carlo results not only form the soundest basis for our present theoretical knowledge of <span class="hlt">shock</span> <span class="hlt">wave</span> structure, but, for purposes of developing other theories, can also be considered a very valuable experimental resource. However, such results remain very expensive to obtain. In this thesis we develop more economical kinetic theory methods for the approximate prediction of <span class="hlt">shock</span> structure, and compare our results with those of the Monte Carlo method.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active"><span>22</span></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_22 --> <div id="page_23" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li class="active"><span>23</span></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="441"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19900002654','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19900002654"><span id="translatedtitle">Simulation of glancing <span class="hlt">shock</span> <span class="hlt">wave</span> and boundary layer interaction</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hung, Ching-Mao</p> <p>1989-01-01</p> <p><span class="hlt">Shock</span> <span class="hlt">waves</span> generated by sharp fins, glancing across a laminar boundary layer growing over a flat plate, are simulated numerically. Several basic issues concerning the resultant three-dimensional flow separation are studied. Using the same number of grid points, different grid spacings are employed to investigate the effects of grid resolution on the origin of the line of separation. Various <span class="hlt">shock</span> strengths (generated by different fin angles) are used to study the so-called separated and unseparated boundary layer and to establish the existence or absence of the secondary separation. The usual interpretations of the flow field from previous studies and new interpretations arising from the present simulation are discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19720052777&hterms=nuns&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dnuns','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19720052777&hterms=nuns&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dnuns"><span id="translatedtitle">'Thunder' - <span class="hlt">Shock</span> <span class="hlt">waves</span> in pre-biological organic synthesis.</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Bar-Nun, A.; Tauber, M. E.</p> <p>1972-01-01</p> <p>Theoretical study of the gasdynamics and chemistry of lightning-produced <span class="hlt">shock</span> <span class="hlt">waves</span> in a postulated primordial reducing atmosphere. It is shown that the conditions are similar to those encountered in a previously performed <span class="hlt">shock</span>-tube experiment which resulted in 36% of the ammonia in the original mixture being converted into amino acids. The calculations give the (very large) energy rate of about 0.4 cal/sq cm/yr available for amino acid production, supporting previous hypotheses that 'thunder' could have been responsible for efficient large-scale production of organic molecules serving as precursors of life.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19730037344&hterms=shock+initiation&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dshock%2Binitiation','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19730037344&hterms=shock+initiation&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dshock%2Binitiation"><span id="translatedtitle"><span class="hlt">Shock</span> <span class="hlt">wave</span> compression of iron-silicate garnet.</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Graham, E. K.; Ahrens, T. J.</p> <p>1973-01-01</p> <p><span class="hlt">Shock</span> <span class="hlt">wave</span> compression data to over 650 kb are presented for single-crystal almandine garnet. The data indicate the initiation of a phase transformation near 200 kb. Total transition to the high-pressure polymorph occurs at approximately 300 kb. The elastic properties of the high-pressure phase are calculated from the metastable Hugoniot data by using the linear <span class="hlt">shock</span> velocity-particle velocity relationships. The overall results obtained strongly suggest that upper mantle minerals are likely to occur in the ilmenite structure over a substantial part of the lower mantle.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1983PhFl...26.1234N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1983PhFl...26.1234N"><span id="translatedtitle">Analysis of self-similar problems of imploding <span class="hlt">shock</span> <span class="hlt">waves</span> by the method of characteristics</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nakamura, Y.</p> <p>1983-05-01</p> <p>The asymptotic self-similar form of cylindrically or spherically imploding <span class="hlt">shock</span> <span class="hlt">waves</span> is extracted by numerically solving non-self-similar problems. The <span class="hlt">shock</span> <span class="hlt">wave</span> is generated by a contracting piston with finite initial velocity. For the initial <span class="hlt">shock</span> motion, a perturbation method is used to determine the starting condition for the numerical calculation. Propagation of the <span class="hlt">shock</span> <span class="hlt">wave</span> and flow field properties are obtained and the transition of the non-self-similar motion of the <span class="hlt">shock</span> <span class="hlt">wave</span> into the self-similar one is presented. Good agreement between self-similar exponents determined from the variation of the <span class="hlt">shock</span> strength and those calculated by Guderley is obtained.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/21538207','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/21538207"><span id="translatedtitle">Enhancement of airborne <span class="hlt">shock</span> <span class="hlt">wave</span> by laser-induced breakdown of liquid column in laser <span class="hlt">shock</span> cleaning</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Jang, Deoksuk; Kim, Dongsik; Park, Jin-Goo</p> <p>2011-04-01</p> <p>In laser <span class="hlt">shock</span> cleaning (LSC), the <span class="hlt">shock</span> <span class="hlt">wave</span> is generated by laser-induced breakdown of the ambient gas. The <span class="hlt">shock</span> <span class="hlt">wave</span> intensity has thus been a factor limiting the performance of the LSC process. In this work, a novel method of amplifying a laser-induced plasma-generated <span class="hlt">shock</span> <span class="hlt">wave</span> by the breakdown of a liquid column is proposed and analyzed. When the laser beam is focused on a microscale liquid column, a <span class="hlt">shock</span> <span class="hlt">wave</span> having a significantly amplified intensity compared to that generated by air breakdown alone can be generated in air. Therefore, substantially amplified cleaning force can be obtained. The dynamics of a <span class="hlt">shock</span> <span class="hlt">wave</span> induced by a Q-switched Nd:YAG laser was analyzed by laser flash shadowgraphy. The peak pressure of the laser-induced <span class="hlt">shock</span> <span class="hlt">wave</span> was approximately two times greater than that of air breakdown at the same laser fluence. The proposed method of <span class="hlt">shock</span> <span class="hlt">wave</span> generation is expected to be useful in various applications of laser <span class="hlt">shock</span> processing, including surface cleaning.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19950039618&hterms=generation+compare&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dgeneration*%2Bcompare*','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19950039618&hterms=generation+compare&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dgeneration*%2Bcompare*"><span id="translatedtitle"><span class="hlt">Shock</span> propagation and the generation of magnetohydrodynamic <span class="hlt">wave</span> fields in inhomogeneous molecular clouds</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Miesch, Mark S.; Zweibel, Ellen G.</p> <p>1994-01-01</p> <p>We develop a simple one-dimensional model for the interaction of a steady, thin, planar <span class="hlt">shock</span> <span class="hlt">wave</span> with a nonrigid cloud which may be in motion relative to the surrounding medium, and we apply the model to <span class="hlt">shocks</span> impinging on, and propagating through, molecular clouds. Both 'adiabatic' (gamma = 5/3) and radiative (gamma = 1) <span class="hlt">shocks</span> are considered and we allow for the presence of a uniform magnetic field directed either parallel or perpendicular to the <span class="hlt">shock</span> normal. The former field orientation is equivalent to the hydrodynamic case, and the latter involves only fast MHD <span class="hlt">shocks</span>. We focus on the manner in which such <span class="hlt">shocks</span> can generate internal kinetic motions in the cloud on a range of size and density scales through the direct acceleration of cores and clumps by <span class="hlt">shocks</span> transmitted into them and through the generation of an MHD wavefield via the <span class="hlt">reflection</span> of the incident <span class="hlt">shock</span> at clump boundaries. We find that stronger incident Mach numbers and smaller density contrasts lead to more efficient cloud acceleration, as do isothermal intercloud <span class="hlt">shocks</span> and small intercloud magnetic field strengths. The acceleration efficiency is insensitive to the adiabatic index and the magnetic field strength in the cloud itself. For typical parameter choices, the direct acceleration of clouds and clumps by strong <span class="hlt">shocks</span> is found to be substantial and could at least in part account for their observed velocity dispersions. If the <span class="hlt">shocks</span> are moderately weak, the final velocity of the cloud is linearly related to its initial velocity, with higher acceleration giving shallower slopes (i.e., final velocity distributions which are less sensitive to the initial distribution). Compared to the kinetic energy of the postshock cloud, the energy given to the wavefield at each encounter is small, and the heating of the interclump medium by the dissipation of this wavefield is found to be insufficient to balance the cooling rate in the cloud as a whole (although it may be important in particular</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AIPC.1359...42Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AIPC.1359...42Z"><span id="translatedtitle">A New Acoustic Lens Design for Electromagnetic <span class="hlt">Shock</span> <span class="hlt">Wave</span> Lithotripters</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhong, Pei; Smith, Nathan; Simmons, Neal W.; Sankin, Georgy</p> <p>2011-09-01</p> <p>The 3rd-generation electromagnetic (EM) <span class="hlt">shock</span> <span class="hlt">wave</span> lithotripters often have narrow focal width and high peak pressure compared to the original Dornier HM-3. In addition, the pressure waveform produced by a typical EM lithotripter has a secondary compressive <span class="hlt">wave</span> following the tensile component that suppresses lithotripter pulse induced cavitation, which may impact negatively on stone comminution. These characteristic changes in the modern EM lithotripters may contribute in part to their reduced effectiveness observed clinically. To overcome these two drawbacks, we have designed a new acoustic lens for the Siemens Modularis EM lithotripter that produces an idealized pressure waveform similar to that of the HM-3 with broad focal width and low peak pressure. At acoustic pulse energy of 53 mJ, the new lens design enlarges the -6 dB focal width of the Modularis by 47% while significantly reducing the second compressive <span class="hlt">wave</span> in the lithotripter pulse throughout its focal plane. After 2000 <span class="hlt">shocks</span>, in vitro comminution produced by the original and new lens designs are 100% and 99% at the lithotripter focus, and 52±16% and 77±8% (p<0.001) at 10 mm off axis, respectively. Corresponding values for stones that are translated to mimic respiratory motion during <span class="hlt">shock</span> <span class="hlt">wave</span> lithotripsy are 83±4% and 91±1% (p<0.01), demonstrating the significant performance improvement provided by the new lens design.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19800008577','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19800008577"><span id="translatedtitle">Second sound <span class="hlt">shock</span> <span class="hlt">waves</span> and critical velocities in liquid helium 2. Ph.D. Thesis</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Turner, T. N.</p> <p>1979-01-01</p> <p>Large amplitude second-sound <span class="hlt">shock</span> <span class="hlt">waves</span> were generated and the experimental results compared to the theory of nonlinear second-sound. The structure and thickness of second-sound <span class="hlt">shock</span> fronts are calculated and compared to experimental data. Theoretically it is shown that at T = 1.88 K, where the nonlinear <span class="hlt">wave</span> steepening vanishes, the thickness of a very weak <span class="hlt">shock</span> must diverge. In a region near this temperature, a finite-amplitude <span class="hlt">shock</span> pulse evolves into an unusual double-<span class="hlt">shock</span> configuration consisting of a front steepened, temperature raising <span class="hlt">shock</span> followed by a temperature lowering <span class="hlt">shock</span>. Double-<span class="hlt">shocks</span> are experimentally verified. It is experimentally shown that very large second-sound <span class="hlt">shock</span> <span class="hlt">waves</span> initiate a breakdown in the superfluidity of helium 2, which is dramatically displayed as a limit to the maximum attainable <span class="hlt">shock</span> strength. The value of the maximum <span class="hlt">shock</span>-induced relative velocity represents a significant lower bound to the intrinsic critical velocity of helium 2.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012ASSP...33..129S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012ASSP...33..129S"><span id="translatedtitle">Alfvénic Solitary and <span class="hlt">Shock</span> <span class="hlt">Waves</span> in Plasmas</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Shukla, Padma Kant; Eliasson, Bengt; Stenflo, Lennart</p> <p></p> <p>We present a review of nonlinear Alfvénic solitary and <span class="hlt">shock</span> <span class="hlt">waves</span> in a magnetized electron-ion plasma. The dynamics of these nonlinear dispersive Alfvén <span class="hlt">waves</span> is governed by the two-fluid equations, coupled with Faraday's and Ampère's laws. First, we demonstrate the existence of large amplitude compressional Alfvénic solitary and <span class="hlt">shock</span> <span class="hlt">waves</span> propagating across the external magnetic field in a warm electron-ion magnetoplasma. It is found that these nonlinear structures can exist in well defined speed ranges above the Alfvén speed, and their widths are several times larger than the electron skin depths. Second, we study the formation of nonlinear slow magnetosonic solitary (SMS) <span class="hlt">waves</span> propagating almost perpendicular to the external magnetic field direction. The propagation speed of the SMS <span class="hlt">waves</span> is below the Alfvén speed and their width is a few ion skin depth in a collisionless magnetoplasma. The nonlinear dispersive Alfvén <span class="hlt">waves</span>, as discussed here, can be associated with localized electromagnetic field excitations in magnetized laboratory and space plasmas that are composed of magnetized electrons and ions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22410459','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22410459"><span id="translatedtitle">Investigation of <span class="hlt">shock-shock</span> interaction and Mach <span class="hlt">reflection</span> in laterally colliding laser-blow-off plasmas</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Kumar, Bhupesh; Singh, R. K.; Sengupta, Sudip; Kaw, P. K.; Kumar, Ajai</p> <p>2015-06-15</p> <p>Interactions of two Li plasma plumes and <span class="hlt">shock</span> <span class="hlt">waves</span> are investigated at various pressures (∼10{sup −5} to 3 mbar) in the argon gas ambient. Fast imaging and optical emission spectroscopy are used to study the plume dynamics and characteristic emission of plasmas. The plasma plumes are created in laser-blow-off geometry. The expansion of plasma plumes in the ambient gas leads to the formation of an interaction zone. The formation of interaction zone is dependent on the ambient pressure and below a certain pressure, no significant change is observed in the shape and size of the interaction plasma. In the higher pressure, formation of interaction zone and its shape are dependent on ambient pressure. Dynamics of seed plasmas and interaction zone are also affected by the <span class="hlt">shock-shock</span> interactions. The <span class="hlt">shock-shock</span> interaction depends on the angle of incidence (α) between two <span class="hlt">shock</span> <span class="hlt">waves</span> at the initial time of interaction but as the plumes expand, the <span class="hlt">shock-shock</span> interaction does not follow α dependence.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006PhDT.......240C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006PhDT.......240C"><span id="translatedtitle">Shape stability and violent collapse of microbubbles interacting with acoustic <span class="hlt">waves</span> and <span class="hlt">shocks</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Calvisi, Michael Louis</p> <p></p> <p>This dissertation elucidates the effect of nonspherical perturbations on the energy-focusing properties of bubble collapses driven by acoustic and <span class="hlt">shock</span> <span class="hlt">wave</span> forcing. First, the influence of acoustic forcing on shape stability is explored and two models of bubble breakup---one based on perturbation analysis and the other based on numerical solution of the Laplace equation---are compared, showing remarkably good agreement. The Laplace equation for axisymmetric geometry is solved through use of a Boundary Integral Method that can efficiently model highly deformed; even toroidal bubble geometries. This model is based on the work of previous researchers but is significantly augmented for our purposes to simulate extremely violent, acoustically-driven collapses. Our numerical model based on the Boundary Integral Method is then used to explore the effect of shape stability on energy concentration in the bubble interior by comparing the peak temperatures and pressures of spherical to nonspherical bubble collapses. It is demonstrated that for very intense collapses, nonspherical bubbles do not focus the energy as efficiently as spherical collapses due to the conversion of some of the incident acoustic energy into kinetic energy of a liquid jet that pierces the bubble near the point of minimum volume. This is clarified by a calculation of the (gas) thermal equivalent of this liquid kinetic energy. Finally, the effect of <span class="hlt">shock</span> <span class="hlt">wave</span> forcing on bubbles is analyzed in the vicinity of a rigid boundary. Through calculation of quantities such as kinetic energy and Kelvin impulse of the surrounding liquid, the physics of <span class="hlt">shock</span>-bubble interaction near a wall is illuminated. A key finding is that <span class="hlt">reflection</span> of the incident <span class="hlt">shock</span> <span class="hlt">wave</span> enhances the intensity of bubble collapse in the near region due to constructive interference between the incident and <span class="hlt">reflected</span> <span class="hlt">shock</span> <span class="hlt">waves</span>. Conversely, destructive interference suppresses the intensity of such collapses further away from the surface</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015PhDT.........1J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015PhDT.........1J"><span id="translatedtitle">The effect of <span class="hlt">shock</span> <span class="hlt">wave</span> impingement on thin, woven glass fiber reinforced, polymer composite plates</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jahnke, Douglas M.</p> <p></p> <p> deformation of the test specimen. The technique has been validated by comparing the results obtained in a static experiment with the results measured by laser displacement sensors. Additional validation of dynamically obtained strain measurements was carried out by using a 13 mm (1/2") thick in-house fabricated composite specimen with embedded strain gauges and piezoelectric sensors. Surface mounted sensors due to the large inertia forces experienced by a test specimen tend to detach from it almost immediately after the <span class="hlt">shock</span> impact, so very little useful data could be collected. The present work has created a strong foundation in testing methodology and baseline results in studying the effects of <span class="hlt">shock</span> <span class="hlt">wave</span> impingement on FRP composites. It was found that the maximum deformation of the plate occurs immediate after the <span class="hlt">shock</span> impact and much before the whole loading cycle is completed. The results of permanent deformation have been normalized by using the impulse of the loading force. Additional work has been focused on the energy exchange between the incoming <span class="hlt">shock</span> <span class="hlt">wave</span> and the specimen. Understanding how much energy is associated with the <span class="hlt">shock</span> <span class="hlt">reflection</span>, transmission, absorption, or passed through is critical to designing protective systems using FRP composites.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007ShWav..16..477S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007ShWav..16..477S"><span id="translatedtitle">The curious events leading to the theory of <span class="hlt">shock</span> <span class="hlt">waves</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Salas, Manuel D.</p> <p>2007-07-01</p> <p>We review the history of the development of the modern theory of <span class="hlt">shock</span> <span class="hlt">waves</span>. Several attempts at an early-theory quickly collapsed for lack of foundations in mathematics and thermodynamics. It is not until the works of Rankine and later Hugoniot that a full theory is established. Rankine is the first to show that within the <span class="hlt">shock</span> a non-adiabatic process must occur. Hugoniot showed that in the absence of viscosity and heat conduction conservation of energy implies conservation of entropy in smooth regions and a jump in entropy across a <span class="hlt">shock</span>. Even after the theory is fully developed, old notions continue to pervade the literature well into the early part of the twentieth century.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19930035432&hterms=asme&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dasme','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19930035432&hterms=asme&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dasme"><span id="translatedtitle">Hypersonic flow separation in <span class="hlt">shock</span> <span class="hlt">wave</span> boundary layer interactions</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hamed, A.; Kumar, Ajay</p> <p>1992-01-01</p> <p>An assessment is presented for the experimental data on separated flow in <span class="hlt">shock</span> <span class="hlt">wave</span> turbulent boundary layer interactions at hypersonic and supersonic speeds. The data base consists mainly of two dimensional and axisymmetric interactions in compression corners or cylinder-flares, and externally generated oblique <span class="hlt">shock</span> interactions with boundary layers over flat plates or cylindrical surfaces. The conditions leading to flow separation and the subsequent changes in the flow empirical correlations for incipient separation are reviewed. The effects of the Mach number, Reynolds number, surface cooling and the methods of detecting separation are discussed. The pertinent experimental data for the separated flow characteristics in separated turbulent boundary layer <span class="hlt">shock</span> interaction are also presented and discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20060047586','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20060047586"><span id="translatedtitle">The Curious Events Leading to the Theory of <span class="hlt">Shock</span> <span class="hlt">Waves</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Salas, Manuel D.</p> <p>2006-01-01</p> <p>We review the history of the development of the modern theory of <span class="hlt">shock</span> <span class="hlt">waves</span>. Several attempts at an early-theory quickly collapsed for lack of foundations in mathematics and thermodynamics. It is not until the works of Rankine and later Hugoniot that a full theory is established. Rankine is the first to show that within the <span class="hlt">shock</span> a non-adiabatic process must occur. Hugoniot showed that in the absence of viscosity and heat conduction conservation of energy implies conservation of entropy in smooth regions and a jump in entropy across a <span class="hlt">shock</span>. Even after the theory is fully developed, old notions continue to pervade the literature well into the early part of the 20th Century.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2002PhDT.........5M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2002PhDT.........5M"><span id="translatedtitle">Particle Acceleration at Relativistic and Ultra-Relativistic <span class="hlt">Shock</span> <span class="hlt">Waves</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Meli, A.</p> <p></p> <p>We perform Monte Carlo simulations using diffusive <span class="hlt">shock</span> acceleration at relativistic and ultra-relativistic <span class="hlt">shock</span> <span class="hlt">waves</span>. High upstream flow gamma factors are used, Γ=(1-uup2/c2)-0.5, which are relevant to models of ultra-relativistic particle <span class="hlt">shock</span> acceleration in the central engines and relativistic jets of Active Galactic Nuclei (AGN) and in Gamma-Ray Burst (GRB) fireballs. Numerical investigations are carried out on acceleration properties in the relativistic and ultra-relativistic flow regime (Γ ˜ 10-1000) concerning angular distributions, acceleration time scales, particle energy gain versus number of crossings and spectral shapes. We perform calculations for both parallel and oblique sub-luminal and super-luminal <span class="hlt">shocks</span>. For parallel and oblique sub-luminal <span class="hlt">shocks</span>, the spectra depend on whether or not the scattering is represented by pitch angle diffusion or by large angle scattering. The large angle case exhibits a distinctive structure in the basic power-law spectrum not nearly so obvious for small angle scattering. However, both cases yield a significant 'speed-up' of acceleration rate when compared with the conventional, non-relativistic expression, tacc=[c/(uup-udown)] (λup/uup+λdown/udown). An energization by a factor Γ2 for the first crossing cycle and a large energy gains for subsequent crossings as well as the high 'speed-up' factors found, are important in supporting past works, especially the models developed by Vietri and Waxman on ultra-high energy cosmic ray, neutrino and gamma-ray production in GRB. For oblique super-luminal <span class="hlt">shocks</span>, we calculate the energy gain and spectral shape for a number of different inclinations. For this case the acceleration of particles is 'pictured' by a <span class="hlt">shock</span> drift mechanism. We use high gamma flows with Lorentz factors in the range 10-40 which are relevant to ultra-relativistic <span class="hlt">shocks</span> in AGN accretion disks and jets. In all investigations we closely follow the particle's trajectory along the magnetic field</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010ZaMP...61...87P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010ZaMP...61...87P"><span id="translatedtitle">Group theoretic method for analyzing interaction of a discontinuity <span class="hlt">wave</span> with a strong <span class="hlt">shock</span> in an ideal gas</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pandey, Manoj</p> <p>2010-02-01</p> <p>A group theoretic method is used to obtain an exact particular solution to the system of partial differential equations, describing one-dimensional unsteady planar, cylindrically and spherically symmetric motions in an ideal gas, involving <span class="hlt">shock</span> <span class="hlt">waves</span>. It is interesting to remark that the exact solution obtained here is precisely the blast <span class="hlt">wave</span> solution obtained earlier using a different method of approach. Further, the evolution of a discontinuity <span class="hlt">wave</span> and its interaction with the strong <span class="hlt">shock</span> are studied within the state characterized by the exact particular solution. The properties of <span class="hlt">reflected</span> and transmitted <span class="hlt">waves</span> and the jump in the <span class="hlt">shock</span> acceleration are completely characterized, and certain observations are noted in respect to their contrasting behavior.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015PhDT........41O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015PhDT........41O"><span id="translatedtitle">Oblique <span class="hlt">Shock</span> <span class="hlt">Wave</span> Effects on Impulsively Accelerated Heavy Gas Column</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Olmstead, Dell T.</p> <p></p> <p>An experimental study was performed to elucidate the fundamental physics of <span class="hlt">shock</span>-induced mixing for a simple three-dimensional interface. The interface studied consists of a gravity stabilized SF6-based heavy gas jet that produced a circular column with a diffuse interface into the surrounding air. The effects of density gradient (Atwood number, A), <span class="hlt">shock</span> strength (Mach number, M), and column inclination angle (theta) were examined. Concentration was measured using Planar Laser Induced Fluorescence (PLIF) of an acetone vapor tracer mixed with the heavy gas jet and illuminated by a pulsed Nd-YAG laser. <span class="hlt">Shocks</span> with Mach numbers of 1.13, 1.5, 1.7, and 2.0 were used for inclinations of 0° (planar normal <span class="hlt">shock</span> <span class="hlt">wave</span>), 20° and 30°. Columns with Atwood numbers of 0.25, 0.4, and 0.60 were tested at Mach 1.7 for inclinations of 0° and 20°. The oblique <span class="hlt">shock</span>-accelerated cylindrical interface produced a typical Richtmyer-Meshkov instability (RMI) consisting of a primary counter-rotating vortices. The streamwise extent of the vortex pair in the centerline plane (cross-section) images of the column is proportional to √A/√ M, regardless of oblique <span class="hlt">shock</span> angle for theta < 20. A heretofore unseen manifestation of Kelvin-Helmholtz (K-H) <span class="hlt">waves</span> on the upstream edge of the column appear for oblique <span class="hlt">shock</span> acceleration. The upstream edge K-H <span class="hlt">waves</span> were observed in images from a vertical plane through the center of the column. The wavelength of the upstream edge K-H <span class="hlt">waves</span> is proportional to theta/M ˙ √A. This upstream edge K-H instability (KHI) caused earlier onset of secondary instabilities in the primary RMI vortices seen in the centerline plane images. The combination of more rapid onset of secondary instabilities in the RMI and upstream edge KHI accelerated transition to turbulence and thus reduced the time to achieve well-mixed flow. Time to reach well-mixed flow was inversely related to Atwood number, and had a weak correlation with Mach number for M>1.13. Transition to</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19930093827','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19930093827"><span id="translatedtitle">Effect of surface roughness on characteristics of spherical <span class="hlt">shock</span> <span class="hlt">waves</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Huber, Paul W; Mcfarland, Donald R</p> <p>1955-01-01</p> <p>An investigation has been conducted on a small-scale test layout in which direct observation of the <span class="hlt">shock</span> <span class="hlt">wave</span> movement with time could be made in order to determine the effects of surface roughness on the characteristics of spherical <span class="hlt">shock</span> <span class="hlt">waves</span>. Data were obtained with 15-gram pentolite charges at four heights of burst, both for a smooth surface and for a surface completely covered with pyramid-shaped roughness elements. The observations resulted in determinations of <span class="hlt">shock</span> peak overpressure and Mach stem height as a function of distance for each test. Comparison of the smooth-surface data with those obtained for the extremely rough condition showed a small net effort of roughness on the <span class="hlt">shock</span> peak overpressures at the surface for all burst heights, the effect being to lower the overpressures. The effect of surface roughness on the Mach stem formation and growth was to delay the formation at the greatest charge height and to lower the height of the Mach stem for all heights.Comparison of the free-air <span class="hlt">shock</span> peak overpressures with larger scale data showed good similarity of the overpressure-distance relationships. The data did not fit a geometrical similarity parameter for the path of the triple point at different heights of burst suggested by other investigators. A simple similarity parameter (relating the horizontal distance to the theoretical point of Mach formation) was found which showed only a small influence of burst height on the path of the triple point. While the data presented provide knowledge of the effect of many surface-roughness elements on the overall <span class="hlt">shock</span> characteristics, the data do not provide insight into the details of the air-flow characteristics along the surface, nor the relative contribution of individual roughness elements to the results obtained.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFMSH12B2208B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFMSH12B2208B"><span id="translatedtitle">STEREO observations of <span class="hlt">waves</span> near the ramp region of interplanetary <span class="hlt">shocks</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Breneman, A. W.; Cattell, C. A.; Wilson, L. B., III; Kersten, K.; Goetz, K.; Paradise, A.</p> <p>2012-12-01</p> <p>The Earth's bowshock as well as interplanetary <span class="hlt">shocks</span> host a variety of mechanisms that provide for the dissipation of bulk flow energy. Wilson et al., 2007 suggested that <span class="hlt">wave</span>-particle interactions, in addition to previously suggested particle <span class="hlt">reflection</span>, may be an important part of the energy dissipation at high mach number <span class="hlt">shocks</span>. Supporting this idea, two recent papers have identified very large amplitude electrostatic <span class="hlt">waves</span> upstream of the Earth's bowshock and an interplanetary <span class="hlt">shock</span>. These <span class="hlt">waves</span> are expected to contribute significantly to particle scattering and heating. Large amplitude turbulent electrostatic waveforms (up to 40 mV/m), identified as ion acoustic <span class="hlt">waves</span>, were first observed by Hull et al., 2006 from Polar spacecraft data upstream of the Earth's bowshock during active solar wind conditions. Similar waveforms were observed on Wind by Wilson et al., 2010 (up to 100 mV/m) at a supercritical interplanetary <span class="hlt">shock</span> and were identified as electron Bernstein <span class="hlt">waves</span>. These studies were limited to two bowshock crossings and a single interplanetary <span class="hlt">shock</span>, respectively. We present a preliminary study of a much larger data set of these <span class="hlt">waves</span> from high time resolution STEREO, WIND and THEMIS burst waveform data. Over STEREO 200 burst capture electric field waveforms are seen in twelve separate groups on all four Earth swing-by orbits in 2006. <span class="hlt">Wave</span> amplitudes range from ~20 to 200 mV/m. With this dataset we will provide statistical context to the observations of the aforementioned papers and attempt to resolve the discrepancy in <span class="hlt">wave</span> identification. The results of this study will elucidate the plasma conditions under which these <span class="hlt">waves</span> are generated and constrain possible generation mechanisms. The ubiquity of these <span class="hlt">waves</span>, under a variety of solar wind conditions, suggests that they may indeed play an important role in the dissipation of energy at the bowshock. In addition, many of the waveforms show evidence of particle trap! ping suggesting that not only do</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li class="active"><span>23</span></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_23 --> <div id="page_24" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li class="active"><span>24</span></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="461"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016PhPl...23g3508Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016PhPl...23g3508Z"><span id="translatedtitle">Revisiting the thermal effect on <span class="hlt">shock</span> <span class="hlt">wave</span> propagation in weakly ionized plasmas</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhou, Qianhong; Dong, Zhiwei; Yang, Wei</p> <p>2016-07-01</p> <p>Many researchers have investigated <span class="hlt">shock</span> propagation in weakly ionized plasmas and observed the following anomalous effects: <span class="hlt">shock</span> acceleration, <span class="hlt">shock</span> recovery, <span class="hlt">shock</span> weakening, <span class="hlt">shock</span> spreading, and splitting. It was generally accepted that the thermal effect can explain most of the experimental results. However, little attention was paid to the <span class="hlt">shock</span> recovery. In this paper, the <span class="hlt">shock</span> <span class="hlt">wave</span> propagation in weakly ionized plasmas is studied by fluid simulation. It is found that the <span class="hlt">shock</span> acceleration, weakening, and splitting appear after it enters the plasma (thermal) region. The <span class="hlt">shock</span> splits into two parts right after it leaves the thermal region. The distance between the splitted <span class="hlt">shocks</span> keeps decreasing until they recover to one. This paper can explain a whole set of features of the <span class="hlt">shock</span> <span class="hlt">wave</span> propagation in weakly ionized plasmas. It is also found that both the <span class="hlt">shock</span> curvature and the splitting present the same photoacoustic deflection (PAD) signals, so they cannot be distinguished by the PAD experiments.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/21455272','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/21455272"><span id="translatedtitle">From weak discontinuities to nondissipative <span class="hlt">shock</span> <span class="hlt">waves</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Garifullin, R. N. Suleimanov, B. I.</p> <p>2010-01-15</p> <p>An analysis is presented of the effect of weak dispersion on transitions from weak to strong discontinuities in inviscid fluid dynamics. In the neighborhoods of transition points, this effect is described by simultaneous solutions to the Korteweg-de Vries equation u{sub t}'+ uu{sub x}' + u{sub xxx}' = 0 and fifth-order nonautonomous ordinary differential equations. As x{sup 2} + t{sup 2} {yields}{infinity}, the asymptotic behavior of these simultaneous solutions in the zone of undamped oscillations is given by quasi-simple <span class="hlt">wave</span> solutions to Whitham equations of the form r{sub i}(t, x) = tl{sub i} x/t{sup 2}.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1993SPIE.1801.1029T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1993SPIE.1801.1029T"><span id="translatedtitle">Application of holographic interferometric studies of underwater <span class="hlt">shock-wave</span> focusing to medicine</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Takayama, Kazuyoshi; Nagoya, H.; Obara, Tetsuro; Kuwahara, M.</p> <p>1993-01-01</p> <p>Holographic interferometric flow visualization was successfully applied to underwater <span class="hlt">shock</span> <span class="hlt">wave</span> focusing and its application to extracorporeal <span class="hlt">shock</span> <span class="hlt">wave</span> lithotripsy (ESWL). Real time diffuse holograms revealed the <span class="hlt">shock</span> <span class="hlt">wave</span> focusing process in an ellipsoidal reflector made from PMMA and double exposure holographic interferometry also clarified quantitatively the <span class="hlt">shock</span> focusing process. Disintegration of urinary tract stones and gallbladder stones was observed by high speed photogrammetry. Tissue damage associated with the ESWL treatment is discussed in some detail.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009JAP...105e4902I','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009JAP...105e4902I"><span id="translatedtitle">Terahertz <span class="hlt">reflection</span> response measurement using a phonon polariton <span class="hlt">wave</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Inoue, Hayato; Katayama, Kenji; Shen, Qing; Toyoda, Taro; Nelson, Keith A.</p> <p>2009-03-01</p> <p>We developed a new technique for the measurement of terahertz <span class="hlt">reflection</span> responses utilizing a propagating phonon polariton <span class="hlt">wave</span>. Frequency tunable phonon polariton <span class="hlt">waves</span> were generated by the recently developed continuously variable spatial frequency transient grating method [K. Katayama, H. Inoue, H. Sugiya, Q. Shen, T. Taro, and K. A. Nelson, Appl. Phys. Lett. 92, 031906 (2008)]. The phonon polariton <span class="hlt">wave</span> traveled in a ferroelectric crystal in an in-plane direction with an inclined angle of 26°, and the <span class="hlt">wave</span> <span class="hlt">reflected</span> at the crystal edge where a sample was positioned. The <span class="hlt">reflected</span> polariton <span class="hlt">wave</span> was detected by the same method as that used for the generation of the polariton <span class="hlt">waves</span>. By comparing the <span class="hlt">reflection</span> intensities in the presence and absence of the sample, <span class="hlt">reflectivity</span> of the polariton <span class="hlt">wave</span> was calculated, and the refractive index and absorption in the terahertz region were obtained.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015ExFl...56..113G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015ExFl...56..113G"><span id="translatedtitle">High-resolution PIV measurements of a transitional <span class="hlt">shock</span> <span class="hlt">wave</span>-boundary layer interaction</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Giepman, R. H. M.; Schrijer, F. F. J.; van Oudheusden, B. W.</p> <p>2015-06-01</p> <p>This study investigates the effects of boundary layer transition on an oblique <span class="hlt">shock</span> <span class="hlt">wave</span> <span class="hlt">reflection</span>. The Mach number was 1.7, the unit Reynolds number was 35 × 106 m-1, and the pressure ratio over the interaction was 1.35. Particle image velocimetry is used as the main flow diagnostics tool, supported by oil-flow and Schlieren visualizations. At these conditions, the thickness of the laminar boundary layer is only 0.2 mm, and seeding proved to be problematic as practically no seeding was recorded in the lower 40 % of the boundary layer. The top 60 % could, however, still be resolved with good accuracy and is found to be in good agreement with the compressible Blasius solution. Due to the effects of turbulent mixing, the near-wall seeding deficiency disappears when the boundary layer transitions to a turbulent state. This allowed the seeding distribution to be used as an indicator for the state of the boundary layer, permitting to obtain an approximate intermittency distribution for the boundary layer transition region. This knowledge was then used for positioning the oblique <span class="hlt">shock</span> <span class="hlt">wave</span> in the laminar, transitional (50 % intermittency) or turbulent region of the boundary layer. Separation is only recorded for the laminar and transitional interactions. For the laminar interaction, a large separation bubble is found, with a streamwise length of 96. The incoming boundary layer is lifted over the separation bubble and remains in a laminar state up to the impingement point of the <span class="hlt">shock</span> <span class="hlt">wave</span>. After the <span class="hlt">shock</span>, transition starts and a turbulent profile is reached approximately 80-90 downstream of the <span class="hlt">shock</span>. Under the same <span class="hlt">shock</span> conditions, the transitional interaction displays a smaller separation bubble (43), and transition is found to be accelerated over the separation bubble.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/5415969','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/5415969"><span id="translatedtitle">Temperature kinetics during <span class="hlt">shock-wave</span> consolidation of metallic powders</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Schwarz, R.B.; Kasiraj, P.; Vreeland, T. Jr.</p> <p>1985-01-01</p> <p>Powders (60 ..mu..m diam) of constantan and pure copper were compressed statically into cylindrical greens (20.3 mm diam, 5.3 mm long) with a flat interface separating the two powders. A 20-mm propellant gun was used to accelerate a flyer of Lexan, copper, or aluminum, and generate in the green a <span class="hlt">shock</span> <span class="hlt">wave</span> with front parallel to the Cu/constantan interface. The voltages between opposite ends of the greens were measured as a function of time and for <span class="hlt">shock</span> pressures between 1.3 and 9.4 GPa. When the <span class="hlt">shock</span> <span class="hlt">wave</span> arrives at the Cu/constantan interface, the voltage signal shows an abrupt increase, which lasts between 45 and 81 ns and leads to a peak temperature T/sub p/. After this, the hotter and cooler parts of the compact equilibrate and the temperature decreases to a value T/sub h/. With increasing <span class="hlt">shock</span> pressure, T/sub h/ increases from 425 to 1215 K. The measurements of T/sub h/ are in excellent agreement with the temperatures calculated from the measured flyer velocity, the Hugoniot for copper powder, and thermodynamic data for the flyer and powders.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1993JAP....73..673D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1993JAP....73..673D"><span id="translatedtitle">Strength of titanium diboride under <span class="hlt">shock</span> <span class="hlt">wave</span> loading</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dandekar, Dattatraya P.; Benfanti, Daniel C.</p> <p>1993-01-01</p> <p>Strength of TiB2 under plane <span class="hlt">shock</span> <span class="hlt">wave</span> loading is assessed in terms of its spall threshold and the shear stress sustained by it under <span class="hlt">shock</span> compression to 60 GPa. The results of experiments support the thesis that the observed cusp in TiB2 at 4.5-7.0 GPa is of mechanical nature and its effect is to decrease the spall threshold values at stresses above the cusp but below the accepted Hugoniot elastic limit (HEL) value of 13-17 GPa. A comparison of <span class="hlt">shock</span> Hugoniot data on two different TiB2 obtained from Grady [Dynamic Material Properties of Armor Ceramics, Sandia Laboratories, SAND 91-0147. UC-704 (1991)] and the adiabats constructed from high pressure ultrasonic <span class="hlt">wave</span> velocity measurements show that these materials sustain increasing shear stresses with increasing values of <span class="hlt">shock</span> stress. For example, results of data analysis on the denser TiB2 show that it sustains around three times the shear stress at 60 GPa than at its HEL, i.e., 17 GPa.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1044133','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1044133"><span id="translatedtitle">Simulation and Analysis of Converging <span class="hlt">Shock</span> <span class="hlt">Wave</span> Test Problems</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Ramsey, Scott D.; Shashkov, Mikhail J.</p> <p>2012-06-21</p> <p>Results and analysis pertaining to the simulation of the Guderley converging <span class="hlt">shock</span> <span class="hlt">wave</span> test problem (and associated code verification hydrodynamics test problems involving converging <span class="hlt">shock</span> <span class="hlt">waves</span>) in the LANL ASC radiation-hydrodynamics code xRAGE are presented. One-dimensional (1D) spherical and two-dimensional (2D) axi-symmetric geometric setups are utilized and evaluated in this study, as is an instantiation of the xRAGE adaptive mesh refinement capability. For the 2D simulations, a 'Surrogate Guderley' test problem is developed and used to obviate subtleties inherent to the true Guderley solution's initialization on a square grid, while still maintaining a high degree of fidelity to the original problem, and minimally straining the general credibility of associated analysis and conclusions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4095641','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4095641"><span id="translatedtitle">Extracorporeal <span class="hlt">shock</span> <span class="hlt">wave</span> therapy in periodontics: A new paradigm</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Venkatesh Prabhuji, Munivenkatappa Lakshmaiah; Khaleelahmed, Shaeesta; Vasudevalu, Sujatha; Vinodhini, K.</p> <p>2014-01-01</p> <p>The quest for exploring new frontiers in the field of medical science for efficient and improved treatment modalities has always been on a rise. Extracorporeal <span class="hlt">shock</span> <span class="hlt">wave</span> therapy (ESWT) has been enormously used in medical practice, principally, for the management of urolithiasis, cholelithiasis and also in various orthopedic and musculoskeletal disorders. The efficacy of ESWT in the stimulation of osteoblasts, fibroblasts, induction of neovascularization and increased expression of bone morphogenic proteins has been well documented in the literature. However, dentistry is no exception to this trend. The present article enlightens the various applications of ESWT in the field of dentistry and explores its prospective applications in the field of periodontics, and the possibility of incorporating the beneficial properties of <span class="hlt">shock</span> <span class="hlt">waves</span> in improving the treatment outcome. PMID:25024562</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1982JFM...120..451V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1982JFM...120..451V"><span id="translatedtitle">The converging <span class="hlt">shock</span> <span class="hlt">wave</span> from a spherical or cylindrical piston</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>van Dyke, M.; Guttmann, A. J.</p> <p>1982-07-01</p> <p>A spherical or cylindrical cavity containing quiescent gas begins to contract at high constant radial speed, driving an axisymmetric <span class="hlt">shock</span> <span class="hlt">wave</span> inward to collapse at the center. We analyze the flow field by expanding the solution in powers of time, and calculate 40 terms by delegating the arithmetic to a computer. Analysis of the series for the radius of the <span class="hlt">shock</span> <span class="hlt">wave</span> confirms Guderley's local self-similar solution for the focusing, including recent refined values for his similarity exponent, and yields higher terms in his local expansion. In the range of adiabatic exponent where the Guderley solution has been shown not to be unique we find, in accord with a conjecture of Gel'fand, that the smallest admissible similarity exponent is realized.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/108177','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/108177"><span id="translatedtitle">Sonoluminescence, <span class="hlt">shock</span> <span class="hlt">waves</span>, and micro-thermonuclear fusion</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Moss, W.C.; Clarke, D.B.; White, J.W.; Young, D.A.</p> <p>1995-08-01</p> <p>We have performed numerical hydrodynamic simulations of the growth and collapse of a sonoluminescing bubble in a liquid. Our calculations show that spherically converging <span class="hlt">shock</span> <span class="hlt">waves</span> are generated during the collapse of the bubble. The combination of the <span class="hlt">shock</span> <span class="hlt">waves</span> and a realistic equation of state for the gas in the bubble provides an explanation for the measured picosecond optical pulse widths and indicates that the temperatures near the center of the bubble may exceed 3O eV. This leads naturally to speculation about obtaining micro-thermonuclear fusion in a bubble filled with deuterium (D{sub 2}) gas. Consequently, we performed numerical simulations of the collapse of a D{sub 2} bubble in D{sub 2}0. A pressure spike added to the periodic driving amplitude creates temperatures that may be sufficient to generate a very small, but measurable number of thermonuclear D-D fusion reactions in the bubble.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22043623','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22043623"><span id="translatedtitle">Tracking <span class="hlt">shocked</span> dust: State estimation for a complex plasma during a <span class="hlt">shock</span> <span class="hlt">wave</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Oxtoby, Neil P.; Ralph, Jason F.; Durniak, Celine; Samsonov, Dmitry</p> <p>2012-01-15</p> <p>We consider a two-dimensional complex (dusty) plasma crystal excited by an electrostatically-induced <span class="hlt">shock</span> <span class="hlt">wave</span>. Dust particle kinematics in such a system are usually determined using particle tracking velocimetry. In this work we present a particle tracking algorithm which determines the dust particle kinematics with significantly higher accuracy than particle tracking velocimetry. The algorithm uses multiple extended Kalman filters to estimate the particle states and an interacting multiple model to assign probabilities to the different filters. This enables the determination of relevant physical properties of the dust, such as kinetic energy and kinetic temperature, with high precision. We use a Hugoniot <span class="hlt">shock</span>-jump relation to calculate a pressure-volume diagram from the <span class="hlt">shocked</span> dust kinematics. Calculation of the full pressure-volume diagram was possible with our tracking algorithm, but not with particle tracking velocimetry.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/21797491','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/21797491"><span id="translatedtitle"><span class="hlt">Shock</span> <span class="hlt">waves</span> in Stokes flows down an inclined plate.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Benilov, E S; Lapin, V N</p> <p>2011-06-01</p> <p>We consider a viscous flow on an inclined plate, such that the liquid's depth far upstream is larger than that far downstream, resulting in a "smoothed-<span class="hlt">shock</span> <span class="hlt">wave</span>" steadily propagating downstream. Our numerical simulations show that in a large section of the problem's parameter space all initial conditions overturn (i.e., the liquid's surface becomes vertical at some point) and thus no steady solution exists. The overturning can only be stopped by a sufficiently strong surface tension. PMID:21797491</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015APS..DPPUP2052J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015APS..DPPUP2052J"><span id="translatedtitle">Flow induced dust acoustic <span class="hlt">shock</span> <span class="hlt">waves</span> in a complex plasma</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jaiswal, Surabhi; Bandyopadhyay, Pintu; Sen, Abhijit</p> <p>2015-11-01</p> <p>We report on experimental observations of particle flow induced large amplitude <span class="hlt">shock</span> <span class="hlt">waves</span> in a dusty plasma. These dust acoustic <span class="hlt">shocks</span> (DAS) are observed for strongly supersonic flows and have been studied in a U-shaped Dusty Plasma Experimental (DPEx) device for charged kaolin dust in a background of Argon plasma. The strong flow of the dust fluid is induced by adjusting the pumping speed and neutral gas flow into the device. An isolated copper wire mounted on the cathode acts as a potential barrier to the flow of dust particles. A sudden change of the dust density near the potential hill is used to trigger the onset of high velocity dust acoustic <span class="hlt">shocks</span>. The dynamics of the <span class="hlt">shocks</span> are captured by fast video pictures of the structures that are illuminated by a laser sheet beam. The physical characteristics of the <span class="hlt">shock</span> are delineated from a parametric scan of their dynamical properties over a range of plasma parameters and flow speeds. Details of these observations and a physical explanation based on model calculations will be presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010cosp...38.1806C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010cosp...38.1806C"><span id="translatedtitle">Coronal <span class="hlt">Shock</span> <span class="hlt">Waves</span> and Solar Energetic Particle Events</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cliver, Edward</p> <p></p> <p>Recent evidence supports the view first expressed by Wild, Smerd, and Weiss in 1963 that large solar energetic particle (SEP) events are a consequence of <span class="hlt">shock</span> <span class="hlt">waves</span> manifested by radio type II bursts. Following Tylka et al. (ApJ 625, 474, 2005), our picture of SEP acceleration at <span class="hlt">shocks</span> now includes the effects of variable seed particle population and <span class="hlt">shock</span> geometry. By taking these factors into account, Tylka and Lee (ApJ 646, 1319, 2006; see also Sandroos Vainio, ApJ 662, L127, 2007; AA 507, L21, 2009) were able to account for the charge-to-mass variability in high-Z ions first reported by Breneman and Stone in 1985. Recent studies of electron-to-proton ratios, both in interplanetary space (Cliver Ling, ApJ 658, 1349, 2007; Dietrich et al., in preparation, 2010) and in gamma-ray-line events (Shih et al., ApJ 698, L152, 2009), also support the view that large SEP events originate in coronal <span class="hlt">shocks</span> and not in solar flares. Concurrent with the above developments, there is growing evidence that coronal <span class="hlt">shocks</span> are driven by coronal mass ejections rather than by flare pressure pulses.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/5182528','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/5182528"><span id="translatedtitle"><span class="hlt">Shock-wave</span> response of titanium subhydride-potassium perchlorate</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Sheffield, S.A.; Schwa, A.C.</p> <p>1982-01-01</p> <p><span class="hlt">Shock</span> initiation of pyrotechnic materials is becoming increasingly more interesting since this concept is now used in weapon component design. In this study we have performed several types of <span class="hlt">shock</span> initiation experiments on TiH/sub 0/ /sub 65//KC10/sub 4/ to better understand its <span class="hlt">shock</span> response and the process by which it undergoes reaction. Gas gun impact experiments have led to new unreacted Hugoniot information which was used, along with earlier reported data, to construct an equation of state for the unreacted material. Particle velocity records of the projectile impact interface and the <span class="hlt">shock</span> transmitted through the sample show little evidence of reaction in the first microsecond even for 6 GPa <span class="hlt">shocks</span>. Peculiarities in the waveforms at later times suggest some evidence of reaction although the experiments do not remain strictly one-dimensional long enough to make definite statements. Flyer plate initiated compacts indicate a short input pulse is rapidly attenuated but the material is initiated and a combustion <span class="hlt">wave</span> propagates through the compact at velocities of about 0.4 to 0.7 km/s.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/pages/biblio/1295510-negative-pressures-spallation-water-drops-subjected-nanosecond-shock-waves','SCIGOV-DOEP'); return false;" href="http://www.osti.gov/pages/biblio/1295510-negative-pressures-spallation-water-drops-subjected-nanosecond-shock-waves"><span id="translatedtitle">Negative pressures and spallation in water drops subjected to nanosecond <span class="hlt">shock</span> <span class="hlt">waves</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/pages">DOE PAGESBeta</a></p> <p>Stan, Claudiu A.; Willmott, Philip R.; Stone, Howard A.; Koglin, Jason E.; Liang, Mengning; Aquila, Andrew L.; Robinson, Joseph S.; Gumerlock, Karl L.; Blaj, Gabriel; Sierra, Raymond G.; et al</p> <p>2016-05-16</p> <p>Most experimental studies of cavitation in liquid water at negative pressures reported cavitation at tensions significantly smaller than those expected for homogeneous nucleation, suggesting that achievable tensions are limited by heterogeneous cavitation. We generated tension pulses with nanosecond rise times in water by <span class="hlt">reflecting</span> cylindrical <span class="hlt">shock</span> <span class="hlt">waves</span>, produced by X-ray laser pulses, at the internal surface of drops of water. Depending on the X-ray pulse energy, a range of cavitation phenomena occurred, including the rupture and detachment, or spallation, of thin liquid layers at the surface of the drop. When spallation occurred, we evaluated that negative pressures below –100 MPamore » were reached in the drops. As a result, we model the negative pressures from <span class="hlt">shock</span> <span class="hlt">reflection</span> experiments using a nucleation-and-growth model that explains how rapid decompression could outrun heterogeneous cavitation in water, and enable the study of stretched water close to homogeneous cavitation pressures.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/27182751','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27182751"><span id="translatedtitle">Negative Pressures and Spallation in Water Drops Subjected to Nanosecond <span class="hlt">Shock</span> <span class="hlt">Waves</span>.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Stan, Claudiu A; Willmott, Philip R; Stone, Howard A; Koglin, Jason E; Liang, Mengning; Aquila, Andrew L; Robinson, Joseph S; Gumerlock, Karl L; Blaj, Gabriel; Sierra, Raymond G; Boutet, Sébastien; Guillet, Serge A H; Curtis, Robin H; Vetter, Sharon L; Loos, Henrik; Turner, James L; Decker, Franz-Josef</p> <p>2016-06-01</p> <p>Most experimental studies of cavitation in liquid water at negative pressures reported cavitation at tensions significantly smaller than those expected for homogeneous nucleation, suggesting that achievable tensions are limited by heterogeneous cavitation. We generated tension pulses with nanosecond rise times in water by <span class="hlt">reflecting</span> cylindrical <span class="hlt">shock</span> <span class="hlt">waves</span>, produced by X-ray laser pulses, at the internal surface of drops of water. Depending on the X-ray pulse energy, a range of cavitation phenomena occurred, including the rupture and detachment, or spallation, of thin liquid layers at the surface of the drop. When spallation occurred, we evaluated that negative pressures below -100 MPa were reached in the drops. We model the negative pressures from <span class="hlt">shock</span> <span class="hlt">reflection</span> experiments using a nucleation-and-growth model that explains how rapid decompression could outrun heterogeneous cavitation in water, and enable the study of stretched water close to homogeneous cavitation pressures. PMID:27182751</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26687540','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26687540"><span id="translatedtitle">Modeling secondary accidents identified by traffic <span class="hlt">shock</span> <span class="hlt">waves</span>.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Junhua, Wang; Boya, Liu; Lanfang, Zhang; Ragland, David R</p> <p>2016-02-01</p> <p>The high potential for occurrence and the negative consequences of secondary accidents make them an issue of great concern affecting freeway safety. Using accident records from a three-year period together with California interstate freeway loop data, a dynamic method for more accurate classification based on the traffic <span class="hlt">shock</span> <span class="hlt">wave</span> detecting method was used to identify secondary accidents. Spatio-temporal gaps between the primary and secondary accident were proven be fit via a mixture of Weibull and normal distribution. A logistic regression model was developed to investigate major factors contributing to secondary accident occurrence. Traffic <span class="hlt">shock</span> <span class="hlt">wave</span> speed and volume at the occurrence of a primary accident were explicitly considered in the model, as a secondary accident is defined as an accident that occurs within the spatio-temporal impact scope of the primary accident. Results show that the <span class="hlt">shock</span> <span class="hlt">waves</span> originating in the wake of a primary accident have a more significant impact on the likelihood of a secondary accident occurrence than the effects of traffic volume. Primary accidents with long durations can significantly increase the possibility of secondary accidents. Unsafe speed and weather are other factors contributing to secondary crash occurrence. It is strongly suggested that when police or rescue personnel arrive at the scene of an accident, they should not suddenly block, decrease, or unblock the traffic flow, but instead endeavor to control traffic in a smooth and controlled manner. Also it is important to reduce accident processing time to reduce the risk of secondary accident. PMID:26687540</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/21307276','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/21307276"><span id="translatedtitle">Needleless vaccine delivery using micro-<span class="hlt">shock</span> <span class="hlt">waves</span>.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Jagadeesh, Gopalan; Prakash, G Divya; Rakesh, S G; Allam, Uday Sankar; Krishna, M Gopala; Eswarappa, Sandeepa M; Chakravortty, Dipshikha</p> <p>2011-04-01</p> <p><span class="hlt">Shock</span> <span class="hlt">waves</span> are one of the most efficient mechanisms of energy dissipation observed in nature. In this study, utilizing the instantaneous mechanical impulse generated behind a micro-<span class="hlt">shock</span> <span class="hlt">wave</span> during a controlled explosion, a novel nonintrusive needleless vaccine delivery system has been developed. It is well-known that antigens in the epidermis are efficiently presented by resident Langerhans cells, eliciting the requisite immune response, making them a good target for vaccine delivery. Unfortunately, needle-free devices for epidermal delivery have inherent problems from the perspective of the safety and comfort of the patient. The penetration depth of less than 100 μm in the skin can elicit higher immune response without any pain. Here we show the efficient utilization of our needleless device (that uses micro-<span class="hlt">shock</span> <span class="hlt">waves</span>) for vaccination. The production of liquid jet was confirmed by high-speed microscopy, and the penetration in acrylamide gel and mouse skin was observed by confocal microscopy. Salmonella enterica serovar Typhimurium vaccine strain pmrG-HM-D (DV-STM-07) was delivered using our device in the murine salmonellosis model, and the effectiveness of the delivery system for vaccination was compared with other routes of vaccination. Vaccination using our device elicits better protection and an IgG response even at a lower vaccine dose (10-fold less) compared to other routes of vaccination. We anticipate that our novel method can be utilized for effective, cheap, and safe vaccination in the near future. PMID:21307276</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li class="active"><span>24</span></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_24 --> <div id="page_25" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li class="active"><span>25</span></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="481"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010SCPMA..53..279W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010SCPMA..53..279W"><span id="translatedtitle">A study on compressive <span class="hlt">shock</span> <span class="hlt">wave</span> propagation in metallic foams</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wang, Zhihua; Zhang, Yifen; Ren, Huilan; Zhao, Longmao</p> <p>2010-02-01</p> <p>Metallic foam can dissipate a large amount of energy due to its relatively long stress plateau, which makes it widely applicable in the design of structural crashworthiness. However, in some experimental studies, stress enhancement has been observed when the specimens are subjected to intense impact loads, leading to severe damage to the objects being protected. This paper studies this phenomenon on a 2D mass-spring-bar model. With the model, a constitutive relationship of metal foam and corresponding loading and unloading criteria are presented; a nonlinear kinematics equilibrium equation is derived, where an explicit integration algorithm is used to calculate the characteristic of the compressive <span class="hlt">shock</span> <span class="hlt">wave</span> propagation within the metallic foam; the effect of heterogeneous distribution of foam microstructures on the <span class="hlt">shock</span> <span class="hlt">wave</span> features is also included. The results reveal that under low impact pulses, considerable energy is dissipated during the progressive collapse of foam cells, which then reduces the crush of objects. When the pulse is sufficiently high, on the other hand, stress enhancement may take place, especially in the heterogeneous foams, where high peak stresses usually occur. The characteristics of compressive <span class="hlt">shock</span> <span class="hlt">wave</span> propagation in the foam and the magnitude and location of the peak stress produced are strongly dependent on the mechanical properties of the foam material, amplitude and period of the pulse, as well as the homogeneity of the microstructures. This research provides valuable insight into the reliability of the metallic foams used as a protective structure.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016PhPl...23e2706V&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016PhPl...23e2706V&link_type=ABSTRACT"><span id="translatedtitle">Stability of stagnation via an expanding accretion <span class="hlt">shock</span> <span class="hlt">wave</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Velikovich, A. L.; Murakami, M.; Taylor, B. D.; Giuliani, J. L.; Zalesak, S. T.; Iwamoto, Y.</p> <p>2016-05-01</p> <p>Stagnation of a cold plasma streaming to the center or axis of symmetry via an expanding accretion <span class="hlt">shock</span> <span class="hlt">wave</span> is ubiquitous in inertial confinement fusion (ICF) and high-energy-density plasma physics, the examples ranging from plasma flows in x-ray-generating Z pinches [Maron et al., Phys. Rev. Lett. 111, 035001 (2013)] to the experiments in support of the recently suggested concept of impact ignition in ICF [Azechi et al., Phys. Rev. Lett. 102, 235002 (2009); Murakami et al., Nucl. Fusion 54, 054007 (2014)]. Some experimental evidence indicates that stagnation via an expanding <span class="hlt">shock</span> <span class="hlt">wave</span> is stable, but its stability has never been studied theoretically. We present such analysis for the stagnation that does not involve a rarefaction <span class="hlt">wave</span> behind the expanding <span class="hlt">shock</span> front and is described by the classic ideal-gas Noh solution in spherical and cylindrical geometry. In either case, the stagnated flow has been demonstrated to be stable, initial perturbations exhibiting a power-law, oscillatory or monotonic, decay with time for all the eigenmodes. This conclusion has been supported by our simulations done both on a Cartesian grid and on a curvilinear grid in spherical coordinates. Dispersion equation determining the eigenvalues of the problem and explicit formulas for the eigenfunction profiles corresponding to these eigenvalues are presented, making it possible to use the theory for hydrocode verification in two and three dimensions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2768123','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2768123"><span id="translatedtitle">Assessment of <span class="hlt">shock</span> <span class="hlt">wave</span> lithotripters via cavitation potential</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Iloreta, Jonathan I.; Zhou, Yufeng; Sankin, Georgy N.; Zhong, Pei; Szeri, Andrew J.</p> <p>2008-01-01</p> <p>A method to characterize <span class="hlt">shock</span> <span class="hlt">wave</span> lithotripters by examining the potential for cavitation associated with the lithotripter <span class="hlt">shock</span> <span class="hlt">wave</span> (LSW) has been developed. The method uses the maximum radius achieved by a bubble subjected to a LSW as a representation of the cavitation potential for that region in the lithotripter. It is found that the maximum radius is determined by the work done on a bubble by the LSW. The method is used to characterize two reflectors: an ellipsoidal reflector and an ellipsoidal reflector with an insert. The results show that the use of an insert reduced the −6 dB volume (with respect to peak positive pressure) from 1.6 to 0.4 cm3, the −6 dB volume (with respect to peak negative pressure) from 14.5 to 8.3 cm3, and reduced the volume characterized by high cavitation potential (i.e., regions characterized by bubbles with radii larger than 429 µm) from 103 to 26 cm3. Thus, the insert is an effective way to localize the potentially damaging effects of <span class="hlt">shock</span> <span class="hlt">wave</span> lithotripsy, and suggests an approach to optimize the shape of the reflector. PMID:19865493</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2012AIPC.1481...76D&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2012AIPC.1481...76D&link_type=ABSTRACT"><span id="translatedtitle">Optically triggered solid state driver for <span class="hlt">shock</span> <span class="hlt">wave</span> therapy</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Duryea, Alexander P.; Roberts, William W.; Cain, Charles A.; Hall, Timothy L.</p> <p>2012-10-01</p> <p><span class="hlt">Shock</span> <span class="hlt">wave</span> lithotripsy (SWL) represents one of several first-line therapies for the treatment of stones located in the kidneys and ureters. Additional applications for <span class="hlt">shock</span> <span class="hlt">wave</span> therapy are also under exploration, including non-urinary calculi, orthopedics, and neovascularization. Except for the elimination of a large water bath in which the treatment is performed, current procedures remain largely unchanged, with one of the original commercial devices (the Dornier HM3) still considered a gold standard for comparison. To accelerate research in this area, Coleman, et al. published an experimental electrohydraulic <span class="hlt">shock</span> <span class="hlt">wave</span> generator capable of simulating the acoustic field generated by the HM3. We propose a further update of this system, replacing the triggered spark gap with an optically triggered solid state switch. The new system has better reliability, a wider operating range, and reduced timing jitter allowing synchronization with additional acoustic sources under exploration for improving efficacy and reducing injury. Originally designed for exciting electrohydraulic spark electrodes, the system can also be adapted for driving piezoelectric and electromagnetic sources.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3745501','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3745501"><span id="translatedtitle">A heuristic model of stone comminution in <span class="hlt">shock</span> <span class="hlt">wave</span> lithotripsy</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Smith, Nathan B.; Zhong, Pei</p> <p>2013-01-01</p> <p>A heuristic model is presented to describe the overall progression of stone comminution in <span class="hlt">shock</span> <span class="hlt">wave</span> lithotripsy (SWL), accounting for the effects of <span class="hlt">shock</span> <span class="hlt">wave</span> dose and the average peak pressure, P+(avg), incident on the stone during the treatment. The model is developed through adaptation of the Weibull theory for brittle fracture, incorporating threshold values in dose and P+(avg) that are required to initiate fragmentation. The model is validated against experimental data of stone comminution from two stone types (hard and soft BegoStone) obtained at various positions in lithotripter fields produced by two <span class="hlt">shock</span> <span class="hlt">wave</span> sources of different beam width and pulse profile both in water and in 1,3-butanediol (which suppresses cavitation). Subsequently, the model is used to assess the performance of a newly developed acoustic lens for electromagnetic lithotripters in comparison with its original counterpart both under static and simulated respiratory motion. The results have demonstrated the predictive value of this heuristic model in elucidating the physical basis for improved performance of the new lens. The model also provides a rationale for the selection of SWL treatment protocols to achieve effective stone comminution without elevating the risk of tissue injury. PMID:23927195</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3122580','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3122580"><span id="translatedtitle">Needleless Vaccine Delivery Using Micro-<span class="hlt">Shock</span> <span class="hlt">Waves</span> ▿ †</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Jagadeesh, Gopalan; Prakash, G. Divya; Rakesh, S. G.; Allam, Uday Sankar; Krishna, M. Gopala; Eswarappa, Sandeepa M.; Chakravortty, Dipshikha</p> <p>2011-01-01</p> <p><span class="hlt">Shock</span> <span class="hlt">waves</span> are one of the most efficient mechanisms of energy dissipation observed in nature. In this study, utilizing the instantaneous mechanical impulse generated behind a micro-<span class="hlt">shock</span> <span class="hlt">wave</span> during a controlled explosion, a novel nonintrusive needleless vaccine delivery system has been developed. It is well-known that antigens in the epidermis are efficiently presented by resident Langerhans cells, eliciting the requisite immune response, making them a good target for vaccine delivery. Unfortunately, needle-free devices for epidermal delivery have inherent problems from the perspective of the safety and comfort of the patient. The penetration depth of less than 100 μm in the skin can elicit higher immune response without any pain. Here we show the efficient utilization of our needleless device (that uses micro-<span class="hlt">shock</span> <span class="hlt">waves</span>) for vaccination. The production of liquid jet was confirmed by high-speed microscopy, and the penetration in acrylamide gel and mouse skin was observed by confocal microscopy. Salmonella enterica serovar Typhimurium vaccine strain pmrG-HM-D (DV-STM-07) was delivered using our device in the murine salmonellosis model, and the effectiveness of the delivery system for vaccination was compared with other routes of vaccination. Vaccination using our device elicits better protection and an IgG response even at a lower vaccine dose (10-fold less) compared to other routes of vaccination. We anticipate that our novel method can be utilized for effective, cheap, and safe vaccination in the near future. PMID:21307276</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19920069674&hterms=downstream&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Ddownstream','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19920069674&hterms=downstream&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Ddownstream"><span id="translatedtitle">A simulation study of multiple ion <span class="hlt">wave</span> generation downstream of low Mach number quasiperpendicular <span class="hlt">shocks</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Motschmann, Uwe; Raeder, Joachim</p> <p>1992-01-01</p> <p>The behavior of minor ions just downstream of a low Mach number quasi-perpendicular <span class="hlt">shock</span> is investigated both theoretically and by computer simulations. Because all ions see the same cross <span class="hlt">shock</span> electric field their deceleration depends on their charge to mass ratio, yielding different downstream velocities. It is shown that these differences in velocity can lead to coherent <span class="hlt">wave</span> structures in the downstream region of quasi-perpendicular <span class="hlt">shocks</span> with a narrow transition layer. These <span class="hlt">waves</span> are shown to be multi ion hybrid <span class="hlt">waves</span> in contrast to mirror <span class="hlt">waves</span> and ion cyclotron <span class="hlt">waves</span>. Under favorable conditions these <span class="hlt">waves</span> should be observable both at interplanetary <span class="hlt">shocks</span> and at planetary bowshocks.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012PhRvB..85a2102G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012PhRvB..85a2102G"><span id="translatedtitle">Anomalous and negative <span class="hlt">reflection</span> of Lamb <span class="hlt">waves</span> in mode conversion</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Germano, M.; Alippi, A.; Bettucci, A.; Mancuso, G.</p> <p>2012-01-01</p> <p>Mode conversion is an important feature of <span class="hlt">wave</span> propagation used in ultrasonic nondestructive testing with Lamb <span class="hlt">waves</span>. When a <span class="hlt">wave</span> packet with a given central frequency, and a correspondent central wavenumber, impinges on the free edge of a plate, the <span class="hlt">reflected</span> <span class="hlt">wave</span> generally is a weighed combination of all the possible modes compatible with the given frequency. Under particular conditions, only one <span class="hlt">wave</span> packet is <span class="hlt">reflected</span> with a distinct central wavenumber compared to the incident one. In such a case, according to Snell's law, the <span class="hlt">reflection</span> angle is different from the incident one (anomalous <span class="hlt">reflection</span>). In this article, experimental results are presented on anomalous <span class="hlt">reflection</span> on a free edge of a thin plate of a Lamb <span class="hlt">wave</span> packet; moreover, experimental results are reported on a Lamb <span class="hlt">wave</span> packet that is <span class="hlt">reflected</span> at an angle lying on the same side, with respect to the normal direction, of the impinging <span class="hlt">wave</span> (negative <span class="hlt">reflection</span>). Negative <span class="hlt">reflection</span> of Lamb <span class="hlt">waves</span> has been obtained through mode conversion taking place at the free edge of a thin plate of constant thickness: More precisely, a symmetric S1 Lamb mode has been converted into the same mode but with phase velocity antiparallel to group velocity, so obtaining the so-called backward-propagating Lamb <span class="hlt">wave</span> packet.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19950024161','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19950024161"><span id="translatedtitle">On <span class="hlt">reflection</span> of Alfven <span class="hlt">waves</span> in the solar wind</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Krogulec, M.; Musielak, Z. E.; Suess, S. T.; Moore, R. L.; Nerney, S. F.</p> <p>1993-01-01</p> <p>We have revisited the problem of propagation of toroidal and linear Alfven <span class="hlt">waves</span> formulated by Heinemann and Olbert (1980) to compare WKB and non-WKB <span class="hlt">waves</span> and their effects on the solar wind. They considered two solar wind models and showed that <span class="hlt">reflection</span> is important for Alfven <span class="hlt">waves</span> with periods of the order of one day and longer, and that non-WKB Alfven <span class="hlt">waves</span> are no more effective in accelerating the solar wind than WKB <span class="hlt">waves</span>. There are several recently published papers which seem to indicate that Alfven <span class="hlt">waves</span> with periods of the order of several minutes should be treated as non-WKB <span class="hlt">waves</span> and that these non-WKB <span class="hlt">waves</span> exert a stronger acceleration force than WKB <span class="hlt">waves</span>. The purpose of this paper is to study the origin of these discrepancies by performing parametric studies of the behavior of the <span class="hlt">waves</span> under a variety of different conditions. In addition, we want to investigate two problems that have not been addressed by Heinemann and Olbert, namely, calculate the efficiency of Alfven <span class="hlt">wave</span> <span class="hlt">reflection</span> by using the <span class="hlt">reflection</span> coefficient and identify the region of strongest <span class="hlt">wave</span> <span class="hlt">reflection</span> in different wind models. To achieve these goals, we investigated the influence of temperature, electron density distribution, wind velocity and magnetic field strength on the <span class="hlt">waves</span>. The obtained results clearly demonstrate that Alfven <span class="hlt">wave</span> <span class="hlt">reflection</span> is strongly model dependent and that the strongest <span class="hlt">reflection</span> can be expected in models with the base temperatures higher than 10(exp 6) K and with the base densities lower than 7 x 10(exp 7) cm(exp -3). In these models as well as in the models with lower temperatures and higher densities, Alfven <span class="hlt">waves</span> with periods as short as several minutes have negligible <span class="hlt">reflection</span> so that they can be treated as WKB <span class="hlt">waves</span>; however, for Alfven <span class="hlt">waves</span> with periods of the order of one hour or longer <span class="hlt">reflection</span> is significant, requiring a non-WKB treatment. We also show that non-WKB, linear Alfven <span class="hlt">waves</span> are always less effective in accelerating the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1810690M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1810690M"><span id="translatedtitle">Unstable whistlers and Bernstein <span class="hlt">waves</span> within the front of supercritical perpendicular <span class="hlt">shocks</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Muschietti, Laurent; Lembege, Bertrand</p> <p>2016-04-01</p> <p>In supercritical <span class="hlt">shocks</span> a significant fraction of ions is <span class="hlt">reflected</span> at the steep <span class="hlt">shock</span> ramp and carries a considerable amount of energy. The existence of <span class="hlt">reflected</span> ions enables streaming instabilities to develop which are excited by the relative drifts between the populations of incoming ions, <span class="hlt">reflected</span> ions, and electrons. The processes are fundamental to the transformation of directed kinetic energy into thermal energy, a tenet of <span class="hlt">shock</span> physics. We model the particle distributions as a broad electron population and two ion populations, namely a core and a beam (representing the <span class="hlt">reflected</span> ions) in order to investigate the kinetic instabilities possible under various <span class="hlt">wave</span> propagation angles. Recently, assuming the ion beam is directed along the <span class="hlt">shock</span> normal at 90° to the magnetic field Bo, we analyzed the linear dispersion properties by computing the full electromagnetic dielectric tensor [Muschietti and Lembege, AGU Fall meeting 2015]. Three types of <span class="hlt">waves</span> were shown to be unstable: (1) Oblique whistlers with wavelengths about the ion inertia length which propagate toward upstream at angles about 50° to the magnetic field. Frequencies are a few times the lower-hybrid. The <span class="hlt">waves</span> share many similarities to the obliquely propagating whistlers measured in detail by Polar [Hull et al., JGR 117, 2012]. (2) Quasi-perpendicular whistlers with wavelength covering a fraction of the electron inertia length which propagate toward downstream at angles larger than 80° to Bo. Frequencies are close to the lower-hybrid. (3) Bernstein <span class="hlt">waves</span> with wavelengths close to the electron gyroradius which propagate toward upstream at angles within 5° of perpendicular to the magnetic field. Frequencies are close to the electron cyclotron. The <span class="hlt">waves</span> have similarities to those reported by Wind and Stereo [Breneman et al., JGR 118, 2013; Wilson et al., JGR 115, 2010]. We will present electromagnetic 1D3V PIC simulations with predetermined propagation angles which illustrate the three types</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19880066210&hterms=earth+frequencies&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dearth%2Bfrequencies','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19880066210&hterms=earth+frequencies&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dearth%2Bfrequencies"><span id="translatedtitle">Plasma <span class="hlt">waves</span> in the range of the lower hybrid frequency - ISEE 1 and 2 observations at the earth's bow <span class="hlt">shock</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Mellott, M. M.; Greenstadt, E. W.</p> <p>1988-01-01</p> <p>This report presents a characterization of plasma <span class="hlt">wave</span> noise in the range of the lower hybrid frequency associated with 65 crossings of earth's bow <span class="hlt">shock</span> observed by the ISEE 1 and 2 satellites. <span class="hlt">Wave</span> growth generally becomes detectable at the upstream edge of the <span class="hlt">shock</span> foot, increases at the upstream edge of the <span class="hlt">shock</span> ramp, peaks within the ramp, and then quickly decays to steady downstream values. The upstream extent of the noise is on the same order as that of specularly <span class="hlt">reflected</span> gyrating ions. Similar profiles were observed in subcritical and supercritical <span class="hlt">shocks</span>, and no special behavior was associated with the first critical Mach number. Spectra in the foot and ramp were similar in shape, although the noise was 1 to 2 orders of magnitude more intense in the <span class="hlt">shock</span> ramps than in the feet. Electric field intensities are positively correlated with solar wind speed and inversely related to electron beta and Mach number. Magnetic components are positively correlated with Mach number and beta. The results are generally consistent with suggestions that the noise consists of lower hybrid <span class="hlt">waves</span> driven by <span class="hlt">reflected</span> gyrating ions in the foot, and by additional instabilities, such as the cross-field current, in the <span class="hlt">shock</span> ramp.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016cosp...41E.385C&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016cosp...41E.385C&link_type=ABSTRACT"><span id="translatedtitle">Analysis of Metric Type II Burst and EUV <span class="hlt">Waves</span> Generated by <span class="hlt">Shock</span> <span class="hlt">Wave</span> Driven by Cme</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cunha-Silva, Rafael; Fernandes, Francisco; Selhorst, Caius</p> <p>2016-07-01</p> <p>The relationship between solar type II radio bursts produced by plasma oscillations and coronal <span class="hlt">shocks</span> is well shown since the 1960s. However, the details of the association between the drivers of the <span class="hlt">shocks</span> and the metric type II bursts remains a controversial issue. The flares and the coronal mass ejections (CMEs) are the potential drivers of these <span class="hlt">shocks</span>. In this work, we present the analysis of a metric type II burst observed on May 17, 2013, by spectrometers from e-CALLISTO network and EUV images from the Extreme Ultraviolet Imager (EUVI), aboard the STEREO. The event was associated with an M3.2 X-ray flare and a halo CME. The EUV images show the EUV <span class="hlt">wave</span> was produced by the expansion of the CME. The heights of the EUV <span class="hlt">wave</span> fronts and the magnetic field intensity determined in the regions of the <span class="hlt">shock</span> are consistent with those the heights of radio source obtained with the three-fold Newkirk density model, which suggests an oblique propagation of the <span class="hlt">shock</span>. The finding of an accelerating <span class="hlt">shock</span> with speed of 530-640 km/s and of 870-1220 km/s for the first and the second stages of the type II emission, respectively, is consistent with both the average speed of the associated EUV <span class="hlt">wave</span> front, of 626 km/s, during the initial expansion of the CME, and with the linear speed of the CME, of 1345 km/s. These results will be presented and discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015ShWav..25..675B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015ShWav..25..675B"><span id="translatedtitle">Experimental investigation of the stress <span class="hlt">wave</span> propagation inside a granular column impacted by a <span class="hlt">shock</span> <span class="hlt">wave</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Belov, E.; Blachman, M.; Britan, A.; Sadot, O.; Ben-Dor, G.</p> <p>2015-11-01</p> <p>A simple experimental technique, based on pressure transducers, capable of measuring the stress <span class="hlt">wave</span> that propagates along the solid phase of a granular column after being hit head-on by a plane <span class="hlt">shock</span> <span class="hlt">wave</span> is presented. The technique is based on installing couples of gauges at different cross-sections along the granular column in such a way that one transducer measures the overall pressure acting on it while the other measures only the pressure exerted on it by the gaseous phase of the granular column. By means of the presented experimental technique the time histories of the stresses normal to the <span class="hlt">shock</span> tube walls and data on the stress <span class="hlt">wave</span> attenuation as it propagates downstream towards the <span class="hlt">shock</span> tube end wall were obtained.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003SPIE.4948..263N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003SPIE.4948..263N"><span id="translatedtitle">Biological effect of <span class="hlt">shock</span> <span class="hlt">waves</span> on rat brain: pathological evaluation by compact Ho:YAG-laser-induced cavitational <span class="hlt">shock</span> <span class="hlt">wave</span> generator</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nakagawa, Atsuhiro; Hirano, T.; Kusaka, Y.; Sato, Motoyuki; Shirane, R.; Takayama, Kazuya; Yoshimoto, Takashi</p> <p>2003-07-01</p> <p>To introduce <span class="hlt">shock</span> <span class="hlt">wave</span> as a new treatment modality for the lesions in the vicinity of brain and skull, pressure-dependent brain damages after exposure of <span class="hlt">shock</span> <span class="hlt">wave</span> were investigated. A novel compact Ho:YAG laser-induced cavitational <span class="hlt">shock</span> <span class="hlt">wave</span> generator (diameter: 15 mm, weight: 20g) was used intstead of clinical lithotriptors due to their wide distribution of <span class="hlt">shock</span> <span class="hlt">waves</span>. In the first part, we have developed and investigated characteristics of present generator by means of high-speed photography, shadowgraphy, and pressure measurement. Generation of localized <span class="hlt">shock</span> <span class="hlt">wave</span> without harmful effect of laser was observed after irradiation of Ho:YAG laser in the brass tube with internal water supply. Mechanical effect of accompanying laser-induced liquid jet was mitigated after placement of latex diaphragm with acrylic water reservoir. Maximum overpressure of generated <span class="hlt">shock</span> <span class="hlt">wave</span> was 15 MPa before placement of diaphragm, and 5 MPa after placement of diaphragm. In the second part, <span class="hlt">shock</span> <span class="hlt">wave</span>-induced brain damages were investigated in 5 male Sprague-Dawley rats. While subarachnoid hemorrhage could be observed between 1 and 5 MPa, intracerebral hemorrhage, and laceration of tissue were also observed above 5 MPa. We therefore conclude that overpressure of exposing <span class="hlt">shock</span> <span class="hlt">wave</span> over brain surface should be managed under 1 MPa.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19880003924','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19880003924"><span id="translatedtitle">Interferometric data for a <span class="hlt">shock-wave</span>/boundary-layer interaction</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Dunagan, Stephen E.; Brown, James L.; Miles, John B.</p> <p>1986-01-01</p> <p>An experimental study of the axisymmetric <span class="hlt">shock-wave</span> / boundary-layer strong interaction flow generated in the vicinity of a cylinder-cone intersection was conducted. The study data are useful in the documentation and understanding of compressible turbulent strong interaction flows, and are part of a more general effort to improve turbulence modeling for compressible two- and three-dimensional strong viscous/inviscid interactions. The nominal free stream Mach number was 2.85. Tunnel total pressures of 1.7 and 3.4 atm provided Reynolds number values of 18 x 10(6) and 36 x 10(6) based on model length. Three cone angles were studied giving negligible, incipient, and large scale flow separation. The initial cylinder boundary layer upstream of the interaction had a thickness of 1.0 cm. The subsonic layer of the cylinder boundary layer was quite thin, and in all cases, the <span class="hlt">shock</span> <span class="hlt">wave</span> penetrated a significant portion of the boundary layer. Owing to the thickness of the cylinder boundary layer, considerable structural detail was resolved for the three <span class="hlt">shock-wave</span> / boundary-layer interaction cases considered. The primary emphasis was on the application of the holographic interferometry technique. The density field was deduced from an interferometric analysis based on the Able transform. Supporting data were obtained using a 2-D laser velocimeter, as well as mean wall pressure and oil flow measurements. The attached flow case was observed to be steady, while the separated cases exhibited <span class="hlt">shock</span> unsteadiness. Comparisons with Navier-Stokes computations using a two-equation turbulence model are presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/6138630','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/6138630"><span id="translatedtitle">Relativistic <span class="hlt">shock</span> <span class="hlt">waves</span> and the excitation of plerions</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Arons, J. ); Gallant, Y.A. . Dept. of Physics); Hoshino, Masahiro; Max, C.E. . Inst. of Geophysics and Planetary Physics); Langdon, A.B. )</p> <p>1991-01-07</p> <p>The <span class="hlt">shock</span> termination of a relativistic magnetohydrodynamic wind from a pulsar is the most interesting and viable model for the excitation of the synchrotron sources observed in plerionic supernova remnants. We have studied the structure of relativistic magnetosonic <span class="hlt">shock</span> <span class="hlt">waves</span> in plasmas composed purely of electrons and positrons, as well as those whose composition includes heavy ions as a minority constituent by number. We find that relativistic <span class="hlt">shocks</span> in symmetric pair plasmas create fully thermalized distributions of particles and fields downstream. Therefore, such <span class="hlt">shocks</span> are not good candidates for the mechanism which converts rotational energy lost from a pulsar into the nonthermal synchrotron emission observed in plerions. However, when the upstream wind contains heavy ions which are minority constituent by number density, but carry the bulk of the energy density, much of the energy of the <span class="hlt">shock</span> goes into a downstream, nonthermal power law distribution of positrons with energy distribution N(E)dE {proportional to}E{sup {minus}s}. In a specific model presented in some detail, s = 3. These characteristics are close to those assumed for the pairs in macroscopic MHD wind models of plerion excitation. The essential mechanism is collective synchrotron emission of left-handed extraordinary modes by the ions in the <span class="hlt">shock</span> front at high harmonics of the ion cyclotron frequency, with the downstream positrons preferentially absorbing almost all of this radiation, mostly at their fundamental (relativistic) cyclotron frequencies. Possible applications to models of plerions and to constraints on theories of energy loss from pulsars are briefly outlines. 27 refs., 5 figs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19930049652&hterms=terrestre&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dterrestre','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19930049652&hterms=terrestre&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dterrestre"><span id="translatedtitle">Plasma <span class="hlt">wave</span> phenomena at interplanetary <span class="hlt">shocks</span> observed by the Ulysses URAP experiment. [Unified Radio and Plasma <span class="hlt">Waves</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Lengyel-Frey, D.; Macdowall, R. J.; Stone, R. G.; Hoang, S.; Pantellini, F.; Harvey, C.; Mangeney, A.; Kellogg, P.; Thiessen, J.; Canu, P.</p> <p>1992-01-01</p> <p>We present Ulysses URAP observations of plasma <span class="hlt">waves</span> at seven interplanetary <span class="hlt">shocks</span> detected between approximately 1 and 3 AU. The URAP data allows ready correlation of <span class="hlt">wave</span> phenomena from .1 Hz to 1 MHz. <span class="hlt">Wave</span> phenomena observed in the <span class="hlt">shock</span> vicinity include abrupt changes in the quasi-thermal noise continuum, Langmuir <span class="hlt">wave</span> activity, ion acoustic noise, whistler <span class="hlt">waves</span> and low frequency electrostatic <span class="hlt">waves</span>. We focus on the forward/reverse <span class="hlt">shock</span> pair of May 27, 1991 to demonstrate the characteristics of the URAP data.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1998GeoJI.132..577J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1998GeoJI.132..577J"><span id="translatedtitle">Polarization and amplitude attributes of <span class="hlt">reflected</span> plane and spherical <span class="hlt">waves</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jiang, Jinjun; Baird, Graham; Blair, Dane</p> <p>1998-03-01</p> <p>The characteristics of a <span class="hlt">reflected</span> spherical <span class="hlt">wave</span> at a free surface are investigated by numerical methods; in particular, the polarization angles and amplitude coefficients of a <span class="hlt">reflected</span> spherical <span class="hlt">wave</span> are studied. The classical case of the <span class="hlt">reflection</span> of a plane P <span class="hlt">wave</span> from a free surface is revisited in order to establish our terminology, and the classical results are recast in a way which is more suited for the study undertaken. The polarization angle of a plane P <span class="hlt">wave</span>, for a given angle of incidence, is shown to be 90° minus twice the angle of <span class="hlt">reflection</span> of the <span class="hlt">reflected</span> S <span class="hlt">wave</span>. For a Poisson's ratio less than 1/3, there is a non-normal incident angle for which both amplification coefficients are 2 precisely; for this incident angle the direction of the particle motion at the free surface is also the direction of the incident <span class="hlt">wave</span>. For a <span class="hlt">wave</span> emanating from a spherical source, the polarization angle, for all angles of incidence, is always less than, or equal to, the polarization angle of a plane P <span class="hlt">wave</span>. The vector amplification coefficient of a spherical <span class="hlt">wave</span>, for all angles of incidence, is always greater than the vector amplification coefficient of a plane P <span class="hlt">wave</span>. As expected, the results for a spherical <span class="hlt">wave</span> approach the results for a plane P <span class="hlt">wave</span> in the far field. Furthermore, there was a good agreement between the theoretical modelling and the numerical modelling using the dynamic finite element method (DFEM).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016APS..MAR.M1283T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016APS..MAR.M1283T"><span id="translatedtitle"><span class="hlt">Shock</span> <span class="hlt">wave</span> irradiations avoiding fluid flow evoke intracellular Ca2+ signaling</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Takahashi, Toru; Tsukamoto, Akira; Tada, Shigeru</p> <p></p> <p><span class="hlt">Shock</span> <span class="hlt">wave</span> irradiation accelerates therapeutic effects including angiogenesis. One mechanism underlying those effects is cellular responses evoked by <span class="hlt">shock</span> <span class="hlt">wave</span> irradiation. Fluid flow is one of major physical phenomena induced by <span class="hlt">shock</span> <span class="hlt">wave</span> irradiation. Cellular responses evoked by fluid flow are similar to those evoked by <span class="hlt">shock</span> <span class="hlt">wave</span> irradiation. Thus, fluid flow could be responsible for cellular responses evoked by <span class="hlt">shock</span> <span class="hlt">wave</span> irradiation. However, it is obscure whether fluid flow is required for the cellular responses evoked by <span class="hlt">shock</span> <span class="hlt">wave</span> irradiation. In this study, intracellular Ca2 + signaling was observed in cells seeded in down-sized chambers. In the down-sized chambers, fluid flow was supposed to be suppressed because size of chambers (6 mm in diameter, 1 mm in thickness) was analogous to size of <span class="hlt">shock</span> <span class="hlt">wave</span> focus region (3mm in diameter). Dynamics of polystyrene microbeads suspended in the chambers were visualized with a CCD camera and analyzed with a particle image velocimetry (PIV) method to quantify fluid flow in the chamber. As a result, <span class="hlt">shock</span> <span class="hlt">wave</span> irradiation evoked intracellular Ca2 + signaling. However, fluid flow was not observed in the chamber due to <span class="hlt">shock</span> <span class="hlt">wave</span> irradiation. Thus, it was suggested that physical mechanics, not fluid flow, are further required for evoking intracellular Ca2 + signaling following to <span class="hlt">shock</span> <span class="hlt">wave</span> irradiation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFMNG23A1369S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFMNG23A1369S"><span id="translatedtitle">Experimental particle acceleration by water evaporation induced by <span class="hlt">shock</span> <span class="hlt">waves</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Scolamacchia, T.; Alatorre Ibarguengoitia, M.; Scheu, B.; Dingwell, D. B.; Cimarelli, C.</p> <p>2010-12-01</p> <p><span class="hlt">Shock</span> <span class="hlt">waves</span> are commonly generated during volcanic eruptions. They induce sudden changes in pressure and temperature causing phase changes. Nevertheless, their effects on flowfield properties are not well understood. Here we investigate the role of gas expansion generated by <span class="hlt">shock</span> <span class="hlt">wave</span> propagation in the acceleration of ash particles. We used a <span class="hlt">shock</span> tube facility consisting of a high-pressure (HP) steel autoclave (450 mm long, 28 mm in internal diameter), pressurized with Ar gas, and a low-pressure tank at atmospheric conditions (LP). A copper diaphragm separated the HP autoclave from a 180 mm tube (PVC or acrylic glass) at ambient P, with the same internal diameter of the HP reservoir. Around the tube, a 30 cm-high acrylic glass cylinder, with the same section of the LP tank (40 cm), allowed the observation of the processes occurring downstream from the nozzle throat, and was large enough to act as an unconfined volume in which the initial diffracting <span class="hlt">shock</span> and gas jet expand. All experiments were performed at Pres/Pamb ratios of 150:1. Two ambient conditions were used: dry air and air saturated with steam. Carbon fibers and glass spheres in a size range between 150 and 210 μm, were placed on a metal wire at the exit of the PVC tube. The sudden decompression of the Ar gas, due to the failure of the diaphragm, generated an initial air <span class="hlt">shock</span> <span class="hlt">wave</span>. A high-speed camera recorded the processes between the first 100 μsec and several ms after the diaphragm failure at frame rates ranging between 30,000 and 50,000 fps. In the experiments with ambient air saturated with steam, the high-speed camera allowed to visualize the condensation front associated with the initial air <span class="hlt">shock</span>; a maximum velocity of 788 m/s was recorded, which decreases to 524 m/s at distance of 0.5 ±0.2 cm, 1.1 ms after the diaphragm rupture. The condensation front preceded the Ar jet front exhausting from the reservoir, by 0.2-0.5 ms. 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