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Sample records for parallel shock layers

  1. Parallelization of the Flow Field Dependent Variation Scheme for Solving the Triple Shock/Boundary Layer Interaction Problem

    NASA Technical Reports Server (NTRS)

    Schunk, Richard Gregory; Chung, T. J.

    2001-01-01

    A parallelized version of the Flowfield Dependent Variation (FDV) Method is developed to analyze a problem of current research interest, the flowfield resulting from a triple shock/boundary layer interaction. Such flowfields are often encountered in the inlets of high speed air-breathing vehicles including the NASA Hyper-X research vehicle. In order to resolve the complex shock structure and to provide adequate resolution for boundary layer computations of the convective heat transfer from surfaces inside the inlet, models containing over 500,000 nodes are needed. Efficient parallelization of the computation is essential to achieving results in a timely manner. Results from a parallelization scheme, based upon multi-threading, as implemented on multiple processor supercomputers and workstations is presented.

  2. Parallelization of the Flow Field Dependent Variation Scheme for Solving the Triple Shock/Boundary Layer Interaction Problem

    NASA Technical Reports Server (NTRS)

    Schunk, Greg; chung, T. J.

    1999-01-01

    A parallelized version of the Flowfield Dependent Variation (FDV) Method is developed to analyze a problem of current research interest, the flowfield resulting from a triple shock/boundary layer interaction. Such flowfields are often encountered in the inlets of high speed air-breathing vehicles including NASA's Hyper-X. In order to resolve the complex shock structure and to provide adequate resolution for boundary layer computations of the convective heat transfer from surfaces inside the inlet, models containing over 500,000 nodes are needed. Efficient parallelization of the computation is essential to obtaining the results in a timely manner. Results from different parallelization schemes, based upon multi-threading and message passing, as implemented on multiple processor supercomputers and on distributed workstations are compared.

  3. Theory and simulation of collisionless parallel shocks

    NASA Technical Reports Server (NTRS)

    Quest, K. B.

    1988-01-01

    This paper presents a self-consistent theoretical model for collisionless parallel shock structure, based on the hypothesis that shock dissipation and heating can be provided by electromagnetic ion beam-driven instabilities. It is shown that shock formation and plasma heating can result from parallel propagating electromagnetic ion beam-driven instabilities for a wide range of Mach numbers and upstream plasma conditions. The theoretical predictions are compared with recently published observations of quasi-parallel interplanetary shocks. It was found that low Mach number interplanetary shock observations were consistent with the explanation that group-standing waves are providing the dissipation; two high Mach number observations confirmed the theoretically predicted rapid thermalization across the shock.

  4. Double layers and electrostatic shocks

    NASA Technical Reports Server (NTRS)

    Hershkowitz, N.

    1981-01-01

    It is shown that it is useful to define double layers and shocks so that the ion phase spaces of double layers are the mirror image (about zero ion velocity) of the ion phase spaces for laminar electrostatic shocks. The distinguishing feature is the direction of the free ion velocity. It is also shown that double layers can exist without the presence of trapped ions. The Bohm condition for double layers, that the ion drift velocity on the high potential side must be greater than the ion sound velocity, is shown to be related to a requirement of a lower limit on the Mach number of laminar electrostatic shocks

  5. Modelling Layer parallel stylolites

    NASA Astrophysics Data System (ADS)

    Koehn, Daniel; Pataki Rood, Daisy; Beaudoin, Nicolas

    2016-04-01

    We modeled the geometrical roughening of mainly layer-dominated stylolites in order to understand their structural evolution, to present an advanced classification of stylolite shapes and to relate this classification to chemical compaction and stylolite sealing capabilities. Our simulations show that layer-dominated stylolites can grow in three distinct stages, an initial slow nucleation, a fast layer-pinning phase and a final freezing stage if the layer dissolves completely during growth. Dissolution of the pinning layer and thus destruction of the compaction tracking capabilities is a function of the background noise in the rock and the dissolution rate of the layer itself. Low background noise needs a slower dissolving layer for pinning to be successful but produces flatter teeth than higher background noise. We present an advanced classification based on our simulations and separate stylolites into four classes: rectangular layer type, seismogram pinning type, suture/sharp peak type and simple wave-like type.

  6. Low Mach number parallel and quasi-parallel shocks

    NASA Technical Reports Server (NTRS)

    Omidi, N.; Quest, K. B.; Winske, D.

    1990-01-01

    The properties of low-Mach-number parallel and quasi-parallel shocks are studied using the results of one-dimensional hybrid simulations. It is shown that both the structure and ion dissipation at the shocks differ considerably. In the parallel limit, the shock remains coupled to the piston and consists of large-amplitude magnetosonic-whistler waves in the upstream, through the shock and into the downstream region, where the waves eventually damp out. These waves are generated by an ion beam instability due to the interaction between the incident and piston-reflected ions. The excited waves decelerate the plasma sufficiently that it becomes stable far into the downstream. The increase in ion temperature along the shock normal in the downstream region is due to superposition of incident and piston-rflected ions. These two populations of ions remain distinct through the downstream region. While they are both gyrophase-bunched, their counterstreaming nature results in a 180-deg phase shift in their perpendicular velocities.

  7. Heavy ion acceleration at parallel shocks

    NASA Astrophysics Data System (ADS)

    Galinsky, V. L.; Shevchenko, V. I.

    2010-11-01

    A study of alpha particle acceleration at parallel shock due to an interaction with Alfvén waves self-consistently excited in both upstream and downstream regions was conducted using a scale-separation model (Galinsky and Shevchenko, 2000, 2007). The model uses conservation laws and resonance conditions to find where waves will be generated or damped and hence where particles will be pitch-angle scattered. It considers the total distribution function (for the bulk plasma and high energy tail), so no standard assumptions (e.g. seed populations, or some ad-hoc escape rate of accelerated particles) are required. The heavy ion scattering on hydromagnetic turbulence generated by both protons and ions themselves is considered. The contribution of alpha particles to turbulence generation is important because of their relatively large mass-loading parameter Pα=nαmα/npmp (mp, np and mα, nα are proton and alpha particle mass and density) that defines efficiency of wave excitation. The energy spectra of alpha particles are found and compared with those obtained in test particle approximation.

  8. Internal hypersonic flow. [in thin shock layer

    NASA Technical Reports Server (NTRS)

    Lin, T. C.; Rubin, S. G.

    1974-01-01

    An approach for studying hypersonic internal flow with the aid of a thin-shock-layer approximation is discussed, giving attention to a comparison of thin-shock-layer results with the data obtained on the basis of the imposition theory or a finite-difference integration of the Euler equations. Relations in the case of strong interaction are considered together with questions of pressure distribution and aspects of the boundary-layer solution.

  9. Escape of heated ions upstream of quasi-parallel shocks

    NASA Technical Reports Server (NTRS)

    Edmiston, J. P.; Kennel, C. F.; Eichler, D.

    1982-01-01

    A simple theoretical criterion by which quasi-parallel and quasi-perpendicular collisionless shocks may be distinguished is proposed on the basis of an investigation of the free escape of ions from the post-shock plasma into the region upstream of a fast collisionless shock. It was determined that the accessibility of downstream ions to the upstream region depends on upstream magnetic field shock normal angle, in addition to the upstream plasma parameters, with post-shock ions escaping upstream for shock normal angles of less than 45 deg, in agreement with the observed transition between quasi-parallel and quasi-perpendicular shock structure. Upstream ion distribution functions resembling those of observed intermediate ions and beams are also calculated.

  10. Shock-boundary-layer interaction in flight

    NASA Technical Reports Server (NTRS)

    Bertelrud, Arild

    1989-01-01

    A brief survey is given on the study of transonic shock/boundary layer effects in flight. Then the possibility of alleviating the adverse shock effects through passive shock control is discussed. A Swedish flight experiment on a swept wing attack aircraft is used to demonstrate how it is possible to reduce the extent of separated flow and increase the drag-rise Mach number significantly using a moderate amount of perforation of the surface.

  11. Scale lengths in quasi-parallel shocks. [interplanetary and earth bow waves

    NASA Technical Reports Server (NTRS)

    Scudder, J. D.; Burlaga, L. F.; Greenstadt, E. W.

    1984-01-01

    A review was carried out of ISEE and Voyager spacecraft magnetometer data to determine if quasi-parallel bow shocks are really broad, disordered regions. The key parameter was the deceleration scale (thickness, Lp) across which random energy would need to increase and a localized electrostatic field (E) would be present. Lp would define the breadth of the shock and be associated with a plasma deceleration. The ISEE 1 satellite collected data on the electron density, bulk speed, magnetic intensity, and electron temperature in November 1977 during five traverses of the bow shock. Similar data were gathered from an interplanetary shock wave in 1981. The evidence supported the concept of a plasma deceleration across a thin layer (Lp) in both types of shocks. The layers were about 50 times (interplanetary) and 20 times (earth) thinner than surrounding magnetic fluctuation regions. It is asserted that the regions of deceleration, although much thinner, are the actual shocks and not the entire regions of magnetic fluctuations.

  12. Preliminary investigation of interplanetary shock structure: Quasi-parallel shocks

    NASA Technical Reports Server (NTRS)

    Greenstadt, E. W.

    1974-01-01

    Pioneer 9's magnetic field and plasma data were studied to develop arguments for or against the observation of oblique interplanetary shocks. Structural classifications are defined, and the justification for seeking these classifications in the solar wind are presented.

  13. Ion Acceleration at the Quasi-parallel Bow Shock: Decoding the Signature of Injection

    NASA Astrophysics Data System (ADS)

    Sundberg, Torbjörn; Haynes, Christopher T.; Burgess, D.; Mazelle, Christian X.

    2016-03-01

    Collisionless shocks are efficient particle accelerators. At Earth, ions with energies exceeding 100 keV are seen upstream of the bow shock when the magnetic geometry is quasi-parallel, and large-scale supernova remnant shocks can accelerate ions into cosmic-ray energies. This energization is attributed to diffusive shock acceleration however, for this process to become active, the ions must first be sufficiently energized. How and where this initial acceleration takes place has been one of the key unresolved issues in shock acceleration theory. Using Cluster spacecraft observations, we study the signatures of ion reflection events in the turbulent transition layer upstream of the terrestrial bow shock, and with the support of a hybrid simulation of the shock, we show that these reflection signatures are characteristic of the first step in the ion injection process. These reflection events develop in particular in the region where the trailing edge of large-amplitude upstream waves intercept the local shock ramp and the upstream magnetic field changes from quasi-perpendicular to quasi-parallel. The dispersed ion velocity signature observed can be attributed to a rapid succession of ion reflections at this wave boundary. After the ions’ initial interaction with the shock, they flow upstream along the quasi-parallel magnetic field. Each subsequent wavefront in the upstream region will sweep the ions back toward the shock, where they gain energy with each transition between the upstream and the shock wave frames. Within three to five gyroperiods, some ions have gained enough parallel velocity to escape upstream, thus completing the injection process.

  14. Ion reflection and downstream thermalization at the quasi-parallel bow shock

    NASA Technical Reports Server (NTRS)

    Gosling, J. T.; Thomsen, M. F.; Bame, S. J.; Russell, C. T.

    1989-01-01

    Using the results of ISEE 2 plasma and magnetic field measurements, two features related to the ion thermalization process at high-Mach-number (M above 2) quasi-parallel collisionless shocks are discussed. These are the presence of a coherent secondary beam of ions within the shock layer which is considered to be produced by reflection, and downstream ion distributions which contain both a relatively cold core of directly transmitted ions and a hotter 'shell' of ions, which appear to result from the disruption and scattering of ions initially reflected at the shock. Evidence is presented that coherent ion reflection is an important element of the ion energy dissipation process at high-Mach-number quasi-parallel shocks.

  15. Shock timing measurements in DT ice layers

    NASA Astrophysics Data System (ADS)

    Robey, H. F.; Celliers, P. M.; Moody, J. D.; Sater, J.; Parham, T.; Kozioziemski, B.; Dylla-Spears, R. J.; Ross, J. S.; Lepape, S.; Ralph, J. E.; Berzak Hopkins, L. F.; Kroll, J. J.; Yoxall, B. E.; Hamza, A. V.; Boehly, T. R.; Nikroo, A.; Landen, O. L.; Edwards, M. J.

    2013-10-01

    Shock timing experiments on the National Ignition Facility (NIF) are routinely conducted using the keyhole target geometry, in which the strength and timing of multiple shocks are measured in a liquid-deuterium (D2) filled capsule interior. These targets have recently been modified to improve the surrogacy to ignition implosions by replacing the standard, continuous liquid D2 capsule fill with a deuterium-tritium (DT) ice layer with a central DT gas fill. These experiments remove any possible material surrogacy difference between D2 and DT as well as incorporating the physics of multiple shock release and recompression events from an ice layer of finite thickness, an effect that is absent in the liquid-filled targets. Experimental results and comparisons with numerical simulation are presented. Prepared by LLNL under Contract DE-AC52-07NA27344.

  16. Thermal shock response of layered orthotropic media

    SciTech Connect

    Santhosh, U. )

    1992-09-01

    In this article a coupled thermoelastic theory including inertia effects is used to determine the through-thickness temperature and stress distribution in a laminated medium subjected to thermal shock loading. The solution is obtained using an implicit-explicit finite difference procedure, and numerical results are presented for composites made of layers of a carbon substrate and a coating. 14 refs.

  17. Direct Simulation of Shock Layer Plasmas

    SciTech Connect

    Farbar, E. D.; Boyd, I. D.

    2011-05-20

    Approximate models of the electric field used with the DSMC method all impose quasi-neutrality everywhere in the shock layer plasma. The shortcomings of these models are examined in this study by simulating a weak shock layer plasma with a coupled DSMC-Particle-In-Cell (PIC) method. The stagnation streamline of an axisymmetric shock layer is simulated for entry velocities in air that correspond to both lunar and Mars return trajectories. The atmospheric densities, particle diameters and chemical reaction rates are varied from the actual values to make the computations tractable while retaining the mean free path of air at 85 km altitude. In contrast to DSMC flow field predictions, regions of non-neutrality are predicted by the DSMC-PIC method, and the electrons are predicted to be isothermal. Perhaps the most important result of this study is that the DSMC-PIC results at both reentry energies yield a 14% increase in heat flux to the vehicle surface relative to the DSMC results. Rather unintuitively, this is mostly due to an increase in ion flux to the surface, rather than the potential energy gained by each ion as it traverses the plasma sheath. In this study, an approximate electric field model is presented, with the goal of accounting for this heat flux augmentation without the need for a computationally expensive DSMC-PIC calculation of the entire flow-field. Convective heat flux results obtained with new electric field model are compared to results from the rigorous DSMC-PIC calculations.

  18. Quasi-perpendicular/quasi-parallel divisions of Earth's bow shock

    SciTech Connect

    Greenstadt, E.W. )

    1991-02-01

    Computer-drawn diagrams of the boundaries between quasi-perpendicular and quasi-parallel areas of Earth's bow shock are displayed for a few selected cone angles of static interplanetary magnetic field (IMF). The effect on the boundary of variable IMF in the foreshock is also discussed and shown for one nominal case. The boundaries demand caution in applying them to the realistic, dynamic conditions of the solar wind and in interpreting the effects of small cone angles on the distributions of structures at the shock. However, the calculated, first-order boundaries are helpful in defining areas of the shock where contributions from active structures inherent in quasi-parallel geometry may be distinguishable from those derived secondarily from upstream reflected ion dynamics. The boundaries are also compatible with known behavior of daytime ULF geomagnetic waves and pulsations according to models postulating that cone angle-controlled, time-dependent ULF activity around the subsolar point of the bow shock provides the source of geomagnetic excitation.

  19. 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.

  20. Shock interactions with a dense-gas wall layer

    SciTech Connect

    Kuhl, A.L. ); Reichenbach, H. ); Ferguson, R.E. )

    1991-11-19

    Described here are experiments and calculations of the interaction of a planar shock with a dense-gas layer located on the floor of the shock tube test section. The shock front deposited vorticity in the layer by the baroclynic mechanism. The wall shear layer was unstable and rapidly evolved into a turbulent boundary layer with a wide spectrum of mixing scales. Density effects dominated the dynamics in the wall region.

  1. On Nonequilibrium Radiation in Hydrogen Shock Layers

    NASA Technical Reports Server (NTRS)

    Park, Chul

    2005-01-01

    The influence of thermochemical nonequilibrium in the shock layer over a vehicle entering the atmosphere of an outer planet is examined qualitatively. The state of understanding of the heating environment for the Galileo Probe vehicle is first reviewed. Next, the possible reasons for the high recession in the frustum region and the low recession in the stagnation region are examined. The state of understanding of the nonequilibrium in the hydrogen flow is then examined. For the entry flight in Neptune, the possible influence of nonequilibrium is predicted.

  2. Improved method for solving the viscous shock layer equations

    NASA Technical Reports Server (NTRS)

    Gordon, Rachel; Davis, R. T.

    1992-01-01

    An improved method for solving the viscous shock layer equations for supersonic/hypersonic flows past blunt-nosed bodies is presented. The method is capable of handling slender to thick bodies. The solution is obtained by solving a coupled set of five equations, built of the four basic viscous shock layer equations and an additional equation for the standoff distance. The coupling of the equations prevents the local iterations divergence problems encountered by previous methods of solution far downstream on slender bodies. It also eliminates the need for local iterations, which were required by previous methods of solution, for a first-order scheme in the streamwise direction. A new global iteration procedure is employed to impose the shock boundary conditions. The procedure prevents the global iteration instability encountered by the basic method of solution and improves the convergence rate of the global iteration procedure of later methods devised to overcome this difficulty. The new technique reduces the computation time by 65-95 percent as compared to previous methods of solution. The method can efficiently be implemented in vector/parallel computers.

  3. Magnetic pulsations at the quasi-parallel shock

    NASA Technical Reports Server (NTRS)

    Thomsen, M. F.; Gosling, J. T.; Bame, S. J.; Russell, C. T.

    1990-01-01

    The plasma and field properties of large-amplitude magnetic field pulsatins upstream from the quasi-parallel region of the earth's bow shock are examined in high time resolution using data from ISEE 1 and 2. The relative timing of the magnetic field profiles observed at the two spacecraft shows that some of the pulsations are convecting antisunward across the spacecraft while others are brief out/in motions of bow shock across the spacecraft. Pulsations with both timing signatures are the site of slowing and heating of the solar wind plasma. The ions tend to be only weakly heated in the convecting pulsations, while within the out/in pulsations the ion heating can be quite substantial but variable. This variation occurs not only from pulsation to pulsation but also from point to point within a given pulsation. In general, the hottest distributions within the out/in pulsations tend to occur in regions of lower density and field strength. Magnetic pulsations bear a number of similarities to previously identified hot diamagnetic cavity events as well as to more durable crossings of the quasi-parallel shock itself. These various phenomena may be different manifestations of the same basic physical processes, in particular the coupling of coherently reflected ions to the solar wind beam.

  4. Radiography for a Shock-accelerated Liquid Layer

    SciTech Connect

    P. Meekunnasombat J.G. Oakley\\inst M.H. Anderson R. Bonazza

    2005-07-01

    This program supported the experimental study of the itneraction of planar shock waves with both solid structures (a single cylinder or a bank of cylinders) and single and multiple liquid layers. Objectives of the study included: characterization of the shock refraction patterns; measurements of the impulsive loading of the solid structures; observation of the response of the liquid layers to shock acceleration; assessment of the shock-mitigation effects of single and multiple liquid layers. The uploaded paper is intended as a final report for the entire funding period. The poster described in the paper won the Best Poster Award at the 25 International Symposium on Shock Waves.

  5. 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.

  6. Shock layer radiance effects on endoatmospheric interceptor seeker performance

    NASA Astrophysics Data System (ADS)

    Trolier, J.; Hudson, D.; Carlson, D.; Krawczyk, W.

    1992-05-01

    A method is described in detail to allow prediction of infrared radiance from shock layers surrounding high altitude hypersonic endoatmospheric interceptors. Flowfield properties calculated with the EXTC code for a representative endoatmospheric interceptor forebody are shown, including thermal and chemical nonequilibrium effects for both clean air and atmospheric trace species. The SIRRM-II radiative transport code was used with a modified version of the NORSE infrared radiance database to predict radiance and transmission through the shock layer. A simple sensor model, including spectral target signatures, window thermal emission noise, and shock layer radiance is employed to illustrate the importance of the shock layer radiance effects. Shock layer radiance is found to increase with decreasing altitude, with significant broadening of spectral emission bands at lower altitudes.

  7. Re-forming supercritical quasi-parallel shocks. I - One- and two-dimensional simulations

    NASA Technical Reports Server (NTRS)

    Thomas, V. A.; Winske, D.; Omidi, N.

    1990-01-01

    The process of reforming supercritical quasi-parallel shocks is investigated using one-dimensional and two-dimensional hybrid (particle ion, massless fluid electron) simulations both of shocks and of simpler two-stream interactions. It is found that the supercritical quasi-parallel shock is not steady. Instread of a well-defined shock ramp between upstream and downstream states that remains at a fixed position in the flow, the ramp periodically steepens, broadens, and then reforms upstream of its former position. It is concluded that the wave generation process is localized at the shock ramp and that the reformation process proceeds in the absence of upstream perturbations intersecting the shock.

  8. Unsteadiness of Shock Wave / Boundary Layer Interactions

    NASA Astrophysics Data System (ADS)

    Clemens, Noel

    2009-11-01

    Shock wave / 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

  9. Critical pitch angle for electron acceleration in a collisionless shock layer

    NASA Astrophysics Data System (ADS)

    Narita, Y.; Comişel, H.; Motschmann, U.

    2016-07-01

    Collisionless shock waves in space and astrophysical plasmas can accelerate electrons along the shock layer by an electrostatic potential, and scatter or reflect electrons back to the upstream region by the amplified magnetic field or turbulent fluctuations. The notion of the critical pitch angle is introduced for non-adiabatic electron acceleration by balancing the two timescales under a quasi-perpendicular shock wave geometry in which the upstream magnetic field is nearly perpendicular to the shock layer normal direction. An analytic expression of the critical pitch angle is obtained as a function of the electron velocity parallel to the magnetic field, the ratio of the electron gyro- to plasma frequency, the cross-shock potential, the width of the shock transition layer, and the shock angle (which is the angle between the upstream magnetic field and the shock normal direction). For typical non-relativistic solar system applications, the critical pitch angle is predicted to be about 10°. An efficient acceleration is expected below the critical pitch angle.

  10. 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.

  11. Experimental study of a shock accelerated thin gas layer

    SciTech Connect

    Jacobs, J.W.; Jenkins, D.G.; Klein, D.L.; Benjamin, R.F.

    1993-08-01

    Planar laser-induced fluorescence imaging is utilized in shock-tube experiments to visualize the development of a shock-accelerated thin gas layer. The Richtmyer-Meshkov instability of both sides of the heavy gas layer causes perturbations initially imposed on the two interfaces to develop into one of three distinct flow patterns. Two of the patterns exhibit vortex pairs which travel either upstream or downstream in the shock tube, while the third is a sinuous pattern that shows no vortex development until late in its evolution. The development of the observed patterns as well as the growth in the layer thickness is modeled by considering the dynamics of vorticity deposited in the layer by the shock interaction process. This model yields an expression for the layer growth which is in good agreement with measurements.

  12. Vorticity interaction effects on blunt bodies. [hypersonic viscous shock layers

    NASA Technical Reports Server (NTRS)

    Anderson, E. C.; Wilcox, D. C.

    1977-01-01

    Numerical solutions of the viscous shock layer equations governing laminar and turbulent flows of a perfect gas and radiating and nonradiating mixtures of perfect gases in chemical equilibrium are presented for hypersonic flow over spherically blunted cones and hyperboloids. Turbulent properties are described in terms of the classical mixing length. Results are compared with boundary layer and inviscid flowfield solutions; agreement with inviscid flowfield data is satisfactory. Agreement with boundary layer solutions is good except in regions of strong vorticity interaction; in these flow regions, the viscous shock layer solutions appear to be more satisfactory than the boundary layer solutions. Boundary conditions suitable for hypersonic viscous shock layers are devised for an advanced turbulence theory.

  13. Nonequilibrium effects on shock-layer radiometry during earth entry.

    NASA Technical Reports Server (NTRS)

    Arnold, J. O.; Whiting, E. E.

    1973-01-01

    Radiative enhancement factors for the CN violet and N2(+) first negative band systems caused by nonequilibrium thermochemistry in the shock layer of a blunt-nosed vehicle during earth entry are reported. The results are based on radiometric measurements obtained with the aid of a combustion-driven shock tube. The technique of converting the shock-tube measurements into predictions of the enhancement factors for the blunt-body case is described, showing it to be useful for similar applications of other shock-tube measurements.

  14. Giotto magnetic field observations at the outbound quasi-parallel bow shock of Comet Halley

    NASA Technical Reports Server (NTRS)

    Neubauer, F. M.; Glassmeier, K. H.; Acuna, M. H.; Mariani, F.; Musmann, G.

    1990-01-01

    The investigation of the outbound bow shock of Comet Halley using Giotto magnetometer data leads to the following results: the shock is characterized by strong magnetic turbulence associated with an increasing background magnetic field and a change in direction by 60 deg as one goes inward. In HSE-coordinates, the observed normal turned out to be (0.544, - 0.801, 0.249). The thickness of the quasi-parallel shock was 120,000 km. The shock is shown to be a new type of shock transition called a 'draping shock'. In a draping shock with high beta in the transonic transition region, the transonic region is characterized by strong directional variations of the magnetic field. The magnetic turbulence ahead of the shock is characterized by k-vectors parallel or antiparallel to the average field (and, therefore, also to the normal of the quasi-parallel shock) and almost isotropic magnetic turbulence in the shock transition region. A model of the draping shock is proposed which also includes a hypothetical subshock in which the supersonic-subsonic transition is accomplished.

  15. Plasma and energetic particle structure upstream of a quasi-parallel interplanetary shock

    NASA Technical Reports Server (NTRS)

    Kennel, C. F.; Scarf, F. L.; Coroniti, F. V.; Russell, C. T.; Wenzel, K.-P.; Sanderson, T. R.; Van Nes, P.; Smith, E. J.; Tsurutani, B. T.; Scudder, J. D.

    1984-01-01

    ISEE 1, 2 and 3 data from 1978 on interplanetary magnetic fields, shock waves and particle energetics are examined to characterize a quasi-parallel shock. The intense shock studied exhibited a 640 km/sec velocity. The data covered 1-147 keV protons and electrons and ions with energies exceeding 30 keV in regions both upstream and downstream of the shock, and also the magnitudes of ion-acoustic and MHD waves. The energetic particles and MHD waves began being detected 5 hr before the shock. Intense halo electron fluxes appeared ahead of the shock. A closed magnetic field structure was produced with a front end 700 earth radii from the shock. The energetic protons were cut off from the interior of the magnetic bubble, which contained a markedly increased density of 2-6 keV protons as well as the shock itself.

  16. Ion Dynamics at a Rippled Quasi-parallel Shock: 2D Hybrid Simulations

    NASA Astrophysics Data System (ADS)

    Hao, Yufei; Lu, Quanming; Gao, Xinliang; Wang, Shui

    2016-05-01

    In this paper, two-dimensional hybrid simulations are performed to investigate ion dynamics at a rippled quasi-parallel shock. The results show that the ripples around the shock front are inherent structures of a quasi-parallel shock, and the re-formation of the shock is not synchronous along the surface of the shock front. By following the trajectories of the upstream ions, we find that these ions behave differently when they interact with the shock front at different positions along the shock surface. The upstream particles are transmitted more easily through the upper part of a ripple, and the corresponding bulk velocity downstream is larger, where a high-speed jet is formed. In the lower part of the ripple, the upstream particles tend to be reflected by the shock. Ions reflected by the shock may suffer multiple-stage acceleration when moving along the shock surface or trapped between the upstream waves and the shock front. Finally, these ions may escape further upstream or move downstream; therefore, superthermal ions can be found both upstream and downstream.

  17. Monte Carlo Simulations of Nonlinear Particle Acceleration in Parallel Trans-relativistic Shocks

    NASA Astrophysics Data System (ADS)

    Ellison, Donald C.; Warren, Donald C.; Bykov, Andrei M.

    2013-10-01

    We present results from a Monte Carlo simulation of a parallel collisionless shock undergoing particle acceleration. Our simulation, which contains parameterized scattering and a particular thermal leakage injection model, calculates the feedback between accelerated particles ahead of the shock, which influence the shock precursor and "smooth" the shock, and thermal particle injection. We show that there is a transition between nonrelativistic shocks, where the acceleration efficiency can be extremely high and the nonlinear compression ratio can be substantially greater than the Rankine-Hugoniot value, and fully relativistic shocks, where diffusive shock acceleration is less efficient and the compression ratio remains at the Rankine-Hugoniot value. This transition occurs in the trans-relativistic regime and, for the particular parameters we use, occurs around a shock Lorentz factor γ0 = 1.5. We also find that nonlinear shock smoothing dramatically reduces the acceleration efficiency presumed to occur with large-angle scattering in ultra-relativistic shocks. Our ability to seamlessly treat the transition from ultra-relativistic to trans-relativistic to nonrelativistic shocks may be important for evolving relativistic systems, such as gamma-ray bursts and Type Ibc supernovae. We expect a substantial evolution of shock accelerated spectra during this transition from soft early on to much harder when the blast-wave shock becomes nonrelativistic.

  18. MONTE CARLO SIMULATIONS OF NONLINEAR PARTICLE ACCELERATION IN PARALLEL TRANS-RELATIVISTIC SHOCKS

    SciTech Connect

    Ellison, Donald C.; Warren, Donald C.; Bykov, Andrei M. E-mail: ambykov@yahoo.com

    2013-10-10

    We present results from a Monte Carlo simulation of a parallel collisionless shock undergoing particle acceleration. Our simulation, which contains parameterized scattering and a particular thermal leakage injection model, calculates the feedback between accelerated particles ahead of the shock, which influence the shock precursor and 'smooth' the shock, and thermal particle injection. We show that there is a transition between nonrelativistic shocks, where the acceleration efficiency can be extremely high and the nonlinear compression ratio can be substantially greater than the Rankine-Hugoniot value, and fully relativistic shocks, where diffusive shock acceleration is less efficient and the compression ratio remains at the Rankine-Hugoniot value. This transition occurs in the trans-relativistic regime and, for the particular parameters we use, occurs around a shock Lorentz factor γ{sub 0} = 1.5. We also find that nonlinear shock smoothing dramatically reduces the acceleration efficiency presumed to occur with large-angle scattering in ultra-relativistic shocks. Our ability to seamlessly treat the transition from ultra-relativistic to trans-relativistic to nonrelativistic shocks may be important for evolving relativistic systems, such as gamma-ray bursts and Type Ibc supernovae. We expect a substantial evolution of shock accelerated spectra during this transition from soft early on to much harder when the blast-wave shock becomes nonrelativistic.

  19. Hypersonic flow separation in shock wave boundary layer interactions

    NASA Technical Reports Server (NTRS)

    Hamed, A.; Kumar, Ajay

    1992-01-01

    An assessment is presented for the experimental data on separated flow in shock wave 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 shock 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 shock interaction are also presented and discussed.

  20. Simulation of glancing shock wave and boundary layer interaction

    NASA Technical Reports Server (NTRS)

    Hung, Ching-Mao

    1989-01-01

    Shock waves 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 shock 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.

  1. Turbulence at quasi-parallel and quasi-perpendicular bow shocks

    NASA Astrophysics Data System (ADS)

    Pitna, Alexander; Zastenker, Georgy; Nemecek, Zdenek; Safrankova, Jana

    2016-07-01

    A solar wind is a highly turbulent medium carrying various modes of magnetohydrodynamic and kinetic instabilities. During its supersonic expansion, it meets obstacles like planetary magnetospheres and bow shocks are formed. Depending on the orientation of the ambient magnetic field with respect to the local shock normal, either quasi-parallel or quasi-perpendicular shocks can be formed. Particles reflected at the ramp of the quasi-parallel shock are streaming far upstream along the magnetic field lines, giving rise to all sorts of instabilities like SLAMS and ULF waves. In the case of the quasi-perpendicular bow shock, the reflected particles influence only a narrow upstream region of the order of the proton gyroradius but the downstream plasma becomes highly turbulent regardless of the shock type. We analyze the high cadence (31 ms) data from the BMSW instrument onboard the Spektr-R spacecraft and compare the frequency spectra of observed turbulence in MHD and kinetic ranges in upstream and downstream regions of the supercritical quasi-parallel and quasi-perpendicular bow shocks. We found that the change in the fluctuation level (from upstream to downstream) as well as the spectral indices differ substantially in the MHD and kinetic ranges for both types of bow shock.

  2. Numerical calculations of shock-wave/boundary-layer flow interactions

    NASA Astrophysics Data System (ADS)

    Huang, P. G.; Liou, W. W.

    1994-08-01

    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 shock-wave/boundary-layer flows in the 2-D compression corner over a wide range of corner angles and flow conditions.

  3. {open_quotes}Heated layer{close_quotes} effect in interaction of an interplanetary shock wave with a geomagnetic tail

    SciTech Connect

    Aleksandrov, P.E.

    1993-11-01

    Using the numerical solution as the base the conditions of propagating a parallel MGD shock wave in the presence of a heated layer are analyzed, a new {open_quotes}raking regime{open_quotes} of interaction not observed with no magnetic field is revealed. A flow steadiness criterion is obtained, and conditions for the onset of a similarity precursor are estimated.

  4. Search for shock-metamorphosed grains in Precambrian spherule layers

    NASA Astrophysics Data System (ADS)

    Smith, Frank C.

    2014-10-01

    There is minimal physical evidence in only a few of the ˜17 Precambrian spherule layers to support an impact origin. A search was done for shock-metamorphosed grains in the following spherule layers: Carawine, Jeerinah, and Bee Gorge (formerly Wittenoom) in Western Australia, Monteville in South Africa, and Graenseso in South-West Greenland. Samples went through acid digestion, and the residues were wet sieved. The 63-125 mum (+/- 125-250 mum) size fractions went through heavy liquid separation. For most samples, the heavy mineral assemblages consist predominantly of anatase, rutile, tourmaline, and zircon (+/- chrome spinel) grains. Using micro-Raman spectroscopy, the high-pressure, alpha-PbO2 -structured polymorph of TiO2 (TiO2 II) was identified in 27 buff rutile grains from the Carawine, Jeerinah, Bee Gorge, and Monteville spherule layers. For three of the layers, rutile + TiO2 II grains were found only in their upper parts. For a sample or stratigraphic subdivision within a sample, rutile + TiO2 II grains comprise ˜1-5% of the rutile population. The TiO2 II polymorph is interpreted as a shock-induced phase that is syngenetic with respect to its host spherule layer. The rutile + TiO2 II grains provide physical evidence to support an impact origin for these four spherule layers. Using a universal stage microscope, measurements of the crystallographic orientations of planar microstructures in three quartz grains from the Carawine spherule layer support the interpretation that the microstructures are shock-induced planar deformation features. No unequivocal evidence of shock metamorphism was found in the white opaque zircon grains; instead, these grains appear to have varying degrees of metamictization. The physical properties of the chrome spinel, rutile, and zircon grains support the previously proposed hypothesis that the Carawine, Jeerinah, and Monteville spherule layers are parts of a single spherule layer that is older than the Bee Gorge spherule layer

  5. Direct simulation of shock-induced mixing layer

    SciTech Connect

    Greenough, J.A.; Bell, J.B.

    1993-03-01

    The interaction of a shock wave with a dense fluid layer in three dimensions is investigated using direct numerical simulations. The underlying numerical method is a second-order Godunov scheme. This is coupled to an implementation of Adaptive Mesh Refinement which is used to manage the hierarchical grid structure. An anomalous shock refraction is formed as the initiating shock wave impinges on a quiescent thin dense gas layer. One of the two resulting centered waves from the refraction, the contact surface, serves as the site for initial deposition of primarily spanwise vorticity and represents the primary mixing layer instability. The other wave, the transmitted shock wave, through repeated interactions with the free-surface, forms a cellular structure within the dense layer. The initial interaction introduces three dimensional perturbations onto the slip surface. These perturbations are selectively enhanced, due to favorable velocity gradients over part of the cellular structures, and form large-scale counter-rotating streamwise vertical structures. The structures characterize the secondary instability of this mixing layer. These vortices are quite unstable and transition to small-scales within a distance spanned by two of the cellular structures behind the initiating shock. The transition location has been verified in physical experiments. The fine-scale structure contains evidence of hairpin vortices. The evolution of a conserved scalar is used to monitor mixing progress. Increases in the rate of mixing are directly tied to intensification events associated with the streamwise vortices. Overall the large-scale streamwise structures provide an efficient mechanism for mixing the light and dense fluids. Analysis of time-series data from the calculation shows evidence of what are termed energetic smallscales. This is the characteristic signature of the hairpin vortices undergoing intensification.

  6. Interferometric data for a shock-wave/boundary-layer interaction

    NASA Technical Reports Server (NTRS)

    Dunagan, Stephen E.; Brown, James L.; Miles, John B.

    1986-01-01

    An experimental study of the axisymmetric shock-wave / 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 shock wave 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 shock-wave / 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 shock unsteadiness. Comparisons with Navier-Stokes computations using a two-equation turbulence model are presented.

  7. Shock wave-turbulent boundary layer interactions in transonic flow

    NASA Technical Reports Server (NTRS)

    Adamson, T. C., Jr.; Messiter, A. F.

    1976-01-01

    The method of matched asymptotic expansions is used in analyzing the structure of the interaction region formed when a shock wave 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 shock waves. Solutions for the wall shear stress are discussed.

  8. Unsteady Phenomena in Shock Wave/Boundary Layer Interaction

    NASA Technical Reports Server (NTRS)

    Dolling, D. S.

    1993-01-01

    A brief review is given of the unsteadiness of shock wave/turbulent boundary layer interaction. The focus is on interactions generated by swept and unswept compression ramps, by flares, steps and incident shock waves, by cylinders and blunt fins, and by glancing shock waves. 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.

  9. NUCLEOSYNTHETIC LAYERS IN THE SHOCKED EJECTA OF CASSIOPEIA A

    SciTech Connect

    Isensee, Karl; Olmschenk, Greg; Rudnick, Lawrence; DeLaney, Tracey; Rho, Jeonghee; Smith, J. D.; Reach, William T.; Kozasa, Takashi; Gomez, Haley E-mail: larry@astro.umn.edu E-mail: jrho@sofia.usra.edu E-mail: reach@ipac.caltech.edu E-mail: haley.morgan@astro.cf.ac.uk

    2012-10-01

    We present a three-dimensional analysis of the supernova remnant Cassiopeia A using high-resolution spectra from the Spitzer Space Telescope. We observe supernova ejecta both immediately before and during the shock-ejecta interaction. We determine that the reverse shock of the remnant is spherical to within 7%, although the center of this sphere is offset from the geometric center of the remnant by 810 km s{sup -1}. We determine that the velocity width of the nucleosynthetic layers is {approx}1000 km s{sup -1} over 4000 arcsec{sup 2} regions, although the velocity width of a layer along any individual line of sight is <250 km s{sup -1}. Si and O, which come from different nucleosynthetic layers in the progenitor star, are observed to be coincident in velocity space in some directions, but segregated by up to {approx}500 km s{sup -1} in other directions. We compare these observations of the nucleosynthetic layers to predictions from supernova explosion models in an attempt to constrain such models. Finally, we observe small-scale, corrugated velocity structures that are likely caused during the supernova explosion itself, rather than hundreds of years later by dynamical instabilities at the remnant's reverse shock.

  10. Uncertainty Analysis of Air Radiation for Lunar Return Shock Layers

    NASA Technical Reports Server (NTRS)

    Kleb, Bil; Johnston, Christopher O.

    2008-01-01

    By leveraging a new uncertainty markup technique, two risk analysis methods are used to compute the uncertainty of lunar-return shock layer radiation predicted by the High temperature Aerothermodynamic Radiation Algorithm (HARA). The effects of epistemic uncertainty, or uncertainty due to a lack of knowledge, is considered for the following modeling parameters: atomic line oscillator strengths, atomic line Stark broadening widths, atomic photoionization cross sections, negative ion photodetachment cross sections, molecular bands oscillator strengths, and electron impact excitation rates. First, a simplified shock layer problem consisting of two constant-property equilibrium layers is considered. The results of this simplified problem show that the atomic nitrogen oscillator strengths and Stark broadening widths in both the vacuum ultraviolet and infrared spectral regions, along with the negative ion continuum, are the dominant uncertainty contributors. Next, three variable property stagnation-line shock layer cases are analyzed: a typical lunar return case and two Fire II cases. For the near-equilibrium lunar return and Fire 1643-second cases, the resulting uncertainties are very similar to the simplified case. Conversely, the relatively nonequilibrium 1636-second case shows significantly larger influence from electron impact excitation rates of both atoms and molecules. For all cases, the total uncertainty in radiative heat flux to the wall due to epistemic uncertainty in modeling parameters is 30% as opposed to the erroneously-small uncertainty levels (plus or minus 6%) found when treating model parameter uncertainties as aleatory (due to chance) instead of epistemic (due to lack of knowledge).

  11. Subgrid-scale turbulence in shock-boundary layer flows

    NASA Astrophysics Data System (ADS)

    Jammalamadaka, Avinash; Jaberi, Farhad

    2015-04-01

    Data generated by direct numerical simulation (DNS) for a Mach 2.75 zero-pressure gradient turbulent boundary layer interacting with shocks of different intensities are used for a priori analysis of subgrid-scale (SGS) turbulence and various terms in the compressible filtered Navier-Stokes equations. The numerical method used for DNS is based on a hybrid scheme that uses a non-dissipative central scheme in the shock-free turbulent regions and a robust monotonicity-preserving scheme in the shock regions. The behavior of SGS stresses and their components, namely Leonard, Cross and Reynolds components, is examined in various regions of the flow for different shock intensities and filter widths. The backscatter in various regions of the flow is found to be significant only instantaneously, while the ensemble-averaged statistics indicate no significant backscatter. The budgets for the SGS kinetic energy equation are examined for a better understanding of shock-tubulence interactions at the subgrid level and also with the aim of providing useful information for one-equation LES models. A term-by-term analysis of SGS terms in the filtered total energy equation indicate that while each term in this equation is significant by itself, the net contribution by all of them is relatively small. This observation is consistent with our a posteriori analysis.

  12. Experimental studies on two dimensional shock boundary layer interactions

    NASA Technical Reports Server (NTRS)

    Skebe, S. A.; Greber, I.; Hingst, W. R.

    1984-01-01

    Experiments have been performed on the interaction of oblique shock waves with flat plate boundary layers in the 30.48 cm x 30.48 cm (1 ft. x 1 ft.) supersonic wind tunnel at NASA Lewis Research Center. High accuracy measurements of the plate surface static pressure and shear stress distributions as well as boundary layer velocity profiles were obtained through the interaction region. Documentation was also performed of the tunnel test section flow field and of the two-dimensionality of the interaction regions. The findings provide detailed description of two-dimensional interaction with initially laminar boundary layers over the Mach number range 2.0 to 4.0. Additional information with regard to interactions involving initially transitional boundary layers is presented over the Mach number range 2.0 to 3.0 and those for initially turbulent boundary layers at Mach 2.0. These experiments were directed toward providing well documented information of high accuracy useful as test cases for analytic and numerical calculations. Flow conditions encompassed a Reynolds number range of 4.72E6 to 2.95E7 per meter. The shock boundary layer interaction results were found to be generally in good agreement with the experimental work of previous authors both in terms of direct numerical comparison and in support of correlations establishing laminar separation characteristics.

  13. Magnetosheath filamentary structures formed by ion acceleration at the quasi-parallel bow shock

    NASA Astrophysics Data System (ADS)

    Omidi, N.; Sibeck, D.; Gutynska, O.; Trattner, K. J.

    2014-04-01

    Results from 2.5-D electromagnetic hybrid simulations show the formation of field-aligned, filamentary plasma structures in the magnetosheath. They begin at the quasi-parallel bow shock and extend far into the magnetosheath. These structures exhibit anticorrelated, spatial oscillations in plasma density and ion temperature. Closer to the bow shock, magnetic field variations associated with density and temperature oscillations may also be present. Magnetosheath filamentary structures (MFS) form primarily in the quasi-parallel sheath; however, they may extend to the quasi-perpendicular magnetosheath. They occur over a wide range of solar wind Alfvénic Mach numbers and interplanetary magnetic field directions. At lower Mach numbers with lower levels of magnetosheath turbulence, MFS remain highly coherent over large distances. At higher Mach numbers, magnetosheath turbulence decreases the level of coherence. Magnetosheath filamentary structures result from localized ion acceleration at the quasi-parallel bow shock and the injection of energetic ions into the magnetosheath. The localized nature of ion acceleration is tied to the generation of fast magnetosonic waves at and upstream of the quasi-parallel shock. The increased pressure in flux tubes containing the shock accelerated ions results in the depletion of the thermal plasma in these flux tubes and the enhancement of density in flux tubes void of energetic ions. This results in the observed anticorrelation between ion temperature and plasma density.

  14. Magnetosheath Filamentary Structures Formed by Ion Acceleration at the Quasi-Parallel Bow Shock

    NASA Technical Reports Server (NTRS)

    Omidi, N.; Sibeck, D.; Gutynska, O.; Trattner, K. J.

    2014-01-01

    Results from 2.5-D electromagnetic hybrid simulations show the formation of field-aligned, filamentary plasma structures in the magnetosheath. They begin at the quasi-parallel bow shock and extend far into the magnetosheath. These structures exhibit anticorrelated, spatial oscillations in plasma density and ion temperature. Closer to the bow shock, magnetic field variations associated with density and temperature oscillations may also be present. Magnetosheath filamentary structures (MFS) form primarily in the quasi-parallel sheath; however, they may extend to the quasi-perpendicular magnetosheath. They occur over a wide range of solar wind Alfvénic Mach numbers and interplanetary magnetic field directions. At lower Mach numbers with lower levels of magnetosheath turbulence, MFS remain highly coherent over large distances. At higher Mach numbers, magnetosheath turbulence decreases the level of coherence. Magnetosheath filamentary structures result from localized ion acceleration at the quasi-parallel bow shock and the injection of energetic ions into the magnetosheath. The localized nature of ion acceleration is tied to the generation of fast magnetosonic waves at and upstream of the quasi-parallel shock. The increased pressure in flux tubes containing the shock accelerated ions results in the depletion of the thermal plasma in these flux tubes and the enhancement of density in flux tubes void of energetic ions. This results in the observed anticorrelation between ion temperature and plasma density.

  15. Structure of medium Mach number quasi-parallel shocks - Upstream and downstream waves

    NASA Technical Reports Server (NTRS)

    Krauss-Varban, D.; Omidi, N.

    1991-01-01

    The transition from steady low-Mach-number to unsteady high-Mach-number quasi-parallel shocks was investigated by performing large-scale 1D hybrid code simulations at increasing Mach numbers. It was found that only at very low Mach number shocks the steepening is limited by upstream phase-standing whistlers, as predicted by the classical theory (Tidman and Northrop, 1968). In the intermediate region of Mach numbers between 1.5 and 3.5, a very diverse behavior is observed. Backstreaming ions generate fast magnetosonic waves which dominate the upstream, with wavelengths longer than phase-standing whistlers. At increasing Mach numbers, the phase and group velocities of the dominant waves are reduced until they point back toward the shock; when there is sufficient energy flux in these waves, they lead to unsteady shock behavior and eventually to shock reformation.

  16. Post-adiabatic supernova remnants in an interstellar magnetic field: parallel and perpendicular shocks

    NASA Astrophysics Data System (ADS)

    Petruk, O.; Kuzyo, T.; Beshley, V.

    2016-03-01

    Gamma-rays from hadronic collisions are expected from supernova remnants (SNRs) located near molecular clouds. The temperature of the shock interacting with the dense environment quickly reaches 105 K. Radiative losses of plasma become essential in the evolution of SNRs. They decrease the thermal pressure and essentially increase the density behind the shock. The presence of an ambient magnetic field may alter the behaviour of the post-adiabatic SNRs considerably compared with the hydrodynamic scenario. In the present article, magnetohydrodynamic simulations of radiative shocks in a magnetic field are performed. High plasma compression due to radiative losses also results in a prominent increase in the strength of the tangential component of magnetic field behind the shock and a decrease of the parallel one. If the strength of the tangential field before the shock is higher than about 3 μG, it prevents formation of a very dense thin shell. The higher the strength of the tangential magnetic field, the larger the thickness and the lower the maximum density in the radiative shell. The parallel magnetic field does not affect the distribution of the hydrodynamic parameters behind the shock. There are almost independent channels of energy transformations: radiative losses are due to thermal energy, magnetic energy increases come from reducing the kinetic energy. The large density and high strength of the perpendicular magnetic field in the radiative shells of SNRs should result in a considerable increase of the hadronic gamma-ray flux compared with the leptonic one.

  17. Energetic particle diffusion coefficients upstream of quasi-parallel interplanetary shocks

    NASA Technical Reports Server (NTRS)

    Tan, L. C.; Mason, G. M.; Gloeckler, G.; Ipavich, F. M.

    1989-01-01

    The properties of about 30 to 130-keV/e protons and alpha particles upstream of six quasi-parallel interplanetary shocks that passed by the ISEE 3 spacecraft during 1978-1979 were analyzed, and the values for the upstream energegic particle diffusion coefficient, kappa, in these six events were deduced for a number of energies and upstream positions. These observations were compared with predictions of Lee's (1983) theory of shock acceleration. It was found that the observations verified the prediction of the A/Q dependence (where A and Q are the particle atomic mass and ionization state, respectively) of kappa for alpha and proton particles upstream of the quasi-parallel shocks.

  18. Stability and modal analysis of shock/boundary layer interactions

    NASA Astrophysics Data System (ADS)

    Nichols, Joseph W.; Larsson, Johan; Bernardini, Matteo; Pirozzoli, Sergio

    2016-06-01

    The dynamics of oblique shock wave/turbulent boundary layer interactions is analyzed by mining a large-eddy simulation (LES) database for various strengths of the incoming shock. The flow dynamics is first analyzed by means of dynamic mode decomposition (DMD), which highlights the simultaneous occurrence of two types of flow modes, namely a low-frequency type associated with breathing motion of the separation bubble, accompanied by flapping motion of the reflected shock, and a high-frequency type associated with the propagation of instability waves past the interaction zone. Global linear stability analysis performed on the mean LES flow fields yields a single unstable zero-frequency mode, plus a variety of marginally stable low-frequency modes whose stability margin decreases with the strength of the interaction. The least stable linear modes are grouped into two classes, one of which bears striking resemblance to the breathing mode recovered from DMD and another class associated with revolving motion within the separation bubble. The results of the modal and linear stability analysis support the notion that low-frequency dynamics is intrinsic to the interaction zone, but some continuous forcing from the upstream boundary layer may be required to keep the system near a limit cycle. This can be modeled as a weakly damped oscillator with forcing, as in the early empirical model by Plotkin (AIAA J 13:1036-1040, 1975).

  19. DSMC Computations for Regions of Shock/Shock and Shock/Boundary Layer Interaction

    NASA Technical Reports Server (NTRS)

    Moss, James N.

    2001-01-01

    This paper presents the results of a numerical study of hypersonic interacting flows at flow conditions that include those for which experiments have been conducted in the Calspan-University of Buffalo Research Center (CUBRC) Large Energy National Shock (LENS) tunnel and the ONERA R5Ch low-density wind tunnel. The computations are made with the direct simulation Monte Carlo (DSMC) method of Bird. The focus is on Mach 9.3 to 11.4 flows about flared axisymmetric configurations, both hollow cylinder flares and double cones. The results presented highlight the sensitivity of the calculations to grid resolution, provide results concerning the conditions for incipient separation, and provide information concerning the flow structure and surface results for the extent of separation, heating, pressure, and skin friction.

  20. Spontaneous hot flow anomalies at quasi-parallel shocks: 2. Hybrid simulations

    NASA Astrophysics Data System (ADS)

    Omidi, N.; Zhang, H.; Sibeck, D.; Turner, D.

    2013-01-01

    Abstract<p label="1">Motivated by recent THEMIS observations, this paper uses 2.5-D electromagnetic hybrid simulations to investigate the formation of Spontaneous Hot Flow Anomalies (SHFAs) upstream of quasi-<span class="hlt">parallel</span> bow <span class="hlt">shocks</span> during steady solar wind conditions and in the absence of discontinuities. The results show the formation of a large number of structures along and upstream of the quasi-<span class="hlt">parallel</span> bow <span class="hlt">shock</span>. Their outer edges exhibit density and magnetic field enhancements, while their cores exhibit drops in density, magnetic field, solar wind velocity, and enhancements in ion temperature. Using virtual spacecraft in the simulation, we show that the signatures of these structures in the time series data are very similar to those of SHFAs seen in THEMIS data and conclude that they correspond to SHFAs. Examination of the simulation data shows that SHFAs form as the result of foreshock cavitons interacting with the bow <span class="hlt">shock</span>. Foreshock cavitons in turn form due to the nonlinear evolution of ULF waves generated by the interaction of the solar wind with the backstreaming ions. Because foreshock cavitons are an inherent part of the <span class="hlt">shock</span> dissipation process, the formation of SHFAs is also an inherent part of the dissipation process leading to a highly nonuniform plasma in the quasi-<span class="hlt">parallel</span> magnetosheath including large-scale density and magnetic field cavities.</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_1");'>1</a></li> <li><a href="#" onclick='return showDiv("page_2");'>2</a></li> <li class="active"><span>3</span></li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_13");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_3 --> <div id="page_4" 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_2");'>2</a></li> <li><a href="#" onclick='return showDiv("page_3");'>3</a></li> <li class="active"><span>4</span></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_13");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="61"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20150007957','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20150007957"><span id="translatedtitle">Spontaneous Hot Flow Anomalies at Quasi-<span class="hlt">Parallel</span> <span class="hlt">Shocks</span>: 2. Hybrid Simulations</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Omidi, N.; Zhang, H.; Sibeck, D.; Turner, D.</p> <p>2013-01-01</p> <p>Motivated by recent THEMIS observations, this paper uses 2.5-D electromagnetic hybrid simulations to investigate the formation of Spontaneous Hot Flow Anomalies (SHFA) upstream of quasi-<span class="hlt">parallel</span> bow <span class="hlt">shocks</span> during steady solar wind conditions and in the absence of discontinuities. The results show the formation of a large number of structures along and upstream of the quasi-<span class="hlt">parallel</span> bow <span class="hlt">shock</span>. Their outer edges exhibit density and magnetic field enhancements, while their cores exhibit drops in density, magnetic field, solar wind velocity and enhancements in ion temperature. Using virtual spacecraft in the simulation, we show that the signatures of these structures in the time series data are very similar to those of SHFAs seen in THEMIS data and conclude that they correspond to SHFAs. Examination of the simulation data shows that SHFAs form as the result of foreshock cavitons interacting with the bow <span class="hlt">shock</span>. Foreshock cavitons in turn form due to the nonlinear evolution of ULF waves generated by the interaction of the solar wind with the backstreaming ions. Because foreshock cavitons are an inherent part of the <span class="hlt">shock</span> dissipation process, the formation of SHFAs is also an inherent part of the dissipation process leading to a highly non-uniform plasma in the quasi-<span class="hlt">parallel</span> magnetosheath including large scale density and magnetic field cavities.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19930071070&hterms=future+transport+speed&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dfuture%2Btransport%2Bspeed','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19930071070&hterms=future+transport+speed&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dfuture%2Btransport%2Bspeed"><span id="translatedtitle">Alfven wave transport effects in the time evolution of <span class="hlt">parallel</span> cosmic-ray-modified <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>Jones, T. W.</p> <p>1993-01-01</p> <p>This paper presents a numerical study of the time evolution of plane, cosmic-ray modified <span class="hlt">shocks</span> with magnetic field <span class="hlt">parallel</span> to the <span class="hlt">shock</span> normal, based on the diffusive <span class="hlt">shock</span> acceleration formalism and including the effects from the finite propagation speed and energy of Alfven waves responsible for controlling the transport of the cosmic rays. The simulations discussed are based on a three-fluid model for the dynamics, but a more complete formalism is laid out for future work. The results of the simulations confirm earlier steady state analyses that found these Alfven transport effects to be potentially important when the upstream Alfven speed and the gas sound speed are comparable, i.e., when the plasma and magnetic pressures are similar. It is also clear, however, that the impact of Alfven transport effects, which tend to slow <span class="hlt">shock</span> evolution and reduce the time asymptotic cosmic-ray pressure in the <span class="hlt">shock</span>, is strongly dependent upon uncertain details in the transport models. Both cosmic-ray advection tied to streaming Alfven waves and dissipation of wave energy are important to include in the models. Further, Alfven transport properties on both sides of the <span class="hlt">shock</span> are also influential.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19930092322','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19930092322"><span id="translatedtitle">Attenuation in a <span class="hlt">shock</span> tube due to unsteady-boundary-<span class="hlt">layer</span> action</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Mirels, Harold</p> <p>1957-01-01</p> <p>A method is presented for obtaining the attenuation of a <span class="hlt">shock</span> wave in a <span class="hlt">shock</span> tube due to the unsteady boundary <span class="hlt">layer</span> along the <span class="hlt">shock</span>-tube walls. It is assumed that the boundary <span class="hlt">layer</span> is thin relative to the tube diameter and induces one-dimensional longitudinal pressure waves whose strength is proportional to the vertical velocity at the edge of the boundary <span class="hlt">layer</span>. The contributions of the various regions in a <span class="hlt">shock</span> tube to <span class="hlt">shock</span> attenuation are indicated. The method is shown to be in reasonably good agreement with existing experimental data.</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-<span class="hlt">parallel</span> <span class="hlt">shock</span> waves 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> waves 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-<span class="hlt">parallel</span>, 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 reflected and accelerated. Thus, thermal electrons gain energy due to multiple reflections 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://hdl.handle.net/2060/19770015092','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19770015092"><span id="translatedtitle">Structure of a quasi-<span class="hlt">parallel</span>, quasi-laminar 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>Greenstadt, E. W.; Russell, C. T.; Formisano, V.; Hedgecock, P. C.; Scarf, F. L.; Neugebauer, M.; Holzer, R. E.</p> <p>1976-01-01</p> <p>A thick, quasi-<span class="hlt">parallel</span> bow <span class="hlt">shock</span> structure was observed with field and particle detectors of both HEOS 1 and OGO 5. The typical magnetic pulsation structure was at least 1 to 2 earth radii thick radially and was accompanied by irregular but distinct plasma distributions characteristic of neither the solar wind nor the magnetosheath. Waves constituting the large pulsations were polarized principally in the plane of the nominal <span class="hlt">shock</span>, therefore also in the plane perpendicular to the average interplanetary field. A separate interpulsation regime detected between bursts of large amplitude oscillations was similar to the upstream wave region magnetically, but was characterized by disturbed plasma flux and enhanced noise around the ion plasma frequency. The <span class="hlt">shock</span> structure appeared to be largely of an oblique, whistler type, probably complicated by counterstreaming high energy protons. Evidence for firehose instability-based structure was weak at best and probably negative.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22140247','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22140247"><span id="translatedtitle">GYROSURFING ACCELERATION OF IONS IN FRONT OF EARTH's QUASI-<span class="hlt">PARALLEL</span> BOW <span class="hlt">SHOCK</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Kis, Arpad; Lemperger, Istvan; Wesztergom, Viktor; Agapitov, Oleksiy; Krasnoselskikh, Vladimir; Dandouras, Iannis E-mail: Kis.Arpad@csfk.mta.hu</p> <p>2013-07-01</p> <p>It is well known that <span class="hlt">shocks</span> in space plasmas can accelerate particles to high energies. However, many details of the <span class="hlt">shock</span> acceleration mechanism are still unknown. A critical element of <span class="hlt">shock</span> acceleration is the injection problem; i.e., the presence of the so called seed particle population that is needed for the acceleration to work efficiently. In our case study, we present for the first time observational evidence of gyroresonant surfing acceleration in front of Earth's quasi-<span class="hlt">parallel</span> bow <span class="hlt">shock</span> resulting in the appearance of the long-suspected seed particle population. For our analysis, we use simultaneous multi-spacecraft measurements provided by the Cluster spacecraft ion (CIS), magnetic (FGM), and electric field and wave instrument (EFW) during a time period of large inter-spacecraft separation distance. The spacecraft were moving toward the bow <span class="hlt">shock</span> and were situated in the foreshock region. The results show that the gyroresonance surfing acceleration takes place as a consequence of interaction between circularly polarized monochromatic (or quasi-monochromatic) transversal electromagnetic plasma waves and short large amplitude magnetic structures (SLAMSs). The magnetic mirror force of the SLAMS provides the resonant conditions for the ions trapped by the waves and results in the acceleration of ions. Since wave packets with circular polarization and different kinds of magnetic structures are very commonly observed in front of Earth's quasi-<span class="hlt">parallel</span> bow <span class="hlt">shock</span>, the gyroresonant surfing acceleration proves to be an important particle injection mechanism. We also show that seed ions are accelerated directly from the solar wind ion population.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013ApJ...771....4K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013ApJ...771....4K"><span id="translatedtitle">Gyrosurfing Acceleration of Ions in Front of Earth's Quasi-<span class="hlt">parallel</span> 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>Kis, Arpad; Agapitov, Oleksiy; Krasnoselskikh, Vladimir; Khotyaintsev, Yuri V.; Dandouras, Iannis; Lemperger, Istvan; Wesztergom, Viktor</p> <p>2013-07-01</p> <p>It is well known that <span class="hlt">shocks</span> in space plasmas can accelerate particles to high energies. However, many details of the <span class="hlt">shock</span> acceleration mechanism are still unknown. A critical element of <span class="hlt">shock</span> acceleration is the injection problem; i.e., the presence of the so called seed particle population that is needed for the acceleration to work efficiently. In our case study, we present for the first time observational evidence of gyroresonant surfing acceleration in front of Earth's quasi-<span class="hlt">parallel</span> bow <span class="hlt">shock</span> resulting in the appearance of the long-suspected seed particle population. For our analysis, we use simultaneous multi-spacecraft measurements provided by the Cluster spacecraft ion (CIS), magnetic (FGM), and electric field and wave instrument (EFW) during a time period of large inter-spacecraft separation distance. The spacecraft were moving toward the bow <span class="hlt">shock</span> and were situated in the foreshock region. The results show that the gyroresonance surfing acceleration takes place as a consequence of interaction between circularly polarized monochromatic (or quasi-monochromatic) transversal electromagnetic plasma waves and short large amplitude magnetic structures (SLAMSs). The magnetic mirror force of the SLAMS provides the resonant conditions for the ions trapped by the waves and results in the acceleration of ions. Since wave packets with circular polarization and different kinds of magnetic structures are very commonly observed in front of Earth's quasi-<span class="hlt">parallel</span> bow <span class="hlt">shock</span>, the gyroresonant surfing acceleration proves to be an important particle injection mechanism. We also show that seed ions are accelerated directly from the solar wind ion population.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19930061252&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=19930061252&hterms=downstream&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Ddownstream"><span id="translatedtitle">Propagation characteristics of waves upstream and downstream of quasi-<span class="hlt">parallel</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>Krauss-Varban, D.; Omidi, N.</p> <p>1993-01-01</p> <p>The propagation characteristics of waves upstream and downstream of quasi-<span class="hlt">parallel</span> <span class="hlt">shocks</span> are investigated by using 2D hybrid simulations. At low Alfven Mach numbers, M(A) below about 2, the <span class="hlt">shock</span> is initially associated with upstream phase-standing whistlers. At later times, backstreaming ions excite longer-wavelength whistlers via the right-hand resonant ion/ion instability. These waves propagate along the magnetic field at a group velocity no smaller than the upstream flow speed, so that the waves remain in the upstream region. At higher MA (above about 3), these waves are convected back into the <span class="hlt">shock</span>, causing its reformation and downstream perturbations. <span class="hlt">Shock</span> transmitted waves mode-convert into Alfven/ion-cyclotron waves which have a wave vector along the <span class="hlt">shock</span> normal (pointing upstream) and convect downstream. The 2D simulation results confirm our earlier suggestion that the upstream waves should be field aligned, and that their convection into the downstream is associated with linear mode conversion into the Alfven/ion-cyclotron branch.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/101967','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/101967"><span id="translatedtitle">Hypersonic hydrogen combustion in the thin viscous <span class="hlt">shock</span> <span class="hlt">layer</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Riabov, V.V.; Botin, A.V.</p> <p>1995-04-01</p> <p>Different models of hypersonic diffusive hydrogen combustion in a thin viscous <span class="hlt">shock</span> <span class="hlt">layer</span> (TVSL) at moderate Reynolds numbers have been developed. The study is based on computations of nonequilibrium multicomponent flowfield parameters of air-hydrogen mixture in the TVSL near the blunt probe. The structure of computed combustion zones is analyzed. Under conditions of slot and uniform injections the zone structures are essentially different. Hydrogen injection conditions are discovered at which the nonreacting hydrogen zone and the zone enriched with the hydrogen combustion products appear near the body surface. Hydrogen, water, and OH concentrations identify these zones. More effective cooling of the probe surface occurs at moderate injections compared to strong ones. Under the blowing conditions at moderate Reynolds numbers the most effective cooling of the body surface occurs at moderate uniform hydrogen injection. The results can be helpful for predicting the degree of supersonic hydrogen combustion in hypersonic vehicle engines. 21 refs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19740021535','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19740021535"><span id="translatedtitle"><span class="hlt">Shock</span>-induced separation of adiabatic turbulent boundary <span class="hlt">layers</span> in supersonic axially symmetric internal flow</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Page, R. J.; Childs, M. E.</p> <p>1974-01-01</p> <p>An experimental investigation at Mach 4 of <span class="hlt">shock</span>-induced turbulent boundary <span class="hlt">layer</span> separation at the walls of axially symmetric flow passages is discussed, with particular emphasis placed on determining the <span class="hlt">shock</span> strengths required for incipient separation. The <span class="hlt">shock</span> waves were produced by interchangeable sting-mounted cones placed on the axes of the flow passages and aligned with the freestream flow. The interactions under study simulate those encountered in axially symmetric engine inlets of supersonic aircraft. Knowledges of the <span class="hlt">shock</span> strengths required for boundary <span class="hlt">layer</span> separation in inlets is important since for <span class="hlt">shocks</span> of somewhat greater strength rather drastic alterations in the inlet flow field may occur.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22046893','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22046893"><span id="translatedtitle">Evolution of symmetric reconnection <span class="hlt">layer</span> in the presence of <span class="hlt">parallel</span> shear flow</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Lu Haoyu; Cao Jinbin</p> <p>2011-07-15</p> <p>The development of the structure of symmetric reconnection <span class="hlt">layer</span> in the presence of a shear flow <span class="hlt">parallel</span> to the antiparallel magnetic field component is studied by using a set of one-dimensional (1D) magnetohydrodynamic (MHD) equations. The Riemann problem is simulated through a second-order conservative TVD (total variation diminishing) scheme, in conjunction with Roe's averages for the Riemann problem. The simulation results indicate that besides the MHD <span class="hlt">shocks</span> and expansion waves, there exist some new small-scale structures in the reconnection <span class="hlt">layer</span>. For the case of zero initial guide magnetic field (i.e., B{sub y0} = 0), a pair of intermediate <span class="hlt">shock</span> and slow <span class="hlt">shock</span> (SS) is formed in the presence of the <span class="hlt">parallel</span> shear flow. The critical velocity of initial shear flow V{sub zc} is just the Alfven velocity in the inflow region. As V{sub z{infinity}} increases to the value larger than V{sub zc}, a new slow expansion wave appears in the position of SS in the case V{sub z{infinity}} < V{sub zc}, and one of the current densities drops to zero. As plasma {beta} increases, the out-flow region is widened. For B{sub y0} {ne} 0, a pair of SSs and an additional pair of time-dependent intermediate <span class="hlt">shocks</span> (TDISs) are found to be present. Similar to the case of B{sub y0} = 0, there exists a critical velocity of initial shear flow V{sub zc}. The value of V{sub zc} is, however, smaller than the Alfven velocity of the inflow region. As plasma {beta} increases, the velocities of SS and TDIS increase, and the out-flow region is widened. However, the velocity of downstream SS increases even faster, making the distance between SS and TDIS smaller. Consequently, the interaction between SS and TDIS in the case of high plasma {beta} influences the property of direction rotation of magnetic field across TDIS. Thereby, a wedge in the hodogram of tangential magnetic field comes into being. When {beta}{yields}{infinity}, TDISs disappear and the guide magnetic field becomes constant.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20110023251','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20110023251"><span id="translatedtitle">Turbulence Modeling for <span class="hlt">Shock</span> Wave/Turbulent Boundary <span class="hlt">Layer</span> Interactions</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Lillard, Randolph P.</p> <p>2011-01-01</p> <p>Accurate aerodynamic computational predictions are essential for the safety of space vehicles, but these computations are of limited accuracy when large pressure gradients are present in the flow. The goal of the current project is to improve the state of compressible turbulence modeling for high speed flows with <span class="hlt">shock</span> wave / turbulent boundary <span class="hlt">layer</span> interactions (SWTBLI). Emphasis will be placed on models that can accurately predict the separated region caused by the SWTBLI. These flows are classified as nonequilibrium boundary <span class="hlt">layers</span> because of the very large and variable adverse pressure gradients caused by the <span class="hlt">shock</span> waves. The lag model was designed to model these nonequilibrium flows by incorporating history effects. Standard one- and two-equation models (Spalart Allmaras and SST) and the lag model will be run and compared to a new lag model. This new model, the Reynolds stress tensor lag model (lagRST), will be assessed against multiple wind tunnel tests and correlations. The basis of the lag and lagRST models are to preserve the accuracy of the standard turbulence models in equilibrium turbulence, when the Reynolds stresses are linearly related to the mean strain rates, but create a lag between mean strain rate effects and turbulence when nonequilibrium effects become important, such as in large pressure gradients. The affect this lag has on the results for SWBLI and massively separated flows will be determined. These computations will be done with a modified version of the OVERFLOW code. This code solves the RANS equations on overset grids. It was used for this study for its ability to input very complex geometries into the flow solver, such as the Space Shuttle in the full stack configuration. The model was successfully implemented within two versions of the OVERFLOW code. Results show a substantial improvement over the baseline models for transonic separated flows. The results are mixed for the SWBLI assessed. Separation predictions are not as good as the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22492653','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22492653"><span id="translatedtitle">Propagation of acoustic <span class="hlt">shock</span> waves between <span class="hlt">parallel</span> rigid boundaries and into shadow zones</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Desjouy, C. Ollivier, S.; Dragna, D.; Blanc-Benon, P.; Marsden, O.</p> <p>2015-10-28</p> <p>The study of acoustic <span class="hlt">shock</span> 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 <span class="hlt">shocks</span>, laboratory-scale experiments and numerical simulations were performed to study the propagation of weak <span class="hlt">shock</span> waves between <span class="hlt">parallel</span> 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 <span class="hlt">shock</span> 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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AIPC.1685i0001D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AIPC.1685i0001D"><span id="translatedtitle">Propagation of acoustic <span class="hlt">shock</span> waves between <span class="hlt">parallel</span> rigid boundaries and into shadow zones</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Desjouy, C.; Ollivier, S.; Marsden, O.; Dragna, D.; Blanc-Benon, P.</p> <p>2015-10-01</p> <p>The study of acoustic <span class="hlt">shock</span> 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 <span class="hlt">shocks</span>, laboratory-scale experiments and numerical simulations were performed to study the propagation of weak <span class="hlt">shock</span> waves between <span class="hlt">parallel</span> 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 <span class="hlt">shock</span> 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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19880059402&hterms=downstream&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Ddownstream','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19880059402&hterms=downstream&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Ddownstream"><span id="translatedtitle">Downstream energetic proton and alpha particles during quasi-<span class="hlt">parallel</span> interplanetary <span class="hlt">shock</span> events</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Tan, L. C.; Mason, G. M.; Gloeckler, G.; Ipavich, F. M.</p> <p>1988-01-01</p> <p>This paper considers the energetic particle populations in the downstream region of three quasi-<span class="hlt">parallel</span> interplanetary <span class="hlt">shock</span> events, which was explored using the ISEE 3 Ultra Low Energy Charge Analyzer sensor, which unambiguously identifies protons and alpha particles using the electrostatic deflection versus residual energy technique. The downstream particles were found to exhibit anisotropies due largely to convection in the solar wind. The spectral indices of the proton and the alpha-particle distribution functions were found to be remarkably constant during the downstream period, being generally insensitive to changes in particle flux levels, magnetic field direction, and solar wind densities. In two of the three events, the proton and the alpha spectra were the same throughout the entire downstream period, supporting the prediction of diffusive <span class="hlt">shock</span> acceleration theory.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19770040368&hterms=Irregular+Structure&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3DIrregular%2BStructure','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19770040368&hterms=Irregular+Structure&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3DIrregular%2BStructure"><span id="translatedtitle">Structure of a quasi-<span class="hlt">parallel</span>, quasi-laminar 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>Greenstadt, E. W.; Scarf, F. L.; Russell, C. T.; Holzer, R. E.; Formisano, V.; Hedgecock, P. C.; Neugebauer, M.</p> <p>1977-01-01</p> <p>A thick quasi-<span class="hlt">parallel</span> bow <span class="hlt">shock</span> structure was observed on February 14, 1969, with field and particle detectors of both Heos 1 and Ogo 5. The typical magnetic pulsation structure was at least 1-2 R-E thick radially and was accompanied by irregular but distinct (average) plasma distributions characteristic of neither the solar wind nor the magnetosheath. There appeared to be a separate 'interpulsation' regime occurring between bursts of large amplitude oscillations. This regime was magnetically similar to the upstream wave region but was characterized by disturbed plasma flux and enhanced noise around the ion plasma frequency. The <span class="hlt">shock</span> structure appeared to be largely of an oblique whistler type, probably complicated by counterstreaming high-energy protons.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20090033728','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20090033728"><span id="translatedtitle"><span class="hlt">Shock</span> <span class="hlt">Layer</span> Radiation Measurements and Analysis for Mars Entry</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Bose, Deepak; Grinstead, Jay Henderson; Bogdanoff, David W.; Wright, Michael J.</p> <p>2009-01-01</p> <p>NASA's In-Space Propulsion program is supporting the development of <span class="hlt">shock</span> radiation transport models for aerocapture missions to Mars. A comprehensive test series in the NASA Antes Electric Arc <span class="hlt">Shock</span> Tube facility at a representative flight condition was recently completed. The facility optical instrumentation enabled spectral measurements of <span class="hlt">shocked</span> gas radiation from the vacuum ultraviolet to the near infrared. The instrumentation captured the nonequilibrium post-<span class="hlt">shock</span> excitation and relaxation dynamics of dispersed spectral features. A description of the <span class="hlt">shock</span> tube facility, optical instrumentation, and examples of the test data are presented. Comparisons of measured spectra with model predictions are also made.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19760002932','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19760002932"><span id="translatedtitle">Calculation of <span class="hlt">shock</span>-separated turbulent boundary <span class="hlt">layers</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Baldwin, B. S.; Rose, W. C.</p> <p>1975-01-01</p> <p>Numerical solutions of the complete, time-averaged conservation equations using several eddy-viscosity models for the Reynolds shear stress to close the equations are compared with experimental measurements in a compressible, turbulent separated flow. An efficient time-splitting, explicit difference scheme was used to solve the two-dimensional conservation equations. The experiment used for comparison was a turbulent boundary <span class="hlt">layer</span> that was separated by an incident <span class="hlt">shock</span> wave in a Mach 2.93 flow with a unit Reynolds number of 5.7 x 10 to the seventh power m. Comparisons of predicted and experimental values of surface pressure, shear stress along the wall, and velocity profiles are shown. One of the tested eddy-viscosity models which allows the shear stress to be out of equilibrium with the mean flow produces substantially better agreement with the experimental measurements than the simpler models. A tool is thereby provided for inferring additional information about the flow, such as static pressures in the stream, which might not be directly obtainable from experiments.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/10170379','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/10170379"><span id="translatedtitle">Nexus: An interoperability <span class="hlt">layer</span> for <span class="hlt">parallel</span> and distributed computer systems</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Foster, I.; Kesselman, C.; Olson, R.; Tuecke, S.</p> <p>1994-05-01</p> <p>Nexus is a set of services that can be used to implement various task-<span class="hlt">parallel</span> languages, data-<span class="hlt">parallel</span> languages, and message-passing libraries. Nexus is designed to permit the efficient portable implementation of individual <span class="hlt">parallel</span> programming systems and the interoperability of programs developed with different tools. Nexus supports lightweight threading and active message technology, allowing integration of message passing and threads.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20140005333','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20140005333"><span id="translatedtitle"><span class="hlt">Shock</span> <span class="hlt">Layer</span> Radiation Modeling and Uncertainty for Mars Entry</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Johnston, Christopher O.; Brandis, Aaron M.; Sutton, Kenneth</p> <p>2012-01-01</p> <p>A model for simulating nonequilibrium radiation from Mars entry <span class="hlt">shock</span> <span class="hlt">layers</span> is presented. A new chemical kinetic rate model is developed that provides good agreement with recent EAST and X2 <span class="hlt">shock</span> tube radiation measurements. This model includes a CO dissociation rate that is a factor of 13 larger than the rate used widely in previous models. Uncertainties in the proposed rates are assessed along with uncertainties in translational-vibrational relaxation modeling parameters. The stagnation point radiative flux uncertainty due to these flowfield modeling parameter uncertainties is computed to vary from 50 to 200% for a range of free-stream conditions, with densities ranging from 5e-5 to 5e-4 kg/m3 and velocities ranging from of 6.3 to 7.7 km/s. These conditions cover the range of anticipated peak radiative heating conditions for proposed hypersonic inflatable aerodynamic decelerators (HIADs). Modeling parameters for the radiative spectrum are compiled along with a non-Boltzmann rate model for the dominant radiating molecules, CO, CN, and C2. A method for treating non-local absorption in the non-Boltzmann model is developed, which is shown to result in up to a 50% increase in the radiative flux through absorption by the CO 4th Positive band. The sensitivity of the radiative flux to the radiation modeling parameters is presented and the uncertainty for each parameter is assessed. The stagnation point radiative flux uncertainty due to these radiation modeling parameter uncertainties is computed to vary from 18 to 167% for the considered range of free-stream conditions. The total radiative flux uncertainty is computed as the root sum square of the flowfield and radiation parametric uncertainties, which results in total uncertainties ranging from 50 to 260%. The main contributors to these significant uncertainties are the CO dissociation rate and the CO heavy-particle excitation rates. Applying the baseline flowfield and radiation models developed in this work, the</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_2");'>2</a></li> <li><a href="#" onclick='return showDiv("page_3");'>3</a></li> <li class="active"><span>4</span></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_13");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_4 --> <div id="page_5" 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_3");'>3</a></li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li class="active"><span>5</span></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_13");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="81"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016AIPC.1759b0102S&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016AIPC.1759b0102S&link_type=ABSTRACT"><span id="translatedtitle">Simulation of <span class="hlt">shock</span> wave boundary <span class="hlt">layer</span> interaction in flat channel with jet injection</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Shakhan, Nurtoleu; Beketaeva, Asel; Naimanova, Altynshash</p> <p>2016-08-01</p> <p>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 <span class="hlt">shock</span>-wave structures are observed: in the region of the jet (barrel, bow, oblique and closing <span class="hlt">shocks</span>), on the upper boundary <span class="hlt">layer</span> (reflection, transmitted and reattachment <span class="hlt">shocks</span>), and new structures behind the jet on the lower boundary <span class="hlt">layer</span>, which are analogous to the structures on the upper boundary <span class="hlt">layer</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JGRA..121.2080H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JGRA..121.2080H"><span id="translatedtitle">Formation of downstream high-speed jets by a rippled nonstationary quasi-<span class="hlt">parallel</span> <span class="hlt">shock</span>: 2-D hybrid simulations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hao, Y.; Lembege, B.; Lu, Q.; Guo, F.</p> <p>2016-03-01</p> <p>Experimental observations from space missions (including more recently Cluster and Time History of Events and Macroscale Interactions during Substorms data) have clearly revealed the existence of high-speed jets (HSJs) in the downstream region of the quasi-<span class="hlt">parallel</span> terrestrial bow <span class="hlt">shock</span>. Presently, two-dimensional hybrid simulations are performed in order to investigate the formation of such HSJs through a rippled quasi-<span class="hlt">parallel</span> <span class="hlt">shock</span> front. The simulation results show that (i) such <span class="hlt">shock</span> fronts are strongly nonstationary along the <span class="hlt">shock</span> normal, and (ii) ripples are evidenced along the <span class="hlt">shock</span> front as the upstream ULF waves (excited by interaction between incident and reflected ions) are convected back to the front by the solar wind and contribute to the rippling formation. Then, these ripples are inherent structures of a quasi-<span class="hlt">parallel</span> <span class="hlt">shock</span>. As a consequence, new incident solar wind ions interact differently at different locations along the <span class="hlt">shock</span> surface, and the ion bulk velocity strongly differs locally as ions are transmitted downstream. Preliminary results show that (i) local bursty patterns of turbulent magnetic field may form within the rippled front and play the role of local secondary <span class="hlt">shock</span>; (ii) some incident ion flows penetrate the front, suffer some deflection (instead of being decelerated) at the locations of these secondary <span class="hlt">shocks</span>, and are at the origin of well-structured (filamentary) HSJs downstream; and (iii) the spatial scales of HSJs are in a good agreement with experimental observations. Such downstream HSJs are shown to be generated by local curvature effects (front rippling) and the nonstationarity of the <span class="hlt">shock</span> front itself.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/441343','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/441343"><span id="translatedtitle">Interaction of a plane <span class="hlt">shock</span> wave in water with a thin <span class="hlt">layer</span> of lower density</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Bergel`son, V.I.; Nemchinov, I.V.; Orlova, T.I.; Khazins, V.M.</p> <p>1992-08-01</p> <p>A numerical analysis is conducted on the interaction of a plane <span class="hlt">shock</span> wave in water with a thin <span class="hlt">layer</span> of lower density, which is perpendicular to the wave front. Parameters are defined for the perturbed flow structure and for large-scale precursors, which arise ahead of the <span class="hlt">shock</span> front. Possibilities are discussed of experimentally investigating this phenomena with a cylindrical <span class="hlt">shock</span> wave using standard explosives. 4 refs., 4 figs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014PhPl...21b2101M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014PhPl...21b2101M"><span id="translatedtitle"><span class="hlt">Shock</span> waves and double <span class="hlt">layers</span> in electron degenerate dense plasma with viscous ion fluids</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mamun, A. A.; Zobaer, M. S.</p> <p>2014-02-01</p> <p>The properties of ion-acoustic <span class="hlt">shock</span> waves and double <span class="hlt">layers</span> propagating in a viscous degenerate dense plasma (containing inertial viscous ion fluid, non-relativistic and ultra-relativistic degenerate electron fluid, and negatively charged stationary heavy element) is investigated. A new nonlinear equation (viz. Gardner equation with additional dissipative term) is derived by the reductive perturbation method. The properties of the ion-acoustic <span class="hlt">shock</span> waves and double <span class="hlt">layers</span> are examined by the analysis of the <span class="hlt">shock</span> and double <span class="hlt">layer</span> solutions of this new equation (we would like to call it "M-Z equation"). It is found that the properties of these <span class="hlt">shock</span> and double <span class="hlt">layer</span> structures obtained from this analysis are significantly different from those obtained from the analysis of standard Gardner or Burgers' equation. The implications of our results to dense plasmas in astrophysical objects (e.g., non-rotating white dwarf stars) are briefly discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22252111','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22252111"><span id="translatedtitle"><span class="hlt">Shock</span> waves and double <span class="hlt">layers</span> in electron degenerate dense plasma with viscous ion fluids</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Mamun, A. A.; Zobaer, M. S.</p> <p>2014-02-15</p> <p>The properties of ion-acoustic <span class="hlt">shock</span> waves and double <span class="hlt">layers</span> propagating in a viscous degenerate dense plasma (containing inertial viscous ion fluid, non-relativistic and ultra-relativistic degenerate electron fluid, and negatively charged stationary heavy element) is investigated. A new nonlinear equation (viz. Gardner equation with additional dissipative term) is derived by the reductive perturbation method. The properties of the ion-acoustic <span class="hlt">shock</span> waves and double <span class="hlt">layers</span> are examined by the analysis of the <span class="hlt">shock</span> and double <span class="hlt">layer</span> solutions of this new equation (we would like to call it “M-Z equation”). It is found that the properties of these <span class="hlt">shock</span> and double <span class="hlt">layer</span> structures obtained from this analysis are significantly different from those obtained from the analysis of standard Gardner or Burgers’ equation. The implications of our results to dense plasmas in astrophysical objects (e.g., non-rotating white dwarf stars) are briefly discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19750023958','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19750023958"><span id="translatedtitle">Control of <span class="hlt">shock</span> wave-boundary <span class="hlt">layer</span> interactions by bleed in supersonic mixed compression inlets</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Fukuda, M. K.; Hingst, W. G.; Reshotko, E.</p> <p>1975-01-01</p> <p>An experimental investigation was conducted to determine the effect of bleed on a <span class="hlt">shock</span> wave-boundary <span class="hlt">layer</span> interaction in an axisymmetric mixed-compression supersonic inlet. The inlet was designed for a free-stream Mach number of 2.50 with 60-percent supersonic internal area contraction. The experiment was conducted in the NASA Lewis Research Center 10-Foot Supersonic Wind Tunnel. The effects of bleed amount and bleed geometry on the boundary <span class="hlt">layer</span> after a <span class="hlt">shock</span> wave-boundary <span class="hlt">layer</span> interaction were studied. The effect of bleed on the transformed form factor is such that the full realizable reduction is obtained by bleeding of a mass flow equal to about one-half of the incident boundary <span class="hlt">layer</span> mass flow. More bleeding does not yield further reduction. Bleeding upstream or downstream of the <span class="hlt">shock</span>-induced pressure rise is preferable to bleeding across the <span class="hlt">shock</span>-induced pressure rise.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014JPhCS.530a2068P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014JPhCS.530a2068P"><span id="translatedtitle">Investigations of <span class="hlt">shock</span> wave boundary <span class="hlt">layer</span> interaction on suction side of compressor profile</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Piotrowicz, M.; Flaszyński, P.; Doerffer, P.</p> <p>2014-08-01</p> <p>The <span class="hlt">shock</span> wave boundary <span class="hlt">layer</span> interaction on the suction side of transonic compressor blade is one of main objectives of TFAST project (Transition Location Effect on <span class="hlt">Shock</span> Wave Boundary <span class="hlt">Layer</span> Interaction). In order to look more closely into the flow structure on the suction side of a blade, a design of a generic test section in linear transonic wind tunnel was proposed. The test section which could reproduce flow structure, <span class="hlt">shock</span> wave location, pressure distribution and boundary <span class="hlt">layer</span> development similar to the obtained on a cascade profile is the main objective of the presented here design. The design of the proposed test section is very challenging, because of <span class="hlt">shock</span> wave existence, its interaction with boundary <span class="hlt">layer</span> and its influence on the 3-D flow structure in the test section.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012ExFl...52..591H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012ExFl...52..591H"><span id="translatedtitle">Time-resolved stereo PIV measurements of <span class="hlt">shock</span>-boundary <span class="hlt">layer</span> interaction on a supercritical airfoil</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hartmann, Axel; Klaas, Michael; Schröder, Wolfgang</p> <p>2012-03-01</p> <p>Time-resolved stereo particle-image velocimetry (TR-SPIV) and unsteady pressure measurements are used to analyze the unsteady flow over a supercritical DRA-2303 airfoil in transonic flow. The dynamic <span class="hlt">shock</span> wave-boundary <span class="hlt">layer</span> interaction is one of the most essential features of this unsteady flow causing a distinct oscillation of the flow field. Results from wind-tunnel experiments with a variation of the freestream Mach number at Reynolds numbers ranging from 2.55 to 2.79 × 106 are analyzed regarding the origin and nature of the unsteady <span class="hlt">shock</span>-boundary <span class="hlt">layer</span> interaction. Therefore, the TR-SPIV results are analyzed for three buffet flows. One flow exhibits a sinusoidal streamwise oscillation of the <span class="hlt">shock</span> wave only due to an acoustic feedback loop formed by the <span class="hlt">shock</span> wave and the trailing-edge noise. The other two buffet flows have been intentionally influenced by an artificial acoustic source installed downstream of the test section to investigate the behavior of the interaction to upstream-propagating disturbances generated by a defined source of noise. The results show that such upstream-propagating disturbances could be identified to be responsible for the upstream displacement of the <span class="hlt">shock</span> wave and that the feedback loop is formed by a pulsating separation of the boundary <span class="hlt">layer</span> dependent on the <span class="hlt">shock</span> position and the sound pressure level at the <span class="hlt">shock</span> position. Thereby, the pulsation of the separation could be determined to be a reaction to the <span class="hlt">shock</span> motion and not vice versa.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008APS..DPPUP6013G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008APS..DPPUP6013G"><span id="translatedtitle">Particle acceleration by quasi-<span class="hlt">parallel</span> <span class="hlt">shocks</span> in the solar wind</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Galinsky, V. L.; Shevchenko, V. I.</p> <p>2008-11-01</p> <p>The theoretical study of proton acceleration at a quasi-<span class="hlt">parallel</span> <span class="hlt">shock</span> due to interaction with Alfven waves self-consistently excited in both upstream and downstream regions was conducted using a scale-separation model [1]. The model uses conservation laws and resonance conditions to find where waves will be generated or dumped and hence particles will be pitch--angle scattered as well as the change of the wave energy due to instability or damping. It includes in consideration the total distribution function (the bulk plasma and high energy tail), so no any assumptions (e.g. seed populations, or some ad-hoc escape rate of accelerated particles) are required. The dynamics of ion acceleration by the November 11-12, 1978 interplanetary traveling <span class="hlt">shock</span> was investigated and compared with the observations [2] as well as with solution obtained using the so-called convection-diffusion equation for distribution function of accelerated particles [3]. [1] Galinsky, V.L., and V.I. Shevchenko, Astrophys. J., 669, L109, 2007. [2] Kennel, C.F., F.W. Coroniti, F.L. Scarf, W.A. Livesey, C.T. Russell, E.J. Smith, K.P. Wenzel, and M. Scholer, J. Geophys. Res. 91, 11,917, 1986. [3] Gordon B.E., M.A. Lee, E. Mobius, and K.J. Trattner, J. Geophys. Res., 104, 28,263, 1990.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19920043702&hterms=expression+body&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dexpression%2Bbody','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19920043702&hterms=expression+body&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dexpression%2Bbody"><span id="translatedtitle">An approximate viscous <span class="hlt">shock</span> <span class="hlt">layer</span> technique for calculating nonequilibrium hypersonic flows about blunt-nosed bodies</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Cheatwood, F. M.; Dejarnette, F. R.</p> <p>1992-01-01</p> <p>An approximate axisymmetric method has been developed which can reliably calculate nonequilibrium fully viscous hypersonic flows over blunt-nosed bodies. By substituting Maslen's second-order pressure expression for the normal momentum equation, a simplified form of the viscous <span class="hlt">shock</span> <span class="hlt">layer</span> (VSL) equations is obtained. This approach can solve both the subsonic and supersonic regions of the <span class="hlt">shock</span> <span class="hlt">layer</span> without a starting solution for the <span class="hlt">shock</span> shape. This procedure is significantly faster than the parabolized Navier-Stokes and VSL solvers and would be useful in a preliminary design environment. Solutions have been generated for air flows over several analytic body shapes. Surface heat transfer and pressure predictions are comparable to VSL results. Computed heating rates are in good agreement with experimental data. The present technique generates its own <span class="hlt">shock</span> shape as part of its solution, and therefore could be used to provide more accurate initial <span class="hlt">shock</span> shapes for higher-order procedures which require starting solutions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19830056002&hterms=OM&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3DOM','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19830056002&hterms=OM&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3DOM"><span id="translatedtitle">An experimental investigation of multiple <span class="hlt">shock</span> wave/turbulent boundary <span class="hlt">layer</span> interactions in a circular duct</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Om, D.; Childs, M. E.</p> <p>1983-01-01</p> <p>Detailed pitot, static and wall pressure measurements have been obtained for multiple <span class="hlt">shock</span> wave/turbulent boundary <span class="hlt">layer</span> interactions in a circular duct at a free-stream Mach number of 1.49 and at a unit Reynolds number of 4.90 x 10 to the 6th per meter. The details of the flow field show the formation of a series of normal <span class="hlt">shock</span> waves with successively decreasing strength and with decreasing distance between the successive <span class="hlt">shock</span> waves. The overall pressure recovery is much lower than the single normal <span class="hlt">shock</span> pressure recovery at the same free-stream Mach number. A one-dimensional flow model based on the boundary <span class="hlt">layer</span> displacement buildup is postulated to explain the formation of a series of normal <span class="hlt">shock</span> waves.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19920066107&hterms=split+wave&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dsplit%2Bwave','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19920066107&hterms=split+wave&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dsplit%2Bwave"><span id="translatedtitle">Three-dimensional <span class="hlt">shock-wave/boundary-layer</span> interactions with bleed through a circular hole</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Rimlinger, M. J.; Shih, T. I.-P.; Chyu, W. J.</p> <p>1992-01-01</p> <p>Computations were performed to study three-dimensional (3-D), <span class="hlt">shock-wave/boundary-layer</span> interactions on a flat plate in which fluid in the boundary <span class="hlt">layer</span> was bled through a circular hole into a plenum to control <span class="hlt">shock</span>-wave induced separation. Results are presented which show the details of the 3-D flowfield about the bleed hole and how bleed-hole placement relative to <span class="hlt">shock</span>-wave impingement affect upstream, spanwise, and downstream influence lengths. This study revealed an underlying mechanisms by which bleed holes can affect <span class="hlt">shock-wave/boundary-layer</span> interactions. This investigation is based on the ensemble-averaged, "full-compressible" Navier-Stokes equations closed by the Baldwin-Lomax turbulence model. Solutions to these equations were obtained by an implicit finite-volume method based on the partially-split, two-factored algorithm of Steger.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016ShWav..26..129C&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016ShWav..26..129C&link_type=ABSTRACT"><span id="translatedtitle">A new facility for studying <span class="hlt">shock</span>-wave passage over dust <span class="hlt">layers</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chowdhury, A. Y.; Marks, B. D.; Johnston, H. Greg; Mannan, M. Sam; Petersen, E. L.</p> <p>2016-03-01</p> <p>Dust explosion hazards in areas where coal and other flammable materials are found have caused unnecessary loss of life and halted business operations in some instances. The elimination of secondary dust explosion hazards, i.e., reducing dust dispersion, can be characterized in <span class="hlt">shock</span> tubes to understand <span class="hlt">shock</span>-dust interactions. For this reason, a new <span class="hlt">shock</span>-tube test section was developed and integrated into an existing <span class="hlt">shock</span>-tube facility. The test section has large windows to allow for the use of the shadowgraph technique to track dust-<span class="hlt">layer</span> growth behind a passing normal <span class="hlt">shock</span> wave, and it is designed to handle an initial pressure of 1 atm with an incident <span class="hlt">shock</span> wave Mach number as high as 2 to mimic real-world conditions. The test section features an easily removable dust pan with inserts to allow for adjustment of the dust-<span class="hlt">layer</span> thickness. The design also allows for changing the experimental variables such as initial pressure, <span class="hlt">shock</span> Mach number (Ms), dust-<span class="hlt">layer</span> thickness, and the characteristics of the dust itself. The characterization experiments presented herein demonstrate the advantages of the authors' test techniques toward providing new physical insights over a wider range of data than what have been available heretofore in the literature. Limestone dust with a <span class="hlt">layer</span> thickness of 3.2 mm was subjected to Ms = 1.23, 1.32, and 1.6 <span class="hlt">shock</span> waves, and dust-<span class="hlt">layer</span> rise height was mapped with respect to time after <span class="hlt">shock</span> passage. Dust particles subjected to a Ms = 1.6 <span class="hlt">shock</span> wave rose more rapidly and to a greater height with respect to <span class="hlt">shock</span> wave propagation than particles subjected to Ms = 1.23 and 1.32 <span class="hlt">shock</span> waves. Although these results are in general agreement with the literature, the new data also highlight physical trends for dust-<span class="hlt">layer</span> growth that have not been recorded previously, to the best of the authors' knowledge. For example, the dust-<span class="hlt">layer</span> height rises linearly until a certain time where the growth rate is dramatically reduced, and in this second</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015ApJ...808....2W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015ApJ...808....2W"><span id="translatedtitle">The Role of Large Amplitude Upstream Low-frequency Waves in the Generation of Superthermal Ions at a Quasi-<span class="hlt">parallel</span> Collisionless <span class="hlt">Shock</span>: Cluster Observations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wu, Mingyu; Hao, Yufei; Lu, Quanming; Huang, Can; Guo, Fan; Wang, Shui</p> <p>2015-07-01</p> <p>The superthermal ions at a quasi-<span class="hlt">parallel</span> collisionless <span class="hlt">shock</span> are considered to be generated during the reformation of the <span class="hlt">shock</span>. Recently, hybrid simulations of a quasi-<span class="hlt">parallel</span> <span class="hlt">shock</span> have shown that during the reformation of a quasi-<span class="hlt">parallel</span> <span class="hlt">shock</span> the large-amplitude upstream low-frequency waves can trap the reflected ions at the <span class="hlt">shock</span> 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-<span class="hlt">parallel</span> <span class="hlt">shock</span> 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 <span class="hlt">shock</span> front and the peak of the upstream wave just in front of the <span class="hlt">shock</span> front). These superthermal ions are considered to originate from the reflected ions at the <span class="hlt">shock</span> front, and the modulation is caused due to the trapping of the reflected ions between the upstream waves or the upstream waves and the <span class="hlt">shock</span> 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-<span class="hlt">parallel</span> <span class="hlt">shock</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.emergencycareforyou.org/Emergency-101/Emergencies-A-Z/Shock/','NIH-MEDLINEPLUS'); return false;" href="http://www.emergencycareforyou.org/Emergency-101/Emergencies-A-Z/Shock/"><span id="translatedtitle"><span class="hlt">Shock</span></span></a></p> <p><a target="_blank" href="http://medlineplus.gov/">MedlinePlus</a></p> <p></p> <p></p> <p>... Emergencies A-Z Share this! Home » Emergency 101 <span class="hlt">Shock</span> <span class="hlt">Shock</span> is a serious, often life-threatening medical condition ... of death for critically ill or injured people. <span class="hlt">Shock</span> results when the body is not getting enough ...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://medlineplus.gov/ency/article/000039.htm','NIH-MEDLINEPLUS'); return false;" href="https://medlineplus.gov/ency/article/000039.htm"><span id="translatedtitle"><span class="hlt">Shock</span></span></a></p> <p><a target="_blank" href="http://medlineplus.gov/">MedlinePlus</a></p> <p></p> <p></p> <p>... problems) Hypovolemic <span class="hlt">shock</span> (caused by too little blood volume) Anaphylactic <span class="hlt">shock</span> (caused by allergic reaction) Septic <span class="hlt">shock</span> ( ... as heart attack or heart failure ) Low blood volume (as with heavy bleeding or dehydration ) Changes in ...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19910030160&hterms=QUEST&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3DQUEST','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19910030160&hterms=QUEST&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3DQUEST"><span id="translatedtitle">Re-forming supercritical quasi-<span class="hlt">parallel</span> <span class="hlt">shocks</span>. II - Mechanism for wave generation and front re-formation</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Winske, D.; Thomas, V. A.; Omidi, N.; Quest, K. B.</p> <p>1990-01-01</p> <p>This paper continues the study of Thomas et al. (1990) in which hybrid simulations of quasi-<span class="hlt">parallel</span> <span class="hlt">shocks</span> were performed in one and two spatial dimensions. To identify the wave generation processes, the electromagnetic structure of the <span class="hlt">shock</span> is examined by performing a number of one-dimensional hybrid simulations of quasi-<span class="hlt">parallel</span> <span class="hlt">shocks</span> for various upstream conditions. In addition, numerical experiments were carried out in which the backstreaming ions were removed from calculations to show their fundamental importance in reformation process. The calculations show that the waves are excited before ions can propagate far enough upstream to generate resonant modes. At some later times, the waves are regenerated at the leading edge of the interface, with properties like those of their initial interactions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/23005206','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/23005206"><span id="translatedtitle"><span class="hlt">Shock</span> velocity increase due to a heterogeneity produced by a two-gas <span class="hlt">layer</span>.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Elbaz, Déborah; Jourdan, Georges; Houas, Lazhar; Jaouen, Stéphane; Ballereau, Philippe; Dias, Frédéric; Canaud, Benoit</p> <p>2012-06-01</p> <p><span class="hlt">Shock</span> tube experiments are performed in order to study <span class="hlt">shock</span> propagation along a two-gas <span class="hlt">layer</span> in a confined geometry and to compare it to the case of a homogeneous density equivalent mixture. The analysis of the homogeneous case gives values for the adiabatic coefficient and density of the mixture of both gases, while the comparison between heterogeneous and homogeneous media with the same averaged density shows modifications of the <span class="hlt">shock</span> front shape and velocity. In the two-gas <span class="hlt">layer</span>, the <span class="hlt">shock</span> propagates faster than in the homogeneous medium. The <span class="hlt">shock</span> front is curved with a triple point which appears close to the <span class="hlt">shock</span>-tube wall, in the slow medium, while it stays planar during its whole propagation in the homogeneous mixture. A correlation is found between the angle of curvature and the <span class="hlt">shock</span> velocity increase. It is confirmed by two-dimensional Eulerian numerical calculations. Experiments and calculations exhibit very good agreement on all the measurements when molecular diffusion is taken into account in the numerical calculations. A sustained irregular refraction pattern of the <span class="hlt">shock</span> front at the diffuse interface of both gases is obtained experimentally and confirmed by the calculations. PMID:23005206</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20070004895','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20070004895"><span id="translatedtitle">Optimal Control of <span class="hlt">Shock</span> Wave Turbulent Boundary <span class="hlt">Layer</span> Interactions Using Micro-Array Actuation</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Anderson, Bernhard H.; Tinapple, Jon; Surber, Lewis</p> <p>2006-01-01</p> <p>The intent of this study on micro-array flow control is to demonstrate the viability and economy of Response Surface Methodology (RSM) to determine optimal designs of micro-array actuation for controlling the <span class="hlt">shock</span> wave turbulent boundary <span class="hlt">layer</span> interactions within supersonic inlets and compare these concepts to conventional bleed performance. The term micro-array refers to micro-actuator arrays which have heights of 25 to 40 percent of the undisturbed supersonic boundary <span class="hlt">layer</span> thickness. This study covers optimal control of <span class="hlt">shock</span> wave turbulent boundary <span class="hlt">layer</span> interactions using standard micro-vane, tapered micro-vane, and standard micro-ramp arrays at a free stream Mach number of 2.0. The effectiveness of the three micro-array devices was tested using a <span class="hlt">shock</span> pressure rise induced by the 10 <span class="hlt">shock</span> generator, which was sufficiently strong as to separate the turbulent supersonic boundary <span class="hlt">layer</span>. The overall design purpose of the micro-arrays was to alter the properties of the supersonic boundary <span class="hlt">layer</span> by introducing a cascade of counter-rotating micro-vortices in the near wall region. In this manner, the impact of the <span class="hlt">shock</span> wave boundary <span class="hlt">layer</span> (SWBL) interaction on the main flow field was minimized without boundary bleed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013APS..DFDG25003G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013APS..DFDG25003G"><span id="translatedtitle">Effect of Pulsed Plasma Jets on Reflected <span class="hlt">Shock</span>-Turbulent Boundary <span class="hlt">Layer</span> Interaction</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Greene, Benton R.; Clemens, Noel T.; Magari, Patrick; Micka, Daniel</p> <p>2013-11-01</p> <p><span class="hlt">Shock</span>-induced turbulent boundary <span class="hlt">layer</span> separation can have many detrimental effects in supersonic inlets including flow instability, fatigue of structural panels, poor pressure recovery, and unstart. Pulsed plasma jets (or ``spark jets''), zero net mass flow jets characterized by high bandwidth and the ability to direct momentum into the flow, are one promising method of reducing <span class="hlt">shock</span>-induced separation and boundary <span class="hlt">layer</span> distortion. The current study is focused on investigating the efficacy of pulsed plasma jets to reduce the boundary <span class="hlt">layer</span> distortion induced by a reflected <span class="hlt">shock</span> interaction in a Mach 3 flow. A 7° <span class="hlt">shock</span> generator placed outside the tunnel ceiling boundary <span class="hlt">layer</span> produces an incident <span class="hlt">shock</span> on the floor of the tunnel of sufficient strength to induce separation. An array of pulsed plasma jets are placed approximately 2 boundary <span class="hlt">layer</span> thicknesses upstream of the interaction and pulsed at between 1 kHz and 4 kHz. PIV is used to investigate the effect of the jets on the nature of the separation as well as the boundary <span class="hlt">layer</span> distortion and pressure recovery downstream of the interaction. Funded through AFRL in collaboration with Creare, Inc.</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_3");'>3</a></li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li class="active"><span>5</span></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_13");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_5 --> <div id="page_6" 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_4");'>4</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li class="active"><span>6</span></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_13");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="101"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19960009427','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19960009427"><span id="translatedtitle">Control and reduction of unsteady pressure loads in separated <span class="hlt">shock</span> wave turbulent boundary <span class="hlt">layer</span> interaction</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Dolling, David S.; Barter, John W.</p> <p>1995-01-01</p> <p>The focus was on developing means of controlling and reducing unsteady pressure loads in separated <span class="hlt">shock</span> wave turbulent boundary <span class="hlt">layer</span> interactions. Section 1 describes how vortex generators can be used to effectively reduce loads in compression ramp interaction, while Section 2 focuses on the effects of 'boundary-<span class="hlt">layer</span> separators' on the same interaction.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19740030715&hterms=structure+atom&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3Dstructure%2Batom','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19740030715&hterms=structure+atom&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3Dstructure%2Batom"><span id="translatedtitle">Interrelated structures of the transport <span class="hlt">shock</span> and collisional relaxation <span class="hlt">layer</span> in a multitemperature, multilevel ionized gas</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Vinolo, A. R.; Clarke, J. H.</p> <p>1973-01-01</p> <p>The gas dynamic structures of the transport <span class="hlt">shock</span> and the downstream collisional relaxation <span class="hlt">layer</span> are evaluated for partially ionized monatomic gases. Elastic and inelastic collisional nonequilibrium effects are taken into consideration. In the microscopic model of the atom, three electronic levels are accounted for. By using an asymptotic technique, the <span class="hlt">shock</span> morphology is found on a continuum flow basis. This procedure gives two distinct <span class="hlt">layers</span> in which the nonequilibrium effects to be considered are different. A transport <span class="hlt">shock</span> appears as the inner solution to an outer collisional relaxation <span class="hlt">layer</span>. The results show four main interesting points: (1) on structuring the transport <span class="hlt">shock</span>, ionization and excitation rates must be included in the formulation, since the flow is not frozen with respect to the population of the different electronic levels; (2) an electron temperature precursor appears at the beginning of the transport <span class="hlt">shock</span>; (3) the collisional <span class="hlt">layer</span> is rationally reduced to quadrature for special initial conditions, which (4) are obtained from new Rankine-Hugoniot relations for the inner <span class="hlt">shock</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015PhFl...27l6103A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015PhFl...27l6103A"><span id="translatedtitle">Mechanism of <span class="hlt">shock</span> unsteadiness in separated <span class="hlt">shock/boundary-layer</span> interactions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Agostini, L.; Larchevêque, L.; Dupont, P.</p> <p>2015-12-01</p> <p>A large-eddy simulation-based study is presented and focuses on different unsteadiness-source features in a Mach 2.3 <span class="hlt">shock</span> reflection with separation. The sources of unsteadiness are localized and the path taken by disturbance as it spreads out to the whole field is defined. It is shown that the phenomena arising inside the recirculation bubble govern the whole interaction, at both low and intermediate frequencies. Indeed, the <span class="hlt">shock</span> motion appears to mirror phenomena found in the separated zone. Moreover, features of separated-flow unsteadiness bear some resemblance to those occurring in incompressible flows. An equivalent inviscid scheme of the unsteady interaction is established in order to describe the whole <span class="hlt">shock</span>-system unsteadiness at low and intermediate frequencies and the downstream unsteady-pressure field.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19920022918','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19920022918"><span id="translatedtitle">Experimental studies of hypersonic <span class="hlt">shock</span>-wave boundary-<span class="hlt">layer</span> interactions</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Lu, Frank K.</p> <p>1992-01-01</p> <p>Two classes of <span class="hlt">shock</span>-wave boundary-<span class="hlt">layer</span> interactions were studied experimentally in a <span class="hlt">shock</span> tunnel in which a low Reynolds number, turbulent flow at Mach 8 was developed on a cold, flat test surface. The two classes of interactions were: (1) a swept interaction generated by a wedge ('fin') mounted perpendicularly on the flat plate; and (2) a two-dimensional, unseparated interaction induced by a <span class="hlt">shock</span> impinging near an expansion corner. The swept interaction, with wedge angles of 5-20 degrees, was separated and there was also indication that the strongest interactions prossessed secondary separation zones. The interaction spread out extensively from the inviscid <span class="hlt">shock</span> location although no indication of quasi-conical symmetry was evident. The surface pressure from the upstream influence to the inviscid <span class="hlt">shock</span> was relatively low compared to the inviscid downstream value but it rose rapidly past the inviscid <span class="hlt">shock</span> location. However, the surface pressure did not reach the downstream inviscid value and reasons were proposed for this anomalous behavior compared to strongly separated, supersonic interactions. The second class of interactions involved weak <span class="hlt">shocks</span> impinging near small expansion corners. As a prelude to studying this interaction, a hypersonic similarity parameter was identified for the pure, expansion corner flow. The expansion corner severely damped out surface pressure fluctuations. When a <span class="hlt">shock</span> impinged upstream of the corner, no significant changes to the surface pressure were found as compared to the case when the <span class="hlt">shock</span> impinged on a flat plate. But, when the <span class="hlt">shock</span> impinged downstream of the corner, a close coupling existed between the two wave systems, unlike the supersonic case. This close coupling modified the upstream influence. Regardless of whether the <span class="hlt">shock</span> impinged ahead or behind the corner, the downstream region was affected by the close coupling between the <span class="hlt">shock</span> and the expansion. Not only was the mean pressure distribution modified but the</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> wave-boundary <span class="hlt">layer</span> 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 <span class="hlt">layer</span> transition on an oblique <span class="hlt">shock</span> wave reflection. 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 <span class="hlt">layer</span> is only 0.2 mm, and seeding proved to be problematic as practically no seeding was recorded in the lower 40 % of the boundary <span class="hlt">layer</span>. 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 <span class="hlt">layer</span> transitions to a turbulent state. This allowed the seeding distribution to be used as an indicator for the state of the boundary <span class="hlt">layer</span>, permitting to obtain an approximate intermittency distribution for the boundary <span class="hlt">layer</span> transition region. This knowledge was then used for positioning the oblique <span class="hlt">shock</span> wave in the laminar, transitional (50 % intermittency) or turbulent region of the boundary <span class="hlt">layer</span>. 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 <span class="hlt">layer</span> is lifted over the separation bubble and remains in a laminar state up to the impingement point of the <span class="hlt">shock</span> wave. 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://hdl.handle.net/2060/20130008991','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20130008991"><span id="translatedtitle">Validation of <span class="hlt">Shock</span> <span class="hlt">Layer</span> Radiation: Perspectives for Test Cases</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Brandis, Aaron</p> <p>2012-01-01</p> <p>This paper presents a review of the analysis and measurement of radiation data obtained in the NASA Ames Research Center's Electric Arc <span class="hlt">Shock</span> Tube (EAST) facility. The goal of these experiments was to measure the level of radiation encountered during atmospheric entry. The data obtained from these experiments is highlighted by providing the first spectrally and spatially resolved data for high speed Earth entry and measurements of the CO 4th positive band for conditions relevant to Mars entry. Comparisons of the EAST data with experimental results obtained from <span class="hlt">shock</span> tunnels at JAXA and the University of Queensland are presented. Furthermore, the paper will detail initial analyses in to the influence and characterization of the measure non-equilibrium radiation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20080026342','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20080026342"><span id="translatedtitle">Validation of High-Speed Turbulent Boundary <span class="hlt">Layer</span> and <span class="hlt">Shock</span>-Boundary <span class="hlt">Layer</span> Interaction Computations with the OVERFLOW Code</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Oliver, A. B.; Lillard, R. P.; Blaisdell, G. A.; Lyrintizis, A. S.</p> <p>2006-01-01</p> <p>The capability of the OVERFLOW code to accurately compute high-speed turbulent boundary <span class="hlt">layers</span> and turbulent <span class="hlt">shock</span>-boundary <span class="hlt">layer</span> interactions is being evaluated. Configurations being investigated include a Mach 2.87 flat plate to compare experimental velocity profiles and boundary <span class="hlt">layer</span> growth, a Mach 6 flat plate to compare experimental surface heat transfer,a direct numerical simulation (DNS) at Mach 2.25 for turbulent quantities, and several Mach 3 compression ramps to compare computations of <span class="hlt">shock</span>-boundary <span class="hlt">layer</span> interactions to experimental laser doppler velocimetry (LDV) data and hot-wire data. The present paper describes outlines the study and presents preliminary results for two of the flat plate cases and two small-angle compression corner test cases.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015shw2.conf.1199E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015shw2.conf.1199E"><span id="translatedtitle">Experimental Investigation of Axisymmetric Transitional <span class="hlt">Shock</span> Wave Boundary <span class="hlt">Layer</span> Interactions at Mach 5</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Erdem, E.; Kontis, K.; Johnstone, E.; Murray, N.; Steelant, J.</p> <p></p> <p><span class="hlt">Shock</span> Wave Boundary <span class="hlt">Layer</span> Interactions (SWBLIs) can induce separation which causes loss of a control surface effectiveness, drop of an air intake efficiency and it may be the origin of large scale fluctuations such as air-intake buzz, buffeting or fluctuating side loads in separated propulsive nozzles. The subsequent reattachment of the separated shear <span class="hlt">layer</span> on a nearby surface gives rise to local heat transfer rates which can be far in excess of those of an attached boundary <span class="hlt">layer</span> [1].</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19850018354','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19850018354"><span id="translatedtitle">Investigation to optimize the passive <span class="hlt">shock</span> wave/boundary <span class="hlt">layer</span> control for supercritical airfoil drag reduction</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Nagamatsu, H. T.; Dyer, R.</p> <p>1984-01-01</p> <p>The passive <span class="hlt">shock</span> wave/boundary <span class="hlt">layer</span> control for reducing the drag of 14%-thick supercritical airfoil was investigated in the 3 in. x 15.4 in. RPI Transonic Wind Tunnel with and without the top wall insert at transonic Mach numbers. Top wall insert was installed to increase the flow Mach number to 0.90 with the model mounted on the test section bottom wall. Various porous surfaces with a cavity underneath were positioned on the area of the airfoil where the <span class="hlt">shock</span> wave occurs. The higher pressure behind the <span class="hlt">shock</span> wave circulates flow through the cavity to the lower pressure ahead of the <span class="hlt">shock</span> wave. The effects from this circulation prevent boundary <span class="hlt">layer</span> separation and enthropy increase hrough the <span class="hlt">shock</span> wave. The static pressure distributions over the airfoil, the wake impact pressure survey for determining the profile drag and the Schlieren photographs for porous surfaces are presented and compared with the results for solid surface airfoil. With a 2.8% uniform porosity the normal <span class="hlt">shock</span> wave for the solid surface was changed to a lambda <span class="hlt">shock</span> wave, and the wake impact pressure data indicate a drag coefficient reduction as much as 45% lower than for the solid surface airfoil at high transonic Mach numbers.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015PhFl...27i1704T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015PhFl...27i1704T"><span id="translatedtitle">Frequency modulation in <span class="hlt">shock</span> wave-boundary <span class="hlt">layer</span> interaction by repetitive-pulse laser energy deposition</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tamba, T.; Pham, H. S.; Shoda, T.; Iwakawa, A.; Sasoh, A.</p> <p>2015-09-01</p> <p>Modulation of <span class="hlt">shock</span> foot oscillation due to energy deposition by repetitive laser pulses in <span class="hlt">shock</span> wave-boundary <span class="hlt">layer</span> interaction over an axisymmetric nose-cylinder-flare model in Mach 1.92 flow was experimentally studied. From a series of 256 schlieren images, density oscillation spectra at each pixel were obtained. When laser pulses of approximately 7 mJ were deposited with a repetition frequency, fe, of 30 kHz or lower, the flare <span class="hlt">shock</span> oscillation had a peak spectrum equivalent to the value of fe. However, with fe of 40 kHz-60 kHz, it experienced frequency modulation down to lower than 20 kHz.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19880063939&hterms=wave+length&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dwave%2Blength','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19880063939&hterms=wave+length&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dwave%2Blength"><span id="translatedtitle">On the inception lengths of swept <span class="hlt">shock</span>-wave/turbulent boundary-<span class="hlt">layer</span> interactions</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Settles, G. S.</p> <p>1986-01-01</p> <p>Experimental data are shown for the inception lengths of swept compression corner-generated and fin-generated <span class="hlt">shock</span>/boundary <span class="hlt">layer</span> interactions at Mach 2.95. These results are found to correlate on the basis of three different flow regimes. The inception lengths of these flows are dominated by a singularity at the cylindrical/conical boundary for swept corners and by an elongation due to <span class="hlt">shock</span> wave sweepback for fin interactions. Similarity rules for both Re(delta)and <span class="hlt">shock</span> generator geometry effects on inception lengths are demonstrated.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19720025616','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19720025616"><span id="translatedtitle">Interrelated structures of the transport <span class="hlt">shock</span> and collisional relaxation <span class="hlt">layer</span> in a multitemperature, multilevel ionized gas</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Vinolo, A. R.; Clarke, J. H.</p> <p>1972-01-01</p> <p>The gas dynamic structures of the transport <span class="hlt">shock</span> and the downstream collisional relaxation <span class="hlt">layer</span> are evaluated for partially ionized monatomic gases. Elastic and inelastic collisional nonequilibrium effects are taken into consideration. Three electronic levels are accounted for in the microscopic model of the atom. Nonequilibrium processes with respect to population of levels and species plus temperature are considered. By using an asymptotic technique the <span class="hlt">shock</span> morphology is found on a continuum flow basis. The asymptotic procedure gives two distinct <span class="hlt">layers</span> in which the nonequilibrium effects to be considered are different. A transport <span class="hlt">shock</span> appears as the inner solution to an outer collisional relaxation <span class="hlt">layer</span> in which the gas reaches local equilibrium. A family of numerical examples is displayed for different flow regimes. Argon and helium models are used in these examples.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20120004157','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20120004157"><span id="translatedtitle">Experimental Investigation of Normal <span class="hlt">Shock</span> Boundary-<span class="hlt">Layer</span> Interaction with Hybrid Flow Control</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Vyas, Manan A.; Hirt, Stefanie M.; Anderson, Bernhard H.</p> <p>2012-01-01</p> <p>Hybrid flow control, a combination of micro-ramps and micro-jets, was experimentally investigated in the 15x15 cm Supersonic Wind Tunnel (SWT) at the NASA Glenn Research Center. Full factorial, a design of experiments (DOE) method, was used to develop a test matrix with variables such as inter-ramp spacing, ramp height and chord length, and micro-jet injection flow ratio. A total of 17 configurations were tested with various parameters to meet the DOE criteria. In addition to boundary-<span class="hlt">layer</span> measurements, oil flow visualization was used to qualitatively understand <span class="hlt">shock</span> induced flow separation characteristics. The flow visualization showed the normal <span class="hlt">shock</span> location, size of the separation, path of the downstream moving counter-rotating vortices, and corner flow effects. The results show that hybrid flow control demonstrates promise in reducing the size of <span class="hlt">shock</span> boundary-<span class="hlt">layer</span> interactions and resulting flow separation by means of energizing the boundary <span class="hlt">layer</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19980151085','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19980151085"><span id="translatedtitle">An Approximate Axisymmetric Viscous <span class="hlt">Shock</span> <span class="hlt">Layer</span> Aeroheating Method for Three-Dimensional Bodies</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Brykina, Irina G.; Scott, Carl D.</p> <p>1998-01-01</p> <p>A technique is implemented for computing hypersonic aeroheating, shear stress, and other flow properties on the windward side of a three-dimensional (3D) blunt body. The technique uses a 2D/axisymmetric flow solver modified by scale factors for a, corresponding equivalent axisymmetric body. Examples are given in which a 2D solver is used to calculate the flow at selected meridional planes on elliptic paraboloids in reentry flight. The report describes the equations and the codes used to convert the body surface parameters into input used to scale the 2D viscous <span class="hlt">shock</span> <span class="hlt">layer</span> equations in the axisymmetric viscous <span class="hlt">shock</span> <span class="hlt">layer</span> code. Very good agreement is obtained with solutions to finite rate chemistry 3D thin viscous <span class="hlt">shock</span> <span class="hlt">layer</span> equations for a finite rate catalytic body.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19910058794&hterms=expression+body&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dexpression%2Bbody','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19910058794&hterms=expression+body&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dexpression%2Bbody"><span id="translatedtitle">An approximate viscous <span class="hlt">shock</span> <span class="hlt">layer</span> approach to calculating hypersonic flows about blunt-nosed bodies</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Cheatwood, F. MCN.; Dejarnette, F. R.</p> <p>1991-01-01</p> <p>An approximate axisymmetric method has been developed which can reliably calculate fully viscous hypersonic flows over blunt-nosed bodies. By substituting Maslen's second order pressure expression for the normal momentum equation, a simplified form of the viscous <span class="hlt">shock</span> <span class="hlt">layer</span> (VSL) equations is obtained. This approach can solve both the subsonic and supersonic regions of the <span class="hlt">shock</span> <span class="hlt">layer</span> without a starting solution for the <span class="hlt">shock</span> shape. Since the method is fully viscous, the problems associated with coupling a boundary-<span class="hlt">layer</span> solution with an inviscid-<span class="hlt">layer</span> solution are avoided. This procedure is significantly faster than the parabolized Navier-Stokes (PNS) or VSL solvers and would be useful in a preliminary design environment. Problems associated with a previously developed approximate VSL technique are addressed. Surface heat transfer and pressure predictions are comparable to both VSL results and experimental data. The present technique generates its own <span class="hlt">shock</span> shape as part of its solution, and therefore could be used to provide more accurate initial <span class="hlt">shock</span> shapes for higher-order procedures which require starting solutions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19930051623&hterms=split+wave&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dsplit%2Bwave','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19930051623&hterms=split+wave&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dsplit%2Bwave"><span id="translatedtitle">Numerical study of <span class="hlt">shock-wave/boundary-layer</span> interactions with bleed</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hahn, T. O.; Shih, T. I.-P.; Chyu, W. J.</p> <p>1993-01-01</p> <p>A numerical study was conducted to investigate how bleed through a two-dimensional slot affects <span class="hlt">shock</span>-wave induced, boundary-<span class="hlt">layer</span> separation on a flat plate. This study is based on the ensemble-averaged, compressible, Navier-Stokes equations closed by the Baldwin-Lomax, algebraic turbulence model. The algorithm used to obtain solutions was the implicit, partially split, two-factored scheme of Steger. This study examined the effects of the following parameters in controlling <span class="hlt">shock</span>-wave induced flow separation: location of slot in relation to where the incident <span class="hlt">shock</span> wave impinged on the boundary <span class="hlt">layer</span>, size of slot in relation to the boundary-<span class="hlt">layer</span> thickness, number of slots, spacings between slots, and strength of the incident <span class="hlt">shock</span> wave. This study also showed the nature of the very complex flowfield about the slot or slots and how the plenum affects the bleed process. The results of this study are relevant to problems where bleed is used to control <span class="hlt">shock</span>-wave induced, boundary-<span class="hlt">layer</span> separation (e.g., inside jet engine inlets and wind tunnels).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19960000871','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19960000871"><span id="translatedtitle">An investigation of bleed configurations and their effect on <span class="hlt">shock</span> wave/boundary <span class="hlt">layer</span> interactions</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hamed, Awatef</p> <p>1995-01-01</p> <p>The design of high efficiency supersonic inlets is a complex task involving the optimization of a number of performance parameters such as pressure recovery, spillage, drag, and exit distortion profile, over the flight Mach number range. Computational techniques must be capable of accurately simulating the physics of <span class="hlt">shock</span>/boundary <span class="hlt">layer</span> interactions, secondary corner flows, flow separation, and bleed if they are to be useful in the design. In particular, bleed and flow separation, play an important role in inlet unstart, and the associated pressure oscillations. Numerical simulations were conducted to investigate some of the basic physical phenomena associated with bleed in oblique <span class="hlt">shock</span> wave boundary <span class="hlt">layer</span> interactions that affect the inlet performance.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19910057679&hterms=skin+layers&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dskin%2Blayers','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19910057679&hterms=skin+layers&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dskin%2Blayers"><span id="translatedtitle">Laser interferometer/Preston tube skin-friction comparison in <span class="hlt">shock/boundary-layer</span> interaction</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Kim, K.-S.; Lee, Y.; Settles, G. S.</p> <p>1991-01-01</p> <p>An evaluation is conducted of the accuracy of the 'Preston tube' surface pitot-pressure skin friction measurement method relative to the already proven laser interferometer skin-friction meter in a swept <span class="hlt">shock</span> wave/turbulent boundary-<span class="hlt">layer</span> interaction. The Preston tube was used to estimate the total shear-stress distribution in a fin-generated swept <span class="hlt">shock</span>-wave/turbulent boundary-<span class="hlt">layer</span> interaction. The Keener-Hopkins calibration method using the isentropic relation to calculate the Preston-tube Mach number produces the best results.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19950016044','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19950016044"><span id="translatedtitle">Numerical study of boundary <span class="hlt">layer</span> interaction with <span class="hlt">shocks</span>: Method and code validation</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Adams, Nikolaus A.</p> <p>1994-01-01</p> <p>A major problem in modeling of turbulent supersonic flows is the correct assessment of viscous-inviscid interaction problems. Of particular interest is the interaction of boundary <span class="hlt">layers</span> with <span class="hlt">shocks</span>. Present turbulence models give in most cases unsatisfactory results in the region of rapid distortion and in the separation region (if one is present) in particular with regard to mean flow profiles and turbulence quantities. The objective of the present work is the direct numerical simulation of <span class="hlt">shock</span> boundary <span class="hlt">layer</span> interaction. This report summarizes the first phase during which a numerical method suitable for this problem has been developed and a computer code has been written and tested.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/101957','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/101957"><span id="translatedtitle">Heat release effects on the instability of <span class="hlt">parallel</span> shear <span class="hlt">layers</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Hegde, U.</p> <p>1994-01-01</p> <p>The influence of time-dependent heat addition on the linear instablity of shear <span class="hlt">layers</span> is of considerable interest in understanding the dynamic behavior of reacting flows and combustion-turbulence interactions. The approach is based upon the Bernoulli enthalpy aeroacoustics theory, which utilizes the specific enthalpy and specific entropy as the primary thermodynamic variables. In addition, velocity oscillations are split into Helmoholtz decomposition theorem.</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_4");'>4</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li class="active"><span>6</span></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_13");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_6 --> <div id="page_7" 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_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li class="active"><span>7</span></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_13");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="121"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014PhPl...21b2703R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014PhPl...21b2703R"><span id="translatedtitle"><span class="hlt">Shock</span> timing measurements and analysis in deuterium-tritium-ice <span class="hlt">layered</span> capsule implosions on NIF</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Robey, H. F.; Celliers, P. M.; Moody, J. D.; Sater, J.; Parham, T.; Kozioziemski, B.; Dylla-Spears, R.; Ross, J. S.; LePape, S.; Ralph, J. E.; Hohenberger, M.; Dewald, E. L.; Berzak Hopkins, L.; Kroll, J. J.; Yoxall, B. E.; Hamza, A. V.; Boehly, T. R.; Nikroo, A.; Landen, O. L.; Edwards, M. J.</p> <p>2014-02-01</p> <p>Recent advances in <span class="hlt">shock</span> timing experiments and analysis techniques now enable <span class="hlt">shock</span> measurements to be performed in cryogenic deuterium-tritium (DT) ice <span class="hlt">layered</span> capsule implosions on the National Ignition Facility (NIF). Previous measurements of <span class="hlt">shock</span> timing in inertial confinement fusion implosions [Boehly et al., Phys. Rev. Lett. 106, 195005 (2011); Robey et al., Phys. Rev. Lett. 108, 215004 (2012)] were performed in surrogate targets, where the solid DT ice shell and central DT gas were replaced with a continuous liquid deuterium (D2) fill. These previous experiments pose two surrogacy issues: a material surrogacy due to the difference of species (D2 vs. DT) and densities of the materials used and a geometric surrogacy due to presence of an additional interface (ice/gas) previously absent in the liquid-filled targets. This report presents experimental data and a new analysis method for validating the assumptions underlying this surrogate technique. Comparison of the data with simulation shows good agreement for the timing of the first three <span class="hlt">shocks</span>, but reveals a considerable discrepancy in the timing of the 4th <span class="hlt">shock</span> in DT ice <span class="hlt">layered</span> implosions. Electron preheat is examined as a potential cause of the observed discrepancy in the 4th <span class="hlt">shock</span> timing.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19890054707&hterms=wave+length&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dwave%2Blength','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19890054707&hterms=wave+length&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dwave%2Blength"><span id="translatedtitle">Inception length to a fully-developed fin-generated <span class="hlt">shock</span> wave boundary-<span class="hlt">layer</span> interaction</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Lu, Frank K.; Settles, Gary S.</p> <p>1989-01-01</p> <p>An experimental study of fin-generated <span class="hlt">shock</span> wave turbulent boundary-<span class="hlt">layer</span> interactions confirmed previous observations that, sufficiently far from the fin apex, such interactions become conical. The inception length to conical symmetry was found to increase weakly with Mach number for Mach numbers from 2.5 to 4 and fin angles from 4 to 22 deg. For the range of interactions examined, the inception length was found to depend primarily upon the inviscid <span class="hlt">shock</span> angle, this angle ranging from 21 to 40 deg. The behavior of the inception length with <span class="hlt">shock</span> angle can be broadly divided into two categories. For 'weak' interactions with <span class="hlt">shock</span> angles less than about 35 deg, the inception length decreased as the <span class="hlt">shock</span> angle increased. For 'strong' interactions with <span class="hlt">shock</span> angles greater than about 35 deg, the inception region was small and was approximately constant at three boundary-<span class="hlt">layer</span> thicknesses in length. In the latter, strong interaction case, the inception length was an order of magnitude smaller than that found in the weakest interactions examined, to the extent that strong interactions were practically fully-developed from the apex.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22252076','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22252076"><span id="translatedtitle"><span class="hlt">Shock</span> timing measurements and analysis in deuterium-tritium-ice <span class="hlt">layered</span> capsule implosions on NIF</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Robey, H. F.; Celliers, P. M.; Moody, J. D.; Sater, J.; Parham, T.; Kozioziemski, B.; Dylla-Spears, R.; Ross, J. S.; LePape, S.; Ralph, J. E.; Dewald, E. L.; Berzak Hopkins, L.; Kroll, J. J.; Yoxall, B. E.; Hamza, A. V.; Landen, O. L.; Edwards, M. J.; Hohenberger, M.; Boehly, T. R.; Nikroo, A.</p> <p>2014-02-15</p> <p>Recent advances in <span class="hlt">shock</span> timing experiments and analysis techniques now enable <span class="hlt">shock</span> measurements to be performed in cryogenic deuterium-tritium (DT) ice <span class="hlt">layered</span> capsule implosions on the National Ignition Facility (NIF). Previous measurements of <span class="hlt">shock</span> timing in inertial confinement fusion implosions [Boehly et al., Phys. Rev. Lett. 106, 195005 (2011); Robey et al., Phys. Rev. Lett. 108, 215004 (2012)] were performed in surrogate targets, where the solid DT ice shell and central DT gas were replaced with a continuous liquid deuterium (D2) fill. These previous experiments pose two surrogacy issues: a material surrogacy due to the difference of species (D2 vs. DT) and densities of the materials used and a geometric surrogacy due to presence of an additional interface (ice/gas) previously absent in the liquid-filled targets. This report presents experimental data and a new analysis method for validating the assumptions underlying this surrogate technique. Comparison of the data with simulation shows good agreement for the timing of the first three <span class="hlt">shocks</span>, but reveals a considerable discrepancy in the timing of the 4th <span class="hlt">shock</span> in DT ice <span class="hlt">layered</span> implosions. Electron preheat is examined as a potential cause of the observed discrepancy in the 4th <span class="hlt">shock</span> timing.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015APS..DFDG40003S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015APS..DFDG40003S"><span id="translatedtitle">Diffusion-flame ignition by <span class="hlt">shock</span>-wave impingement on a supersonic mixing <span class="hlt">layer</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sanchez, Antonio L.; Huete, Cesar; Williams, Forman A.; Urzay, Javier</p> <p>2015-11-01</p> <p>Ignition in a supersonic mixing <span class="hlt">layer</span> interacting with an oblique <span class="hlt">shock</span> wave is investigated analytically and numerically under conditions such that the post-<span class="hlt">shock</span> flow remains supersonic. The study requires consideration of the structure of the post-<span class="hlt">shock</span> ignition kernel that is found to exist around the point of maximum temperature, which may be located either near the edge of the mixing <span class="hlt">layer</span> or in its interior. The ignition kernel displays a balance between the rates of chemical reaction and of post-<span class="hlt">shock</span> flow expansion, including the acoustic interactions of the chemical heat release with the <span class="hlt">shock</span> wave, leading to increased front curvature. The analysis, which adopts a one-step chemistry model with large activation energy, indicates that ignition develops as a fold bifurcation, the turning point in the diagram of the peak perturbation induced by the chemical reaction as a function of the Damköhler number providing the critical conditions for ignition. Subsequent to ignition the lead <span class="hlt">shock</span> will rapidly be transformed into a thin detonation on the fuel side of the ignition kernel, and, under suitable conditions, a deflagration may extend far downstream, along with the diffusion flame that must separate the rich and lean reaction products.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/878827','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/878827"><span id="translatedtitle">Steady-State Electrostatic <span class="hlt">Layers</span> From Weibel Instability in Relativistic Collisionless <span class="hlt">Shocks</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Milosavljevic, Milos; Nakar, Ehud; Spitkovsky, Anatoly; /KIPAC, Menlo Park</p> <p>2005-08-04</p> <p>It is generally accepted that magnetic fields generated in the nonlinear development of the transverse Weibel instability provide effective collisionality in unmagnetized collisionless <span class="hlt">shocks</span>. Recently, extensive two and three dimensional simulations improved our understanding of the growth and saturation of the instability in colliding plasma shells. However, the steady-state structure of the <span class="hlt">shock</span> wave transition <span class="hlt">layers</span> remains poorly understood. We use basic physical considerations and order-of-magnitude arguments to study the steady state structure in relativistic unmagnetized collisionless <span class="hlt">shocks</span> in pair plasmas. The <span class="hlt">shock</span> contains an electrostatic <span class="hlt">layer</span> resulting from the formation of stationary, magnetically-focused current filaments. The filaments form where the cold upstream plasma and the counterstreaming thermal plasma interpenetrate. The filaments are not entirely neutral and strong electrostatic fields are present. Most of the downstream particles cannot cross this <span class="hlt">layer</span> into the upstream because they are trapped by the electrostatic field. We identify the critical location in the <span class="hlt">shock</span> transition <span class="hlt">layer</span> where the electromagnetic field ceases to be static. At this location, the degree of charge separation in the filaments reaches a maximum value, the current inside the filaments comes close to the Alfven limit, and the phase space distribution function starts to isotropize. We argue that the radius of the current filaments upstream of the critical location is about twice the upstream plasma skin depth. Finally, we show that some downstream particles cross the electrostatic <span class="hlt">layer</span> and run ahead of the <span class="hlt">shock</span> into the preshock medium without causing instability. These particles may play an important role in particle acceleration.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015M%26PS...50..483H&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015M%26PS...50..483H&link_type=ABSTRACT"><span id="translatedtitle">A search for <span class="hlt">shocked</span> quartz grains in the Allerød-Younger Dryas boundary <span class="hlt">layer</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hoesel, Annelies; Hoek, Wim Z.; Pennock, Gillian M.; Kaiser, Knut; Plümper, Oliver; Jankowski, Michal; Hamers, Maartje F.; Schlaak, Norbert; Küster, Mathias; Andronikov, Alexander V.; Drury, Martyn R.</p> <p>2015-03-01</p> <p>The Younger Dryas impact hypothesis suggests that multiple airbursts or extraterrestrial impacts occurring at the end of the Allerød interstadial resulted in the Younger Dryas cold period. So far, no reproducible, diagnostic evidence has, however, been reported. Quartz grains containing planar deformation features (known as <span class="hlt">shocked</span> quartz grains), are considered a reliable indicator for the occurrence of an extraterrestrial impact when found in a geological setting. Although alleged <span class="hlt">shocked</span> quartz grains have been reported at a possible Allerød-Younger Dryas boundary <span class="hlt">layer</span> in Venezuela, the identification of <span class="hlt">shocked</span> quartz in this <span class="hlt">layer</span> is ambiguous. To test whether <span class="hlt">shocked</span> quartz is indeed present in the proposed impact <span class="hlt">layer</span>, we investigated the quartz fraction of multiple Allerød-Younger Dryas boundary <span class="hlt">layers</span> from Europe and North America, where proposed impact markers have been reported. Grains were analyzed using a combination of light and electron microscopy techniques. All samples contained a variable amount of quartz grains with (sub)planar microstructures, often tectonic deformation lamellae. A total of one quartz grain containing planar deformation features was found in our samples. This <span class="hlt">shocked</span> quartz grain comes from the Usselo palaeosol at Geldrop Aalsterhut, the Netherlands. Scanning electron microscopy cathodoluminescence imaging and transmission electron microscopy imaging, however, show that the planar deformation features in this grain are healed and thus likely to be older than the Allerød-Younger Dryas boundary. We suggest that this grain was possibly eroded from an older crater or distal ejecta <span class="hlt">layer</span> and later redeposited in the European sandbelt. The single <span class="hlt">shocked</span> quartz grain at this moment thus cannot be used to support the Younger Dryas impact hypothesis.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1996ShWav...6....1J&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1996ShWav...6....1J&link_type=ABSTRACT"><span id="translatedtitle"><span class="hlt">Shock</span> induced Richtmyer-Meshkov instability in the presence of a wall boundary <span class="hlt">layer</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jourdan, G.; Billiotte, M.; Houas, L.</p> <p>1996-06-01</p> <p>An experimental investigation on gaseous mixing zones originated from the Richtmyer-Meshkov instability has been undertaken in a square cross section <span class="hlt">shock</span> tube. Mass concentration fields, of one of the two mixing constituents, have been determined within the mixing zone when the <span class="hlt">shock</span> wave passes from the heavy gas to the light one, from one gas to an other of close density, and from the light gas to the heavy one. Results have been obtained before and after the coming back of the reflected <span class="hlt">shock</span> wave. The diagnostic method is based on the infrared absorption of one of the two constituents of the mixing zone. It is shown that the mixing zone is strongly deformed by the wall boundary <span class="hlt">layer</span>. The consequence is the presence of strong gradients of concentration in the direction perpendicular to the <span class="hlt">shock</span> wave propagation. Finally, it is pointed out that the mixing goes more homogeneous when the Atwood number tends to zero.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015PrAeS..74...16P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015PrAeS..74...16P"><span id="translatedtitle">Micro-vortex generators for <span class="hlt">shock</span> wave/boundary <span class="hlt">layer</span> interactions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Panaras, Argyris G.; Lu, Frank K.</p> <p>2015-04-01</p> <p>The effect of micro-vortex generators (MVGs) on <span class="hlt">shock</span> wave/boundary <span class="hlt">layer</span> interactions (SBLIs) has been reviewed. Experimental and computational evidence has been presented about the dominant role it has in the suppression of <span class="hlt">shock</span>-induced separation the pair of counter-rotating streamwise vortices, which appears downstream of the types of micro-vortex generators used in SBLIs; these streamwise vortices entrain high momentum fluid, increasing the boundary <span class="hlt">layer</span> velocity near the wall. The structure of the wake is examined in detail, with emphasis on the strength and decay of the streamwise vortices and on the ring-type or hairpin vortices which have been detected in the instantaneous flow around the wake. Evaluation of the ability of various types of MVGs to suppress <span class="hlt">shock</span>-induced separation is done. Topics which need to be further studied, like the structure of the flow around devices of small size and the effect of the Reynolds number, are suggested.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003PrAeS..39..121K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003PrAeS..39..121K"><span id="translatedtitle">Advances in CFD prediction of <span class="hlt">shock</span> wave turbulent boundary <span class="hlt">layer</span> interactions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Knight, Doyle; Yan, Hong; Panaras, Argyris G.; Zheltovodov, Alexander</p> <p>2003-04-01</p> <p>The paper presents a summary of recent computational fluid dynamics (CFD) simulations of <span class="hlt">shock</span> wave turbulent boundary <span class="hlt">layer</span> interactions. This survey was prepared as part of the activity of NATO RTO Working Group 10 which was established in December 1998, and considers results obtained subsequent to the previous survey paper on the same topic by Knight and Degrez (“<span class="hlt">Shock</span> Wave Boundary <span class="hlt">Layer</span> Interactions in High Mach Number Flows-A Critical Survey of Current CFD Prediction Capabilities”, AGARD Advisory Report AR-319, Volume II, December 1998). Five configurations are considered: 2-D compression corner, 2-D <span class="hlt">shock</span> impingement, 2-D expansion-compression corner, 3-D single fin and 3-D double fin. Recent direct numerical simulations (DNS), large eddy simulations (LES) and Reynolds-averaged Navier-Stokes (RANS) simulations are compared with experiment. The capabilities and limitations are described, and future research needs identified.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015shw2.conf.1411E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015shw2.conf.1411E"><span id="translatedtitle">Laser Energy Deposition for <span class="hlt">Shock</span> Wave Boundary <span class="hlt">Layer</span> Control at Supersonic Speeds</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Erdem, E.; Kontis, K.; Osuka, T.; Majima, R.; Tamba, T.; Sasoh, Akihiro</p> <p></p> <p><span class="hlt">Shock</span> Wave Boundary <span class="hlt">Layer</span> Interactions (SWBLIs) can induce separation which causes loss of a control surface effectiveness, drop of an air intake efficiency and it may be the origin of large scale fluctuations such as air-intake buzz, buffeting or fluctuating side loads in separated propulsive nozzles</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19740027814&hterms=1575&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3D%2526%25231575','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19740027814&hterms=1575&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3D%2526%25231575"><span id="translatedtitle">Three-dimensional separation for interaction of <span class="hlt">shock</span> waves with turbulent boundary <span class="hlt">layers</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Goldberg, T. J.</p> <p>1973-01-01</p> <p>For the interaction of <span class="hlt">shock</span> waves with turbulent boundary <span class="hlt">layers</span>, obtained experimental three-dimensional separation results and correlations with earlier two-dimensional and three-dimensional data are presented. It is shown that separation occurs much earlier for turbulent three-dimensional than for two-dimensional flow at hypersonic speeds.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17.2764H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17.2764H"><span id="translatedtitle">Evidence of downstream high speed jets by a non-stationary and rippled front of quasi-<span class="hlt">parallel</span> <span class="hlt">shock</span>: 2-D hybrid simulations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hao, Yufei; Lu, Quanming; Lembege, Bertrand; Huang, Can; Wu, Mingyu; Guo, Fan; Shan, Lican; Zheng, Jian; Wang, Shui</p> <p>2015-04-01</p> <p>Experimental observations from space missions (including Cluster more recently) have clearly revealed the existence of high speed jets (HSJ) in the downstream region of the quasi-<span class="hlt">parallel</span> terrestrial bow <span class="hlt">shock</span>. Presently, two-dimensional (2-D) hybrid simulations are performed to reproduce and investigate the formation of such HSJ through a rippled quasi-<span class="hlt">parallel</span> <span class="hlt">shock</span> front. The simulation results show (i) that such <span class="hlt">shock</span> fronts are strongly nonstationary (self reformation) along the <span class="hlt">shock</span> normal, and (ii) that ripples are evidenced along the <span class="hlt">shock</span> front as the upstream ULF waves (excited by interaction between incoming and reflected ions) are convected back to the front by the solar wind and contribute to the rippling formation. Then, these ripples are inherent structures of a quasi-<span class="hlt">parallel</span> <span class="hlt">shock</span> and the self reformation of the <span class="hlt">shock</span> is not synchronous along the surface of the <span class="hlt">shock</span> front. As a consequence, new incoming solar wind ions interact differently at different locations along the <span class="hlt">shock</span> surface, and some can be only deflected (instead of being decelerated) at locations where ripples are large enough to play the role of local « secondary » <span class="hlt">shock</span>. Therefore, the ion bulk velocity is also different locally after ions are transmitted dowstream, and local high-speed jets patterns are formed somewhere downstream. After a short reminder of main quasi-<span class="hlt">parallel</span> <span class="hlt">shock</span> features, this presentation will focus (i) on experimental observations of HSJ, (ii) on our preliminary simulation results obtained on HSJ, (iii) on their relationship with local bursty patterns of (turbulent) magnetic field evidenced at the front, and (iv) on the spatial and time scales of HSJ to be compared later on with experimental observations. Such downstream HSJ are shown to be generated by the nonstationary <span class="hlt">shock</span> front itself and do not require any upstream perturbations (such as tangential/rotational discontinuity, HFA, etc..) to be convected by the solar wind and to interact with the <span class="hlt">shock</span></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19950024920','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19950024920"><span id="translatedtitle">Numerical simulation of <span class="hlt">shock</span>/turbulent boundary <span class="hlt">layer</span> interaction</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Biringen, Sedat; Hatay, Ferhat F.</p> <p>1993-01-01</p> <p>Most flows of aerodynamic interest are compressible and turbulent. However, our present knowledge on the structures and mechanisms of turbulence is mostly based on incompressible flows. In the present work, compressibility effects in turbulent, high-speed, boundary <span class="hlt">layer</span> flows are systematically investigated using the Direct Numerical Simulation (DNS) approach. Three-dimensional, time-dependent, fully nonlinear, compressible Navier-Stokes equations were numerically integrated by high-order finite-difference methods; no modeling for turbulence is used during the solution because the available resolution is sufficient to capture the relevant scales. The boundary <span class="hlt">layer</span> problem deals with fully-turbulent compressible flows over flat geometries. Apart from its practical relevance to technological flows, turbulent compressible boundary <span class="hlt">layer</span> flow is the simplest experimentally realizable turbulent compressible flow. Still, measuring difficulties prohibit a detailed experimental description of the flow, especially in the near-wall region. DNS studies provide a viable means to probe the physics of compressible turbulence in this region. The focus of this work is to explore the paths of energy transfer through which compressible turbulence is sustained. The structural similarities and differences between the incompressible and compressible turbulence are also investigated. The energy flow patterns or energy cascades are found to be directly related to the evolution of vortical structures which are generated in the near-wall region. Near-wall structures, and mechanisms which are not readily accessible through physical experiments are analyzed and their critical role on the evolution and the behavior of the flow is documented extensively.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009A%26A...506.1215O&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009A%26A...506.1215O&link_type=ABSTRACT"><span id="translatedtitle">The propagation of the <span class="hlt">shock</span> wave from a strong explosion in a plane-<span class="hlt">parallel</span> stratified medium: the Kompaneets approximation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Olano, C. A.</p> <p>2009-11-01</p> <p>Context: Using certain simplifications, Kompaneets derived a partial differential equation that states the local geometrical and kinematical conditions that each surface element of a <span class="hlt">shock</span> wave, created by a point blast in a stratified gaseous medium, must satisfy. Kompaneets could solve his equation analytically for the case of a wave propagating in an exponentially stratified medium, obtaining the form of the <span class="hlt">shock</span> front at progressive evolutionary stages. Complete analytical solutions of the Kompaneets equation for <span class="hlt">shock</span> wave motion in further plane-<span class="hlt">parallel</span> stratified media were not found, except for radially stratified media. Aims: We aim to analytically solve the Kompaneets equation for the motion of a <span class="hlt">shock</span> wave in different plane-<span class="hlt">parallel</span> stratified media that can reflect a wide variety of astrophysical contexts. We were particularly interested in solving the Kompaneets equation for a strong explosion in the interstellar medium of the Galactic disk, in which, due to intense winds and explosions of stars, gigantic gaseous structures known as superbubbles and supershells are formed. Methods: Using the Kompaneets approximation, we derived a pair of equations that we call adapted Kompaneets equations, that govern the propagation of a <span class="hlt">shock</span> wave in a stratified medium and that permit us to obtain solutions in parametric form. The solutions provided by the system of adapted Kompaneets equations are equivalent to those of the Kompaneets equation. We solved the adapted Kompaneets equations for <span class="hlt">shock</span> wave propagation in a generic stratified medium by means of a power-series method. Results: Using the series solution for a <span class="hlt">shock</span> wave in a generic medium, we obtained the series solutions for four specific media whose respective density distributions in the direction perpendicular to the stratification plane are of an exponential, power-law type (one with exponent k=-1 and the other with k =-2) and a quadratic hyperbolic-secant. From these series solutions, we deduced</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1986jtht.confQ....H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1986jtht.confQ....H"><span id="translatedtitle">Relaminarization of the boundary <span class="hlt">layer</span> over a flat plate in <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>Hinckel, J. N.; Nagamatsu, H. T.</p> <p>1986-06-01</p> <p>The relaminarization of the boundary <span class="hlt">layer</span> over a flat plate in the <span class="hlt">shock</span> tube was investigated by using the partially reflected <span class="hlt">shock</span> wave technique. The flow Mach number was approximately 0.14, which corresponds to the inleft flow Mach number for the first row of vanes in a gas turbine. The thin film platinum heat gauges were used to measure the heat transfer rate and the Stanton number was calculated from the oscilloscope voltage traces. The Reynolds number was varied by changing the operation pressure of the <span class="hlt">shock</span> tube and the values varied from 2.3 x 10 to the 4th to 5.3 x 10 to the 5th. For a Reynolds number range of 7 x 10 to the 4th to 3.5 x 10 to the 5th, the relaminarization of the boundary <span class="hlt">layer</span> was observed. This phenomenon is due to the decay of the turbulence level in the flow as the reflected <span class="hlt">shock</span> wave moves upstream from the flat plate. As the Reynolds number increased, the relaminarization was delayed and the delay was related to the turbulence generated by the reflected <span class="hlt">shock</span> wave.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006APS..GECSR2036D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006APS..GECSR2036D"><span id="translatedtitle">Double Electric <span class="hlt">Layer</span> in Stationary <span class="hlt">Shock</span> Structures of a Supersonic Flowing Afterglow</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Drake, D. J.; Upadyay, J.; Popovic, S.; Vuskovic, L.</p> <p>2006-10-01</p> <p>Mutual interaction between an acoustic <span class="hlt">shock</span> wave and weakly ionized gas produces many effects that have been studied in recent years [1]. This interaction is manifested as plasma-induced <span class="hlt">shock</span> dispersion and acceleration, <span class="hlt">shock</span> wave induced double electric <span class="hlt">layer</span>, localized increase of electron temperature and density, or enhancement of optical emission. A comprehensive review of this research and its significance for high-speed aerodynamics is given in Ref. [2]. We have performed experiments in a microwave flowing afterglow system and observed the enhancement of optical radiation in the interaction of a stationary <span class="hlt">shock</span> wave with weakly ionized argon at 100-600 Pa. The enhancement of optical radiation coincided with the calculated standoff distance of the detached shockwave. We studied the stationary <span class="hlt">shock</span> structures, mainly using the 4p excited state populations of argon, which were measured using absolute emission spectroscopy. Oblique <span class="hlt">shock</span> parameters were evaluated exactly for the given model geometry, which were usually spherical. We will present results at the conference. [1] S. Popovic, L. Vuskovic, Phys. Plasmas 6 (1999) 1448. [2] P. Bletzinger, B. N. Ganguly, D. Van Wie, A. Garscadden, J. Phys. D: App. Phys. 38 (2005) R33.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013PhDT.......105T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013PhDT.......105T"><span id="translatedtitle">Two-dimensional numerical investigation of a normal <span class="hlt">shock</span> wave boundary <span class="hlt">layer</span> interaction</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Turlin, Miranda P.</p> <p></p> <p><span class="hlt">Shock</span> wave boundary <span class="hlt">layer</span> interactions (SWBLIs) occur when a <span class="hlt">shock</span> wave meets a boundary <span class="hlt">layer</span>. This study aims to isolate the interaction through numerical investigation of a normal SWBLI and build knowledge of the computational fluid dynamics software, Wind-US 3.0. The test geometry, based on the experimental work of Bruce et al [16], contains a two-dimensional duct split into upper and lower channels by a <span class="hlt">shock</span> holding plate. The boundary conditions were based on experimental conditions, and include: an inlet Mach number of 1.6; inlet total pressure and temperature of 62.5 psi and 522 degrees R, respectively; and viscous walls on all physical surfaces. Downstream boundary conditions are varied in attempts to produce a correct <span class="hlt">shock</span> structure throughout the domain. This study uses two-dimensional structured grids containing approximately 832,000 elements. Wind-US solves the Reynolds-Averaged Navier-Stokes equations using Roe's second-order upwind-biased flux-difference splitting algorithm with a total variation diminishing (TVD) limiting parameter. The turbulence model selected for this study was the Menter SST k-o model. Attempts to produce the correct <span class="hlt">shock</span> structure have included varying the downstream boundary conditions, changing the number of cycles and associated Courant-Friedrichs-Lewy, TVD, and grid sequencing parameters. This study used several tutorial files available through the NPARC Alliance to establish the analysis settings needed to produce a <span class="hlt">shock</span> wave in the lower channel. This enables progress to be made on the next step of this project which is to simulate and analyze the interaction of a normal SWBLI in two dimensions. Results illustrate the correct combination of boundary conditions necessary to generate a <span class="hlt">shock</span> in the expected location. In addition, an appropriate zonal configuration has been determined to eliminate the horizontal zone interfaces which can cause non-physical behavior in those locations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JGRA..121.3310S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JGRA..121.3310S"><span id="translatedtitle">Reconnection <span class="hlt">layer</span> bounded by switch-off <span class="hlt">shocks</span>: Dayside magnetopause crossing by THEMIS D</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sonnerup, Bengt; Paschmann, Götz; Haaland, Stein; Phan, Tai; Eriksson, Stefan</p> <p>2016-04-01</p> <p>We discuss observations of reconnection, obtained by Time History of Events and Macroscale Interactions during Substorms (THEMIS) D during an outward bound traversal of the low-latitude dayside magnetopause. The reconnection signatures include high magnetic shear, a southward directed Alfvénic jet, bounded by slow-mode <span class="hlt">shocks</span> near the switch-off limit (as in the symmetric Petschek geometry), a small, sunward directed normal magnetic field and plasma inflow into the jet from both sides. We conclude that cold, unmeasured ionospheric ions helped establish the symmetry. The effective ion mass, estimated from the switch-off condition, was 2.39 amu on the magnetospheric side, where the number density was inferred from the spacecraft potential, and 1.09 amu on the magnetosheath side. After a modest pressure correction in the magnetospheric <span class="hlt">shock</span>, the MHD jump conditions for density, pressure, temperature, and entropy were well satisfied. The <span class="hlt">shock</span> jumps were much larger on the magnetosphere side than on the magnetosheath side; we show this to be a plasma β effect. The main dissipation mechanism appears to be irreversible transfer between thermal motion <span class="hlt">parallel</span> and perpendicular to the field, such that both <span class="hlt">shocks</span> bring about approximate downstream temperature isotropy. Hall currents and electric fields were present, albeit in a strongly asymmetric configuration. The magnetospheric <span class="hlt">shock</span> had longer duration than the magnetosheath one, possibly as a result of a nonconstant magnetopause speed. We infer an average earthward magnetopause speed (14 km/s), corresponding nominal <span class="hlt">shock</span> thicknesses (12 and 6 λi), dimensionless reconnection rates (0.061-0.085), and reconnection wedge angles (5° between <span class="hlt">shocks</span>; 13° between separatrices).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ShWav.tmp...46S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ShWav.tmp...46S"><span id="translatedtitle">Characterization of an incipiently separated <span class="hlt">shock</span> wave/turbulent boundary <span class="hlt">layer</span> interaction</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Schreyer, A.-M.; Dussauge, J.-P.; Krämer, E.</p> <p>2016-05-01</p> <p>The turbulence structure in a <span class="hlt">shock</span> wave/turbulent boundary <span class="hlt">layer</span> interaction at incipient separation was investigated in order to get insight into turbulence generation and amplification mechanisms in such flow fields. The flow along a two-dimensional 11.5° compression corner was studied experimentally at a Mach number of M=2.53 and with a momentum-thickness Reynolds number of Re_{θ }=5370 . From hot-wire boundary <span class="hlt">layer</span> traverses and surface heat-flux density fluctuation measurements with the fast-response atomic <span class="hlt">layer</span> thermopile, the turbulence structure and amplification was described. Space-time correlations of the mass-flux fluctuations across the boundary <span class="hlt">layer</span> and the surface heat-flux density fluctuations were measured to further characterize the development of the turbulence structure across the interaction. The large-scale boundary <span class="hlt">layer</span> structures are concealed by <span class="hlt">shock</span>-related effects in the strongly disturbed <span class="hlt">shock</span>-foot region. Shortly downstream, however, large-scale structures dominate the signal again, just as in the incoming flow. A mechanism explaining this behavior is suggested.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19910005246','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19910005246"><span id="translatedtitle">Numerical study of <span class="hlt">shock</span>-wave/boundary <span class="hlt">layer</span> interactions in premixed hydrogen-air hypersonic flows</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Yungster, Shaye</p> <p>1990-01-01</p> <p>A computational study of <span class="hlt">shock</span> wave/boundary <span class="hlt">layer</span> interactions involving premixed combustible gases, and the resulting combustion processes is presented. The analysis is carried out using a new fully implicit, total variation diminishing (TVD) code developed for solving the fully coupled Reynolds-averaged Navier-Stokes equations and species continuity equations in an efficient manner. To accelerate the convergence of the basic iterative procedure, this code is combined with vector extrapolation methods. The chemical nonequilibrium processes are simulated by means of a finite-rate chemistry model for hydrogen-air combustion. Several validation test cases are presented and the results compared with experimental data or with other computational results. The code is then applied to study <span class="hlt">shock</span> wave/boundary <span class="hlt">layer</span> interactions in a ram accelerator configuration. Results indicate a new combustion mechanism in which a <span class="hlt">shock</span> wave induces combustion in the boundary <span class="hlt">layer</span>, which then propagates outwards and downstream. At higher Mach numbers, spontaneous ignition in part of the boundary <span class="hlt">layer</span> is observed, which eventually extends along the entire boundary <span class="hlt">layer</span> at still higher values of the Mach number.</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_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li class="active"><span>7</span></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_13");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_7 --> <div id="page_8" 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_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li class="active"><span>8</span></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_13");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="141"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19920071754&hterms=lateral+flow&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dlateral%2Bflow','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19920071754&hterms=lateral+flow&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dlateral%2Bflow"><span id="translatedtitle">A three-dimensional axisymmetric photochemical flow model of the cometary 'inner' <span class="hlt">shock</span> <span class="hlt">layer</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Damas, M. C.; Mendis, D. A.</p> <p>1992-01-01</p> <p>Assuming the Newtonian thin <span class="hlt">layer</span> approximation to describe the structure of the <span class="hlt">shock</span> <span class="hlt">layer</span> between the cometary 'ionopause' and the inner <span class="hlt">shock</span>, a 3D axisymmetric photochemical flow model of this <span class="hlt">layer</span> is constructed. While sources of ions in this <span class="hlt">layer</span> are the flow across the inner <span class="hlt">shock</span> and photoionization of neutrals within it, the sinks are the flow into the flanks and dissociative recombination, the latter being the dominant one. For Halley's comet at the time of the Giotto encounter, the calculated thickness of the <span class="hlt">layer</span> is very small, typically about 100 km for expected values of the dissociative-recombination coefficient. This is not inconsistent with the observations. The lateral flow speed near the point of encounter (inbound) is about 0.9 km/s, while the sonic line is at an angle of about 50 deg to the sun-comet line. Testing the validity of this model will have to await a cometary rendezvous mission such as the proposed CRAF/Cassini mission.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19970009931','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19970009931"><span id="translatedtitle">Experimental Investigation of Crossing <span class="hlt">Shock</span> Wave-Turbulent Boundary <span class="hlt">Layer</span>-Bleed Interaction</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Kim, Hyun; Hingst, Warren R.; Davis, David O.</p> <p>1996-01-01</p> <p>Results of an experimental investigation of a symmetric crossing <span class="hlt">shock</span> wave/turbulent boundary <span class="hlt">layer</span>/bleed interaction are presented for a freestream unit Reynolds number of 1.68 x 10(exp 7)/m, a Mach number of 2.81, and deflection angles of 8 degrees. The data obtained in this study are bleed mass flow rate using a trace gas technique, qualitative information in the form of oil flow visualization, flow field Pitot pressures, and static pressure measurements using pressure sensitive paint. The main objective of this test is two-fold. First, this study is conducted to explore boundary <span class="hlt">layer</span> control through mass flow removal near a large region of separated flow caused by the interaction of a double fin-induced <span class="hlt">shock</span> wave and an incoming turbulent boundary <span class="hlt">layer</span>. Also, a comprehensive data set is needed for computational fluid dynamics code validation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JThSc..24..510F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JThSc..24..510F"><span id="translatedtitle"><span class="hlt">Shock</span> wave boundary <span class="hlt">layer</span> interaction on suction side of compressor profile in single passage test section</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Flaszynski, Pawel; Doerffer, Piotr; Szwaba, Ryszard; Kaczynski, Piotr; Piotrowicz, Michal</p> <p>2015-11-01</p> <p>The <span class="hlt">shock</span> wave boundary <span class="hlt">layer</span> interaction on the suction side of transonic compressor blade is one of the main objectives of TFAST project (Transition Location Effect on <span class="hlt">Shock</span> Wave Boundary <span class="hlt">Layer</span> Interaction). In order to investigate the flow structure on the suction side of a profile, a design of a generic test section in linear transonic wind tunnel was proposed. The experimental and numerical results for the flow structure investigations are shown for the flow conditions as the existing ones on the suction side of the compressor profile. Near the sidewalls the suction slots are applied for the corner flow structure control. It allows to control the Axial Velocity Density Ratio (AVDR), important parameter for compressor cascade investigations. Numerical results for Explicit Algebraic Reynolds Stress Model with transition modeling are compared with oil flow visualization, schlieren and Pressure Sensitive Paint. Boundary <span class="hlt">layer</span> transition location is detected by Temperature Sensitive Paint.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19830013929','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19830013929"><span id="translatedtitle">Experimental investigation of a two-dimensional <span class="hlt">shock</span>-turbulent boundary <span class="hlt">layer</span> interaction with bleed</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hingst, W. R.; Tanji, F. T.</p> <p>1983-01-01</p> <p>The two-dimensional interaction of an oblique <span class="hlt">shock</span> wave with a turbulent boundary <span class="hlt">layer</span> that included the effect of bleed was examined experimentally using a <span class="hlt">shock</span> generator mounted across a supersonic wind tunnel The studies were performed at Mach numbers 2.5 and 2.0 and unit Reynolds number of approximately 2.0 x 10 to the 7th/meter. The study includes surface oil flow visualization, wall static pressure distributions and boundary <span class="hlt">layer</span> pitot pressure profiles. In addition, the variation of the local bleed rates were measured. The results show the effect of the bleed on the boundary <span class="hlt">layer</span> as well as the effect of the flow conditions on the local bleed rate.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19930064187&hterms=wave+equation+2D&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dwave%2Bequation%2B2D','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19930064187&hterms=wave+equation+2D&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dwave%2Bequation%2B2D"><span id="translatedtitle">An investigation of <span class="hlt">shock</span> wave turbulent boundary <span class="hlt">layer</span> interaction with bleed through slanted slots</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hamed, A.; Yeuan, J. J.; Shih, S. H.</p> <p>1993-01-01</p> <p>Flow-field characteristics are simulated numerically in an oblique <span class="hlt">shock</span> wave/turbulent boundary <span class="hlt">layer</span> interactions with six different bleed slot configurations. The strong conservation-law form of the 2D compressible Navier-Stokes equations and the k-epsilon equations are solved throughout the interaction region and inside the bleed slot. The computed results are presented for a normal and 20-deg slanted bleed slots at three different locations, upstream, across and downstream of the impingement point of an oblique <span class="hlt">shock</span> of sufficient strength to cause boundary <span class="hlt">layer</span> separation without bleed. The detailed flow characteristics in the interaction zone and inside the bleed slot are compared for the different bleed slot configurations. The resulting surface pressure and shear stress distributions as well as the boundary <span class="hlt">layer</span> characteristics downstream of the interaction region are also presented for the mix bleed configurations at different bleed mass flows up to choking.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19750004171','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19750004171"><span id="translatedtitle">Weak incident <span class="hlt">shock</span> interactions with Mach 8 laminar boundary <span class="hlt">layers</span>. [of flat plate</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Kaufman, L. G., II; Johnson, C. B.</p> <p>1974-01-01</p> <p>Weak <span class="hlt">shock</span>-wave interactions with boundary <span class="hlt">layers</span> on a flat plate were investigated experimentally in Mach 8 variable-density tunnel for plate-length Reynolds numbers. The undisturbed boundary <span class="hlt">layers</span> were laminar over the entire plate length. Pressure and heat-transfer distributions were obtained for wedge-generated incident <span class="hlt">shock</span> waves that resulted in pressure rises ranging from 1.36 to 4.46 (both nonseparated and separated boundary-<span class="hlt">layer</span> flows). The resulting heat-transfer amplifications ranged from 1.45 to 14. The distributions followed established trends for nonseparated flows, for incipient separation, and for laminar free-interaction pressure rises. The experimental results corroborated established trends for the extent of the pressure rise and for certain peak heat-transfer correlations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20100037235','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20100037235"><span id="translatedtitle">CFL3D Contribution to the AIAA Supersonic <span class="hlt">Shock</span> Boundary <span class="hlt">Layer</span> Interaction Workshop</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Rumsey, Christopher L.</p> <p>2010-01-01</p> <p>This paper documents the CFL3D contribution to the AIAA Supersonic <span class="hlt">Shock</span> Boundary <span class="hlt">Layer</span> Interaction Workshop, held in Orlando, Florida in January 2010. CFL3D is a Reynolds-averaged Navier-Stokes code. Four <span class="hlt">shock</span> boundary <span class="hlt">layer</span> interaction cases are computed using a one-equation turbulence model widely used for other aerodynamic problems of interest. Two of the cases have experimental data available at the workshop, and two of the cases do not. The effect of grid, flux scheme, and thin-<span class="hlt">layer</span> approximation are investigated. Comparisons are made to the available experimental data. All four cases exhibit strong three-dimensional behavior in and near the interaction regions, resulting from influences of the tunnel side-walls.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20130010178','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20130010178"><span id="translatedtitle">Wind-US Code Contributions to the First AIAA <span class="hlt">Shock</span> Boundary <span class="hlt">Layer</span> Interaction Prediction Workshop</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Georgiadis, Nicholas J.; Vyas, Manan A.; Yoder, Dennis A.</p> <p>2013-01-01</p> <p>This report discusses the computations of a set of <span class="hlt">shock</span> wave/turbulent boundary <span class="hlt">layer</span> interaction (SWTBLI) test cases using the Wind-US code, as part of the 2010 American Institute of Aeronautics and Astronautics (AIAA) <span class="hlt">shock</span>/boundary <span class="hlt">layer</span> interaction workshop. The experiments involve supersonic flows in wind tunnels with a <span class="hlt">shock</span> generator that directs an oblique <span class="hlt">shock</span> wave toward the boundary <span class="hlt">layer</span> along one of the walls of the wind tunnel. The Wind-US calculations utilized structured grid computations performed in Reynolds-averaged Navier-Stokes mode. Four turbulence models were investigated: the Spalart-Allmaras one-equation model, the Menter Baseline and Shear Stress Transport k-omega two-equation models, and an explicit algebraic stress k-omega formulation. Effects of grid resolution and upwinding scheme were also considered. The results from the CFD calculations are compared to particle image velocimetry (PIV) data from the experiments. As expected, turbulence model effects dominated the accuracy of the solutions with upwinding scheme selection indicating minimal effects.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/6901192','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/6901192"><span id="translatedtitle">Instability growth patterns of a <span class="hlt">shock</span>-accelerated thin fluid <span class="hlt">layer</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Jacobs, J.W. ); Klein, D.L.; Jenkins, D.G.; Benjamin, R.F. )</p> <p>1993-02-01</p> <p>Laser-induced fluorescence imaging of a <span class="hlt">shock</span>-accelerated thin gas <span class="hlt">layer</span>, produced by a planar SF[sub 6] jet in air, shows multiple flow evolutions. Richtmyer-Meshkov instability causes spatially periodic perturbations initially imposed on the jet to develop into one of three distinct flow patterns, indicating nonlinear instability growth. Slight differences in the vorticity distribution deposited on the air-SF[sub 6] interfaces by the <span class="hlt">shock</span> interaction produce a bifurcated flow, observed as mushroom-shaped or sinuous-shaped interfacial patterns.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19900043444&hterms=Chalk&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DChalk','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19900043444&hterms=Chalk&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DChalk"><span id="translatedtitle">Color surface-flow visualization of fin-generated <span class="hlt">shock</span> wave boundary-<span class="hlt">layer</span> interactions</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Lu, F. K.; Settles, G. S.</p> <p>1990-01-01</p> <p>Kerosene-lampblack mixtures with addition of a ground colored chalk were used in an experiment on visualizing surface flows of swept <span class="hlt">shock</span> boundary-<span class="hlt">layer</span> interactions. The results show that contrasting colors intensify the visualization of different regions of the interaction surface, and help the eye in following the fine streaks to locate the upstream influence. The study confirms observations of the separation occurring at <span class="hlt">shock</span> strength below accepted values. The superiority of the reported technique over the previous monochrome technique is demonstrated.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.9404A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.9404A"><span id="translatedtitle">Folder: a MATLAB-based tool for modelling deformation in <span class="hlt">layered</span> media subject to <span class="hlt">layer</span> <span class="hlt">parallel</span> shortening or extension</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Adamuszek, Marta; Dabrowski, Marcin; Schmid, Daniel W.</p> <p>2016-04-01</p> <p>We present Folder, a numerical tool to simulate and analyse the structure development in mechanically <span class="hlt">layered</span> media during the <span class="hlt">layer</span> <span class="hlt">parallel</span> shortening or extension. Folder includes a graphical user interface that allows for easy designing of complex geometrical models, defining material parameters (including linear and non-linear rheology), and specifying type and amount of deformation. It also includes a range of features that facilitate the visualization and examination of various relevant quantities e.g. velocities, stress, rate of deformation, pressure, and finite strain. Folder contains a separate application, which illustrates analytical solutions of growth rate spectra for <span class="hlt">layer</span> <span class="hlt">parallel</span> shortening and extension of a single viscous <span class="hlt">layer</span>. In the study, we also demonstrate a Folder application, where the role of confinement on the growth rate spectrum and the fold shape evolution during the deformation of a single <span class="hlt">layer</span> subject to the <span class="hlt">layer</span> <span class="hlt">parallel</span> shortening is presented. In the case of the linear viscous materials used for the <span class="hlt">layer</span> and matrix, the close wall proximity leads to a decrease of the growth rate values. The decrease is more pronounced for the larger wavelengths than for the smaller wavelengths. The growth rate reduction is greater when the walls are set closer to the <span class="hlt">layer</span>. The presence of the close confinement can also affect the wavelength selection process and significantly shift the position of the dominant wavelength. The influence of the wall proximity on the growth rate spectrum for the case of non-linear viscous materials used for the <span class="hlt">layer</span> and/or matrix is very different as compared to the linear viscous case. We observe a multiple maxima in the growth rate spectrum. The number of the growth rate maxima, their value and the position strongly depend on the closeness of the confinement. The maximum growth rate value for a selected range of <span class="hlt">layer</span>-wall distances is much larger than in the case when the confinement effect is not taken</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015APS..DFDL21008G&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015APS..DFDL21008G&link_type=ABSTRACT"><span id="translatedtitle">Effect of Pulsed Plasma Jets on the Recovering Boundary <span class="hlt">Layer</span> Downstream of a Reflected <span class="hlt">Shock</span> Interaction</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Greene, Benton; Clemens, Noel; Magari, Patrick; Micka, Daniel; Ueckermann, Mattheus</p> <p>2015-11-01</p> <p><span class="hlt">Shock</span>-induced turbulent boundary <span class="hlt">layer</span> separation can have many detrimental effects in supersonic inlets including flow distortion and instability, structural fatigue, poor pressure recovery, and unstart. The current study investigates the effect of pulsed plasma jets on the recovering boundary <span class="hlt">layer</span> downstream of a reflected <span class="hlt">shock</span> wave-boundary <span class="hlt">layer</span> interaction. The effects of pitch and skew angle of the jet as well as the heating parameter and discharge time scale are tested using several pulsing frequencies. In addition, the effect of the plasma jets on the undisturbed boundary <span class="hlt">layer</span> at 6 mm and 11 mm downstream of the jets is measured. A pitot-static pressure probe is used to measure the velocity profile of the boundary <span class="hlt">layer</span> 35 mm downstream of the plasma jets, and the degree of boundary <span class="hlt">layer</span> distortion is compared between the different models and run conditions. Additionally, the effect of each actuator configuration on the shape of the mean separated region is investigated using surface oil flow visualization. Previous studies with lower energy showed a weak effect on the downstream boundary <span class="hlt">layer</span>. The current investigation will attempt to increase this effect using a higher-energy discharge. Funded by AFRL through and SBIR in collaboration with Creare, LLC.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19820014335','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19820014335"><span id="translatedtitle">Investigation of passive <span class="hlt">shock</span> wave-boundary <span class="hlt">layer</span> control for transonic airfoil drag reduction</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Nagamatsu, H. T.; Brower, W. B., Jr.; Bahi, L.; Ross, J.</p> <p>1982-01-01</p> <p>The passive drag control concept, consisting of a porous surface with a cavity beneath it, was investigated with a 12-percent-thick circular arc and a 14-percent-thick supercritical airfoil mounted on the test section bottom wall. The porous surface was positioned in the <span class="hlt">shock</span> wave/boundary <span class="hlt">layer</span> interaction region. The flow circulating through the porous surface, from the downstream to the upstream of the terminating <span class="hlt">shock</span> wave location, produced a lambda <span class="hlt">shock</span> wave system and a pressure decrease in the downstream region minimizing the flow separation. The wake impact pressure data show an appreciably drag reduction with the porous surface at transonic speeds. To determine the optimum size of porosity and cavity, tunnel tests were conducted with different airfoil porosities, cavities and flow Mach numbers. A higher drag reduction was obtained by the 2.5 percent porosity and the 1/4-inch deep cavity.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19850027059','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19850027059"><span id="translatedtitle">Computation of three-dimensional <span class="hlt">shock</span> wave and boundary-<span class="hlt">layer</span> interactions</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hung, C. M.</p> <p>1985-01-01</p> <p>Computations of the impingement of an oblique <span class="hlt">shock</span> wave on a cylinder and a supersonic flow past a blunt fin mounted on a plate are used to study three dimensional <span class="hlt">shock</span> wave and boundary <span class="hlt">layer</span> interaction. In the impingement case, the problem of imposing a planar impinging <span class="hlt">shock</span> as an outer boundary condition is discussed and the details of particle traces in windward and leeward symmetry planes and near the body surface are presented. In the blunt fin case, differences between two dimensional and three dimensional separation are discussed, and the existence of an unique high speed, low pressure region under the separated spiral vortex core is demonstrated. The accessibility of three dimensional separation is discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AIPC.1754d0024J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AIPC.1754d0024J"><span id="translatedtitle">A computational study on oblique <span class="hlt">shock</span> wave-turbulent boundary <span class="hlt">layer</span> interaction</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Joy, Md. Saddam Hossain; Rahman, Saeedur; Hasan, A. B. M. Toufique; Ali, M.; Mitsutake, Y.; Matsuo, S.; Setoguchi, T.</p> <p>2016-07-01</p> <p>A numerical computation of an oblique <span class="hlt">shock</span> wave incident on a turbulent boundary <span class="hlt">layer</span> was performed for free stream flow of air at M∞ = 2.0 and Re1 = 10.5×106 m-1. The oblique <span class="hlt">shock</span> wave was generated from a 8° wedge. Reynolds averaged Navier-Stokes (RANS) simulation with k-ω SST turbulence model was first utilized for two dimensional (2D) steady case. The results were compared with the experiment at the same flow conditions. Further, to capture the unsteadiness, a 2D Large Eddy Simulation (LES) with sub-grid scale model WMLES was performed which showed the unsteady effects. The frequency of the <span class="hlt">shock</span> oscillation was computed and was found to be comparable with that of experimental measurement.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20070003681','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20070003681"><span id="translatedtitle">Assessment of Turbulent <span class="hlt">Shock</span>-Boundary <span class="hlt">Layer</span> Interaction Computations Using the OVERFLOW Code</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Oliver, A. B.; Lillard, R. P.; Schwing, A. M.; Blaisdell, G> A.; Lyrintzis, A. S.</p> <p>2007-01-01</p> <p>The performance of two popular turbulence models, the Spalart-Allmaras model and Menter s SST model, and one relatively new model, Olsen & Coakley s Lag model, are evaluated using the OVERFLOWcode. Turbulent <span class="hlt">shock</span>-boundary <span class="hlt">layer</span> interaction predictions are evaluated with three different experimental datasets: a series of 2D compression ramps at Mach 2.87, a series of 2D compression ramps at Mach 2.94, and an axisymmetric coneflare at Mach 11. The experimental datasets include flows with no separation, moderate separation, and significant separation, and use several different experimental measurement techniques (including laser doppler velocimetry (LDV), pitot-probe measurement, inclined hot-wire probe measurement, preston tube skin friction measurement, and surface pressure measurement). Additionally, the OVERFLOW solutions are compared to the solutions of a second CFD code, DPLR. The predictions for weak <span class="hlt">shock</span>-boundary <span class="hlt">layer</span> interactions are in reasonable agreement with the experimental data. For strong <span class="hlt">shock</span>-boundary <span class="hlt">layer</span> interactions, all of the turbulence models overpredict the separation size and fail to predict the correct skin friction recovery distribution. In most cases, surface pressure predictions show too much upstream influence, however including the tunnel side-wall boundary <span class="hlt">layers</span> in the computation improves the separation predictions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..1615976K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..1615976K"><span id="translatedtitle">Enhanced diffusive ion scattering in front of the Earth's quasi-<span class="hlt">parallel</span> bow <span class="hlt">shock</span>: a case study</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kis, Arpad; Scholer, Manfred; Klecker, Berndt; Lucek, Elisabeth; Dandouras, Iannis; Lemperger, István; Wesztergom, Viktor; Novák, Attila; Szalai, Sándor</p> <p>2014-05-01</p> <p>In our study we report on observations of energetic ions upstream of the Earth's quasi-<span class="hlt">parallel</span> bow <span class="hlt">shock</span> by Cluster at times of large inter-spacecraft separation distance. For the analysis we use the ion data provided by the CIS-HIA in the 10-32 keV energy range and the magnetic data recorded by the FGM instrument. We determine the spatial gradient of partial energetic ion densities at various distances from the bow <span class="hlt">shock</span>. The gradient in all energy channels decreases exponentially with distance and the e-folding distance of the gradients depends approximately linearly on energy but there is a significant difference in their values obtained at the observed three upstream ion events. We demonstrate for the first time that under specific interplanetary conditions the mechanism of the diffuse ion scattering can change significantly and results in an anomalous diffusive process charactized by an unusually small e-folding distance.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016JHyd..535..737Z&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016JHyd..535..737Z&link_type=ABSTRACT"><span id="translatedtitle">Double-<span class="hlt">layer</span> <span class="hlt">parallelization</span> for hydrological model calibration on HPC systems</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhang, Ang; Li, Tiejian; Si, Yuan; Liu, Ronghua; Shi, Haiyun; Li, Xiang; Li, Jiaye; Wu, Xia</p> <p>2016-04-01</p> <p>Large-scale problems that demand high precision have remarkably increased the computational time of numerical simulation models. Therefore, the <span class="hlt">parallelization</span> of models has been widely implemented in recent years. However, computing time remains a major challenge when a large model is calibrated using optimization techniques. To overcome this difficulty, we proposed a double-<span class="hlt">layer</span> <span class="hlt">parallel</span> system for hydrological model calibration using high-performance computing (HPC) systems. The lower-<span class="hlt">layer</span> <span class="hlt">parallelism</span> is achieved using a hydrological model, the Digital Yellow River Integrated Model, which was <span class="hlt">parallelized</span> by decomposing river basins. The upper-<span class="hlt">layer</span> <span class="hlt">parallelism</span> is achieved by simultaneous hydrological simulations with different parameter combinations in the same generation of the genetic algorithm and is implemented using the job scheduling functions of an HPC system. The proposed system was applied to the upstream of the Qingjian River basin, a sub-basin of the middle Yellow River, to calibrate the model effectively by making full use of the computing resources in the HPC system and to investigate the model's behavior under various parameter combinations. This approach is applicable to most of the existing hydrology models for many applications.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20030063222&hterms=mineral+discoveries&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dmineral%2Bdiscoveries','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20030063222&hterms=mineral+discoveries&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dmineral%2Bdiscoveries"><span id="translatedtitle">Discovery of coesite and <span class="hlt">shocked</span> quartz associated with the upper Eocene cpx spherule <span class="hlt">layer</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Liu, S.; Kyte, T.; Glass, B. P.</p> <p>2002-01-01</p> <p>At least two major impact ejecta <span class="hlt">layers</span> have been discovered in upper Eocene strata. The upper <span class="hlt">layer</span> is the North American microtektite <span class="hlt">layer</span>. lt consists tektite fragments, microtektites, and <span class="hlt">shocked</span> mineral grains (e.g., quartz and feldspar with multiple sets of PDFs, coesite and reidite (a high-pressure polymorph of zircon)). The slightly older <span class="hlt">layer</span> contains clinopyroxene-bearing (cpx) spherules and microtektites associated with an Ir anomaly. The North American tektite <span class="hlt">layer</span> may be derived from the Chesapeake Bay impact structure, and the cpx spherule <span class="hlt">layer</span> may from the Popigai impact crater. A cpx spherule <span class="hlt">layer</span> associated with a positive Ir anomaly was recently found at ODP Site 709, western Indian Ocean. A large sample (Hole 709C, core 31, section 4, 145-150 cm), originally used for a study of interstitial water by shipboard scientists, was acquired for the purpose of recovering a large number of spherules for various petrographic and geochemical studies. A split of the sample (50.35 g) was disaggregated and wet-sieved. More than 17,000 cpx spherules and several hundred microtektites (larger than 125 microns) were recovered from the sample. Rare white opaque grains were observed in the 125-250 micron size fraction after removal of the carbonate component using dilute HCI. Seven of the white opaque grains were X-rayed using a Gandolfi camera and six were found to be coesite (probably mixed with lechatelierite). Eighty translucent colorless grains from the 63-125 micron size fraction were studied with a petrographic microscope. Four of the grains exhibit one to two sets of planar deformation features (PDFs). The only other possible known occurrence of <span class="hlt">shocked</span> minerals associated with the cpx spherule <span class="hlt">layer</span> is at Massignano, Italy, where pancake-shaped clay spherules (thought to be diagenetically altered cpx spherules are associated with a positive Ir anomaly and Ni- rich spinel crystals. <span class="hlt">Shocked</span> quartz grains with multiple sets of PDFs also occur at this site</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19940023299','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19940023299"><span id="translatedtitle">Flowfield dynamics in blunt fin-induced <span class="hlt">shock</span> wave/turbulent boundary <span class="hlt">layer</span> interactions</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Dolling, David S.; Brusniak, Leon</p> <p>1994-01-01</p> <p>Fluctuating wall pressure measurements have been made on centerline upstream of a blunt fin in a Mach 5 turbulent boundary <span class="hlt">layer</span>. By examining the ensemble averaged wall pressure distributions for different separation <span class="hlt">shock</span> foot positions, it has been shown that local fluctuating wall pressure measurements are due to a distinct pressure distribution, Rho(sub i), which undergoes a stretching and flattening effect as its upstream boundary translates aperiodically between the upstream influence and separation lines. The locations of the maxima and minima in the wall pressure standard deviation can be accurately predicted using this distribution, providing quantitative confirmation of the model. This model also explains the observed cross-correlations and ensemble average measurements within the interaction. Using the Rho(sub i) model, wall pressure signals from under the separated flow region were used to reproduce the position-time history of the separation <span class="hlt">shock</span> foot. Further, the negative time delay peak in the cross-correlation between the predicted and actual <span class="hlt">shock</span> foot histories suggests that the separated region fluctuations precede <span class="hlt">shock</span> foot motion. The unsteady behavior of the primary horseshoe vortex and its relation to the unsteady separation <span class="hlt">shock</span> are described.</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_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li class="active"><span>8</span></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_13");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_8 --> <div id="page_9" 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_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li class="active"><span>9</span></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_13");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="161"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015APS..DFDL21010S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015APS..DFDL21010S"><span id="translatedtitle">Investigation of <span class="hlt">Shock</span>-Induced Laminar Separation Bubble in a Supersonic Boundary <span class="hlt">Layer</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sivasubramanian, Jayahar; Fasel, Hermann</p> <p>2015-11-01</p> <p>The interaction between an impinging oblique <span class="hlt">shock</span> and a laminar boundary-<span class="hlt">layer</span> on a flat plate is investigated using DNS. In particular, the two-dimensional separation bubble resulting from the <span class="hlt">shock/boundary-layer</span> interaction (SBLI) at freestream Mach number of 2.0 is investigated in detail. The flow parameters used for the present investigation match the laboratory conditions in the experiments by Hakkinen et al. The skin friction and pressure distribution from the simulations are compared to the experimental measurements and numerical results available in the literature. Our results confirm the asymmetric nature of the separation bubble as reported in the literature. In addition to the steady flow field calculations, the response to low-amplitude disturbances is investigated in order to study the linear stability behavior of the separation bubble. For comparison, both the development of two-dimensional and three-dimensional (oblique) disturbances are studied with and without the impinging oblique <span class="hlt">shock</span>. Furthermore, the effects of the <span class="hlt">shock</span> incidence angle and Reynolds number are also investigated. Finally, three-dimensional simulations were performed in order to explore the laminar-turbulent transition process in the presence of a laminar separation bubble. Funded by the Air Force Office of Scientific Research under grant FA9550-14-1-0195.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19940010724&hterms=archetypes&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Darchetypes','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19940010724&hterms=archetypes&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Darchetypes"><span id="translatedtitle">Swept <span class="hlt">shock/boundary-layer</span> interactions: Scaling laws, flowfield structure, and experimental methods</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Settles, Gary S.</p> <p>1993-01-01</p> <p>A general review is given of several decades of research on the scaling laws and flowfield structures of swept <span class="hlt">shock</span> wave/turbulent boundary <span class="hlt">layer</span> interactions. Attention is further restricted to the experimental study and physical understanding of the steady-state aspects of these flows. The interaction produced by a sharp, upright fin mounted on a flat plate is taken as an archetype. An overall framework of quasiconical symmetry describing such interactions is first developed. Boundary-<span class="hlt">layer</span> separation, the interaction footprint, Mach number scaling, and Reynolds number scaling are then considered, followed by a discussion of the quasiconical similarity of interactions produced by geometrically-dissimilar <span class="hlt">shock</span> generators. The detailed structure of these interaction flowfields is next reviewed, and is illustrated by both qualitative visualizations and quantitative flow images in the quasiconical framework. Finally, the experimental techniques used to investigate such flows are reviewed, with emphasis on modern non-intrusive optical flow diagnostics.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19800012047','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19800012047"><span id="translatedtitle">Calculation of oblique-<span class="hlt">shock</span>-wave laminar-boundary-<span class="hlt">layer</span> interaction on a flat plate</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Goldberg, U.; Reshotko, E.</p> <p>1980-01-01</p> <p>A finite difference solution to the problem of the interaction between an impinging oblique <span class="hlt">shock</span> wave and the laminar boundary <span class="hlt">layer</span> on a flat plate is presented. The boundary <span class="hlt">layer</span> equations coupled with the Prandtl-Meyer relation for the external flow are used to calculate the flow field. A method for the calculation of the separated flow region is presented and discussed. Comparisons between this theory and the experimental results of other investigators show fairly good agreement. Results are presented for the case of a cooled wall with an oncoming flow at Mach number 2.0 without and with suction. The results show that a small amount of suction greatly reduces the extent of the separated region in the vicinity of the <span class="hlt">shock</span> impingement location.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19750050138&hterms=tecnica&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dtecnica','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19750050138&hterms=tecnica&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dtecnica"><span id="translatedtitle">Interaction between a <span class="hlt">shock</span> wave and a turbulent boundary <span class="hlt">layer</span> 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.; Feo, A.</p> <p>1975-01-01</p> <p>Interaction between a <span class="hlt">shock</span> wave and an unseparated turbulent boundary <span class="hlt">layer</span> is considered. The method of matched asymptotic expansions is used, with solutions valid in the double limit as Reynolds number tends to infinity and Mach number tends to unity. The <span class="hlt">shock</span> is weak enough that interaction effects can be considered as perturbations to the undisturbed flow; the case considered is that where the sonic line is near the outer edge of the boundary <span class="hlt">layer</span>. It is shown that, with order estimates for Reynolds stress perturbations, the induced wall pressure distribution can be calculated using only the two outer interaction regions, independent of a specific closure condition and that this solution is in fact a turbulent free interaction solution. A detailed analysis of the inner regions, for which an eddy viscosity model for the Reynolds shear stress is used, provides a description of the variations in velocity, temperature and density near and at the wall.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19950056083&hterms=knowledge+transfer&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dknowledge%2Btransfer','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19950056083&hterms=knowledge+transfer&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dknowledge%2Btransfer"><span id="translatedtitle">Heat-transfer measurements and computations of swept-<span class="hlt">shock</span>-wave boundary-<span class="hlt">layer</span> interactions</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Lee, Y.; Settles, G. S.; Horstman, C. C.</p> <p>1994-01-01</p> <p>An experimental and computational research program providing new knowledge of the heat transfer in swept-<span class="hlt">shock-wave/boundary-layer</span> interactions is described. An equilibrium turbulent boundary <span class="hlt">layer</span> on a flat plate is subjected to impingement by a swept planar <span class="hlt">shock</span> wave generated by a sharp fin. Five different interactions with fin angles ranging from 10 to 20 deg at freestream Mach numbers of 3 and 4 produce a variety of interaction strengths ranging from weak to very strong. A foil heater generates a uniform heat flux over the flat plate surface, and miniature thin-film-resistance sensors are used to measure the local surface temperature. The heat convection equation is then solved for the heat transfer distribution within an interaction, yielding an uncertainty of about +/- 10%. These data are compared with numerical Navier-Stokes solutions that employ a k-epsilon turbulence model. A simple peak heat transfer correlation for fin interactions is suggested.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/21241943','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/21241943"><span id="translatedtitle">A point radiator <span class="hlt">parallel</span> to a plane <span class="hlt">layer</span> with negative refractive index</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Petrin, A. B.</p> <p>2008-09-15</p> <p>Focusing of an electromagnetic wave radiated by a point source and transmitted through a plane <span class="hlt">layer</span> filled with a medium with negative refractive index is considered. An elementary electric Hertzian dipole located in the air (or vacuum) <span class="hlt">parallel</span> to the boundaries of the <span class="hlt">layer</span> is considered as a point source of radiation. It is rigorously shown that, after transmitting through a <span class="hlt">layer</span> with negative refractive index, the electromagnetic wave of the dipole is focused into a certain domain. The dimensions of the focusing region are investigated. The results of the investigation show that the use of homogeneous materials with negative refraction does not allow one to overcome the diffraction limit.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20150021042','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20150021042"><span id="translatedtitle">CFD Validation Experiment of a Mach 2.5 Axisymmetric <span class="hlt">Shock-Wave/Boundary-Layer</span> Interaction</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Davis, David Owen</p> <p>2015-01-01</p> <p>Preliminary results of an experimental investigation of a Mach 2.5 two-dimensional axisymmetric <span class="hlt">shock</span>-wave/ boundary-<span class="hlt">layer</span> interaction (SWBLI) are presented. The purpose of the investigation is to create a SWBLI dataset specifically for CFD validation purposes. Presented herein are the details of the facility and preliminary measurements characterizing the facility and interaction region. These results will serve to define the region of interest where more detailed mean and turbulence measurements will be made.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19900010219','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19900010219"><span id="translatedtitle">Swept <span class="hlt">shock</span>/boundary <span class="hlt">layer</span> interaction experiments in support of CFD code validation</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Settles, G. S.; Lee, Y.</p> <p>1990-01-01</p> <p>Research on the topic of <span class="hlt">shock</span> wave/turbulent boundary <span class="hlt">layer</span> interaction was carried out. Skin friction and surface pressure measurements in fin-induced, swept interactions were conducted, and heat transfer measurements in the same flows are planned. The skin friction data for a strong interaction case (Mach 4, fin-angles equal 16 and 20 degrees) were obtained, and their comparison with computational results was published. Surface pressure data for weak-to-strong fin interactions were also obtained.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19750020301','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19750020301"><span id="translatedtitle">Viscous-<span class="hlt">shock-layer</span> solutions for turbulent flow of radiating gas mixtures in chemical equilibrium</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Anderson, E. C.; Moss, J. N.</p> <p>1975-01-01</p> <p>The viscous-<span class="hlt">shock-layer</span> equations for hypersonic laminar and turbulent flows of radiating or nonradiating gas mixtures in chemical equilibrium are presented for two-dimensional and axially-symmetric flow fields. Solutions were obtained using an implicit finite-difference scheme and results are presented for hypersonic flow over spherically-blunted cone configurations at freestream conditions representative of entry into the atmosphere of Venus. These data are compared with solutions obtained using other methods of analysis.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19760003327','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19760003327"><span id="translatedtitle">Viscous <span class="hlt">shock</span> <span class="hlt">layer</span> solutions for turbulent flow of radiating gas mixtures in chemical equilibrium</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Anderson, E. C.; Moss, J. N.</p> <p>1975-01-01</p> <p>The viscous <span class="hlt">shock</span> <span class="hlt">layer</span> equations for hypersonic laminar and turbulent flows of radiating or nonradiating gas mixtures in chemical equilibrium are presented for two-dimensional and axially symmetric flow fields. Solutions are obtained using an implicit finite difference scheme and results are presented for hypersonic flow over spherically blunted cone configurations at free stream conditions representative of entry into the atmosphere of Venus. These data are compared with solutions obtained using other methods of analysis.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19950047148&hterms=steady+state&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dsteady%2Bstate','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19950047148&hterms=steady+state&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dsteady%2Bstate"><span id="translatedtitle">Investigation of intrinsic variability in one-dimensional <span class="hlt">parallel</span> <span class="hlt">shocks</span> using steady state hybrid simulations</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Bennett, Lee; Ellison, Donald C.</p> <p>1995-01-01</p> <p>We have developed a means of producing a steady state hybrid simulation of a collisionless <span class="hlt">shock</span>. The <span class="hlt">shock</span> is stopped in the simulation box by transforming into the <span class="hlt">shock</span> frame and by modifying the downstream boundary conditions to allow the plasma to flow through the simulation box. Once the <span class="hlt">shock</span> is stationary in the box frame, the simulation can be run for an arbitrary time with a fixed box size and a fixed number of simulation particles. Using this technique, we have shown that certain gross properties associated with the <span class="hlt">shock</span>, such as the particle distribution function (including energetic particles produced by Fermi acceleration) and the flow speed profile, are constant (except for statistical variations) over hundreds of gyroperiods when averaged over times short compared to the average residence time of energetic particles. Our results imply that any microphysical processes responsible for particle heating and/or injection into the Fermi mechanism can be viewed as smooth and continuous on timescales longer than a few gyroperiods.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19920023250','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19920023250"><span id="translatedtitle">Swept <span class="hlt">shock</span>/boundary <span class="hlt">layer</span> interaction experiments in support of CFD code validation</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Settles, G. S.; Lee, Y.</p> <p>1992-01-01</p> <p>Research on the topic of <span class="hlt">shock</span> wave/turbulent boundary-<span class="hlt">layer</span> interaction was carried out during the past three years at the Penn State Gas Dynamics Laboratory. This report describes the experimental research program which provides basic knowledge and establishes new data on heat transfer in swept <span class="hlt">shock</span> wave/boundary-<span class="hlt">layer</span> interactions. An equilibrium turbulent boundary-<span class="hlt">layer</span> on a flat plate is subjected to impingement by swept planar <span class="hlt">shock</span> waves generated by a sharp fin. Five different interactions with fin angle ranging from 10 deg to 20 deg at freestream Mach numbers of 3.0 and 4.0 produce a variety of interaction strengths from weak to very strong. A foil heater generates a uniform heat flux over the flat plate surface, and miniature thin-film-resistance sensors mounted on it are used to measure the local surface temperature. The heat convection equation is then solved for the heat transfer distribution within an interaction, yielding a total uncertainty of about +/- 10 percent. These experimental data are compared with the results of numerical Navier-Stokes solutions which employ a k-epsilon turbulence model. Finally, a simplified form of the peak heat transfer correlation for fin interactions is suggested.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016IJMPS..4260186Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016IJMPS..4260186Y"><span id="translatedtitle">Large-Eddy Simulation of <span class="hlt">Shock</span>-Wave Boundary <span class="hlt">Layer</span> Interaction and its Control Using Sparkjet</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yang, Guang; Yao, Yufeng; Fang, Jian; Gan, Tian; Lu, Lipeng</p> <p>2016-06-01</p> <p>Large-eddy simulation (LES) of an oblique <span class="hlt">shock</span>-wave generated by an 8° sharp wedge impinging onto a spatially-developing Mach 2.3 turbulent boundary <span class="hlt">layer</span> and their interactions has been carried out in this study. The Reynolds number based on the incoming flow property and the boundary <span class="hlt">layer</span> displacement thickness at the impinging point without <span class="hlt">shock</span>-wave is 20,000. The detailed numerical approaches are described and the inflow turbulence is generated using the digital filter method to avoid artificial temporal or streamwise periodicity. Numerical results are compared with the available wind tunnel PIV measurements of the same flow conditions. Further LES study on the control of flow separation due to the strong <span class="hlt">shock</span>-viscous interaction is also conducted by using an active control actuator “SparkJet” concept. The single-pulsed characteristics of the control device are obtained and compared with the experiments. Instantaneous flowfield shows that the “SparkJet” promotes the flow mixing in the boundary <span class="hlt">layer</span> and enhances its ability to resist the flow separation. The time and spanwise averaged skin friction coefficient distribution demonstrates that the separation bubble length is reduced by maximum 35% with the control exerted.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012EUCAS...3..141S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012EUCAS...3..141S"><span id="translatedtitle">Effect on a <span class="hlt">shock</span> wave boundary <span class="hlt">layer</span> interaction of air jet vortex generators</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Souverein, L. J.; Debiève, J.-F.</p> <p>2012-01-01</p> <p>The effect of upstream injection by means of continuous Air Jet Vortex Generators (AJVGs) on a <span class="hlt">shock</span> wave turbulent boundary <span class="hlt">layer</span> interaction is experimentally investigated. The baseline interaction is of the impinging type, with a flow deflection angle of 9.5° , a Mach number Me = 2.3, and a momentum thickness based Reynolds number of 5,000. Considered are the effects of the AJVGs on the upstream boundary <span class="hlt">layer</span> flow topology and on the spatial and dynamical characteristics of the interaction. To this aim, Stereoscopic Particle Image Velocimetry has been employed, in addition to hot-wire anemometry (HWA) for the investigation of the dynamical characteristics of the reflected <span class="hlt">shock</span>. It is shown that the AJVGs significantly modify the three-dimensionality of the upstream boundary <span class="hlt">layer</span>. Overall, the AJVGs cause a reduction of the separation bubble length and height. In addition, the energetic frequency range of the reflected <span class="hlt">shock</span> is increased by approximately 50%, which is in qualitative agreement with the smaller separation bubble size.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19930046822&hterms=earths+magnetic+field&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dearths%2Bmagnetic%2Bfield','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19930046822&hterms=earths+magnetic+field&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dearths%2Bmagnetic%2Bfield"><span id="translatedtitle">Nonthermal ions and associated magnetic field behavior at a quasi-<span class="hlt">parallel</span> 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>Wilkinson, W. P.; Pardaens, A. K.; Schwartz, S. J.; Burgess, D.; Luehr, H.; Kessel, R. L.; Dunlop, M.; Farrugia, C. J.</p> <p>1993-01-01</p> <p>Attention is given to ion and magnetic field measurements at the earth's bow <span class="hlt">shock</span> from the AMPTE-UKS and -IRM spacecraft, which were examined in high time resolution during a 45-min interval when the field remained closely aligned with the model bow <span class="hlt">shock</span> normal. Dense ion beams were detected almost exclusively in the midst of short-duration periods of turbulent magnetic field wave activity. Many examples of propagation at large elevation angles relative to the ecliptic plane, which is inconsistent with reflection in the standard model <span class="hlt">shock</span> configuration, were discovered. The associated waves are elliptically polarized and are preferentially left-handed in the observer's frame of reference, but are less confined to the maximum variance plane than other previously studied foreshock waves. The association of the wave activity with the ion beams suggests that the former may be triggered by an ion-driven instability, and possible candidates are discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19890010729','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19890010729"><span id="translatedtitle">Documentation of Two- and Three-Dimensional Hypersonic <span class="hlt">Shock</span> Wave/Turbulent Boundary <span class="hlt">Layer</span> Interaction Flows</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Kussoy, Marvin I.; Horstman, Clifford C.</p> <p>1989-01-01</p> <p>Experimental data for a series of two- and three-dimensional <span class="hlt">shock</span> wave/turbulent boundary <span class="hlt">layer</span> interaction flows at Mach 7 are presented. Test bodies, composed of simple geometric shapes, were designed to generate flows with varying degrees of pressure gradient, boundary-<span class="hlt">layer</span> separation, and turning angle. The data include surface-pressure and heat-transfer distributions as well as limited mean-flow-field surveys in both the undisturbed and the interaction regimes. The data are presented in a convenient form for use in validating existing or future computational models of these generic hypersonic flows.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1991thph.confQ....G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1991thph.confQ....G"><span id="translatedtitle">A viscous-<span class="hlt">shock-layer</span> analysis of the Martian aerothermal environment</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gupta, R. N.; Moss, J. N.; Sutton, K.; Lee, K. P.</p> <p>1991-06-01</p> <p>Surface heating and flow field results for the stagnation region of a planetary exploration vehicle entering the Martian atmosphere are presented. Solutions for the high-energy viscous flow fields with complete radiative heating are derived from a viscous-<span class="hlt">shock-layer</span> analysis for laminar flow under chemical equilibrium conditions. Results are shown with and without coupled radiation ablation injection utilizing the recently developed curve fits for the transport and thermodynamic properties of Martian atmospheric and ablation species. This analysis includes a strongly absorbing boundary <span class="hlt">layer</span> and, therefore, gives much lower radiative heat transfer rates than those obtained from inviscid analyses.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/24476280','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/24476280"><span id="translatedtitle">Megavolt <span class="hlt">parallel</span> potentials arising from double-<span class="hlt">layer</span> streams in the Earth's outer radiation belt.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Mozer, F S; Bale, S D; Bonnell, J W; Chaston, C C; Roth, I; Wygant, J</p> <p>2013-12-01</p> <p>Huge numbers of double <span class="hlt">layers</span> carrying electric fields <span class="hlt">parallel</span> to the local magnetic field line have been observed on the Van Allen probes in connection with in situ relativistic electron acceleration in the Earth's outer radiation belt. For one case with adequate high time resolution data, 7000 double <span class="hlt">layers</span> were observed in an interval of 1 min to produce a 230,000 V net <span class="hlt">parallel</span> potential drop crossing the spacecraft. Lower resolution data show that this event lasted for 6 min and that more than 1,000,000 volts of net <span class="hlt">parallel</span> potential crossed the spacecraft during this time. A double <span class="hlt">layer</span> traverses the length of a magnetic field line in about 15 s and the orbital motion of the spacecraft perpendicular to the magnetic field was about 700 km during this 6 min interval. Thus, the instantaneous <span class="hlt">parallel</span> potential along a single magnetic field line was the order of tens of kilovolts. Electrons on the field line might experience many such potential steps in their lifetimes to accelerate them to energies where they serve as the seed population for relativistic acceleration by coherent, large amplitude whistler mode waves. Because the double-<span class="hlt">layer</span> speed of 3100  km/s is the order of the electron acoustic speed (and not the ion acoustic speed) of a 25 eV plasma, the double <span class="hlt">layers</span> may result from a new electron acoustic mode. Acceleration mechanisms involving double <span class="hlt">layers</span> may also be important in planetary radiation belts such as Jupiter, Saturn, Uranus, and Neptune, in the solar corona during flares, and in astrophysical objects. PMID:24476280</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013PhRvL.111w5002M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013PhRvL.111w5002M"><span id="translatedtitle">Megavolt <span class="hlt">Parallel</span> Potentials Arising from Double-<span class="hlt">Layer</span> Streams in the Earth's Outer Radiation Belt</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mozer, F. S.; Bale, S. D.; Bonnell, J. W.; Chaston, C. C.; Roth, I.; Wygant, J.</p> <p>2013-12-01</p> <p>Huge numbers of double <span class="hlt">layers</span> carrying electric fields <span class="hlt">parallel</span> to the local magnetic field line have been observed on the Van Allen probes in connection with in situ relativistic electron acceleration in the Earth’s outer radiation belt. For one case with adequate high time resolution data, 7000 double <span class="hlt">layers</span> were observed in an interval of 1 min to produce a 230 000 V net <span class="hlt">parallel</span> potential drop crossing the spacecraft. Lower resolution data show that this event lasted for 6 min and that more than 1 000 000 volts of net <span class="hlt">parallel</span> potential crossed the spacecraft during this time. A double <span class="hlt">layer</span> traverses the length of a magnetic field line in about 15 s and the orbital motion of the spacecraft perpendicular to the magnetic field was about 700 km during this 6 min interval. Thus, the instantaneous <span class="hlt">parallel</span> potential along a single magnetic field line was the order of tens of kilovolts. Electrons on the field line might experience many such potential steps in their lifetimes to accelerate them to energies where they serve as the seed population for relativistic acceleration by coherent, large amplitude whistler mode waves. Because the double-<span class="hlt">layer</span> speed of 3100km/s is the order of the electron acoustic speed (and not the ion acoustic speed) of a 25 eV plasma, the double <span class="hlt">layers</span> may result from a new electron acoustic mode. Acceleration mechanisms involving double <span class="hlt">layers</span> may also be important in planetary radiation belts such as Jupiter, Saturn, Uranus, and Neptune, in the solar corona during flares, and in astrophysical objects.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016ShWav.tmp...67I&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016ShWav.tmp...67I&link_type=ABSTRACT"><span id="translatedtitle">Effects of boundary <span class="hlt">layer</span> on flame propagation generated by forced ignition behind an incident <span class="hlt">shock</span> wave</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ishihara, S.; Tamura, S.; Ishii, K.; Kataoka, H.</p> <p>2016-07-01</p> <p>To study the effects of the boundary <span class="hlt">layer</span> on the deflagration to detonation transition (DDT) process, the mixture behind an incident <span class="hlt">shock</span> wave was ignited using laser breakdown. Ignition timing was controlled so that the interaction of the resulting flame with a laminar or turbulent boundary <span class="hlt">layer</span> could be examined. In the case of the interaction with a laminar boundary <span class="hlt">layer</span>, wrinkling of the flame was observed after the flame reached the corner of the channel. On the other hand, interaction with the turbulent boundary <span class="hlt">layer</span> distorted the flame front and increased the spreading rate of the flame followed by prompt DDT. The inner structure of the turbulent boundary <span class="hlt">layer</span> plays an important role in the DDT process. The region that distorted the flame within the turbulent boundary <span class="hlt">layer</span> was found to be the intermediate region 0.01< y/δ < 0.4 , where y is the distance from the wall and δ is the boundary <span class="hlt">layer</span> thickness. The flame disturbance by the turbulent motions is followed by the flame interaction with the inner <span class="hlt">layer</span> near the wall, which in turn generates a secondary-ignition kernel that produced a spherical accelerating flame, which ultimately led to the onset of detonation. After the flame reached the intermediate region, the time required for DDT was independent of the ignition position. The effect of the boundary <span class="hlt">layer</span> on the propagating flame, thus, became relatively small after the accelerating flame was generated.</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_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li class="active"><span>9</span></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_13");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_9 --> <div id="page_10" 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_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li class="active"><span>10</span></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="181"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19930015972','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19930015972"><span id="translatedtitle">Alfven wave transport effects in the time evolution of <span class="hlt">parallel</span> cosmic-ray modified <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>Jones, T. W.</p> <p>1993-01-01</p> <p>Some of the issues associated with a more complete treatment of Alfven transport in cosmic ray <span class="hlt">shocks</span> are explored qualitatively. The treatment is simplified in some important respects, but some new issues are examined and for the first time a nonlinear, time dependent study of plane cosmic ray mediated <span class="hlt">shocks</span> with both the entropy producing effects of wave dissipation and effects due to the Alfven wave advection of the cosmic ray relative to the gas is included. Examination of the direct consequences of including the pressure and energy of the Alfven waves in the formalism began.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/1015686','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/1015686"><span id="translatedtitle"><span class="hlt">Parallel</span> adaptive Cartesian upwind methods for <span class="hlt">shock</span>-driven multiphysics simulation</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Deiterding, Ralf</p> <p>2011-01-01</p> <p>The multiphysics fluid-structure interaction simulation of <span class="hlt">shock</span>-loaded thin-walled structures requires the dynamic coupling of a <span class="hlt">shock</span>-capturing flow solver to a solid mechanics solver for large deformations. By combining a Cartesian embedded boundary approach with dynamic mesh adaptation a generic software framework for such flow solvers has been constructed that allows easy exchange of the specific hydrodynamic finite volume upwind scheme and coupling to various explicit finite element solid dynamics solvers. The paper gives an overview of the computational approach and presents first simulations that couple the software to the general purpose solid dynamics code DYNA3D.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19760012293','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19760012293"><span id="translatedtitle">Flowfield analysis for successive oblique <span class="hlt">shock</span> wave-turbulent boundary <span class="hlt">layer</span> interactions</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Sun, C. C.; Childs, M. E.</p> <p>1976-01-01</p> <p>A computation procedure is described for predicting the flowfields which develop when successive interactions between oblique <span class="hlt">shock</span> waves and a turbulent boundary <span class="hlt">layer</span> occur. Such interactions may occur, for example, in engine inlets for supersonic aircraft. Computations are carried out for axisymmetric internal flows at M 3.82 and 2.82. The effect of boundary <span class="hlt">layer</span> bleed is considered for the M 2.82 flow. A control volume analysis is used to predict changes in the flow field across the interactions. Two bleed flow models have been considered. A turbulent boundary <span class="hlt">layer</span> program is used to compute changes in the boundary <span class="hlt">layer</span> between the interactions. The results given are for flows with two <span class="hlt">shock</span> wave interactions and for bleed at the second interaction site. In principle the method described may be extended to account for additional interactions. The predicted results are compared with measured results and are shown to be in good agreement when the bleed flow rate is low (on the order of 3% of the boundary <span class="hlt">layer</span> mass flow), or when there is no bleed. As the bleed flow rate is increased, differences between the predicted and measured results become larger. Shortcomings of the bleed flow models at higher bleed flow rates are discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2013PhDT.......247W&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2013PhDT.......247W&link_type=ABSTRACT"><span id="translatedtitle">Control of a <span class="hlt">shock</span> wave-boundary <span class="hlt">layer</span> interaction using localized arc filament plasma actuators</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Webb, Nathan Joseph</p> <p></p> <p>Supersonic flight is currently possible, but expensive. Inexpensive supersonic travel will require increased efficiency of high-speed air entrainment, an integral part of air-breathing propulsion systems. Although mixed compression inlet geometry can significantly improve entrainment efficiency, numerous <span class="hlt">Shock</span> Wave-Boundary <span class="hlt">Layer</span> Interactions (SWBLIs) are generated in this configuration. The boundary <span class="hlt">layer</span> must therefore develop through multiple regions of adverse pressure gradient, causing it to thicken, and, in severe cases, separate. The associated increase in unsteadiness can have adverse effects on downstream engine hardware. The most severe consequence of these interactions is the increased aerodynamic blockage generated by the thickened boundary <span class="hlt">layer</span>. If the increase is sufficient, it can choke the flow, causing inlet unstart, and resulting in a loss of thrust and high transient forces on the engine, airframe, and aircraft occupants. The potentially severe consequences associated with SWBLIs require flow control to ensure proper operation. Traditionally, boundary <span class="hlt">layer</span> bleed has been used to control the interaction. Although this method is effective, it has inherent efficiency penalties. Localized Arc Filament Plasma Actuators (LAFPAs) are designed to generate perturbations for flow control. Natural flow instabilities act to amplify certain perturbations, allowing the LAFPAs to control the flow with minimal power input. LAFPAs also have the flexibility to maintain control over a variety of operating conditions. This work seeks to examine the effectiveness of LAFPAs as a separation control method for an oblique, impinging SWBLI. The low frequency unsteadiness in the reflected <span class="hlt">shock</span> was thought to be the natural manifestation of a Kelvin-Helmholtz instability in the shear <span class="hlt">layer</span> above the separation region. The LAFPAs were therefore placed upstream of the interaction to allow their perturbations to convect to the receptivity region (near the shear <span class="hlt">layer</span> origin</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19950058842&hterms=Computers+Dependent&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3DComputers%2BDependent','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19950058842&hterms=Computers+Dependent&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3DComputers%2BDependent"><span id="translatedtitle">Implementation of a 3D mixing <span class="hlt">layer</span> code on <span class="hlt">parallel</span> computers</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Roe, K.; Thakur, R.; Dang, T.; Bogucz, E.</p> <p>1995-01-01</p> <p>This paper summarizes our progress and experience in the development of a Computational-Fluid-Dynamics code on <span class="hlt">parallel</span> computers to simulate three-dimensional spatially-developing mixing <span class="hlt">layers</span>. In this initial study, the three-dimensional time-dependent Euler equations are solved using a finite-volume explicit time-marching algorithm. The code was first programmed in Fortran 77 for sequential computers. The code was then converted for use on <span class="hlt">parallel</span> computers using the conventional message-passing technique, while we have not been able to compile the code with the present version of HPF compilers.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010PhRvB..82s5327Y&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010PhRvB..82s5327Y&link_type=ABSTRACT"><span id="translatedtitle">Energy spectrum of <span class="hlt">layered</span> semiconductors in a magnetic field <span class="hlt">parallel</span> to the <span class="hlt">layers</span>: Voigt geometry</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yoo, K. H.; Ram-Mohan, L. R.</p> <p>2010-11-01</p> <p>The electronic band structure of zinc-blende <span class="hlt">layered</span> semiconductor heterostructures is investigated theoretically in the presence of an in-plane magnetic field, a configuration we label as the Voigt geometry. We use a Lagrangian formulation for modeling the band structure in the individual <span class="hlt">layers</span> within the kṡP model. This approach has been shown by us to provide the correct ordering of the derivatives appearing in the multiband description of Schrödinger’s equations for the envelope functions through the application of the principle of stationary action. Finite element modeling of the action integral provides a natural and efficient approach to the inclusion of in-plane magnetic fields in the energy-level analysis. Calculations for quantum wells and superlattices are presented, and the complex energy-level structure obtained for the <span class="hlt">layered</span> structures.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012ShWav..22..327V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012ShWav..22..327V"><span id="translatedtitle">Control of <span class="hlt">shock</span> unsteadiness in <span class="hlt">shock</span> boundary-<span class="hlt">layer</span> interaction on a compression corner using mechanical vortex generators</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Verma, S. B.; Manisankar, C.; Raju, C.</p> <p>2012-07-01</p> <p>An experimental study was conducted to control the unsteadiness of separation <span class="hlt">shock</span> in a Mach 2 24° compression ramp-induced interaction using mechanical vortex generators (VG). Control devices in the form of an array of single-row delta-ramps were placed upstream of the interaction region and tested for two streamwise locations with respect to the boundary <span class="hlt">layer</span> thickness ( δ) at the interaction location and height ` h' of the delta-ramps, i.e., at 27.5 δ or h/ δ = 0.65 and at 12.5 δ or h/ δ = 0.26, respectively. Surface oil study revealed traces of streamwise counter-rotating vortex pairs generated downstream of these devices. Measurements using pressure-sensitive paint also showed a spanwise sinusoidal pattern of wall pressure variation indicating generation of streamwise vortices from these control devices. These vortices, on interaction with the reverse flow in the separation bubble, replaced a well-defined separation line (for no control) by a highly corrugated separation line. In the region of separation, the mean pressure distribution gets modified while the peak rms value in the intermittent region of separation showed significant changes. Additionally, the spanwise spacing ` s' of the vertex of the delta ramps seemed to be an important parameter in controlling the peak rms value. A decrease in this spacing, i.e., VG1 with s = 0, significantly reduced the peak rms value (by 50 and 35 %) while an increase in the spacing, i.e., VG2 with s = 1 mm, consistently showed an increase (by 12 and 30 %) in the separation <span class="hlt">shock</span> unsteadiness relative to no control, irrespective of their placement location (of h/ δ = 0.65 and 0.26, respectively).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2013PhDT.......338H&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2013PhDT.......338H&link_type=ABSTRACT"><span id="translatedtitle">The effects of micro-vortex generators on normal <span class="hlt">shock</span> wave/boundary <span class="hlt">layer</span> interactions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Herges, Thomas G.</p> <p></p> <p><span class="hlt">Shock</span> wave/boundary-<span class="hlt">layer</span> interactions (SWBLIs) are complex flow phenomena that are important in the design and performance of internal supersonic and transonic flow fields such as engine inlets. This investigation was undertaken to study the effects of passive flow control devices on normal <span class="hlt">shock</span> wave/boundary <span class="hlt">layer</span> interactions in an effort to gain insight into the physics that govern these complex interactions. The work concentrates on analyzing the effects of vortex generators (VGs) as a flow control method by contributing a greater understanding of the flowfield generated by these devices and characterizing their effects on the SWBLI. The vortex generators are utilized with the goal of improving boundary <span class="hlt">layer</span> health (i.e., reducing/increasing the boundary-<span class="hlt">layer</span> incompressible shape factor/skin friction coefficient) through a SWBLI, increasing pressure recovery, and reducing flow distortion at the aerodynamic interface plane while adding minimal drag to the system. The investigation encompasses experiments in both small-scale and large-scale inlet testing, allowing multiple test beds for improving the characterization and understanding of vortex generators. Small-scale facility experiments implemented instantaneous schlieren photography, surface oil-flow visualization, pressure-sensitive paint, and particle image velocimetry to characterize the effects of an array of microramps on a normal <span class="hlt">shock</span> wave/boundary-<span class="hlt">layer</span> interaction. These diagnostics measured the time-averaged and instantaneous flow organization in the vicinity of the microramps and SWBLI. The results reveal that a microramp produces a complex vortex structure in its wake with two primary counter-rotating vortices surrounded by a train of Kelvin- Helmholtz (K-H) vortices. A streamwise velocity deficit is observed in the region of the primary vortices in addition to an induced upwash/downwash which persists through the normal <span class="hlt">shock</span> with reduced strength. The microramp flow control also increased the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2012APS..DFDR25006G&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2012APS..DFDR25006G&link_type=ABSTRACT"><span id="translatedtitle">Control of <span class="hlt">Shock</span>-Induced Boundary <span class="hlt">Layer</span> Separation by using Pulsed Plasma Jets</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Greene, Benton R.; Clemens, Noel T.; Micka, Daniel</p> <p>2012-11-01</p> <p><span class="hlt">Shock</span>-induced turbulent boundary <span class="hlt">layer</span> separation can have many detrimental effects in supersonic flow including flow instability, fatigue of structural panels, and unstart in supersonic inlets. Pulsed plasma jets (or ``spark jets''), which are characterized by high bandwidth and the ability to direct momentum into the flow, are one promising method of reducing <span class="hlt">shock</span>-induced separation. The current study is focused on investigating the efficacy of plasma jets to reduce the separated flow induced by a compression ramp in a Mach 3 flow. Three different 3-jet actuator configurations are tested: 20° pitched, 45° pitched, and 22° pitched and 45° skewed. The jets are pulsed at frequencies between 2 kHz and 4 kHz with duty cycles between 5 and 15%. The <span class="hlt">shock</span> wave is generated using a 20° compression ramp, and the location of the <span class="hlt">shock</span>-induced separation is visualized using surface oil streak visualization as well as particle image velocimetry. The results of the study show that of the three configurations, the plasma jets pitched at 20° from the streamwise direction cause the greatest reduction in separation, and when pulsed at a frequency of 3.2 kHz and 12% duty cycle can reduce the size of the separation region by up to 40%. This work is supported by AFRL under SBIR contract.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013APS..DFDA30009R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013APS..DFDA30009R"><span id="translatedtitle">Simultaneous Concentration and Velocity Field Measurements in a <span class="hlt">Shock</span>-accelerated Mixing <span class="hlt">Layer</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Reese, Daniel; Oakley, Jason; Weber, Chris; Rothamer, David; Navarro, Jose; Bonazza, Riccardo</p> <p>2013-11-01</p> <p>The Richtmyer-Meshkov instability (RMI) is experimentally investigated at the Wisconsin <span class="hlt">Shock</span> Tube Laboratory. Simultaneous concentration and velocity field measurements from the mixing <span class="hlt">layer</span> of experimental RMI images are obtained through the application of the Advection-Corrected Correlation Image Velocimetry (ACCIV) technique. A statistically repeatable broadband initial condition is created by first setting up a gravitationally stable stagnation plane of helium +acetone over argon and then injecting the gases horizontally at the interface to create a shear <span class="hlt">layer</span>. The shear <span class="hlt">layer</span> is then accelerated by a Mach 2.2 planar <span class="hlt">shock</span> wave that causes the growth of any perturbations present at the interface, and time-separated image pair data of the mixing <span class="hlt">layer</span> are obtained using planar laser induced fluorescence (PLIF). The image pair is corrected to show relative acetone concentration, and is then used as input to the ACCIV algorithm to obtain velocity field results. These velocity field measurements are compared with those obtained from numerical simulations. Turbulent kinetic energy spectra are compared with particle imaging velocimetry (PIV) and simulation results to validate regions of applicability. We wish to thank the Department of Energy National Nuclear Security Administration for supporting this work.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19980201099','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19980201099"><span id="translatedtitle">Flowfield Measurements in a Slot-Bled Oblique <span class="hlt">Shock</span> Wave and Turbulent Boundary-<span class="hlt">Layer</span> Interaction</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Davis, D. O.; Willis, B. P.; Hingst, W. R.</p> <p>1998-01-01</p> <p>An experimental investigation was conducted to determine the flowfield inside a bleed slot used to control an oblique <span class="hlt">shock</span>-wave and turbulent boundary-<span class="hlt">layer</span> interaction. The slot was oriented normal to the primary flow direction and had a width of 1.0 cm (primary flow direction), a length of 2.54 cm, and spanned 16.5 cm. The approach boundary <span class="hlt">layer</span> upstream of the interaction was nominally 3.0 cm thick. Two operating conditions were studied: M = 1.98 with a <span class="hlt">shock</span> generator deflection angle of 6 deg and M= 2.46 with a <span class="hlt">shock</span> generator deflection angle of 8 deg. Measurements include surface and flowfield static pressure, Pitot pressure, and total mass-flow through the slot. The results show that despite an initially two-dimensional interaction for the zero bleed-flow case, the slot does not remove mass uniformly in the spanwise direction. Inside the slot, the flow is characterized by two separation regions which significantly reduce the effective flow area. The upper separation region acts as an aerodynamic throat resulting in supersonic flow through much of the slot.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19930064296&hterms=Wei+Li&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAuthor-Name%26N%3D0%26No%3D60%26Ntt%3DWei%2BLi','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19930064296&hterms=Wei+Li&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAuthor-Name%26N%3D0%26No%3D60%26Ntt%3DWei%2BLi"><span id="translatedtitle">Numerical simulation of a <span class="hlt">shock</span> wave/turbulent boundary <span class="hlt">layer</span> interaction in a duct</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Yang, Wei-Li; Greber, Isaac</p> <p>1993-01-01</p> <p>A numerical investigation of the interaction of an incident oblique <span class="hlt">shock</span> wave with a turbulent duct flow is presented. The investigation consists of solving the three-dimensional, unsteady, compressible, mass averaged Navier-Stokes equations, using an implicit finite volume, lower-upper time marching code and incorporates the three-dimensional Baldwin-Lomax turbulence model. Computed results are obtained Mach number 2.9 for a turning angle of 13 degrees and Reynolds number based on duct width of 1.36 x 10 exp 7. Under various inlet conditions, the results clearly depict the flow characteristics, including the <span class="hlt">shock</span> geometry, the separated flow region, the wall pressure distribution, and the skin friction distribution. The findings provide a physical understanding of the three-dimensional vortex structure of the flow in a duct in which a <span class="hlt">shock</span> wave interacts with a turbulent boundary <span class="hlt">layer</span>. The results show that the ratio of the boundary <span class="hlt">layer</span> thickness to the duct width is the critical parameter in determining the separation structure.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19950053670&hterms=left-handed&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dleft-handed','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19950053670&hterms=left-handed&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dleft-handed"><span id="translatedtitle">Observation of a slow-mode <span class="hlt">shock</span> in the dayside magnetopause reconnection <span class="hlt">layer</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Walthour, D. W.; Sonnerup, B. U. O.; Russell, C. T.</p> <p>1995-01-01</p> <p>Plasma and magnetic field data from the International Sun Earth Explorer (ISEE) 2 spacecraft recorded on 29 Oct 1979 provide evidence for a slow <span class="hlt">shock</span> (SS) in the reconnection <span class="hlt">layer</span> of the dayside magnetopause. This <span class="hlt">layer</span> is bounded on the magnetosheath side by the SS and on the magnetospheric side by a rotational discontinuity (RD). The direction of the accelerated plasma flow, the earthward sense of the normal magnetic field across both discontinuities, and the relative orientation of the SS and the RD all indicate that the reconnection site was located south of the spacecraft. Examination of the substantial pressure anisotropy downstream of the SS explains two unusual properties of the <span class="hlt">shock</span>: (1) the slow-mode and intermediate-mode phase speeds are inverted downstream of the SS such that the RD propagates behind the SS rather than ahead of it; (2) the magnetic wave polarization reserves such that the SS initially displays a left-handed polarization and then switches to a right-handed polarization inside the <span class="hlt">shock</span> structure.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007APS..DFD.GO007B&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007APS..DFD.GO007B&link_type=ABSTRACT"><span id="translatedtitle">Unsteady effects in normal <span class="hlt">shock</span> wave/turbulent boundary <span class="hlt">layer</span> interaction</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bernardini, Matteo; Pirozzoli, Sergio; Grasso, Francesco</p> <p>2007-11-01</p> <p>The interaction of a spatially developing supersonic turbulent boundary <span class="hlt">layer</span> with a normal <span class="hlt">shock</span> wave is analyzed by means of direct numerical simulation of the compressible Navier-Stokes equations. At the selected flow conditions, corresponding to a mild <span class="hlt">shock</span>, no mean flow separation is observed. However, the flow is strongly unsteady, and intermittent regions of flow reversal are found near the wall, while large vortical structures are observed away from it. Such structures are mainly responsible for the amplification of noise and turbulence across the interaction zone. In particular, the sound field attains very large values (up to 162 dB) near the nominal impingement point. The intense acoustic loads occurring in the interaction zone are found to be strictly related to the Reynolds shear stress distribution. The analysis of the pressure energy spectra shows a behavior consistent with that observed in incompressible boundary <span class="hlt">layers</span> in adverse pressure gradient. In particular, a power-law scaling is recovered: at low frequencies the spectra scale as St^0.4, while at high frequencies they decay as St-5. The results show that the interacting <span class="hlt">shock</span> primarily acts as a low-pass filter for the turbulence spectra. The main effect is to enhance the low-frequency components while inhibiting the higher ones. We acknowledge the CASPUR computing consortium (University of Rome `La Sapienza') for providing the computational resources to perform the numerical simulation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22011845','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22011845"><span id="translatedtitle">COULD COSMIC RAYS AFFECT INSTABILITIES IN THE TRANSITION <span class="hlt">LAYER</span> OF NONRELATIVISTIC COLLISIONLESS <span class="hlt">SHOCKS</span>?</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Stroman, Thomas; Pohl, Martin; Niemiec, Jacek; Bret, Antoine</p> <p>2012-02-10</p> <p>There is an observational correlation between astrophysical <span class="hlt">shocks</span> and nonthermal particle distributions extending to high energies. As a first step toward investigating the possible feedback of these particles on the <span class="hlt">shock</span> at the microscopic level, we perform particle-in-cell (PIC) simulations of a simplified environment consisting of uniform, interpenetrating plasmas, both with and without an additional population of cosmic rays. We vary the relative density of the counterstreaming plasmas, the strength of a homogeneous <span class="hlt">parallel</span> magnetic field, and the energy density in cosmic rays. We compare the early development of the unstable spectrum for selected configurations without cosmic rays to the growth rates predicted from linear theory, for assurance that the system is well represented by the PIC technique. Within the parameter space explored, we do not detect an unambiguous signature of any cosmic-ray-induced effects on the microscopic instabilities that govern the formation of a <span class="hlt">shock</span>. We demonstrate that an overly coarse distribution of energetic particles can artificially alter the statistical noise that produces the perturbative seeds of instabilities, and that such effects can be mitigated by increasing the density of computational particles.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016PPCF...58h5004C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016PPCF...58h5004C"><span id="translatedtitle">Effect of collisional temperature isotropisation on ELM <span class="hlt">parallel</span> transport in a tokamak scrape-off <span class="hlt">layer</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Coulette, David; Hirstoaga, Sever A.; Manfredi, Giovanni</p> <p>2016-08-01</p> <p>We develop a hybrid model to describe the <span class="hlt">parallel</span> transport in a tokamak scrape-off <span class="hlt">layer</span> following an edge-localized mode (ELM) event. The <span class="hlt">parallel</span> dynamics is treated with a kinetic Vlasov–Poisson model, while the evolution of the perpendicular temperature {{T}\\bot} is governed by a fluid equation. The coupling is ensured by isotropising collisions. The model generalises an earlier approach where {{T}\\bot} was constant in space and time (Manfredi et al 2011 Plasma Phys. Control. Fusion 53 015012). Numerical results show that the main effect comes from electron–electron collisions, which limit the decrease of the <span class="hlt">parallel</span> electron temperature and increase the potential drop in the Debye sheath in front of the surface. Ion–ion collisions have an almost negligible impact. The net effect is an increased peak power load on the target plates.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2835280','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2835280"><span id="translatedtitle"><span class="hlt">Parallel</span> combinatorial chemical synthesis using single-<span class="hlt">layer</span> poly(dimethylsiloxane) microfluidic devices</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Dexter, Joseph P.; Parker, William</p> <p>2009-01-01</p> <p>Improving methods for high-throughput combinatorial chemistry has emerged as a major area of research because of the importance of rapidly synthesizing large numbers of chemical compounds for drug discovery and other applications. In this investigation, a novel microfluidic chip for performing <span class="hlt">parallel</span> combinatorial chemical synthesis was developed. Unlike past microfluidic systems designed for <span class="hlt">parallel</span> combinatorial chemistry, the chip is a single-<span class="hlt">layer</span> device made of poly(dimethylsiloxane) that is extremely easy and inexpensive to fabricate. Using the chip, a 2×2 combinatorial series of amide-formation reactions was performed. The results of this combinatorial synthesis indicate that the new device is an effective platform for running <span class="hlt">parallel</span> organic syntheses at significantly higher throughput than with past methodologies. Additionally, a design algorithm for scaling up the 2×2 combinatorial synthesis chip to address more complex cases was developed. PMID:20216962</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19790011875','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19790011875"><span id="translatedtitle">A study of the interaction of a normal <span class="hlt">shock</span> wave with a turbulent boundary <span class="hlt">layer</span> at transonic speeds</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Messiter, A. F.; Adamson, T. C., Jr.</p> <p>1979-01-01</p> <p>An asymptotic description is derived for the interaction of a weak normal <span class="hlt">shock</span> wave and a turbulent boundary <span class="hlt">layer</span> along a plane wall. In the case studied the nondimensional friction velocity is small in comparison with the nondimensional <span class="hlt">shock</span> strength, and the <span class="hlt">shock</span> wave extends well into the boundary <span class="hlt">layer</span>. Analytical results are described for the local pressure distribution and wall shear, and a criterion for incipient separation is proposed. A comparison of predicted pressures with available experimental data includes the effect of longitudinal wall curvature.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19820054149&hterms=1082&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3D%2526%25231082','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19820054149&hterms=1082&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3D%2526%25231082"><span id="translatedtitle">Tangential blowing for control of strong normal <span class="hlt">shock</span> - Boundary <span class="hlt">layer</span> interactions on inlet ramps</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Schwendemann, M. F.; Sanders, B. W.</p> <p>1982-01-01</p> <p>The use of tangential blowing from a row of holes in an aft facing step is found to provide good control of the ramp boundary <span class="hlt">layer</span>, normal <span class="hlt">shock</span> interaction on a fixed geometry inlet over a wide range of inlet mass flow ratios. Ramp Mach numbers of 1.36 and 1.96 are investigated. The blowing geometry is found to have a significant effect on system performance at the highest Mach number. The use of high-temperature air in the blowing system, however, has only a slight effect on performance. The required blowing rates are significantly high for the most severe test conditions. In addition, the required blowing coefficient is found to be proportional to the normal <span class="hlt">shock</span> pressure rise.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016JKPS...68..520D&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016JKPS...68..520D&link_type=ABSTRACT"><span id="translatedtitle"><span class="hlt">Shock</span> waves and double <span class="hlt">layers</span> in a quantum electron-positron-ion plasma</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dip, P. R.; Hossen, M. A.; Salahuddin, M.; Mamun, A. A.</p> <p>2016-02-01</p> <p>The ion-acoustic (IA) <span class="hlt">shock</span> waves and double <span class="hlt">layers</span> (DLs) in an unmagnetized, dissipative, quantum electron-positron-ion (EPI) plasma (composed of a viscous heavy ion fluid, Fermi electrons and positrons) have been theoretically investigated. The higher-order Burgers and Gardner equations are derived by employing the reductive perturbation method. The basic features of the IA <span class="hlt">shock</span> waves and the DLs are identified by analyzing the solutions of both the higher-order Burgers and Gardner equations. The ratio of the Fermi temperature of the positron to that of the electron, the Fermi pressure of electrons and positrons, the viscous force, the plasma particle number densities, etc. are found to change remarkably the basic features (viz. amplitude, width, phase speed, etc.) of the IA waves. The results of our investigation may be helpful in understanding the nonlinear features of localized IA waves propagating in quantum EPI plasmas which are ubiquitous in astrophysical, as well as laboratory, environments.</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_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li class="active"><span>10</span></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_10 --> <div id="page_11" 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_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li class="active"><span>11</span></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_13");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="201"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19870035428&hterms=doppler+scaling&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Ddoppler%2Bscaling','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19870035428&hterms=doppler+scaling&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Ddoppler%2Bscaling"><span id="translatedtitle">Two-component LDV investigation of 3-dimensional <span class="hlt">shock</span>/turbulent boundary <span class="hlt">layer</span> interactions</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Brown, J. D.; Brown, J. L.; Kussoy, M. I.; Horstman, C. C.; Holt, M.</p> <p>1987-01-01</p> <p>Mean-velocity and turbulence measurements obtained by two-component laser Doppler velocimetry are presented, together with numerical predictions, for the <span class="hlt">shock</span>-related separation of a turbulent boundary <span class="hlt">layer</span> at Mach 2.85. The basic geometry, a 30 deg half-angle flare mounted on a long cylinder, is made three-dimensional by tipping the flare at an angle of attack, alpha. The separation length and general upstream influence increase with alpha. A recirculating vortex in the separated zone becomes stronger as three-dimensionality increases. A large-scale unsteadiness of the separation <span class="hlt">shock</span> wave and surrounding flowfields grows in amplitude with alpha, and appears to strongly influence the amplification of turbulence correlations ahead of detachment. Scaling of the streamwise coordinate by separation length causes two-dimensional and three-dimensional data profiles on the cylinder to collapse for most measured quantities.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19880018135','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19880018135"><span id="translatedtitle">A documentation of two- and three-dimensional <span class="hlt">shock</span>-separated turbulent boundary <span class="hlt">layers</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Brown, J. D.; Brown, J. L.; Kussoy, M. I.</p> <p>1988-01-01</p> <p>A <span class="hlt">shock</span>-related separation of a turbulent boundary <span class="hlt">layer</span> has been studied and documented. The flow was that of an axisymmetric turbulent boundary <span class="hlt">layer</span> over a 5.02-cm-diam cylinder that was aligned with the wind tunnel axis. The boundary <span class="hlt">layer</span> was compressed by a 30 deg half-angle conical flare, with the cone axis inclined at an angle alpha to the cylinder axis. Nominal test conditions were P sub tau equals 1.7 atm and M sub infinity equals 2.85. Measurements were confined to the upper-symmetry, phi equals 0 deg, plane. Data are presented for the cases of alpha equal to 0. 5. and 10 deg and include mean surface pressures, streamwise and normal mean velocities, kinematic turbulent stresses and kinetic energies, as well as reverse-flow intermittencies. All data are given in tabular form; pressures, streamwise velocities, turbulent shear stresses, and kinetic energies are also presented graphically.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/pages/biblio/1321421-technique-forming-solid-d2-layers-shock-timing-experiments-national-ignition-facility','SCIGOV-DOEP'); return false;" href="http://www.osti.gov/pages/biblio/1321421-technique-forming-solid-d2-layers-shock-timing-experiments-national-ignition-facility"><span id="translatedtitle">Technique for Forming Solid D2 and D-T <span class="hlt">Layers</span> for <span class="hlt">Shock</span> Timing Experiments at the National Ignition Facility</span></a></p> <p><a target="_blank" href="http://www.osti.gov/pages">DOE PAGESBeta</a></p> <p>Sater, J. D.; Espinosa-Loza, F.; Kozioziemski, B.; Mapoles, E. R.</p> <p>2016-07-11</p> <p>Capsule implosion experiments on the National Ignition Facility (NIF) are driven with a carefully tailored laser pulse that delivers a sequence of <span class="hlt">shocks</span> to the ablator and fuel. In order to ensure the <span class="hlt">shocks</span> converge at the desired position, the <span class="hlt">shock</span> strength and velocity are measured in experimental platforms referred to as keyhole targets. We made <span class="hlt">shock</span> measurements on capsules completely filled with liquid deuterium for the solid deuterium tritide (D-T) <span class="hlt">layer</span> campaigns. Modeling has been used to extend these results to form an estimate of the <span class="hlt">shock</span> properties in solid D-T <span class="hlt">layers</span>. Furthermore, to verify and improve the surrogacymore » of the liquid-filled keyhole measurements, we have developed a technique to form a solid <span class="hlt">layer</span> inside the keyhole capsule. The <span class="hlt">layer</span> is typically uniform over a 400-μm-diameter area. This is sufficient to allow direct measurement of the <span class="hlt">shock</span> velocity. This <span class="hlt">layering</span> technique has been successfully applied to 13 experiments on the NIF. The technique may also be applicable to fast-igniter experiments since some proposed designs resemble keyhole targets. We discuss our method in detail and give representative results.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFMSH21A2189L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFMSH21A2189L"><span id="translatedtitle">A Focused Transport Approach to SEP acceleration at a Fast <span class="hlt">Parallel</span> <span class="hlt">Shock</span> in the Corona Including Self-excitation of Alfvén Waves</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>le Roux, J. A.</p> <p>2012-12-01</p> <p>It has been argued that the acceleration of SEPS at a quasi-<span class="hlt">parallel</span> CME-driven <span class="hlt">shock</span> to GeV energies in the corona only occurs if strong wave-excitation by SEPs ahead of the <span class="hlt">shock</span> reduces the <span class="hlt">parallel</span> mean free path upstream, thus boosting the rate of diffusive <span class="hlt">shock</span> acceleration. To investigate this issue, we modeled SEP acceleration at a fast <span class="hlt">parallel</span> traveling <span class="hlt">shock</span> in the corona with an existing time-dependent focused transport model. The model has been expanded recently to also feature time-dependent self-excitation and damping of Alfvén waves by SEP anisotropies ahead of the <span class="hlt">shock</span> based on standard quasi-linear theory. Alfvén wave propagation near the traveling <span class="hlt">shock</span> is modeled based on standard theory for wave transport in a slowly varying non-uniform plasma medium. Preliminary results will be shown to illustrate the increase in wave power driven by SEP anisotropies upstream, the effect of the <span class="hlt">shock</span> wave in shortening the wave length and increasing the wave amplitude of Alfvén waves, and the associated acceleration of SEPs by 1st order Fermi acceleration to high energies. The role of the acceleration of the cross-<span class="hlt">shock</span> solar wind flow, which was found to create a downstream population of <span class="hlt">shock</span> pre-heated particles which forms an additional source for injection into 1st order Fermi acceleration, will be discussed in terms of how it affects self-excitation of Alfvén waves and the formation of high-energy SEPs by 1st order Fermi acceleration.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19910004339','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19910004339"><span id="translatedtitle">Turbulence modeling for sharp-fin-induced <span class="hlt">shock</span> wave/turbulent boundary-<span class="hlt">layer</span> interactions</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Horstman, C. C.</p> <p>1990-01-01</p> <p>Solutions of the Reynolds averaged Navier-Stokes equations are presented and compared with a family of experimental results for the 3-D interaction of a sharp fin induced <span class="hlt">shock</span> wave with a turbulent boundary <span class="hlt">layer</span>. Several algebraic and two equation eddy viscosity turbulence models are employed. The computed results are compared with experimental surface pressure, skin friction, and yaw angle data as well as the overall size of the interaction. Although the major feature of the flow fields are correctly predicted, several discrepancies are noted. Namely, the maximum skin friction values are significantly underpredicted for the strongest interaction cases. These and other deficiencies are discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19890011581','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19890011581"><span id="translatedtitle">Turbulent eddy viscosity modeling in transonic <span class="hlt">shock/boundary-layer</span> interactions</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Inger, G. R.</p> <p>1989-01-01</p> <p>The treatment of turbulence effects on transonic <span class="hlt">shock</span>/turbulent boundary <span class="hlt">layer</span> interaction is addressed within the context of a triple deck approach valid for arbitrary practical Reynolds numbers between 1000 and 10 billion. The modeling of the eddy viscosity and basic turbulent boundary profile effects in each deck is examined in detail using Law-of-the-Wall/Law-of-the-Wake concepts as the foundation. Results of parametric studies showing how each of these turbulence model aspects influences typical interaction zone property distributions (wall pressure, displacement thickness and local skin friction) are presented and discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19750022397','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19750022397"><span id="translatedtitle">Computer user's guide for a chemically reacting viscous <span class="hlt">shock-layer</span> program</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Miner, E. W.; Lewis, C. H.</p> <p>1975-01-01</p> <p>A description is given of the computer code for predicting viscous <span class="hlt">shock-layer</span> flows over nonanalytic blunt bodies (Program VISLNABB) for hypersonic, low Reynolds number flows. Four specific and one general body geometries are considered. In addition to sphere-cones, cylinder wedges and geometries defined in tabular form, options for hyperboloids and paraboloids are included. Details of the theory and results are included in a separate engineering report. The program, subroutines, variables in common, and input and output data are described. Listings of the program code, output data for a sample case, and the input data for this sample case are included.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19930083553','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19930083553"><span id="translatedtitle">Study of the Pressure Rise Across <span class="hlt">Shock</span> Waves Required to Separate Laminar and Turbulent Boundary <span class="hlt">Layers</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Donaldson, Coleman Dup; Lange, Roy H</p> <p>1952-01-01</p> <p>Results are presented of a dimensional study and an experimental investigation of the pressure rise across a <span class="hlt">shock</span> wave which causes separation of the boundary <span class="hlt">layer</span> on a flat plate. The experimental part of the investigation was conducted at a Mach number of 3.03 for a Reynolds number range of 2 x 10 (sup) 6 to 19 x 10 (sup) 6. The available experimental data are compared with the predictions of the present study, and the significance of the results obtained is discussed relative to certain practical design problems.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19880035137&hterms=you+measure+friction&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dyou%2Bmeasure%2Bfriction','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19880035137&hterms=you+measure+friction&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dyou%2Bmeasure%2Bfriction"><span id="translatedtitle">Skin friction measurements by laser interferometry in swept <span class="hlt">shock</span> wave/turbulent boundary-<span class="hlt">layer</span> interactions</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Kim, Kwang-Soo; Settles, Gary S.</p> <p>1988-01-01</p> <p>The laser interferometric skin friction meter was used to measure wall shear stress distributions in two interactions of fin-generated swept <span class="hlt">shock</span> waves with turbulent boundary <span class="hlt">layers</span>. The basic research configuration was an unswept sharp-leading-edge fin of variable angle mounted on a flatplate. The results indicate that such measurements are practical in high-speed interacting flows, and that a repeatability of + or - 6 percent or better is possible. Marked increases in wall shear were observed in both swept interactions tested.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19900032767&hterms=upstream&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DTitle%26N%3D0%26No%3D90%26Ntt%3Dupstream','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19900032767&hterms=upstream&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DTitle%26N%3D0%26No%3D90%26Ntt%3Dupstream"><span id="translatedtitle">Upstream-influence scaling of fin-generated <span class="hlt">shock</span> wave boundary-<span class="hlt">layer</span> interactions</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Lu, Frank K.; Settles, Gary S.</p> <p>1990-01-01</p> <p>An upstream-influence scaling law, previously formulated through analysis of Mach 3 data, has been extended to Mach numbers from 2.5 through 4. For adiabatic, equilibrium, turbulent boundary <span class="hlt">layers</span>, there is no Mach number effect on the constants in the Reynolds number parameters of this law. In addition, based on local similarity, a new Mach number parameter, namely, the Mach number component of the incoming stream normal to the farfield upstream influence, is proposed. Scaling by either the incoming Mach number normal to the inviscid <span class="hlt">shock</span> or by the incoming Mach number normal to the farfield upstream influence is equivalent to scaling by the hypersonic similarity parameter.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/25441032','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/25441032"><span id="translatedtitle"><span class="hlt">Shock</span>.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Wacker, David A; Winters, Michael E</p> <p>2014-11-01</p> <p>Critically ill patients with undifferentiated <span class="hlt">shock</span> are complex and challenging cases in the ED. A systematic approach to assessment and management is essential to prevent unnecessary morbidity and mortality. The simplified, systematic approach described in this article focuses on determining the presence of problems with cardiac function (the pump), intravascular volume (the tank), or systemic vascular resistance (the pipes). With this approach, the emergency physician can detect life-threatening conditions and implement time-sensitive therapy. PMID:25441032</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26813145','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26813145"><span id="translatedtitle">Bi-directional series-<span class="hlt">parallel</span> elastic actuator and overlap of the actuation <span class="hlt">layers</span>.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Furnémont, Raphaël; Mathijssen, Glenn; Verstraten, Tom; Lefeber, Dirk; Vanderborght, Bram</p> <p>2016-02-01</p> <p>Several robotics applications require high torque-to-weight ratio and energy efficient actuators. Progress in that direction was made by introducing compliant elements into the actuation. A large variety of actuators were developed such as series elastic actuators (SEAs), variable stiffness actuators and <span class="hlt">parallel</span> elastic actuators (PEAs). SEAs can reduce the peak power while PEAs can reduce the torque requirement on the motor. Nonetheless, these actuators still cannot meet performances close to humans. To combine both advantages, the series <span class="hlt">parallel</span> elastic actuator (SPEA) was developed. The principle is inspired from biological muscles. Muscles are composed of motor units, placed in <span class="hlt">parallel</span>, which are variably recruited as the required effort increases. This biological principle is exploited in the SPEA, where springs (<span class="hlt">layers</span>), placed in <span class="hlt">parallel</span>, can be recruited one by one. This recruitment is performed by an intermittent mechanism. This paper presents the development of a SPEA using the MACCEPA principle with a self-closing mechanism. This actuator can deliver a bi-directional output torque, variable stiffness and reduced friction. The load on the motor can also be reduced, leading to a lower power consumption. The variable recruitment of the <span class="hlt">parallel</span> springs can also be tuned in order to further decrease the consumption of the actuator for a given task. First, an explanation of the concept and a brief description of the prior work done will be given. Next, the design and the model of one of the <span class="hlt">layers</span> will be presented. The working principle of the full actuator will then be given. At the end of this paper, experiments showing the electric consumption of the actuator will display the advantage of the SPEA over an equivalent stiff actuator. PMID:26813145</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013PhDT.......338H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013PhDT.......338H"><span id="translatedtitle">The effects of micro-vortex generators on normal <span class="hlt">shock</span> wave/boundary <span class="hlt">layer</span> interactions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Herges, Thomas G.</p> <p></p> <p><span class="hlt">Shock</span> wave/boundary-<span class="hlt">layer</span> interactions (SWBLIs) are complex flow phenomena that are important in the design and performance of internal supersonic and transonic flow fields such as engine inlets. This investigation was undertaken to study the effects of passive flow control devices on normal <span class="hlt">shock</span> wave/boundary <span class="hlt">layer</span> interactions in an effort to gain insight into the physics that govern these complex interactions. The work concentrates on analyzing the effects of vortex generators (VGs) as a flow control method by contributing a greater understanding of the flowfield generated by these devices and characterizing their effects on the SWBLI. The vortex generators are utilized with the goal of improving boundary <span class="hlt">layer</span> health (i.e., reducing/increasing the boundary-<span class="hlt">layer</span> incompressible shape factor/skin friction coefficient) through a SWBLI, increasing pressure recovery, and reducing flow distortion at the aerodynamic interface plane while adding minimal drag to the system. The investigation encompasses experiments in both small-scale and large-scale inlet testing, allowing multiple test beds for improving the characterization and understanding of vortex generators. Small-scale facility experiments implemented instantaneous schlieren photography, surface oil-flow visualization, pressure-sensitive paint, and particle image velocimetry to characterize the effects of an array of microramps on a normal <span class="hlt">shock</span> wave/boundary-<span class="hlt">layer</span> interaction. These diagnostics measured the time-averaged and instantaneous flow organization in the vicinity of the microramps and SWBLI. The results reveal that a microramp produces a complex vortex structure in its wake with two primary counter-rotating vortices surrounded by a train of Kelvin- Helmholtz (K-H) vortices. A streamwise velocity deficit is observed in the region of the primary vortices in addition to an induced upwash/downwash which persists through the normal <span class="hlt">shock</span> with reduced strength. The microramp flow control also increased the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012PhDT.......176P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012PhDT.......176P"><span id="translatedtitle">Direct Numerical Simulation of Two <span class="hlt">Shock</span> Wave/Turbulent Boundary <span class="hlt">Layer</span> Interactions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Priebe, Stephan</p> <p></p> <p>Direct numerical simulations (DNSs) of two <span class="hlt">shock</span> wave/turbulent boundary <span class="hlt">layer</span> interactions (STBLIs) are presented in this thesis. The first interaction is a 24° compression ramp at Mach 2.9, and the second interaction is an 8° compression ramp at Mach 7.2. The large-scale low-frequency unsteadiness in the Mach 2.9 DNS is investigated with the aim of shedding some light on its physical origin. Previous experimental and computational works have linked the unsteadiness either to fluctuations in the incoming boundary <span class="hlt">layer</span> or to a mechanism in the downstream separated flow. Consistent with experimental observations, the <span class="hlt">shock</span> in the DNS is found to undergo streamwise oscillations, which are broadband and occur at frequencies that are about two orders of magnitude lower than the characteristic frequency of the energy-containing turbulent scales in the incoming boundary <span class="hlt">layer</span>. Based on a coherence and phase analysis of signals at the wall and in the flow field, it is found that the low frequency <span class="hlt">shock</span> unsteadiness is statistically linked to pulsations of the downstream separated flow. The statistical link with fluctuations in the upstream boundary <span class="hlt">layer</span> is also investigated. A weak link is observed: the value of the low-frequency coherence with the upstream flow is found to lie just above the limit of statistical significance, which is determined by means of a Monte Carlo study. The dynamics of the downstream separated flow are characterized further based on low-pass filtered DNS fields. The results suggest that structural changes occur in the downstream separated flow during the low-frequency motions, including the breaking-up of the separation bubble, which is observed when the <span class="hlt">shock</span> moves downstream. The structural changes are described based on the Cf distribution through the interaction, as well as the velocity and vorticity fields. The possible link between the low-frequency dynamics observed in the DNS and results from global instability theory is explored. It</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19730051995&hterms=atomic+composition&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Datomic%2Bcomposition','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19730051995&hterms=atomic+composition&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Datomic%2Bcomposition"><span id="translatedtitle">Composition of the earth's atmosphere by <span class="hlt">shock-layer</span> radiometry during the PAET entry probe experiment.</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Whiting, E. E.; Arnold, J. O.; Page, W. A.; Reynolds, R. M.</p> <p>1973-01-01</p> <p>A determination of the composition of the earth's atmosphere obtained from onboard radiometer measurements of the spectra emitted from the bow <span class="hlt">shock</span> <span class="hlt">layer</span> of a high-speed entry probe is reported. The N2, O2, CO2, and noble gas concentrations in the earth's atmosphere were determined to good accuracy by this technique. The results demonstrate unequivocally the feasibility of determining the composition of an unknown planetary atmosphere by means of a multichannel radiometer viewing optical emission from the heated atmospheric gases in the region between the bow <span class="hlt">shock</span> wave and the vehicle surface. The spectral locations in this experiment were preselected to enable the observation of CN violet, N2(+) first negative and atomic oxygen emission at 3870, 3910, and 7775 A, respectively. The atmospheric gases were heated and compressed by the <span class="hlt">shock</span> wave to a peak temperature of about 6100 K and a corresponding pressure of 0.4 atm. Complete descriptions of the data analysis technique and the onboard radiometer and its calibration are given.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013APS..DFD.1A017J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013APS..DFD.1A017J"><span id="translatedtitle">On the critical radii for ramp induced <span class="hlt">shock</span> wave and laminar boundary <span class="hlt">layer</span> interaction</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>John, Bibin; Kulkarni, Vinayak</p> <p>2013-11-01</p> <p>The <span class="hlt">shock</span> wave and laminar boundary <span class="hlt">layer</span> interaction is classical example of viscous and inviscid interaction. All the characteristic features of this interaction like separation length, separation and reattachment locations, upstream influence etc. are dependent on the leading edge bluntness. Upstream over pressure region and interaction of entropy <span class="hlt">layer</span> with boundary <span class="hlt">layer</span> alter this dynamics in the presence of blunt leading edge. Two critical radii corresponding to maximum separation size and separation length equal to reference sharp leading edge case are observed for this interaction during the present numerical studies. Freestream Mach number, wall temperature and freestream stagnation enthalpy are the governing parameters for the two critical radii for given configuration. Numerical simulations are then carried out to understand the effect of these parameters on the magnitude of the critical radii. Entropy <span class="hlt">layer</span> swallowing by boundary <span class="hlt">layer</span> and extension of over pressure region are reconsidered for alterations in these radii. Present studies are found very useful in devising mechanism for estimation of critical radii and as well for incorporating the amendment in the same due to change in governing parameters.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19780057957&hterms=bangalore&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3Dbangalore','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19780057957&hterms=bangalore&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3Dbangalore"><span id="translatedtitle">Injection slot location for boundary-<span class="hlt">layer</span> control in <span class="hlt">shock</span>-induced separation</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Viswanath, P. R.; Sankaran, L.; Sagdeo, P. M.; Narasimha, R.; Prabhu, A.</p> <p>1978-01-01</p> <p>An experimental investigation of the effect of tangential air injection, when the injection slot is located inside of what would otherwise have been the dead air zone in a separated flow, in controlling <span class="hlt">shock</span>-induced turbulent boundary <span class="hlt">layer</span> separation is presented. The experiments were carried out at a free-stream Mach number of 2.5 in the separated flow induced by a compression corner with a 20 deg angle. The observations made were wall static pressures, pitot profiles, and schlieren visualizations of the flow. The results show that the present location for injection is more effective in suppressing boundary-<span class="hlt">layer</span> separation than the more conventional one, where the slot is located upstream of where separation would occur in the absence of injection.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015DokPh..60...89S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015DokPh..60...89S"><span id="translatedtitle">Spatial ionization effects of a <span class="hlt">shock</span> <span class="hlt">layer</span> in the RAM-C-II flight experiment</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Surzhikov, S. T.</p> <p>2015-02-01</p> <p>A three-dimensional computer model of the nonequilibrium ionization aerophysics of descent moduli entering dense atmospheric <span class="hlt">layers</span> with orbital velocity in the height range of 60-90 km is developed. A three-dimensional numerical analysis of the experimental data on the ionization of the <span class="hlt">shock</span> <span class="hlt">layer</span> near the surface of a hypersonic flying module having the form of a blunt-sphere cone with the flight velocity higher than 7.5 km/s at heights of 61-81 km is fulfilled. The data of the flight experiment are obtained in the framework of the RAM-C-II investigatory program. The use of a three-dimensional computer model made it possible to find the calculated data in good agreement with the flight experiment data, as well as to explain some spatial effects not considered before.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19930015348','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19930015348"><span id="translatedtitle">Intersecting <span class="hlt">Shock</span>-Wave/Turbulent Boundary-<span class="hlt">Layer</span> Interactions at Mach 8.3</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Kussoy, M. I.; Horstman, K. C.</p> <p>1992-01-01</p> <p>Experimental data for two three-dimensional intersecting <span class="hlt">shock</span>-wave/turbulent boundary-<span class="hlt">layer</span> interaction flows at Mach 8.3 are presented. The test bodies, composed of two sharp fins fastened to a flat-plate test bed, were designed to generate flows with varying degrees of pressure gradient, boundary-<span class="hlt">layer</span> separation, and turning angle. The data include surface pressure and heat transfer distributions as well as mean flow-field surveys both in the undisturbed and interaction regimes. The data are presented in a convenient form to be used to validate existing or future computational models of these hypersonic flows. The data are also on a 3.5-inch diskette included and are available through E-mail.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014APS..DFDD35007S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014APS..DFDD35007S"><span id="translatedtitle">Space-time measurements in a <span class="hlt">shock</span> wave/turbulent boundary <span class="hlt">layer</span> interaction</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Schreyer, Anne-Marie; Dupont, Pierre</p> <p>2014-11-01</p> <p>We study a reflected <span class="hlt">shock</span> interaction with separation at Mach 2, contributing to a better understanding of rocket engine nozzle flows. The flow field contains a wide range of characteristic frequencies between O (100) Hz for the oscillation of the reflected <span class="hlt">shock</span> and O (100) kHz for the turbulent microscales. To explain the origin and interdependence of the physical phenomena in the interaction, we need access to the spatio-temporal links. We thus require a measurement technique allowing the resolution of the entire frequency range while also providing sufficient spatial resolution and a large field of view. Our newly developed Dual-PIV system satisfies these requirements. First measurements with this system in an interaction flow field were performed in the continuous hypo-turbulent wind-tunnel at IUSTI at a momentum thickness Reynolds number of Reθ = 5024 and a deflection angle of θ = 8 .75° . We present a detailed characterization of the flow field including turbulence measurements. From measurements at a range of temporal delays, we determined autocorrelations at crucial points in the flow field (incoming boundary <span class="hlt">layer</span>, mixing <span class="hlt">layer</span>, relaxation zone). From these, spatio-temporal information like the integral scales and the convection velocity are deduced. This work received financial support by the CNES within the research program ATAC and also the ANR within the program DECOMOS. This support is gratefully acknowledged.</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_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li class="active"><span>11</span></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_13");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_11 --> <div id="page_12" 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_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li class="active"><span>12</span></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_13");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="221"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20150006750','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20150006750"><span id="translatedtitle">Mitigation of Adverse Effects Caused by <span class="hlt">Shock</span> Wave Boundary <span class="hlt">Layer</span> Interactions Through Optimal Wall Shaping</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Liou, May-Fun; Lee, Byung Joon</p> <p>2013-01-01</p> <p>It is known that the adverse effects of <span class="hlt">shock</span> wave boundary <span class="hlt">layer</span> interactions in high speed inlets include reduced total pressure recovery and highly distorted flow at the aerodynamic interface plane (AIP). This paper presents a design method for flow control which creates perturbations in geometry. These perturbations are tailored to change the flow structures in order to minimize <span class="hlt">shock</span> wave boundary <span class="hlt">layer</span> interactions (SWBLI) inside supersonic inlets. Optimizing the shape of two dimensional micro-size bumps is shown to be a very effective flow control method for two-dimensional SWBLI. In investigating the three dimensional SWBLI, a square duct is employed as a baseline. To investigate the mechanism whereby the geometric elements of the baseline, i.e. the bottom wall, the sidewall and the corner, exert influence on the flow's aerodynamic characteristics, each element is studied and optimized separately. It is found that arrays of micro-size bumps on the bottom wall of the duct have little effect in improving total pressure recovery though they are useful in suppressing the incipient separation in three-dimensional problems. Shaping sidewall geometry is effective in re-distributing flow on the side wall and results in a less distorted flow at the exit. Subsequently, a near 50% reduction in distortion is achieved. A simple change in corner geometry resulted in a 2.4% improvement in total pressure recovery.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013ExFl...54.1598E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013ExFl...54.1598E"><span id="translatedtitle">Experiments on transitional <span class="hlt">shock</span> wave--boundary <span class="hlt">layer</span> interactions at Mach 5</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Erdem, E.; Kontis, K.; Johnstone, E.; Murray, N. P.; Steelant, J.</p> <p>2013-10-01</p> <p>An experimental campaign was carried out to investigate transitional <span class="hlt">shock</span> wave--boundary <span class="hlt">layer</span> interactions (SWBLI) at Mach and unit Reynolds numbers of 5 and 15.9 × 106 1/m, respectively. An impinging <span class="hlt">shock</span> that generates 7° flow deflection resulted in separated SWBLI flowfield on axisymmetric centrebody. Various flow diagnostics were utilised such as schlieren photography, quantitative infrared thermography, shear sensitive liquid crystals, pressure sensitive paints and particle image velocimetry (PIV) to provide a complete time-averaged experimental data set. One nominally laminar case (with triggered transition due to SWBLI) and four natural transition cases with varying intermittency were tested. Heat transfer and shear stress peaks occurred around the reattachment point. For nominally laminar case, the separation induces transition, and thus, heat transfer and pressure peaks were found to be the highest. For the cases with natural transition with different intermittency levels, where incoming boundary <span class="hlt">layer</span> is in state of transition, the magnitude of pressure and heat transfer peaks initially started to increase reaching a maximum and afterwards decreased towards the highest intermittency case. The presence of streamwise vortices was apparent for laminar case. Pressure peaks were found to occur slightly downstream of heat flux/shear stress peaks. PIV results (for laminar case only) showed high levels of turbulence above the separation region, proving triggered transition behaviour.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19830055174&hterms=OM&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3DOM','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19830055174&hterms=OM&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3DOM"><span id="translatedtitle">An integral analysis of transonic normal <span class="hlt">shock</span> wave/turbulent boundary <span class="hlt">layer</span> interactions in internal flow</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Om, D.; Childs, M. E.</p> <p>1983-01-01</p> <p>An approximate integral viscous-inviscid interaction method is presented for calculating the development of a turbulent boundary <span class="hlt">layer</span> subjected to a normal <span class="hlt">shock</span> wave induced adverse pressure gradient in an internal axisymmetric flow. The inflow conditions and the downstream pressure are provided for the computation. In the supersonic region of <span class="hlt">shock</span> pressure rise, the Prandtl-Meyer function is used to couple the viscous and inviscid flows. An analytical model for the coupling process is postulated and appropriate equations are defined. Downstream of the sonic point, one-dimensional inviscid flow is assumed for coupling with the viscous flow. The turbulent boundary <span class="hlt">layer</span> is calculated using Green's integral lag-entrainment method. Comparisons of the solutions with the experimental data are made for interactions which are unseparated, near separation and separated. For comparison purposes, solutions to the time-dependent, mass-averaged, Navier-Stokes equations incorporating a two-equation, Wilcox-Rubesin turbulence model are also shown. The computed results from the integral method show good agreement with experimental data for unseparated interactions and reasonable agreement with the trend of the viscous effects when the interaction becomes increasingly separated.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20080043603','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20080043603"><span id="translatedtitle">Non-Boltzmann Modeling for Air <span class="hlt">Shock-Layer</span> Radiation at Lunar-Return Conditions</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Johnston, Christopher O.; Hollis, Brian R.; Sutton, Kenneth</p> <p>2008-01-01</p> <p>This paper investigates the non-Boltzmann modeling of the radiating atomic and molecular electronic states present in lunar-return <span class="hlt">shock-layers</span>. The Master Equation is derived for a general atom or molecule while accounting for a variety of excitation and de-excitation mechanisms. A new set of electronic-impact excitation rates is compiled for N, O, and N2+, which are the main radiating species for most lunar-return <span class="hlt">shock-layers</span>. Based on these new rates, a novel approach of curve-fitting the non-Boltzmann populations of the radiating atomic and molecular states is developed. This new approach provides a simple and accurate method for calculating the atomic and molecular non-Boltzmann populations while avoiding the matrix inversion procedure required for the detailed solution of the Master Equation. The radiative flux values predicted by the present detailed non-Boltzmann model and the approximate curve-fitting approach are shown to agree within 5% for the Fire 1634 s case.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22038530','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22038530"><span id="translatedtitle">Modeling of the plasma generated in a rarefied hypersonic <span class="hlt">shock</span> <span class="hlt">layer</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Farbar, Erin D.; Boyd, Iain D.</p> <p>2010-10-15</p> <p>In this study, a rigorous numerical model is developed to simulate the plasma generated in a rarefied, hypersonic <span class="hlt">shock</span> <span class="hlt">layer</span>. The model uses the direct simulation Monte Carlo (DSMC) method to treat the particle collisions and the particle-in-cell (PIC) method to simulate the plasma dynamics in a self-consistent manner. The model is applied to compute the flow along the stagnation streamline in front of a blunt body reentering the Earth's atmosphere at very high velocity. Results from the rigorous DSMC-PIC model are compared directly to the standard DSMC modeling approach that uses the ambipolar diffusion approximation to simulate the plasma dynamics. It is demonstrated that the self-consistent computation of the plasma dynamics using the rigorous DSMC-PIC model captures many physical phenomena not accurately predicted by the standard modeling approach. These computations represent the first assessment of the validity of the ambipolar diffusion approximation when predicting the rarefied plasma generated in a hypersonic <span class="hlt">shock</span> <span class="hlt">layer</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19920071486&hterms=knowledge+transfer&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dknowledge%2Btransfer','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19920071486&hterms=knowledge+transfer&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dknowledge%2Btransfer"><span id="translatedtitle">Heat transfer measurements and CFD comparison of swept <span class="hlt">shock</span> wave/boundary-<span class="hlt">layer</span> interactions</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Lee, Y.; Settles, G. S.; Horstman, C. C.</p> <p>1992-01-01</p> <p>An experimental research program providing basic knowledge and establishing new data on the heat transfer in swept <span class="hlt">shock</span> wave/boundary-<span class="hlt">layer</span> interactions is described. An equilibrium turbulent boundary-<span class="hlt">layer</span> on a flat plate is subjected to impingement by swept planar <span class="hlt">shock</span> waves generated by a sharp fin. Five different interactions with fin angles ranging from 10 to 20 deg at freestream Mach numbers of 3.0 and 4.0 produce a variety of interaction strengths from weak to very strong. A foil heater generates a uniform heat flux over the flat plate surface and miniature thin-film-resistance sensors mounted on it are used to measure the local surface temperature. The heat convection equation is then solved for the heat transfer distribution within an interaction, yielding a total uncertainty of about +/- 10 percent. These experimental data are compared with the results of numerical Navier-Stokes solutions which employ a kappa-epsilon turbulence model. Finally, a simplified form of the peak heat transfer correlation for fin interactions is suggested.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013PhDT.......156C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013PhDT.......156C"><span id="translatedtitle">Study of <span class="hlt">shock</span> wave boundary <span class="hlt">layer</span> interaction phenonemon using color schlieren and snapshot Proper Orthogonal Decomposition</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chaganti Subrahmanya Datta, Narendra</p> <p></p> <p>The flow structure of shockwave boundary <span class="hlt">layer</span> interaction (SWBLI) has been studied using Rainbow Schlieren Deflectometry (RSD), Ensemble Averaging, Fast Fourier Transform (FFT), and snapshot Proper Orthogonal Decomposition (POD) techniques. The Mach number of the approach free-stream was Mach = 3. Shockwave was generated with a 12° wedge. The color schlieren pictures are used to determine the transverse ray deflections at each pixel of the pictures taken using a high speed camera. The interaction region structure is described statistically with the ensemble average and, root mean square deflections. FFT technique is used to determine the dominant frequencies at different regions of the flow field. Results indicate that low frequency oscillations dominate the flow field. The POD technique results complement the findings of the ensemble averaging technique and show that distinct regions contain most of the energy in the flow field. These distinct regions are located around the reflected <span class="hlt">shock</span>, around the <span class="hlt">shock</span> wave reaching into the approach boundary <span class="hlt">layer</span> and around the separation region over the edge of the separation bubble.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004RScI...75.4789S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004RScI...75.4789S"><span id="translatedtitle">On the efficiency of Gore-Tex <span class="hlt">layer</span> for brain protection from <span class="hlt">shock</span> wave damage in cranioplasty</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Saito, T.; Voinovich, P. A.; Nakagawa, A.; Hosseini, S. H. R.; Takayama, K.; Hirano, T.</p> <p>2004-11-01</p> <p>The effectiveness of a Gore-Tex <span class="hlt">layer</span> for protecting soft tissue from damage in <span class="hlt">shock</span> wave therapy is investigated analytically, numerically and experimentally. Analytical considerations based on the fundamentals of wave dynamics and two-dimensional numerical simulations based on the elastodynamic equations are carried out for underwater <span class="hlt">shock</span> wave propagation and interaction with Gore-Tex membrane models of different complexity. The results clearly demonstrate that considerable attenuation of <span class="hlt">shock</span> waves with Gore-Tex is due to the air trapped inside the membrane. The experimental results confirm that a Gore-Tex sheet placed in the liquid reduces the transmitted <span class="hlt">shock</span> wave peak overpressure significantly, by up to two orders of magnitude. Another experimental series reveals what kind of damage in the rat brain tissue can be caused by <span class="hlt">shock</span> waves of different intensity.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19940010307','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19940010307"><span id="translatedtitle">Interaction of two glancing, crossing <span class="hlt">shock</span> waves with a turbulent boundary-<span class="hlt">layer</span> at various Mach numbers</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hingst, Warren R.; Williams, Kevin E.</p> <p>1991-01-01</p> <p>A preliminary experimental investigation was conducted to study two crossing, glancing <span class="hlt">shock</span> waves of equal strengths, interacting with the boundary-<span class="hlt">layer</span> developed on a supersonic wind tunnel wall. This study was performed at several Mach numbers between 2.5 and 4.0. The <span class="hlt">shock</span> waves were created by fins (<span class="hlt">shock</span> generators), spanning the tunnel test section, that were set at angles varying from 4 to 12 degrees. The data acquired are wall static pressure measurements, and qualitative information in the form of oil flow and schlieren visualizations. The principle aim is two-fold. First, a fundamental understanding of the physics underlying this flow phenomena is desired. Also, a comprehensive data set is needed for computational fluid dynamic code validation. Results indicate that for small <span class="hlt">shock</span> generator angles, the boundary-<span class="hlt">layer</span> remains attached throughout the flow field. However, with increasing <span class="hlt">shock</span> strengths (increasing generator angles), boundary <span class="hlt">layer</span> separation does occur and becomes progressively more severe as the generator angles are increased further. The location of the separation, which starts well downstream of the <span class="hlt">shock</span> crossing point, moves upstream as <span class="hlt">shock</span> strengths are increased. At the highest generator angles, the separation appears to begin coincident with the generator leading edges and engulfs most of the area between the generators. This phenomena occurs very near the 'unstart' limit for the generators. The wall pressures at the lower generator angles are nominally consistent with the flow geometries (i.e. <span class="hlt">shock</span> patterns) although significantly affected by the boundary-<span class="hlt">layer</span> upstream influence. As separation occurs, the wall pressures exhibit a gradient that is mainly axial in direction in the vicinity of the separation. At the limiting conditions the wall pressure gradients are primarily in the axial direction throughout.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19730022509','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19730022509"><span id="translatedtitle">Prediction and measurement of heat transfer rates for the <span class="hlt">shock</span>-induced unsteady laminar boundary <span class="hlt">layer</span> on a flat plate</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Cook, W. J.</p> <p>1972-01-01</p> <p>The unsteady laminar boundary <span class="hlt">layer</span> induced by the flow-initiating <span class="hlt">shock</span> wave passing over a flat plate mounted in a <span class="hlt">shock</span> tube was theoretically and experimentally studied in terms of heat transfer rates to the plate for <span class="hlt">shock</span> speeds ranging from 1.695 to 7.34 km/sec. The theory presented by Cook and Chapman for the <span class="hlt">shock</span>-induced unsteady boundary <span class="hlt">layer</span> on a plate is reviewed with emphasis on unsteady heat transfer. A method of measuring time-dependent heat-transfer rates using thin-film heat-flux gages and an associated data reduction technique are outlined in detail. Particular consideration is given to heat-flux measurement in short-duration ionized shocktube flows. Experimental unsteady plate heat transfer rates obtained in both air and nitrogen using thin-film heat-flux gages generally agree well with theoretical predictions. The experimental results indicate that the theory continues to predict the unsteady boundary <span class="hlt">layer</span> behavior after the <span class="hlt">shock</span> wave leaves the trailing edge of the plate even though the theory is strictly applicable only for the time interval in which the <span class="hlt">shock</span> remains on the plate.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009APS..DFD.AD001W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009APS..DFD.AD001W"><span id="translatedtitle"><span class="hlt">Shock</span> Wave/Boundary <span class="hlt">Layer</span> Interaction Control in a Supersonic Inlet</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Webb, Nathan; Caraballo, Edgar; Little, Jesse; Kim, Jin-Hwa; Samimy, Mo</p> <p>2009-11-01</p> <p>A <span class="hlt">shock</span> wave/boundary <span class="hlt">layer</span> interaction (SWBLI) occurs in a supersonic mixed compression inlet. The SWBLI could cause boundary <span class="hlt">layer</span> separation resulting in adverse consequences such as reduced pressure recovery and non-uniform fan loading. Boundary <span class="hlt">layer</span> bleed is currently used to prevent separation, which incurs a significant performance penalty. We have recently used Localized Arc Filament Plasma Actuators (LAFPAs) with high amplitude and wide bandwidth to control the SWBLI in a Mach 1.9 flow. The preliminary results are promising and show excellent potential for this technique. These actuators may affect the SWBLI by two mechanisms: manipulation of flow instabilities and/or streamwise vorticity generation. Particle image velocimetry measurements have confirmed that instability manipulation is the key to the LAFPAs' ability to significantly energize the boundary <span class="hlt">layer</span> in the interaction region. The streamwise vorticity effects are currently being investigated. The LAFPAs have been tested at varying frequency, duty cycle, and mode to determine the parameters with the maximum effectiveness. Supported by AFRL and AFOSR.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19970018536','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19970018536"><span id="translatedtitle">Experimental Investigation of Unsteady <span class="hlt">Shock</span> Wave Turbulent Boundary <span class="hlt">Layer</span> Interactions About a Blunt Fin</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Barnhart, Paul J.; Greber, Isaac</p> <p>1997-01-01</p> <p>A series of experiments were performed to investigate the effects of Mach number variation on the characteristics of the unsteady <span class="hlt">shock</span> wave/turbulent boundary <span class="hlt">layer</span> interaction generated by a blunt fin. A single blunt fin hemicylindrical leading edge diameter size was used in all of the experiments which covered the Mach number range from 2.0 to 5.0. The measurements in this investigation included surface flow visualization, static and dynamic pressure measurements, both on centerline and off-centerline of the blunt fin axis. Surface flow visualization and static pressure measurements showed that the spatial extent of the <span class="hlt">shock</span> wave/turbulent boundary <span class="hlt">layer</span> interaction increased with increasing Mach number. The maximum static pressure, normalized by the incoming static pressure, measured at the peak location in the separated flow region ahead of the blunt fin was found to increase with increasing Mach number. The mean and standard deviations of the fluctuating pressure signals from the dynamic pressure transducers were found to collapse to self-similar distributions as a function of the distance perpendicular to the separation line. The standard deviation of the pressure signals showed initial peaked distribution, with the maximum standard deviation point corresponding to the location of the separation line at Mach number 3.0 to 5.0. At Mach 2.0 the maximum standard deviation point was found to occur significantly upstream of the separation line. The intermittency distributions of the separation <span class="hlt">shock</span> wave motion were found to be self-similar profiles for all Mach numbers. The intermittent region length was found to increase with Mach number and decrease with interaction sweepback angle. For Mach numbers 3.0 to 5.0 the separation line was found to correspond to high intermittencies or equivalently to the downstream locus of the separation <span class="hlt">shock</span> wave motion. The Mach 2.0 tests, however, showed that the intermittent region occurs significantly upstream of the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19720010625','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19720010625"><span id="translatedtitle">A thin-<span class="hlt">shock-layer</span> solution for nonequilibrium, inviscid hypersonic flows in earth, Martian, and Venusian atmospheres</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Grose, W. L.</p> <p>1971-01-01</p> <p>An approximate inverse solution is presented for the nonequilibrium flow in the inviscid <span class="hlt">shock</span> <span class="hlt">layer</span> about a vehicle in hypersonic flight. The method is based upon a thin-<span class="hlt">shock-layer</span> approximation and has the advantage of being applicable to both subsonic and supersonic regions of the <span class="hlt">shock</span> <span class="hlt">layer</span>. The relative simplicity of the method makes it ideally suited for programming on a digital computer with a significant reduction in storage capacity and computing time required by other more exact methods. Comparison of nonequilibrium solutions for an air mixture obtained by the present method is made with solutions obtained by two other methods. Additional cases are presented for entry of spherical nose cones into representative Venusian and Martian atmospheres. A digital computer program written in FORTRAN language is presented that permits an arbitrary gas mixture to be employed in the solution. The effects of vibration, dissociation, recombination, electronic excitation, and ionization are included in the program.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19780015447','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19780015447"><span id="translatedtitle">A numerical solution of the Navier-Stokes equations for chemically nonequilibrium, merged stagnation <span class="hlt">shock</span> <span class="hlt">layers</span> on spheres and two-dimensional cylinders in air</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Johnston, K. D.; Hendricks, W. L.</p> <p>1978-01-01</p> <p>Results of solving the Navier-Stokes equations for chemically nonequilibrium, merged stagnation <span class="hlt">shock</span> <span class="hlt">layers</span> on spheres and two-dimensional cylinders are presented. The effects of wall catalysis and slip are also examined. The thin <span class="hlt">shock</span> <span class="hlt">layer</span> assumption is not made, and the thick viscous <span class="hlt">shock</span> is allowed to develop within the computational domain. The results show good comparison with existing data. Due to the more pronounced merging of <span class="hlt">shock</span> <span class="hlt">layer</span> and boundary <span class="hlt">layer</span> for the sphere, the heating rates for spheres become higher than those for cylinders as the altitude is increased.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012SPIE.8539E..08H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012SPIE.8539E..08H"><span id="translatedtitle">GPU-based <span class="hlt">parallel</span> implementation of 5-<span class="hlt">layer</span> thermal diffusion scheme</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Huang, Melin; Mielikainen, Jarno; Huang, Bormin; Huang, H.-L. A.; Goldberg, Mitchell D.</p> <p>2012-10-01</p> <p>The Weather Research and Forecasting (WRF) is a system of numerical weather prediction and atmospheric simulation with dual purposes for forecasting and research. The WRF software infrastructure consists of several components such as dynamic solvers and physical simulation modules. WRF includes several Land-Surface Models (LSMs). The LSMs use atmospheric information, the radiative and precipitation forcing from the surface <span class="hlt">layer</span> scheme, the radiation scheme, and the microphysics/convective scheme all together with the lands state variables and land-surface properties, to provide heat and moisture fluxes over land and sea-ice points. The WRF 5-<span class="hlt">layer</span> thermal diffusion simulation is an LSM based on the MM5 5-<span class="hlt">layer</span> soil temperature model with an energy budget that includes radiation, sensible, and latent heat flux. The WRF LSMs are very suitable for massively <span class="hlt">parallel</span> computation as there are no interactions among horizontal grid points. More and more scientific applications have adopted graphics processing units (GPUs) to accelerate the computing performance. This study demonstrates our GPU massively <span class="hlt">parallel</span> computation efforts on the WRF 5-<span class="hlt">layer</span> thermal diffusion scheme. Since this scheme is only an intermediate module of the entire WRF model, the I/O transfer does not involve in the intermediate process. Without data transfer, this module can achieve a speedup of 36x with one GPU and 108x with four GPUs as compared to a single threaded CPU processor. With CPU/GPU hybrid strategy, this module can accomplish a even higher speedup, ~114x with one GPU and ~240x with four GPUs. Meanwhile, we are seeking other approaches to improve the speeds.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19910023127','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19910023127"><span id="translatedtitle">An approximate viscous <span class="hlt">shock</span> <span class="hlt">layer</span> technique for calculating chemically reacting hypersonic flows about blunt-nosed bodies</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Cheatwood, F. Mcneil; Dejarnette, Fred R.</p> <p>1991-01-01</p> <p>An approximate axisymmetric method was developed which can reliably calculate fully viscous hypersonic flows over blunt nosed bodies. By substituting Maslen's second order pressure expression for the normal momentum equation, a simplified form of the viscous <span class="hlt">shock</span> <span class="hlt">layer</span> (VSL) equations is obtained. This approach can solve both the subsonic and supersonic regions of the <span class="hlt">shock</span> <span class="hlt">layer</span> without a starting solution for the <span class="hlt">shock</span> shape. The approach is applicable to perfect gas, equilibrium, and nonequilibrium flowfields. Since the method is fully viscous, the problems associated with a boundary <span class="hlt">layer</span> solution with an inviscid <span class="hlt">layer</span> solution are avoided. This procedure is significantly faster than the parabolized Navier-Stokes (PNS) or VSL solvers and would be useful in a preliminary design environment. Problems associated with a previously developed approximate VSL technique are addressed before extending the method to nonequilibrium calculations. Perfect gas (laminar and turbulent), equilibrium, and nonequilibrium solutions were generated for airflows over several analytic body shapes. Surface heat transfer, skin friction, and pressure predictions are comparable to VSL results. In addition, computed heating rates are in good agreement with experimental data. The present technique generates its own <span class="hlt">shock</span> shape as part of its solution, and therefore could be used to provide more accurate initial <span class="hlt">shock</span> shapes for higher order procedures which require starting solutions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1984cals.reptR....H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1984cals.reptR....H"><span id="translatedtitle">Experimental studies of Quasi-Two-Dimensional and three-dimensional viscous interaction regions induced by skewed-<span class="hlt">shock</span> and swept-<span class="hlt">shock</span> boundary <span class="hlt">layer</span> interactions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Holden, M. S.</p> <p>1984-07-01</p> <p>This report describes results from 3 experimental studies designed to examine the aerothermal characteristics of regions of three-dimensional <span class="hlt">shock</span> wave/boundary <span class="hlt">layer</span> interaction in high-speed flow over non-adiabatic surfaces. The objectives were: (1) to explore the basic mechanisms associated with 3D boundary <span class="hlt">layer</span> separation in high-speed flows with special emphasis on the large heat transfer rates and gradients developed in the separation and reattachment regions of these flows; and (2) to obtain detailed sets of experimental measurements with which to extend the simple semi-empirical prediction methods to the hypersonic/cooled wall regime where no previous data existed. These studies were conducted at Mach 11 for Reynolds number of up to 40 million in Calspan's 96-Inch <span class="hlt">Shock</span> Tunnel. In the first study we examined the effects of crossflow on the scale and properties of attached and separated region induced over a flat plate at the base of skewed/oblique <span class="hlt">shocks</span>. Analysis of the detailed heat transfer and pressure measurements together with flow visualization demonstrated that, for sweep angles of up to 45 deg, crossflow had little effect on the size or characteristics of the interaction regions. In the second study the swept-<span class="hlt">shock</span> was induced normal to the flat plate boundary <span class="hlt">layer</span> by a <span class="hlt">shock</span> generator mounted perpendicular to the flat plate. Our corner flow measurements demonstrated that, in highly-cooled hypersonic flows, the pressure rise to induce incipient separation is significantly larger than predicted by the semi-empirical methods.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/5975895','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/5975895"><span id="translatedtitle">Turbulent heat transfer in <span class="hlt">parallel</span> flow boundary <span class="hlt">layers</span> with streamwise step changes in surface conditions</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Lindberg, W.R.; Lee, R.C.; Smathers, L.B. )</p> <p>1989-11-01</p> <p>This paper examines the convective heat/mass transfer behavior of a turbulent boundary <span class="hlt">layer</span> with <span class="hlt">parallel</span> streamlines. The most notable example of such flow is an atmospheric boundary <span class="hlt">layer</span> with a steady mean wind in the absence of topography. The classic, two-dimensional problem involves the surface boundary condition of a finite-length step change in temperature/concentration in the streamwise direction of an atmospheric flow. In the literature on geophysical evapotranspiration, this problem is known as Sutton's problem (cf. Sutton, 1934, and Brutsaert, 1984). This flow situation is equally applicable to heat/mass transfer in solar ponds, ground solar collectors, and heated roadways, as examples. The present note revisits the Sutton problem, with the can Driest eddy diffusivity model, and expands the types of boundary conditions that are examined to include surface changes in temperature/concentration and fluxes. The <span class="hlt">parallel</span> streamline condition allows for Graetz-type solutions, with boundary conditions at the surface and in the far flow field. The predicted results are presented as a series of power law correlations of the relevant nondimensional parameters.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20040090527','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20040090527"><span id="translatedtitle"><span class="hlt">Shock-Wave/Boundary-Layer</span> Interactions in Hypersonic Low Density Flows</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Moss, James N.; Olejniczak, Joseph</p> <p>2004-01-01</p> <p>Results of numerical simulations of Mach 10 air flow over a hollow cylinder-flare and a double-cone are presented where viscous effects are significant. The flow phenomena include <span class="hlt">shock-shock</span> and <span class="hlt">shock</span>- boundary-<span class="hlt">layer</span> interactions with accompanying flow separation, recirculation, and reattachment. The purpose of this study is to promote an understanding of the fundamental gas dynamics resulting from such complex interactions and to clarify the requirements for meaningful simulations of such flows when using the direct simulation Monte Carlo (DSMC) method. Particular emphasis is placed on the sensitivity of computed results to grid resolution. Comparisons of the DSMC results for the hollow cylinder-flare (30 deg.) configuration are made with the results of experimental measurements conducted in the ONERA RSCh wind tunnel for heating, pressure, and the extent of separation. Agreement between computations and measurements for various quantities is good except that for pressure. For the same flow conditions, the double- cone geometry (25 deg.- 65 deg.) produces much stronger interactions, and these interactions are investigated numerically using both DSMC and Navier-Stokes codes. For the double-cone computations, a two orders of magnitude variation in free-stream density (with Reynolds numbers from 247 to 24,7 19) is investigated using both computational methods. For this range of flow conditions, the computational results are in qualitative agreement for the extent of separation with the DSMC method always predicting a smaller separation region. Results from the Navier-Stokes calculations suggest that the flow for the highest density double-cone case may be unsteady; however, the DSMC solution does not show evidence of unsteadiness.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20030068449','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20030068449"><span id="translatedtitle">Drag Reduction by Suction of the Boundary <span class="hlt">Layer</span> Separated Behind <span class="hlt">Shock</span> Wave Formation at High Mach Numbers</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Regenscheit, B.</p> <p>1947-01-01</p> <p>With an approach of the velocity of flight of a ship to the velocity of sound, there occurs a considerable increase of the drag. The reason for this must be found in the boundary <span class="hlt">layer</span> separation caused by formation of <span class="hlt">shock</span> waves. It will be endeavored to reduce the drag increase by suction of the boundary <span class="hlt">layer</span>. Experimental results showed that drag increase may be considerably reduced by this method. It was, also, observed that, by suction, the position of <span class="hlt">shock</span> waves can be altered to a considerable extent.</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_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li class="active"><span>12</span></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_13");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_12 --> <div id="page_13" 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_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li class="active"><span>13</span></li> <li><a href="#" onclick='return showDiv("page_13");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="241"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19800050160&hterms=wall+shear+stress&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dwall%2Bshear%2Bstress','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19800050160&hterms=wall+shear+stress&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dwall%2Bshear%2Bstress"><span id="translatedtitle">Interaction between a normal <span class="hlt">shock</span> wave and a turbulent boundary <span class="hlt">layer</span> at high transonic speeds. II - Wall shear stress</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Liou, M. S.; Adamson, T. C., Jr.</p> <p>1980-01-01</p> <p>Asymptotic methods are used to calculate the shear stress at the wall for the interaction between a normal <span class="hlt">shock</span> wave and a turbulent boundary <span class="hlt">layer</span> on a flat plate. A mixing length model is used for the eddy viscosity. The <span class="hlt">shock</span> wave is taken to be strong enough that the sonic line is deep in the boundary <span class="hlt">layer</span> and the upstream influence is thus very small. It is shown that unlike the result found for laminar flow an asymptotic criterion for separation is not found; however, conditions for incipient separation are computed numerically using the derived solution for the shear stress at the wall. Results are compared with available experimental measurements.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009PhDT.......293M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009PhDT.......293M"><span id="translatedtitle">Physics of unsteady cylinder-induced transitional <span class="hlt">shock</span> wave boundary <span class="hlt">layer</span> interactions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Murphree, Zachary Ryan</p> <p></p> <p>The mean flowfield and time-dependent characteristics of a Mach 5 cylinder-induced transitional <span class="hlt">shock-wave/boundary-layer</span> interaction have been studied experimentally. The interactions were generated with a right circular cylinder mounted on a flat plate. The Reynolds number based on distance from the leading edge of the plate to the cylinder leading edge ranged from 4.5 x 106 to 6.1 x 106, and the incoming boundary-<span class="hlt">layer</span> was transitional. The objectives of the study were to: (i) provide a detailed description of the mean flow structure of the interaction, and (ii) characterize the unsteadiness of the interaction based on fluctuating pressure measurements. Mean wall-pressure measurements coupled with planar laser scattering and surface visualization showed that the transitional interaction exhibits characteristics that are essentially a "composite" of an upstream laminar interaction and a downstream turbulent interaction. In the upstream region there is a laminar separation bubble that is characterized by a weak separation <span class="hlt">shock</span>, a pressure plateau, and low relative mass/heat flux. The separated boundary-<span class="hlt">layer</span> reattaches downstream of this bubble, about 4 diameters upstream of the cylinder. This reattached flow is characterized by high relative mass/heat flux, an increase in pressure and a rapidly thickening boundary-<span class="hlt">layer</span>. The flow then separates again in a manner very similar to a low Reynolds number turbulent interaction. Statistical analysis of the pressure histories suggest that the entire interaction stretches and contracts in concert. Power spectral densities of the pressure fluctuations showed unsteadiness throughout the interaction with energy content in one of two frequency bands: one with a sharp peak from 1-2 kHz and the other with a broader peak at 7-10 kHz. The lower frequency is attributed to the interaction motion, whereas the higher frequency is found underneath the reattached boundary-<span class="hlt">layer</span>. Cross-correlations and coherence functions in the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19960054470','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19960054470"><span id="translatedtitle">Transonic <span class="hlt">Shock</span> Oscillations and Wing Flutter Calculated with an Interactive Boundary <span class="hlt">Layer</span> Coupling Method</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Edwards, John W.</p> <p>1996-01-01</p> <p>A viscous-inviscid interactive coupling method is used for the computation of unsteady transonic flows involving separation and reattachment. A lag-entrainment integral boundary <span class="hlt">layer</span> method is used with the transonic small disturbance potential equation in the CAP-TSDV (Computational Aeroelasticity Program - Transonic Small Disturbance) code. Efficient and robust computations of steady and unsteady separated flows, including steady separation bubbles and self-excited <span class="hlt">shock</span>-induced oscillations are presented. The buffet onset boundary for the NACA 0012 airfoil is accurately predicted and shown computationally to be a Hopf bifurcation. <span class="hlt">Shock</span>-induced oscillations are also presented for the 18 percent circular arc airfoil. The oscillation onset boundaries and frequencies are accurately predicted, as is the experimentally observed hysteresis of the oscillations with Mach number. This latter stability boundary is identified as a jump phenomenon. Transonic wing flutter boundaries are also shown for a thin swept wing and for a typical business jet wing, illustrating viscous effects on flutter and the effect of separation onset on the wing response at flutter. Calculations for both wings show limit cycle oscillations at transonic speeds in the vicinity of minimum flutter speed indices.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015ShWav..25..535V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015ShWav..25..535V"><span id="translatedtitle">Control of <span class="hlt">shock</span>-wave boundary <span class="hlt">layer</span> interaction using steady micro-jets</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Verma, S. B.; Manisankar, C.; Akshara, P.</p> <p>2015-09-01</p> <p>An experimental investigation was conducted to control the amplitude of <span class="hlt">shock</span> unsteadiness associated with the interaction induced by a cylindrical protuberance on a flat plate in a Mach 2.18 flow. The control was applied in the form of an array of steady micro air-jets of different configurations with variation in pitch and skew angle of the jets. The effect of air-jet supply pressure on control was also studied. Each of the micro-jet configurations was placed 20 boundary <span class="hlt">layer</span> thicknesses upstream of the leading edge of the cylinder. The overall interaction is seen to get modified for all control configurations and shows a reduction in both separation- and bow-<span class="hlt">shock</span> strengths and in triple-point height. A significant reduction in the peak rms value is also observed in the intermittent region of separation for each case. For pitched jets placed in a zig-zag configuration, good control effectiveness is achieved at control pressures similar to the stagnation pressure of the freestream. At higher control pressures, however, their obstruction component increases and if these jets are not spaced sufficiently far apart, the effectiveness of their control begins to drop due to the beginning of spanwise jet-to-jet interaction. On the other hand, pitching or skewing the jets to reduces the obstruction component considerably which at lower control pressures shows lower effectiveness. But at higher control pressure, the effectiveness of these configurations continues to increase unlike the pitched jets.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013EUCAS...5..247G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013EUCAS...5..247G"><span id="translatedtitle">Numerical analysis of three complex three-dimensional <span class="hlt">shock</span> wave / turbulent boundary <span class="hlt">layer</span> interaction flows</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Grosvenor, A. D.; Zheltovodov, A. A.; Matheson, M. A.; Sailer, L. M.; Krzysztopik, M.; Gutzwiller, D. P.</p> <p>2013-06-01</p> <p>A set of Reynolds-averaged Navier-Stokes (RANS) computations with turbulence closure provided by the Spalart-Allmaras (SA) model have been carried out for prediction of <span class="hlt">shock</span>-induced three-dimensional (3D) turbulent separated flows. The experimental data for different aerodynamic test configurations have been used for assessing credibility of the numerical method employed. Particularly, <span class="hlt">shock</span> wave / turbulent boundary <span class="hlt">layer</span> interactions (SWTBLI) in the vicinity of an asymmetric sharp double-fin (DF) with different (7° and 11°) deflection angles mounted on a flat plate and two conically sharp cylindrical bodies at varying interbody distances and nose cone angles 60° and 40° mounted over a flat plate at freestream Mach number 4, as well as a transonic fan stage operating in the near-stall regime are considered. The gas dynamic structure and topology of 3D separated flows, surface flow patterns, and pressure distributions as well as body aerodynamic force prediction are analyzed. A transonic fan stage operating in the near-stall regime and a possibility of applying flow control is investigated. High Performance Computing was employed to make high resolution computations of these flows possible, and advanced 3D visualization techniques were employed in order to improve understanding of the separating flow phenomena.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19930062842&hterms=upstream&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DTitle%26N%3D0%26No%3D60%26Ntt%3Dupstream','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19930062842&hterms=upstream&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DTitle%26N%3D0%26No%3D60%26Ntt%3Dupstream"><span id="translatedtitle">Control of unsteady <span class="hlt">shock</span>-induced turbulent boundary <span class="hlt">layer</span> separation upstream of blunt fins</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Kleifges, K.; Dolling, D. S.</p> <p>1993-01-01</p> <p>Fluctuating wall pressure measurements have been made on centerline upstream of blunt fins in a Mach 5 turbulent boundary <span class="hlt">layer</span>. Standard time series analysis and conditional sampling algorithms have been used to examine the effects of leading edge sweepback, leading edge shape, and fin root modifications on the fluctuating pressures. Leading edge sweep considerably reduces the mean and rms pressure loading at the fin root, the extent of the region of unsteady separation <span class="hlt">shock</span> motion, and the separation length. The frequency of pressure fluctuations in the intermittent region increases with leading edge sweepback, while the spectral content of pressure fluctuations in the separated region is virtually unchanged by leading edge sweep. A swept hemicylindrically blunted root fillet reduces the centerline upstream influence and intermittent region length by 50 percent, and reduces the mean and rms pressure loading at the fin root by about 75 percent and 95 percent respectively. Experiments using hemicylindrical, wedge shaped and flat leading edges show that while separated flow scales increase with increasing 'bluntness', intermittent region length and root loading decrease, and separation <span class="hlt">shock</span> frequency increases.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19920002551','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19920002551"><span id="translatedtitle">Spectral fitting, <span class="hlt">shock</span> <span class="hlt">layer</span> modeling, and production of nitrogen oxides and excited nitrogen</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Blackwell, H. E.</p> <p>1991-01-01</p> <p>An analysis was made of N2 emission from 8.72 MJ/kg <span class="hlt">shock</span> <span class="hlt">layer</span> at 2.54, 1.91, and 1.27 cm positions and vibrational state distributions, temperatures, and relative electronic state populations was obtained from data sets. Other recorded arc jet N2 and air spectral data were reviewed and NO emission characteristics were studied. A review of operational procedures of the DSMC code was made. Information on other appropriate codes and modifications, including ionization, were made as well as a determination of the applicability of codes reviewed to task requirement. A review was also made of computational procedures used in CFD codes of Li and other codes on JSC computers. An analysis was made of problems associated with integration of specific chemical kinetics applicable to task into CFD codes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19900051345&hterms=Chemical+Equilibria+Earth&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3DChemical%2BEquilibria%2BEarth','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19900051345&hterms=Chemical+Equilibria+Earth&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3DChemical%2BEquilibria%2BEarth"><span id="translatedtitle">Viscous-<span class="hlt">shock-layer</span> solutions with coupled radiation and ablation injection for earth entry</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Gupta, Roop N.; Lee, Kam-Pui; Moos, James N.; Sutton, Kenneth</p> <p>1990-01-01</p> <p>Results are obtained for the forebody of a planetary exploration vehicle entering the earth's atmosphere. A viscous-<span class="hlt">shock-layer</span> analysis is used assuming the flow to be laminar and in chemical equilibrium. Presented results include coupled radiation and ablation injection. This study further includes the effect of different transport and thermodynamic properties and radiation models. A Lewis number of 1.4 appears adequate for the radiation-dominated flows. Five velocities corresponding to different possible trajectory points at an altitude of 70 km have been further analyzed in detail. Sublimation and radiative equilibrium wall temperatures are employed for cases with and without coupled injection, respectively. For the cases analyzed here, the mass injection rates are small. However, the rates could become large if a lower altitude is used for aerobraking and/or the body size is increased. A comparison of the equilibrium results with finite-rate chemistry calculation shows the flowfield to be in chemical equilibrium.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19970006988','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19970006988"><span id="translatedtitle">Skin-Friction Measurements in a 3-D, Supersonic <span class="hlt">Shock-Wave/Boundary-Layer</span> Interaction</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Wideman, J. K.; Brown, J. L.; Miles, J. B.; Ozcan, O.</p> <p>1994-01-01</p> <p>The experimental documentation of a three-dimensional <span class="hlt">shock-wave/boundary-layer</span> interaction in a nominal Mach 3 cylinder, aligned with the free-stream flow, and 20 deg. half-angle conical flare offset 1.27 cm from the cylinder centerline. Surface oil flow, laser light sheet illumination, and schlieren were used to document the flow topology. The data includes surface-pressure and skin-friction measurements. A laser interferometric skin friction data. Included in the skin-friction data are measurements within separated regions and three-dimensional measurements in highly-swept regions. The skin-friction data will be particularly valuable in turbulence modeling and computational fluid dynamics validation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19840008067','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19840008067"><span id="translatedtitle">Investigation to optimize the passive <span class="hlt">shock</span> wave-boundary <span class="hlt">layer</span> control for supercritical airfoil drag reduction</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Nagamatsu, H. T.; Ficarra, R.; Orozco, R.</p> <p>1983-01-01</p> <p>The optimization of passive <span class="hlt">shock</span> wave/boundary <span class="hlt">layer</span> control for supercritical airfoil drag reduction was investigated in a 3 in. x 15.4 in. Transonic Blowdown Wind Tunnel. A 14% thick supercritical airfoil was tested with 0%, 1.42% and 2.8% porosities at Mach numbers of .70 to .83. The 1.42% case incorporated a linear increase in porosity with the flow direction while the 2.8% case was uniform porosity. The static pressure distributions over the airfoil, the wake impact pressure data for determining the profile drag, and the Schlieren photographs for porous surface airfoils are presented and compared with the results for solid-surface airfoils. While the results show that linear 1.42% porosity actually led to a slight increase in drag it was found that the uniform 2.8% porosity can lead to a drag reduction of 46% at M = .81.</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_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li class="active"><span>13</span></li> <li><a href="#" onclick='return showDiv("page_13");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_13 --> <center> <div class="footer-extlink text-muted"><small>Some links on this page may take you to non-federal websites. 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