Simulation of Ejecta Production and Mixing Process of Sn Sample under shock loading

NASA Astrophysics Data System (ADS)

Wang, Pei; Chen, Dawei; Sun, Haiquan; Ma, Dongjun

2017-06-01

Ejection may occur when a strong shock wave release at the free surface of metal material and the ejecta of high-speed particulate matter will be formed and further mixed with the surrounding gas. Ejecta production and its mixing process has been one of the most difficult problems in shock physics remain unresolved, and have many important engineering applications in the imploding compression science. The present paper will introduce a methodology for the theoretical modeling and numerical simulation of the complex ejection and mixing process. The ejecta production is decoupled with the particle mixing process, and the ejecta state can be achieved by the direct numerical simulation for the evolution of initial defect on the metal surface. Then the particle mixing process can be simulated and resolved by a two phase gas-particle model which uses the aforementioned ejecta state as the initial condition. A preliminary ejecta experiment of planar Sn metal Sample has validated the feasibility of the proposed methodology.

Pathway to a Phenocopy: Heat Stress Effects in Early Embryogenesis

PubMed Central

Crews, Sarah M.; McCleery, W. Tyler; Hutson, M. Shane

2015-01-01

Background Heat shocks applied at the onset of gastrulation in early Drosophila embryos frequently lead to phenocopies of U-shaped mutants – having characteristic failures in the late morphogenetic processes of germband retraction and dorsal closure. The pathway from non-specific heat stress to phenocopied abnormalities is unknown. Results Drosophila embryos subjected to 30-min, 38-°C heat shocks at gastrulation appear to recover and restart morphogenesis. Post-heat-shock development appears normal, albeit slower, until a large fraction of embryos develop amnioserosa holes (diameters > 100 μm). These holes are positively correlated with terminal U-shaped phenocopies. They initiate between amnioserosa cells and open over tens of minutes by evading normal wound healing responses. They are not caused by tissue-wide increases in mechanical stress or decreases in cell-cell adhesion, but instead appear to initiate from isolated apoptosis of amnioserosa cells. Conclusions The pathway from heat shock to U-shaped phenocopies involves the opening of one or more large holes in the amnioserosa that compromise its structural integrity and lead to failures in morphogenetic processes that rely on amnioserosa-generated tensile forces. The proposed mechanism by which heat shock leads to hole initiation and expansion is heterochonicity – i.e., disruption of morphogenetic coordination between embryonic and extra-embryonic cell types. PMID:26498920

Method to separate and determine the amount of ejecta produced in a second-shock material-fragmentation event

NASA Astrophysics Data System (ADS)

Buttler, W. T.; Hixson, R. S.; King, N. S. P.; Olson, R. T.; Rigg, P. A.; Zellner, M. B.; Routley, N.; Rimmer, A.

2007-04-01

The authors consider a mathematical method to separate and determine the amount of ejecta produced in a second-shock material-fragmentation process. The technique is theoretical and assumes that a material undergoing a shock release at a vacuum interface ejects particulate material or fragments as the initial shock unloads and reflects at the vacuum-surface interface. In this case it is thought that the reflected shock may reflect again at the source of the shock and return to the vacuum-surface interface and eject another amount of fragments or particulate material.

Designing high speed diagnostics

NASA Astrophysics Data System (ADS)

Veliz Carrillo, Gerardo; Martinez, Adam; Mula, Swathi; Prestridge, Kathy; Extreme Fluids Team Team

2017-11-01

Timing and firing for shock-driven flows is complex because of jitter in the shock tube mechanical drivers. Consequently, experiments require dynamic triggering of diagnostics from pressure transducers. We explain the design process and criteria for setting up re-shock experiments at the Los Alamos Vertical Shock Tube facility, and the requirements for particle image velocimetry and planar laser induced fluorescence measurements necessary for calculating Richtmeyer-Meshkov variable density turbulent statistics. Dynamic triggering of diagnostics allows for further investigation of the development of the Richtemeyer-Meshkov instability at both initial shock and re-shock. Thanks to the Los Alamos National Laboratory for funding our project.

Hot spot formation and chemical reaction initiation in shocked HMX crystals with nanovoids: a large-scale reactive molecular dynamics study.

PubMed

Zhou, Tingting; Lou, Jianfeng; Zhang, Yangeng; Song, Huajie; Huang, Fenglei

2016-07-14

We report million-atom reactive molecular dynamic simulations of shock initiation of β-cyclotetramethylene tetranitramine (β-HMX) single crystals containing nanometer-scale spherical voids. Shock induced void collapse and subsequent hot spot formation as well as chemical reaction initiation are observed which depend on the void size and impact strength. For an impact velocity of 1 km s(-1) and a void radius of 4 nm, the void collapse process includes three stages; the dominant mechanism is the convergence of upstream molecules toward the centerline and the downstream surface of the void forming flowing molecules. Hot spot formation also undergoes three stages, and the principal mechanism is kinetic energy transforming to thermal energy due to the collision of flowing molecules on the downstream surface. The high temperature of the hot spot initiates a local chemical reaction, and the breakage of the N-NO2 bond plays the key role in the initial reaction mechanism. The impact strength and void size have noticeable effects on the shock dynamical process, resulting in a variation of the predominant mechanisms leading to void collapse and hot spot formation. Larger voids or stronger shocks result in more intense hot spots and, thus, more violent chemical reactions, promoting more reaction channels and generating more reaction products in a shorter duration. The reaction products are mainly concentrated in the developed hot spot, indicating that the chemical reactivity of the hmx crystal is greatly enhanced by void collapse. The detailed information derived from this study can aid a thorough understanding of the role of void collapse in hot spot formation and the chemical reaction initiation of explosives.

The effect of stochastic re-acceleration on the energy spectrum of shock-accelerated protons

DOE Office of Scientific and Technical Information (OSTI.GOV)

Afanasiev, Alexandr; Vainio, Rami; Kocharov, Leon

2014-07-20

The energy spectra of particles in gradual solar energetic particle (SEP) events do not always have a power-law form attributed to the diffusive shock acceleration mechanism. In particular, the observed spectra in major SEP events can take the form of a broken (double) power law. In this paper, we study the effect of a process that can modify the power-law spectral form produced by the diffusive shock acceleration: the stochastic re-acceleration of energetic protons by enhanced Alfvénic turbulence in the downstream region of a shock wave. There are arguments suggesting that this process can be important when the shock propagatesmore » in the corona. We consider a coronal magnetic loop traversed by a shock and perform Monte Carlo simulations of interactions of shock-accelerated protons with Alfvén waves in the loop. The wave-particle interactions are treated self-consistently, so the finiteness of the available turbulent energy is taken into account. The initial energy spectrum of particles is taken to be a power law. The simulations reveal that the stochastic re-acceleration leads either to the formation of a spectrum that is described in a wide energy range by a power law (although the resulting power-law index is different from the initial one) or to a broken power-law spectrum. The resulting spectral form is determined by the ratio of the energy density of shock-accelerated protons to the wave energy density in the shock's downstream region.« less

Fast Hydrogen-Air Flames for Turbulence Driven Deflagration to Detonation Transition

NASA Astrophysics Data System (ADS)

Chambers, Jessica; Ahmed, Kareem

2016-11-01

Flame acceleration to Detonation produces several combustion modes as the Deflagration-to-Detonation Transition (DDT) is initiated, including fast deflagration, auto-ignition, and quasi-detonation. Shock flame interactions and turbulence levels in the reactant mixture drive rapid flame expansion, formation of a leading shockwave and post-shock conditions. An experimental study to characterize the developing shock and flame front behavior of propagating premixed hydrogen-air flames in a square channel is presented. To produce each flame regime, turbulence levels and flame propagation velocity are controlled using perforated plates in several configurations within the experimental facility. High speed optical diagnostics including Schlieren and Particle Image Velocimetry are used to capture the flow field. In-flow pressure measurements acquired post-shock, detail the dynamic changes that occur in the compressed gas directly ahead of the propagating flame. Emphasis on characterizing the turbulent post-shock environment of the various flame regimes helps identify the optimum conditions to initiate the DDT process. The study aims to further the understanding of complex physical mechanisms that drive transient flame conditions for detonation initiation. American Chemical Society.

Shock response of 1,3,5-trinitroperhydro-1,3,5-triazine (RDX): The C-N bond scission studied by molecular dynamics simulations

NASA Astrophysics Data System (ADS)

Yuan, Jiao-Nan; Wei, Yong-Kai; Zhang, Xiu-Qing; Chen, Xiang-Rong; Ji, Guang-Fu; Kotni, Meena Kumari; Wei, Dong-Qing

2017-10-01

The shock response has a great influence on the design, synthesis, and application of energetic materials in both industrial and military areas. Therefore, the initial decomposition mechanism of bond scission at the atomistic level of condensed-phase α-RDX under shock loading has been studied based on quantum molecular dynamics simulations in combination with a multi-scale shock technique. First, based on the frontier molecular orbital theory, our calculated result shows that the N-NO2 bond is the weakest bond in the α-RDX molecule in the ground state, which may be the initial bond for pyrolysis. Second, the changes of bonds under shock loading are investigated by the changes of structures, kinetic bond lengths, and Laplacian bond orders during the simulation. Also, the variation of thermodynamic properties with time in shocked α-RDX at 10 km/s along the lattice vector a for a timescale of up to 3.5 ps is presented. By analyzing the detailed structural changes of RDX under shock loading, we find that the shocked RDX crystal undergoes a process of compression and rotation, which leads to the C-N bond initial rupture. The time variation of dynamic bond lengths in a shocked RDX crystal is calculated, and the result indicates that the C-N bond is easier to rupture than other bonds. The Laplacian bond orders are used to predict the molecular reactivity and stability. The values of the calculated bond orders show that the C-N bonds are more sensitive than other bonds under shock loading. In a word, the C-N bond scission has been validated as the initial decomposition in a RDX crystal shocked at 10 km/s. Finally, the bond-length criterion has been used to identify individual molecules in the simulation. The distance thresholds up to which two particles are considered direct neighbors and assigned to the same cluster have been tested. The species and density numbers of the initial decomposition products are collected according to the trajectory.

Experimental particle acceleration by water evaporation induced by shock waves

NASA Astrophysics Data System (ADS)

Scolamacchia, T.; Alatorre Ibarguengoitia, M.; Scheu, B.; Dingwell, D. B.; Cimarelli, C.

2010-12-01

Shock waves are commonly generated during volcanic eruptions. They induce sudden changes in pressure and temperature causing phase changes. Nevertheless, their effects on flowfield properties are not well understood. Here we investigate the role of gas expansion generated by shock wave propagation in the acceleration of ash particles. We used a shock tube facility consisting of a high-pressure (HP) steel autoclave (450 mm long, 28 mm in internal diameter), pressurized with Ar gas, and a low-pressure tank at atmospheric conditions (LP). A copper diaphragm separated the HP autoclave from a 180 mm tube (PVC or acrylic glass) at ambient P, with the same internal diameter of the HP reservoir. Around the tube, a 30 cm-high acrylic glass cylinder, with the same section of the LP tank (40 cm), allowed the observation of the processes occurring downstream from the nozzle throat, and was large enough to act as an unconfined volume in which the initial diffracting shock and gas jet expand. All experiments were performed at Pres/Pamb ratios of 150:1. Two ambient conditions were used: dry air and air saturated with steam. Carbon fibers and glass spheres in a size range between 150 and 210 μm, were placed on a metal wire at the exit of the PVC tube. The sudden decompression of the Ar gas, due to the failure of the diaphragm, generated an initial air shock wave. A high-speed camera recorded the processes between the first 100 μsec and several ms after the diaphragm failure at frame rates ranging between 30,000 and 50,000 fps. In the experiments with ambient air saturated with steam, the high-speed camera allowed to visualize the condensation front associated with the initial air shock; a maximum velocity of 788 m/s was recorded, which decreases to 524 m/s at distance of 0.5 ±0.2 cm, 1.1 ms after the diaphragm rupture. The condensation front preceded the Ar jet front exhausting from the reservoir, by 0.2-0.5 ms. In all experiments particles velocities following the initial condensation front exhibited large accelerations, with velocity varying from few tens of m/s up to 479 (±0.5) m/s, at distances of 1.5 (±0.3) cm and in times of 0.1 ms. This process preceded the appearance of the Ar front. Our first results suggest that the evaporation of moisture induced by compression waves associated with the air shock is able to accelerate particles (ca.100s microns in size) efficiently, at short distances. This process could have broader implications in active volcanic areas where shock waves are generated, for the damage that may follow.

Multiphysics Simulations of Hot-Spot Initiation in Shocked Insensitive High-Explosive

NASA Astrophysics Data System (ADS)

Najjar, Fady; Howard, W. M.; Fried, L. E.

2010-11-01

Solid plastic-bonded high-explosive materials consist of crystals with micron-sized pores embedded. Under mechanical or thermal insults, these voids increase the ease of shock initiation by generating high-temperature regions during their collapse that might lead to ignition. Understanding the mechanisms of hot-spot initiation has significant research interest due to safety, reliability and development of new insensitive munitions. Multi-dimensional high-resolution meso-scale simulations are performed using the multiphysics software, ALE3D, to understand the hot-spot initiation. The Cheetah code is coupled to ALE3D, creating multi-dimensional sparse tables for the HE properties. The reaction rates were obtained from MD Quantum computations. Our current predictions showcase several interesting features regarding hot spot dynamics including the formation of a "secondary" jet. We will discuss the results obtained with hydro-thermo-chemical processes leading to ignition growth for various pore sizes and different shock pressures.

Simulation of Interaction of Strong Shocks with Gas Bubbles using the Direct Simulation Monte Carlo Method

NASA Astrophysics Data System (ADS)

Puranik, Bhalchandra; Watvisave, Deepak; Bhandarkar, Upendra

2016-11-01

The interaction of a shock with a density interface is observed in several technological applications such as supersonic combustion, inertial confinement fusion, and shock-induced fragmentation of kidney and gall-stones. The central physical process in this interaction is the mechanism of the Richtmyer-Meshkov Instability (RMI). The specific situation where the density interface is initially an isolated spherical or cylindrical gas bubble presents a relatively simple geometry that exhibits all the essential RMI processes such as reflected and refracted shocks, secondary instabilities, turbulence and mixing of the species. If the incident shocks are strong, the calorically imperfect nature needs to be modelled. In the present work, we have carried out simulations of the shock-bubble interaction using the DSMC method for such situations. Specifically, an investigation of the shock-bubble interaction with diatomic gases involving rotational and vibrational excitations at high temperatures is performed, and the effects of such high temperature phenomena will be presented.

Using laser-driven flyer plates to study the shock initiation of nanoenergetic materials

NASA Astrophysics Data System (ADS)

Shaw, William; Dlott, Dana

2013-06-01

A tabletop system has been developed to launch aluminum laser-driven flyer plates at speeds up to 4 km/s. The flyer plates are used to initiate a variety of nanoenergetic materials including aluminum/iron oxide particles produced by arrested ball milling, and multi-layer nano-thermites produced by sputtering. The initiation process is probed by a variety of high-speed diagnostics including time-resolved emission spectroscopy. Impact velocity initiation thresholds for different thickness flyer plates, producing different duration shocks, were determined. The durations of the emission bursts and the effects of nanostructure and microstructure on these bursts were used to investigate the fundamental mechanisms of impact initiation.

Simulation of Shock-Shock Interaction in Parsec-Scale Jets

NASA Astrophysics Data System (ADS)

Fromm, Christian M.; Perucho, Manel; Ros, Eduardo; Mimica, Petar; Savolainen, Tuomas; Lobanov, Andrei P.; Zensus, J. Anton

The analysis of the radio light curves of the blazar CTA 102 during its 2006 flare revealed a possible interaction between a standing shock wave and a traveling one. In order to better understand this highly non-linear process, we used a relativistic hydrodynamic code to simulate the high energy interaction and its related emission. The calculated synchrotron emission from these simulations showed an increase in turnover flux density, Sm, and turnover frequency, νm, during the interaction and decrease to its initial values after the passage of the traveling shock wave.

Shock drift acceleration in the presence of waves

NASA Technical Reports Server (NTRS)

Decker, R. B.; Vlahos, L.

1985-01-01

Attention is given to the initial results of a model designed to study the modification of the scatter-free, shock drift acceleration of energetic test particles by wave activity in the vicinity of a quasi-perpendicular, fast-mode MHD shock. It is emphasized that the concept of magnetic moment conservation is a valid approximation only in the perpendicular and nearly perpendicular regimes, when the angle theta-Bn between the shock normal and the upstream magnetic field vector is in the range from 70 deg to 90 deg. The present investigation is concerned with one step in a program which is being developed to combine the shock drift and diffusive processes at a shock of arbitrary theta-Bn.

Survival of carbon grains in shocks

NASA Technical Reports Server (NTRS)

Seab, C. Gregory

1990-01-01

Supernova shocks play a significant part in the life of an interstellar grain. In a typical 10 to the 9th power year lifetime, a grain will be hit by an average of 10 shocks of 100 km s(sup -1) or greater velocity, and even more shocks of lower velocity. Evaluation of the results of this frequent shock processing is complicated by a number of uncertainties, but seems to give about 10 percent destruction of silicate grains and about half that for graphite grains. Because of the frequency of shocking, the mineralogy and sizes of the grain population is predominately determined by shock processing effects, and not by the initial grain nucleation and growth environment. One consequence of the significant role played by interstellar shocks is that a certain fraction (up to 5 percent) of the carbon should be transformed into the diamond phase. Diamond transformation is observed in the laboratory at threshold shock pressures easily obtainable in grain-grain collisions in supernova shocks. Yields for transforming graphite, amorphous carbon, glassy carbon, and other nearly pure carbon solids into diamond are quite high. Impurities up to at least the 10 percent level (for oxygen) are tolerated in the process. The typical size diamond expected from shock transformation agrees well with the observed sizes in the Lewis et al. findings in meteoritic material. Isotropic anomalies already contained in the grain are likely to be retained through the conversion process, while others may be implanted by the shock if the grain is close to the supernova. The meteoritic diamonds are likely to be the results of transformation of carbon grains in grain-grain collisions in supernova shock waves.

Influence of Small Change of Porosity on Shock Initiation of an HMX/TATB/Viton Explosive and Ignition and Growth Modeling

NASA Astrophysics Data System (ADS)

Liu, Yan; Hussain, Tariq; Huang, Fenglei; Duan, Zhuoping

2016-07-01

All solid explosives in practical use are more or less porous. Although it is known that the change in porosity affects the shock sensitivity of solid explosives, the effect of small changes in porosity on the sensitivity needs to be determined for safe and efficient use of explosive materials. In this study, the influence of a small change in porosity on shock initiation and the subsequent detonation growth process of a plastic-bonded explosive PBXC03, composed of 87% cyclotetramethylene-tetranitramine (HMX), 7% triaminotrinitrobenzene (TATB), and 6% Viton by weight, are investigated by shock to detonation transition experiments. Two explosive formulations of PBXC03 having the same initial grain sizes pressed to 98 and 99% of theoretical mass density (1.873 g/cm3) respectively are tested using the in situ manganin piezoresistive pressure gauge technique. Numerical modeling of the experiments is performed using an ignition and growth reactive flow model. Reasonable agreement with the experimental results is obtained by increasing the growth term coefficient in the Lee-Tarver ignition and growth model with porosity. Combining the experimental and simulation results shows that the shock sensitivity increases with porosity for PBXC03 having the same explosive initial grain sizes for the pressures (about 3.1 GPa) applied in the experiments.

Shock Initiation of Secondary Explosives by MicroSlapper

NASA Astrophysics Data System (ADS)

Mendes, Ricardo; Campos, Jose; Plaksin, Igor; Ribeiro, Jose

2001-06-01

Using the well known Exploding Foil Initiator (EFI) also called slapper detonator the shock to Detonation Wave (DW) transition in a low dense secondary explosive like PETN and RDX is presented in this study. The EFI formed by a capacitor with capacity up to 0.2μF charged until 3kV was used to burst copper bridges with 0.3x0.3mm and 0.4x0.3mm with 5μm of thickness, and to accelerate Kapton flyer plates with 25μm of thickness until 5mm/μs. The process of Shock to Detonation Transition (SDT) in explosive samples with 5mm of diameter by 10mm of height was characterized by an optical method based on 64 optical fibbers ribbon (250mm of diameter each fibber) connected to a fast electronic streak camera. The obtained results, (x,t) diagrams, with 1ns resolution, show continuously the shock to detonation transition regime and allowed the evaluation of the detonation velocity and the detonation wave front curvature. In that regime DW propagation presents the oscillations in detonation velocity. The results also show the influence of the flyer plate velocity and the initial density of the explosive sample in the process of SDT and front oscillations.

Initiation of Detonation in Multiple Shock-Compressed Liquid Explosives

NASA Astrophysics Data System (ADS)

Yoshinaka, A. C.; Zhang, F.; Petel, O. E.; Higgins, A. J.

2006-07-01

Initiation and resulting propagation of detonation via multiple shock reverberations between two high impedance plates has been investigated in amine-sensitized nitromethane. Experiments were designed so that the first reflected shock strength was below the critical value for initiation found previously. Luminosity combined with a distinct pressure hump indicated onset of reaction and successful initiation after double or triple shock reflection off the bottom plate. Final temperature estimates for double or triple shock reflection immediately before initiation lie between 700-720 K, consistent with those found previously for both incident and singly reflected shock initiation.

Dynamic calibration of fast-response probes in low-pressure shock tubes

NASA Astrophysics Data System (ADS)

Persico, G.; Gaetani, P.; Guardone, A.

2005-09-01

Shock tube flows resulting from the incomplete burst of the diaphragm are investigated in connection with the dynamic calibration of fast-response pressure probes. As a result of the partial opening of the diaphragm, pressure disturbances are observed past the shock wave and the measured total pressure profile deviates from the envisaged step signal required by the calibration process. Pressure oscillations are generated as the initially normal shock wave diffracts from the diaphragm's orifice and reflects on the shock tube walls, with the lowest local frequency roughly equal to the ratio of the sound speed in the perturbed region to the shock tube diameter. The energy integral of the perturbations decreases with increasing distance from the diaphragm, as the diffracted leading shock and downwind reflections coalesce into a single normal shock. A procedure is proposed to calibrate fast-response pressure probes downwind of a partially opened shock tube diaphragm.

Stress Proteins and Initiation of Immune Response: Chaperokine activity of Hsp72

PubMed Central

Asea, Alexzander

2006-01-01

From its original description as solely an intracellular molecular chaperone, heat shock proteins have now been shown to function as initiators of the host's immune response. Although the exact mechanism by which intracellular heat shock proteins leave cells is still incompletely understood, recent work from several labs suggest that heat shock proteins are released by both passive (necrotic) and active (physiological) mechanisms. Binding to specific surface receptors is a prerequisite for the initiation of an immune response. To date, several cell surface proteins have been described as the receptor for seventy kilo-Dalton heat shock protein (Hsp70) including Toll-like receptors 2 and 4 with their cofactor CD14, the scavenger receptor CD36, the low-density lipoprotein receptor-related protein CD91, the C-type lectin receptor LOX-1, and another member of the scavenger super-family SR-A plus the co-stimulatory molecule, CD40. Binding of Hsp70 to these surface receptors specifically activates intracellular signaling cascades, which in turn exert immunoregulatory effector functions; a process known as the chaperokine activity of Hsp70. This review will highlight recent advances in understanding the mechanism by which Hsp70 initiates the host's immune response. PMID:16385842

Stress proteins and initiation of immune response: chaperokine activity of hsp72.

PubMed

Asea, Alexzander

2005-01-01

From its original description as solely an intracellular molecular chaperone, heat shock proteins have now been shown to function as initiators of the host's immune response. Although the exact mechanism by which intracellular heat shock proteins leave cells is still incompletely understood, recent work from several labs suggest that heat shock proteins are released by both passive (necrotic) and active (physiological) mechanisms. Binding to specific surface receptors is a prerequisite for the initiation of an immune response. To date, several cell surface proteins have been described as the receptor for seventy kilo-Dalton heat shock protein (Hsp70) including Toll-like receptors 2 and 4 with their cofactor CD14, the scavenger receptor CD36, the low-density lipoprotein receptor-related protein CD91, the C-type lectin receptor LOX-1, and another member of the scavenger super-family SR-A plus the co-stimulatory molecule, CD40. Binding of Hsp70 to these surface receptors specifically activates intracellular signaling cascades, which in turn exert immunoregulatory effector functions; a process known as the chaperokine activity of Hsp70. This review will highlight recent advances in understanding the mechanism by which Hsp70 initiates the host's immune response.

Re-forming supercritical quasi-parallel shocks. II - Mechanism for wave generation and front re-formation

NASA Technical Reports Server (NTRS)

Winske, D.; Thomas, V. A.; Omidi, N.; Quest, K. B.

1990-01-01

This paper continues the study of Thomas et al. (1990) in which hybrid simulations of quasi-parallel shocks were performed in one and two spatial dimensions. To identify the wave generation processes, the electromagnetic structure of the shock is examined by performing a number of one-dimensional hybrid simulations of quasi-parallel shocks 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.

Collisionless shock formation, spontaneous electromagnetic fluctuations, and streaming instabilities

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bret, A.; Instituto de Investigaciones Energeticas y Aplicaciones Industriales, Campus Universitario de Ciudad Real, 13071 Ciudad Real; Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, MS-51 Cambridge, Massachusetts 02138

2013-04-15

Collisionless shocks are ubiquitous in astrophysics and in the lab. Recent numerical simulations and experiments have shown how they can arise from the encounter of two collisionless plasma shells. When the shells interpenetrate, the overlapping region turns unstable, triggering the shock formation. As a first step towards a microscopic understanding of the process, we analyze here in detail the initial instability phase. On the one hand, 2D relativistic Particle-In-Cell simulations are performed where two symmetric initially cold pair plasmas collide. On the other hand, the instabilities at work are analyzed, as well as the field at saturation and the seedmore » field which gets amplified. For mildly relativistic motions and onward, Weibel modes govern the linear phase. We derive an expression for the duration of the linear phase in good agreement with the simulations. This saturation time constitutes indeed a lower-bound for the shock formation time.« less

Impact Processes in the Solar System

NASA Technical Reports Server (NTRS)

Ahrens, Thomas J.

2004-01-01

The three main topics of this program as described initially in our May 2003 proposal are: 1) Shock-induced damage and attenuation in planetary materials. 2 ) Shock-induced melting and phase changes. 3) Impact-induced volatilization and vapor speciation of planetary materials Topic 4 has been the subject of a continuing investigation since approximately 1990. On Topic 5, we have a paper in preparation and have submitted a proposal to Astrobiology. 4) Responses of planetary atmospheres to giant impact, 5) Effects of impact-induced shock waves on microbial life

Reactive atomistic simulations of shock-induced initiation processes in mixtures of ammonium nitrate and fuel oil

NASA Astrophysics Data System (ADS)

Thompson, Aidan P.; Shan, Tzu-Ray

2014-05-01

Ammonium nitrate mixed with fuel oil (ANFO) is a commonly used blasting agent. In this paper we investigated the shock properties of pure ammonium nitrate (AN) and two different mixtures of ammonium nitrate and n-dodecane by characterizing their Hugoniot states. We simulated shock compression of pure AN and ANFO mixtures using the Multi-scale Shock Technique, and observed differences in chemical reaction. We also performed a large-scale explicit sub-threshold shock of AN crystal with a 10 nm void filled with 4.4 wt% of n-dodecane. We observed the formation of hotspots and enhanced reactivity at the interface region between AN and n-dodecane molecules.

Calculation of H2-He Flow with Nonequilibrium Ionization and Radiation: an Interim Report

NASA Technical Reports Server (NTRS)

Furudate, Michiko; Chang, Keun-Shik

2005-01-01

The nonequilibrium ionization process in hydrogen-helium mixture behind a strong shock wave is studied numerically using the detailed ionization rate model developed recently by Park which accounts for emission and absorption of Lyman lines. The study finds that, once the avalanche ionization is started, the Lyman line is self-absorbed. The intensity variation of the radiation at 5145 Angstroms found by Leibowitz in a shock tube experiment can be numerically reproduced by assuming that ionization behind the shock wave prior to the onset of avalanche ionization is 1.3%. Because 1.3% initial ionization is highly unlikely, Leibowitz s experimental data is deemed questionable. By varying the initial electron density value in the calculation, the calculated ionization equilibration time is shown to increase approximately as inverse square-root of the initial electron density value. The true ionization equilibration time is most likely much longer than the value found by Leibowitz.

An electromagnetic railgun accelerator: a generator of strong shock waves in channels

NASA Astrophysics Data System (ADS)

Bobashev, S. V.; Zhukov, B. G.; Kurakin, R. O.; Ponyaev, S. A.; Reznikov, B. I.

2014-11-01

Processes that accompany the generation of strong shock waves during the acceleration of a free plasma piston (PP) in the electromagnetic railgun channel have been experimentally studied. The formation of shock waves in the railgun channel and the motion of a shock-wave-compressed layer proceed (in contrast to the case of a classical shock tube) in a rather strong electric field (up to 300 V/cm). The experiments were performed at the initial gas pressures in the channel ranging from 25 to 500 Torr. At 25 Torr, the shock-wave Mach numbers reached 32 in argon and 16 in helium. At high concentrations of charged particles behind the shock wave, the electric field causes the passage of a part of the discharge current through the volume of the shock-wave-compressed layer, which induces intense glow comparable with that of the PP glow.

Atomic-level deformation of CuxZr100-x metallic glasses under shock loading

NASA Astrophysics Data System (ADS)

Demaske, Brian J.; Wen, Peng; Phillpot, Simon R.; Spearot, Douglas E.

2018-06-01

Plastic deformation mechanisms in CuxZr100-x bulk metallic glasses (MGs) subjected to shock are investigated using molecular dynamics simulations. MGs with Cu compositions between 30 and 70 at. % subjected to shock waves generated via piston velocities that range from 0.125 to 2.0 km/s are considered. In agreement with prior studies, plastic deformation is initiated via formation of localized regions of high von Mises shear strain, known as shear transformation zones (STZs). At low impact velocities, but above the Hugoniot elastic limit, STZ nucleation is dispersed behind the shock front. As impact velocity is increased, STZ nucleation becomes more homogeneous, eventually leading to shock-induced melting, which is identified in this work via high atomic diffusivity. The shear stress necessary to initiate plastic deformation within the shock front is independent of composition at shock intensities near the elastic limit but increases with increasing Cu content at high shock intensities. By contrast, both the flow stress in the plastically deformed MG and the critical shock pressure associated with melting behind the shock front are found to increase with increasing Cu content over the entire range of impact velocities. The evolution of the short-range order in the MG samples during shock wave propagation is analyzed using a polydisperse Voronoi tessellation method. Cu-centered polyhedra with full icosahedral symmetry are found to be most resistant to change under shock loading independent of the MG composition. A saturation is observed in the involvement of select Cu-centered polyhedra in the plastic deformation processes at a piston velocity around 0.75 km/s.

Observation of dust acoustic shock wave in a strongly coupled dusty plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sharma, Sumita K., E-mail: sumita-sharma82@yahoo.com; Boruah, A.; Nakamura, Y.

2016-05-15

Dust acoustic shock wave is observed in a strongly coupled laboratory dusty plasma. A supersonic flow of charged microparticles is allowed to perturb a stationary dust fluid to excite dust acoustic shock wave. The evolution process beginning with steepening of initial wave front and then formation of a stable shock structure is similar to the numerical results of the Korteweg-de Vries-Burgers equation. The measured Mach number of the observed shock wave agrees with the theoretical results. Reduction of shock amplitude at large distances is also observed due to the dust neutral collision and viscosity effects. The dispersion relation and themore » spatial damping of a linear dust acoustic wave are also measured and compared with the relevant theory.« less

Design of Gages for Direct Skin Friction Measurements in Complex Turbulent Flows with Shock Impingement Compensation

DTIC Science & Technology

2007-06-07

100 kW/m2 for 0.1 s. Along with the material change, an oil leak problem required a geometric change. Initially, we considered TIG welding or...shear and moment, is addressed through the design, development, and testing of the CF1 and CF2 gages. Chapter 3 presents the evolutionary process ...a shock. Chapter 4 examines the performance of each gage to the nominal load conditions. Through this process , objective 2 is met. The best

Induction of heat-shock response and alterations of protein phosphorylation by a novel topoisomerase II inhibitor, withangulatin A, in 9L rat brain tumor cells.

PubMed

Lee, W C; Lin, K Y; Chen, C M; Chen, Z T; Liu, H J; Lai, Y K

1991-10-01

Withangulatin A is a newly identified in vitro topoisomerase II inhibitor isolated from the Chinese antitumor herb Physalis angulata. In vivo, it was found to be cytotoxic, capable of suppressing general protein synthesis and of inducing the synthesis of a small set of proteins including those generated by heat-shock treatment. The 70 kDa protein generated by withangulatin A was unequivocally identified as the heat-shock protein 70 (HSP70) since both proteins migrated to the same position on two-dimensional polyacrylamide gels, could be recognized by a monoclonal antibody to human HSP70, and exhibited identical peptide maps. The induction of protein synthesis by withangulatin A was regulated at the transcriptional level since it was aborted in cells pre-treated with actinomycin D. However, the initiation of this process did not require de novo protein synthesis since it was not affected by cycloheximide. Other cellular effect of withangulatin A was alterations of protein phosphorylation including an enhancement of phosphorylation of a 65 kDa protein which was also detected in the heat-shocked cells. Moreover, this process was observed within 7.5 min after the initial heat treatment which is much faster than the onset of HSP synthesis. Therefore, increased phosphorylation of the 65 kDa protein may represent one of the earliest signals generated by both heat-shock and withangluatin A and may be involved in the upstream regulation of heat-shock response in cells.

Computational Study of 3-D Hot-Spot Initiation in Shocked Insensitive High-Explosive

NASA Astrophysics Data System (ADS)

Najjar, F. M.; Howard, W. M.; Fried, L. E.

2011-06-01

High explosive shock sensitivity is controlled by a combination of mechanical response, thermal properties, and chemical properties. The interplay of these physical phenomena in realistic condensed energetic materials is currently lacking. A multiscale computational framework is developed investigating hot spot (void) ignition in a single crystal of an insensitive HE, TATB. Atomistic MD simulations are performed to provide the key chemical reactions and these reaction rates are used in 3-D multiphysics simulations. The multiphysics code, ALE3D, is linked to the chemistry software, Cheetah, and a three-way coupled approach is pursued including hydrodynamics, thermal and chemical analyses. A single spherical air bubble is embedded in the insensitive HE and its collapse due to shock initiation is evolved numerically in time; while the ignition processes due chemical reactions are studied. Our current predictions showcase several interesting features regarding hot spot dynamics including the formation of a ``secondary'' jet. Results obtained with hydro-thermo-chemical processes leading to ignition growth will be discussed for various pore sizes and different shock pressures. LLNL-ABS-471438. This work performed under the auspices of the U.S. Department of Energy by LLNL under Contract DE-AC52-07NA27344.

Electron injection by whistler waves in non-relativistic shocks

NASA Astrophysics Data System (ADS)

Riquelme, Mario A.; Spitkovsky, Anatoly

2012-04-01

Radio and X-ray observations of shocks in young supernova remnants (SNRs) reveal electron acceleration to non-thermal, ultra-relativistic energies (~ 10-100 TeV). This acceleration is usually assumed to happen via the diffusive shock acceleration (DSA) mechanism. However, the way in which electrons are initially energized or 'injected' into this acceleration process is an open question and the main focus of this work. We present our study of electron acceleration in nonrelativistic shocks using 2D and 3D particle-in-cell (PIC) plasma simulations. Our simulations show that significant non-thermal acceleration happens due to the growth of oblique whistler waves in the foot of quasi-perpendicular shocks. The obtained electron energy distributions show power law tails with spectral indices up to α ~ 3-4. Also, the maximum energies of the accelerated particles are consistent with the electron Larmor radii being comparable to that of the ions, indicating potential injection into the subsequent DSA process. This injection mechanism requires the shock waves to have fairly low Alfvénic Mach numbers, MA <20, which is consistent with the theoretical conditions for the growth of whistler waves in the shock foot (MA <(mi/me)1/2). Thus, if this mechanism is the only robust electron injection process at work in SNR shocks, then SNRs that display non-thermal emission must have significantly amplified upstream magnetic fields. Such field amplification is likely achieved by accelerated ions in these environments, so electron and ion acceleration in SNR shocks must be interconnected.

Ultrafast Shock Compression Hugoniot Data of beta-CL-20 and TATB Thin Films

NASA Astrophysics Data System (ADS)

Zaug, Joseph; Armstrong, Michael; Grivickas, Paulius; Tappan, Alexander; Kohl, Ian; Rodriguez, Mark; Knepper, Robert; Crowhurst, Jonathan; Stavrou, Elissaios; Bastea, Sorin

2017-06-01

The shock induced initiation threshold of two energetic materials, CL-20 and TATB are remarkably different; CL-20 is a relatively shock sensitive energetic material and TATB is considered an insensitive high explosive (IHE). Here we report ultrafast laser-based shockwave hydrodynamic data on the 100 ps timescale with 10 ps time resolution to further develop density dependent unreacted shock Hugoniot equations of state (UEOS) and to elucidate ultrafast timescale shock initiation processes for these two vastly different HEs. Thin film samples were made by vacuum thermal evaporation of the explosive on a deposited aluminum ablator layer. The deposited explosives were characterized by scanning electron microscopy, surface profilometry, and x-ray diffraction. Our preliminary UEOS results (up range of 1.3 - 1.8 km/s) from shock compressed beta-CL-20 agree reasonably well with extrapolated pseudo-velocities computed from epsilon-CL-20 isothermal diamond-anvil cell EOS measurements. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract No. DE-AC52-07NA27344. Sandia National Laboratories is a multi-mission laboratory managed and operated by Sandia Corporati.

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

NASA Technical Reports Server (NTRS)

Jachimowski, Casimir J.

1992-01-01

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

1D GAS-DYNAMIC SIMULATION OF SHOCK-WAVE PROCESSES VIA INTERNET

DOE Office of Scientific and Technical Information (OSTI.GOV)

Khishchenko, K. V.; Levashov, P. R.; Povarnitsyn, M. E.

2009-12-28

We present a Web-interface for 1D simulation of different shock-wave experiments. The choosing of initial parameters, the modeling itself and output data treatment can be made directly via the Internet. The interface is based upon the expert system on shock-wave data and equations of state and contains both the Eulerian and Lagrangian Godunov hydrocodes. The availability of equations of state for a broad set of substances makes this system a useful tool for planning and interpretation of shock-wave experiments. As an example of simulation with the system, results of modeling of multistep shock loading of potassium between polytetrafluoroethylene and stainlessmore » steel plates are presented in comparison with experimental data from Shakhray et al.(2005).« less

The structure of steady shock waves in porous metals

NASA Astrophysics Data System (ADS)

Czarnota, Christophe; Molinari, Alain; Mercier, Sébastien

2017-10-01

The paper aims at developing an understanding of steady shock wave propagation in a ductile metallic material containing voids. Porosity is assumed to be less than 0.3 and voids are not connected (foams are not considered). As the shock wave is traveling in the porous medium, the voids are facing a rapid collapse. During this dynamic compaction process, material particles are subjected to very high acceleration in the vicinity of voids, thus generating acceleration forces at the microscale that influence the overall response of the porous material. Analyzing how stationary shocks are influenced by these micro-inertia effects is the main goal of this work. The focus is essentially on the shock structure, ignoring oscillatory motion of pores prevailing at the tail of the shock wave. Following the constitutive framework developed by Molinari and Ravichandran (2004) for the analysis of steady shock waves in dense metals, an analytical approach of steady state propagation of plastic shocks in porous metals is proposed. The initial void size appears as a characteristic internal length that scales the overall dynamic response, thereby contributing to the structuring of the shock front. This key feature is not captured by standard damage models where the porosity stands for the single damage parameter with no contribution of the void size. The results obtained in this work provide a new insight in the fundamental understanding of shock waves in porous media. In particular, a new scaling law relating the shock width to the initial void radius is obtained when micro-inertia effects are significant.

Dynamic Electromechanical Characterization of the Ferroelectric Ceramic PZT 95/5

NASA Astrophysics Data System (ADS)

Setchell, R. E.; Chhabildas, L. C.; Furnish, M. D.; Montgomery, S. T.; Holman, G. T.

1997-07-01

Shock-induced depoling of the ferroelectric ceramic PZT 95/5 has been utilized in a number of pulsed power applications. The dynamic behavior of the poled ceramic is complex, with nonlinear coupling between mechanical and electrical variables. Recent efforts to improve numerical simulations of this process have been limited by the scarcity of relevant experimental studies within the last twenty years. Consequently, we have initiated an extensive experimental study of the dynamic electromechanical behavior of this material. Samples of the poled ceramic are shocked to axial stresses from 0.5 to 5 GPa in planar impact experiments and observed with laser interferometry (VISAR) to obtain transmitted wave profiles. Current generation due to shock-induced depoling is observed using different external loads to vary electric field strengths within the samples. Experimental configurations either have the remanent polarization parallel to the direction of shock motion (axially poled) or perpendicular (normally poled). Initial experiments on unpoled samples utilized PVDF stress gauges as well as VISAR, and extended prior data on shock loading and release behavior. (Supported by the U. S. Department of Energy under contract DE-AC04-94AL85000). abstract.

Dissociative Functions in the Normal Mourning Process.

ERIC Educational Resources Information Center

Kauffman, Jeffrey

1994-01-01

Sees dissociative functions in mourning process as occurring in conjunction with integrative trends. Considers initial shock reaction in mourning as model of normal dissociation in mourning process. Dissociation is understood to be related to traumatic significance of death in human consciousness. Discerns four psychological categories of…

Molecule formation and infrared emission in fast interstellar shocks. I Physical processes

NASA Technical Reports Server (NTRS)

Hollenbach, D.; Mckee, C. F.

1979-01-01

The paper analyzes the structure of fast shocks incident upon interstellar gas of ambient density from 10 to the 7th per cu cm, while focusing on the problems of formation and destruction of molecules and infrared emission in the cooling, neutral post shock gas. It is noted that such fast shocks initially dissociate almost all preexisting molecules. Discussion covers the physical processes which determine the post shock structure between 10 to the 4 and 10 to the 2 K. It is shown that the chemistry of important molecular coolants H2, CO, OH, and H2O, as well as HD and CH, is reduced to a relatively small set of gas phase and grain surface reactions. Also, the chemistry follows the slow conversion of atomic hydrogen into H2, which primarily occurs on grain surfaces. The dependence of this H2 formation rate on grain and gas temperatures is examined and the survival of grains behind fast shocks is discussed. Post shock heating and cooling rates are calculated and an appropriate, analytic, universal cooling function is developed for molecules other than hydrogen which includes opacities from both the dust and the lines.

Simulations of the Richtmyer-Meshkov Instability in a two-shock vertical shock tube

NASA Astrophysics Data System (ADS)

Ferguson, Kevin; Olson, Britton; Jacobs, Jeffrey

2017-11-01

Simulations of the Richtmyer-Meshkov Instability (RMI) in a new two-shock vertical shock tube configuration are presented. The simulations are performed using the ARES code at Lawrence-Livermore National Laboratory (LLNL). Two M=1.2 shock waves travel in opposing directions and impact an initially stationary interface formed by sulfur hexaflouride (SF6) and air. The delay between the two shocks is controlled to achieve a prescribed temporal separation in shock wave arrival time. Initial interface perturbations and diffusion profiles are generated in keeping with previously gathered experimental data. The effect of varying the inter-shock delay and initial perturbation structure on instability growth and mixing parameters is examined. Information on the design, construction, and testing of a new two-shock vertical shock tube are also presented.

Numerical modeling of the destruction of steel plates with a gradient substrate

NASA Astrophysics Data System (ADS)

Orlov, M. Yu.; Glazyrin, V. P.; Orlov, Yu. N.

2017-10-01

The paper presents the results of numerical simulation of the shock loading process of steel barriers with a gradient substrate. In an elastic plastic axisymmetric statement, a shock is simulated along the normal in the range of initial velocities up to 300 m / s. A range of initial velocities was revealed, in which the presence of a substrate "saved" the obstacle from spallation. New tasks were announced to deepen scientific knowledge about the behavior of unidirectional gradient barriers at impact. The results of calculations are obtained in the form of graphs, calculated configurations of the "impact - barrier" and tables.

Atomistic simulation of orientation dependence in shock-induced initiation of pentaerythritol tetranitrate.

PubMed

Shan, Tzu-Ray; Wixom, Ryan R; Mattsson, Ann E; Thompson, Aidan P

2013-01-24

The dependence of the reaction initiation mechanism of pentaerythritol tetranitrate (PETN) on shock orientation and shock strength is investigated with molecular dynamics simulations using a reactive force field and the multiscale shock technique. In the simulations, a single crystal of PETN is shocked along the [110], [001], and [100] orientations with shock velocities in the range 3-10 km/s. Reactions occur with shock velocities of 6 km/s or stronger, and reactions initiate through the dissociation of nitro and nitrate groups from the PETN molecules. The most sensitive orientation is [110], while [100] is the most insensitive. For the [001] orientation, PETN decomposition via nitro group dissociation is the dominant reaction initiation mechanism, while for the [110] and [100] orientations the decomposition is via mixed nitro and nitrate group dissociation. For shock along the [001] orientation, we find that CO-NO(2) bonds initially acquire more kinetic energy, facilitating nitro dissociation. For the other two orientations, C-ONO(2) bonds acquire more kinetic energy, facilitating nitrate group dissociation.

Explosively Driven Shock Induced Damage in OFHC Copper

DOE Office of Scientific and Technical Information (OSTI.GOV)

Koller, D. D.; Hixson, R. S.; Gray, G. T. III

OFHC Cu samples were subjected to shock loading using plane wave HE lenses to produce a uniaxial Taylor wave profile (shock followed by immediate release). Upon arrival of the shock wave at the free surface of the sample, the wave is reflected and propagates back into the sample as a release wave. It is the interaction of initial and reflected release waves that place the material in a localized state of tension which can ultimately result in damage and possibly complete failure of the material. The peak tensile stress and its location in the material are determined by the wavemore » shape. Damage evolution processes and localized behavior are discussed based on results from time-resolved free surface velocity (VISAR) interferometry and post shock metallurgical analysis of the soft recovered samples.« less

Dust in Supernovae and Supernova Remnants II: Processing and Survival

NASA Astrophysics Data System (ADS)

Micelotta, E. R.; Matsuura, M.; Sarangi, A.

2018-03-01

Observations have recently shown that supernovae are efficient dust factories, as predicted for a long time by theoretical models. The rapid evolution of their stellar progenitors combined with their efficiency in precipitating refractory elements from the gas phase into dust grains make supernovae the major potential suppliers of dust in the early Universe, where more conventional sources like Asymptotic Giant Branch (AGB) stars did not have time to evolve. However, dust yields inferred from observations of young supernovae or derived from models do not reflect the net amount of supernova-condensed dust able to be expelled from the remnants and reach the interstellar medium. The cavity where the dust is formed and initially resides is crossed by the high velocity reverse shock which is generated by the pressure of the circumstellar material shocked by the expanding supernova blast wave. Depending on grain composition and initial size, processing by the reverse shock may lead to substantial dust erosion and even complete destruction. The goal of this review is to present the state of the art about processing and survival of dust inside supernova remnants, in terms of theoretical modelling and comparison to observations.

Anisotropic responses and initial decomposition of condensed-phase β-HMX under shock loadings via molecular dynamics simulations in conjunction with multiscale shock technique.

PubMed

Ge, Ni-Na; Wei, Yong-Kai; Song, Zhen-Fei; Chen, Xiang-Rong; Ji, Guang-Fu; Zhao, Feng; Wei, Dong-Qing

2014-07-24

Molecular dynamics simulations in conjunction with multiscale shock technique (MSST) are performed to study the initial chemical processes and the anisotropy of shock sensitivity of the condensed-phase HMX under shock loadings applied along the a, b, and c lattice vectors. A self-consistent charge density-functional tight-binding (SCC-DFTB) method was employed. Our results show that there is a difference between lattice vector a (or c) and lattice vector b in the response to a shock wave velocity of 11 km/s, which is investigated through reaction temperature and relative sliding rate between adjacent slipping planes. The response along lattice vectors a and c are similar to each other, whose reaction temperature is up to 7000 K, but quite different along lattice vector b, whose reaction temperature is only up to 4000 K. When compared with shock wave propagation along the lattice vectors a (18 Å/ps) and c (21 Å/ps), the relative sliding rate between adjacent slipping planes along lattice vector b is only 0.2 Å/ps. Thus, the small relative sliding rate between adjacent slipping planes results in the temperature and energy under shock loading increasing at a slower rate, which is the main reason leading to less sensitivity under shock wave compression along lattice vector b. In addition, the C-H bond dissociation is the primary pathway for HMX decomposition in early stages under high shock loading from various directions. Compared with the observation for shock velocities V(imp) = 10 and 11 km/s, the homolytic cleavage of N-NO2 bond was obviously suppressed with increasing pressure.

Multi-parametric studies of electrically-driven flyer plates

NASA Astrophysics Data System (ADS)

Neal, William; Bowden, Michael; Explosive Trains; Devices Collaboration

2015-06-01

Exploding foil initiator (EFI) detonators function by the acceleration of a flyer plate, by the electrical explosion of a metallic bridge, into an explosive pellet. The length, and therefore time, scales of this shock initation process is dominated by the magnitude and duration of the imparted shock pulse. To predict the dynamics of this initiation, it is critical to further understand the velocity, shape and thickness of this flyer plate. This study uses multi-parametric diagnostics to investigate the geometry and velocity of the flyer plate upon impact including the imparted electrical energy: photon Doppler velocimetry (PDV), dual axis imaging, time-resolved impact imaging, voltage and current. The investigation challenges the validity of traditional assumptions about the state of the flyer plate at impact and discusses the improved understanding of the process.

Detonative propagation and accelerative expansion of the Crab Nebula shock front.

PubMed

Gao, Yang; Law, Chung K

2011-10-21

The accelerative expansion of the Crab Nebula's outer envelope is a mystery in dynamics, as a conventional expanding blast wave decelerates when bumping into the surrounding interstellar medium. Here we show that the strong relativistic pulsar wind bumping into its surrounding nebula induces energy-generating processes and initiates a detonation wave that propagates outward to form the current outer edge, namely, the shock front, of the nebula. The resulting detonation wave, with a reactive downstream, then provides the needed power to maintain propagation of the shock front. Furthermore, relaxation of the curvature-induced reduction of the propagation velocity from the initial state of formation to the asymptotic, planar state of Chapman-Jouguet propagation explains the observed accelerative expansion. Potential richness in incorporating reactive fronts in the description of various astronomical phenomena is expected. © 2011 American Physical Society

A Study of SDT in an Ammonium Nitrate (NH4 NO3) Based Granular Explosive

NASA Astrophysics Data System (ADS)

Burns, Malcolm; Taylor, Peter

2007-06-01

In order to study the SDT process in a granular non ideal explosive (NIE) an experimental technique has been developed that allows the granular explosive to be shock initiated at a well controlled ``tap density''. The granular NIE was contained in a PMMA cone and a planar shock was delivered to the explosive through buffer plates of varying material. A combination of piezoelectric probes, ionization pins, PVDF stress gauges and a high speed framing camera were used to measure the input shock pressure and shock and detonation wave positions in the explosive. Four trials were performed to characterize the run to detonation distance versus pressure relationship (Pop plot) of the granular NH4 NO3 explosive. Input pressures ranged from close to the 4GPa predicted CJ pressure of the granular explosive down to 1.4 GPa, giving run distances up to 14mm for the lowest pressure. The data indicates a steady acceleration of the input shock to the detonation velocity, implying significant reaction growth at the shock front. This is in contrast to the behaviour of most high density pressed PBXs which show little growth in shock front velocity before transit to detonation. The experimentally observed initiation behaviour is compared to that predicted by a simple JWL++ reactive burn model for the granular NH4 NO3 explosive which has been fitted to other detonics experiments on this material.

Optical diagnostics of turbulent mixing in explosively-driven shock tube

NASA Astrophysics Data System (ADS)

Anderson, James; Hargather, Michael

2016-11-01

Explosively-driven shock tube experiments were performed to investigate the turbulent mixing of explosive product gases and ambient air. A small detonator initiated Al / I2O5 thermite, which produced a shock wave and expanding product gases. Schlieren and imaging spectroscopy were applied simultaneously along a common optical path to identify correlations between turbulent structures and spatially-resolved absorbance. The schlieren imaging identifies flow features including shock waves and turbulent structures while the imaging spectroscopy identifies regions of iodine gas presence in the product gases. Pressure transducers located before and after the optical diagnostic section measure time-resolved pressure. Shock speed is measured from tracking the leading edge of the shockwave in the schlieren images and from the pressure transducers. The turbulent mixing characteristics were determined using digital image processing. Results show changes in shock speed, product gas propagation, and species concentrations for varied explosive charge mass. Funded by DTRA Grant HDTRA1-14-1-0070.

Transit Time and Normal Orientation of ICME-driven Shocks

NASA Astrophysics Data System (ADS)

Case, A. W.; Spence, H.; Owens, M.; Riley, P.; Linker, J.; Odstrcil, D.

2006-12-01

Interplanetary Coronal Mass Ejections (ICMEs) can drive shocks that accelerate particles to great energies. It is important to understand the acceleration, transport, and spectra of these particles in order to quantify this fundamental physical process operating throughout the cosmos. This understanding also helps to better protect astronauts and spacecraft in upcoming missions. We show that the ambient solar wind is crucial in determining characteristics of ICME-driven shocks, which in turn affect energetic particle production. We use a coupled 3-D MHD code of the corona and heliosphere to simulate ICME propagation from 30 solar radii to 1AU. ICMEs of different velocities are injected into a realistic solar wind to determine how the initial speed affects the shape and deceleration of the ICME-driven shock. We use shock transit time and shock normal orientation to quantify these dependencies. We also inject identical ICMEs into different ambient solar winds to quantify the effective drag force on an ICME.

Nonlinear theory of diffusive acceleration of particles by shock waves

NASA Astrophysics Data System (ADS)

Malkov, M. A.; Drury, L. O'C.

2001-04-01

Among the various acceleration mechanisms which have been suggested as responsible for the nonthermal particle spectra and associated radiation observed in many astrophysical and space physics environments, diffusive shock acceleration appears to be the most successful. We review the current theoretical understanding of this process, from the basic ideas of how a shock energizes a few reactionless particles to the advanced nonlinear approaches treating the shock and accelerated particles as a symbiotic self-organizing system. By means of direct solution of the nonlinear problem we set the limit to the test-particle approximation and demonstrate the fundamental role of nonlinearity in shocks of astrophysical size and lifetime. We study the bifurcation of this system, proceeding from the hydrodynamic to kinetic description under a realistic condition of Bohm diffusivity. We emphasize the importance of collective plasma phenomena for the global flow structure and acceleration efficiency by considering the injection process, an initial stage of acceleration and, the related aspects of the physics of collisionless shocks. We calculate the injection rate for different shock parameters and different species. This, together with differential acceleration resulting from nonlinear large-scale modification, determines the chemical composition of accelerated particles. The review concentrates on theoretical and analytical aspects but our strategic goal is to link the fundamental theoretical ideas with the rapidly growing wealth of observational data.

Unifying role of dissipative action in the dynamic failure of solids

NASA Astrophysics Data System (ADS)

Grady, Dennis E.

2015-04-01

A fourth-power law underlying the steady shock-wave structure and solid viscosity of condensed material has been observed for a wide range of metals and non-metals. The fourth-power law relates the steady-wave Hugoniot pressure to the fourth power of the strain rate during passage of the material through the structured shock wave. Preceding the fourth-power law was the observation in a shock transition that the product of the shock dissipation energy and the shock transition time is a constant independent of the shock pressure amplitude. Invariance of this energy-time product implies the fourth-power law. This property of the shock transition in solids was initially identified as a shock invariant. More recently, it has been referred to as the dissipative action, although no relationship to the accepted definitions of action in mechanics has been demonstrated. This same invariant property has application to a wider range of transient failure phenomena in solids. Invariance of this dissipation action has application to spall fracture, failure through adiabatic shear, shock compaction of granular media, and perhaps others. Through models of the failure processes, a clearer picture of the physics underlying the observed invariance is emerging. These insights in turn are leading to a better understanding of the shock deformation processes underlying the fourth-power law. Experimental result and material models encompassing the dynamic failure of solids are explored for the purpose of demonstrating commonalities leading to invariance of the dissipation action. Calculations are extended to aluminum and uranium metals with the intent of predicting micro-scale dynamics and spatial structure in the steady shock wave.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Grady, Dennis E.

A fourth-power law underlying the steady shock-wave structure and solid viscosity of condensed material has been observed for a wide range of metals and non-metals. The fourth-power law relates the steady-wave Hugoniot pressure to the fourth power of the strain rate during passage of the material through the structured shock wave. Preceding the fourth-power law was the observation in a shock transition that the product of the shock dissipation energy and the shock transition time is a constant independent of the shock pressure amplitude. Invariance of this energy-time product implies the fourth-power law. This property of the shock transition inmore » solids was initially identified as a shock invariant. More recently, it has been referred to as the dissipative action, although no relationship to the accepted definitions of action in mechanics has been demonstrated. This same invariant property has application to a wider range of transient failure phenomena in solids. Invariance of this dissipation action has application to spall fracture, failure through adiabatic shear, shock compaction of granular media, and perhaps others. Through models of the failure processes, a clearer picture of the physics underlying the observed invariance is emerging. These insights in turn are leading to a better understanding of the shock deformation processes underlying the fourth-power law. Experimental result and material models encompassing the dynamic failure of solids are explored for the purpose of demonstrating commonalities leading to invariance of the dissipation action. Calculations are extended to aluminum and uranium metals with the intent of predicting micro-scale dynamics and spatial structure in the steady shock wave.« less

Estimate of Shock-Hugoniot Adiabat of Liquids from Hydrodynamics

NASA Astrophysics Data System (ADS)

Bouton, E.; Vidal, P.

2007-12-01

Shock states are generally obtained from shock velocity (D) and material velocity (u) measurements. In this paper, we propose a hydrodynamical method for estimating the (D-u) relation of Nitromethane from easily measured properties of the initial state. The method is based upon the differentiation of the Rankine-Hugoniot jump relations with the initial temperature considered as a variable and under the constraint of a unique nondimensional shock-Hugoniot. We then obtain an ordinary differential equation for the shock velocity D in the variable u. Upon integration, this method predicts the shock Hugoniot of liquid Nitromethane with a 5% accuracy for initial temperatures ranging from 250 K to 360 K.

Solute transport by flow yields geometric shocks in shape evolution

NASA Astrophysics Data System (ADS)

Huang, Jinzi (Mac); Davies Wykes, Megan; Hajjar, George; Ristroph, Leif; Shelley, Michael

2017-11-01

Geological processes such as erosion and dissolution of surfaces often lead to striking shapes with strikingly sharp features. We present observations of such features forming in dissolution under gravity. In our experiment, a dissolving body with initially smooth surface evolves into an increasingly sharp needle shape. A mathematical model of its shape dynamics, derived from a boundary layer theory, predicts that a geometric shock forms at the tip of dissolved body, with the tip curvature becoming infinite in finite time. We further discuss the model's application to similar processes, such as flow driven erosion which can yield corners.

Experimental Investigation of Shock Initiation in Mixtures of Manganese and Sulfur

NASA Astrophysics Data System (ADS)

Jette, Francois-Xavier; Goroshin, Sam; Higgins, Andrew

2009-06-01

Equimolar mixtures of manganese powder and sulfur at different initial densities were tested in two different types of steel recovery capsules in order to study the shock initiation phenomenon in SHS mixtures. This mixture composition was selected due to the large exothermic heat release of the manganese-sulfur reaction (214 kJ/mol), which causes the reaction to be self-sustaining once initiated. Two different sizes of Mn particles were used for these experiments, 1-5 μm and -325 mesh (44μm or less). The test samples were placed in planar recovery ampoules and a strong shock was delivered via the detonation of a charge of amine-sensitized nitromethane. Various shock strengths were achieved by placing different thicknesses of PMMA attenuator discs between the explosive charge and the ampoule. The results confirmed that shock-induced reactions can be produced in highly non-porous mixtures. It was also found that shock interactions with the side walls of the recovery capsule can play a significant role in the initiation, and that mixtures containing the larger Mn particles were very difficult to initiate in the absence of shock interactions with the capsule walls.

Reduction of initial shock in decadal predictions using a new initialization strategy

NASA Astrophysics Data System (ADS)

He, Yujun; Wang, Bin; Liu, Mimi; Liu, Li; Yu, Yongqiang; Liu, Juanjuan; Li, Ruizhe; Zhang, Cheng; Xu, Shiming; Huang, Wenyu; Liu, Qun; Wang, Yong; Li, Feifei

2017-08-01

A novel full-field initialization strategy based on the dimension-reduced projection four-dimensional variational data assimilation (DRP-4DVar) is proposed to alleviate the well-known initial shock occurring in the early years of decadal predictions. It generates consistent initial conditions, which best fit the monthly mean oceanic analysis data along the coupled model trajectory in 1 month windows. Three indices to measure the initial shock intensity are also proposed. Results indicate that this method does reduce the initial shock in decadal predictions by Flexible Global Ocean-Atmosphere-Land System model, Grid-point version 2 (FGOALS-g2) compared with the three-dimensional variational data assimilation-based nudging full-field initialization for the same model and is comparable to or even better than the different initialization strategies for other fifth phase of the Coupled Model Intercomparison Project (CMIP5) models. Better hindcasts of global mean surface air temperature anomalies can be obtained than in other FGOALS-g2 experiments. Due to the good model response to external forcing and the reduction of initial shock, higher decadal prediction skill is achieved than in other CMIP5 models.

A magma ocean and the Earth's internal water budget

NASA Technical Reports Server (NTRS)

Ahrens, Thomas J.

1992-01-01

There are lines of evidence which relate bounds on the primordial water content of the Earth's mantle to a magma ocean and the accompanying Earth accretion process. We assume initially (before a magma ocean could form) that as the Earth accreted, it grew from volatile- (H2O, CO2, NH3, CH4, SO2, plus noble) gas-rich planetesimals, which accreted to form an initial 'primitive accretion core' (PAC). The PAC retained the initial complement of planetesimal gaseous components. Shock wave experiments in which both solid, and more recently, the gaseous components of materials such as serpentine and the Murchison meteorite have demonstrated that planetesimal infall velocities of less than 0.5 km/sec, induce shock pressures of less than 0.5 GPa and result in virtually complete retention of planetary gases.

Motivational Modulation of Self-Initiated and Externally Triggered Movement Speed Induced by Threat of Shock: Experimental Evidence for Paradoxical Kinesis in Parkinson’s Disease

PubMed Central

McDonald, Louise M.; Griffin, Harry J.; Angeli, Aikaterini; Torkamani, Mariam; Georgiev, Dejan; Jahanshahi, Marjan

2015-01-01

Background Paradoxical kinesis has been observed in bradykinetic people with Parkinson’s disease. Paradoxical kinesis occurs in situations where an individual is strongly motivated or influenced by relevant external cues. Our aim was to induce paradoxical kinesis in the laboratory. We tested whether the motivation of avoiding a mild electric shock was sufficient to induce paradoxical kinesis in externally-triggered and self-initiated conditions in people with Parkinson’s disease tested on medication and in age-matched controls. Methods Participants completed a shock avoidance behavioural paradigm in which half of the trials could result in a mild electric shock if the participant did not move fast enough. Half of the trials of each type were self-initiated and half were externally-triggered. The criterion for avoiding shock was a maximum movement time, adjusted according to each participant’s performance on previous trials using a staircase tracking procedure. Results On trials with threat of shock, both patients with Parkinson’s disease and controls had faster movement times compared to no potential shock trials, in both self-initiated and externally-triggered conditions. The magnitude of improvement of movement time from no potential shock to potential shock trials was positively correlated with anxiety ratings. Conclusions When motivated to avoid mild electric shock, patients with Parkinson’s disease, similar to healthy controls, showed significant speeding of movement execution. This was observed in both self-initiated and externally-triggered versions of the task. Nevertheless, in the ET condition the improvement of reaction times induced by motivation to avoid shocks was greater for the PD patients than controls, highlighting the value of external cues for movement initiation in PD patients. The magnitude of improvement from the no potential shock to the potential shock trials was associated with the threat-induced anxiety. This demonstration of paradoxical kinesis in the laboratory under both self-initiated and externally-triggered conditions has implications for motivational and attentional enhancement of movement speed in Parkinson’s disease. PMID:26284366

Reduction of initial shock in decadal predictions using a new initialization strategy

NASA Astrophysics Data System (ADS)

He, Yujun; Wang, Bin

2017-04-01

Initial shock is a well-known problem occurring in the early years of a decadal prediction when assimilating full-field observations into a coupled model, which directly affects the prediction skill. For the purpose to alleviate this problem, we propose a novel full-field initialization method based on dimension-reduced projection four-dimensional variational data assimilation (DRP-4DVar). Different from the available solution strategies including anomaly assimilation and bias correction, it substantially reduces the initial shock through generating more consistent initial conditions for the coupled model, which, along with the model trajectory in one-month windows, best fit the monthly mean analysis data of oceanic temperature and salinity. We evaluate the performance of initialized hindcast experiments according to three proposed indices to measure the intensity of the initial shock. The results indicate that this strategy can obviously reduce the initial shock in decadal predictions by FGOALS-g2 (the Flexible Global Ocean-Atmosphere-Land System model, Grid-point Version 2) compared with the commonly-used nudging full-field initialization for the same model as well as the different full-field initialization strategies for other CMIP5 (the fifth phase of the Coupled Model Intercomparison Project) models whose decadal prediction results are available. It is also comparable to or even better than the anomaly initialization methods. Better hindcasts of global mean surface air temperature anomaly are obtained due to the reduction of initial shock by the new initialization scheme.

Estimate of shock-Hugoniot adiabat of liquids from hydrodyamics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bouton, E.; Vidal, P.

2007-12-12

Shock states are generally obtained from shock velocity (D) and material velocity (u) measurements. In this paper, we propose a hydrodynamical method for estimating the (D-u) relation of Nitromethane from easily measured properties of the initial state. The method is based upon the differentiation of the Rankine-Hugoniot jump relations with the initial temperature considered as a variable and under the constraint of a unique nondimensional shock-Hugoniot. We then obtain an ordinary differential equation for the shock velocity D in the variable u. Upon integration, this method predicts the shock Hugoniot of liquid Nitromethane with a 5% accuracy for initial temperaturesmore » ranging from 250 K to 360 K.« less

Shock melting and vaporization of metals.

NASA Technical Reports Server (NTRS)

Ahrens, T. J.

1972-01-01

The effect of initial porosity on shock induction of melting and vaporization is investigated for Ba, Sr, Li, Fe, Al, U, and Th. For the less compressible of these metals, it is found that for a given strong shock-generation system (explosive in contact, or flyer-plate impact) an optimum initial specific volume exists such that the total entropy production, and hence the amount of metal liquid or vapor, is a maximum. Initial volumes from 1.4 to 2.0 times crystal volumes, depending on the metal sample and shock-inducing system, will result in optimum post-shock entropies.

Performance data of the new free-piston shock tunnel T5 at GALCIT

NASA Technical Reports Server (NTRS)

Hornung, H.; Sturtevant, B.; Belanger, J.; Sanderson, S.; Brouillette, M.; Jenkins, M.

1992-01-01

A new free piston shock tunnel has been constructed at the Graduate Aeronautical Laboratories at Caltec. Compression tube length is 30 m and diameter 300 mm. Shock tube length is 12 m and diameter 90 mm. Piston mass is 150 kg and maximum diaphragm burst pressure is 130 MPa. Special features of this facility are that the pressure in the driver gas is monitored throughout the compression process until well after diaphragm rupture, and that the diaphragm burst pressure can be measured dynamically. An analysis of initial performance data including transient behavior of the flow over models is presented.

Undercuts by Laser Shock Forming

NASA Astrophysics Data System (ADS)

Wielage, Hanna; Vollertsen, Frank

2011-05-01

In laser shock forming TEA-CO2-laser induced shock waves are used to form metal foils, such as aluminum or copper. The process utilizes an initiated plasma shock wave on the target surface, which leads to a forming of the foil. A challenge in forming technologies is the manufacturing of undercuts. By conventional forming methods these special forms are not feasible. In this article, it is presented that undercuts in the micro range can be produced by laser shock deep drawing. Different drawing die diameters, drawing die depths and the material aluminum in the thicknesses 20 and 50 μm were investigated. It will be presented that smaller die diameters facilitate undercuts compared to bigger die diameters. The phenomena can be explained by Barlow's formula. Furthermore, it is shown which maximum undercut depth at different die diameters can be reached. To this end, cross-sections of the different parameter combinations are displayed.

Ignition and Growth Modeling of Shock Initiation of Different Particle Size Formulations of PBXC03 Explosive

NASA Astrophysics Data System (ADS)

Hussain, Tariq; Liu, Yan; Huang, Fenglei; Duan, Zhuoping

2016-01-01

The change in shock sensitivity of explosives having various explosive grain sizes is discussed. Along with other parameters, explosive grain size is one of the key parameters controlling the macroscopic behavior of shocked pressed explosives. Ignition and growth reactive flow modeling is performed for the shock initiation experiments carried out by using the in situ manganin piezoresistive pressure gauge technique to investigate the influences of the octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) particle size on the shock initiation and the subsequent detonation growth process for the three explosive formulations of pressed PBXC03 (87% HMX, 7% 1,3,5-trichloro-2,4,6-trinitrobenzene (TATB), 6% Viton by weight). All of the formulation studied had the same density but different explosive grain sizes. A set of ignition and growth parameters was obtained for all three formulations. Only the coefficient G1 of the first growth term in the reaction rate equation was varied with the grain size; all other parameters were kept the same for all formulations. It was found that G1 decreases almost linearly with HMX particle size for PBXC03. However, the equation of state (EOS) for solid explosive had to be adjusted to fit the experimental data. Both experimental and numerical simulation results show that the shock sensitivity of PBXC03 decreases with increasing HMX particle size for the sustained pressure pulses (around 4 GPa) as obtained in the experiment. This result is in accordance with the results reported elsewhere in literature. For future work, a better approach may be to find standard solid Grüneisen EOS and product Jones-Wilkins-Lee (JWL) EOS for each formulation for the best fit to the experimental data.

Efficient particle acceleration in shocks

NASA Astrophysics Data System (ADS)

Heavens, A. F.

1984-10-01

A self-consistent non-linear theory of acceleration of particles by shock waves is developed, using an extension of the two-fluid hydrodynamical model by Drury and Völk. The transport of the accelerated particles is governed by a diffusion coefficient which is initially assumed to be independent of particle momentum, to obtain exact solutions for the spectrum. It is found that steady-state shock structures with high acceleration efficiency are only possible for shocks with Mach numbers less than about 12. A more realistic diffusion coefficient is then considered, and this maximum Mach number is reduced to about 6. The efficiency of the acceleration process determines the relative importance of the non-relativistic and relativistic particles in the distribution of accelerated particles, and this determines the effective specific heat ratio.

Atomistic simulations of shock-induced alloying reactions in Ni /Al nanolaminates

NASA Astrophysics Data System (ADS)

Zhao, Shijin; Germann, Timothy C.; Strachan, Alejandro

2006-10-01

We employ molecular dynamics simulations with a first principles-based many body potential to characterize the exothermic alloying reactions of nanostructured Ni /Al multilayers induced by shock loading. We introduce a novel technique that captures both the initial shock transit as well as the subsequent longer-time-scale Ni3Al alloy formation. Initially, the softer Al layers are shock heated to a higher temperature than the harder Ni layers as a result of a series of shock reflections from the impedance-mismatched interfaces. Once initiated, the highly exothermic alloying reactions can propagate in a self-sustained manner by mass and thermal diffusion. We also characterize the role of voids on the initiation of alloying. The interaction of the shock wave with the voids leads not only to significant local heating (hot spots) but also directly aids the intermixing between Al and Ni; both of these phenomena contribute to a significant acceleration of the alloying reactions.

Comparative study of the expansion dynamics of laser-driven plasma and shock wave in in-air and underwater ablation regimes

NASA Astrophysics Data System (ADS)

Nguyen, Thao T. P.; Tanabe, Rie; Ito, Yoshiro

2018-03-01

We compared the expansion characteristics of the plasma plumes and shock waves generated in laser-induced shock process between the two ablation regimes: in air and under water. The observation was made from the initial moment when the laser pulse hit the target until 1.5 μs. The shock processes were driven by focusing a single laser pulse (1064 nm, FWHM = 13 ns) onto the surface of epoxy-resin blocks using a 40-mm focal length lens. The estimated laser intensity at the target plane is approximate to 9 ×109Wcm-2 . We used the fast-imaging technique to observe the expansion of the plasma plume and a custom-designed time-resolved photoelasticity imaging technique to observe the propagation of shock waves with the time resolution of nanoseconds. We found that at the same intensity of the laser beam, the plasma expansion during the laser pulse follows different mechanisms: the plasma plume that grows in air follows a radiation-wave model while a detonation-wave model can explain the expansion of the plasma plume induced in water. The ideal blast wave theory can be used to predict the decay of the shock wave in air but is not appropriate to describe the decay of the shock wave induced under water.

Passage of a shock wave through inhomogeneous media and its impact on gas-bubble deformation.

PubMed

Nowakowski, A F; Ballil, A; Nicolleau, F C G A

2015-08-01

The paper investigates shock-induced vortical flows within inhomogeneous media of nonuniform thermodynamic properties. Numerical simulations are performed using a Eulerian type mathematical model for compressible multicomponent flow problems. The model, which accounts for pressure nonequilibrium and applies different equations of state for individual flow components, shows excellent capabilities for the resolution of interfaces separating compressible fluids as well as for capturing the baroclinic source of vorticity generation. The developed finite volume Godunov type computational approach is equipped with an approximate Riemann solver for calculating fluxes and handles numerically diffused zones at flow component interfaces. The computations are performed for various initial conditions and are compared with available experimental data. The initial conditions promoting a shock-bubble interaction process include weak to high planar shock waves with a Mach number ranging from 1.2 to 3 and isolated cylindrical bubble inhomogeneities of helium, argon, nitrogen, krypton, and sulphur hexafluoride. The numerical results reveal the characteristic features of the evolving flow topology. The impulsively generated flow perturbations are dominated by the reflection and refraction of the shock, the compression, and acceleration as well as the vorticity generation within the medium. The study is further extended to investigate the influence of the ratio of the heat capacities on the interface deformation.

Analysis of unsteady wave processes in a rotating channel

NASA Technical Reports Server (NTRS)

Larosiliere, L. M.; Mawid, M.

1993-01-01

The impact of passage rotation on the gas dynamic wave processes is analyzed through a numerical simulation of ideal shock-tube flow in a closed rotating-channel. Initial conditions are prescribed by assuming homentropic solid-body rotation. Relevant parameters of the problem such as wheel Mach number, hub-to-tip radius ratio, length-to-tip radius ratio, diaphragm temperature ratio, and diaphragm pressure ratio are varied. The results suggest possible criteria for assessing the consequences of passage rotation on the wave processes, and they may therefore be applicable to pressure-exchange wave rotors. It is shown that for a fixed geometry and initial conditions, the contact interface acquires a distorted three-dimensional time-dependent orientation at non-zero wheel Mach numbers. At a fixed wheel Mach number, the level of distortion depends primarily on the density ratio across the interface as well as the hub-to-tip radius ratio. Rarefaction fronts, shocks, and contact interfaces are observed to propagate faster with increasing wheel Mach number.

Analysis of unsteady wave processes in a rotating channel

NASA Astrophysics Data System (ADS)

Larosiliere, Louis M.; Mawid, M.

1993-06-01

The impact of passage rotation on the gas dynamic wave processes is analyzed through a numerical simulation of ideal shock-tube flow in a closed rotating-channel. Initial conditions are prescribed by assuming homentropic solid-body rotation. Relevant parameters of the problem such as wheel Mach number, hub-to-tip radius ratio, length-to-tip radius ratio, diaphragm temperature ratio, and diaphragm pressure ratio are varied. The results suggest possible criteria for assessing the consequences of passage rotation on the wave processes, and they may therefore be applicable to pressure-exchange wave rotors. It is shown that for a fixed geometry and initial conditions, the contact interface acquires a distorted three-dimensional time-dependent orientation at non-zero wheel Mach numbers. At a fixed wheel Mach number, the level of distortion depends primarily on the density ratio across the interface as well as the hub-to-tip radius ratio. Rarefaction fronts, shocks, and contact interfaces are observed to propagate faster with increasing wheel Mach number.

Shock interactions with heterogeneous energetic materials

NASA Astrophysics Data System (ADS)

Yarrington, Cole D.; Wixom, Ryan R.; Damm, David L.

2018-03-01

The complex physical phenomenon of shock wave interaction with material heterogeneities has significant importance and nevertheless remains little understood. In many materials, the observed macroscale response to shock loading is governed by characteristics of the microstructure. Yet, the majority of computational studies aimed at predicting phenomena affected by these processes, such as the initiation and propagation of detonation waves in explosives or shock propagation in geological materials, employ continuum material and reactive burn model treatment. In an effort to highlight the grain-scale processes that underlie the observable effects in an energetic system, a grain-scale model for hexanitrostilbene (HNS) has been developed. The measured microstructures were used to produce synthetic computational representations of the pore structure, and a density functional theory molecular dynamics derived equation of state (EOS) was used for the fully dense HNS matrix. The explicit inclusion of the microstructure along with a fully dense EOS resulted in close agreement with historical shock compression experiments. More recent experiments on the dynamic reaction threshold were also reproduced by inclusion of a global kinetics model. The complete model was shown to reproduce accurately the expected response of this heterogeneous material to shock loading. Mesoscale simulations were shown to provide a clear insight into the nature of threshold behavior and are a way to understand complex physical phenomena.

Shock interactions with heterogeneous energetic materials

DOE PAGES

Yarrington, Cole D.; Wixom, Ryan R.; Damm, David L.

2018-03-14

The complex physical phenomenon of shock wave interaction with material heterogeneities has significant importance and nevertheless remains little understood. In many materials, the observed macroscale response to shock loading is governed by characteristics of the microstructure. Yet the majority of computational studies aimed at predicting phenomena affected by these processes, such as initiation and propagation of detonation waves in explosives, or shock propagation in geological materials, employ continuum material and reactive burn model treatment. In an effort to highlight the grain-scale processes that underlie the observable effects in an energetic system, a grain-scale model for hexanitrostilbene (HNS) has been developed.more » Measured microstructures were used to produce synthetic computational representations of the pore structure, and a density functional theory molecular dynamics (DFT-MD) derived equation of state (EOS) was used for the fully dense HNS matrix. The explicit inclusion of microstructure along with a fully-dense EOS resulted in close agreement with historical shock compression experiments. More recent experiments on dynamic reaction threshold were also reproduced by inclusion of a global kinetics model. The complete model was shown to reproduce accurately the expected response of this heterogeneous material to shock loading. Mesoscale simulations were shown to provide clear insight into the nature of threshold behavior, and are a way to understand complex physical phenomena.« less

Localized atomic segregation in the spalled area of a Zr50Cu40Al10 bulk metallic glasses induced by laser-shock experiment

NASA Astrophysics Data System (ADS)

Jodar, B.; Loison, D.; Yokoyama, Y.; Lescoute, E.; Nivard, M.; Berthe, L.; Sangleboeuf, J.-C.

2018-02-01

Laser-shock experiments were performed on a ternary {Zr50{Cu}40{Al}10} bulk metallic glass. A spalling process was studied through post-mortem analyses conducted on a recovered sample and spall. Scanning electron microscopy magnification of fracture surfaces revealed the presence of a peculiar feature known as cup-cone. Cups are found on sample fracture surface while cones are observed on spall. Two distinct regions can be observed on cups and cones: a smooth viscous-like region in the center and a flat one with large vein-pattern in the periphery. Energy dispersive spectroscopy measurements conducted on these features emphasized atomic distribution discrepancies both on the sample and spall. We propose a mechanism for the initiation and the growth of these features but also a process for atomic segregation during spallation. Cup and cones would originate from cracks arising from shear bands formation (softened paths). These shear bands result from a quadrupolar-shaped atomic disorder engendered around an initiation site by shock wave propagation. This disorder turns into a shear band when tensile front reaches spallation plane. During the separation process, temperature gain induced by shock waves and shear bands generation decreases material viscosity leading to higher atomic mobility. Once in a liquid-like form, atomic clusters migrate and segregate due to inertial effects originating from particle velocity variation (interaction of release waves). As a result, a high rate of copper is found in sample cups and high zirconium concentration is found on spall cones.

Lunar and Planetary Science XXXV: Effects of Impacts: Shock and Awe

NASA Technical Reports Server (NTRS)

Kyte, F. T.; Koeberl, C.

2004-01-01

This document discusses the following topics: Zircon as a Shock Indicator in Impactites of Drill Core Yaxcopoil-1, Chicxulub Impact Structure, Mexico; Experimental Investigation of Shock Effects in a Metapelitic Granulite; Experimental Reproduction of Shock Veins in Single-Crystal Minerals; Post-Shock Crystal-Plastic Processes in Quartz from Crystalline Target Rocks of the Charlevoix Impact Structure; Shock Reequilibration of Fluid Inclusions; How Does Tektite Glass Lose Its Water?; Assessing the Role of Anhydrite in the KT Mass Extinction: Hints from Shock-loading Experiments; A Mineralogical and Geochemical Study of the Nonmarine Permian/Triassic Boundary in the Southern Karoo Basin, South Africa; Extraterrestrial Chromium in the Permian-Triassic Boundary at Graphite Peak, Antarctica; Magnetic Fe,Si,Al-rich Impact Spherules from the P-T Boundary Layer at Graphite Peak, Antarctica; A Newly Recognized Late Archean Impact Spherule Layer in the Reivilo Formation, Griqualand West Basin, South Africa; Initial Cr-Isotopic and Iridium Measurements of Concentrates from Late Eocene Cpx-Spherule Deposits; An Ordinary Chondrite Impactor Composition for the Bosumtwi Impact Structure, Ghana, West Africa: Discussion of Siderophile Element Contents and Os and Cr Isotope Data.

Control of quasi-monoenergetic electron beams from laser-plasma accelerators by adjusting shock density profile

NASA Astrophysics Data System (ADS)

Tsai, Hai-En; Swanson, Kelly K.; Lehe, Remi; Barber, Sam K.; Isono, Fumika; Otero, Jorge G.; Liu, Xinyao; Mao, Hann-Shin; Steinke, Sven; Tilborg, Jeroen Van; Geddes, Cameron G. R.; Leemans, Wim

2017-10-01

High-level control of a laser-plasma accelerator (LPA) using a shock injector was demonstrated by systematically varying the shock injector profile, including the shock angle, up-ramp width and shock position. Particle-in-cell (PIC) simulation explored how variations in the shock profile impacted the injection process and confirmed results obtained through acceleration experiments. These results establish that, by adjusting shock position, up-ramp, and angle, beam energy, energy spread, and pointing can be controlled. As a result, e-beam were highly tunable from 25 to 300 MeV with <8% energy spread, 1.5 mrad divergence and <1 mrad pointing fluctuation. This highly controllable LPA represents an ideal and compact beam source for the ongoing MeV Thomson photon experiments. Set-up and initial experimental design on a newly constructed one hundred TW laser system will be presented. This work is supported by the US DOE under Contract No. DE-AC02-05CH11231, and by the US DOE National Nuclear Security Administration, Defense Nuclear Nonproliferation R&D (NA22).

Experiments and simulations of Richtmyer-Meshkov Instability with measured,volumetric initial conditions

NASA Astrophysics Data System (ADS)

Sewell, Everest; Ferguson, Kevin; Jacobs, Jeffrey; Greenough, Jeff; Krivets, Vitaliy

2016-11-01

We describe experiments of single-shock Richtmyer-Meskhov Instability (RMI) performed on the shock tube apparatus at the University of Arizona in which the initial conditions are volumetrically imaged prior to shock wave arrival. Initial perturbations play a major role in the evolution of RMI, and previous experimental efforts only capture a single plane of the initial condition. The method presented uses a rastered laser sheet to capture additional images throughout the depth of the initial condition immediately before the shock arrival time. These images are then used to reconstruct a volumetric approximation of the experimental perturbation. Analysis of the initial perturbations is performed, and then used as initial conditions in simulations using the hydrodynamics code ARES, developed at Lawrence Livermore National Laboratory (LLNL). Experiments are presented and comparisons are made with simulation results.

Maximum initial growth-rate of strong-shock-driven Richtmyer-Meshkov instability

NASA Astrophysics Data System (ADS)

Abarzhi, Snezhana I.; Bhowmich, Aklant K.; Dell, Zachary R.; Pandian, Arun; Stanic, Milos; Stellingwerf, Robert F.; Swisher, Nora C.

2017-10-01

We focus on classical problem of dependence on the initial conditions of the initial growth-rate of strong shocks driven Richtmyer-Meshkov instability (RMI) by developing a novel empirical model and by employing rigorous theories and Smoothed Particle Hydrodynamics (SPH) simulations to describe the simulations data with statistical confidence in a broad parameter regime. For given values of the shock strength, fluids' density ratio, and wavelength of the initial perturbation of the fluid interface, we find the maximum value of RMI initial growth-rate, the corresponding amplitude scale of the initial perturbation, and the maximum fraction of interfacial energy. This amplitude scale is independent of the shock strength and density ratio, and is characteristic quantity of RMI dynamics. We discover the exponential decay of the ratio of the initial and linear growth-rates of RMI with the initial perturbation amplitude that excellently agrees with available data. National Science Foundation, USA.

Maximum initial growth-rate of strong-shock-driven Richtmyer-Meshkov instability

NASA Astrophysics Data System (ADS)

Abarzhi, Snezhana I.; Bhowmich, Aklant K.; Dell, Zachary R.; Pandian, Arun; Stanic, Milos; Stellingwerf, Robert F.; Swisher, Nora C.

2017-11-01

We focus on classical problem of dependence on the initial conditions of the initial growth-rate of strong shocks driven Richtmyer-Meshkov instability (RMI) by developing a novel empirical model and by employing rigorous theories and Smoothed Particle Hydrodynamics (SPH) simulations to describe the simulations data with statistical confidence in a broad parameter regime. For given values of the shock strength, fluids' density ratio, and wavelength of the initial perturbation of the fluid interface, we find the maximum value of RMI initial growth-rate, the corresponding amplitude scale of the initial perturbation, and the maximum fraction of interfacial energy. This amplitude scale is independent of the shock strength and density ratio, and is characteristic quantity of RMI dynamics. We discover the exponential decay of the ratio of the initial and linear growth-rates of RMI with the initial perturbation amplitude that excellently agrees with available data. National Science Foundation, USA.

Improved Reactive Flow Modeling of the LX-17 Double Shock Experiments

NASA Astrophysics Data System (ADS)

Rehagen, Thomas J.; Vitello, Peter

2017-06-01

Over driven double shock experiments provide a measurement of the properties of the reaction product states of the insensitive high explosive LX-17 (92.5% TATB and 7.5% Kel-F by weight). These experiments used two flyer materials mounted on the end of a projectile to send an initial shock through the LX-17, followed by a second shock of a higher magnitude into the detonation products. In the experiments, the explosive was initially driven by the flyer plate to pressures above the Chapman-Jouguet state. The particle velocity history was recorded by Photonic Doppler Velocimetry (PDV) probes pointing at an aluminum foil coated LiF window. The PDV data shows a sharp initial shock and decay, followed by a rounded second shock. Here, the experimental results are compared to 2D and 3D Cheetah reactive flow modeling. Our default Cheetah reactive flow model fails to accurately reproduce the decay of the first shock or the curvature or strength of the second shock. A new model is proposed in which the carbon condensate produced in the reaction zone is controlled by a kinetic rate. This allows the carbon condensate to be initially out of chemical equilibrium with the product gas. This new model reproduces the initial detonation peak and decay, and matches the curvature of the second shock, however, it still over-predicts the strength of the second shock. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract No. DE-AC52-07NA27344.

Surface instabilities in shock loaded granular media

NASA Astrophysics Data System (ADS)

Kandan, K.; Khaderi, S. N.; Wadley, H. N. G.; Deshpande, V. S.

2017-12-01

The initiation and growth of instabilities in granular materials loaded by air shock waves are investigated via shock-tube experiments and numerical calculations. Three types of granular media, dry sand, water-saturated sand and a granular solid comprising PTFE spheres were experimentally investigated by air shock loading slugs of these materials in a transparent shock tube. Under all shock pressures considered here, the free-standing dry sand slugs remained stable while the shock loaded surface of the water-saturated sand slug became unstable resulting in mixing of the shocked air and the granular material. By contrast, the PTFE slugs were stable at low pressures but displayed instabilities similar to the water-saturated sand slugs at higher shock pressures. The distal surfaces of the slugs remained stable under all conditions considered here. Eulerian fluid/solid interaction calculations, with the granular material modelled as a Drucker-Prager solid, reproduced the onset of the instabilities as seen in the experiments to a high level of accuracy. These calculations showed that the shock pressures to initiate instabilities increased with increasing material friction and decreasing yield strain. Moreover, the high Atwood number for this problem implied that fluid/solid interaction effects were small, and the initiation of the instability is adequately captured by directly applying a pressure on the slug surface. Lagrangian calculations with the directly applied pressures demonstrated that the instability was caused by spatial pressure gradients created by initial surface perturbations. Surface instabilities are also shown to exist in shock loaded rear-supported granular slugs: these experiments and calculations are used to infer the velocity that free-standing slugs need to acquire to initiate instabilities on their front surfaces. The results presented here, while in an idealised one-dimensional setting, provide physical understanding of the conditions required to initiate instabilities in a range of situations involving the explosive dispersion of particles.

Collisional processes involving icy bodies in the solar system

NASA Astrophysics Data System (ADS)

Stewart-Mukhopadhyay, Sarah Toby

1. The shock Hugoniot of solid ice. We present a complete description of the solid ice Hugoniot based on new shock wave experiments conducted at an initial temperature of 100 K and previously published data obtained at 263 K. We identify five regions on the solid ice Hugoniot: (1)elastic shock waves, (2)ice Ih deformation shocks, transformation shocks to (3)ice VI, (4)ice VII, and (5)liquid water. In each region, data obtained at different initial temperatures are described by a single US - Δup shock equation of state. The dynamic strength of ice Ih is strongly dependent on temperature. The Hugoniot Elastic Limit varies from 0.05 to 0.62 GPa, as a function of temperature and peak shock stress. We estimate the entropy and temperature along the 100 and 263 K Hugoniots and derive the critical pressures for shock-induced incipient (IM) and complete (CM) melting upon release. On the 100 K Hugoniot, the critical pressures are about 4.5 and between 5 6 GPa for IM and CM, respectively. On the 263 K Hugoniot, the critical pressures are 0.6 and 3.7 GPa for IM and CM, lower than previously suggested. Shock-induced melting of ice will be widespread in impact events. 2. Rampart crater formation on Mars. A complete description for formation of lobate ejecta blankets around Martian craters by fluidization with liquid water is presented based on impact cratering simulations and shock wave data on H2O ice. Shock wave experiments show that ice at Martian temperatures, 150 to 275 K, will begin to melt when shocked above 2.2 to 0.6 GPa, respectively, lower than previously expected. We find that more than half the excavated ice is melted by the impact shock; therefore, debris flow modeling of fluidized ejecta morphologies may directly quantify the amount of ground ice. The estimated quantity of water required to form the observed fluidized ejecta blankets is equivalent to a global layer about 0.6 m thick and the implied global regolith ice content, within the upper ˜2 km sampled by rampart craters, is equivalent to a 120 m layer.

Triggering collapse of the presolar dense cloud core and injecting short-lived radioisotopes with a shock wave. III. Rotating three-dimensional cloud cores

DOE Office of Scientific and Technical Information (OSTI.GOV)

Boss, Alan P.; Keiser, Sandra A., E-mail: boss@dtm.ciw.edu

2014-06-10

A key test of the supernova triggering and injection hypothesis for the origin of the solar system's short-lived radioisotopes is to reproduce the inferred initial abundances of these isotopes. We present here the most detailed models to date of the shock wave triggering and injection process, where shock waves with varied properties strike fully three-dimensional, rotating, dense cloud cores. The models are calculated with the FLASH adaptive mesh hydrodynamics code. Three different outcomes can result: triggered collapse leading to fragmentation into a multiple protostar system; triggered collapse leading to a single protostar embedded in a protostellar disk; or failure tomore » undergo dynamic collapse. Shock wave material is injected into the collapsing clouds through Rayleigh-Taylor fingers, resulting in initially inhomogeneous distributions in the protostars and protostellar disks. Cloud rotation about an axis aligned with the shock propagation direction does not increase the injection efficiency appreciably, as the shock parameters were chosen to be optimal for injection even in the absence of rotation. For a shock wave from a core-collapse supernova, the dilution factors for supernova material are in the range of ∼10{sup –4} to ∼3 × 10{sup –4}, in agreement with recent laboratory estimates of the required amount of dilution for {sup 60}Fe and {sup 26}Al. We conclude that a type II supernova remains as a promising candidate for synthesizing the solar system's short-lived radioisotopes shortly before their injection into the presolar cloud core by the supernova's remnant shock wave.« less

Modeling the effect of orientation on the shock response of a damageable composite material

NASA Astrophysics Data System (ADS)

Lukyanov, Alexander A.

2012-10-01

A carbon fiber-epoxy composite (CFEC) shock response in the through thickness orientation and in one of the fiber directions is significantly different. The hydrostatic pressure inside anisotropic materials depends on deviatoric strain components as well as volumetric strain. Non-linear effects, such as shock effects, can be incorporated through the volumetric straining in the material. Thus, a new basis is required to couple the anisotropic material stiffness and strength with anisotropic shock effects, associated energy dependence, and damage softening process. This article presents these constitutive equations for shock wave modeling of a damageable carbon fiber-epoxy composite. Modeling the effect of fiber orientation on the shock response of a CFEC has been performed using a generalized decomposition of the stress tensor [A. A. Lukyanov, Int. J. Plast. 24, 140 (2008)] and Mie-Grüneisen's extrapolation of high-pressure shock Hugoniot states to other thermodynamics states for shocked CFEC materials. The three-wave structure (non-linear anisotropic, fracture, and isotropic elastic waves) that accompanies damage softening process is also proposed in this work for describing CFEC behavior under shock loading which allows to remove any discontinuities observed in the linear case for relation between shock velocities and particle velocities [A. A. Lukyanov, Eur. Phys. J. B 74, 35 (2010)]. Different Hugoniot stress levels are obtained when the material is impacted in different directions; their good agreement with the experiment demonstrates that the anisotropic equation of state, strength, and damage model are adequate for the simulation of shock wave propagation within damageable CFEC material. Remarkably, in the through thickness orientation, the material behaves similar to a simple polymer whereas in the fiber direction, the proposed in this paper model explains an initial ramp, before at sufficiently high stresses, and a much faster rising shock above it. The numerical results for shock wave modeling using proposed constitutive equations are presented, discussed, and future studies are outlined.

Shock initiation of 2,4-dinitroimidazole (2,4-DNI)

NASA Astrophysics Data System (ADS)

Urtiew, P. A.; Tarver, C. M.; Simpson, R. L.

1996-05-01

The shock sensitivity of the pressed solid explosive 2,4-dinitroimidazole (2,4-DNI) was determined using the embedded manganin pressure gauge technique. At an initial shock pressure of 2 GPa, several microseconds were required before any exothermic reaction was observed. At 4 GPa, 2,4-DNI reacted more rapidly but did not transition to detonation at the 12 mm deep gauge position. At 6 GPa, detonation occurred in less than 6 mm of shock propagation. Thus, 2,4-DNI is more shock sensitive than TATB-based explosives but is considerably less shock sensitive than HMX-based explosives. An Ignition and Growth reactive flow model for 2,4-DNI based on these gauge records showed that 2,4-DNI exhibits shock initiation characteristics similar to TATB but reacts faster. The chemical structure of 2,4-DNI suggests that it may exhibit thermal decomposition reactions similar to nitroguanine and explosives with similar ring structures, such as ANTA and NTO.

Shock loading and release behavior of silicon nitride

NASA Astrophysics Data System (ADS)

Kawai, N.; Tsuru, T.; Hidaka, N.; Liu, X.; Mashimo, T.

2017-01-01

Shock-reshock and shock-release experiments were performed on silicon nitride ceramics above and below its phase transition pressure. Experimental results clearly show the occurrence of elastic-plastic transition and phase transition during initial shock loading. The HEL and phase transition stress are determined as 11.6 and 34.5 GPa, respectively. Below the phase transition stress, the reshock profile consists of the single shock with short rise time, while the release profile shows the gradual release followed by rapid one. Above phase transition stress, reshock and release behavior varies with the initial shock stress. In the case of reshock and release from about 40 GPa, the reshock structure is considerably dispersed, while the release structure shows rapid release. In the reshock profile from about 50 GPa, the formation of the shock wave with the small ramped precursor is observed. And, the release response from same shocked condition shows initial gradual release and subsequent quite rapid one. These results would provide the information about how phase transformation kinetics effects on the reshock and release behavior.

Shock Initiation Characteristics of an Aluminized DNAN/RDX Melt-Cast Explosive

NASA Astrophysics Data System (ADS)

Cao, Tong-Tang; Zhou, Lin; Zhang, Xiang-Rong; Zhang, Wei; Miao, Fei-Chao

2017-10-01

Shock sensitivity is one of the key parameters for newly developed, 2,4-dinitroanisole (DNAN)-based, melt-cast explosives. For this paper, a series of shock initiation experiments were conducted using a one-dimensional Lagrangian system with a manganin piezoresistive pressure gauge technique to evaluate the shock sensitivity of an aluminized DNAN/cyclotrimethylenetrinitramine (RDX) melt-cast explosive. This study fully investigated the effects of particle size distributions in both RDX and aluminum, as well as the RDX's crystal quality on the shock sensitivity of the aluminized DNAN/RDX melt-cast explosive. Ultimately, the shock sensitivity of the aluminized DNAN/RDX melt-cast explosives increases when the particle size decreases in both RDX and aluminum. Additionally, shock sensitivity increases when the RDX's crystal quality decreases. In order to simulate these effects, an Ignition and Growth (I&G) reactive flow model was calibrated. This calibrated I&G model was able to predict the shock initiation characteristics of the aluminized DNAN/RDX melt-cast explosive.

Critical energy for shock initiation of fuze train explosives

DOE Office of Scientific and Technical Information (OSTI.GOV)

Walker, F.E.; Wasley, R.J.; Green, L.G.

1973-01-01

Results of shock initiation experiments conducted for tetryl and A-5 are presented, along with some data on the shock initiation of other explosives. The experiments were conducted using a gun system. An equation which has been useful in correlating these shock data is given. Some applications of the critical energy concept (represented by the above equation), to explosive train designs for NASA space systems are included. The concept's usefulness to DOD ordnance agencies now replacing tetryl in fuze trains with A-5 is also indicated. (auth)

Richtmyer-Meshkov evolution under steady shock conditions in the high-energy-density regime

DOE PAGES

Di Stefano, C. A.; Malamud, G.; Kuranz, C. C.; ...

2015-03-17

This work presents direct experimental evidence of long-predicted nonlinear aspects of the Richtmyer-Meshkov (RM) process, in which new modes first arise from the coupling of initially-present modes, and in which shorter-wavelength modes are eventually overtaken by longer-wavelength modes. This is accomplished using a technique we developed employing a long driving laser pulse to create a strong (Mach ~ 8) shock across a well-characterized material interface seeded by a two-mode sinusoidal perturbation. Furthermore, this technique further permits the shock to be sustained, without decay of the high-energy-density flow conditions, long enough for the system to evolve into the nonlinear phase.

Finite GUE Distribution with Cut-Off at a Shock

NASA Astrophysics Data System (ADS)

Ferrari, P. L.

2018-03-01

We consider the totally asymmetric simple exclusion process with initial conditions generating a shock. The fluctuations of particle positions are asymptotically governed by the randomness around the two characteristic lines joining at the shock. Unlike in previous papers, we describe the correlation in space-time without employing the mapping to the last passage percolation, which fails to exists already for the partially asymmetric model. We then consider a special case, where the asymptotic distribution is a cut-off of the distribution of the largest eigenvalue of a finite GUE matrix. Finally we discuss the strength of the probabilistic and physically motivated approach and compare it with the mathematical difficulties of a direct computation.

Origin of the bright prompt optical emission in the naked eye burst

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hascoeet, R.; Daigne, F.; Mochkovitch, R.

The huge optical brightness of GRB 080319B (the 'Naked Eye Burst') makes this event really challenging for models of the prompt GRB emission. In the framework of the internal shock model, we investigate a scenario where the dominant radiative process is synchrotron emission and the high optical flux is due to the dynamical properties of the relativistic outflow : if the initial Lorentz factor distribution in the jet is highly variable, many internal shocks will form within the outflow at various radii. The most violent shocks will produce the main gamma-ray component while the less violent ones will contribute atmore » lower energy, including the optical range.« less

Numerical investigation of separated nozzle flows

NASA Technical Reports Server (NTRS)

Chen, C. L.; Chakravarthy, S. R.; Hung, C. M.

1994-01-01

A numerical study of axisymmetric overexpanded nozzle is presented. The flow structure of the startup and throttle-down processes are examined. During the impulsive startup process, observed flow features include the Mach disk, separation shock, Mach stem, vortex core, contact surface, slip stream, initial shock front, and shocklet. Also the movement of the Mach disk is not monotonical in the downstream direction. For a range of pressure ratios, hysteresis phenomenon occurs; different solutions were obtained depending on different processes. Three types of flow structures were observed. The location of separation point and the lower end turning point of hysteresis are closely predicted. A high peak of pressure is associated with the nozzle flow reattachment. The reversed vortical structure and affects engine performance.

Microenergetic Shock Initiation Studies on Deposited Films of Petn

NASA Astrophysics Data System (ADS)

Tappan, Alexander S.; Wixom, Ryan R.; Trott, Wayne M.; Long, Gregory T.; Knepper, Robert; Brundage, Aaron L.; Jones, David A.

2009-12-01

Films of the high explosive PETN (pentaerythritol tetranitrate) up to 500-μm thick have been deposited through physical vapor deposition, with the intent of creating well-defined samples for shock-initiation studies. PETN films were characterized with microscopy, x-ray diffraction, and focused ion beam nanotomography. These high-density films were subjected to strong shocks in both the out-of-plane and in-plane orientations. Initiation behavior was monitored with high-speed framing and streak camera photography. Direct initiation with a donor explosive (either RDX with binder, or CL-20 with binder) was possible in both orientations, but with the addition of a thin aluminum buffer plate (in-plane configuration only), initiation proved to be difficult. Initiation was possible with an explosively-driven 0.13-mm thick Kapton flyer and direct observation of initiation behavior was examined using streak camera photography at different flyer velocities. Models of this configuration were created using the shock physics code CTH.

Shock-activated electrochemical power supplies

DOEpatents

Benedick, William B.; Graham, Robert A.; Morosin, Bruno

1988-01-01

A shock-activated electrochemical power supply is provided which is initiated extremely rapidly and which has a long shelf life. Electrochemical power supplies of this invention are initiated much faster than conventional thermal batteries. Power supplies of this invention comprise an inactive electrolyte and means for generating a high-pressure shock wave such that the shock wave is propagated through the electrolytes rendering the electrolyte electrochemically active.

Shock-activated electrochemical power supplies

DOEpatents

Benedick, W.B.; Graham, R.A.; Morosin, B.

1988-11-08

A shock-activated electrochemical power supply is provided which is initiated extremely rapidly and which has a long shelf life. Electrochemical power supplies of this invention are initiated much faster than conventional thermal batteries. Power supplies of this invention comprise an inactive electrolyte and means for generating a high-pressure shock wave such that the shock wave is propagated through the electrolytes rendering the electrolyte electrochemically active. 2 figs.

Shock Initiation of Wedge-shaped Explosive Measured with Smear Camera and Photon Doppler Velocimetry

NASA Astrophysics Data System (ADS)

Gu, Yan

2017-06-01

Triaminotrinitrobenzene (TATB) is an important insensitive high explosive in conventional weapons due to its safety and high energy. In order to have an insight into the shock initiation performance of a TATB-based insensitive high explosive (IHE), experimental measurements of the particle velocity histories of the TATB-based Explosive using Photon Doppler Velocimetry and shock wave profile of the TATB-based explosive using High Speed Rotating Mirror Smear Camera had been performed. In this paper, we would describe the shock initiation performance of the TATB-based explosive by run-to-detonation distance and the particle velocity history at an initialization shock of about 7.9 GPa. The parameters of hugoniot of unreacted the TATB-based explosive and Pop relationship could be derived with the particle velocity history obtained in this paper.

Experimental Investigation of Shock Initiation in Mixtures of Manganese and Sulfur

NASA Astrophysics Data System (ADS)

Jetté, F. X.; Goroshin, S.; Higgins, A. J.

2009-12-01

Equimolar mixtures of manganese powder and sulfur at different starting densities were tested in two different types of steel recovery capsules in order to study the shock initiation phenomenon in Self-Propagating High-Temperature Synthesis (SHS) mixtures. Two different sizes of Mn particles were used for these experiments, <10 μm and -325 mesh (<44 μm). This mixture was selected due to the large exothermic heat release of the manganese-sulfur reaction (214 kJ/mol), which causes the reaction to be self-sustaining once initiated. The test samples were placed in planar recovery capsules and a strong shock was delivered via the detonation of a charge of amine-sensitized nitromethane. Various shock strengths were achieved by placing different thicknesses of PMMA attenuator discs between the explosive charge and the capsule. The results confirmed that shock-induced reactions can be produced in highly non-porous mixtures. It was also found that shock interactions with the side walls of the recovery capsule can play a significant role in the initiation.

Implementation of a Cardiogenic Shock Team and Clinical Outcomes (INOVA-SHOCK Registry): Observational and Retrospective Study.

PubMed

Tehrani, Behnam; Truesdell, Alexander; Singh, Ramesh; Murphy, Charles; Saulino, Patricia

2018-06-28

The development and implementation of a Cardiogenic Shock initiative focused on increased disease awareness, early multidisciplinary team activation, rapid initiation of mechanical circulatory support, and hemodynamic-guided management and improvement of outcomes in cardiogenic shock. The objectives of this study are (1) to collect retrospective clinical outcomes for acute decompensated heart failure cardiogenic shock and acute myocardial infarction cardiogenic shock, and compare current versus historical survival rates and clinical outcomes; (2) to evaluate Inova Heart and Vascular Institute site specific outcomes before and after initiation of the Cardiogenic Shock team on January 1, 2017; (3) to compare outcomes related to early implementation of mechanical circulatory support and hemodynamic-guided management versus historical controls; (4) to assess survival to discharge rate in patients receiving intervention from the designated shock team and (5) create a clinical archive of Cardiogenic Shock patient characteristics for future analysis and the support of translational research studies. This is an observational, retrospective, single center study. Retrospective and prospective data will be collected in patients treated at the Inova Heart and Vascular Institute with documented cardiogenic shock as a result of acute decompensated heart failure or acute myocardial infarction. This registry will include data from patients prior to and after the initiation of the multidisciplinary Cardiogenic Shock team on January 1, 2017. Clinical outcomes associated with early multidisciplinary team intervention will be analyzed. In the study group, all patients evaluated for documented cardiogenic shock (acute decompensated heart failure cardiogenic shock, acute myocardial infarction cardiogenic shock) treated at the Inova Heart and Vascular Institute by the Cardiogenic Shock team will be included. An additional historical Inova Heart and Vascular Institute control group will be analyzed as a comparator. Means with standard deviations will be reported for outcomes. For categorical variables, frequencies and percentages will be presented. For continuous variables, the number of subjects, mean, standard deviation, minimum, 25th percentile, median, 75th percentile and maximum will be reported. Reported differences will include standard errors and 95% CI. Preliminary data analysis for the year 2017 has been completed. Compared to a baseline 2016 survival rate of 47.0%, from 2017 to 2018, CS survival rates were increased to 57.9% (58/110) and 81.3% (81/140), respectively (P=.01 for both). Study data will continue to be collected until December 31, 2018. The preliminary results of this study demonstrate that the INOVA SHOCK team approach to the treatment of Cardiogenic Shock with early team activation, rapid initiation of mechanical circulatory support, hemodynamic-guided management, and strict protocol adherence is associated with superior clinical outcomes: survival to discharge and overall survival when compared to 2015 and 2016 outcomes prior to Shock team initiation. What may limit the generalization of these results of this study to other populations are site specific; expertise of the team, strict algorithm adherence based on the INOVA SHOCK protocol, and staff commitment to timely team activation. Retrospective clinical outcomes (acute decompensated heart failure cardiogenic shock, acute myocardial infarction cardiogenic shock) demonstrated an increase in current survival rates when compared to pre-Cardiogenic Shock team initiation, rapid team activation and diagnosis and timely utilization of mechanical circulatory support. ClinicalTrials.gov NCT03378739; https://clinicaltrials.gov/ct2/show/NCT03378739 (Archived by WebCite at http://www.webcitation.org/701vstDGd). ©Behnam Tehrani, Alexander Truesdell, Ramesh Singh, Charles Murphy, Patricia Saulino. Originally published in JMIR Research Protocols (http://www.researchprotocols.org), 28.06.2018.

Prolonged electron accelerations at a high-Mach-number, quasi-perpendicular shock

NASA Astrophysics Data System (ADS)

Matsumoto, Y.; Amano, T.; Kato, T.; Hoshino, M.

2016-12-01

Elucidating acceleration mechanisms of charged particles have been of great interests in laboratory, space, and astrophysical plasmas. Among other mechanisms, a collision-less shock is thought as an efficient particle accelerator. The idea has been strengthened by radio, X-ray, and gamma-ray observations of astrophysical objects such as supernova remnant shocks, where it has been indicated that protons and electrons are efficiently accelerated to TeV energies at such very strong shock waves. Efficient electron accelerations at high-Mach-number shocks was also suggested recently by in-situ measurements at the Saturn's bow shock. Motivated by these circumstances, laboratory experiments using high-power laser facilities emerge to provide a new platform to tackle these problems.Numerical simulations have revealed that electrons can be efficiently heated and accelerated via so-called the shock surfing acceleration mechanism in which electron-scale Buneman instability played key roles. Recently, Matsumoto et al. [2015] proposed a stochastic acceleration mechanism by turbulent reconnection in the shock transition region through excitation of the ion Weibel instability. In order to deal with the two different acceleration mechanisms in a self-consistent system, we examined 3D PIC simulations of a quasi-perpendicular, high-Mach-number shock. We successfully followed a long term evolution in which two different acceleration mechanisms coexist in the 3D shock structure. The Buneman instability is strongly excited ahead of the shock front in the same manner as have been found in 2D simulations. The surfing acceleration is found to be very effective in the present 3D system. In the transition region, the ion-beam Weibel instability generated strong magnetic field turbulence in 3D space. Energetic electrons, which initially experienced the surfing acceleration, undergo pitch-angle diffusion by interacting with the turbulent fields and thus stay in the upstream regions. The ion Weibel turbulence is essentially the key to prolonged acceleration processes which can produce relativistic particles with energies more than 1000 times the initial kinetic energy. We present how such relativistic electrons are produced during traveling in the 3D shock structure.

Microenergetic Shock Initiation Studies on Deposited Films of PETN

NASA Astrophysics Data System (ADS)

Tappan, Alexander S.; Wixom, Ryan R.; Trott, Wayne M.; Long, Gregory T.; Knepper, Robert; Brundage, Aaron L.; Jones, David A.

2009-06-01

Films of the high explosive PETN (pentaerythritol tetranitrate) up to 500-μm thick have been deposited through physical vapor deposition, with the intent of creating well-defined samples for shock-initiation studies. PETN films were characterized with surface profilometry, scanning electron microscopy, x-ray diffraction, and focused ion beam nanotomography. These high-density films were subjected to strong shocks in both the in-plane and out-of-plane orientations. Initiation behavior was monitored with high-speed framing and streak camera photography. Direct initiation with a donor explosive (either RDX with binder, or CL-20 with binder) was possible in both orientations, but with the addition of a thin aluminum buffer plate (in-plane configuration only), initiation proved to be difficult due to the attenuated shock and the high density of the PETN films. Mesoscale models of microenergetic samples were created using the shock physics code CTH and compared with experimental results. The results of these experiments will be discussed in the context of small sample geometry, deposited film morphology, and density.

Effect of Pressure Gradients on the Initiation of PBX-9502 via Irregular (Mach) Reflection of Low Pressure Curved Shock Waves

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hull, Lawrence Mark; Miller, Phillip Isaac; Moro, Erik Allan

In the instance of multiple fragment impact on cased explosive, isolated curved shocks are generated in the explosive. These curved shocks propagate and may interact and form irregular or Mach reflections along the interaction loci, thereby producing a single shock that may be sufficient to initiate PBX-9501. However, the incident shocks are divergent and their intensity generally decreases as they expand, and the regions behind the Mach stem interaction loci are generally unsupported and allow release waves to rapidly affect the flow. The effects of release waves and divergent shocks may be considered theoretically through a “Shock Change Equation”.

Expansion shock waves in regularized shallow-water theory

NASA Astrophysics Data System (ADS)

El, Gennady A.; Hoefer, Mark A.; Shearer, Michael

2016-05-01

We identify a new type of shock wave by constructing a stationary expansion shock solution of a class of regularized shallow-water equations that include the Benjamin-Bona-Mahony and Boussinesq equations. An expansion shock exhibits divergent characteristics, thereby contravening the classical Lax entropy condition. The persistence of the expansion shock in initial value problems is analysed and justified using matched asymptotic expansions and numerical simulations. The expansion shock's existence is traced to the presence of a non-local dispersive term in the governing equation. We establish the algebraic decay of the shock as it is gradually eroded by a simple wave on either side. More generally, we observe a robustness of the expansion shock in the presence of weak dissipation and in simulations of asymmetric initial conditions where a train of solitary waves is shed from one side of the shock.

Success and failure of the defibrillation shock: insights from a simulation study.

PubMed

Skouibine, K; Trayanova, N; Moore, P

2000-07-01

This simulation study presents a further inquiry into the mechanisms by which a strong electric shock fails to halt life-threatening cardiac arrhythmias. The research uses a model of the defibrillation process that represents a sheet of myocardium as a bidomain. The tissue consists of nonuniformly curved fibers in which spiral wave reentry is initiated. Monophasic defibrillation shocks are delivered via two line electrodes that occupy opposite tissue boundaries. In some simulation experiments, the polarity of the shock is reversed. Electrical activity in the sheet is compared for failed and successful shocks under controlled conditions. The maps of transmembrane potential and activation times calculated during and after the shock demonstrate that weak shocks fail to terminate the reentrant activity via two major mechanisms. As compared with strong shocks, weak shocks result in (1) smaller extension of refractoriness in the areas depolarized by the shock, and (2) slower or incomplete activation of the excitable gap created by deexcitation of the negatively polarized areas. In its turn, mechanism 2 is associated with one or more of the following events: (a) lack of some break excitations, (b) latency in the occurrence of the break excitations, and (c) slower propagation through deexcited areas. Reversal of shock polarity results in a change of the extent of the regions of deexcitation, and thus, in a change in defibrillation threshold. The results of this study indicate the paramount importance of shock-induced deexcitation in both defibrillation and postshock arrhythmogenesis.

NQR Line Broadening Due to Crystal Lattice Imperfections and Its Relationship to Shock Sensitivity

NASA Astrophysics Data System (ADS)

Caulder, S. M.; Buess, M. L.; Garroway, A. N.; Miller, P. J.

2004-07-01

The hydrodynamic hot spot model is used to explain the difference between shock sensitive and shock insensitive explosives. Among the major factors that influence the shock sensitivity of energetic compounds are the quality and particle size of the energetic crystals used to formulate the cast plastic bonded explosive. As do all energetic compounds, RDX and HMX exhibit internal crystal defects the magnitude and type of which depend on the manufacturing process used to synthesize and re-crystallize the energetic compound. Nuclear Quadrupole Resonance (NQR) spectroscopy was used to determine the crystal quality of RDX, HMX and CL-20 obtained from various manufacturers. The NQR experimental results are discussed. Cast plastic bonded explosives were made using the RDX and HMX obtained from the various manufacturers and subsequently subjected to the NOL large-scale gap test (LSGT). The results of the LSGT are discussed and correlated with the NQR results. A relationship between the crystal defect density and shock initiation pressure of the plastic bonded explosive is developed and discussed.

32-channel pyrometer with high dynamic range for studies of shocked nanothermites

NASA Astrophysics Data System (ADS)

Bassett, Will P.; Dlott, Dana D.

2017-01-01

A 32-channel optical pyrometer has been developed for studying temperature dynamics of shock-initiated reactive materials with one nanosecond time resolution and high dynamic range. The pyrometer consists of a prism spectrograph which directs the spectrally-resolved emission to 32 fiber optics and 32 photomultiplier tubes and digitizers. Preliminary results show shock-initiated reactions of a nanothermite composite, nano CuO/Al in nitrocellulose binder, consists of three stages. The first stage occurred at 30 ns, right after the shock unloaded, the second stage at 100 ns and the third at 1 μs, and the temperatures ranged from 2100K to 3000K. Time-resolved emission spectra suggest hot spots formed during shock unloading, which initiated the bulk thermite/nitrocellulose reaction.

Numerical study of heterogeneous mean temperature and shock wave in a resonator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yano, Takeru

2015-10-28

When a frequency of gas oscillation in an acoustic resonator is sufficiently close to one of resonant frequencies of the resonator, the amplitude of gas oscillation becomes large and hence the nonlinear effect manifests itself. Then, if the dissipation effects due to viscosity and thermal conductivity of the gas are sufficiently small, the gas oscillation may evolve into the acoustic shock wave, in the so-called consonant resonators. At the shock front, the kinetic energy of gas oscillation is converted into heat by the dissipation process inside the shock layer, and therefore the temperature of the gas in the resonator rises.more » Since the acoustic shock wave travels in the resonator repeatedly over and over again, the temperature rise becomes noticeable in due course of time even if the shock wave is weak. We numerically study the gas oscillation with shock wave in a resonator of square cross section by solving the initial and boundary value problem of the system of three-dimensional Navier-Stokes equations with a finite difference method. In this case, the heat conduction across the boundary layer on the wall of resonator causes a spatially heterogeneous distribution of mean (time-averaged) gas temperature.« less

Shock Initiation and Equation of State of Ammonium Nitrate

NASA Astrophysics Data System (ADS)

Robbins, David; Sheffield, Steve; Dattelbaum, Dana; Chellappa, Raja; Velisavljevic, Nenad

2013-06-01

Ammonium nitrate (AN) is a widely used fertilizer and mining explosive commonly found in ammonium nitrate-fuel oil. Neat AN is a non-ideal explosive with measured detonation velocities approaching 4 km/s. Previously, we reported a thermodynamically-complete equation of state for AN based on its maximum density, and showed that near-full density AN did not initiate when subjected to shock input conditions up to 22 GPa. In this work, we extend these initial results, by presenting new Hugoniot data for intermediate density neat AN obtained from gas gun-driven plate impact experiments. AN at densities from 1.8 to 1.5 g/cm3 were impacted into LiF windows using a two-stage light gas gun. Dual VISARs were used to measure the interfacial particle velocity wave profile as a function of time following impact. The new Hugoniot data, in addition to updates to thermodynamic parameters derived from structural analysis and vibrational spectroscopy measurements in high pressure diamond anvil cell experiments, are used to refine the unreacted EOS for AN. Furthermore, shock initiation of neat AN was observed as the initial porosity increased (density decreased). Insights into the relationship(s) between initial density and shock initiation sensitivity are also presented, from evidence of shock initiation in the particle velocity profiles obtained for the lower density AN samples.

On the interplay between cosmological shock waves and their environment

NASA Astrophysics Data System (ADS)

Martin-Alvarez, Sergio; Planelles, Susana; Quilis, Vicent

2017-05-01

Cosmological shock waves are tracers of the thermal history of the structures in the Universe. They play a crucial role in redistributing the energy within the cosmic structures and are also amongst the main ingredients of galaxy and galaxy cluster formation. Understanding this important function requires a proper description of the interplay between shocks and the different environments where they can be found. In this paper, an Adaptive Mesh Refinement (AMR) Eulerian cosmological simulation is analysed by means of a shock-finding algorithm that allows to generate shock wave maps. Based on the population of dark matter halos and on the distribution of density contrast in the simulation, we classify the shocks in five different environments. These range from galaxy clusters to voids. The shock distribution function and the shocks power spectrum are studied for these environments dynamics. We find that shock waves on different environments undergo different formation and evolution processes, showing as well different characteristics. We identify three different phases of formation, evolution and dissipation of these shock waves, and an intricate migration between distinct environments and scales. Shock waves initially form at external, low density regions and are merged and amplified through the collapse of structures. Shock waves and cosmic structures follow a parallel evolution. Later on, shocks start to detach from them and dissipate. We also find that most of the power that shock waves dissipate is found at scales of k ˜0.5 Mpc^{-1}, with a secondary peak at k ˜8 Mpc^{-1}. The evolution of the shocks power spectrum confirms that shock waves evolution is coupled and conditioned by their environment.

Impact and collisional processes in the solar system

NASA Technical Reports Server (NTRS)

Ahrens, Thomas J.; Gazis, C.; Pepin, R.; Becker, R.; Cronin, R.; Tyburczy, J.; Tingle, T.; Duffy, T.; Rowan, L.

1991-01-01

As impact cratered terrains have been successively recognized on certain planets and planetary satellites, it has become clear that impact processes are important to the understanding of the accretion and evolution of all solid planets. The noble gases in the normalized atmospheric inventories of the planets and the normalized gas content of meteorites are grossly similar, but demonstrate differences from each other which are not understood. In order to study shock devolatilization of the candidate carrier phases which are principally thought to be carbonaceous or hydrocarbons in planetesimals, experiments were conducted on noble gase implantation in various carbons: carbon black, activated charcoal, graphite, and carbon glass. These were candidate starting materials for impact devolatilization experiments. Initial experiments were conducted on vitreous amorphous carbon samples which were synthesized under vapor saturated conditions using argon as the pressurizing medium. An amino acid and surface analysis by laser ionization analyses were performed on three samples of shocked Murchison meteorite. A first study was completed in which a series of shock loading experiments on a porous limestone and on a non-porous gabbro in one and three dimensions were performed. Also a series of recovery experiments were conducted in which shocked molten basalt a 1700 C is encapsulated in molybdenum containers and shock recovered from up to 6 GPa pressures.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yarrington, Cole D.; Wixom, Ryan R.; Damm, David L.

The complex physical phenomenon of shock wave interaction with material heterogeneities has significant importance and nevertheless remains little understood. In many materials, the observed macroscale response to shock loading is governed by characteristics of the microstructure. Yet the majority of computational studies aimed at predicting phenomena affected by these processes, such as initiation and propagation of detonation waves in explosives, or shock propagation in geological materials, employ continuum material and reactive burn model treatment. In an effort to highlight the grain-scale processes that underlie the observable effects in an energetic system, a grain-scale model for hexanitrostilbene (HNS) has been developed.more » Measured microstructures were used to produce synthetic computational representations of the pore structure, and a density functional theory molecular dynamics (DFT-MD) derived equation of state (EOS) was used for the fully dense HNS matrix. The explicit inclusion of microstructure along with a fully-dense EOS resulted in close agreement with historical shock compression experiments. More recent experiments on dynamic reaction threshold were also reproduced by inclusion of a global kinetics model. The complete model was shown to reproduce accurately the expected response of this heterogeneous material to shock loading. Mesoscale simulations were shown to provide clear insight into the nature of threshold behavior, and are a way to understand complex physical phenomena.« less

Cellular automaton model for molecular traffic jams

NASA Astrophysics Data System (ADS)

Belitsky, V.; Schütz, G. M.

2011-07-01

We consider the time evolution of an exactly solvable cellular automaton with random initial conditions both in the large-scale hydrodynamic limit and on the microscopic level. This model is a version of the totally asymmetric simple exclusion process with sublattice parallel update and thus may serve as a model for studying traffic jams in systems of self-driven particles. We study the emergence of shocks from the microscopic dynamics of the model. In particular, we introduce shock measures whose time evolution we can compute explicitly, both in the thermodynamic limit and for open boundaries where a boundary-induced phase transition driven by the motion of a shock occurs. The motion of the shock, which results from the collective dynamics of the exclusion particles, is a random walk with an internal degree of freedom that determines the jump direction. This type of hopping dynamics is reminiscent of some transport phenomena in biological systems.

Expansion shock waves in regularized shallow-water theory

PubMed Central

El, Gennady A.; Shearer, Michael

2016-01-01

We identify a new type of shock wave by constructing a stationary expansion shock solution of a class of regularized shallow-water equations that include the Benjamin–Bona–Mahony and Boussinesq equations. An expansion shock exhibits divergent characteristics, thereby contravening the classical Lax entropy condition. The persistence of the expansion shock in initial value problems is analysed and justified using matched asymptotic expansions and numerical simulations. The expansion shock's existence is traced to the presence of a non-local dispersive term in the governing equation. We establish the algebraic decay of the shock as it is gradually eroded by a simple wave on either side. More generally, we observe a robustness of the expansion shock in the presence of weak dissipation and in simulations of asymmetric initial conditions where a train of solitary waves is shed from one side of the shock. PMID:27279780

Analysis of compaction shock interactions during DDT of low density HMX

NASA Astrophysics Data System (ADS)

Rao, Pratap T.; Gonthier, Keith A.

2017-01-01

Deflagration-to-Detonation Transition (DDT) in confined, low density granular HMX occurs by a complex mechanism that involves compaction shock interactions within the material. Piston driven DDT experiments indicate that detonation is abruptly triggered by the interaction of a strong combustion-supported secondary shock and a piston-supported primary (input) shock, where the nature of the interaction depends on initial packing density and primary shock strength. These interactions influence transition by affecting dissipative heating within the microstructure during pore collapse. Inert meso-scale simulations of successive shock loading of low density HMX are performed to examine how dissipation and hot-spot formation are affected by the initial density, and the primary and secondary shock strengths. This information is used to formulate an ignition and burn model for low density HMX that accounts for the effect of shock densensitization on burn. Preliminary DDT predictions are presented that illustrate how primary shock strength affects the transition mechanism.

Criticality conditions of heterogeneous energetic materials under shock loading

NASA Astrophysics Data System (ADS)

Nassar, Anas; Rai, Nirmal Kumar; Sen, Oishik; Udaykumar, H. S.

2017-06-01

Shock interaction with the microstructural heterogeneities of energetic materials can lead to the formation of locally heated regions known as hot spots. These hot spots are the potential sites where chemical reaction may be initiated. However, the ability of a hot spot to initiate chemical reaction depends on its size, shape and strength (temperature). Previous study by Tarver et al. has shown that there exists a critical size and temperature for a given shape (spherical, cylindrical, and planar) of the hot spot above which reaction initiation is imminent. Tarver et al. assumed a constant temperature variation in the hot spot. However, the meso-scale simulations show that the temperature distribution within a hot spot formed from processes such as void collapse is seldom constant. Also, the shape of a hot spot can be arbitrary. This work is an attempt towards development of a critical hot spot curve which is a function of loading strength, duration and void morphology. To achieve the aforementioned goal, mesoscale simulations are conducted on porous HMX material. The process is repeated for different loading conditions and void sizes. The hot spots formed in the process are examined for criticality depending on whether they will ignite or not. The metamodel is used to obtain criticality curves and is compared with the critical hot spot curve of Tarver et al.

Pyrotechnic shock at the orbiter/external tank forward attachment

NASA Technical Reports Server (NTRS)

Rogers, W. F.; Grissom, D. S.; Rhodes, L. R.

1980-01-01

During the initial certification test of the forward structural attachment of the space shuttle orbiter to the external tank, pyrotechnic shock from actuation of the separation device resulted in structural failure of the thermal protection tiles surrounding the attachment. Because of the high shock associated with the separation bolt, the development of alternative low shock separation designs was initiated. Two concepts that incorporate a 5.08 centimeter frangible nut as the release device were developed and tested.

Evaluation of Straight and Swept Ramp Obstacles on Enhancing Deflagration-to-Detonation Transition in Pulse Detonation Engines

DTIC Science & Technology

2006-12-01

models attempted to bracket the extremes of the conditions of interest. These conditions were Mach 2 and Mach 3 shocks , with initial medium...later, but all traces have been expanded to the area of interest. Pressure readings were primarily used to measure shock speeds, and initially used...results for the clean tube configuration. The characteristics of the initial shock are similar, and are comparable for all configurations tested

Cavitation-induced fragmentation of an acoustically-levitated droplet

NASA Astrophysics Data System (ADS)

Gonzalez Avila, Silvestre Roberto; Ohl, Claus-Dieter

2015-12-01

In this paper we investigate the initial sequence of events that lead to the fragmentation of a millimetre sized water droplets when interacting with a focused ns-laser pulse. The experimental results show complex processes that result from the reflection of an initial shock wave from plasma generation with the soft boundary of the levitating droplet; furthermore, when the reflected waves from the walls of the droplet refocus they leave behind a trail of microbubbles that later act as cavitation inception regions. Numerical simulations of a shock wave impacting and reflecting from a soft boundary are also reported; the simulated results show that the lowest pressure inside the droplet occurs at the equatorial plane. The results of the numerical model display good agreement with the experimental results both in time and in space.

Explosive-induced shock damage in copper and recompression of the damaged region

DOE PAGES

Turley, William D.; Stevens, Gerald D.; Hixson, Robert Stewart; ...

2016-08-31

Here, we have studied the dynamic spall process for copper samples in contact with detonating low-performance explosives. When a triangular shaped shock wave from detonation moves through a sample and reflects from the free surface, tension develops immediately, one or more damaged layers can form, and a spall scab can separate from the sample and move ahead of the remaining target material. For dynamic experiments, we used time-resolved velocimetry and x-ray radiography. Soft-recovered samples were analyzed using optical imaging and microscopy. Computer simulations were used to guide experiment design. We observe that for some target thicknesses the spall scab continuesmore » to run ahead of the rest of the sample, but for thinner samples, the detonation product gases accelerate the sample enough for it to impact the spall scab several microseconds or more after the initial damage formation. Our data also show signatures in the form of a late-time reshock in the time-resolved data, which support this computational prediction. A primary goal of this research was to study the wave interactions and damage processes for explosives-loaded copper and to look for evidence of this postulated recompression event. We found both experimentally and computationally that we could tailor the magnitude of the initial and recompression shocks by varying the explosive drive and the copper sample thickness; thin samples had a large recompression after spall, whereas thick samples did not recompress at all. Samples that did not recompress had spall scabs that completely separated from the sample, whereas samples with recompression remained intact. This suggests that the hypothesized recompression process closes voids in the damage layer or otherwise halts the spall formation process. This is a somewhat surprising and, in some ways controversial, result, and the one that warrants further research in the shock compression community.« less

Explosive-induced shock damage in copper and recompression of the damaged region

DOE Office of Scientific and Technical Information (OSTI.GOV)

Turley, William D.; Stevens, Gerald D.; Hixson, Robert Stewart

Here, we have studied the dynamic spall process for copper samples in contact with detonating low-performance explosives. When a triangular shaped shock wave from detonation moves through a sample and reflects from the free surface, tension develops immediately, one or more damaged layers can form, and a spall scab can separate from the sample and move ahead of the remaining target material. For dynamic experiments, we used time-resolved velocimetry and x-ray radiography. Soft-recovered samples were analyzed using optical imaging and microscopy. Computer simulations were used to guide experiment design. We observe that for some target thicknesses the spall scab continuesmore » to run ahead of the rest of the sample, but for thinner samples, the detonation product gases accelerate the sample enough for it to impact the spall scab several microseconds or more after the initial damage formation. Our data also show signatures in the form of a late-time reshock in the time-resolved data, which support this computational prediction. A primary goal of this research was to study the wave interactions and damage processes for explosives-loaded copper and to look for evidence of this postulated recompression event. We found both experimentally and computationally that we could tailor the magnitude of the initial and recompression shocks by varying the explosive drive and the copper sample thickness; thin samples had a large recompression after spall, whereas thick samples did not recompress at all. Samples that did not recompress had spall scabs that completely separated from the sample, whereas samples with recompression remained intact. This suggests that the hypothesized recompression process closes voids in the damage layer or otherwise halts the spall formation process. This is a somewhat surprising and, in some ways controversial, result, and the one that warrants further research in the shock compression community.« less

Explosive-induced shock damage in copper and recompression of the damaged region

DOE Office of Scientific and Technical Information (OSTI.GOV)

Turley, W. D., E-mail: turleywd@nv.doe.gov; Stevens, G. D.; La Lone, B. M.

We have studied the dynamic spall process for copper samples in contact with detonating low-performance explosives. When a triangular shaped shock wave from detonation moves through a sample and reflects from the free surface, tension develops immediately, one or more damaged layers can form, and a spall scab can separate from the sample and move ahead of the remaining target material. For dynamic experiments, we used time-resolved velocimetry and x-ray radiography. Soft-recovered samples were analyzed using optical imaging and microscopy. Computer simulations were used to guide experiment design. We observe that for some target thicknesses the spall scab continues tomore » run ahead of the rest of the sample, but for thinner samples, the detonation product gases accelerate the sample enough for it to impact the spall scab several microseconds or more after the initial damage formation. Our data also show signatures in the form of a late-time reshock in the time-resolved data, which support this computational prediction. A primary goal of this research was to study the wave interactions and damage processes for explosives-loaded copper and to look for evidence of this postulated recompression event. We found both experimentally and computationally that we could tailor the magnitude of the initial and recompression shocks by varying the explosive drive and the copper sample thickness; thin samples had a large recompression after spall, whereas thick samples did not recompress at all. Samples that did not recompress had spall scabs that completely separated from the sample, whereas samples with recompression remained intact. This suggests that the hypothesized recompression process closes voids in the damage layer or otherwise halts the spall formation process. This is a somewhat surprising and, in some ways controversial, result, and the one that warrants further research in the shock compression community.« less

Direct Comparisons of the Size and Persistence of Anisomycin-Induced Consolidation and Reconsolidation Deficits

ERIC Educational Resources Information Center

Stafford, James M.; Lattal, K. Matthew

2009-01-01

An issue of increasing theoretical interest in the study of learning is to compare the processes that follow an initial learning experience (such as learning an association between a context and a shock; memory consolidation processes) with those that follow retrieval of that learning experience (such as exposure to the context in the absence of…

Observations of impact-induced molten metal-silicate partitioning

NASA Technical Reports Server (NTRS)

Rowan, Linda R.; Ahrens, Thomas J.

1994-01-01

Observations of molten mid-ocean ridge basalt (MORB)-molybdenum (Mo) interactions produced by shock experiments provide insight into impact and differentiation processes involving metal-silicate partitioning. Analysis of fragments recovered from experiments (achieving MORB liquid shock pressures from 0.8 to 6 GPa) revealed significant changes in the composition of the MORB and Mo due to reaction of the silicate and metal liquids on a short time scale (less than 13 s). The FeO concentration of the shocked liquid decreases systematically with increasing pressure. In fact, the most highly shocked liquid (6 GPa) contains only 0.1 wt% FeO compared to an initial concentration of 9 wt% in the MORB. We infer from the presence of micrometer-sized Fe-, Si- and Mo-rich metallic spheres in the shocked glass that the Fe and Si oxides in the MORB were reduced in an estimated oxygen fugacity of 10(exp -17) bar and subsequently alloyed with the Mo. The in-situ reduction of FeO in the shocked molten basalt implies that shock-induced reduction of impact melt should be considered a viable mechanism for the formation of metallic phases. Similar metallic phases may form during impact accretion of planets and in impacted material found on the lunar surface and near terrestrial impact craters. In particular, the minute, isolated Fe particles found in lunar soils may have formed by such a process. Furthermore, the metallic spheres within the shocked glass have a globular texture similar to the textures of metallic spheroids from lunar samples and the estimated, slow cooling rate of less than or equal to 140 C/s for our spheres is consistent with the interpretation that the lunar spheroids formed by slow cooling within a melted target.

Experiments and simulations of single shock Richtmeyer-Meshkov Instability with measured, volumetric initial conditions

NASA Astrophysics Data System (ADS)

Sewell, Everest; Ferguson, Kevin; Greenough, Jeffrey; Jacobs, Jeffrey

2014-11-01

We describe new experiments of single shock Richtmeyer-Meshkov Instability (RMI) performed on the shock tube apparatus at the University of Arizona in which the initial conditions are volumetrically imaged prior to shock wave arrival. Initial perturbation plays a major role in the evolution of RMI, and previous experimental efforts only capture a narrow slice of the initial condition. The method presented uses a rastered laser sheet to capture additional images in the depth of the initial condition shortly before the experimental start time. These images are then used to reconstruct a volumetric approximation of the experimental perturbation, which is simulated using the hydrodynamics code ARES, developed at Lawrence Livermore National Laboratory (LLNL). Comparison is made between the time evolution of the interface width and the mixedness ratio measured from the experiments against the predictions from the numerical simulations.

Early afterglows in wind environments revisited

NASA Astrophysics Data System (ADS)

Zou, Y. C.; Wu, X. F.; Dai, Z. G.

2005-10-01

When a cold shell sweeps up the ambient medium, a forward shock and a reverse shock will form. We analyse the reverse-forward shocks in a wind environment, including their dynamics and emission. An early afterglow is emitted from the shocked shell, e.g. an optical flash may emerge. The reverse shock behaves differently in two approximations: the relativistic and Newtonian cases, which depend on the parameters, e.g. the initial Lorentz factor of the ejecta. If the initial Lorentz factor is much less than 114E1/453Δ-1/40,12A-1/4*,-1, the early reverse shock is Newtonian. This may take place for the wider of a two-component jet, an orphan afterglow caused by a low initial Lorentz factor and so on. The synchrotron self-absorption effect is significant especially for the Newtonian reverse shock case, as the absorption frequency νa is larger than the cooling frequency νc and the minimum synchrotron frequency νm for typical parameters. For the optical to X-ray band, the flux is nearly unchanged with time during the early period, which may be a diagnostic for the low initial Lorentz factor of the ejecta in a wind environment. We also investigate the early light curves with different wind densities and compare them with those in the interstellar medium model.

Simulation of Richtmyer-Meshkov flows for elastic-plastic solids in planar and converging geometries using an Eulerian framework

NASA Astrophysics Data System (ADS)

Lopez Ortega, Alejandro

This thesis presents a numerical and analytical study of two problems of interest involving shock waves propagating through elastic-plastic media: the motion of converging (imploding) shocks and the Richtmyer-Meshkov (RM) instability. Since the stress conditions encountered in these cases normally produce large deformations in the materials, an Eulerian description, in which the spatial coordinates are fixed, is employed. This formulation enables a direct comparison of similarities and differences between the present study of phenomena driven by shock-loading in elastic-plastic solids, and in fluids, where they have been studied extensively. In the first application, Whitham's shock dynamics (WSD) theory is employed for obtaining an approximate description of the motion of an elastic-plastic material processed by a cylindrically/spherically converging shock. Comparison with numerical simulations of the full set of equations of motion reveal that WSD is an accurate tool for characterizing the evolution of converging shocks at all stages. The study of the Richtmyer-Meshkov flow (i.e., interaction between the interface separating two materials of different density and a shock wave incoming at an angle) in solids is performed by means of analytical models for purely elastic solids and numerical simulations when plasticity is included in the material model. To this effect, an updated version of a previously developed multi-material, level-set-based, Eulerian framework for solid mechanics is employed. The revised code includes the use of a multi-material HLLD Riemann problem for imposing material boundary conditions, and a new formulation of the equations of motion that makes use of the stretch tensor while avoiding the degeneracy of the stress tensor under rotation. Results reveal that the interface separating two elastic solids always behaves in a stable oscillatory or decaying oscillatory manner due to the existence of shear waves, which are able to transport the initial vorticity away from the interface. In the case of elastic-plastic materials, the interface behaves at first in an unstable manner similar to a fluid. Ejecta formation is appreciated under certain initial conditions while in other conditions, after an initial period of growth, the interface displays a quasi-stationary long-term behavior due to stress relaxation. The effect of secondary shock-interface interactions (re-shocks) in converging geometries is also studied. A turbulent mixing zone, similar to what is observed in gas--gas interfaces, is created, especially when materials with low strength driven by moderate to strong shocks are considered.

Investigate the shock focusing under a single vortex disturbance using 2D Saint-Venant equations with a shock-capturing scheme

NASA Astrophysics Data System (ADS)

Zhao, Jiaquan; Li, Renfu; Wu, Haiyan

2018-02-01

In order to characterize the flow structure and the effect of acoustic waves caused by the shock-vortex interaction on the performance of the shock focusing, the incident plane shock wave with a single disturbance vortex focusing in a parabolic cavity is simulated systematically through solving the two-dimensional, unsteady Saint-Venant equations with the two order HLL scheme of Riemann solvers. The simulations show that the dilatation effect to be dominant in the net vorticity generation, while the baroclinic effect is dominate in the absence of initial vortex disturbance. Moreover, the simulations show that the time evolution of maximum focusing pressure with initial vortex is more complicate than that without initial vortex, which has a lot of relevance with the presence of quadrupolar acoustic wave structure induced by shock-vortex interaction and its propagation in the cavity. Among shock and other disturbance parameters, the shock Mach number, vortex Mach number and the shape of parabolic reflector proved to play a critical role in the focusing of shock waves and the strength of viscous dissipation, which in turn govern the evolution of maximum focusing pressure due to the gas dynamic focus, the change in dissipation rate and the coincidence of motion disturbance vortex with aerodynamic focus point.

Coherent Raman Studies of Shocked Liquids

NASA Astrophysics Data System (ADS)

McGrane, Shawn; Brown, Kathryn; Dang, Nhan; Bolme, Cynthia; Moore, David

2013-06-01

Transient vibrational spectroscopies offer the potential to directly observe time dependent shock induced chemical reaction kinetics. We report recent experiments that couple a hybrid picosecond/femtosecond coherent anti-Stokes Raman spectroscopy (CARS) diagnostic with our tabletop ultrafast laser driven shock platform. Initial results on liquids shocked to 20 GPa suggest that sub-picosecond dephasing at high pressure and temperature may limit the application of this nonresonant background free version of CARS. Initial results using interferometric CARS to increase sensitivity and overcome these limitations will be presented.

Shock loading and release behavior of silicon nitride

NASA Astrophysics Data System (ADS)

Kawai, Nobuaki; Tsuru, Taiki; Hidaka, Naoto; Liu, Xun; Mashimo, Tsutomu

2015-06-01

Shock-reshock and shock-release experiments were performed on silicon nitride ceramics above and below its phase transition pressure. Experimental results clearly show the occurrence of elastic-plastic transition and phase transition during initial shock loading. The HEL and phase transition stress are determined as 11.6 GPa and 34.5 GPa, respectively. Below the phase transition point, the reshock profile consists of the single shock with short rise time, while the release profile shows the gradual release followed by more rapid one. Above the phase transition point, reshock and release behavior varies with the initial shock stress. In the case of reshock and release from about 40 GPa, the reshock structure is considerably dispersed, while the release structure shows rapid release. In the reshock profile from about 50 GPa, the formation of the shock wave with the small ramped precursor is observed. And, the release response from same condition shows initial gradual release and subsequent quite rapid one. These results would provide the information about how phase transformation kinetics effects on the reshock and release behavior.

Super- and sub-critical regions in shocks driven by radio-loud and radio-quiet CMEs

PubMed Central

Bemporad, Alessandro; Mancuso, Salvatore

2012-01-01

White-light coronagraphic images of Coronal Mass Ejections (CMEs) observed by SOHO/LASCO C2 have been used to estimate the density jump along the whole front of two CME-driven shocks. The two events are different in that the first one was a “radio-loud” fast CME, while the second one was a “radio quiet” slow CME. From the compression ratios inferred along the shock fronts, we estimated the Alfvén Mach numbers for the general case of an oblique shock. It turns out that the “radio-loud” CME shock is initially super-critical around the shock center, while later on the whole shock becomes sub-critical. On the contrary, the shock associated with the “radio-quiet” CME is sub-critical at all times. This suggests that CME-driven shocks could be efficient particle accelerators at the shock nose only at the initiation phases of the event, if and when the shock is super-critical, while at later times they lose their energy and the capability to accelerate high energetic particles. PMID:25685431

Working mechanism of extracorporeal shockwave therapy in non-urological disciplines

NASA Astrophysics Data System (ADS)

Schaden, Wolfgang

2005-04-01

For 32 years of extracorporeal shockwave lithotripsy (ESWL) only the mechanical strength of shockwaves were of clinical interest. For use in orthopaedics, the absence of dangerous long term effects (malignant degeneration, etc.) is the only important message. The mechanical model tries to explain the effect of shock waves by the provocation of microleasions in the tissue stimulating repairing processes. First doubts on this mechanical model came up when Schaden (2001) could show, that less energy is more efficient in the treatment of non-unions. Due to the basic research of the last years knowledge increased about the microbiological effects. Under the influence of shock waves the change of permeability of cell membranes and the liberation of free radicals was reported. Also the production of nitric oxide (NO) and different growth factors like vascular endothelial growth factor (VEGF), bone morphogenetic proteins (BMP), transforming growth factor-beta 1 (TGF-b1), insulin-like growth factor-I (IGF-I) etc. was observed. The biological model tries to explain the effect of shock waves by stimulating the ingrowth of blood vessels and liberation of growth factors. Under the influence of shock waves, biological tissues seem to be able to produce important substances to initiate healing processes.

Note: A contraction channel design for planar shock wave enhancement

NASA Astrophysics Data System (ADS)

Zhan, Dongwen; Li, Zhufei; Yang, Jianting; Zhu, Yujian; Yang, Jiming

2018-05-01

A two-dimensional contraction channel with a theoretically designed concave-oblique-convex wall profile is proposed to obtain a smooth planar-to-planar shock transition with shock intensity amplification that can easily overcome the limitations of a conventional shock tube. The concave segment of the wall profile, which is carefully determined based on shock dynamics theory, transforms the shock shape from an initial plane into a cylindrical arc. Then the level of shock enhancement is mainly contributed by the cylindrical shock convergence within the following oblique segment, after which the cylindrical shock is again "bent" back into a planar shape through the third section of the shock dynamically designed convex segment. A typical example is presented with a combination of experimental and numerical methods, where the shape of transmitted shock is almost planar and the post-shock flow has no obvious reflected waves. A quantitative investigation shows that the difference between the designed and experimental transmitted shock intensities is merely 1.4%. Thanks to its advantage that the wall profile design is insensitive to initial shock strength variations and high-temperature gas effects, this method exhibits attractive potential as an efficient approach to a certain, controllable, extreme condition of a strong shock wave with relatively uniform flow behind.

Building the Hot Intra-Group Medium in Spiral-Rich Compact Groups

NASA Astrophysics Data System (ADS)

O'Sullivan, Ewan

2014-11-01

Galaxy groups provide a natural laboratory for investigating the formation of the hot intergalactic medium (IGM). While galaxy clusters gain most of their hot gas through accretion and gravitational shocks, in groups the processes of galaxy evolution (stripping, collisions, star formation) play an important role in the initial build up of the hot halo. We present Chandra and XMM-Newton observations of groups still in the process of forming their IGM, including the well known compact groups HCG 16 and Stephan's Quintet (HCG 92). We show that starburst winds and shock-heating of stripped HI provide important contributions of gas and metals to the IGM, and discuss the impact of gas stripping, enhanced star formation and nuclear activity in the group member galaxies.

Turbulent mixing induced by Richtmyer-Meshkov instability

NASA Astrophysics Data System (ADS)

Krivets, V. V.; Ferguson, K. J.; Jacobs, J. W.

2017-01-01

Richtmyer-Meshkov instability is studied in shock tube experiments with an Atwood number of 0.7. The interface is formed in a vertical shock tube using opposed gas flows, and three-dimensional random initial interface perturbations are generated by the vertical oscillation of gas column producing Faraday waves. Planar Laser Mie scattering is used for flow visualization and for measurements of the mixing process. Experimental image sequences are recorded at 6 kHz frequency and processed to obtain the time dependent variation of the integral mixing layer width. Measurements of the mixing layer width are compared with Mikaelian's [1] model in order to extract the growth exponent θ where a fairly wide range of values is found varying from θ ≈ 0.2 to 0.6.

Numerical simulation of particle jet formation induced by shock wave acceleration in a Hele-Shaw cell

NASA Astrophysics Data System (ADS)

Osnes, A. N.; Vartdal, M.; Pettersson Reif, B. A.

2018-05-01

The formation of jets from a shock-accelerated cylindrical shell of particles, confined in a Hele-Shaw cell, is studied by means of numerical simulation. A number of simulations have been performed, systematically varying the coupling between the gas and solid phases in an effort to identify the primary mechanism(s) responsible for jet formation. We find that coupling through drag is sufficient for the formation of jets. Including the effect of particle volume fraction and particle collisions did not alter the general behaviour, but had some influence on the length, spacing and number of jets. Furthermore, we find that the jet selection process starts early in the dispersal process, during the initial expansion of the particle layer.

Theoretical Insight into Shocked Gases

DOE Office of Scientific and Technical Information (OSTI.GOV)

Leiding, Jeffery Allen

2016-09-29

I present the results of statistical mechanical calculations on shocked molecular gases. This work provides insight into the general behavior of shock Hugoniots of gas phase molecular targets with varying initial pressures. The dissociation behavior of the molecules is emphasized. Impedance matching calculations are performed to determine the maximum degree of dissociation accessible for a given flyer velocity as a function of initial gas pressure.

Emergence of power-law scalings in shock-driven mixing transition

NASA Astrophysics Data System (ADS)

Vorobieff, Peter; Wayne, Patrick; Olmstead, Dell; Simons, Dylan; Truman, C. Randall; Kumar, Sanjay

2016-11-01

We present an experimental study of transition to turbulence due to shock-driven instability evolving on an initially cylindrical, diffuse density interface between air and a mixture of sulfur hexafluoride (SF6) and acetone. The plane of the shock is at an initial angle θ with the axis of the heavy-gas cylinder. We present the cases of planar normal (θ = 0) and oblique (θ =20°) shock interaction with the initial conditions. Flow is visualized in two perpendicular planes with planar laser-induced fluorescence (PLIF) triggered in acetone with a pulsed ultraviolet laser. Statistics of the flow are characterized in terms of the second-order structure function of the PLIF intensity. As instabilities in the flow evolve, the structure functions begin to develop power-law scalings, at late times manifesting over a range of scales spanning more than two orders of magnitude. We discuss the effects of the initial conditions on the emergence of these scalings, comparing the fully three-dimensional case (oblique shock interaction) with the quasi-two-dimensional case (planar normal shock interaction). We also discuss the flow anisotropy apparent in statistical differences in data from the two visualization planes. This work is funded by NNSA Grant DE-NA0002913.

High-Order Shock-Capturing Methods for Modeling Dynamics of the Solar Atmosphere

NASA Technical Reports Server (NTRS)

Bryson, Steve; Kosovichev, Alexander; Levy, Doron

2004-01-01

We use one-dimensional high-order central shock capturing numerical methods to study the response of various model solar atmospheres to forcing at the solar surface. The dynamics of the atmosphere is modeled with the Euler equations in a variable-sized flux tube in the presence of gravity. We study dynamics of the atmosphere suggestive of spicule formation and coronal oscillations. These studies are performed on observationally-derived model atmospheres above the quiet sun and above sunspots. To perform these simulations, we provide a new extension of existing second- and third- order shock-capturing methods to irregular grids. We also solve the problem of numerically maintaining initial hydrostatic balance via the introduction of new variables in the model equations and a careful initialization mechanism. We find several striking results: all model atmospheres respond to a single impulsive perturbation with several strong shock waves consistent with the rebound-shock model. These shock waves lift material and the transition region well into the initial corona, and the sensitivity of this lift to the initial impulse depends non-linearly on the details of the atmosphere model. We also reproduce an observed 3-minute coronal oscillation above sunspots compared to 5-minute oscillations above the quiet sun.

Ultrafast shock compression of an oxygen-balanced mixture of nitromethane and hydrogen peroxide.

PubMed

Armstrong, Michael R; Zaug, Joseph M; Grant, Christian D; Crowhurst, Jonathan C; Bastea, Sorin

2014-08-14

We apply ultrafast optical interferometry to measure the Hugoniot of an oxygen-balanced mixture of nitromethane and hydrogen peroxide (NM/HP) and compare with Hugoniot data for pure nitromethane (NM) and a 90% hydrogen peroxide/water mixture (HP), as well as theoretical predictions. We observe a 2.1% percent mean pairwise difference between the measured shockwave speed (at the measured piston speed) in unreacted NM/HP and the corresponding "universal" liquid Hugoniot, which is larger than the average standard deviation of our data, 1.4%. Unlike the Hugoniots of both HP and NM, in which measured shock speeds deviate to values greater than the unreacted Hugoniot for piston speeds larger than the respective reaction thresholds, in the NM/HP mixture we observe shock speed deviations to values lower than the unreacted Hugoniot well below the von Neumann pressure (≈28 GPa). Although the trend should reverse for high enough piston speeds, the initial behavior is unexpected. Possible explanations range from mixing effects to a complex index of refraction in the reacted solution. If this is indeed a signature of chemical initiation, it would suggest that the process may not be kinetically limited (on a ~100 ps time scale) between the initiation threshold and the von Neumann pressure.

A mesoscopic reaction rate model for shock initiation of multi-component PBX explosives.

PubMed

Liu, Y R; Duan, Z P; Zhang, Z Y; Ou, Z C; Huang, F L

2016-11-05

The primary goal of this research is to develop a three-term mesoscopic reaction rate model that consists of a hot-spot ignition, a low-pressure slow burning and a high-pressure fast reaction terms for shock initiation of multi-component Plastic Bonded Explosives (PBX). Thereinto, based on the DZK hot-spot model for a single-component PBX explosive, the hot-spot ignition term as well as its reaction rate is obtained through a "mixing rule" of the explosive components; new expressions for both the low-pressure slow burning term and the high-pressure fast reaction term are also obtained by establishing the relationships between the reaction rate of the multi-component PBX explosive and that of its explosive components, based on the low-pressure slow burning term and the high-pressure fast reaction term of a mesoscopic reaction rate model. Furthermore, for verification, the new reaction rate model is incorporated into the DYNA2D code to simulate numerically the shock initiation process of the PBXC03 and the PBXC10 multi-component PBX explosives, and the numerical results of the pressure histories at different Lagrange locations in explosive are found to be in good agreements with previous experimental data. Copyright © 2016 Elsevier B.V. All rights reserved.

Early initiation of low-dose hydrocortisone treatment for septic shock in adults: A randomized clinical trial.

PubMed

Lv, Qing-Quan; Gu, Xiao-Hua; Chen, Qi-Hong; Yu, Jiang-Quan; Zheng, Rui-Qiang

2017-12-01

Physiologic dose hydrocortisone is part of the suggested adjuvant therapies for patients with septic shock. However, the association between the corticosteroid therapy and mortality in patients with septic shock is still not clear. Some authors considered that the mortality is related to the time frame between development of septic shock and start of low dose hydrocortisone. Thus we designed a placebo-controlled, randomized clinical trial to assess the importance of early initiation of low dose hydrocortisone for the final outcome. A total of 118 patients with septic shock were recruited in the study. All eligible patients were randomized to receive hydrocortisone (n=58) or normal saline (n=60). The study medication (hydrocortisone and normal saline) was initiated simultaneously with vasopressors. The primary end-point was 28-day mortality. The secondary end-points were the reversal of shock, in-hospital mortality and the duration of ICU and hospital stay. The proportion of patients with reversal of shock was similar in the two groups (P=0.602); There were no significant differences in 28-day or hospital all-cause mortality; length of stay in the ICU or hospital between patients treated with hydrocortisone or normal saline. The early initiation of low-dose of hydrocortisone did not decrease the risk of mortality, and the length of stay in the ICU or hospital in adults with septic shock. www.clinicaltrials.govNCT02580240. Copyright © 2017 Elsevier Inc. All rights reserved.

Continuous cytokine haemoadsorption incorporated into a venoarterial ECMO circuit for the management of postcardiotomy cardiogenic and septic shock - a case report.

PubMed

Nemeth, Endre; Szigeti, Szabolcs; Varga, Tamas; Daroczi, Laszlo; Barati, Zoltan; Merkely, Bela; Gal, Janos

2018-05-01

The acute surgical treatment of infective endocarditis (IE) carries a high risk of postoperative mortality. Most complications are linked to uncontrolled sepsis and inflammatory processes. Cytokine haemoadsorption is an extracorporeal technique which has benefits reported in haemodynamic stability and inflammatory response. A 46-year-old male patient underwent emergency cardiac surgery due to progressive IE. Postcardiotomy cardiogenic shock associated with cardiac surgery required the implantation of venoarterial (VA)-ECMO. Three days later, the patient developed secondary septic shock. The novel application of continuous CytoSorb TM treatment installed in the VA-ECMO circuit is demonstrated in this case during the management of simultaneous shocks. Advanced intensive care led to an improvement in the patient's condition, which facilitated successful weaning from mechanical ventilation. However, the patient died from a new onset fulminant septic shock two months after his initial cardiac surgery. VA-ECMO is suitable for installation of the CytoSorb TM cartridge. This modality could be an option for high-volume, continuous cytokine haemoadsorption when VA-ECMO is employed without renal replacement therapy. This specific application of CytoSorb TM was safe, feasible and contributed to the optimal management of simultaneous shocks.

A composite model for a class of electric-discharge shock tubes

NASA Technical Reports Server (NTRS)

Elkins, R. T.; Baganoff, D.

1973-01-01

A gasdynamic model is presented and analyzed for a class of shock tubes that utilize both Joule heating and electromagnetic forces to produce high-speed shock waves. The model consists of several stages of acceleration in which acceleration to sonic conditions is achieved principally through heating, and further acceleration of the supersonic flow is obtained principally through use of electromagnetic forces. The utility of the model results from the fact that it predicts a quasi-steady flow process, mathematical analysis is straightforward, and it is even possible to remove one or more component stages and still have the model related to a possible shock-tube flow. Initial experiments have been performed where the electrical discharge configuration and current level were such that Joule heating was the dominant form of energy addition present. These experiments indicate that the predictions of the model dealing with heat addition correspond quite closely to reality. The experimental data together with the theory show that heat addition to the flowing driver gas after diaphragm rupture (approach used in the model) is much more effective in producing high-speed shock waves than heating the gas in the driver before diaphragm rupture, as in the case of the arc-driven shock tube.

A flyer-impact technique for measuring viscosity of metal under shock compression

NASA Astrophysics Data System (ADS)

Li, Yilei; Liu, Fusheng; Ma, Xiaojuan; Li, Yinglei; Yu, Ming; Zhang, Jichun; Jing, Fuqian

2009-01-01

A flyer-impact technique, different from the explosive method of [Sakharov et al., Sov. Phys. Dokl. 9, 1091 (1965)], is developed to investigate the viscosity of shocked metals. The shock wave with a front of sinusoidal perturbation is induced by the sinusoidal profile of the impact surface of the sample by use of two-stage light-gas gun. The oscillatory damping process of the perturbation amplitude is monitored by electric pins. Two damping curves (perturbation amplitude relative to its initial value versus propagated distance relative to the wavelength of sinusoidal perturbation) of aluminum are determined at 78 and 101 GPa. The effective shear viscosity coefficients are deduced to be about 1300 and 800 Pa s based on the Miller and Ahrens analytic solution for viscous fluid.

Liquid-surface entrainment induced by shocked air stream

NASA Astrophysics Data System (ADS)

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

2018-02-01

Recently, we experimentally studied, in a shock tube environment, shock waves propagating over horizontal free water layers having depths of 10, 20, and 30 mm for shock wave Mach numbers M_is equal to 1.1 and 1.4. The qualitative interaction process was observed by means of high-speed visualizations, and the pressures arising in the air and in the water layer were measured and interpreted in terms of the various incident and refracted shock waves in air and water; in particular, it was concluded that the compression wave in the water is driven by the planar shock wave in the air. Additional experiments have been conducted and the novel contributions of the present technical note are quantitative results regarding the liquid-surface entrainment. At low Mach number (M_is=1.1 ), we show that the velocity of the droplets ejected into the air is independent of the water depth, unlike the wavelength of initial ripples and the angle of ejection. When the shock wave strength increases (M_is=1.4 ), the dispersion of a very thin droplet mist and a single large wave take place. We show that the thickening of the water mist and the velocity of the subsequent large wave decreases with the water-layer depth.

Mechanical Properties of Shock-Damaged Rocks

NASA Technical Reports Server (NTRS)

He, Hongliang; Ahrens, T. J.

1994-01-01

Stress-strain tests were performed both on shock-damaged gabbro and limestone. The effective Young's modulus decreases with increasing initial damage parameter value, and an apparent work-softening process occurs prior to failure. To further characterize shock-induced microcracks, the longitudinal elastic wave velocity behavior of shock-damaged gabbro in the direction of compression up to failure was measured using an acoustic transmission technique under uniaxial loading. A dramatic increase in velocity was observed for the static compressive stress range of 0-50 MPa. Above that stress range, the velocity behavior of lightly damaged (D(sub 0) less than 0.1) gabbro is almost equal to unshocked gabbro. The failure strength of heavily-damaged (D(sub 0) greater than 0.1) gabbro is approx. 100-150 MPa, much lower than that of lightly damaged and unshocked gabbros (approx. 230-260 MPa). Following Nur's theory, the crack shape distribution was analyzed. The shock-induced cracks in gabbro appear to be largely thin penny-shaped cracks with c/a values below 5 x 10(exp -4). Moreover, the applicability of Ashby and Sammis's theory relating failure strength and damage parameter of shock-damaged rocks was examined and was found to yield a good estimate of the relation of shock-induced deficit in elastic modulus with the deficit in compressive strength.

Self-similar dynamic converging shocks - I. An isothermal gas sphere with self-gravity

NASA Astrophysics Data System (ADS)

Lou, Yu-Qing; Shi, Chun-Hui

2014-07-01

We explore novel self-similar dynamic evolution of converging spherical shocks in a self-gravitating isothermal gas under conceivable astrophysical situations. The construction of such converging shocks involves a time-reversal operation on feasible flow profiles in self-similar expansion with a proper care for the increasing direction of the specific entropy. Pioneered by Guderley since 1942 but without self-gravity so far, self-similar converging shocks are important for implosion processes in aerodynamics, combustion, and inertial fusion. Self-gravity necessarily plays a key role for grossly spherical structures in very broad contexts of astrophysics and cosmology, such as planets, stars, molecular clouds (cores), compact objects, planetary nebulae, supernovae, gamma-ray bursts, supernova remnants, globular clusters, galactic bulges, elliptical galaxies, clusters of galaxies as well as relatively hollow cavity or bubble structures on diverse spatial and temporal scales. Large-scale dynamic flows associated with such quasi-spherical systems (including collapses, accretions, fall-backs, winds and outflows, explosions, etc.) in their initiation, formation, and evolution are likely encounter converging spherical shocks at times. Our formalism lays an important theoretical basis for pertinent astrophysical and cosmological applications of various converging shock solutions and for developing and calibrating numerical codes. As examples, we describe converging shock triggered star formation, supernova explosions, and void collapses.

Model development of supersonic trough wind with shocks

NASA Technical Reports Server (NTRS)

Grebowsky, J. M.

1972-01-01

The time dependent one dimensional hydrodynamic equations describe the evolution of the thermal plasma flow along closed magnetic field lines outside of the plasmasphere. The convection of the supersonic polar wind onto a closed fieldline results in the assumed formation of collisionless plasma shocks. These shocks move earthward as the field line with its frozen-in plasma remains fixed or contracts with time to smaller L coordinates. The high equatorial plasma temperature (of the order of electron volts) produced by the shock process decreases with time if the flow is isothermal but it will increase if the contraction is under adiabatic conditions. Assuming adiabaticity a peak in the temperature forms at the equator in conjunction with a depression in the ion density. After an initial contraction, if the flux tube drifts to higher L coordinates the direction of the shock motion can be reversed so that the supersonic region will expand along the field line towards the state characterizing the supersonic polar wind. A rapid expansion will lower the equatorial density while the temperature decreases with time under adiabatic but not isothermal conditions.

Modeling of plasticity and fracture of metals at shock loading

NASA Astrophysics Data System (ADS)

Mayer, A. E.; Khishchenko, K. V.; Levashov, P. R.; Mayer, P. N.

2013-05-01

In this paper, we present a model of dislocation plasticity and fracture of metals, which in combination with the wide-range equation of state and the continuum mechanics equations is a necessary component for simulation of the shock-wave loading. We take into account immobilization of dislocations and nucleation of micro-voids in weakened zones of substance; this is distinguished feature of the present version of the model. Accounting of the dislocations immobilization provides a better description of the unloading wave structure, while the detailed consideration of processes in the weakened zones expands the domain of applicability of fracture model to higher strain rates. We compare our results with the experimental data for the shock loading of aluminum, copper, and nickel samples; the comparison indicates satisfactory description of the elastic precursor, unloading wave, and spall pulse. Using the model, we investigate intently the early stage of the shock formation in solids; it is found out that the elastic precursor is formed even for a strong shock wave, and initially the precursor has very large amplitude and propagation velocity.

Dislocation structure produced by an ultrashort shock pulse

DOE Office of Scientific and Technical Information (OSTI.GOV)

Matsuda, Tomoki, E-mail: t-matsu@mapse.eng.osaka-u.ac.jp; Hirose, Akio; Sano, Tomokazu

We found an ultrashort shock pulse driven by a femtosecond laser pulse on iron generates a different dislocation structure than the shock process which is on the nanosecond timescale. The ultrashort shock pulse produces a highly dense dislocation structure that varies by depth. According to transmission electron microscopy, dislocations away from the surface produce microbands via a network structure similar to a long shock process, but unlike a long shock process dislocations near the surface have limited intersections. Considering the dislocation motion during the shock process, the structure near the surface is attributed to the ultrashort shock duration. This approachmore » using an ultrashort shock pulse will lead to understanding the whole process off shock deformation by clarifying the early stage.« less

Influence of hot spot features on the shock initiation of heterogenous nitromethane

NASA Astrophysics Data System (ADS)

Dattelbaum, Dana; Sheffield, Stephen; Stahl, David; Dattelbaum, Andrew

2009-06-01

The shock initiation sensitivity of heterogeneous explosives is known to be strongly related to the confluence of ``hot spots'' or localized regions of high pressure and temperature. Physical origins of hot spots within a material include dynamic pore collapse, friction from motion along closed cracks, and wave reflections from other in situ interfaces. A complex interplay among numerous physical and chemical factors, spanning several length scales, determines whether or not a hot spot will quench or lead to initiation. To further elucidate key features of hot spots on energetic materials sensitivity and initiation mechanisms, we have intentionally introduced well-defined particles into the homogeneous liquid explosive nitromethane which has been gelled so the particles are somewhat stationary. Gas-gun driven shock initiation experiments using embedded electromagnetic gauging methods have been performed on these materials, revealing new insights into the role of heterogeneities on the sensitivity of the explosives through shock input-to-run distance relationships (Pop-plots), and reactive chemistry growth in and behind the incident shock front. By logically mapping out these relationships, the data provide a scientific foundation for the development of predictive capabilities for modeling new formulations, and designing next-generation energetic materials.

Shock experiments on maskelynite-bearing anorthosite

NASA Technical Reports Server (NTRS)

Lambert, P.; Grieve, R. A. F.

1984-01-01

A series of shock recovery experiments over 9.9-60.4 GPa have been carried out on naturally shocked anorthosite from the Mistastin impact structure in Labrador consisting primarily of diaplectic plagioclase glass or maskelynite, An(50), and pyroxene. Petrographic observations of the experimental products indicate that the component minerals and diaplectic glasses generally retained their initial character throughout, the only exception being the increase in fracturing which occurred in the 9.9 GPa shot. Reshocking at pressures higher than the initial shock tends to lower the refractive index of maskelynite. The increase in refractive index of maskelynite reshocked to pressures lower than the initial pressure is interpreted as due to shock densification of the diaplectic glass above the Hugoniot elastic limit and below the mixed phase regime. The data suggest that the low-high-low density transition of maskelynite occurs about 8 GPa below that of the crystal of corresponding composition.

Reaction Buildup of PBX Explosives JOB-9003 under Different Initiation Pressures

NASA Astrophysics Data System (ADS)

Zhang, Xu; Wang, Yan-fei; Hung, Wen-bin; Gu, Yan; Zhao, Feng; Wu, Qiang; Yu, Xin; Yu, Heng

2017-04-01

Aluminum-based embedded multiple electromagnetic particle velocity gauge technique has been developed in order to measure the shock initiation behavior of JOB-9003 explosives. In addition, another gauge element called a shock tracker has been used to monitor the progress of the shock front as a function of time, thus providing a position-time trajectory of the wave front as it moves through the explosive sample. The data are used to determine the position and time for shock to detonation transition. All the experimental results show that: the rising-up time of Al-based electromagnetic particle velocity gauge was very fast and less than 20 ns; the reaction buildup velocity profiles and the position-time for shock to detonation transition of HMX-based PBX explosive JOB-9003 with 1-8 mm depth from the origin of impact plane under different initiation pressures are obtained with high accuracy.

Use of Genetic Algorithms to solve Inverse Problems in Relativistic Hydrodynamics

NASA Astrophysics Data System (ADS)

Guzmán, F. S.; González, J. A.

2018-04-01

We present the use of Genetic Algorithms (GAs) as a strategy to solve inverse problems associated with models of relativistic hydrodynamics. The signal we consider to emulate an observation is the density of a relativistic gas, measured at a point where a shock is traveling. This shock is generated numerically out of a Riemann problem with mildly relativistic conditions. The inverse problem we propose is the prediction of the initial conditions of density, velocity and pressure of the Riemann problem that gave origin to that signal. For this we use the density, velocity and pressure of the gas at both sides of the discontinuity, as the six genes of an organism, initially with random values within a tolerance. We then prepare an initial population of N of these organisms and evolve them using methods based on GAs. In the end, the organism with the best fitness of each generation is compared to the signal and the process ends when the set of initial conditions of the organisms of a later generation fit the Signal within a tolerance.

Compaction shock dissipation in low density granular explosive

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rao, Pratap T.; Gonthier, Keith A., E-mail: gonthier@me.lsu.edu; Chakravarthy, Sunada

The microstructure of granular explosives can affect dissipative heating within compaction shocks that can trigger combustion and initiate detonation. Because initiation occurs over distances that are much larger than the mean particle size, homogenized (macroscale) theories are often used to describe local thermodynamic states within and behind shocks that are regarded as the average manifestation of thermodynamic fields at the particle scale. In this paper, mesoscale modeling and simulation are used to examine how the initial packing density of granular HMX (C{sub 4}H{sub 8}N{sub 8}O{sub 8}) C{sub 4}H{sub 8}N{sub 8}O{sub 8} having a narrow particle size distribution influences dissipation withinmore » resolved, planar compaction shocks. The model tracks the evolution of thermomechanical fields within large ensembles of particles due to pore collapse. Effective shock profiles, obtained by averaging mesoscale fields over space and time, are compared with those given by an independent macroscale compaction theory that predicts the variation in effective thermomechanical fields within shocks due to an imbalance between the solid pressure and a configurational stress. Reducing packing density is shown to reduce the dissipation rate within shocks but increase the integrated dissipated work over shock rise times, which is indicative of enhanced sensitivity. In all cases, dissipated work is related to shock pressure by a density-dependent power law, and shock rise time is related to pressure by a power law having an exponent of negative one.« less

Experimental Study of Shock-Induced Compression and Vortex Generation in the Shock-Bubble Interaction

NASA Astrophysics Data System (ADS)

Ranjan, Devesh; Motl, Bradley; Niederhaus, John; Oakley, Jason; Anderson, Mark; Bonazza, Riccardo; Greenough, Jeffrey

2006-11-01

Results are presented from experiments studying the interaction of a planar shock wave of strength 1.4

Effects of initial condition spectral content on shock-driven turbulent mixing.

PubMed

Nelson, Nicholas J; Grinstein, Fernando F

2015-07-01

The mixing of materials due to the Richtmyer-Meshkov instability and the ensuing turbulent behavior is of intense interest in a variety of physical systems including inertial confinement fusion, combustion, and the final stages of stellar evolution. Extensive numerical and laboratory studies of shock-driven mixing have demonstrated the rich behavior associated with the onset of turbulence due to the shocks. Here we report on progress in understanding shock-driven mixing at interfaces between fluids of differing densities through three-dimensional (3D) numerical simulations using the rage code in the implicit large eddy simulation context. We consider a shock-tube configuration with a band of high density gas (SF(6)) embedded in low density gas (air). Shocks with a Mach number of 1.26 are passed through SF(6) bands, resulting in transition to turbulence driven by the Richtmyer-Meshkov instability. The system is followed as a rarefaction wave and a reflected secondary shock from the back wall pass through the SF(6) band. We apply a variety of initial perturbations to the interfaces between the two fluids in which the physical standard deviation, wave number range, and the spectral slope of the perturbations are held constant, but the number of modes initially present is varied. By thus decreasing the density of initial spectral modes of the interface, we find that we can achieve as much as 25% less total mixing at late times. This has potential direct implications for the treatment of initial conditions applied to material interfaces in both 3D and reduced dimensionality simulation models.

Effects of Initial Condition Spectral Content on Shock Driven-Turbulent Mixing

DOE PAGES

Nelson, Nicholas James; Grinstein, Fernando F.

2015-07-15

The mixing of materials due to the Richtmyer-Meshkov instability and the ensuing turbulent behavior is of intense interest in a variety of physical systems including inertial confinement fusion, combustion, and the final stages of stellar evolution. Extensive numerical and laboratory studies of shock-driven mixing have demonstrated the rich behavior associated with the onset of turbulence due to the shocks. Here we report on progress in understanding shock-driven mixing at interfaces between fluids of differing densities through three-dimensional (3D) numerical simulations using the RAGE code in the implicit large eddy simulation context. We consider a shock-tube configuration with a band ofmore » high density gas (SF 6) embedded in low density gas (air). Shocks with a Mach number of 1.26 are passed through SF 6 bands, resulting in transition to turbulence driven by the Richtmyer-Meshkov instability. The system is followed as a rarefaction wave and a reflected secondary shock from the back wall pass through the SF 6 band. We apply a variety of initial perturbations to the interfaces between the two fluids in which the physical standard deviation, wave number range, and the spectral slope of the perturbations are held constant, but the number of modes initially present is varied. By thus decreasing the density of initial spectral modes of the interface, we find that we can achieve as much as 25% less total mixing at late times. This has potential direct implications for the treatment of initial conditions applied to material interfaces in both 3D and reduced dimensionality simulation models.« less

On magnetic field amplification and particle acceleration near non-relativistic astrophysical shocks: particles in MHD cells simulations

NASA Astrophysics Data System (ADS)

van Marle, Allard Jan; Casse, Fabien; Marcowith, Alexandre

2018-01-01

We present simulations of magnetized astrophysical shocks taking into account the interplay between the thermal plasma of the shock and suprathermal particles. Such interaction is depicted by combining a grid-based magnetohydrodynamics description of the thermal fluid with particle in cell techniques devoted to the dynamics of suprathermal particles. This approach, which incorporates the use of adaptive mesh refinement features, is potentially a key to simulate astrophysical systems on spatial scales that are beyond the reach of pure particle-in-cell simulations. We consider in this study non-relativistic shocks with various Alfvénic Mach numbers and magnetic field obliquity. We recover all the features of both magnetic field amplification and particle acceleration from previous studies when the magnetic field is parallel to the normal to the shock. In contrast with previous particle-in-cell-hybrid simulations, we find that particle acceleration and magnetic field amplification also occur when the magnetic field is oblique to the normal to the shock but on larger time-scales than in the parallel case. We show that in our simulations, the suprathermal particles are experiencing acceleration thanks to a pre-heating process of the particle similar to a shock drift acceleration leading to the corrugation of the shock front. Such oscillations of the shock front and the magnetic field locally help the particles to enter the upstream region and to initiate a non-resonant streaming instability and finally to induce diffuse particle acceleration.

A cumulative shear mechanism for tissue damage initiation in shock-wave lithotripsy.

PubMed

Freund, Jonathan B; Colonius, Tim; Evan, Andrew P

2007-09-01

Evidence suggests that inertial cavitation plays an important role in the renal injury incurred during shock-wave lithotripsy. However, it is unclear how tissue damage is initiated, and significant injury typically occurs only after a sufficient dose of shock waves. Although it has been suggested that shock-induced shearing might initiate injury, estimates indicate that individual shocks do not produce sufficient shear to do so. In this paper, we hypothesize that the cumulative shear of the many shocks is damaging. This mechanism depends on whether there is sufficient time between shocks for tissue to relax to its unstrained state. We investigate the mechanism with a physics-based simulation model, wherein the basement membranes that define the tubules and vessels in the inner medulla are represented as elastic shells surrounded by viscous fluid. Material properties are estimated from in-vitro tests of renal basement membranes and documented mechanical properties of cells and extracellular gels. Estimates for the net shear deformation from a typical lithotripter shock (approximately 0.1%) are found from a separate dynamic shock simulation. The results suggest that the larger interstitial volume (approximately 40%) near the papilla tip gives the tissue there a relaxation time comparable to clinical shock delivery rates (approximately 1 Hz), thus allowing shear to accumulate. Away from the papilla tip, where the interstitial volume is smaller (approximately 20%), the model tissue relaxes completely before the next shock would be delivered. Implications of the model are that slower delivery rates and broader focal zones should both decrease injury, consistent with some recent observations.

Euler-Lagrange Simulations of Shock Wave-Particle Cloud Interaction

NASA Astrophysics Data System (ADS)

Koneru, Rahul; Rollin, Bertrand; Ouellet, Frederick; Park, Chanyoung; Balachandar, S.

2017-11-01

Numerical experiments of shock interacting with an evolving and fixed cloud of particles are performed. In these simulations we use Eulerian-Lagrangian approach along with state-of-the-art point-particle force and heat transfer models. As validation, we use Sandia Multiphase Shock Tube experiments and particle-resolved simulations. The particle curtain upon interaction with the shock wave is expected to experience Kelvin-Helmholtz (KH) and Richtmyer-Meshkov (RM) instabilities. In the simulations evolving the particle cloud, the initial volume fraction profile matches with that of Sandia Multiphase Shock Tube experiments, and the shock Mach number is limited to M =1.66. Measurements of particle dispersion are made at different initial volume fractions. A detailed analysis of the influence of initial conditions on the evolution of the particle cloudis presented. The early time behavior of the models is studied in the fixed bed simulations at varying volume fractions and shock Mach numbers.The mean gas quantities are measured in the context of 1-way and 2-way coupled simulations. This work was supported by the U.S. Department of Energy, National Nuclear Security Administration, Advanced Simulation and Computing Program, as a Cooperative Agreement under the Predictive Science Academic Alliance Program, Contract No. DE-NA0002378.

Pressure-induced metallization of condensed phase β-HMX under shock loadings via molecular dynamics simulations in conjunction with multi-scale shock technique.

PubMed

Ge, Ni-Na; Wei, Yong-Kai; Zhao, Feng; Chen, Xiang-Rong; Ji, Guang-Fu

2014-07-01

The electronic structure and initial decomposition in high explosive HMX under conditions of shock loading are examined. The simulation is performed using quantum molecular dynamics in conjunction with multi-scale shock technique (MSST). A self-consistent charge density-functional tight-binding (SCC-DFTB) method is adapted. The results show that the N-N-C angle has a drastic change under shock wave compression along lattice vector b at shock velocity 11 km/s, which is the main reason that leads to an insulator-to-metal transition for the HMX system. The metallization pressure (about 130 GPa) of condensed-phase HMX is predicted firstly. We also detect the formation of several key products of condensed-phase HMX decomposition, such as NO2, NO, N2, N2O, H2O, CO, and CO2, and all of them have been observed in previous experimental studies. Moreover, the initial decomposition products include H2 due to the C-H bond breaking as a primary reaction pathway at extreme condition, which presents a new insight into the initial decomposition mechanism of HMX under shock loading at the atomistic level.

Less or more hemodynamic monitoring in critically ill patients.

PubMed

Jozwiak, Mathieu; Monnet, Xavier; Teboul, Jean-Louis

2018-06-07

Hemodynamic investigations are required in patients with shock to identify the type of shock, to select the most appropriate treatments and to assess the patient's response to the selected therapy. We discuss how to select the most appropriate hemodynamic monitoring techniques in patients with shock as well as the future of hemodynamic monitoring. Over the last decades, the hemodynamic monitoring techniques have evolved from intermittent toward continuous and real-time measurements and from invasive toward less-invasive approaches. In patients with shock, current guidelines recommend the echocardiography as the preferred modality for the initial hemodynamic evaluation. In patients with shock nonresponsive to initial therapy and/or in the most complex patients, it is recommended to monitor the cardiac output and to use advanced hemodynamic monitoring techniques. They also provide other useful variables that are useful for managing the most complex cases. Uncalibrated and noninvasive cardiac output monitors are not reliable enough in the intensive care setting. The use of echocardiography should be initially encouraged in patients with shock to identify the type of shock and to select the most appropriate therapy. The use of more invasive hemodynamic monitoring techniques should be discussed on an individualized basis.

Shock initiation and detonation properties of bisfluorodinitroethyl formal (FEFO)

NASA Astrophysics Data System (ADS)

Gibson, L. L.; Sheffield, S. A.; Dattelbaum, Dana M.; Stahl, David B.

2012-03-01

FEFO is a liquid explosive with a density of 1.60 g/cm3 and an energy output similar to that of trinitrotoluene (TNT), making it one of the more energetic liquid explosives. Here we describe shock initiation experiments that were conducted using a two-stage gas gun using magnetic gauges to measure the wave profiles during a shock-to-detonation transition. Unreacted Hugoniot data, time-to detonation (overtake) measurements, and reactive wave profiles were obtained from each experiment. FEFO was found to initiate by the homogeneous initiation model, similar to all other liquid explosives we have studied (nitromethane, isopropyl nitrate, hydrogen peroxide). The new unreacted Hugoniot points agree well with other published data. A universal liquid Hugoniot estimation slightly under predicts the measured Hugoniot data. FEFO is very insensitive, with about the same shock sensitivity as the triamino-trinitro-benzene (TATB)-based explosive PBX9502 and cast TNT.

Numerical simulations of the process of multiple shock-flame interactions

NASA Astrophysics Data System (ADS)

Jiang, Hua; Dong, Gang; chen, Xiao; Wu, Jin-Tao

2016-08-01

Based on a weighted essentially nonoscillatory scheme, the multiple interactions of a flame interface with an incident shock wave and its reshock waves are numerically simulated by solving the compressible reactive Navier-Stokes equations with a single-step Arrhenius chemical reaction. The two-dimensional sinusoidally perturbed premixed flames with different initial perturbed amplitudes are used to investigate the effect of the initial perturbation on the flame evolutions. The results show that the development of the flame interface is directly affected by the initial perturbed amplitudes before the passages of reshock waves, and the perturbation development is mainly controlled by the Richtmyer-Meshkov instability (RMI). After the successive impacts of multiple reshock waves, the chemical reaction accelerates the consumption of reactants and leads to a gradual disappearance of the initial perturbed information. The perturbation developments in frozen flows with the same initial interface as those in reactive flows are also demonstrated. Comparisons of results between the reactive and frozen flows show that a chemical reaction changes the perturbation pattern of the flame interface by decreasing the density gradient, thereby weakening the baroclinic torque in the flame mixing region, and therefore plays a dominant role after the passage of reshock waves.

An infrared flash contemporaneous with the gamma-rays of GRB 041219a.

PubMed

Blake, C H; Bloom, J S; Starr, D L; Falco, E E; Skrutskie, M; Fenimore, E E; Duchêne, G; Szentgyorgyi, A; Hornstein, S; Prochaska, J X; McCabe, C; Ghez, A; Konopacky, Q; Stapelfeldt, K; Hurley, K; Campbell, R; Kassis, M; Chaffee, F; Gehrels, N; Barthelmy, S; Cummings, J R; Hullinger, D; Krimm, H A; Markwardt, C B; Palmer, D; Parsons, A; McLean, K; Tueller, J

2005-05-12

The explosion that results in a cosmic gamma-ray burst (GRB) is thought to produce emission from two physical processes: the central engine gives rise to the high-energy emission of the burst through internal shocking, and the subsequent interaction of the flow with the external environment produces long-wavelength afterglows. Although observations of afterglows continue to refine our understanding of GRB progenitors and relativistic shocks, gamma-ray observations alone have not yielded a clear picture of the origin of the prompt emission nor details of the central engine. Only one concurrent visible-light transient has been found and it was associated with emission from an external shock. Here we report the discovery of infrared emission contemporaneous with a GRB, beginning 7.2 minutes after the onset of GRB 041219a (ref. 8). We acquired 21 images during the active phase of the burst, yielding early multi-colour observations. Our analysis of the initial infrared pulse suggests an origin consistent with internal shocks.

Experimental Study on Reaction Characteristics of PTFE/Ti/W Energetic Materials under Explosive Loading

PubMed Central

Li, Yan; Jiang, Chunlan; Wang, Zaicheng; Luo, Puguang

2016-01-01

Metal/fluoropolymer composites represent a new category of energetic structural materials that release energy through exothermic chemical reactions initiated under shock loading conditions. This paper describes an experiment designed to study the reaction characteristics of energetic materials with low porosity under explosive loading. Three PTFE (polytetrafluoroethylene)/Ti/W mixtures with different W contents are processed through pressing and sintering. An inert PTFE/W mixture without reactive Ti particles is also prepared to serve as a reference. Shock-induced chemical reactions are recorded by high-speed video through a narrow observation window. Related shock parameters are calculated based on experimental data, and differences in energy release are discussed. The results show that the reaction propagation of PTFE/Ti/W energetic materials with low porosity under explosive loading is not self-sustained. As propagation distance increases, the energy release gradually decreases. In addition, reaction failure distance in PTFE/Ti/W composites is inversely proportional to the W content. Porosity increased the failure distance due to higher shock temperature. PMID:28774056

A new method to study he effective shear modulus of shocked material

NASA Astrophysics Data System (ADS)

Xiaojuan, Ma; Fusheng, Liu

2013-06-01

Shear modulus is a crucial material parameter for description of mechanical behavior. However, at strong shock compression, it is generally deduced from the longitudinal and bulk sound velocity evaluated by unloading wave profile measurement. Here, a new method called the disturbed amplitude damping method of shock wave is presented, that can directly measure the shear modulus of material. This method relies on the correlation between the shear modulus of shock compressed state and amplitude damping and oscillation of an initial sinusoidal disturbance on shock front in concerned substance. Two important steps are required to determine the shear modulus of material. The first is to measure the damping and oscillation feature of disturbance by the flyer impacted method. The second is to find the quantitative relationship between the disturbed amplitude damping and shear modulus by the finite difference method which is applied to obtain the numerical solutions for disturbance amplitude damping behavior of sinusoidal shock front in flyer impacted flow field. When aluminum shocked to 80 GPa is taken as an example, the shape of perturbed shock front and its disturbed amplitude development with propagation distance, are approximately mapped out. The figure shows an oscillatory damping characteristic. At the early stage the perturbation amplitude on the shock front experiences a decaying process until to zero point, then it rises to a maximum but in reverse phase, and then it decays again. Comparing these data with those simulated using the SCG constitutive model, the effective shear modulus for aluminum shocked to 80 GPa is determined to be about 90 GPa, which is higher than the result given by Yu.

Original size of the Vredefort structure, South Africa

NASA Technical Reports Server (NTRS)

Therriault, A. M.; Reid, A. M.; Reimold, W. U.

1993-01-01

The Vredefort structure is located approximately 120 km southwest of Johannesburg, South Africa, and is deeply eroded. Controversies remain on the origin of this structure with the most popular hypotheses being: (1) by impact cratering about 2.0 Ga; (2) as a cryptoexplosion structure about 2.0 Ga; and (3) by purely tectonic processes starting at about 3.0 Ga and ending with the Vredefort event at 2.0 Ga. In view of recent work in which the granophyre dikes are interpreted as the erosional remants of a more extensive impact melt sheet, injected downward into the underlying country rocks, the impact origin hypothesis for Vredefort is adopted. In order to estimate the original dimensions of the Vredefort impact structure, it is assumed that the structure was initially circular, that its predeformation center corresponds to the center of the granitic core, and that the pre-Vredefort geology of the area prior to approximately 2.0 Ga ago is as suggested by Fletcher and Reimold. The spatial relationship between shock metamorphic effects, the shock pressures they record, and the morphological features of the crater were established for a number of large terrestrial craters. The principles of crater formation at large complex impact structures comparable in size to Vredefort were also established, although many details remain unresolved. An important conclusion is that the transient crater, which is formed directly by excavation and displacement by the shock-induced cratering flow-field (i.e., the particle velocity flow field existing in the region of the transient crater but behind the initial outgoing shock front), is highly modified during the late stage processes. The original transient crater diameter lies well within the final rim of the crater, which is established by structural movements during late-stage cavity modification.

One dimensional shock Initiation of UK Comp B

NASA Astrophysics Data System (ADS)

Burns, Malcolm

2017-06-01

Ten shock initiation experiments have been carried out on the UK isostatically pressed Composition B (59.5% RDX, 39.5% TNT, 1% wax) comprising of seven sustained pulse experiments with input pressures ranging from 2.89 to 9.86 GPa and three short shock experiments using the embedded gauge technique at the Los Alamos National Laboratory gas gun facility. The evolution of the reactive growth at and behind the shock front has been measured along with the run to detonation distance. These data have been used to create the Pop plot and hugoniot states for the UK Comp B. The shock initiation behavior of the UK Comp B has been compared to that of the equivalent US Composition. The reactive growth shows a feature that was observed in the US composition in which the wave profiles dispay a high level of pre-detonation noise. This was hypothesized to be due to a piezoelectric effect in the RDX crystals. The results of these experiments have shown that this effect may be localized in the gamma phase at shock pressures in the region of 5 GP and above.

Evaluation of a novel 5-group classification system of sepsis by vasopressor use and initial serum lactate in the emergency department.

PubMed

Swenson, Kai E; Dziura, James D; Aydin, Ani; Reynolds, Jesse; Wira, Charles R

2018-03-01

Prognostication in sepsis is limited by disease heterogeneity, and measures to risk-stratify patients in the proximal phases of care lack simplicity and accuracy. Hyperlactatemia and vasopressor dependence are easily identifiable risk factors for poor outcomes. This study compares incidence and hospital outcomes in sepsis based on initial serum lactate level and vasopressor use in the emergency department (ED). In a retrospective analysis of a prospectively identified dual-center ED registry, patients with sepsis were categorized by ED vasopressor use and initial serum lactate level. Vasopressor-dependent patients were categorized as dysoxic shock (lactate >4.0 mmol/L) and vasoplegic shock (≤4.0 mmol/L). Patients not requiring vasopressors were categorized as cryptic shock major (lactate >4.0 mmol/L), cryptic shock minor (>2.0 and ≤4.0 mmol/L), and sepsis without lactate elevation (≤2.0 mmol/L). Of 446 patients included, 4.9% (n = 22) presented in dysoxic shock, 11.7% (n = 52) in vasoplegic shock, 12.1% (n = 54) in cryptic shock major, 30.9% (n = 138) in cryptic shock minor, and 40.4% (n = 180) in sepsis without lactate elevation. Group mortality rates at 28 days were 50.0, 21.1, 18.5, 12.3, and 7.2%, respectively. After adjusting for potential confounders, odds ratios for mortality at 28 days were 15.1 for dysoxic shock, 3.6 for vasoplegic shock, 3.8 for cryptic shock major, and 1.9 for cryptic shock minor, when compared to sepsis without lactate elevation. Lactate elevation is associated with increased mortality in both vasopressor dependent and normotensive infected patients presenting to the emergency department (ED). Cryptic shock mortality (normotension + lactate >4 mmol/L) is equivalent to vasoplegic shock mortality (vasopressor requirement + lactate <4 mmol/L) in our population. The odds of normotensive, infected patients decompensating is three to fourfold higher with hyperlactemia. The proposed Sepsis-3 definitions exclude an entire group of high-risk ED patients. A simple classification in the ED by vasopressor requirement and initial lactate level may identify high-risk subgroups of sepsis. This study may inform prognostication and triage decisions in the proximal phases of care.

Gaseous detonation initiation via wave implosion

NASA Astrophysics Data System (ADS)

Jackson, Scott Irving

Efficient detonation initiation is a topic of intense interest to designers of pulse detonation engines. This experimental work is the first to detonate propane-air mixtures with an imploding detonation wave and to detonate a gas mixture with a non-reflected, imploding shock. In order to do this, a unique device has been developed that is capable of generating an imploding toroidal detonation wave inside of a tube from a single ignition point without any obstruction to the tube flow path. As part of this study, an initiator that creates a large-aspect-ratio planar detonation wave in gas-phase explosive from a single ignition point has also been developed. The effectiveness of our initiation devices has been evaluated. The minimum energy required by the imploding shock for initiation was determined to scale linearly with the induction zone length, indicating the presence of a planar initiation mode. The imploding toroidal detonation initiator was found to be more effective at detonation initiation than the imploding shock initiator, using a comparable energy input to that of current initiator tubes.

Kinetic structures of quasi-perpendicular shocks in global particle-in-cell simulations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Peng, Ivy Bo, E-mail: bopeng@kth.se; Markidis, Stefano; Laure, Erwin

2015-09-15

We carried out global Particle-in-Cell simulations of the interaction between the solar wind and a magnetosphere to study the kinetic collisionless physics in super-critical quasi-perpendicular shocks. After an initial simulation transient, a collisionless bow shock forms as a result of the interaction of the solar wind and a planet magnetic dipole. The shock ramp has a thickness of approximately one ion skin depth and is followed by a trailing wave train in the shock downstream. At the downstream edge of the bow shock, whistler waves propagate along the magnetic field lines and the presence of electron cyclotron waves has beenmore » identified. A small part of the solar wind ion population is specularly reflected by the shock while a larger part is deflected and heated by the shock. Solar wind ions and electrons are heated in the perpendicular directions. Ions are accelerated in the perpendicular direction in the trailing wave train region. This work is an initial effort to study the electron and ion kinetic effects developed near the bow shock in a realistic magnetic field configuration.« less

Focusing of noncircular self-similar shock waves.

PubMed

Betelu, S I; Aronson, D G

2001-08-13

We study the focusing of noncircular shock waves in a perfect gas. We construct an explicit self-similar solution by combining three convergent plane waves with regular shock reflections between them. We then show, with a numerical Riemann solver, that there are initial conditions with smooth shocks whose intermediate asymptotic stage is described by the exact solution. Unlike the focusing of circular shocks, our self-similar shocks have bounded energy density.

The emotional process from diagnosis to birth following a prenatal diagnosis of fetal anomaly: A qualitative study of messages in online discussion boards.

PubMed

Carlsson, Tommy; Starke, Veronica; Mattsson, Elisabet

2017-05-01

to explore written statements found in online discussion boards where parents currently expecting, or with previous experience of expecting, a child with a prenatally diagnosed congenital anomaly communicate about their emotional process from diagnosis to birth. cross-sectional qualitative study of messages in public online discussion boards. Swedish public discussion boards about reproductive subjects. ten pregnant women and eight parents (of children with prenatal diagnoses) who had written 852 messages in five threads in Swedish online discussion boards identified via systematic searches. three phases were identified in the process of moving from the diagnosis to the birth: shock, existential crisis, and life remodeling. The people posting message ('posters') moved from initial shock to existential crisis and, lastly, a phase of remodeling life later in the pregnancy. During the pregnancy, considerable worries about both antenatal and postnatal aspects were expressed. To cope with their situation, the posters distanced themselves from the diagnoses, vented their feelings, sought control, and obtained practical support from friends and relatives. expectant parents faced with a prenatal diagnosis move from initial shock to a phase of life remodeling and acceptance. Burdened with considerable worries, expectant parents cope with their situation through informational, emotional, and instrumental support from health professionals, family, friends, and peers. health professionals should make sure that expectant parents feel involved in planning their children's postnatal care, that they are offered sufficient information, and that they have access to emotional and instrumental support structures. Copyright © 2017. Published by Elsevier Ltd.

Kappa-Electrons Downstream of the Solar Wind Termination Shock

NASA Astrophysics Data System (ADS)

Fahr, H. J.

2017-12-01

A theoretical description of the solar wind electron distribution function downstream of the termination shock under the influence of the shock-induced injection of overshooting KeV-energetic electrons will be presented. A kinetic phasespace transport equation in the bulk frame of the heliosheath plasma flow is developed for the solar wind electrons, taking into account shock-induced electron injection, convective changes, magnetic cooling processes and whistler wave-induced energy diffusion. Assuming that the local electron distribution under the prevailing Non-LTE conditions can be represented by a local kappa function with a local kappa parameter that varies with the streamline coordinates, we determine the parameters of the resulting, initial kappa distribution for the downstream electrons. From this initial function spectral electron fluxes can be derived and can be compared with those measured by the VOYAGER-1 spacecraft in the range between 40 to 70 KeV. It can then be shown that with kappa values around kappa = 6 one can in fact fit these data very satisfactorily. In addition it is shown that for isentropic electron flows kappa-distributed electrons have to undergo simultaneous changes of both parameters, i.e. kappa and theta, of the electron kappa function. It is also shown then that under the influence of energy sinks and sources the electron flux becomes non-isentropic with electron entropies changing along the streamline.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Peralta, Pedro; Fortin, Elizabeth; Opie, Saul

Activities for this grant included: 1) Development of dynamic impact experiments to probe strength and phase transition influence on dynamic deformation, 2) development of modern strength and phase aware simulation capabilities, 3) and post-processing of experimental data with simulation and closed form analytical techniques. Two different dynamic experiments were developed to probe material strengths in solid metals (largely copper and iron in this effort). In the first experiment a flyer plate impacts a flat target with an opposite rippled surface that is partially supported by a weaker window material. Post mortem analysis of the target sample showed a strong andmore » repeatable residual plastic deformation dependence on grain orientation. Yield strengths for strain rates near 10 5 s -1 and plastic strains near ~50% were estimated to be around 180 to 240 MPa, varying in this range with grain orientation. Unfortunately dynamic real-time measurements were difficult with this setup due to diagnostic laser scattering; hence, an additional experimental setup was developed to complement these results. In the second set of experiments a rippled surface was ablated by a controlled laser pulsed, which launched a rippled shock front to an opposite initially flat diagnostic surface that was monitored in real-time with spatially resolved velocimetry techniques, e.g., line VISAR in addition to Transient Imaging Displacement Interferometry (TIDI) displacement measurements. This setup limited the displacements at the diagnostic surface to a reasonable level for TIDI measurements (~ less than one micrometer). These experiments coupled with analytical and numerical solutions provided evidence that viscous and elastic deviatoric strength affect shock front perturbation evolution in clearly different ways. Particularly, normalized shock front perturbation amplitudes evolve with viscosity (η) and perturbation wavelength (λ) as η/λ, such that increasing viscosity (or decreasing the initial wavelength) delays the perturbation decay. Conversely our experimental data, analysis and simulations show that for materials with elastic yield strength Y the normalized shock perturbation amplitude evolves with Yλ/A 0, which shows wavelength increases have the opposite effect as in viscous materials and perturbation decay is also dependent on initial amplitude A 0 (viscous materials are independent of this parameter). Materials where strength had clear strain rate dependence, e.g., such as a PTW material law, behaved similarly to materials with only an effective yield stress (elastic-perfectly plastic) in the shock front perturbation studies obeying a Y effλA 0 relationship where Y eff was a constant (near ~400 MPa for Cu for strain rates around 10 6 s -1). Magnitude changes in strain rate would increase Y eff as would be expected from the PTW behavior, but small perturbations (typical of regions behind the shock front) near a mean had little effect. Additional work based on simulations showed that phase transformation kinetics can affect the behavior of the perturbed shock front as well as the evolution of the RM-like instability that develops due to the imprint of the perturbed shock front on the initially flat surface as the shock breaks out.« less

Evaluation of solar Type II radio burst estimates of initial solar wind shock speed using a kinematic model of the solar wind on the April 2001 solar event swarm

NASA Astrophysics Data System (ADS)

Sun, W.; Dryer, M.; Fry, C. D.; Deehr, C. S.; Smith, Z.; Akasofu, S.-I.; Kartalev, M. D.; Grigorov, K. G.

2002-04-01

We compare simulation results of real time shock arrival time prediction with observations by the ACE satellite for a series of solar flares/coronal mass ejections which took place between 28 March and 18 April, 2001 on the basis of the Hakamada-Akasofu-Fry, version 2 (HAFv.2) model. It is found, via an ex post facto calculation, that the initial speed of shock waves as an input parameter of the modeling is crucial for the agreement between the observation and the simulation. The initial speed determined by metric Type II radio burst observations must be substantially reduced (30 percent in average) for most high-speed shock waves.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kay, Jeffrey J.; Park, Samuel; Kohl, Ian Thomas

In this work, shock-induced reactions in high explosives and their chemical mechanisms were investigated using state-of-the-art experimental and theoretical techniques. Experimentally, ultrafast shock interrogation (USI, an ultrafast interferometry technique) and ultrafast absorption spectroscopy were used to interrogate shock compression and initiation of reaction on the picosecond timescale. The experiments yielded important new data that appear to indicate reaction of high explosives on the timescale of tens of picoseconds in response to shock compression, potentially setting new upper limits on the timescale of reaction. Theoretically, chemical mechanisms of shock-induced reactions were investigated using density functional theory. The calculations generated important insightsmore » regarding the ability of several hypothesized mechanisms to account for shock-induced reactions in explosive materials. The results of this work constitute significant advances in our understanding of the fundamental chemical reaction mechanisms that control explosive sensitivity and initiation of detonation.« less

Early administration of hydrocortisone replacement after the advent of septic shock: impact on survival and immune response*.

PubMed

Katsenos, Chrysostomos S; Antonopoulou, Anastasia N; Apostolidou, Efterpi N; Ioakeimidou, Aikaterini; Kalpakou, Georgia Th; Papanikolaou, Metaxia N; Pistiki, Aikaterini C; Mpalla, Margarita C; Paraschos, Michael D; Patrani, Maria A; Pratikaki, Maria E; Retsas, Theodoros A; Savva, Athina A; Vassiliagkou, Spyridoula D; Lekkou, Alexandra A; Dimopoulou, Ioanna; Routsi, Christina; Mandragos, Konstantinos E

2014-07-01

To investigate the impact of early initiation of hydrocortisone therapy on the clinical course of septic shock and on cytokine release. Prospective study in patients with septic shock treated with low doses of hydrocortisone. ICUs and general wards. Over a 2-year period, 170 patients with septic shock treated with low doses of hydrocortisone were enrolled. Blood was sampled from 34 patients for isolation of peripheral blood mononuclear cells and cytokine stimulation before and 24 hours after the start of hydrocortisone. None. After quartile analysis, patients were divided into those with early initiation of hydrocortisone (< 9 hr after vasopressors, n = 46) and those with late initiation of hydrocortisone (> 9 hr after vasopressors, n = 124). After adjusting for disease severity and type of infection, a protective effect of early hydrocortisone administration against unfavorable outcome was found (hazard ratio, 0.20; p = 0.012). Time of discontinuation of vasopressors was earlier among patients with initiation of hydrocortisone within 9 hours. Production of tumor necrosis factor-α was lower among patients who had had hydrocortisone early. In patients receiving hydrocortisone for septic shock, early initiation of treatment was associated with improved survival. This treatment was also associated with attenuated stimulation of tumor necrosis factor-α.

Guidance on the Assessment and Development of Insensitive Munitions (MURAT)

DTIC Science & Technology

2006-05-01

theoretical modelling . For this reason it is the best understood of all the areas on the flowchart. If the charge is already shocked by a previous impact...the initiation of heterogeneous high explosives due to shock waves are finite rate chemical reactions involved in the conversion of solid explosive ... explosive , increasing the chance of shock initiation (N26) Such an impact would have to take account of case material ahead of the fragment

[A patient with toxic shock syndrome following correction of the nasal septum].

PubMed

Schweitzer, D H; Moffie, B G; van der Mey, A G; Thompson, J

1990-11-03

A male aged 30 suffered from toxic shock syndrome after septorhinoplasty with positioning of a tampon. Initial treatment consisted of removing the tampon and supportive care, as a result of which the patient recovered. The patient was a carrier of Staphylococcus aureus which produced toxic shock syndrome toxin-I (TSST-I). Anti-TSST-I antibodies were already found in the serum in the initial phase of the disease.

Shock Detector for SURF model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Menikoff, Ralph

2016-01-11

SURF and its extension SURFplus are reactive burn models aimed at shock initiation and propagation of detonation waves in high explosives. A distinctive feature of these models is that the burn rate depends on the lead shock pressure. A key part of the models is an algorithm to detect the lead shock. Typically, shock capturing hydro algorithms have small oscillations behind a shock. Here we investigate how well the shock detection algorithm works for a nearly steady propagating detonation wave in one-dimension using the Eulerian xRage code.

The formation and evolution of reconnection-driven, slow-mode shocks in a partially ionised plasma

NASA Astrophysics Data System (ADS)

Hillier, A.; Takasao, S.; Nakamura, N.

2016-06-01

The role of slow-mode magnetohydrodynamic (MHD) shocks in magnetic reconnection is of great importance for energy conversion and transport, but in many astrophysical plasmas the plasma is not fully ionised. In this paper, we use numerical simulations to investigate the role of collisional coupling between a proton-electron, charge-neutral fluid and a neutral hydrogen fluid for the one-dimensional (1D) Riemann problem initiated in a constant pressure and density background state by a discontinuity in the magnetic field. This system, in the MHD limit, is characterised by two waves. The first is a fast-mode rarefaction wave that drives a flow towards a slow-mode MHD shock wave. The system evolves through four stages: initiation, weak coupling, intermediate coupling, and a quasi-steady state. The initial stages are characterised by an over-pressured neutral region that expands with characteristics of a blast wave. In the later stages, the system tends towards a self-similar solution where the main drift velocity is concentrated in the thin region of the shock front. Because of the nature of the system, the neutral fluid is overpressured by the shock when compared to a purely hydrodynamic shock, which results in the neutral fluid expanding to form the shock precursor. Once it has formed, the thickness of the shock front is proportional to ξ I-1.2 , which is a smaller exponent than would be naively expected from simple scaling arguments. One interesting result is that the shock front is a continuous transition of the physical variables of subsonic velocity upstream of the shock front (a c-shock) to a sharp jump in the physical variables followed by a relaxation to the downstream values for supersonic upstream velocity (a j-shock). The frictional heating that results from the velocity drift across the shock front can amount to ~2 per cent of the reference magnetic energy.

Ignition-and-Growth Modeling of NASA Standard Detonator and a Linear Shaped Charge

NASA Technical Reports Server (NTRS)

Oguz, Sirri

2010-01-01

The main objective of this study is to quantitatively investigate the ignition and shock sensitivity of NASA Standard Detonator (NSD) and the shock wave propagation of a linear shaped charge (LSC) after being shocked by NSD flyer plate. This combined explosive train was modeled as a coupled Arbitrary Lagrangian-Eulerian (ALE) model with LS-DYNA hydro code. An ignition-and-growth (I&G) reactive model based on unreacted and reacted Jones-Wilkins-Lee (JWL) equations of state was used to simulate the shock initiation. Various NSD-to-LSC stand-off distances were analyzed to calculate the shock initiation (or failure to initiate) and detonation wave propagation along the shaped charge. Simulation results were verified by experimental data which included VISAR tests for NSD flyer plate velocity measurement and an aluminum target severance test for LSC performance verification. Parameters used for the analysis were obtained from various published data or by using CHEETAH thermo-chemical code.

Printable sensors for explosive detonation

NASA Astrophysics Data System (ADS)

Griffith, Matthew J.; Cooling, Nathan A.; Elkington, Daniel C.; Muller, Elmar; Belcher, Warwick J.; Dastoor, Paul C.

2014-10-01

Here, we report the development of an organic thin film transistor (OTFT) based on printable solution processed polymers and employing a quantum tunnelling composite material as a sensor to convert the pressure wave output from detonation transmission tubing (shock tube) into an inherently amplified electronic signal for explosives initiation. The organic electronic detector allows detection of the signal in a low voltage operating range, an essential feature for sites employing live ordinances that is not provided by conventional electronic devices. We show that a 30-fold change in detector response is possible using the presented detector assembly. Degradation of the OTFT response with both time and repeated voltage scans was characterised, and device lifetime is shown to be consistent with the requirements for on-site printing and usage. The integration of a low cost organic electronic detector with inexpensive shock tube transmission fuse presents attractive avenues for the development of cheap and simple assemblies for precisely timed initiation of explosive chains.

Modeling Type IIn Supernovae: Understanding How Shock Development Effects Light Curves Properties

NASA Astrophysics Data System (ADS)

De La Rosa, Janie

2016-06-01

Type IIn supernovae are produced when massive stars experience dramatic mass loss phases caused by opacity edges or violent explosions. Violent mass ejections occur quite often just prior to the collapse of the star. If the final episode happens just before collapse, the outward ejecta is sufficiently dense to alter the supernova light-curve, both by absorbing the initial supernova light and producing emission when the supernova shock hits the ejecta. Initially, the ejecta is driven by shock progating through the interior of the star, and eventually expands through the circumstellar medium, forming a cold dense shell. As the shock wave approaches the shell, there is an increase in UV and optical radiation at the location of the shock breakout. We have developed a suite of simple semi-analytical models in order to understand the relationship between our observations and the properties of the expanding SN ejecta. When we compare Type IIn observations to a set of modeled SNe, we begin to see the influence of initial explosion conditions on early UV light curve properties such as peak luminosities and decay rate.The fast rise and decay corresponds to the models representing a photosphere moving through the envelope, while the modeled light curves with a slower rise and decay rate are powered by 56Ni decay. However, in both of these cases, models that matched the luminosity were unable to match the low radii from the blackbody models. The effect of shock heating as the supernova material blasts through the circumstellar material can drastically alter the temperature and position of the photosphere. The new set of models redefine the initial modeling conditions to incorporate an outer shell-like structure, and include late-time shock heating from shocks produced as the supernova ejecta travels through the inhomogeneous circumstellar medium.

Shock initiated thermal and chemical responses of HMX crystal from ReaxFF molecular dynamics simulation.

PubMed

Zhou, Tingting; Song, Huajie; Liu, Yi; Huang, Fenglei

2014-07-21

To gain an atomistic-level understanding of the thermal and chemical responses of condensed energetic materials under thermal shock, we developed a thermal shock reactive dynamics (TS-RD) computational protocol using molecular dynamics simulation coupled with ReaxFF force field. β-Octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocane (HMX) was selected as a a target explosive due to its wide usage in the military and industry. The results show that a thermal shock initiated by a large temperature gradient between the "hot" region and the "cold" region results in thermal expansion of the particles and induces a thermal-mechanical wave propagating back and forth in the system with an averaged velocity of 3.32 km s(-1). Heat propagating along the direction of thermal shock leads to a temperature increment of the system and thus chemical reaction initiation. Applying a continuum reactive heat conduction model combined with the temperature distribution obtained from the RD simulation, a heat conduction coefficient is derived as 0.80 W m(-1) K(-1). The chemical reaction mechanisms during thermal shock were analyzed, showing that the reaction is triggered by N-NO2 bond breaking followed by HONO elimination and ring fission. The propagation rates of the reaction front and reaction center are obtained to be 0.069 and 0.038 km s(-1), based on the time and spatial distribution of NO2. The pressure effect on the thermal shock was also investigated by employing uniaxial compression before the thermal shock. We find that compression significantly accelerates thermal-mechanical wave propagation and heat conduction, resulting in higher temperature and more excited molecules and thus earlier initiation and faster propagation of chemical reactions.

Development of a simultaneous Hugoniot and temperature measurement for preheated-metal shock experiments: melting temperatures of Ta at pressures of 100 GPa.

PubMed

Li, Jun; Zhou, Xianming; Li, Jiabo; Wu, Qiang; Cai, Lingcang; Dai, Chengda

2012-05-01

Equations of state of metals are important issues in earth science and planetary science. A major limitation of them is the lack of experimental data for determining pressure-volume and temperature of shocked metal simultaneously. By measuring them in a single experiment, a major source of systematic error is eliminated in determining from which shock pressure release pressure originates. Hence, a non-contact fast optical method was developed and demonstrated to simultaneously measure a Hugoniot pressure-volume (P(H)-V(H)) point and interfacial temperature T(R) on the release of Hugoniot pressure (P(R)) for preheated metals up to 1000 K. Experimental details in our investigation are (i) a Ni-Cr resistance coil field placed around the metal specimen to generate a controllable and stable heating source, (ii) a fiber-optic probe with an optical lens coupling system and optical pyrometer with ns time resolution to carry out non-contact fast optical measurements for determining P(H)-V(H) and T(R). The shock response of preheated tantalum (Ta) at 773 K was investigated in our work. Measured data for shock velocity versus particle velocity at an initial state of room temperature was in agreement with previous shock compression results, while the measured shock data between 248 and 307 GPa initially heated to 773 K were below the Hugoniot evaluation from its off-Hugoniot states. Obtained interfacial temperatures on release of Hugoniot pressures (100-170 GPa) were in agreement with shock-melting points at initial ambient condition and ab initio calculations of melting curve. It indicates a good consistency for shock melting data of Ta at different initial temperatures. Our combined diagnostics for Hugoniot and temperature provides an important approach for studying EOS and the temperature effect of shocked metals. In particular, our measured melting temperatures of Ta address the current controversy about the difference by more than a factor of 2 between the melting temperatures measured under shock and those measured in a laser-heated diamond anvil cell at ∼100 GPa.

Dynamics of a Pipeline under the Action of Internal Shock Pressure

NASA Astrophysics Data System (ADS)

Il'gamov, M. A.

2017-11-01

The static and dynamic bending of a pipeline in the vertical plane under the action of its own weight is considered with regard to the interaction of the internal pressure with the curvature of the axial line and the axisymmetric deformation. The pressure consists of a constant and timevarying parts and is assumed to be uniformly distributed over the entire span between the supports. The pipeline reaction to the stepwise increase in the pressure is analyzed in the case where it is possible to determine the exact solution of the problem. The initial stage of bending determined by the smallness of elastic forces as compared to the inertial forces is introduced into the consideration. At this stage, the solution is sought in the form of power series and the law of pressure variation can be arbitrary. This solution provides initial conditions for determining the further process. The duration of the inertial stage is compared with the times of sharp changes of the pressure and the shock waves in fluids. The structure parameters are determined in the case where the shock pressure is accepted only by the inertial forces in the pipeline.

Effect of Shockwave Curvature on Run Distance Observed with a Modified Wedge Test

NASA Astrophysics Data System (ADS)

Lee, Richard; Dorgan, Robert; Sutherland, Gerrit; Benedetta, Ashley; Milby, Christopher

2011-06-01

The effect of wave curvature on shock initiation in PBXN-110 was investigated using a modified wedge test configuration. Various thicknesses of PBXN-110 donor slabs were used to define the shockwave curvature introduced to wedge samples of the same explosive. The donor slabs were initiated with line-wave generators so that the introduced shock would be the same shape, magnitude and duration across the entire input surface of the wedge. The shock parameters were varied for a given donor thickness via different widths of PMMA spacers placed between the donor and the wedge. A framing camera was used to observe where initiation occurred along the face of the wedge. Initiation always occurred at the center of the shock front instead of the sides like that reported by others using a much smaller test format. Results were compared to CTH calculations to indicate if there were effects associated with highly curved shock fronts that could not be adequately predicted. The run distance predicted in CTH for a 50.8 mm thick donor slab (low curvature) compared favorably with experimental results. However, results from thinner donor slabs (higher curvature) indicate a more sensitive behavior than the simulations predicted.

Effect of shockwave curvature on run distance observed with a modified wedge test

NASA Astrophysics Data System (ADS)

Lee, Richard; Dorgan, Robert J.; Sutherland, Gerrit; Benedetta, Ashley; Milby, Christopher

2012-03-01

The effect of wave curvature on shock initiation in PBXN-110 was investigated using a modified wedge test configuration. Various widths of PBXN-110 donor slabs were used to define the shockwave curvature introduced to wedge samples of the same explosive. The donor slabs were initiated with line-wave generators so that the shock from the donor would be the same shape, magnitude and duration across the entire input surface of the wedge. The shock parameters were varied for a given donor with PMMA spacers placed between the donor and the wedge sample. A high-speed electronic framing camera was used to observe where initiation occurred along the face of the wedge. Initiation always occurred at the center of the shock front instead of along the sides like that reported by others using a much smaller test format. Results were compared to CTH calculations to indicate if there were effects associated with highly curved shock fronts that could not be adequately predicted. The run distance predicted in CTH for a 50.8 mm wide donor slab (low curvature) compared favorably with experimental results. However, results from thinner donor slabs (higher curvature) indicate a more sensitive behavior than the simulations predicted.

Quartz-coesite-stishovite relations in shocked metaquartzites from the Vredefort impact structure, South Africa

NASA Astrophysics Data System (ADS)

Spray, John G.; Boonsue, Suporn

2018-01-01

Coesite and stishovite are developed in shock veins within metaquartzites beyond a radius of 30 km from the center of the 2.02 Ga Vredefort impact structure. This work focuses on deploying analytical field emission scanning electron microscopy, electron backscattered diffraction, and Raman spectrometry to better understand the temporal and spatial relations of these silica polymorphs. α-Quartz in the host metaquartzites, away from shock veins, exhibits planar features, Brazil twins, and decorated planar deformation features, indicating a primary (bulk) shock loading of >5 < 35 GPa. Within the shock veins, coesite forms anhedral grains, ranging in size from 0.5 to 4 μm, with an average of 1.25 μm. It occurs in clasts, where it displays a distinct jigsaw texture, indicative of partial reversion to a less dense SiO2 phase, now represented by microcrystalline quartz. It is also developed in the matrix of the shock veins, where it is typically of smaller size (<1 μm). Stishovite occurs as euhedral acicular crystals, typically <0.5 μm wide and up to 15 μm in length, associated with clast-matrix or shock vein margin-matrix interfaces. In this context, the needles occur as radiating or subparallel clusters, which grow into/over both coesite and what is now microcrystalline quartz. Stishovite also occurs as more blebby, subhedral to anhedral grains in the vein matrix (typically <1 μm). We propose a model for the evolution of the veins (1) precursory frictional melting in a microfault ( 1 mm wide) generates a molten matrix containing quartz clasts. This is followed by (2) arrival of the main shock front, which shocks to 35 GPa. This generates coesite in the clasts and in the matrix. (3) On initial shock release, the coesite partly reverts to a less dense SiO2 phase, which is now represented by microcrystalline quartz. (4) With continued release, stishovite forms euhedral needle clusters at solid-liquid interfaces and as anhedral crystals in the matrix. (5) With decreasing pressure-temperature, the matrix completes crystallization to yield a microcrystalline quasi-igneous texture comprising quartz-coesite-stishovite-kyanite-biotite-alkali feldspar and accessory phases. It is possible that the shock vein represents the locus of a thermal spike within the bulk shock, in which case there is no requirement for additional pressure (i.e., the bulk shock was ≃35 GPa). However, if that pressure was not realized from the main shock, then supplementary pressure excursions within the vein would have been required. These could have taken the form of localized reverberations from wave trapping, or implosion processes, including pore collapse, phase change-initiated volume reduction, and melt cavitation.

Heat shock, but not temperature, is a biological trigger for the exsheathment of third-stage larvae of Haemonchus contortus.

PubMed

Bekelaar, Kiliana; Waghorn, Tania; Tavendale, Michael; McKenzie, Catherine; Leathwick, Dave

2018-05-21

Gastrointestinal parasites are an important health issue in grazing ruminants. Understanding the processes involved in the transition from the free living to the parasitic life stage of these nematodes is one avenue to identifying new targets amenable to future intervention. The transition to parasitism is initiated by exsheathment and is triggered by the sudden change in environment after ingestion of the infective larva by the host. Two major changes in environment are the increases in temperature and carbon dioxide (CO 2 ) levels. For CO 2 a role in exsheathment has been described previously, but the exact role of temperature was unclear. The current study is the first to investigate the importance of temperature in triggering exsheathment of Haemonchus contortus. Carbon dioxide induced exsheathment in H. contortus proved to be temperature dependent, as no exsheathment was observed at room temperatures. However, the temperature requirement to trigger exsheathment was quite specific. A rapid change in temperature (heat shock) very efficiently induced high levels of exsheathment. In contrast, when the larvae were exposed to a slow increase in temperature, the exsheathment response was smaller and delayed. Further investigation revealed that timing of the heat shock in relation to the CO 2 administration was crucial, as well as the final temperature and magnitude of the heat shock. In conclusion, these data indicate that heat shock rather than temperature itself is a crucial aspect in triggering the biological exsheathment cascade, and thus infection process, of H. contortus.

Laser shock processing effects on isothermal oxidation resistance of GH586 superalloy

NASA Astrophysics Data System (ADS)

Hua, Yinqun; Rong, Zhen; Ye, Yunxia; Chen, Kangmin; Chen, Ruifang; Xue, Qing; Liu, Haixia

2015-03-01

The oxidation is one of the main failure mode of Ni-based alloy at high temperature, laser shock processing not only can improve the mechanical properties but also the oxidation resistance. So the study on laser shock processing effects on oxidation resistance of this alloy is necessary. The aim of this paper is to investigate the effects of laser shock processing on microstructure, micro-hardness and isothermal oxidation resistance of GH586 superalloy. Scanning electron microscopy, energy-dispersive spectrum, transmission electron microscope, and X-ray diffraction technique were used to analyze the microstructure changes and the surface morphologies of the oxide scales. In addition, micro-hardness of LSP-treated samples was measured. The results show that the average grains size on the surfaces of LSP specimen was found to be significantly finer compared to the untreated one (33.3 μm vs. 18.5 μm). Highly tangled and dense dislocation arrangements and a high amount of twins have been observed. After the oxidation, the defects density (dislocations and twins) in the specimen decreased. The oxidation kinetics approximately followed a parabolic oxidation law at 800 °C and 900 °C. The oxidation layer was composed of Cr2O3, NiCr2O4, TiO2, and Al2O3, which generated more quickly on the surface treated by LSP during initial oxidation. The average oxidation rate was lower after LSP due to the dense, tiny and homogeneous oxidation layer. The results show that the specimens treated by LSP have a better high temperature oxidation resistance.

Barrier experiment: Shock initiation under complex loading

DOE Office of Scientific and Technical Information (OSTI.GOV)

Menikoff, Ralph

2016-01-12

The barrier experiments are a variant of the gap test; a detonation wave in a donor HE impacts a barrier and drives a shock wave into an acceptor HE. The question we ask is: What is the trade-off between the barrier material and threshold barrier thickness to prevent the acceptor from detonating. This can be viewed from the perspective of shock initiation of the acceptor subject to a complex pressure drive condition. Here we consider key factors which affect whether or not the acceptor undergoes a shock-to-detonation transition. These include the following: shock impedance matches for the donor detonation wavemore » into the barrier and then the barrier shock into the acceptor, the pressure gradient behind the donor detonation wave, and the curvature of detonation front in the donor. Numerical simulations are used to illustrate how these factors affect the reaction in the acceptor.« less

Collapsing Radiative Shocks in Xenon Gas on the Omega Laser

NASA Astrophysics Data System (ADS)

Reighard, A. B.; Glendinning, S. G.; Knauer, J.; Bouquet, S.; Koenig, M.

2005-10-01

A number of astrophysical systems involve radiative shocks that collapse spatially in response to energy lost through radiation, producing thin shells believed to be Vishniac unstable. We report experiments intended to study such collapsing shocks. The Omega laser drives a thin slab of material at >100 km/s through Xe gas. Simulations predict a collapsed layer in which the density reaches 45 times initial density. X-ray backlighting techniques have yielded images of a collapsed shock compressed to <1/25 its initial thickness (45 μm) at a speed of ˜100 km/s when the shock has traveled 1.3 mm. Optical depth before and behind the shock is important for comparison to astrophysical systems. This research was sponsored by the National Nuclear Security Administration under the Stewardship Science Academic Alliances program through DOE Research Grants DE-FG52-03NA00064, DE-FG53-2005-NA26014, and other grants and contracts.

Isolator fragmentation and explosive initiation tests

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dickson, Peter; Rae, Philip John; Foley, Timothy J.

2016-09-19

Three tests were conducted to evaluate the effects of firing an isolator in proximity to a barrier or explosive charge. The tests with explosive were conducted without a barrier, on the basis that since any barrier will reduce the shock transmitted to the explosive, bare explosive represents the worst-case from an inadvertent initiation perspective. No reaction was observed. The shock caused by the impact of a representative plastic material on both bare and cased PBX 9501 is calculated in the worst-case, 1-D limit, and the known shock response of the HE is used to estimate minimum run-to-detonation lengths. The estimatesmore » demonstrate that even 1-D impacts would not be of concern and that, accordingly, the divergent shocks due to isolator fragment impact are of no concern as initiating stimuli.« less

Isolator fragmentation and explosive initiation tests

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dickson, Peter; Rae, Philip John; Foley, Timothy J.

2015-09-30

Three tests were conducted to evaluate the effects of firing an isolator in proximity to a barrier or explosive charge. The tests with explosive were conducted without barrier, on the basis that since any barrier will reduce the shock transmitted to the explosive, bare explosive represents the worst-case from an inadvertent initiation perspective. No reaction was observed. The shock caused by the impact of a representative plastic material on both bare and cased PBX9501 is calculated in the worst-case, 1-D limit, and the known shock response of the HE is used to estimate minimum run-to-detonation lengths. The estimates demonstrate thatmore » even 1-D impacts would not be of concern and that, accordingly, the divergent shocks due to isolator fragment impact are of no concern as initiating stimuli.« less

Heat shock instructs hESCs to exit from the self-renewal program through negative regulation of OCT4 by SAPK/JNK and HSF1 pathway.

PubMed

Byun, Kyunghee; Kim, Taek-Kyun; Oh, Jeehyun; Bayarsaikhan, Enkhjargal; Kim, Daesik; Lee, Min Young; Pack, Chan-Gi; Hwang, Daehee; Lee, Bonghee

2013-11-01

Environmental factors affect self-renewal of stem cells by modulating the components of self-renewal networks. Heat shock, an environmental factor, induces heat shock factors (HSFs), which up-regulate stress response-related genes. However, the link of heat shock to self-renewal of stem cells has not been elucidated yet. Here, we present the direct link of heat shock to a core stem cell regulator, OCT4, in the self-renewal network through SAPK/JNK and HSF1 pathway. We first showed that heat shock initiated differentiation of human embryonic stem cells (hESCs). Gene expression analysis revealed that heat shock increased the expression of many genes involved in cellular processes related to differentiation of stem cells. We then examined the effects of HSFs induced by heat shock on core self-renewal factors. Among HSFs, heat shock induced mainly HSF1 in hESCs. The HSF1 repressed the expression of OCT4, leading to the differentiation of hESCs and the above differentiation-related gene expression change. We further examined the effects of the upstream MAP (mitogen-activated protein) kinases of HSF1 on the repression of OCT4 expression by HSF1. Among the MAP kinases, SAPK/JNK controlled predominantly the repression of the OCT4 expression by HSF1. The direct link of heat shock to the core self-renewal regulator through SAPK/JNK and HSF1 provides a fundamental basis for understanding the effect of heat and other stresses involving activation of HSF1 on the self-renewal program and further controlling differentiation of hESCs in a broad spectrum of stem cell applications using these stresses. © 2013.

An Equation of State for Foamed Divinylbenzene (DVB) Based on Multi-Shock Response

NASA Astrophysics Data System (ADS)

Aslam, Tariq; Schroen, Diana; Gustavsen, Richard; Bartram, Brian

2013-06-01

The methodology for making foamed Divinylbenzene (DVB) is described. For a variety of initial densities, foamed DVB is examined through multi-shock compression and release experiments. Results from multi-shock experiments on LANL's 2-stage gas gun will be presented. A simple conservative Lagrangian numerical scheme, utilizing total-variation-diminishing interpolation and an approximate Riemann solver, will be presented as well as the methodology of calibration. It has been previously demonstrated that a single Mie-Gruneisen fitting form can replicate foam multi-shock compression response at a variety of initial densities; such a methodology will be presented for foamed DVB.

Comparison Between Surf and Multi-Shock Forest Fire High Explosive Burn Models

DOE Office of Scientific and Technical Information (OSTI.GOV)

Greenfield, Nicholas Alexander

PAGOSA1 has several different burn models used to model high explosive detonation. Two of these, Multi-Shock Forest Fire and Surf, are capable of modeling shock initiation. Accurately calculating shock initiation of a high explosive is important because it is a mechanism for detonation in many accident scenarios (i.e. fragment impact). Comparing the models to pop-plot data give confidence that the models are accurately calculating detonation or lack thereof. To compare the performance of these models, pop-plots2 were created from simulations where one two cm block of PBX 9502 collides with another block of PBX 9502.

Simulations of Shock Wave Interaction with a Particle Cloud

NASA Astrophysics Data System (ADS)

Koneru, Rahul; Rollin, Bertrand; Ouellet, Frederick; Annamalai, Subramanian; Balachandar, S.'Bala'

2016-11-01

Simulations of a shock wave interacting with a cloud of particles are performed in an attempt to understand similar phenomena observed in dispersal of solid particles under such extreme environment as an explosion. We conduct numerical experiments in which a particle curtain fills only 87% of the shock tube from bottom to top. As such, the particle curtain upon interaction with the shock wave is expected to experience Kelvin-Helmholtz (KH) and Richtmyer-Meshkov (RM) instabilities. In this study, the initial volume fraction profile matches with that of Sandia Multiphase Shock Tube experiments, and the shock Mach number is limited to M =1.66. In these simulations we use a Eulerian-Lagrangian approach along with state-of-the-art point-particle force and heat transfer models. Measurements of particle dispersion are made at different initial volume fractions of the particle cloud. A detailed analysis of the evolution of the particle curtain with respect to the initial conditions is presented. This work was supported by the U.S. Department of Energy, National Nuclear Security Administration, Advanced Simulation and Computing Program, as a Cooperative Agreement under the Predictive Science Academic Alliance Program, Contract No. DE-NA0002378.

Laser-driven shock compression of gold foam in the terapascal pressure range

NASA Astrophysics Data System (ADS)

Liu, Wei; Duan, Xiaoxi; Jiang, Shaoen; Wang, Zhebin; Sun, Liang; Liu, Hao; Yang, Weiming; Zhang, Huan; Ye, Qing; Wang, Peng; Li, Yulong; Yi, Lin; Dong, Suo

2018-06-01

Shock compression experiments are carried out on gold foam with an initial density of 3.2 g/cm3 through indirectly laser-driven shock waves at the SG-III prototype laser facility. The impedance-matching technique is applied to determine the equation-of-state (EOS) data of the shocked gold foam. A passive shock breakout diagnostic system is employed to obtain the shock velocities in both the standard material and gold foam. The gold foams are compressed to a maximum density of 20 g/cm3 under a shock pressure of about 2 TPa. The effects of the unsteadiness of shock waves on the EOS measurement are quantitatively analyzed and corrected. The correction of unsteady waves, as well as the good planarity of the shock waves and the low preheating of the gold foam, contributes high-confidence EOS data for the gold foam. The corrected experimental data are compared with the Hugoniot states from the SESAME library. The comparison suggests that the database is suitable for describing the states of gold foam with an initial density of 3.2 g/cm3 under a pressure of about 2 TPa.

Dynamic evolutions of electron properties: A theoretical study for condensed-phase β-HMX under shock loading

NASA Astrophysics Data System (ADS)

He, Zheng-Hua; Chen, Jun; Wu, Qiang; Ji, Guang-Fu

2017-11-01

We present the density functional theory (DFT) calculations for microscopic electron properties of β-HMX under shock loading. The metallization pressure is determined to be within 30-55 GPa. The frontier molecular orbitals mainly localize on N-NO2 groups initially and disperse with pressure increase, while HOMO and LUMO orbitals trend to aggregate with each other. The deformation of N-NO2 groups and enhanced hydrogen-bonding interactions cause the electron delocalization and lower the band gap, inducing the reaction initiation finally. Our results show that using the electron properties can reliably predict the initial decomposition of energetic materials under shock loading.

Application of Time-resolved PIV to Supersonic Hot Jets

NASA Technical Reports Server (NTRS)

Bridges, James; Wernet, Mark P.

2007-01-01

This presentation lays out the ground-breaking work at bringing high-speed (25kHz) particle image velocimetry (PIV) to bear on measurements of noise-producing turbulence in hot jets. The work is still in progress in that the tremendous amount of data obtained are still be analyzed, but the method has been validated and initial results of interest to jet noise modeling have been obtained. After a brief demonstration of the validation process used on the data, results are shown for hot jets at different temperatures and Mach numbers. Comparisons of first order statistics show the relative indifference of the turbulence to the presence of shocks and independence to jet temperature. What does come out is that when the shock-containing jets are in a screech mode the turbulence is highly elevated, showing the importance of removing screech phenomena from model-scale jets before applying findings to full-scale aircraft which typically do not contain shocks.

The role of heat shock proteins in kidney disease

PubMed Central

2016-01-01

Abstract Heat Shock Proteins (HSP) belong to the family of intracellular proteins that are constitutively expressed and are upregulated by various stressors including heat, oxidative and chemical stress. HSP helps in reparative processes, including the refolding of damaged proteins and the removal of irreparably damaged proteins that would initiate cellular death or apoptosis. A growing body of evidence has expanded the role of HSP and defined their role in diseases such as neurodegenerative disorders, cancer, ischemic heart disease and kidney diseases. The protective role of HSP in ischemic renal injury has been described and HSP impairment has been noted in other forms of kidney injuries including post-transplant situation. Further research into the role of HSP in prevention of kidney injury is crucial if translation from the laboratory to patient bedside has to occur. This article aims to be a review of heat shock protein, and its relevance to kidney diseases. PMID:28191532

Chronic treatment with fluoxetine prevents the return of extinguished auditory-cued conditioned fear.

PubMed

Deschaux, Olivier; Spennato, Guillaume; Moreau, Jean-Luc; Garcia, René

2011-05-01

We have recently shown that post-extinction exposure of rats to a sub-threshold reminder shock can reactivate extinguished context-related freezing and found that chronic treatment with fluoxetine before fear extinction prevents this phenomenon. In the present study, we examined whether these findings would be confirmed with auditory fear conditioning. Rats were initially submitted to a session of five tone-shock pairings with either a 0.7- or 0.1-mA shock and underwent, 3 days later, a session of 20 tone-alone trials. At the beginning of this latter session, we observed cue-conditioned freezing in rats that received the strong, but not the weak, shock. At the end, both groups (strong and weak shocks) displayed similar low levels of freezing, indicating fear extinction in rats exposed to the strong shock. These rats exhibited again high levels of cue-evoked freezing when exposed to three tone-shock pairings with 0.1-mA shock. This reemergence of cue-conditioned fear was completely abolished by chronic (over a 21-day period) fluoxetine treatment which spared, when administered before the initial fear conditioning, the original tone-shock association. These data extend our previous findings and suggest that chronic fluoxetine treatment favor extinction memory by dampening the reactivation of the original tone-shock association.

Shock tubes and waves; Proceedings of the Thirteenth International Symposium, Niagara Falls, NY, July 6-9, 1981

NASA Astrophysics Data System (ADS)

Treanor, C. E.; Hall, J. G.

1982-10-01

The present conference on shock tubes and waves considers shock tube drivers, luminous shock tubes, shock tube temperature and pressure measurement, shock front distortion in real gases, nonlinear standing waves, transonic flow shock wave turbulent boundary interactions, wall roughness effects on reflected shock bifurcation, argon thermal conductivity, pattern generation in gaseous detonations, cylindrical resonators, shock tunnel-produced high gain lasers, fluid dynamic aspects of laser-metal interaction, and the ionization of argon gas behind reflected shock waves. Also discussed are the ionization relaxation of shock-heated plasmas and gases, discharge flow/shock tube studies of singlet oxygen, rotational and vibrational relaxation, chemiluminescence thermal and shock wave decomposition of hydrogen cyanide and hydrogen azide, shock wave structure in gas-particle mixtures at low Mach numbers, binary nucleation in a Ludwieg tube, shock liquefaction experiments, pipeline explosions, the shock wave ignition of pulverized coal, and shock-initiated methane combustion.

Measuring twinning and slip in shock-compressed Ta from in-situ x-ray diffraction

NASA Astrophysics Data System (ADS)

Wehrenberg, Christopher; McGonegle, David; Sliwa, Marcin; Suggit, Matt; Wark, Justin; Lee, Hae Ja; Nagler, Bob; Tavella, Franz; Remington, Bruce; Rudd, Rob; Lazicki, Amy; Park, Hye-Sook; Swift, Damian; Zepeda-Ruiz, Louis; Higginbotham, Andrew; Bolme, Cindy

2017-06-01

A fundamental understanding of high-pressure and high-strain-rate deformation rests on grasping the underlying microstructural processes, such as twinning and dislocation generation and transport (slip), yet simulations and ex-post-facto recovery experiments provide conflicting answers to these basic issues. Here, we report direct, in-situ observation of twinning and slip in shock compressed Ta using in-situ x-ray diffraction. A series of shock experiments were performed on the Matter in Extreme Conditions end station at LCLS. Direct laser ablation was used to drive a shock, ranging in pressure from 10-300 GPa, into a Ta sample with an initial (110) fiber texture. The subsequent changes in texture were observed in-situ by examining the azimuthal distribution of the diffraction intensity and found to match twinning and lattice rotation. Measurements of the twin fraction and lattice rotation were used to calculate the equivalent plastic strain from twinning and slip. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract No. DE-AC52-07NA27344.

Subgrain Rotation Behavior in Sn3.0Ag0.5Cu-Sn37Pb Solder Joints During Thermal Shock

NASA Astrophysics Data System (ADS)

Han, Jing; Tan, Shihai; Guo, Fu

2018-01-01

Ball grid array (BGA) samples were soldered on a printed circuit board with Sn37Pb solder paste to investigate the recrystallization induced by subgrain rotation during thermal shock. The composition of the solder balls was Sn3.0Ag0.5Cu-Sn37Pb, which comprised mixed solder joints. The BGA component was cross-sectioned before thermal shock. The microstructure and grain orientations were obtained by a scanning electron microscope equipped with an electron back-scattered diffraction system. Two mixed solder joints at corners of the BGA component were selected as the subjects. The results showed that recrystallization occurred at the corner of the solder joints after 200 thermal shock cycles. The recrystallized subgrains had various new grain orientations. The newly generated grain orientations were closely related to the initial grain orientations, which indicated that different subgrain rotation behaviors could occur in one mixed solder joint with the same initial grain orientation. When the misorientation angles were very small, the rotation axes were about Sn [100], [010] and [001], as shown by analyzing the misorientation angles and subgrain rotation axes, while the subgrain rotation behavior with large misorientation angles in the solder joints was much more complicated. As Pb was contained in the solder joints and the stress was concentrated on the corner of the mixed solder joints, concaves and cracks were formed. When the adjacent recrystallized subgrains were separated, and the process of the continuous recrystallization was limited.

Numerical study on dusty shock reflection over a double wedge

NASA Astrophysics Data System (ADS)

Yin, Jingyue; Ding, Juchun; Luo, Xisheng

2018-01-01

The dusty shock reflection over a double wedge with different length scales is systematically studied using an adaptive multi-phase solver. The non-equilibrium effect caused by the particle relaxation is found to significantly influence the shock reflection process. Specifically, it behaves differently for double wedges with different length scales of the first wedge L1. For a double wedge with L1 relatively longer than the particle relaxation length λ, the equilibrium shock dominates the shock reflection and seven typical reflection processes are obtained, which is similar to the pure gas counterpart. For a double wedge with L1 shorter than λ, the non-equilibrium effect manifests more evidently, i.e., three parts of the dusty shock system including the frozen shock, the relaxation zone, and the equilibrium shock together dominate the reflection process. As a result, the shock reflection is far more complicated than the pure gas counterpart and eleven transition processes are found under various wedge angles. These findings give a complete description of all possible processes of dusty shock reflection over a double wedge and may be useful for better understanding the non-equilibrium shock reflection over complex structures.

Volatile Behavior in Lunar and Terrestrial Basalts During Shock: Implications for Martian Magmas

NASA Technical Reports Server (NTRS)

Chaklader, Johny; Shearer, C. K.; Hoerz, F.; Newsom, H. E.

2004-01-01

The amount of water in martian magmas has significant ramifications for the martian atmosphere-hydrosphere cycle. Large D-enrichments have been observed in kaersutitic amphiboles in Zagami, Chassigny and Shergotty meteorites (delta-D values up to 4400 per mil) suggesting that substantial amounts of H escaped Mars in its past. Furthermore, martian meteorites with inclusions of biotite and apatite imply possible origins in a hydrous mantle. However, whether martian magmas ever possessed considerable proportions of water remains controversial and unclear. The H-content of mica and amphibole melt inclusions has been found to be low, while bulk-rock H2O content is also low ranging from 0.013 to 0.035 wt. % in Shergotty. Hydrous martian magmas were considered responsible for light lithophile element (LLE) zoning patterns observed in Nakhlite and Shergottite pyroxenes. Since LLEs, such as Li and B, partition into aqueous fluids at temperatures greater than 350 C, workers interpreted Li-B depletions in pyroxene rims as evidence that supercritical fluid exsolution occurred during magma degassing. In that many martian basalts experienced substantial shock (15-45 GPa) it is possible that the magmatic volatile record preserved in martian basalts has been disturbed. Previous shock experiments suggest that shock processes may effect water content and H/D. To better understand the possible effects of shock on this volatile record, we are studying the redistribution of volatile elements in naturally and experimentally shocked basalts. Here, we report the initial results from shocked basalts associated with the Lonar Crater, India and an experimentally shocked lunar basalt.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mao, Shoudi; He, Jiansen; Yang, Liping

The impact of an overtaking fast shock on a magnetic cloud (MC) is a pivotal process in CME–CME (CME: coronal mass ejection) interactions and CME–SIR (SIR: stream interaction region) interactions. MC with a strong and rotating magnetic field is usually deemed a crucial part of CMEs. To study the impact of a fast shock on an MC, we perform a 2.5 dimensional numerical magnetohydrodynamic simulation. Two cases are run in this study: without and with impact by fast shock. In the former case, the MC expands gradually from its initial state and drives a relatively slow magnetic reconnection with themore » ambient magnetic field. Analyses of forces near the core of the MC as a whole body indicates that the solar gravity is quite small compared to the Lorentz force and the pressure gradient force. In the second run, a fast shock propagates, relative to the background plasma, at a speed twice that of the perpendicular fast magnetosonic speed, catches up with and takes over the MC. Due to the penetration of the fast shock, the MC is highly compressed and heated, with the temperature growth rate enhanced by a factor of about 10 and the velocity increased to about half of the shock speed. The magnetic reconnection with ambient magnetic field is also sped up by a factor of two to four in reconnection rate as a result of the enhanced density of the current sheet, which is squeezed by the forward motion of the shocked MC.« less

Experimental study of shock-accelerated inclined heavy gas cylinder

DOE PAGES

Olmstead, Dell; Wayne, Patrick; Yoo, Jae-Hwun; ...

2017-05-23

An experimental study examines shock acceleration with an initially diffuse cylindrical column of sulfur hexafluoride surrounded by air and inclined with respect to the shock front. Three-dimensional vorticity deposition produces flow patterns whose evolution is captured with planar laser-induced fluorescence in two planes. Both planes are thus parallel to the direction of the shock propagation. The first plane is vertical and passes through the axis of the column. The second visualization plane is normal to the first plane and passes through the centerline of the shock tube. Vortex formation in the vertical and centerline planes is initially characterized by differentmore » rates and morphologies due to differences in initial vorticity deposition. In the vertical plane, the vortex structure manifests a periodicity that varies with Mach number. The dominant wavelength in the vertical plane can be related to the geometry and compressibility of the initial conditions. At later times, the vortex interaction produces a complex and irregular three-dimensional pattern suggesting transition to turbulence. We present highly repeatable experimental data for Mach numbers 1.13, 1.4, 1.7, and 2.0 at column incline angles of 0, 20, and 30 degrees for about 50 nominal cylinder diameters (30 cm) of downstream travel.« less

Cyclic behavior at quasi-parallel collisionless shocks

NASA Technical Reports Server (NTRS)

Burgess, D.

1989-01-01

Large scale one-dimensional hybrid simulations with resistive electrons have been carried out of a quasi-parallel high-Mach-number collisionless shock. The shock initially appears stable, but then exhibits cyclic behavior. For the magnetic field, the cycle consists of a period when the transition from upstream to downstream is steep and well defined, followed by a period when the shock transition is extended and perturbed. This cyclic shock solution results from upstream perturbations caused by backstreaming gyrating ions convecting into the shock. The cyclic reformation of a sharp shock transition can allow ions, at one time upstream because of reflection or leakage, to contribute to the shock thermalization.

Letter: Transient interaction between plasma jet and supersonic compression ramp flow

NASA Astrophysics Data System (ADS)

Huang, He-Xia; Tan, Hui-Jun; Sun, Shu; Zhang, Yu-Chao; Cheng, Lin

2018-04-01

The rapid flow evolution between a plasma jet and a 20° compression ramp flow is captured by a high-speed schlieren system at Mach 2.0. Several interesting flow phenomena are observed for the first time. The pulsed jet, which generates strong perturbations, forces the crossflow boundary layer to separate and forms a forward moving shock. A typical shock-on-shock interaction occurs when the precursor shock intersects with the original shock. The interaction is initially regular, and then it transforms into an irregular one with a Mach stem connecting the precursor shock and original ramp shock.

Simulations and experiments of ejecta generation in twice-shocked metals

NASA Astrophysics Data System (ADS)

Karkhanis, Varad; Ramaprabhu, Praveen; Buttler, William; Hammerberg, James; Cherne, Frank; Andrews, Malcolm

2016-11-01

Using continuum hydrodynamics embedded in the FLASH code, we model ejecta generation in recent target experiments, where a metallic surface was loaded by two successive shock waves. The experimental data were obtained from a two-shockwave, high-explosive tool at Los Alamos National Laboratory, capable of generating ejecta from a shocked tin surface in to a vacuum. In both simulations and experiment, linear growth is observed following the first shock event, while the second shock strikes a finite-amplitude interface leading to nonlinear growth. The timing of the second incident shock was varied systematically in our simulations to realize a finite-amplitude re-initialization of the RM instability driving the ejecta. We find the shape of the interface at the event of second shock is critical in determining the amount of ejecta, and thus must be used as an initial condition to evaluate subsequent ejected mass using a source model. In particular, the agreement between simulations, experiments and the mass model is improved when shape effects associated with the interface at second shock are incorporated. This work was supported in part by the (U.S.) Department of Energy (DOE) under Contract No. DE-AC52-06NA2-5396.

Shock wave and flame front induced detonation in a rapid compression machine

NASA Astrophysics Data System (ADS)

Wang, Y.; Qi, Y.; Xiang, S.; Mével, R.; Wang, Z.

2018-05-01

The present study focuses on one mode of detonation initiation observed in a rapid compression machine (RCM). This mode is referred to as shock wave and flame front-induced detonation (SWFID). Experimental high-speed imaging and two-dimensional numerical simulations with skeletal chemistry are combined to unravel the dominant steps of detonation initiation under SWFID conditions. It is shown that the interaction between the shock wave generated by the end-gas auto-ignition and the spherical flame creates a region of high pressure and temperature which enables the acceleration of the flame front and the detonation onset. The experimental observation lacks adequate spatial and temporal resolution despite good reproducibility of the detonation onset. Based on the numerical results, phenomenological interpretation of the event within the framework of shock wave refraction indicates that the formation of a free-precursor shock wave at the transition between regular and irregular refraction may be responsible for detonation onset. The present results along with previous findings on shock wave reflection-induced detonation in the RCM indicate that super-knock occurs after the interaction of the shock wave generated by end-gas auto-ignition with the RCM walls, preignition flame, or another shock wave.

Modeling deflagration waves out of hot spots

NASA Astrophysics Data System (ADS)

Partom, Yehuda

2017-01-01

It is widely accepted that shock initiation and detonation of heterogeneous explosives comes about by a two-step process known as ignition and growth. In the first step a shock sweeping through an explosive cell (control volume) creates hot spots that become ignition sites. In the second step, deflagration waves (or burn waves) propagate out of those hot spots and transform the reactant in the cell into reaction products. The macroscopic (or average) reaction rate of the reactant in the cell depends on the speed of those deflagration waves and on the average distance between neighboring hot spots. Here we simulate the propagation of deflagration waves out of hot spots on the mesoscale in axial symmetry using a 2D hydrocode, to which we add heat conduction and bulk reaction. The propagation speed of the deflagration waves may depend on both pressure and temperature. It depends on pressure for quasistatic loading near ambient temperature, and on temperature at high temperatures resulting from shock loading. From the simulation we obtain deflagration fronts emanating out of the hot spots. For 8 to 13 GPa shocks, the emanating fronts propagate as deflagration waves to consume the explosive between hot spots. For higher shock levels deflagration waves may interact with the sweeping shock to become detonation waves on the mesoscale. From the simulation results we extract average deflagration wave speeds.

Shock Mitigation in Open-Celled TiNi Foams

NASA Astrophysics Data System (ADS)

Jardine, A. Peter

2018-05-01

High-energy shock events generated by impacts are effectively mitigated by Nitinol materials. Initial evidence of this capability was suggested by the dramatically superior cavitation-erosion performance of Nitinol coatings made by plasma spray processes, over steels and brasses. A fast acting hysteretic stress-strain response mechanism was proposed to explain this result, transforming the shock energy into heat. Extending this work to bulk TiNi, dynamic load characterization using Split Rod Hopkinson Bar techniques on solid porous TiNi confirmed that the mechanical response to high strain rates below 4200 s-1 were indeed hysteretic. This paper reports on dynamical load characterization on TiNi foams made by Self-Propagating High-Temperature Synthesis (SHS) using Split Rod Hopkinson Bar and gas-gun impact characterization to compare these foams to alternative materials. This work verified that SHS-derived TiNi foams were indeed hysteretic at strain rates from 180 to 2300 s-1. In addition, Shock Spectrum Analysis demonstrated that TiNi foams were very effective in mitigating the shock spectrum range below 5 kHz, and that increasing porosity increased the amount of shock attenuation in that spectral range. Finally under impact loading, 55% porous TiNi foams were a factor of 7 superior to steel and a factor of 4 better than Al 6061 or Cu in mitigating peak g-loads and this attenuation improved with bilayer structures of 57 and 73% porous TiNi foam article.

Shock-induced compaction of nanoparticle layers into nanostructured coating

NASA Astrophysics Data System (ADS)

Mayer, Alexander E.; Ebel, Andrei A.

2017-10-01

A new process of shock wave consolidation of nanoparticles into a nanocrystalline coating is theoretically considered. In the proposed scheme, the nanoparticle layers, which are attached to the substrate surface by adhesion, are compacted by plane ultra-short shock waves coming from the substrate. The initial adhesion is self-arisen at any contact between the nanoparticles without a pre-compression. The absence of the nanoparticle ejections due to the shock wave action is connected with the strong adhesive forces, which allow nanoparticles to be attached to each other and to substrate while they are being compacted; this should be valid for small enough nanoparticles. Severe plastic deformation of the nanoparticles and the increased temperature due to collapse of voids between them facilitate their compaction into the monolithic nanocrystalline layer. We consider the examples of Cu and Ni nanoparticles on Al substrate using molecular dynamic simulations. We show the efficiency of the action of multiple shock waves with the duration in the range 2-20 ps and the amplitude in the range 4-12 GPa for sequential layerwise compaction of nanoparticles. A series of shock waves can be created by a repetitive powerful pulsed laser irradiation of the opposite surface of the substrate. The method offers the challenge for the formation of nanostructured coatings of various compositions. The thickness of the compacted nanocrystalline coating can be locally varied and controlled by the number of acting pulses.

Synchrotron hard X-ray imaging of shock-compressed metal powders

NASA Astrophysics Data System (ADS)

Rutherford, Michael E.; Chapman, David J.; Collinson, Mark A.; Jones, David R.; Music, Jasmina; Stafford, Samuel J. P.; Tear, Gareth R.; White, Thomas G.; Winters, John B. R.; Drakopoulos, Michael; Eakins, Daniel E.

2015-06-01

This poster will present the application of a new, high-energy (50 to 250 keV) synchrotron X-ray radiography technique to the study of shock-compressed granular materials. Following plate-impact loading, transmission radiography was used to quantitatively observe the compaction and release processes in a range of high-Z metal powders (e.g. Fe, Ni, Cu). By comparing the predictions of 3D numerical models initialized from X-ray tomograms-captured prior to loading-with experimental results, this research represents a new approach to refining mesoscopic compaction models. The authors gratefully acknowledge the ongoing support of Imperial College London, EPSRC, STFC and the Diamond Light Source, and AWE Plc.

[Acute heart failure: acute cardiogenic pulmonary edema and cardiogenic shock].

PubMed

Sánchez Marteles, Marta; Urrutia, Agustín

2014-03-01

Acute cardiogenic pulmonary edema and cardiogenic shock are two of the main forms of presentation of acute heart failure. Both entities are serious, with high mortality, and require early diagnosis and prompt and aggressive management. Acute pulmonary edema is due to the passage of fluid through the alveolarcapillary membrane and is usually the result of an acute cardiac episode. Correct evaluation and clinical identification of the process is essential in the management of acute pulmonary edema. The initial aim of treatment is to ensure hemodynamic stability and to correct hypoxemia. Other measures that can be used are vasodilators such as nitroglycerin, loop diuretics and, in specific instances, opioids. Cardiogenic shock is characterized by sustained hypoperfusion, pulmonary wedge pressure > 18 mmHg and a cardiac index < 2.2l/min/m(2). The process typically presents with hypotension (systolic blood pressure < 90 mmHg or a decrease in mean arterial pressure > 30 mmHg) and absent or reduced diuresis (< 0.5 ml/kg/h). The most common cause is left ventricular failure due to acute myocardial infarction. Treatment consists of general measures to reverse acidosis and hypoxemia, as well as the use of vasopressors and inotropic drugs. Early coronary revascularization has been demonstrated to improve survival in shock associated with ischaemic heart disease. Copyright © 2014 Elsevier España, S.L. All rights reserved.

Constitutively Active Acetylcholine-Dependent Potassium Current Increases Atrial Defibrillation Threshold by Favoring Post-Shock Re-Initiation

PubMed Central

Bingen, Brian O.; Askar, Saïd F. A.; Neshati, Zeinab; Feola, Iolanda; Panfilov, Alexander V.; de Vries, Antoine A. F.; Pijnappels, Daniël A.

2015-01-01

Electrical cardioversion (ECV), a mainstay in atrial fibrillation (AF) treatment, is unsuccessful in up to 10–20% of patients. An important aspect of the remodeling process caused by AF is the constitutive activition of the atrium-specific acetylcholine-dependent potassium current (IK,ACh → IK,ACh-c), which is associated with ECV failure. This study investigated the role of IK,ACh-c in ECV failure and setting the atrial defibrillation threshold (aDFT) in optically mapped neonatal rat cardiomyocyte monolayers. AF was induced by burst pacing followed by application of biphasic shocks of 25–100 V to determine aDFT. Blocking IK,ACh-c by tertiapin significantly decreased DFT, which correlated with a significant increase in wavelength during reentry. Genetic knockdown experiments, using lentiviral vectors encoding a Kcnj5-specific shRNA to modulate IK,ACh-c, yielded similar results. Mechanistically, failed ECV was attributed to incomplete phase singularity (PS) removal or reemergence of PSs (i.e. re-initiation) through unidirectional propagation of shock-induced action potentials. Re-initiation occurred at significantly higher voltages than incomplete PS-removal and was inhibited by IK,ACh-c blockade. Whole-heart mapping confirmed our findings showing a 60% increase in ECV success rate after IK,ACh-c blockade. This study provides new mechanistic insight into failing ECV of AF and identifies IK,ACh-c as possible atrium-specific target to increase ECV effectiveness, while decreasing its harmfulness. PMID:26487066

Shock wave viscosity measurements

NASA Astrophysics Data System (ADS)

Celliers, Peter

2013-06-01

Several decades ago a method was proposed and demonstrated to measure the viscosity of fluids at high pressure by observing the oscillatory damping of sinusoidal perturbations on a shock front. A detailed mathematical analysis of the technique carried out subsequently by Miller and Ahrens revealed its potential, as well as a deep level of complexity in the analysis. We revisit the ideas behind this technique in the context of a recent experimental development: two-dimensional imaging velocimetry. The new technique allows one to capture a broad spectrum of perturbations down to few micron scale-lengths imposed on a shock front from an initial perturbation. The detailed evolution of the perturbation spectrum is sensitive to the viscosity in the fluid behind the shock front. Initial experiments are aimed at examining the viscosity of shock compressed SiO2 just above the shock melting transition. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

Shock initiation of explosives: High temperature hot spots explained

NASA Astrophysics Data System (ADS)

Bassett, Will P.; Johnson, Belinda P.; Neelakantan, Nitin K.; Suslick, Kenneth S.; Dlott, Dana D.

2017-08-01

We investigated the shock initiation of energetic materials with a tabletop apparatus that uses km s-1 laser-driven flyer plates to initiate tiny explosive charges and obtains complete temperature histories with a high dynamic range. By comparing various microstructured formulations, including a pentaerythritol tetranitrate (PETN) based plastic explosive (PBX) denoted XTX-8003, we determined that micron-scale pores were needed to create high hot spot temperatures. In charges where micropores (i.e., micron-sized pores) were present, a hot spot temperature of 6000 K was observed; when the micropores were pre-compressed to nm scale, however, the hot spot temperature dropped to ˜4000 K. By comparing XTX-8003 with an analog that replaced PETN by nonvolatile silica, we showed that the high temperatures require gas in the pores, that the high temperatures were created by adiabatic gas compression, and that the temperatures observed can be controlled by the choice of ambient gases. The hot spots persist in shock-compressed PBXs even in vacuum because the initially empty pores became filled with gas created in-situ by shock-induced chemical decomposition.

Shock Initiation Experiments with Ignition and Growth Modeling on the HMX-Based Explosive LX-14

NASA Astrophysics Data System (ADS)

Vandersall, Kevin S.; Dehaven, Martin R.; Strickland, Shawn L.; Tarver, Craig M.; Springer, H. Keo; Cowan, Matt R.

2017-06-01

Shock initiation experiments on the HMX-based explosive LX-14 were performed to obtain in-situ pressure gauge data, characterize the run-distance-to-detonation behavior, and provide a basis for Ignition and Growth reactive flow modeling. A 101 mm diameter gas gun was utilized to initiate the explosive charges with manganin piezoresistive pressure gauge packages placed between sample disks pressed to different densities ( 1.57 or 1.83 g/cm3 that corresponds to 85 or 99% of theoretical maximum density (TMD), respectively). The shock sensitivity was found to increase with decreasing density as expected. Ignition and Growth model parameters were derived that yielded reasonable agreement with the experimental data at both initial densities. The shock sensitivity at the tested densities will be compared to prior work published on other HMX-based formulations. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. This work was funded in part by the Joint DoD-DOE Munitions Program.

Mathematical Modeling of the Heat-Shock Response in HeLa Cells

DTIC Science & Technology

2015-07-01

Petre et al. (16), but with some critical changes, which are detailed below. 2HSF4HSF2; (1) HSFþ HSF24HSF3; (2) HSF3 þ HSE4HSF3 : HSE ; (3) HSF3 : HSE ... HSE /HSP : HSFþ HSEþ 2HSF; (10) HSP/; (11) Prot/MFP; (12) HSPþMFP4HSP : MFP; (13) HSP : MFP/HSPþ Prot: (14) The heat-shock response is initiated by a... HSE , heat-shock element; HSF, heat-shock factor; HSP, heat-shock protein; MFP, misfolded protein; mRNA, heat-shock protein messenger RNA; and Prot

Non-thermal Processes in Colliding-wind Massive Binaries: the Contribution of Simbol-X to a Multiwavelength Investigation

NASA Astrophysics Data System (ADS)

De Becker, Michaël; Blomme, Ronny; Micela, Giusi; Pittard, Julian M.; Rauw, Gregor; Romero, Gustavo E.; Sana, Hugues; Stevens, Ian R.

2009-05-01

Several colliding-wind massive binaries are known to be non-thermal emitters in the radio domain. This constitutes strong evidence for the fact that an efficient particle acceleration process is at work in these objects. The acceleration mechanism is most probably the Diffusive Shock Acceleration (DSA) process in the presence of strong hydrodynamic shocks due to the colliding-winds. In order to investigate the physics of this particle acceleration, we initiated a multiwavelength campaign covering a large part of the electromagnetic spectrum. In this context, the detailed study of the hard X-ray emission from these sources in the SIMBOL-X bandpass constitutes a crucial element in order to probe this still poorly known topic of astrophysics. It should be noted that colliding-wind massive binaries should be considered as very valuable targets for the investigation of particle acceleration in a similar way as supernova remnants, but in a different region of the parameter space.

Shock initiation studies of low density HMX using electromagnetic particle velocity and PVDF stress gauges

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sheffield, S.A.; Gustavsen, R.L.; Alcon, R.R.

1993-09-01

Magnetic particle velocity and PVDF stress rate gauges have been used to measure the shock response of low density octotetramethylene tetranitramine (HMX) (1.24 &/cm{sup 3}). In experiments done at LANL, magnetic particle velocity gauges were located on both sides of the explosive. In nearly identical experiments done at SNL, PVDF stress rate gauges were located at the same positions so both particle velocity and stress histories were obtained for a particular experimental condition. Unreacted Hugoniot data were obtained and an EOS was developed by combining methods used by Hayes, Sheffield and Mitchell (for describing the Hugoniot of HNS at variousmore » densities) with Hermann`s P-{alpha} model. Using this technique, it is only necessary to know some thermodynamic constants or the Hugoniot of the initially solid material and the porous material sound speed to obtain accurate unreacted Hugoniots for the porous explosive. Loading and reaction paths were established in the stress-particle velocity plane for some experimental conditions. This information was used to determine a global reaction rate of {approx} 0.13 {mu}s{sup {minus}1} for porous HMX shocked to 0.8 GPa. At low input stresses the transmitted wave profiles had long rise times (up to 1 {mu}s) due to the compaction processes.« less

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.

Strength and viscosity effects on perturbed shock front stability in metals

DOE PAGES

Opie, Saul; Loomis, Eric Nicholas; Peralta, Pedro; ...

2017-05-09

Here, computational modeling and experimental measurements on metal samples subject to a laser-driven, ablative Richtmyer-Meshkov instability showed differences between viscosity and strength effects. In particular, numerical and analytical solutions, coupled with measurements of fed-through perturbations, generated by perturbed shock fronts onto initially flat surfaces, show promise as a validation method for models of deviatoric response in the post shocked material. Analysis shows that measurements of shock perturbation amplitudes at low sample thickness-to-wavelength ratios are not enough to differentiate between strength and viscosity effects, but that surface displacement data of the fed-through fed-thru perturbations appears to resolve the ambiguity. Additionally, analyticalmore » and numerical results show shock front perturbation evolution dependence on initial perturbation amplitude and wavelength is significantly different in viscous and materials with strength, suggesting simple experimental geometry changes should provide data supporting one model or the other.« less

Detonator Performance Characterization using Multi-Frame Laser Schlieren Imaging

NASA Astrophysics Data System (ADS)

Clarke, Steven; Landon, Colin; Murphy, Michael; Martinez, Michael; Mason, Thomas; Thomas, Keith

2009-06-01

Multi-frame Laser Schlieren Imaging of shock waves produced by detonators in transparent witness materials can be used to evaluate detonator performance. We use inverse calculations of the 2D propagation of shock waves in the EPIC finite element model computer code to calculate a temporal-spatial-pressure profile on the surface of the detonator that is consistent with the experimental shock waves from the schlieren imaging. Examples of calculated 2D temporal-spatial-pressure profiles from a range of detonator types (EFI --exploding foil initiators, DOI -- direct optical initiation, EBW -- exploding bridge wire, hotwire), detonator HE materials (PETN, HMX, etc), and HE densities. Also pressure interaction profiles from the interaction of multiple shock waves will be shown. LA-UR-09-00909.

Influence of Hot SPOT Features on the Shock Initiation of Heterogeneous Nitromethane

NASA Astrophysics Data System (ADS)

Dattelbaum, D. M.; Sheffield, S. A.; Stahl, D. B.; Dattelbaum, A. M.

2009-12-01

"Hot spots," or regions of localized high temperature and pressure that arise during the shock compression of heterogeneous materials, are known to highly influence the initiation characteristics of explosives. By introducing controlled-size particles at known number densities into otherwise homogeneous explosives, details about hot spot criticality can be mapped for a given material. Here, we describe a series of gas gun-driven plate impact experiments on nitromethane loaded with 40 μm silica beads at 6 wt%. Through the use of embedded electromagnetic gauges, we have gained insight into the initiation mechanisms as a function of the input shock pressure, and present a Pop-plot for the mixture, which is further compared to neat nitromethane.

Second sound shock waves and critical velocities in liquid helium 2. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Turner, T. N.

1979-01-01

Large amplitude second-sound shock waves were generated and the experimental results compared to the theory of nonlinear second-sound. The structure and thickness of second-sound shock fronts are calculated and compared to experimental data. Theoretically it is shown that at T = 1.88 K, where the nonlinear wave steepening vanishes, the thickness of a very weak shock must diverge. In a region near this temperature, a finite-amplitude shock pulse evolves into an unusual double-shock configuration consisting of a front steepened, temperature raising shock followed by a temperature lowering shock. Double-shocks are experimentally verified. It is experimentally shown that very large second-sound shock waves initiate a breakdown in the superfluidity of helium 2, which is dramatically displayed as a limit to the maximum attainable shock strength. The value of the maximum shock-induced relative velocity represents a significant lower bound to the intrinsic critical velocity of helium 2.

Laser-shock damage of iron-based materials

NASA Astrophysics Data System (ADS)

Chu, Jinn P.; Banas, Grzegorz; Lawrence, Frederick V.; Rigsbee, James M.; Elsayed-Ali, Hani E.

1993-05-01

The effects of laser shock processing on the microstructure and mechanical properties of the manganese (1 percent C and 14 percent Mn) steels have been low carbon (0.04 wt. percent C) and Hadfield studied. Laser shock processing was performed with a 1.054 micrometers wavelength Nd-phosphate laser operating in a pulse mode (600 ps pulse length and up to 200 J energy) with power densities above 10 to the 11th power W/cm2. Shock waves were generated by volume expansion of the plasma formed when the material was laser irradiated. Maximum shock wave intensities were obtained using an energy-absorbing black paint coating without a plasma-confining overlay. Maximum modification of compressive residual stresses were achieved when laser shock processing induced deformation occurred without melting. Mechanical properties were improved through modifying the microstructure by laser shock processing. High density arrays of dislocations (greater than 10 to the 11th power/cm2) were generated in low carbon steel by high strain-rate deformation of laser shock processing, resulting in surface hardness increases of 30 to 80 percent. In austenitic Hadfield steel, laser shock processing caused extensive formation of Epsilon-hcp martensite (35 vol. percent), producing increases of 50 to 130 percent in surface hardness. The laser shock processing strengthening effect in Hadfield steel was attributed to the combined effects of the partial dislocation/stacking fault arrays and the grain refinement due to presence of the Epsilon-hcp martensite.

Shock timing experiments on the National Ignition Facility: Initial results and comparison with simulation

NASA Astrophysics Data System (ADS)

Robey, H. F.; Boehly, T. R.; Celliers, P. M.; Eggert, J. H.; Hicks, D.; Smith, R. F.; Collins, R.; Bowers, M. W.; Krauter, K. G.; Datte, P. S.; Munro, D. H.; Milovich, J. L.; Jones, O. S.; Michel, P. A.; Thomas, C. A.; Olson, R. E.; Pollaine, S.; Town, R. P. J.; Haan, S.; Callahan, D.; Clark, D.; Edwards, J.; Kline, J. L.; Dixit, S.; Schneider, M. B.; Dewald, E. L.; Widmann, K.; Moody, J. D.; Döppner, T.; Radousky, H. B.; Throop, A.; Kalantar, D.; DiNicola, P.; Nikroo, A.; Kroll, J. J.; Hamza, A. V.; Horner, J. B.; Bhandarkar, S. D.; Dzenitis, E.; Alger, E.; Giraldez, E.; Castro, C.; Moreno, K.; Haynam, C.; LaFortune, K. N.; Widmayer, C.; Shaw, M.; Jancaitis, K.; Parham, T.; Holunga, D. M.; Walters, C. F.; Haid, B.; Mapoles, E. R.; Sater, J.; Gibson, C. R.; Malsbury, T.; Fair, J.; Trummer, D.; Coffee, K. R.; Burr, B.; Berzins, L. V.; Choate, C.; Brereton, S. J.; Azevedo, S.; Chandrasekaran, H.; Eder, D. C.; Masters, N. D.; Fisher, A. C.; Sterne, P. A.; Young, B. K.; Landen, O. L.; Van Wonterghem, B. M.; MacGowan, B. J.; Atherton, J.; Lindl, J. D.; Meyerhofer, D. D.; Moses, E.

2012-04-01

Capsule implosions on the National Ignition Facility (NIF) [Lindl et al., Phys. Plasmas 11, 339 (2004)] are underway with the goal of compressing deuterium-tritium (DT) fuel to a sufficiently high areal density (ρR) to sustain a self-propagating burn wave required for fusion power gain greater than unity. These implosions are driven with a carefully tailored sequence of four shock waves that must be timed to very high precision in order to keep the DT fuel on a low adiabat. Initial experiments to measure the strength and relative timing of these shocks have been conducted on NIF in a specially designed surrogate target platform known as the keyhole target. This target geometry and the associated diagnostics are described in detail. The initial data are presented and compared with numerical simulations. As the primary goal of these experiments is to assess and minimize the adiabat in related DT implosions, a methodology is described for quantifying the adiabat from the shock velocity measurements. Results are contrasted between early experiments that exhibited very poor shock timing and subsequent experiments where a modified target geometry demonstrated significant improvement.

Experiments on the Richtmyer–Meshkov instability with an imposed, random initial perturbation

DOE PAGES

Jacobs, J. W.; Krivets, V. V.; Tsiklashvili, V.; ...

2013-03-16

A vertical shock tube is used to perform experiments on the Richtmyer–Meshkov instability with a three-dimensional random initial perturbation. A membraneless flat interface is formed by opposed gas flows in which the light and heavy gases enter the shock tube from the top and from the bottom of the shock tube driven section. An air/SF6 gas combination is used and a Mach number M = 1.2 incident shock wave impulsively accelerates the interface. Initial perturbations on the interface are created by vertically oscillating the gas column within the shock tube to produce Faraday waves on the interface resulting in amore » short wavelength, three-dimensional perturbation. Planar Mie scattering is used to visualize the flow in which light from a laser sheet is scattered by smoke seeded in the air, and image sequences are captured using three high-speed video cameras. Measurements of the integral penetration depth prior to reshock show two growth behaviors, both having power law growth with growth exponents in the range found in previous experiments and simulations. Following reshock, all experiments showvery consistent linear growth with a growth rate in good agreement with those found in previous studies.« less

On beyond the standard model for high explosives: challenges & obstacles to surmount

DOE Office of Scientific and Technical Information (OSTI.GOV)

Menikoff, Ralph Ds

2009-01-01

Plastic-bonded explosives (PBX) are heterogeneous materials. Nevertheless, current explosive models treat them as homogeneous materials. To compensate, an empirically determined effective burn rate is used in place of a chemical reaction rate. A significant limitation of these models is that different burn parameters are needed for applications in different regimes; for example, shock initiation of a PBX at different initial temperatures or different initial densities. This is due to temperature fluctuations generated when a heterogeneous material is shock compressed. Localized regions of high temperatures are called hot spots. They dominate the reaction for shock initiation. The understanding of hot spotmore » generation and their subsequent evolution has been limited by the inability to measure transients on small spatial ({approx} 1 {micro}m) and small temporal ({approx} 1 ns) scales in the harsh environment of a detonation. With the advances in computing power, it is natural to try and gain an understanding of hot-spot initiation with numerical experiments based on meso-scale simulations that resolve material heterogeneities and utilize realistic chemical reaction rates. However, to capture the underlying physics correctly, such high resolution simulations will require more than fast computers with a large amount of memory. Here we discuss some of the issues that need to be addressed. These include dissipative mechanisms that generate hot spots, accurate thermal propceties for the equations of state of the reactants and products, and controlling numerical entropy error from shock impedance mismatches at material interfaces. The later can generate artificial hot spots and lead to premature reaction. Eliminating numerical hot spots is critical for shock initiation simulations due to the positive feedback between the energy release from reaction and the hydrodynamic flow.« less

Influence of hot spot features on the initiation characteristics of heterogeneous nitromethane

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dattelbaum, Dana M; Sheffield, Stephen A; Stahl, David B

2010-01-01

To gain insights into the critical hot spot features influencing energetic materials initiation characteristics, well-defined micron-scale particles have been intentionally introduced into the homogeneous explosive nitromethane (NM). Two types of potential hot spot origins have been examined - shock impedance mismatches using solid silica beads, and porosity using hollow microballoons - as well as their sizes and inter-particle separations. Here, we present the results of several series of gas gun-driven plate impact experiments on NM/particle mixtures with well-controlled shock inputs. Detailed insights into the nature of the reactive flow during the build-up to detonation have been obtained from the responsemore » of in-situ electromagnetic gauges, and the data have been used to establish Pop-plots (run-distance-to-detonation vs. shock input pressure) for the mixtures. Comparisons of sensitization effects and energy release characteristics relative to the initial shock front between the solid and hollow beads are presented.« less

Characterizing detonator output using dynamic witness plates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Murphy, Michael John; Adrian, Ronald J

2009-01-01

A sub-microsecond, time-resolved micro-particle-image velocimetry (PIV) system is developed to investigate the output of explosive detonators. Detonator output is directed into a transparent solid that serves as a dynamic witness plate and instantaneous shock and material velocities are measured in a two-dimensional plane cutting through the shock wave as it propagates through the solid. For the case of unloaded initiators (e.g. exploding bridge wires, exploding foil initiators, etc.) the witness plate serves as a surrogate for the explosive material that would normally be detonated. The velocity-field measurements quantify the velocity of the shocked material and visualize the geometry of themore » shocked region. Furthermore, the time-evolution of the velocity-field can be measured at intervals as small as 10 ns using the PIV system. Current experimental results of unloaded exploding bridge wire output in polydimethylsiloxane (PDMS) witness plates demonstrate 20 MHz velocity-field sampling just 300 ns after initiation of the wire.« less

Equation of state of fluid helium at high temperatures and densities

NASA Astrophysics Data System (ADS)

Cai, Lingcang; Chen, Qifeng; Gu, Yunjun; Zhang, Ying; Zhou, Xianming; Jing, Fuqian

2005-03-01

Hugoniot curves and shock temperatures of gas helium with initial temperature 293 K and three initial pressures 0.6, 1.2, and 5.0 MPa were measured up to 15000 K using a two-stage light-gas gun and transient radiation pyrometer. It was found that the calculated Hugoniot EOS of gas helium at the same initial pressure using Saha equation with Debye-Hückel correction was in good agreement with the experimental data. The curve of the calculated shock wave velocity with the particle velocity of gas helium which is shocked from the initial pressure 5 MPa and temperature 293 K, i.e., the D ≈ u relation, D= C 0+λ u ( u<10 km/s, λ=1.32) in a low pressure region, is approximately parallel with the fitted D ≈ u (λ=1.36) of liquid helium from the experimental data of Nellis et al. Our calculations show that the Hugoniot parameter λ is independent of the initial density p{in0}. The D≈ u curves of gas helium will transfer to another one and approach a limiting value of compression when their temperature elevates to about 18000 K and the ionization degree of the shocked gas helium reaches 10-3.

External front instabilities induced by a shocked particle ring.

PubMed

Rodriguez, V; Saurel, R; Jourdan, G; Houas, L

2014-10-01

The dispersion of a cylindrical particle ring by a blast or shock wave induces the formation of coherent structures which take the form of particle jets. A blast wave, issuing from the discharge of a planar shock wave at the exit of a conventional shock tube, is generated in the center of a granular medium ring initially confined inside a Hele-Shaw cell. With the present experimental setup, under impulsive acceleration, a solid particle-jet formation is observed in a quasi-two-dimensional configuration. The aim of the present investigation is to observe in detail the formation of very thin perturbations created around the external surface of the dispersed particle layer. By means of fast flow visualization with an appropriate recording window, we focus solely on the first instants during which the external particle ring becomes unstable. We find that the critical area of the destabilization of the external ring surface is constant regardless of the acceleration of the initial layer. Moreover, we observe in detail the external front perturbation wavelength, rendered dimensionless by the initial ring perimeter, and follow its evolution with the initial particle layer acceleration. We report this quantity to be constant regardless of the evolution of the initial particle layer acceleration. Finally, we can reasonably assert that external front perturbations depend solely on the material of the particles.

Appropriate evaluation and treatment of heart failure patients after implantable cardioverter-defibrillator discharge: time to go beyond the initial shock.

PubMed

Mishkin, Joseph D; Saxonhouse, Sherry J; Woo, Gregory W; Burkart, Thomas A; Miles, William M; Conti, Jamie B; Schofield, Richard S; Sears, Samuel F; Aranda, Juan M

2009-11-24

Multiple clinical trials support the use of implantable cardioverter-defibrillators (ICDs) for prevention of sudden cardiac death in patients with heart failure (HF). Unfortunately, several complicating issues have arisen from the universal use of ICDs in HF patients. An estimated 20% to 35% of HF patients who receive an ICD for primary prevention will experience an appropriate shock within 1 to 3 years of implant, and one-third of patients will experience an inappropriate shock. An ICD shock is associated with a 2- to 5-fold increase in mortality, with the most common cause being progressive HF. The median time from initial ICD shock to death ranges from 168 to 294 days depending on HF etiology and the appropriateness of the ICD therapy. Despite this prognosis, current guidelines do not provide a clear stepwise approach to managing these high-risk patients. An ICD shock increases HF event risk and should trigger a thorough evaluation to determine the etiology of the shock and guide subsequent therapeutic interventions. Several combinations of pharmacologic and device-based interventions such as adding amiodarone to baseline beta-blocker therapy, adjusting ICD sensitivity, and employing antitachycardia pacing may reduce future appropriate and inappropriate shocks. Aggressive HF surveillance and management is required after an ICD shock, as the risk of sudden cardiac death is transformed to an increased HF event risk.

Adiabat-shaping in indirect drive inertial confinement fusion

DOE PAGES

Baker, K. L.; Robey, H. F.; Milovich, J. L.; ...

2015-05-05

Adiabat-shaping techniques were investigated in this paper in indirect drive inertial confinement fusion experiments on the National Ignition Facility as a means to improve implosion stability, while still maintaining a low adiabat in the fuel. Adiabat-shaping was accomplished in these indirect drive experiments by altering the ratio of the picket and trough energies in the laser pulse shape, thus driving a decaying first shock in the ablator. This decaying first shock is designed to place the ablation front on a high adiabat while keeping the fuel on a low adiabat. These experiments were conducted using the keyhole experimental platform formore » both three and four shock laser pulses. This platform enabled direct measurement of the shock velocities driven in the glow-discharge polymer capsule and in the liquid deuterium, the surrogate fuel for a DT ignition target. The measured shock velocities and radiation drive histories are compared to previous three and four shock laser pulses. This comparison indicates that in the case of adiabat shaping the ablation front initially drives a high shock velocity, and therefore, a high shock pressure and adiabat. The shock then decays as it travels through the ablator to pressures similar to the original low-adiabat pulses when it reaches the fuel. Finally, this approach takes advantage of initial high ablation velocity, which favors stability, and high-compression, which favors high stagnation pressures.« less

Observations and simulations of specularly reflected He++ at Earth's quasiperpendicular bow shock

NASA Astrophysics Data System (ADS)

Broll, J. M.; Fuselier, S. A.; Trattner, K. J.; Anderson, B. J.; Burch, J. L.; Giles, B. L.

2016-12-01

Specular reflection of protons at Earth's quasiperpendicular bow shock is an important process for supercritical shock dissipation. Previous studies have found evidence of He++ specular reflection from reduced particle distributions downstream from the shock, but confirmation of the process for heavier ions in the shock foot was not possible due to time resolution constraints. We present He++ distributions, observed by MMS in a quasiperpendicular bow shock crossing, that are consistent with specularly reflected He++. We also investigate the He++ dynamics with test-particle simulations in a simulated shock based on this crossing and we conduct wave analysis to determine what processes lead to separate gyrotropization timescales for the transmitted and reflected populations.

Jet formation of SF6 bubble induced by incident and reflected shock waves

NASA Astrophysics Data System (ADS)

Zhu, Yuejin; Yu, Lei; Pan, Jianfeng; Pan, Zhenhua; Zhang, Penggang

2017-12-01

The computational results of two different cases on the evolution of the shock-SF6 heavy bubble interaction are presented. The shock focusing processes and jet formation mechanisms are analyzed by using the high resolution of computation schemes, and the influence of reflected shock waves is also investigated. It is concluded that there are two steps in the shock focusing process behind the incident shock wave, and the density and pressure values increase distinctly when the shock focusing process is completed. The local high pressure and vorticities in the vicinity of the downstream pole can propel the formation of the jet behind the incident shock wave. In addition, the gas is with the rightward velocity before the reflected shock wave impinges on the bubble; therefore, the evolutions of the waves and the bubble are more complicated when the reflected shock wave impinges on the SF6 bubble. Furthermore, the different end wall distances would affect the deformation degree of the bubble before the interaction of the reflected shock wave; therefore, the different left jet formation processes are found after the impingement of reflected shock waves when L = 27 mm. The local high pressure zones in the vicinity of the left bubble interface and the impingement of different shock waves can induce the local gas to shift the rightward velocity to the leftward velocity, which can further promote the formation of jets.

Study on Subgrain Rotation Behavior at Different Interfaces of a Solder Joint During Thermal Shock

NASA Astrophysics Data System (ADS)

Han, Jing; Tan, Shihai; Guo, Fu

2016-12-01

In order to investigate subgrain rotation behavior in the recrystallized region of lead-free solder joints, a ball grid array (BGA) specimen with a cross-sectioned edge row was thermally shocked. Electron backscattered diffraction (EBSD) was used to obtain the microstructure and orientations of Sn grains or subgrains in as-reflowed and thermally shocked conditions. Orientation imaging microscopy (OIM) showed that several subgrains were formed at the tilted twin grain boundaries, near the chip side and near the printed circuit board (PCB) side after 200 thermal shocks due to a highly mismatched coefficient of thermal expansion (CTE) of twin grains. Also, subgrains formed at the chip side and PCB side in the solder joint were selected to research the grain rotation behavior in lead-free solder joints. The analysis of subgrain rotation also indicated that the rotation behavior of subgrains was different between the chip side and PCB side. It was closely related with the large different crystal orientations between the chip side and PCB side. Furthermore, electron backscattered patterns (EBSPs) at several parts of the joint were not obtained after 300 thermal shocks due to the serious deformation caused by mismatched CTE during thermal shock. But 4 subgrains were selected and compared with that of the initial state and 200-thermal shock conditions. The results showed that the subgrains at the chip side were also rotated around the Sn [101] and [001] axes and the subgrains at the PCB side were also rotated around the Sn [100] axis, which indicated a continuous process of subgrain rotation.

Exact Analytic Solution for a Ballistic Orbiting Wind

NASA Astrophysics Data System (ADS)

Wilkin, Francis P.; Hausner, Harry

2017-07-01

Much theoretical and observational work has been done on stellar winds within binary systems. We present a new solution for a ballistic wind launched from a source in a circular orbit. The solution is that of a single wind—no second wind is included in the system and the shocks that arise are those due to the orbiting wind interacting with itself. Our method emphasizes the curved streamlines in the corotating frame, where the flow is steady-state, allowing us to obtain an exact solution for the mass density at all pre-shock locations. Assuming an initially isotropic wind, fluid elements launched from the interior hemisphere of the wind will be the first to cross other streamlines, resulting in a spiral structure bounded by two shock surfaces. Streamlines from the outer wind hemisphere later intersect these shocks as well. An analytic solution is obtained for the geometry of the two shock surfaces. Although the inner and outer shock surfaces asymptotically trace Archimedean spirals, our tail solution suggests many crossings where the shocks overlap, beyond which the analytic solution cannot be continued. Our solution can be readily extended to an initially anisotropic wind.

Simulation and characterization of a laterally-driven inertial micro-switch

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Wenguo; Wang, Yang; Wang, Huiying

2015-04-15

A laterally-driven inertial micro-switch was designed and fabricated using surface micromachining technology. The dynamic response process was simulated by ANSYS software, which revealed the vibration process of movable electrode when the proof mass is shocked by acceleration in sensitive direction. The test results of fabricated inertial micro-switches with and without anti-shock beams indicated that the contact process of micro-switch with anti-shock beams is more reliable than the one without anti-shock beams. The test results indicated that three contact signals had been observed in the contact process of the inertial switch without anti-shock beams, and only one contact signal in themore » inertial switch with anti-shock beams, which demonstrated that the anti-shock beams can effectively constrain the vibration in non-sensitive direction.« less

Simulations of the Richtmyer-Meshkov Instability with experimentally measured volumetric initial conditions

NASA Astrophysics Data System (ADS)

Ferguson, Kevin; Sewell, Everest; Krivets, Vitaliy; Greenough, Jeffrey; Jacobs, Jeffrey

2016-11-01

Initial conditions for the Richtmyer-Meshkov instability (RMI) are measured in three dimensions in the University of Arizona Vertical Shock Tube using a moving magnet galvanometer system. The resulting volumetric data is used as initial conditions for the simulation of the RMI using ARES at Lawrence-Livermore National Laboratory (LLNL). The heavy gas is sulfur hexafluoride (SF6), and the light gas is air. The perturbations are generated by harmonically oscillating the gasses vertically using two loudspeakers mounted to the shock tube which cause Faraday resonance, producing a random short wavelength perturbation on the interface. Planar Mie scattering is used to illuminate the flow field through the addition of propylene glycol particles seeded in the heavy gas. An M=1.2 shock impulsively accelerates the interface, initiating instability growth. Images of the initial condition and instability growth are captured at a rate of 6 kHz using high speed cameras. Comparisons between experimental and simulation results, mixing diagnostics, and mixing zone growth are presented.

Simulation and analysis of collapsing vapor-bubble clusters with special emphasis on potentially erosive impact loads at walls

NASA Astrophysics Data System (ADS)

Ogloblina, Daria; Schmidt, Steffen J.; Adams, Nikolaus A.

2018-06-01

Cavitation is a process where a liquid evaporates due to a pressure drop and re-condenses violently. Noise, material erosion and altered system dynamics characterize for such a process for which shock waves, rarefaction waves and vapor generation are typical phenomena. The current paper presents novel results for collapsing vapour-bubble clusters in a liquid environment close to a wall obtained by computational fluid mechanics (CFD) simulations. The driving pressure initially is 10 MPa in the liquid. Computations are carried out by using a fully compressible single-fluid flow model in combination with a conservative finite volume method (FVM). The investigated bubble clusters (referred to as "clouds") differ by their initial vapor volume fractions, initial stand-off distances to the wall and by initial bubble radii. The effects of collapse focusing due to bubble-bubble interaction are analysed by investigating the intensities and positions of individual bubble collapses, as well as by the resulting shock-induced pressure field at the wall. Stronger interaction of the bubbles leads to an intensification of the collapse strength for individual bubbles, collapse focusing towards the center of the cloud and enhanced re-evaporation. The obtained results reveal collapse features which are common for all cases, as well as case-specific differences during collapse-rebound cycles. Simultaneous measurements of maximum pressures at the wall and within the flow field and of the vapor volume evolution show that not only the primary collapse but also subsequent collapses are potentially relevant for erosion.

Scaling craters in carbonates: Electron paramagnetic resonance analysis of shock damage

NASA Technical Reports Server (NTRS)

Polanskey, Carol A.; Ahrens, Thomas J.

1994-01-01

Carbonate samples from the 8.9-Mt nuclear (near-surface explosion) crater, OAK, and a terrestrial impact crater, Meteor Crater, were analyzed for shock damage using electron paramagnetic resonance (EPR). Samples from below the OAK apparent crater floor were obtained from six boreholes, as well as ejecta recovered from the crater floor. The degree of shock damage in the carbonate material was assessed by comparing the sample spectra to the spectra of Solenhofen and Kaibab limestone, which had been skocked to known pressures. Analysis of the OAK Crater borehole samples has identified a thin zone of allocthonous highly shocked (10-13 GPa) carbonate material underneath the apparent crater floor. This approx. 5- to 15-m-thick zone occurs at a maximum depth of approx. 125 m below current seafloor at the borehole, sited at the initial position of the OAK explosive, and decreases in depth towards the apparent crater edge. Because this zone of allocthonous shocked rock delineates deformed rock below, and a breccia of mobilized sand and collapse debris above, it appears to outline the transient crater. The transient crater volume inferred in this way is found to by 3.2 +/- 0.2 times 10(exp 6)cu m, which is in good agreement with a volume of 5.3 times 10(exp 6)cu m inferred from gravity scaling of laboratory experiments. A layer of highly shocked material is also found near the surface outside the crater. The latter material could represent a fallout ejecta layer. The ejecta boulders recovered from the present crater floor experienced a range of shock pressures from approx. 0 to 15 GPa with the more heavily shocked samples all occurring between radii of 360 and approx. 600 m. Moreover, the fossil content, lithology and Sr isotopic composition all demonstrate that the initial position of the bulk of the heavily shocked rock ejecta sampled was originally near surface rock at initial depths in the 32 to 45-m depth (below sea level) range. The EPR technique is also sensitive to prehistoric shock damage. This is demonstrated by our study of shocked Kaibab limestone from the 49,000-year-old Meteor (Barringer) Crater Arizona.

X3 expansion tube driver gas spectroscopy and temperature measurements

NASA Astrophysics Data System (ADS)

Parekh, V.; Gildfind, D.; Lewis, S.; James, C.

2018-07-01

The University of Queensland's X3 facility is a large, free-piston driven expansion tube used for super-orbital and high Mach number scramjet aerothermodynamic studies. During recent development of new scramjet test flow conditions, experimentally measured shock speeds were found to be significantly lower than that predicted by initial driver performance calculations. These calculations were based on ideal, isentropic compression of the driver gas and indicated that loss mechanisms, not accounted for in the preliminary analysis, were significant. The critical determinant of shock speed is peak driver gas sound speed, which for a given gas composition depends on the peak driver gas temperature. This temperature may be inaccurately estimated if an incorrect fill temperature is assumed, or if heat losses during driver gas compression are significant but not accounted for. For this study, the ideal predicted peak temperature was 3750 K, without accounting for losses. However, a much lower driver temperature of 2400 K is suggested based on measured experimental shock speeds. This study aimed to measure initial and peak driver gas temperatures for a representative X3 operating condition. Examination of the transient temperatures of the driver gas and compression tube steel wall during the initial fill process showed that once the filling process was complete, the steady-state driver gas temperature closely matched the tube wall temperature. Therefore, while assuming the gas is initially at the ambient laboratory temperature is not a significant source of error, it can be entirely mitigated by simply monitoring tube wall temperature. Optical emission spectroscopy was used to determine the driver gas spectra after diaphragm rupture; the driver gas emission spectrum exhibited a significant continuum radiation component, with prominent spectral lines attributed to contamination of the gas. A graybody approximation of the continuum suggested a peak driver gas temperature of 3200 K; uncertainty associated with the blackbody curve fit is ±100 K. However, work is required to quantify additional sources of uncertainty due to the graybody assumption and the presence of contaminant particles in the driver gas; these are potentially significant. The estimate of the driver gas temperature suggests that driver heat losses are not the dominant contributor to the lower-than-expected shock speeds for X3. Since both the driver temperature and pressure have been measured, investigation of total pressure losses during driver gas expansion across the diaphragm and driver-to-driven tube area change (currently not accounted for) is recommended for future studies as the likely mechanism for the observed performance gap.

X3 expansion tube driver gas spectroscopy and temperature measurements

NASA Astrophysics Data System (ADS)

Parekh, V.; Gildfind, D.; Lewis, S.; James, C.

2017-11-01

The University of Queensland's X3 facility is a large, free-piston driven expansion tube used for super-orbital and high Mach number scramjet aerothermodynamic studies. During recent development of new scramjet test flow conditions, experimentally measured shock speeds were found to be significantly lower than that predicted by initial driver performance calculations. These calculations were based on ideal, isentropic compression of the driver gas and indicated that loss mechanisms, not accounted for in the preliminary analysis, were significant. The critical determinant of shock speed is peak driver gas sound speed, which for a given gas composition depends on the peak driver gas temperature. This temperature may be inaccurately estimated if an incorrect fill temperature is assumed, or if heat losses during driver gas compression are significant but not accounted for. For this study, the ideal predicted peak temperature was 3750 K, without accounting for losses. However, a much lower driver temperature of 2400 K is suggested based on measured experimental shock speeds. This study aimed to measure initial and peak driver gas temperatures for a representative X3 operating condition. Examination of the transient temperatures of the driver gas and compression tube steel wall during the initial fill process showed that once the filling process was complete, the steady-state driver gas temperature closely matched the tube wall temperature. Therefore, while assuming the gas is initially at the ambient laboratory temperature is not a significant source of error, it can be entirely mitigated by simply monitoring tube wall temperature. Optical emission spectroscopy was used to determine the driver gas spectra after diaphragm rupture; the driver gas emission spectrum exhibited a significant continuum radiation component, with prominent spectral lines attributed to contamination of the gas. A graybody approximation of the continuum suggested a peak driver gas temperature of 3200 K; uncertainty associated with the blackbody curve fit is ±100 K. However, work is required to quantify additional sources of uncertainty due to the graybody assumption and the presence of contaminant particles in the driver gas; these are potentially significant. The estimate of the driver gas temperature suggests that driver heat losses are not the dominant contributor to the lower-than-expected shock speeds for X3. Since both the driver temperature and pressure have been measured, investigation of total pressure losses during driver gas expansion across the diaphragm and driver-to-driven tube area change (currently not accounted for) is recommended for future studies as the likely mechanism for the observed performance gap.

Vortex ring formation at the open end of a shock tube: A particle image velocimetry study

NASA Astrophysics Data System (ADS)

Arakeri, J. H.; Das, D.; Krothapalli, A.; Lourenco, L.

2004-04-01

The vortex ring generated subsequent to the diffraction of a shock wave from the open end of a shock tube is studied using particle image velocimetry. We examine the early evolution of the compressible vortex ring for three-exit shock Mach numbers, 1.1, 1.2, and 1.3. For the three cases studied, the ring formation is complete at about tUb/D=2, where t is time, Ub is fluid velocity behind shock as it exits the tube and D is tube diameter. Unlike in the case of piston generated incompressible vortex rings where the piston velocity variation with time is usually trapezoidal, in the shock-generated vortex ring case the exit fluid velocity doubles from its initial value Ub before it slowly decays to zero. At the end of the ring formation, its translation speed is observed to be about 0.7 Ub. During initial formation and propagation, a jet-like flow exists behind the vortex ring. The vortex ring detachment from the tailing jet, commonly referred to as pinch-off, is briefly discussed.

Numerical Study of Richtmyer-Meshkov Instability with Re-Shock

NASA Astrophysics Data System (ADS)

Wong, Man Long; Livescu, Daniel; Lele, Sanjiva

2017-11-01

The interaction of a Mach 1.45 shock wave with a perturbed planar interface between two gases with an Atwood number 0.68 is studied through 2D and 3D shock-capturing adaptive mesh refinement (AMR) simulations with physical diffusive and viscous terms. The simulations have initial conditions similar to those in the actual experiment conducted by Poggi et al. [1998]. The development of the flow and evolution of mixing due to the interactions with the first shock and the re-shock are studied together with the sensitivity of various global parameters to the properties of the initial perturbation. Grid resolutions needed for fully resolved and 2D and 3D simulations are also evaluated. Simulations are conducted with an in-house AMR solver HAMeRS built on the SAMRAI library. The code utilizes the high-order localized dissipation weighted compact nonlinear scheme [Wong and Lele, 2017] for shock-capturing and different sensors including the wavelet sensor [Wong and Lele, 2016] to identify regions for grid refinement. First and third authors acknowledge the project sponsor LANL.

Initial conditions and modeling for simulations of shock driven turbulent material mixing

DOE PAGES

Grinstein, Fernando F.

2016-11-17

Here, we focus on the simulation of shock-driven material mixing driven by flow instabilities and initial conditions (IC). Beyond complex multi-scale resolution issues of shocks and variable density turbulence, me must address the equally difficult problem of predicting flow transition promoted by energy deposited at the material interfacial layer during the shock interface interactions. Transition involves unsteady large-scale coherent-structure dynamics capturable by a large eddy simulation (LES) strategy, but not by an unsteady Reynolds-Averaged Navier–Stokes (URANS) approach based on developed equilibrium turbulence assumptions and single-point-closure modeling. On the engineering end of computations, such URANS with reduced 1D/2D dimensionality and coarsermore » grids, tend to be preferred for faster turnaround in full-scale configurations.« less

Pressure threshold for shock wave induced renal hemorrhage.

PubMed

Mayer, R; Schenk, E; Child, S; Norton, S; Cox, C; Hartman, C; Cox, C; Carstensen, E

1990-12-01

Studies were performed with an interest in determining a pressure threshold for extracorporeal shock wave induced renal damage. Histological evidence of intraparenchymal hemorrhage was used as an indicator of tissue trauma. Depilated C3H mice were anesthetized and placed on a special frame to enhance visualization and treatment of the kidneys in situ. A Wolf electrohydraulic generator and 9 French probe designed for endoscopic use were utilized to expose the kidneys to 10 double spherically divergent shock waves. Measurements of the shock waves revealed two positive pressure peaks of similar magnitude for each spark discharge. The kidneys were exposed to different peak pressures by choice of distance from the spark source and were removed immediately after treatment for histologic processing. A dose response was noted with severe corticomedullary damage apparent following 15 to 20 MPa shocks. Hemorrhage was more apparent in the medulla where evidence of damage could be seen following pressures as low as three to five MPa. When a latex membrane was interposed to prevent possible collapse of the initial bubble from the spark source against the skin surface, histological evaluation revealed substantial reduction of severe tissue damage associated with the highest pressures tested, 20 MPa. However, the threshold level for evidence of hemorrhage remained about three to five MPa. Hydrophonic measurements indicated that the membrane allowed transmission of the acoustic shock waves and suggested that collapse of the bubble generated by electrohydraulic probes may have local effects due to a cavitation-like mechanism.

Molecular Mechanisms in the shock induced decomposition of FOX-7

NASA Astrophysics Data System (ADS)

Mishra, Ankit; Tiwari, Subodh C.; Nakano, Aiichiro; Vashishta, Priya; Kalia, Rajiv; CACS Team

Experimental and first principle computational studies on FOX 7 have either involved a very small system consisting of a few atoms or they did not take into account the decomposition mechanisms under extreme conditions of temperature and pressure. We have performed a large-scale reactive MD simulation using ReaxFF-lg force field to study the shock decomposition of FOX 7. The chemical composition of the principal decomposition products correlates well with experimental observations. Furthermore, we observed that the production of N2 and H2O was inter molecular in nature and was through different chemical pathways. Moreover, the production of CO and CO2 was delayed due to production of large stable C,O atoms cluster. These critical insights into the initial processes involved in the shock induced decomposition of FOX-7 will greatly help in understanding the factors playing an important role in the insensitiveness of this high energy material. This research is supported by AFOSR Award No. FA9550-16-1-0042.

A surge of light at the birth of a supernova.

PubMed

Bersten, M C; Folatelli, G; García, F; Van Dyk, S D; Benvenuto, O G; Orellana, M; Buso, V; Sánchez, J L; Tanaka, M; Maeda, K; Filippenko, A V; Zheng, W; Brink, T G; Cenko, S B; de Jaeger, T; Kumar, S; Moriya, T J; Nomoto, K; Perley, D A; Shivvers, I; Smith, N

2018-02-21

It is difficult to establish the properties of massive stars that explode as supernovae. The electromagnetic emission during the first minutes to hours after the emergence of the shock from the stellar surface conveys important information about the final evolution and structure of the exploding star. However, the unpredictable nature of supernova events hinders the detection of this brief initial phase. Here we report the serendipitous discovery of a newly born, normal type IIb supernova (SN 2016gkg), which reveals a rapid brightening at optical wavelengths of about 40 magnitudes per day. The very frequent sampling of the observations allowed us to study in detail the outermost structure of the progenitor of the supernova and the physics of the emergence of the shock. We develop hydrodynamical models of the explosion that naturally account for the complete evolution of the supernova over distinct phases regulated by different physical processes. This result suggests that it is appropriate to decouple the treatment of the shock propagation from the unknown mechanism that triggers the explosion.

A surge of light at the birth of a supernova

NASA Astrophysics Data System (ADS)

Bersten, M. C.; Folatelli, G.; García, F.; van Dyk, S. D.; Benvenuto, O. G.; Orellana, M.; Buso, V.; Sánchez, J. L.; Tanaka, M.; Maeda, K.; Filippenko, A. V.; Zheng, W.; Brink, T. G.; Cenko, S. B.; de Jaeger, T.; Kumar, S.; Moriya, T. J.; Nomoto, K.; Perley, D. A.; Shivvers, I.; Smith, N.

2018-02-01

It is difficult to establish the properties of massive stars that explode as supernovae. The electromagnetic emission during the first minutes to hours after the emergence of the shock from the stellar surface conveys important information about the final evolution and structure of the exploding star. However, the unpredictable nature of supernova events hinders the detection of this brief initial phase. Here we report the serendipitous discovery of a newly born, normal type IIb supernova (SN 2016gkg), which reveals a rapid brightening at optical wavelengths of about 40 magnitudes per day. The very frequent sampling of the observations allowed us to study in detail the outermost structure of the progenitor of the supernova and the physics of the emergence of the shock. We develop hydrodynamical models of the explosion that naturally account for the complete evolution of the supernova over distinct phases regulated by different physical processes. This result suggests that it is appropriate to decouple the treatment of the shock propagation from the unknown mechanism that triggers the explosion.

The effect of treatment strategy on stone comminution efficiency in shock wave lithotripsy.

PubMed

Zhou, Yufeng; Cocks, Franklin H; Preminger, Glenn M; Zhong, Pei

2004-07-01

The comminution of kidney stones in shock wave lithotripsy (SWL) is a dose dependent process caused primarily by the combination of 2 fundamental mechanisms, namely stress waves and cavitation. The effect of treatment strategy with emphasis on enhancing the effect of stress waves or cavitation on stone comminution in SWL was investigated. Because vascular injury in SWL is also dose dependent, optimization of the treatment strategy may produce improved stone comminution with decreased tissue injury in SWL. Using an in vitro experiment system that mimics stone fragmentation in the renal pelvis spherical BegoStone (Bego USA, Smithfield, Rhode Island) phantoms (diameter 10 mm) were exposed to 1,500 shocks at a pulse repetition rate of 1 Hz in an unmodified HM-3 lithotripter (Dornier Medical Systems, Kennesaw, Georgia). The 3 treatment strategies used were increasing output voltage from 18 to 20 and then to 22 kV every 500 shocks with emphasis on enhancing the effect of cavitation on medium fragments (2 to 4 mm) at the final treatment stage, decreasing output voltage from 22 to 20 and then to 18 kV every 500 shocks with emphasis on enhancing the effect of stress waves on large fragments (greater than 4 mm) at the initial treatment stage and maintaining a constant output voltage at 20 kV, as typically used in SWL procedures. Following shock wave exposure the size distribution of fragments was determined by the sequential sieving method. In addition, pressure waveforms at lithotripter focus (F2) produced at different output settings were measured using a fiber optic probe hydrophone. The rate of stone comminution in SWL varied significantly in a dose dependent manner depending on the treatment strategies used. Specifically the comminution efficiencies produced by the 3 strategies after the initial 500 shocks were 30.7%, 59% and 41.9%, respectively. After 1,000 shocks the corresponding comminution efficiencies became similar (60.2%, 68.1% and 66.4%, respectively) with no statistically significant differences (p = 0.08). After 1,500 shocks the final comminution efficiency produced by the first strategy was 88.7%, which was better than the corresponding values of 81.2% and 83.5%, respectively, for the other 2 strategies. The difference between the final comminution efficiency of the first and second strategies was statistically significant (p = 0.005). Progressive increase in lithotripter output voltage can produce the best overall stone comminution in vitro.

Numerical study of multiscale compaction-initiated detonation

NASA Astrophysics Data System (ADS)

Gambino, J. R.; Schwendeman, D. W.; Kapila, A. K.

2018-02-01

A multiscale model of heterogeneous condensed-phase explosives is examined computationally to determine the course of transient events following the application of a piston-driven stimulus. The model is a modified version of that introduced by Gonthier (Combust Sci Technol 175(9):1679-1709, 2003. https://doi.org/10.1080/00102200302373) in which the explosive is treated as a porous, compacting medium at the macro-scale and a collection of closely packed spherical grains capable of undergoing reaction and diffusive heat transfer at the meso-scale. A separate continuum description is ascribed to each scale, and the two scales are coupled together in an energetically consistent manner. Following piston-induced compaction, localized energy deposition at the sites of intergranular contact creates hot spots where reaction begins preferentially. Reaction progress at the macro-scale is determined by the spatial average of that at the grain scale. A parametric study shows that combustion at the macro-scale produces an unsteady detonation with a cyclical character, in which the lead shock loses strength and is overtaken by a stronger secondary shock generated in the partially reacted material behind it. The secondary shock in turn becomes the new lead shock and the process repeats itself.

The Autodigestion Hypothesis for Shock and Multi-organ Failure

PubMed Central

Schmid-Schönbein, Geert W.; Chang, Marisol

2013-01-01

An important medical problem with high mortality is shock, sepsis and multi-organ failure. They have currently no treatments other than alleviation of symptoms. Shock is accompanied by strong markers for inflammation and involves a cascade of events that leads to failure in organs even if they are not involved in the initial insult. Recent evidence indicates that pancreatic digestive enzymes carried in the small intestine after mixing with ingested food are a major cause for multi-organ failure. These concentrated and relatively non-specific enzymes are usually compartmentalized inside the intestinal lumen as requirement for normal digestion. But after breakdown of the mucosal barrier they leak into the wall of the intestine and start an autodigestion process that includes destruction of villi in the intestine. Digestive enzymes also generate cytotoxic mediators, which together are transported into the systemic circulation via the portal venous system, the intestinal lymphatics and via the peritoneum. They cause various degrees of cell and organ dysfunction that can reach the point of complete organ failure. Blockade of digestive enzymes in the lumen of the intestine in experimental forms of shock serves to reduce breakdown of the mucosal barrier and autodigestion of the intestine, organ dysfunctions and mortality. PMID:23989761

DOE Office of Scientific and Technical Information (OSTI.GOV)

James A. Smith; Jeffrey M. Lacy; Barry H. Rabin

12. Other advances in QNDE and related topics: Preferred Session Laser-ultrasonics Developing A Laser Shockwave Model For Characterizing Diffusion Bonded Interfaces 41st Annual Review of Progress in Quantitative Nondestructive Evaluation Conference QNDE Conference July 20-25, 2014 Boise Centre 850 West Front Street Boise, Idaho 83702 James A. Smith, Jeffrey M. Lacy, Barry H. Rabin, Idaho National Laboratory, Idaho Falls, ID ABSTRACT: The US National Nuclear Security Agency has a Global Threat Reduction Initiative (GTRI) which is assigned with reducing the worldwide use of high-enriched uranium (HEU). A salient component of that initiative is the conversion of research reactors from HEUmore » to low enriched uranium (LEU) fuels. An innovative fuel is being developed to replace HEU. The new LEU fuel is based on a monolithic fuel made from a U-Mo alloy foil encapsulated in Al-6061 cladding. In order to complete the fuel qualification process, the laser shock technique is being developed to characterize the clad-clad and fuel-clad interface strengths in fresh and irradiated fuel plates. The Laser Shockwave Technique (LST) is being investigated to characterize interface strength in fuel plates. LST is a non-contact method that uses lasers for the generation and detection of large amplitude acoustic waves to characterize interfaces in nuclear fuel plates. However the deposition of laser energy into the containment layer on specimen’s surface is intractably complex. The shock wave energy is inferred from the velocity on the backside and the depth of the impression left on the surface from the high pressure plasma pulse created by the shock laser. To help quantify the stresses and strengths at the interface, a finite element model is being developed and validated by comparing numerical and experimental results for back face velocities and front face depressions with experimental results. This paper will report on initial efforts to develop a finite element model for laser shock.« less

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

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

2009-07-01

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

The preplasma effect on the properties of the shock wave driven by a fast electron beam

DOE Office of Scientific and Technical Information (OSTI.GOV)

Llor Aisa, E.; Ribeyre, X.; Tikhonchuk, V. T.

2016-08-15

Strong shock wave generation by a mono-energetic fast electron beam in a plasma with an increasing density profile is studied theoretically. The proposed analytical model describes the shock wave characteristics for a homogeneous plasma preceded by a low density precursor. The shock pressure and the time of shock formation depend on the ratio of the electron stopping length to the preplasma areal density and on the initial energy of injected electrons. The conclusions of theoretical model are confirmed in numerical simulations.

Transcriptomic analysis of (group I) Clostridium botulinum ATCC 3502 cold shock response.

PubMed

Dahlsten, Elias; Isokallio, Marita; Somervuo, Panu; Lindström, Miia; Korkeala, Hannu

2014-01-01

Profound understanding of the mechanisms foodborne pathogenic bacteria utilize in adaptation to the environmental stress they encounter during food processing and storage is of paramount importance in design of control measures. Chill temperature is a central control measure applied in minimally processed foods; however, data on the mechanisms the foodborne pathogen Clostridium botulinum activates upon cold stress are scarce. Transcriptomic analysis on the C. botulinum ATCC 3502 strain upon temperature downshift from 37°C to 15°C was performed to identify the cold-responsive gene set of this organism. Significant up- or down-regulation of 16 and 11 genes, respectively, was observed 1 h after the cold shock. At 5 h after the temperature downshift, 199 and 210 genes were up- or down-regulated, respectively. Thus, the relatively small gene set affected initially indicated a targeted acute response to cold shock, whereas extensive metabolic remodeling appeared to take place after prolonged exposure to cold. Genes related to fatty acid biosynthesis, oxidative stress response, and iron uptake and storage were induced, in addition to mechanisms previously characterized as cold-tolerance related in bacteria. Furthermore, several uncharacterized DNA-binding transcriptional regulator-encoding genes were induced, suggesting involvement of novel regulatory mechanisms in the cold shock response of C. botulinum. The role of such regulators, CBO0477 and CBO0558A, in cold tolerance of C. botulinum ATCC 3502 was demonstrated by deteriorated growth of related mutants at 17°C.

Implementation of an Inpatient Pediatric Sepsis Identification Pathway.

PubMed

Bradshaw, Chanda; Goodman, Ilyssa; Rosenberg, Rebecca; Bandera, Christopher; Fierman, Arthur; Rudy, Bret

2016-03-01

Early identification and treatment of severe sepsis and septic shock improves outcomes. We sought to identify and evaluate children with possible sepsis on a pediatric medical/surgical unit through successful implementation of a sepsis identification pathway. The sepsis identification pathway, a vital sign screen and subsequent physician evaluation, was implemented in October 2013. Quality improvement interventions were used to improve physician and nursing adherence with the pathway. We reviewed charts of patients with positive screens on a monthly basis to assess for nursing recognition/physician notification, physician evaluation for sepsis, and subsequent physician diagnosis of sepsis and severe sepsis/septic shock. Adherence data were analyzed on a run chart and statistical process control p-chart. Nursing and physician pathway adherence of >80% was achieved over a 6-month period and sustained for the following 6 months. The direction of improvements met standard criteria for special causes. Over a 1-year period, there were 963 admissions to the unit. Positive screens occurred in 161 (16.7%) of these admissions and 38 (23.5%) of these had a physician diagnosis of sepsis, severe sepsis, or septic shock. One patient with neutropenia and septic shock had a negative sepsis screen due to lack of initial fever. Using quality improvement methodology, we successfully implemented a sepsis identification pathway on our pediatric unit. The pathway provided a standardized process to identify and evaluate children with possible sepsis requiring timely evaluation and treatment. Copyright © 2016 by the American Academy of Pediatrics.

Skill acquisition and retention in automated external defibrillator (AED) use and CPR by lay responders: a prospective study.

PubMed

Woollard, Malcolm; Whitfeild, Richard; Smith, Anna; Colquhoun, Michael; Newcombe, Robert G; Vetteer, Norman; Chamberlain, Douglas

2004-01-01

This prospective study evaluated the acquisition and retention of skills in cardio-pulmonary resuscitation (CPR) and the use of the automated external defibrillator (AED) by lay volunteers involved in the Department of Health, England National Defibrillator Programme. One hundred and twelve trainees were tested immediately before and after and initial 4-h class; 76 were similarly reassessed at refresher training 6 months later. A standardised test scenario that required assessment of the casualty, CPR and the use of on AED was evaluated using recording manikin data and video recordings. Before training only 44% of subjects delivered a shock. Afterwards, all did so and the average delay to first shock was reduced by 57 s. All trainees placed the defibrillator electrodes in an "acceptable" position after training, but very few did so in the recommended "ideal" position. After refresher training 80% of subjects used the correct sequence for CPR and shock delivery, yet a third failed to perform adequate safety checks before all shocks. The trainees self-assessed AED competence score was 86 (scale 0-100) after the initial class and their confidence that they would act in a real emergency was rated at a similar level. Initial training improved performance of all CPR skills, although all except compression rate had deteriorated after 6 months. The proportion of subjects able to correctly perform most CPR skill was higher following refresher training that after the initial class. Although this course was judged to be effective in teaching delivery of counter-shocks, the need was identified for more emphasis on positioning of electrodes, pre-shock safety checks, airway opening, ventilation volume, checking for signs of a circulation, hand positioning, and depth and rate of chest compressions.

Acute right heart failure after hemorrhagic shock and trauma pneumonectomy-a management approach: A blinded randomized controlled animal trial using inhaled nitric oxide.

PubMed

Lubitz, Andrea L; Sjoholm, Lars O; Goldberg, Amy; Pathak, Abhijit; Santora, Thomas; Sharp, Thomas E; Wallner, Markus; Berretta, Remus M; Poole, Lauren A; Wu, Jichuan; Wolfson, Marla R

2017-02-01

Hemorrhagic shock and pneumonectomy causes an acute increase in pulmonary vascular resistance (PVR). The increase in PVR and right ventricular (RV) afterload leads to acute RV failure, thus reducing left ventricular (LV) preload and output. Inhaled nitric oxide (iNO) lowers PVR by relaxing pulmonary arterial smooth muscle without remarkable systemic vascular effects. We hypothesized that with hemorrhagic shock and pneumonectomy, iNO can be used to decrease PVR and mitigate right heart failure. A hemorrhagic shock and pneumonectomy model was developed using sheep. Sheep received lung protective ventilatory support and were instrumented to serially obtain measurements of hemodynamics, gas exchange, and blood chemistry. Heart function was assessed with echocardiography. After randomization to study gas of iNO 20 ppm (n = 9) or nitrogen as placebo (n = 9), baseline measurements were obtained. Hemorrhagic shock was initiated by exsanguination to a target of 50% of the baseline mean arterial pressure. The resuscitation phase was initiated, consisting of simultaneous left pulmonary hilum ligation, via median sternotomy, infusion of autologous blood and initiation of study gas. Animals were monitored for 4 hours. All animals had an initial increase in PVR. PVR remained elevated with placebo; with iNO, PVR decreased to baseline. Echo showed improved RV function in the iNO group while it remained impaired in the placebo group. After an initial increase in shunt and lactate and decrease in SvO2, all returned toward baseline in the iNO group but remained abnormal in the placebo group. These data indicate that by decreasing PVR, iNO decreased RV afterload, preserved RV and LV function, and tissue oxygenation in this hemorrhagic shock and pneumonectomy model. This suggests that iNO may be a useful clinical adjunct to mitigate right heart failure and improve survival when trauma pneumonectomy is required.

Shock-induced CO2 loss from CaCO3: Implications for early planetary atmospheres

NASA Technical Reports Server (NTRS)

Lange, M. A.; Ahrens, T. J.

1984-01-01

Recovered samples from shock recovery experiments on single crystal calcite were subjected to thermogravimetric analysis to determine the amount of post-shock CO2, the decarbonization interval and the activation energy, for the removal of remaining CO2 in shock-loaded calcite. Comparison of post-shock CO2 with that initially present determines shock-induced CO2 loss as a function of shock pressure. Incipient to complete CO2 loss occurs over a pressure range of approximately 10 to approximately 70 GPa. Optical and scanning electron microscopy reveal structural changes, which are related to the shock-loading. The occurrence of dark, diffuse areas, which can be resolved as highly vesicular areas as observed with a scanning electron microscope are interpreted as representing quenched partial melts, into which shock-released CO2 was injected. The experimental results are used to constrain models of shock-produced, primary CO2 atmospheres on the accreting terrestrial planets.

Collisionless Weibel shocks: Full formation mechanism and timing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bret, A.; Instituto de Investigaciones Energéticas y Aplicaciones Industriales, Campus Universitario de Ciudad Real, 13071 Ciudad Real; Stockem, A.

2014-07-15

Collisionless shocks in plasmas play an important role in space physics (Earth's bow shock) and astrophysics (supernova remnants, relativistic jets, gamma-ray bursts, high energy cosmic rays). While the formation of a fluid shock through the steepening of a large amplitude sound wave has been understood for long, there is currently no detailed picture of the mechanism responsible for the formation of a collisionless shock. We unravel the physical mechanism at work and show that an electromagnetic Weibel shock always forms when two relativistic collisionless, initially unmagnetized, plasma shells encounter. The predicted shock formation time is in good agreement with 2Dmore » and 3D particle-in-cell simulations of counterstreaming pair plasmas. By predicting the shock formation time, experimental setups aiming at producing such shocks can be optimised to favourable conditions.« less

Multi-dimensional mesoscale simulations of detonation initiation in energetic materials with density-based kinetics

NASA Astrophysics Data System (ADS)

Jackson, Thomas Luther; Jost, Antoine M. D.; Zhang, Ju; Sridharan, Prashanth; Amadio, Guilherme

2018-03-01

In this work we present multi-dimensional mesoscale simulations of detonation initiation in energetic materials. We solve the reactive Euler equations, with the energy equation augmented by a power deposition term. The reaction rate at the mesoscale is modelled using density-based kinetics, while the deposition term is based on simulations of void collapse at the microscale, modelled at the mesoscale as hot spots. We carry out two- and three-dimensional mesoscale simulations of random packs of HMX crystals in a binder, and show that transition between no-detonation and detonation depends on the number density of the hot spots, the packing fraction, and the post-shock pressure of an imposed shock. In particular, we show that, for a fixed post-shock pressure, there exists a critical value of the number density of hot spots, such that when the number density is below this value a detonation wave will not develop. We highlight the importance of morphology to initiation by comparing with a homogeneous counterpart, and we compare relevant length scales by examining their corresponding power spectra. We also examine the effect of packing fraction and show that at low post-shock pressures there is significant variation in the initiation times, but that this variation disappears as the post-shock pressure is increased. Finally, we compare three-dimensional simulations with the experimental data, and show that the model is capable of qualitatively reproducing the trends shown in the data.

Effect of prior heat shock on heat resistance of Listeria monocytogenes in meat.

PubMed Central

Farber, J M; Brown, B E

1990-01-01

The effect of prior heat shock on the thermal resistance of Listeria monocytogenes in meat was investigated. A sausage mix inoculated with approximately 10(7) L. monocytogenes per g was initially subjected to a heat shock temperature of 48 degrees C before being heated at a final test temperature of 62 or 64 degrees C. Although cells heat shocked at 48 degrees C for 30 or 60 min did not show a significant increase in thermotolerance as compared with control cells (non-heat shocked), bacteria heat shocked for 120 min did, showing an average 2.4-fold increase in the D64 degrees C value. Heat-shocked cells shifted to 4 degrees C appeared to maintain their thermotolerance for at least 24 h after heat shock. PMID:2116757

High-Mach number, laser-driven magnetized collisionless shocks

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schaeffer, Derek B.; Fox, W.; Haberberger, D.

Collisionless shocks are ubiquitous in space and astrophysical systems, and the class of supercritical shocks is of particular importance due to their role in accelerating particles to high energies. While these shocks have been traditionally studied by spacecraft and remote sensing observations, laboratory experiments can provide reproducible and multi-dimensional datasets that provide complementary understanding of the underlying microphysics. We present experiments undertaken on the OMEGA and OMEGA EP laser facilities that show the formation and evolution of high-Mach number collisionless shocks created through the interaction of a laser-driven magnetic piston and magnetized ambient plasma. Through time-resolved, 2-D imaging we observemore » large density and magnetic compressions that propagate at super-Alfvenic speeds and that occur over ion kinetic length scales. Electron density and temperature of the initial ambient plasma are characterized using optical Thomson scattering. Measurements of the piston laser-plasma are modeled with 2-D radiation-hydrodynamic simulations, which are used to initialize 2-D particle-in-cell simulations of the interaction between the piston and ambient plasmas. The numerical results show the formation of collisionless shocks, including the separate dynamics of the carbon and hydrogen ions that constitute the ambient plasma and their effect on the shock structure. Furthermore, the simulations also show the shock separating from the piston, which we observe in the data at late experimental times.« less

High-Mach number, laser-driven magnetized collisionless shocks

DOE PAGES

Schaeffer, Derek B.; Fox, W.; Haberberger, D.; ...

2017-12-08

Collisionless shocks are ubiquitous in space and astrophysical systems, and the class of supercritical shocks is of particular importance due to their role in accelerating particles to high energies. While these shocks have been traditionally studied by spacecraft and remote sensing observations, laboratory experiments can provide reproducible and multi-dimensional datasets that provide complementary understanding of the underlying microphysics. We present experiments undertaken on the OMEGA and OMEGA EP laser facilities that show the formation and evolution of high-Mach number collisionless shocks created through the interaction of a laser-driven magnetic piston and magnetized ambient plasma. Through time-resolved, 2-D imaging we observemore » large density and magnetic compressions that propagate at super-Alfvenic speeds and that occur over ion kinetic length scales. Electron density and temperature of the initial ambient plasma are characterized using optical Thomson scattering. Measurements of the piston laser-plasma are modeled with 2-D radiation-hydrodynamic simulations, which are used to initialize 2-D particle-in-cell simulations of the interaction between the piston and ambient plasmas. The numerical results show the formation of collisionless shocks, including the separate dynamics of the carbon and hydrogen ions that constitute the ambient plasma and their effect on the shock structure. Furthermore, the simulations also show the shock separating from the piston, which we observe in the data at late experimental times.« less

High-Mach number, laser-driven magnetized collisionless shocks

NASA Astrophysics Data System (ADS)

Schaeffer, D. B.; Fox, W.; Haberberger, D.; Fiksel, G.; Bhattacharjee, A.; Barnak, D. H.; Hu, S. X.; Germaschewski, K.; Follett, R. K.

2017-12-01

Collisionless shocks are ubiquitous in space and astrophysical systems, and the class of supercritical shocks is of particular importance due to their role in accelerating particles to high energies. While these shocks have been traditionally studied by spacecraft and remote sensing observations, laboratory experiments can provide reproducible and multi-dimensional datasets that provide a complementary understanding of the underlying microphysics. We present experiments undertaken on the OMEGA and OMEGA EP laser facilities that show the formation and evolution of high-Mach number collisionless shocks created through the interaction of a laser-driven magnetic piston and a magnetized ambient plasma. Through time-resolved, 2-D imaging, we observe large density and magnetic compressions that propagate at super-Alfvénic speeds and that occur over ion kinetic length scales. The electron density and temperature of the initial ambient plasma are characterized using optical Thomson scattering. Measurements of the piston laser-plasma are modeled with 2-D radiation-hydrodynamic simulations, which are used to initialize 2-D particle-in-cell simulations of the interaction between the piston and ambient plasmas. The numerical results show the formation of collisionless shocks, including the separate dynamics of the carbon and hydrogen ions that constitute the ambient plasma and their effect on the shock structure. The simulations also show the shock separating from the piston, which we observe in the data at late experimental times.

Limits of shock wave ignition of hydrogen-oxygen mixture in the presence of particles

NASA Astrophysics Data System (ADS)

Efremov, V. P.; Obruchkova, L. R.; Ivanov, M. F.; Kiverin, A. D.

2018-01-01

It is a well known fact that the cloud of non-reacting particles in the flow weakens or even suppresses the detonation. Contrary to this phenomenon there are experimental data showing that the presence of solid particles in the combustible mixtures shorten significantly the ignition delay time. In other words particles could promote the initiation of detonation. This paper analyzes numerically the phenomenon of detonation initiation behind the shock wave in the combustible mixture containing only one solid particle. Numerical results demonstrate a significant degree of lowering of ignition limits. Namely, it is shown that it becomes possible to ignite the gaseous mixture much earlier due to the shock wave interaction with solid particle surface. It is found that ignition arises in subsonic region located between the particle and the bow shock front.

Selfsimilar time dependent shock structures

NASA Astrophysics Data System (ADS)

Beck, R.; Drury, L. O.

1985-08-01

Diffusive shock acceleration as an astrophysical mechanism for accelerating charged particles has the advantage of being highly efficient. This means however that the theory is of necessity nonlinear; the reaction of the accelerated particles on the shock structure and the acceleration process must be self-consistently included in any attempt to develop a complete theory of diffusive shock acceleration. Considerable effort has been invested in attempting, at least partially, to do this and it has become clear that in general either the maximum particle energy must be restricted by introducing additional loss processes into the problem or the acceleration must be treated as a time dependent problem (Drury, 1984). It is concluded that stationary modified shock structures can only exist for strong shocks if additional loss processes limit the maximum energy a particle can attain. This is certainly possible and if it occurs the energy loss from the shock will lead to much greater shock compressions. It is however equally possible that no such processes exist and we must then ask what sort of nonstationary shock structure develops. The ame argument which excludes stationary structures also rules out periodic solutions and indeed any solution where the width of the shock remains bounded. It follows that the width of the shock must increase secularly with time and it is natural to examine the possibility of selfsimilar time dependent solutions.

Selfsimilar time dependent shock structures

NASA Technical Reports Server (NTRS)

Beck, R.; Drury, L. O.

1985-01-01

Diffusive shock acceleration as an astrophysical mechanism for accelerating charged particles has the advantage of being highly efficient. This means however that the theory is of necessity nonlinear; the reaction of the accelerated particles on the shock structure and the acceleration process must be self-consistently included in any attempt to develop a complete theory of diffusive shock acceleration. Considerable effort has been invested in attempting, at least partially, to do this and it has become clear that in general either the maximum particle energy must be restricted by introducing additional loss processes into the problem or the acceleration must be treated as a time dependent problem (Drury, 1984). It is concluded that stationary modified shock structures can only exist for strong shocks if additional loss processes limit the maximum energy a particle can attain. This is certainly possible and if it occurs the energy loss from the shock will lead to much greater shock compressions. It is however equally possible that no such processes exist and we must then ask what sort of nonstationary shock structure develops. The ame argument which excludes stationary structures also rules out periodic solutions and indeed any solution where the width of the shock remains bounded. It follows that the width of the shock must increase secularly with time and it is natural to examine the possibility of selfsimilar time dependent solutions.

Shockwave compression of Ar gas at several initial densities

NASA Astrophysics Data System (ADS)

Dattelbaum, Dana M.; Goodwin, Peter M.; Garcia, Daniel B.; Gustavsen, Richard L.; Lang, John M.; Aslam, Tariq D.; Sheffield, Stephen A.; Gibson, Lloyd L.; Morris, John S.

2017-01-01

Experimental data of the principal Hugoniot locus of variable density gas-phase noble and molecular gases are rare. The majority of shock Hugoniot data is either from shock tube experiments on low-pressure gases or from plate impact experiments on cryogenic, liquefied gases. In both cases, physics regarding shock compressibility, thresholds for the on-set of shock-driven ionization, and even dissociation chemistry are difficult to infer for gases at intermediate densities. We have developed an experimental target design for gas gun-driven plate impact experiments on noble gases at initial pressures between 200-1000 psi. Using optical velocimetry, we are able to directly determine both the shock and particle velocities of the gas on the principal Hugoniot locus, as well as clearly differentiate ionization thresholds. The target design also results in multiply shocking the gas in a quasi-isentropic fashion yielding off-Hugoniot compression data. We describe the results of a series of plate impact experiments on Ar with starting densities between 0.02-0.05 g/cm3 at room temperature. Furthermore, by coupling optical fibers to the targets, we have measured the time-resolved optical emission from the shocked gas using a spectrometer coupled to an optical streak camera to spectrally-resolve the emission, and with a 5-color optical pyrometer for temperature determination.

Shock vaporization of carbonate and sulfate minerals

NASA Astrophysics Data System (ADS)

Shen, A. H.; Ahrens, T. J.; O'Keefe, J. D.

2001-12-01

Strong shock waves induced by impacts can cause vaporization of rocks and minerals. The products of such process play important roles in planetary differentiation (Yakovlev et al., Geochem. International, 38, 1027, 2000) and in effecting the planetary climate. Many experiments and computer simulations have been performed to simulate the Chicxulub impact at Cretaceous/Tertiary boundary (see, for example, Pierazzo et al., J. Geophys. Res., 103, 28607, 1998 and Pope et al., J. Geophys. Res., 102, 21645, 1997). However, the pressure range for incipient and complete vaporization of carbonates and sulfates are not well constrained, especially, for minerals with various initial porosities. Furthermore, evidence for chemical species in the products of vaporized carbonate and sulfate minerals is almost non-existing. In this study, we employed published Hugoniot data for carbonate and sulfate minerals. By using the methods described in Ahrens (J. Appl. Phys., 43, 2443, 1972) and Ahrens and O'Keefe (The Moon, 4, 214, 1972), we calculated the entropy associated with the thermodynamic states produced by hypervelocity impacts at various velocities for carbonate and sulfate minerals with different initial porosities. The results were compared with the entropy of incipient vaporization and complete vaporization of these minerals to determine the degree of vaporization due to impacts. Moreover, these results are utilized to guide our experimental study in speciation reactions in shock-induced vaporization of carbonates and sulfates.

Macro-mechanical modeling of blast-wave mitigation in foams. Part II: reliability of pressure measurements

NASA Astrophysics Data System (ADS)

Britan, A.; Liverts, M.; Shapiro, H.; Ben-Dor, G.

2013-02-01

A phenomenological study of the process occurring when a plane shock wave reflected off an aqueous foam column filling the test section of a vertical shock tube has been undertaken. The experiments were conducted with initial shock wave Mach numbers in the range 1.25le {M}_s le 1.7 and foam column heights in the range 100-450 mm. Miniature piezotrone circuit electronic pressure transducers were used to record the pressure histories upstream and alongside the foam column. The aim of these experiments was to find a simple way to eliminate a spatial averaging as an artifact of the pressure history recorded by the side-on transducer. For this purpose, we discuss first the common behaviors of the pressure traces in extended time scales. These observations evidently quantify the low frequency variations of the pressure field within the different flow domains of the shock tube. Thereafter, we focus on the fronts of the pressure signals, which, in turn, characterize the high-frequency response of the foam column to the shock wave impact. Since the front shape and the amplitude of the pressure signal most likely play a significant role in the foam destruction, phase changes and/or other physical factors, such as high capacity, viscosity, etc., the common practice of the data processing is revised and discussed in detail. Generally, side-on pressure measurements must be used with great caution when performed in wet aqueous foams, because the low sound speed is especially prone to this effect. Since the spatial averaged recorded pressure signals do not reproduce well the real behaviors of the pressure rise, the recorded shape of the shock wave front in the foam appears much thicker. It is also found that when a thin liquid film wet the sensing membrane, the transducer sensitivity was changed. As a result, the pressure recorded in the foam could exceed the real amplitude of the post-shock wave flow. A simple procedure, which allows correcting this imperfection, is discussed in detail.

Association of Fluid Resuscitation Initiation Within 30 Minutes of Severe Sepsis and Septic Shock Recognition With Reduced Mortality and Length of Stay.

PubMed

Leisman, Daniel; Wie, Benjamin; Doerfler, Martin; Bianculli, Andrea; Ward, Mary Frances; Akerman, Meredith; D'Angelo, John K; Zemmel D'Amore, Jason A

2016-09-01

We evaluate the association of intravenous fluid resuscitation initiation within 30 minutes of severe sepsis or septic shock identification in the emergency department (ED) with inhospital mortality and hospital length of stay. We also compare intravenous fluid resuscitation initiated at various times from severe sepsis or septic shock identification's association with the same outcomes. This was a review of a prospective, observational cohort of all ED severe sepsis or septic shock patients during 13 months, captured in a performance improvement database at a single, urban, tertiary care facility (90,000 ED visits/year). The primary exposure was initiation of a crystalloid bolus at 30 mL/kg within 30 minutes of severe sepsis or septic shock identification. Secondary analysis compared intravenous fluid initiated within 30, 31 to 60, or 61 to 180 minutes, or when intravenous fluid resuscitation was initiated at greater than 180 minutes or not provided. Of 1,866 subjects, 53.6% were men, 72.5% were white, mean age was 72 years (SD 16.6 years), and mean initial lactate level was 2.8 mmol/L. Eighty-six percent of subjects were administered intravenous antibiotics within 180 minutes; 1,193 (64%) had intravenous fluid initiated within 30 minutes. Mortality was lower in the within 30 minutes group (159 [13.3%] versus 123 [18.3%]; 95% confidence interval [CI] 1.4% to 8.5%), as was median hospital length of stay (6 days [95% CI 6 to 7] versus 7 days [95% CI 7 to 8]). In multivariate regression that included adjustment for age, lactate, hypotension, acute organ dysfunction, and Emergency Severity Index score, intravenous fluid within 30 minutes was associated with lower mortality (odds ratio 0.63; 95% CI 0.46 to 0.86) and 12% shorter length of stay (hazard ratio=1.14; 95% CI 1.02 to 1.27). In secondary analysis, mortality increased with later intravenous fluid resuscitation initiation: 13.3% (≤30 minutes) versus 16.0% (31 to 60 minutes) versus 16.9% (61 to 180 minutes) versus 19.7% (>180 minutes). Median hospital length of stay also increased with later intravenous fluid initiation: 6 days (95% CI 6 to 7 days) versus 7 days (95% CI 6 to 7 days) versus 7 days (95% CI 6 to 8 days) versus 8 days (95% CI 7 to 9 days). The time of intravenous fluid resuscitation initiation was associated with improved mortality and could be used as an easier obtained alternative to intravenous fluid completion time as a performance indicator in severe sepsis and septic shock management. Copyright © 2016 American College of Emergency Physicians. Published by Elsevier Inc. All rights reserved.

Evolution and stability of shock waves in dissipative gases characterized by activated inelastic collisions.

PubMed

Sirmas, N; Radulescu, M I

2015-02-01

Previous experiments have revealed that shock waves driven through dissipative gases may become unstable, for example, in granular gases and in molecular gases undergoing strong relaxation effects. The mechanisms controlling these instabilities are not well understood. We successfully isolated and investigated this instability in the canonical problem of piston-driven shock waves propagating into a medium characterized by inelastic collision processes. We treat the standard model of granular gases, where particle collisions are taken as inelastic, with a constant coefficient of restitution. The inelasticity is activated for sufficiently strong collisions. Molecular dynamic simulations were performed for 30,000 particles. We find that all shock waves investigated become unstable, with density nonuniformities forming in the relaxation region. The wavelength of these fingers is found to be comparable to the characteristic relaxation thickness. Shock Hugoniot curves for both elastic and inelastic collisions were obtained analytically and numerically. Analysis of these curves indicates that the instability is not of the Bethe-Zeldovich-Thompson or D'yakov-Kontorovich type. Analysis of the shock relaxation rates and rates for clustering in a convected fluid element with the same thermodynamic history ruled out the clustering instability of a homogeneous granular gas. Instead, wave reconstruction of the early transient evolution indicates that the onset of instability occurs during repressurization of the gas following the initial relaxation of the medium behind the lead shock. This repressurization gives rise to internal pressure waves in the presence of strong density gradients. This indicates that the mechanism of instability is more likely of the vorticity-generating Richtmyer-Meshkov type, relying on the action of the inner pressure wave development during the transient relaxation.

Acceleration of Ions and Electrons by Coronal Shocks

NASA Astrophysics Data System (ADS)

Sandroos, A.

2013-12-01

Diffusive shock acceleration (DSA) of particles at collisionless shock waves driven by coronal mass ejections (CMEs) is the best developed theory for the genesis of gradual solar energetic particle (SEP) events. According to DSA, particles scatter from fluctuations present in the ambient magnetic field, which causes some particles to encounter the shock front repeatedly and to gain energy during each crossing. DSA operating in solar corona is a complex process whose outcome depends on multiple parameters such as shock speed and strength, magnetic geometry, and composition of seed particles. Currently, STEREO and other near-Earth spacecraft are providing valuable multi-point information on how SEP properties, such as composition and energy spectra, vary in longitude. Initial results have shown that longitude distributions of large CME-associated SEP events are much wider than previously thought. These findings have many important consequences on SEP modeling. For example, it is important to extend the present models into two or three spatial coordinates to properly account for the effects of coronal and interplanetary magnetic geometry and the evolution of the CME-driven shock wave on the acceleration and transport of SEPs. We present a new model for the shock acceleration of ions and electrons in the solar corona and discuss implications for particle properties (energy spectra, longitudinal distribution, composition) in the resulting gradual SEP events. We also discuss the possible emission of type II radio waves by the accelerated coronal electrons. In the new model, the ion pitch angle scattering rate is calculated from modeled Alfvén wave power spectra using quasilinear theory. The energy gained by ions in scatterings are self-consistently removed from waves so that total energy (ions+waves) is conserved. New model has been implemented on massively parallel simulation platform Corsair.

Photographic laboratory studies of explosions.

NASA Technical Reports Server (NTRS)

Kamel, M. M.; Oppenheim, A. K.

1973-01-01

Description of a series of cinematographic studies of explosions made with a high-speed rotating-mirror streak camera which uses a high-frequency stroboscopic ruby laser as the light source. The results obtained mainly concern explosions initiated by focused laser irradiation from a pulsed neodymium laser in a detonating gas consisting essentially of an equimolar mixture of acetylene and oxygen at an initial pressure of 100 torr at room temperature. Among the most significant observations were observations of a spherical blast wave preceded by a Chapman-Jouguet detonation which is stabilized immediately after initiation, the merging of a spherical flame with a shock front of the blast wave in which the flame is propagating, the division of a spherical detonation front into a shock wave and flame, and the generation of shock waves by a network of spherical flames.

Numerical computation of Pop plot

DOE Office of Scientific and Technical Information (OSTI.GOV)

Menikoff, Ralph

The Pop plot — distance-of-run to detonation versus initial shock pressure — is a key characterization of shock initiation in a heterogeneous explosive. Reactive burn models for high explosives (HE) must reproduce the experimental Pop plot to have any chance of accurately predicting shock initiation phenomena. This report describes a methodology for automating the computation of a Pop plot for a specific explosive with a given HE model. Illustrative examples of the computation are shown for PBX 9502 with three burn models (SURF, WSD and Forest Fire) utilizing the xRage code, which is the Eulerian ASC hydrocode at LANL. Comparisonmore » of the numerical and experimental Pop plot can be the basis for a validation test or as an aid in calibrating the burn rate of an HE model. Issues with calibration are discussed.« less

A survey of critical care nurses' practices and perceptions surrounding early intravenous antibiotic initiation during septic shock.

PubMed

Roberts, Russel J; Alhammad, Abdullah M; Crossley, Lindsay; Anketell, Eric; Wood, LeeAnn; Schumaker, Greg; Garpestad, Erik; Devlin, John W

2017-08-01

Delays in antibiotic administration after severe sepsis recognition increases mortality. While physician and pharmacy-related barriers to early antibiotic initiation have been well evaluated, those factors that affect the speed by which critical care nurses working in either the emergency department or the intensive care unit setting initiate antibiotic therapy remains poorly characterized. To evaluate the knowledge, practices and perceptions of critical care nurses regarding antibiotic initiation in patients with newly recognised septic shock. A validated survey was distributed to 122 critical care nurses at one 320-bed academic institution with a sepsis protocol advocating intravenous(IV) antibiotic initiation within 1hour of shock recognition. Among 100 (82%) critical care nurses responding, nearly all (98%) knew of the existence of the sepsis protocol. However, many critical care nurses stated they would optimise blood pressure [with either fluid (38%) or both fluid and a vasopressor (23%)] before antibiotic initiation. Communicated barriers to rapid antibiotic initiation included: excessive patient workload (74%), lack of awareness IV antibiotic(s) ordered (57%) or delivered (69%), need for administration of multiple non-antibiotic IV medications (54%) and no IV access (51%). Multiple nurse-related factors influence IV antibiotic(s) initiation speed and should be incorporated into sepsis quality improvement efforts. Copyright © 2017 Elsevier Ltd. All rights reserved.

High dynamic range spectroscopic studies of shocked nitromethane

NASA Astrophysics Data System (ADS)

Bhowmick, Mithun; Nissen, Erin J.; Dlott, Dana D.

In this talk we describe a tabletop apparatus that can reproducibly drive shocks through tiny cells containing liquid arranged in an array for high-throughput shock compression studies. This talk will focus on nitromethane, a liquid reactive to shocks and capable of detonation. In our studies, a laser-driven flyer plate was used to shock nitromethane, and a spectrometer with high dynamic range was employed to measure emission spectra from nanosecond to millisecond time scales. Typically, 50 single-shock experiments were performed per day with precisely controllable shock speeds below, above, or equal to the detonation shock speed. The emission spectra provide temperature histories using the graybody approximation. The ability to conveniently shock nitromethane on a benchtop will be used with isotopically substituted and amine-sensitized nitromethane and in future will be combined with other spectroscopies such as infrared absorption. Multidisciplinary University Research Initiative (MURI), Office of Naval Research.

Studies in shocked nitromethane through High dynamic range spectroscopy

NASA Astrophysics Data System (ADS)

Bhowmick, Mithun; Nissen, Erin; Matveev, Sergey; Dlott, Dana

2017-06-01

In this talk we describe a tabletop apparatus that can reproducibly drive shocks through tiny cells containing liquid arranged in an array for high-throughput shock compression studies. This talk will focus on nitromethane, a liquid reactive to shocks and capable of detonation. In our studies, a laser-driven ?yer plate was used to shock nitromethane, and a spectrometer with high dynamic range was employed to measure emission spectra from nanosecond to millisecond time scales. Typically, 50 single-shock experiments were performed per day with precisely controllable shock speeds below, above, or equal to the detonation shock speed. The emission spectra provide temperature histories using the grey body approximation. The ability to conveniently shock nitromethane on a benchtop was used with isotopically substituted and amine-sensitized nitromethane and in future will be combined with other spectroscopies such as infrared absorption. Multidisciplinary University Research Initiative (MURI), Office of Naval Research.

Rapid, in Situ Synthesis of High Capacity Battery Anodes through High Temperature Radiation-Based Thermal Shock.

PubMed

Chen, Yanan; Li, Yiju; Wang, Yanbin; Fu, Kun; Danner, Valencia A; Dai, Jiaqi; Lacey, Steven D; Yao, Yonggang; Hu, Liangbing

2016-09-14

High capacity battery electrodes require nanosized components to avoid pulverization associated with volume changes during the charge-discharge process. Additionally, these nanosized electrodes need an electronically conductive matrix to facilitate electron transport. Here, for the first time, we report a rapid thermal shock process using high-temperature radiative heating to fabricate a conductive reduced graphene oxide (RGO) composite with silicon nanoparticles. Silicon (Si) particles on the order of a few micrometers are initially embedded in the RGO host and in situ transformed into 10-15 nm nanoparticles in less than a minute through radiative heating. The as-prepared composites of ultrafine Si nanoparticles embedded in a RGO matrix show great performance as a Li-ion battery (LIB) anode. The in situ nanoparticle synthesis method can also be adopted for other high capacity battery anode materials including tin (Sn) and aluminum (Al). This method for synthesizing high capacity anodes in a RGO matrix can be envisioned for roll-to-roll nanomanufacturing due to the ease and scalability of this high-temperature radiative heating process.

Modelling the complete operation of a free-piston shock tunnel for a low enthalpy condition

NASA Astrophysics Data System (ADS)

McGilvray, M.; Dann, A. G.; Jacobs, P. A.

2013-07-01

Only a limited number of free-stream flow properties can be measured in hypersonic impulse facilities at the nozzle exit. This poses challenges for experimenters when subsequently analysing experimental data obtained from these facilities. Typically in a reflected shock tunnel, a simple analysis that requires small amounts of computational resources is used to calculate quasi-steady gas properties. This simple analysis requires initial fill conditions and experimental measurements in analytical calculations of each major flow process, using forward coupling with minor corrections to include processes that are not directly modeled. However, this simplistic approach leads to an unknown level of discrepancy to the true flow properties. To explore the simple modelling techniques accuracy, this paper details the use of transient one and two-dimensional numerical simulations of a complete facility to obtain more refined free-stream flow properties from a free-piston reflected shock tunnel operating at low-enthalpy conditions. These calculations were verified by comparison to experimental data obtained from the facility. For the condition and facility investigated, the test conditions at nozzle exit produced with the simple modelling technique agree with the time and space averaged results from the complete facility calculations to within the accuracy of the experimental measurements.

Hypertonic Saline Resuscitation Restores Inflammatory Cytokine Balance in Post-Traumatic Hemorrhagic Shock Patients

DTIC Science & Technology

2004-08-01

immunocompetant cells experience bidirectional communication with hormones and cytokines [35,40]. Thus, despite compelling experimental findings, HSD has not...hypertonic saline with 6% dextran-70 (HSD) has been shown in experimental studies to reduce shock/resuscitation-induced inflammatory reactions and...alterations have been described in clinical and experimental investigations of post-traumatic hemorrhagic shock [13]. The initial immunological

Mixing-model Sensitivity to Initial Conditions in Hydrodynamic Predictions

NASA Astrophysics Data System (ADS)

Bigelow, Josiah; Silva, Humberto; Truman, C. Randall; Vorobieff, Peter

2017-11-01

Amagat and Dalton mixing-models were studied to compare their thermodynamic prediction of shock states. Numerical simulations with the Sandia National Laboratories shock hydrodynamic code CTH modeled University of New Mexico (UNM) shock tube laboratory experiments shocking a 1:1 molar mixture of helium (He) and sulfur hexafluoride (SF6) . Five input parameters were varied for sensitivity analysis: driver section pressure, driver section density, test section pressure, test section density, and mixture ratio (mole fraction). We show via incremental Latin hypercube sampling (LHS) analysis that significant differences exist between Amagat and Dalton mixing-model predictions. The differences observed in predicted shock speeds, temperatures, and pressures grow more pronounced with higher shock speeds. Supported by NNSA Grant DE-0002913.

Uncertainty analysis for the steady-state flows in a dual throat nozzle

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Q.-Y.; Gottlieb, David; Hesthaven, Jan S.

2005-03-20

It is well known that the steady state of an isentropic flow in a dual-throat nozzle with equal throat areas is not unique. In particular there is a possibility that the flow contains a shock wave, whose location is determined solely by the initial condition. In this paper, we consider cases with uncertainty in this initial condition and use generalized polynomial chaos methods to study the steady-state solutions for stochastic initial conditions. Special interest is given to the statistics of the shock location. The polynomial chaos (PC) expansion modes are shown to be smooth functions of the spatial variable x,more » although each solution realization is discontinuous in the spatial variable x. When the variance of the initial condition is small, the probability density function of the shock location is computed with high accuracy. Otherwise, many terms are needed in the PC expansion to produce reasonable results due to the slow convergence of the PC expansion, caused by non-smoothness in random space.« less

Low Mach-number collisionless electrostatic shocks and associated ion acceleration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pusztai, Istvan; TenBarge, Jason; Csapó, Aletta N.

The existence and properties of low Mach-number (M >~ 1) electrostatic collisionless shocks are investigated with a semi-analytical solution for the shock structure. We show that the properties of the shock obtained in the semi-analytical model can be well reproduced in fully kinetic Eulerian Vlasov-Poisson simulations, where the shock is generated by the decay of an initial density discontinuity. By using this semi-analytical model, we also study the effect of electron-to-ion temperature ratio and presence of impurities on both the maximum shock potential and Mach number. We find that even a small amount of impurities can influence the shock propertiesmore » significantly, including the reflected light ion fraction, which can change several orders of magnitude. Electrostatic shocks in heavy ion plasmas reflect most of the hydrogen impurity ions.« less

Low Mach-number collisionless electrostatic shocks and associated ion acceleration

DOE PAGES

Pusztai, Istvan; TenBarge, Jason; Csapó, Aletta N.; ...

2017-12-19

The existence and properties of low Mach-number (M >~ 1) electrostatic collisionless shocks are investigated with a semi-analytical solution for the shock structure. We show that the properties of the shock obtained in the semi-analytical model can be well reproduced in fully kinetic Eulerian Vlasov-Poisson simulations, where the shock is generated by the decay of an initial density discontinuity. By using this semi-analytical model, we also study the effect of electron-to-ion temperature ratio and presence of impurities on both the maximum shock potential and Mach number. We find that even a small amount of impurities can influence the shock propertiesmore » significantly, including the reflected light ion fraction, which can change several orders of magnitude. Electrostatic shocks in heavy ion plasmas reflect most of the hydrogen impurity ions.« less

Modeling Spectral Turnovers in Interplanetary Shocks Observed by ULYSSES

NASA Astrophysics Data System (ADS)

Summerlin, E. J.; Baring, M. G.

2009-12-01

Interplanetary shocks in the heliosphere provide excellent test cases for the simulation and theory of particle acceleration at shocks thanks to the presence of in-situ measurements and a relatively well understood initial particle distribution. The Monte-Carlo test particle simulation employed in this work has been previously used to study injection and acceleration from thermal energies into the high energy power-law tail at co-rotating interaction regions (CIRs) in the heliosphere presuming a steady state planar shock (Summerlin & Baring, 2006, Baring and Summerlin, 2008). These simulated power-spectra compare favorably with in-situ measurements from the ULYSSES spacecraft below 60 keV. However, to effectively model the high energy exponential cutoff at energies above 60 keV observed in these distributions, simulations must apply spatial or temporal constraints to the acceleration process. This work studies the effects of a variety of temporal and spatial co! nstraints (including spatial constraints on the turbulent region around the shock as determined by magnetometer data, spatial constraints related to the scale size of the shock and constraints on the acceleration time based on the known limits for the shock's lifetime) on the high energy cut-off and compares simulated particle spectra to those observed by the ULYSSES HI-SCALE instrument in an effort to determine which constraint is creating the cut-off and using that constraining parameter to determine additional information about the shock that can not, normally, be determined by a single data point, such as the spatial extent of the shock or how long the shock has been propagating through the heliosphere before it encounters the spacecraft. Shocks observed by multiple spacecraft will be of particular interest as their parameters will be better constrained than shocks observed by only one spacecraft. To achieve these goals, the simulation will be modified to include the re! trodictive approach of Jones (1978) to accurately track time spent dow nstream while maintaining, to large degree, the large dynamic range and short run times that make this type of simulation so attractive. This work is inspired by examinations of acceleration cutoffs in SEP events performed by various authors (see Li et al., 2009, and references therein), and it is hoped that this work will pave the way for a multi-species analysis similar to theirs that should greatly enhance the information one can derive about shocks based on individual observations.

On the Exit Boundary Condition for One-Dimensional Calculations of Pulsed Detonation Engine Performance

NASA Technical Reports Server (NTRS)

Wilson, Jack; Paxson, Daniel E.

2002-01-01

In one-dimensional calculations of pulsed detonation engine (PDE) performance, the exit boundary condition is frequently taken to be a constant static pressure. In reality, for an isolated detonation tube, after the detonation wave arrives at the exit plane, there will be a region of high pressure, which will gradually return to ambient pressure as an almost spherical shock wave expands away from the exit, and weakens. Initially, the flow is supersonic, unaffected by external pressure, but later becomes subsonic. Previous authors have accounted for this situation either by assuming the subsonic pressure decay to be a relaxation phenomenon, or by running a two-dimensional calculation first, including a domain external to the detonation tube, and using the resulting exit pressure temporal distribution as the boundary condition for one-dimensional calculations. These calculations show that the increased pressure does affect the PDE performance. In the present work, a simple model of the exit process is used to estimate the pressure decay time. The planar shock wave emerging from the tube is assumed to transform into a spherical shock wave. The initial strength of the spherical shock wave is determined from comparison with experimental results. Its subsequent propagation, and resulting pressure at the tube exit, is given by a numerical blast wave calculation. The model agrees reasonably well with other, limited, results. Finally, the model was used as the exit boundary condition for a one-dimensional calculation of PDE performance to obtain the thrust wall pressure for a hydrogen-air detonation in tubes of length to diameter ratio (L/D) of 4, and 10, as well as for the original, constant pressure boundary condition. The modified boundary condition had no performance impact for values of L/D > 10, and moderate impact for L/D = 4.

Effects of AED device features on performance by untrained laypersons.

PubMed

Mosesso, Vincent N; Shapiro, Alan H; Stein, Karen; Burkett, Kelly; Wang, Henry

2009-11-01

Our study evaluates the impact of features of automated external defibrillators (AEDs) on the performance and speed of untrained laypersons to deliver a shock and initiate CPR after a shock. This was a randomized trial of volunteer laypersons without AED or advanced medical training. Subjects were assigned to use one of six different models of AEDs on a manikin in simulated cardiac arrest. No instructions on AED operation were provided. Primary endpoints were shock delivery and elapsed time from start to shock. Secondary endpoints included time to power-on, initiation of CPR, adequacy of pad placement and subjects' ratings of ease of use (1=very easy, 5=very difficult). Most subjects (109/120; 91%) were able to deliver a shock. Median time from start of scenario to shock delivery was 79 s (IQR: 67-99). Of the 11 participants who did not deliver shock, eight never powered on the device. Time to power-on was shorter in devices with open lid (median 12s, IQR 8-27 s) and pull handle (17s, IQR 9-20s) mechanisms than with a push button (37s, IQR 18-69 s; p=0.000). Pad position on the manikin was judged adequate for 86 (77%) of the 111 subjects who placed pads. Devices which gave more detailed voice instruction for pad placement had higher rates of adequate pad position [38/39 (97%) versus 50/73 (68%), p=0.001]. With AEDs that provided step-by-step CPR instruction, 49/58 (84%) subjects began CPR compared to 26/51 (51%) with AEDs that only prompted to start CPR (p=0.01). Participants rated all the models easy to use (overall mean 1.48; individual device means 1.28-1.71). Most untrained laypersons were successful in delivering a shock. Device features had the most impact on these functions: ability and time to power-on device, adequacy of pad position and initiation of CPR.

Particle Methods for Simulating Atomic Radiation in Hypersonic Reentry Flows

NASA Astrophysics Data System (ADS)

Ozawa, T.; Wang, A.; Levin, D. A.; Modest, M.

2008-12-01

With a fast reentry speed, the Stardust vehicle generates a strong shock region ahead of its blunt body with a temperature above 60,000 K. These extreme Mach number flows are sufficiently energetic to initiate gas ionization processes and thermal and chemical ablation processes. The nonequilibrium gaseous radiation from the shock layer is so strong that it affects the flowfield macroparameter distributions. In this work, we present the first loosely coupled direct simulation Monte Carlo (DSMC) simulations with the particle-based photon Monte Carlo (p-PMC) method to simulate high-Mach number reentry flows in the near-continuum flow regime. To efficiently capture the highly nonequilibrium effects, emission and absorption cross section databases using the Nonequilibrium Air Radiation (NEQAIR) were generated, and atomic nitrogen and oxygen radiative transport was calculated by the p-PMC method. The radiation energy change calculated by the p-PMC method has been coupled in the DSMC calculations, and the atomic radiation was found to modify the flow field and heat flux at the wall.

Shock tubes and waves; Proceedings of the Sixteenth International Symposium, Rheinisch-Westfaelische Technische Hochschule, Aachen, Federal Republic of Germany, July 26-31, 1987

NASA Astrophysics Data System (ADS)

Groenig, Hans

Topics discussed in this volume include shock wave structure, propagation, and interaction; shocks in condensed matter, dusty gases, and multiphase media; chemical processes and related combustion and detonation phenomena; shock wave reflection, diffraction, and focusing; computational fluid dynamic code development and shock wave application; blast and detonation waves; advanced shock tube technology and measuring technique; and shock wave applications. Papers are presented on dust explosions, the dynamics of shock waves in certain dense gases, studies of condensation kinetics behind incident shock waves, the autoignition mechanism of n-butane behind a reflected shock wave, and a numerical simulation of the focusing process of reflected shock waves. Attention is also given to the equilibrium shock tube flow of real gases, blast waves generated by planar detonations, modern diagnostic methods for high-speed flows, and interaction between induced waves and electric discharge in a very high repetition rate excimer laser.

On the propagation of decaying planar shock and blast waves through non-uniform channels

NASA Astrophysics Data System (ADS)

Peace, J. T.; Lu, F. K.

2018-05-01

The propagation of planar decaying shock and blast waves in non-uniform channels is investigated with the use of a two-equation approximation of the generalized CCW theory. The effects of flow non-uniformity for the cases of an arbitrary strength decaying shock and blast wave in the strong shock limit are considered. Unlike the original CCW theory, the two-equation approximation takes into account the effects of initial temporal flow gradients in the flow properties behind the shock as the shock encounters an area change. A generalized order-of-magnitude analysis is carried out to analyze under which conditions the classical area-Mach (A-M) relation and two-equation approximation are valid given a time constant of decay for the flow properties behind the shock. It is shown that the two-equation approximation extends the applicability of the CCW theory to problems where flow non-uniformity behind the shock is orders of magnitude above that for appropriate use of the A-M relation. The behavior of the two-equation solution is presented for converging and diverging channels and compared against the A-M relation. It is shown that the second-order approximation and A-M relation have good agreement for converging geometries, such that the influence of flow non-uniformity behind the shock is negligible compared to the effects of changing area. Alternatively, the two-equation approximation is shown to be strongly dependent on the initial magnitude of flow non-uniformity in diverging geometries. Further, in diverging geometries, the inclusion of flow non-uniformity yields shock solutions that tend toward an acoustic wave faster than that predicted by the A-M relation.

Creating a Driven, Collapsed Radiative Shock in the Laboratory

NASA Astrophysics Data System (ADS)

Reighard, Amy

2006-10-01

We report details of the first experimental campaign to create a driven, planar, radiatively collapsed in laboratory experiment. Radiation hydrodynamics experiments are challenging to realize in a laboratory setting, requiring high temperatures in a system of sufficient extent. The Omega laser at ˜10^15 W/cm^2 drives a thin slab of low-Z material at >100 km/s gas via laser ablation pressure. This slab initially shocks, then continues driving a shock through a cylindrical volume of Xe gas at 6 mg/cc. Simulations predict a collapsed layer in which the density reaches ˜45 times initial density. Side-on x-ray backlighting was the principal diagnostic. We have successfully imaged shocks with average velocities between 95-205 km/sec, with measured thicknesses of 45-150 μm in experiments lasting up to 20 ns and spanning up 2.5 mm in extent. Comparison of the shock position as a function of time from these experiments to 1D radiation hydrodynamic simulation results show some discrepancy, which will be explored. Optical depth before and behind the shock is important for meaningful comparison to these astrophysical systems. This shock is optically thin to emitted radiation in the unshocked region and optically thick to radiation in the shocked, dense region. We compare this system to collapsed shocks in astrophysical systems with similar optical depth profiles. An experiment using a Thomson scattering diagnostic across the shock front is also discussed. This research was sponsored by the National Nuclear Security Administration under the Stewardship Science Academic Alliances program through DOE Research Grants DE-FG52-03NA00064, DE-FG53-2005-NA26014, and other grants and contracts.

Multiscale modeling of shock wave localization in porous energetic material

NASA Astrophysics Data System (ADS)

Wood, M. A.; Kittell, D. E.; Yarrington, C. D.; Thompson, A. P.

2018-01-01

Shock wave interactions with defects, such as pores, are known to play a key role in the chemical initiation of energetic materials. The shock response of hexanitrostilbene is studied through a combination of large-scale reactive molecular dynamics and mesoscale hydrodynamic simulations. In order to extend our simulation capability at the mesoscale to include weak shock conditions (<6 GPa), atomistic simulations of pore collapse are used to define a strain-rate-dependent strength model. Comparing these simulation methods allows us to impose physically reasonable constraints on the mesoscale model parameters. In doing so, we have been able to study shock waves interacting with pores as a function of this viscoplastic material response. We find that the pore collapse behavior of weak shocks is characteristically different than that of strong shocks.

Geometrical shock dynamics, formation of singularities and topological bifurcations of converging shock fronts

NASA Astrophysics Data System (ADS)

Suramlishvili, Nugzar; Eggers, Jens; Fontelos, Marco

2014-11-01

We are concerned with singularities of the shock fronts of converging perturbed shock waves. Our considerations are based on Whitham's theory of geometrical shock dynamics. The recently developed method of local analysis is applied in order to determine generic singularities. In this case the solutions of partial differential equations describing the geometry of the shock fronts are presented as families of smooth maps with state variables and the set of control parameters dependent on Mach number, time and initial conditions. The space of control parameters of the singularities is analysed, the unfoldings describing the deformations of the canonical germs of shock front singularities are found and corresponding bifurcation diagrams are constructed. Research is supported by the Leverhulme Trust, Grant Number RPG-2012-568.

The Acceleration of Charged Particles at a Spherical Shock Moving through an Irregular Magnetic Field

DOE Office of Scientific and Technical Information (OSTI.GOV)

Giacalone, J.

We investigate the physics of charged-particle acceleration at spherical shocks moving into a uniform plasma containing a turbulent magnetic field with a uniform mean. This has applications to particle acceleration at astrophysical shocks, most notably, to supernovae blast waves. We numerically integrate the equations of motion of a large number of test protons moving under the influence of electric and magnetic fields determined from a kinematically defined plasma flow associated with a radially propagating blast wave. Distribution functions are determined from the positions and velocities of the protons. The unshocked plasma contains a magnetic field with a uniform mean andmore » an irregular component having a Kolmogorov-like power spectrum. The field inside the blast wave is determined from Maxwell’s equations. The angle between the average magnetic field and unit normal to the shock varies with position along its surface. It is quasi-perpendicular to the unit normal near the sphere’s equator, and quasi-parallel to it near the poles. We find that the highest intensities of particles, accelerated by the shock, are at the poles of the blast wave. The particles “collect” at the poles as they approximately adhere to magnetic field lines that move poleward from their initial encounter with the shock at the equator, as the shock expands. The field lines at the poles have been connected to the shock the longest. We also find that the highest-energy protons are initially accelerated near the equator or near the quasi-perpendicular portion of the shock, where the acceleration is more rapid.« less

Gap Test Calibrations and Their Scaling

NASA Astrophysics Data System (ADS)

Sandusky, Harold

2011-06-01

Common tests for measuring the threshold for shock initiation are the NOL large scale gap test (LSGT) with a 50.8-mm diameter donor/gap and the expanded large scale gap test (ELSGT) with a 95.3-mm diameter donor/gap. Despite the same specifications for the explosive donor and polymethyl methacrylate (PMMA) gap in both tests, calibration of shock pressure in the gap versus distance from the donor scales by a factor of 1.75, not the 1.875 difference in their sizes. Recently reported model calculations suggest that the scaling discrepancy results from the viscoelastic properties of PMMA in combination with different methods for obtaining shock pressure. This is supported by the consistent scaling of these donors when calibrated in water-filled aquariums. Calibrations with water gaps will be provided and compared with PMMA gaps. Scaling for other donor systems will also be provided. Shock initiation data with water gaps will be reviewed.

TIMING OF SHOCK WAVES

DOEpatents

Tuck, J.L.

1955-03-01

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

Ignition and Growth Reactive Flow Modeling of Shock Initiation of PBX 9502 at -55∘C and -196∘C

NASA Astrophysics Data System (ADS)

Chidester, Steven; Tarver, Craig

2015-06-01

Recently Gustavsen et al. and Hollowell et al. published two stage gas gun embedded particle velocity gauge experiments on PBX 9502 (95%TATB, 5% Kel-F800) cooled to -55°C and -196°C, respectively. At -196°C, PBX 9502 was shown to be much less shock sensitive than at -55°C, but it did transition to detonation. Previous Ignition and Growth model parameters for shock initiation of PBX 9502 at -55°C are modified based on the new data, and new parameters for -196°C PBX 9502 are created to accurately simulate the measured particle velocity histories and run distances to detonation versus shock pressures. This work was performed under the auspices of the U. S. Department of Energy by the Lawrence Livermore National Laboratory under Contract No. DE-AC52-07NA27344.

A shock surface geometry - The February 15-16, 1967, event. [solar flare associated interplanetary shock

NASA Technical Reports Server (NTRS)

Lepping, R. P.; Chao, J. K.

1976-01-01

An estimated shape is presented for the surface of the flare-associated interplanetary shock of February 15-16, 1967, as seen in the ecliptic-plane cross section. The estimate is based on observations by Explorer 33 and Pioneers 6 and 7. The estimated shock normal at the Explorer 33 position is obtained by a least-squares shock parameter-fitting procedure for that satellite's data; the shock normal at the Pioneer 7 position is found by using the magnetic coplanarity theorem and magnetic-field data. The average shock speed from the sun to each spacecraft is determined along with the local speed at Explorer 33 and the relations between these speeds and the position of the initiating solar flare. The Explorer 33 shock normal is found to be severely inclined and not typical of interplanetary shocks. It is shown that the curvature of the shock surface in the ecliptic plane near the earth-Pioneer 7 region is consistent with a radius of not more than 0.4 AU.

Shock waves and shock tubes; Proceedings of the Fifteenth International Symposium, Berkeley, CA, July 28-August 2, 1985

NASA Technical Reports Server (NTRS)

Bershader, D. (Editor); Hanson, R. (Editor)

1986-01-01

A detailed survey is presented of shock tube experiments, theoretical developments, and applications being carried out worldwide. The discussions explore shock tube physics and the related chemical, physical and biological science and technology. Extensive attention is devoted to shock wave phenomena in dusty gases and other multiphase and heterogeneous systems, including chemically reactive mixtures. Consideration is given to techniques for measuring, visualizing and theoretically modeling flowfield, shock wave and rarefaction wave characteristics. Numerical modeling is explored in terms of the application of computational fluid dynamics techniques to describing flowfields in shock tubes. Shock interactions and propagation, in both solids, fluids, gases and mixed media are investigated, along with the behavior of shocks in condensed matter. Finally, chemical reactions that are initiated as the result of passage of a shock wave are discussed, together with methods of controlling the evolution of laminar separated flows at concave corners on advanced reentry vehicles.

Shock waves and shock tubes; Proceedings of the Fifteenth International Symposium, Berkeley, CA, July 28-August 2, 1985

NASA Astrophysics Data System (ADS)

Bershader, D.; Hanson, R.

A detailed survey is presented of shock tube experiments, theoretical developments, and applications being carried out worldwide. The discussions explore shock tube physics and the related chemical, physical and biological science and technology. Extensive attention is devoted to shock wave phenomena in dusty gases and other multiphase and heterogeneous systems, including chemically reactive mixtures. Consideration is given to techniques for measuring, visualizing and theoretically modeling flowfield, shock wave and rarefaction wave characteristics. Numerical modeling is explored in terms of the application of computational fluid dynamics techniques to describing flowfields in shock tubes. Shock interactions and propagation, in both solids, fluids, gases and mixed media are investigated, along with the behavior of shocks in condensed matter. Finally, chemical reactions that are initiated as the result of passage of a shock wave are discussed, together with methods of controlling the evolution of laminar separated flows at concave corners on advanced reentry vehicles.

Timing of vasopressor initiation and mortality in septic shock: a cohort study

PubMed Central

2014-01-01

Introduction Despite recent advances in the management of septic shock, mortality remains unacceptably high. Earlier initiation of key therapies including appropriate antimicrobials and fluid resuscitation appears to reduce the mortality in this condition. This study examined whether early initiation of vasopressor therapy is associated with improved survival in fluid therapy-refractory septic shock. Methods Utilizing a well-established database, relevant information including duration of time to vasopressor administration following the initial documentation of recurrent/persistent hypotension associated with septic shock was assessed in 8,670 adult patients from 28 ICUs in Canada, the United States of America, and Saudi Arabia. The primary endpoint was survival to hospital discharge. Secondary endpoints were length of ICU and hospital stay as well as duration of ventilator support and vasopressor dependence. Analysis involved multivariate linear and logistic regression analysis. Results In total, 8,640 patients met the definition of septic shock with time of vasopressor/inotropic initiation documented. Of these, 6,514 were suitable for analysis. The overall unadjusted hospital mortality rate was 53%. Independent mortality correlates included liver failure (odds ratio (OR) 3.46, 95% confidence interval (CI), 2.67 to 4.48), metastatic cancer (OR 1.63, CI, 1.32 to 2.01), AIDS (OR 1.91, CI, 1.29 to 2.49), hematologic malignancy (OR 1.88, CI, 1.46 to 2.41), neutropenia (OR 1.78, CI, 1.27 to 2.49) and chronic hypertension (OR 0.62 CI, 0.52 to 0.73). Delay of initiation of appropriate antimicrobial therapy (OR 1.07/hr, CI, 1.06 to 1.08), age (OR 1.03/yr, CI, 1.02 to 1.03), and Acute Physiology and Chronic Health Evaluation (APACHE) II Score (OR 1.11/point, CI, 1.10 to 1.12) were also found to be significant independent correlates of mortality. After adjustment, only a weak correlation between vasopressor delay and hospital mortality was found (adjusted OR 1.02/hr, 95% CI 1.01 to 1.03, P <0.001). This weak effect was entirely driven by the group of patients with the longest delays (>14.1 hours). There was no significant relationship of vasopressor initiation delay to duration of vasopressor therapy (P = 0.313) and only a trend to longer duration of ventilator support (P = 0.055) among survivors. Conclusion Marked delays in initiation of vasopressor/inotropic therapy are associated with a small increase in mortality risk in patients with septic shock. PMID:24887489

Dynamics of formation of low-angle tilt boundaries in metals and alloys at high loading rates

NASA Astrophysics Data System (ADS)

Gutkin, M. Yu.; Rzhavtsev, E. A.

2015-12-01

A computer model has been developed in which the process of formation of low-angle tilt boundaries and fragmentation of initial subgrains during shock loading of metals and alloys is clearly demonstrated by the of two-dimensional discrete dislocation-disclination dynamics method. The formation and evolution of such grains proceeds under the action of an external stress and the stress field of grain boundary disclinations distributed on the subgrain boundaries. With the D16 aluminum alloy as an example, three cases of fragmented structures formed in accordance with the initial configuration of the disclination ensemble have been considered for a dipole, quadrupole, and arbitrary octupole of wedge disclinations. It has been shown that, in all these cases, the formation of a stable fragmented structure requires a stress of ~0.5 GPa and time of 10 ns. The main results of computer simulation (the finite form of a fragmented structure, typical level of applied stress, and small fragmentation time) agree well with known experimental results on shock compression of the D16 aluminum alloy.

Prognosis of patients excluded by the definition of septic shock based on their lactate levels after initial fluid resuscitation: a prospective multi-center observational study.

PubMed

Ko, Byuk Sung; Kim, Kyuseok; Choi, Sung-Hyuk; Kang, Gu Hyun; Shin, Tae Gun; Jo, You Hwan; Ryoo, Seung Mok; Beom, Jin Ho; Kwon, Woon Yong; Han, Kap Su; Choi, Han Sung; Chung, Sung Phil; Suh, Gil Joon; Lim, Tae Ho; Kim, Won Young

2018-02-24

Septic shock can be defined both by the presence of hyperlactatemia and need of vasopressors. Lactate levels should be measured after volume resuscitation (as per the Sepsis-3 definition). However, currently, no studies have evaluated patients who have been excluded by the new criteria for septic shock. The aim of this study was to determine the clinical characteristics and prognosis of these patients, based on their lactate levels after initial fluid resuscitation. This observational study was performed using a prospective, multi-center registry of septic shock, with the participation of 10 hospitals in the Korean Shock Society, between October 2015 and February 2017. We compared the 28-day mortality between patients who were excluded from the new definition (defined as lactate level <2 mmol/L after volume resuscitation) and those who were not (≥2 mmol/L after volume resuscitation), from among a cohort of patients with refractory hypotension, and requiring the use of vasopressors. Other outcome variables such as in-hospital mortality, intensive care unit (ICU) stay (days), Sequential Organ Failure Assessment (SOFA) scores and Acute Physiology and Chronic Health Evaluation (APACHE) II scores were also analyzed. Of 567 patients with refractory hypotension, requiring the use of vasopressors, 435 had elevated lactate levels, while 83 did not have elevated lactate levels (either initially or after volume resuscitation), and 49 (8.2%) had elevated lactate levels initially, which normalized after fluid resuscitation. Thus, these 49 patients were excluded by the new definition of septic shock. These patients, in whom perfusion was restored, demonstrated significantly lower age, platelet count, and initial and subsequent lactate levels (all p < 0.01). Similarly, significantly lower 28-day mortality was observed in these patients than in those who had not been excluded (8.2% vs 25.5%, p = 0.02). In-hospital mortality and the maximum SOFA score were also significantly lower in the excluded patients group (p = 0.03, both). It seems reasonable for septic shock to be defined by the lactate levels after volume resuscitation. However, owing to the small number of patients in whom lactate levels were improved, further study is warranted.

Influence of Flow Gradients on Mach Stem Initiation of PBX-9502

NASA Astrophysics Data System (ADS)

Hull, Lawrence; Miller, Phillip; Mas, Eric; Focused Experiments Team

2017-06-01

Recent experiments and theory explore the effect of flow gradients on reaction acceleration and stability in the pressure-enhanced region between colliding sub-detonative shock waves in PBX-9502. The experiments are designed to produce divergent curved incident shock waves that interact in a convergent irregular reflection, or ``Mach stem'', configuration. Although this flow is fundamentally unsteady, such a configuration does feature particle paths having a single shock wave that increases the pressure from zero to the wave-reflected enhanced pressure. Thus, the possibility of pre-shock desensitization is precluded in this interaction region. Diagnostics record arrival wave velocity, shape, and material velocity along the angled free surface face of a large wedge. The wedge is large enough to allow observation of the wave structure for distances much larger than the run-to-detonation derived from classical ``Pop plot'' data. The explosive driver system produces the incident shocks and allows some control of the flow gradients in the collision region. Further, the incident shocks are very weak and do not transition to detonation. The experiments discussed feature incident shock waves that would be expected to cause initiation in the Mach stem, based on the Pop plot. Results show that the introduction of pressure/velocity gradients in the reaction zone strongly influences the ability of the flow to build to a steady ``CJ'' detonation. As expected, the ability of the Mach stem to stabilize or accelerate is strongly influenced by the incident shock pressure.

Complex flow morphologies in shock-accelerated gaseous flows

NASA Astrophysics Data System (ADS)

Kumar, S.; Vorobieff, P.; Orlicz, G.; Palekar, A.; Tomkins, C.; Goodenough, C.; Marr-Lyon, M.; Prestridge, K. P.; Benjamin, R. F.

2007-11-01

A Mach 1.2 planar shock wave impulsively and simultaneously accelerates a row of three heavy gas (SF 6) cylinders surrounded by a lighter gas (air), producing pairs of vortex columns. The heavy gas cylinders (nozzle diameter D) are initially equidistant in the spanwise direction (center to center spacing S), with S/D=1.5. The interaction of the vortex columns is investigated with planar laser-induced fluorescence (PLIF) in the plane normal to the axes of the cylinders. Several distinct post-shock morphologies are observed, apparently due to rather small variations of the initial conditions. We report the variation of the streamwise and spanwise growth rates of the integral scales for these flow morphologies.

A detonation wave in the system liquid-gas bubbles

NASA Astrophysics Data System (ADS)

Sychev, A. I.

1985-06-01

The shock-wave ignition of a system consisting of a liquid (H2O) and bubbles of an explosive gas mixture (C2H2+2.5O2) is investigated experimentally and analytically. The possibility of the existence of a detonation wave, a supersonic self-sustaining process, in a gas-liquid system is demonstrated. The conditions for the existence of a detonation wave are determined, and the initiation mechanism is analyzed.

Roles of heat shock factors in gametogenesis and development.

PubMed

Abane, Ryma; Mezger, Valérie

2010-10-01

Heat shock factors form a family of transcription factors (four in mammals), which were named according to the first discovery of their activation by heat shock. As a result of the universality and robustness of their response to heat shock, the stress-dependent activation of heat shock factor became a ‘paradigm’: by binding to conserved DNA sequences (heat shock elements), heat shock factors trigger the expression of genes encoding heat shock proteins that function as molecular chaperones, contributing to establish a cytoprotective state to various proteotoxic stress and in several pathological conditions. Besides their roles in the stress response, heat shock factors perform crucial roles during gametogenesis and development in physiological conditions. First, during these process, in stress conditions, they are either proactive for survival or, conversely, for apoptotic process, allowing elimination or, inversely, protection of certain cell populations in a way that prevents the formation of damaged gametes and secure future reproductive success. Second, heat shock factors display subtle interplay in a tissue- and stage-specific manner, in regulating very specific sets of heat shock genes, but also many other genes encoding growth factors or involved in cytoskeletal dynamics. Third, they act not only by their classical transcription factor activities, but are necessary for the establishment of chromatin structure and, likely, genome stability. Finally, in contrast to the heat shock gene paradigm, heat shock elements bound by heat shock factors in developmental process turn out to be extremely dispersed in the genome, which is susceptible to lead to the future definition of ‘developmental heat shock element’.

On the Initiation Mechanism in Exploding Bridgewire and Laser Detonators

NASA Astrophysics Data System (ADS)

Stewart, D. Scott; Thomas, Keith A.; Clarke, S.; Mallett, H.; Martin, E.; Martinez, M.; Munger, A.; Saenz, Juan

2006-07-01

Since its invention by Los Alamos during the Manhattan Project era the exploding bridgewire detonator (EBW) has seen tremendous use and study. Recent development of a laser-powered device with detonation properties similar to an EBW is reviving interest in the basic physics of the deflagration-to-detonation (DDT) process in both of these devices. Cutback experiments using both laser interferometry and streak camera observations are providing new insight into the initiation mechanism in EBWs. These measurements are being correlated to a DDT model of compaction to detonation and shock to detonation developed previously by Xu and Stewart. The DDT model is incorporated into a high-resolution, multi-material model code for simulating the complete process. Model formulation and the modeling issues required to describe the test data will be discussed.

Recurrent menstrual toxic shock syndrome despite discontinuation of tampon use: is menstrual toxic shock syndrome really caused by tampons?

PubMed

Dixit, Shreya; Fischer, Gayle; Wittekind, Carola

2013-11-01

Menstrual toxic shock syndrome (MTSS) is a rare and potentially life-threatening illness. We present a case of recurrent MTSS initially associated with tampon use that continued to recur when tampons were discontinued, which was successfully treated with rifampicin and clindamycin. © 2012 The Authors Australasian Journal of Dermatology © 2012 The Australasian College of Dermatologists.

Investigation of heavy current discharges with high initial gas density

NASA Astrophysics Data System (ADS)

Budin, A.; Bogomaz, A.; Kolikov, V.; Kuprin, A.; Leontiev, V.; Rutberg, Ph.; Shirokov, N.

1996-05-01

Piezoelectric pressure transducers, with noise immunity and time resolution of 0,5 μs were used to measure pulse pressures of 430 MPa along the axis of an electrical discharge channel. Initial concentration of He was 2,7ṡ1021cm-3, dI/dt=6ṡ1011 A/s, and Imax=560 kA. Shock waves with amplitudes exceeding the pressure along the axis, were detected by a pressure transducer on the wall of the discharge chamber. Typical shock velocities were 2ṡ4 km/s. Average pressure measurements along the discharge axis at different radii were used to estimate the current density distribution along the canal radius. The presence of the shock waves, promoting the additional hydrogen heating in the discharge chamber, has been registered during the discharge in hydrogen for Imax˜1 MA and an initial concentration of 1021cm-3.

Magma ocean formation due to giant impacts

NASA Technical Reports Server (NTRS)

Tonks, W. B.; Melosh, H. J.

1993-01-01

The thermal effects of giant impacts are studied by estimating the melt volume generated by the initial shock wave and corresponding magma ocean depths. Additionally, the effects of the planet's initial temperature on the generated melt volume are examined. The shock pressure required to completely melt the material is determined using the Hugoniot curve plotted in pressure-entropy space. Once the melting pressure is known, an impact melting model is used to estimate the radial distance melting occurred from the impact site. The melt region's geometry then determines the associated melt volume. The model is also used to estimate the partial melt volume. Magma ocean depths resulting from both excavated and retained melt are calculated, and the melt fraction not excavated during the formation of the crater is estimated. The fraction of a planet melted by the initial shock wave is also estimated using the model.

Initial resuscitation and management of pediatric septic shock

PubMed Central

Martin, Kelly; Weiss, Scott L.

2015-01-01

The pediatric sepsis syndrome remains a common cause of morbidity, mortality, and health care utilization costs worldwide. The initial resuscitation and management of pediatric sepsis is focused on 1) rapid recognition of abnormal tissue perfusion and restoration of adequate cardiovascular function, 2) eradication of the inciting invasive infection, including prompt administration of empiric broad-spectrum antimicrobial medications, and 3) supportive care of organ system dysfunction. Efforts to improve early and aggressive initial resuscitation and ongoing management strategies have improved outcomes in pediatric severe sepsis and septic shock, though many questions still remain as to the optimal therapeutic strategies for many patients. In this article, we will briefly review the definitions, epidemiology, clinical manifestations, and pathophysiology of sepsis and provide an extensive overview of both current and novel therapeutic strategies used to resuscitate and manage pediatric patients with severe sepsis and septic shock. PMID:25604591

Effects of Initial Conditions on Shock Driven Flows

NASA Astrophysics Data System (ADS)

Martinez, Adam A.; Mula, Swathi M.; Charonko, John; Prestridge, Kathy

2017-11-01

The spatial and temporal evolution of shock-driven, variable density flows, such as the Richtmyer Meshkov (RM) instability, are strongly influenced by the initial conditions (IC's) of the flow at the time of interaction with shockwave. We study the effects of the IC's on the Vertical Shock Tube (VST) and on flows from Mach =1.2 to Mach =9. Experiments at the VST are of an Air-SF6 (At =0.6) multimode interface. Perturbations are generated using a shear layer with a flapper plate. Planar Laser Induced Fluorescence (PLIF) is used to characterize the IC's. New experiments are occurring using the Powder Gun driver at LANL Proton Radiography (pRad) facility. Mach number up to M =9 accelerate a Xenon-Helium (At =0.94) interface that is perturbed using a membrane supported by different sized grids. This presentation focuses on how to design and characterize different types of initial conditions for experiments.

Plasma Gradient Piston: a new approach to precision pulse shaping

NASA Astrophysics Data System (ADS)

Prisbrey, Shon T.

2011-10-01

We have successfully developed a method to create shaped pressure drives from large shocks that can be applied to a wide variety of experimental platforms. The method consists of transforming a large shock or blast wave into a ramped pressured drive by utilizing a graded density reservoir that unloads across a gap and stagnates against the sample being studied. The utilization of a graded density reservoir, different materials, and a gap transforms the energy in the initial large shock into a quasi-isentropic ramped compression. Control of the ramp history is via the size of the initial shock, the chosen reservoir materials, their densities, the thickness of each density layer, and the gap size. There are two keys to utilizing this approach to create ramped drives: the ability to produce a large shock, and making the layered density reservoir. A number of facilities can produce the strong initial shock (Z, Omega, NIF, Phoenix, high explosives, NIKE, LMJ, pulsed power,...). We have demonstrated ramped drives from 0.5 to 1.5 Mbar utilizing a large shock created at the Omega laser facility. We recently concluded a pair of NIF drive shots where we successfully converted a hohlraum-generated shock into a stepped, ramped pressure drive with a peak pressure of ~4 - 5 Mbar in a Ta sample. We will explain the basic concepts needed for producing a ramped pressure drive, compare experimental data with simulations from Omega (Pmax ~ 1 Mbar) and NIF (Pmax ~ 5-10 Mbar), and present designs for ramped, staged-shock designs up to Pmax ~ 30 Mbar. The approach that we have developed enables precision pulse shaping of the drive (applied pressure vs. time) via target characteristics, as opposed to tailoring laser power vs time or Z-pinch facility current vs time. This enables ramped, quasi-isentropic materials studies to be performed on a wide variety of HED facilities. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. LLNL-ABS-490532.

From avoidance to approach: The influence of threat-of-shock on reward-based decision making.

PubMed

Bublatzky, Florian; Alpers, Georg W; Pittig, Andre

2017-09-01

Potential threat can prime defensive responding and avoidance behavior, which may result in the loss of rewards. When aversive consequences do not occur, avoidance should, thus, be quickly overcome in healthy individuals. This study examined the impact of threat anticipation on reward-based decisions. Sixty-five participants completed a decision-making task in which they had to choose between high- and low-reward options. To model an approach-avoidance conflict, the high-reward option was contingent with a threat-of-shock cue; the low-reward option was contingent with a safety cue. In control trials, decisions were made without threat/safety instructions. Overall, behavioral data documented a typical preference for the profitable option. Importantly, under threat-of-shock, participants initially avoided the profitable option (i.e., safe, but less profitable choices). However, when they experienced that shocks did actually not occur, participants overcame initial avoidance in favor of larger gains. Furthermore, autonomic arousal (skin conductance and heart rate responses) was elevated during threat cues compared to safety and non-threatening control cues. Taken together, threat-of-shock was associated with behavioral consequences: initially, participants avoided threat-related options but made more profitable decisions as they experienced no aversive consequences. Although socially acquired threat contingencies are typically stable, incentives for approach can help to overcome threat-related avoidance. Copyright © 2017 Elsevier Ltd. All rights reserved.

Molecular line emission models of Herbig-Haro objects. II - HCO(+) emission

NASA Technical Reports Server (NTRS)

Wolfire, Mark G.; Koenigl, Arieh

1993-01-01

We present time-dependent models of the chemistry and temperature of interstellar molecular gas clumps that are exposed to the radiation from propagating stellar-jet shocks. The X-ray, EUV, and FUV radiation from the shock initiates ion chemistry and also heats the gas in the clumps. Using representative parameters, we show that, on the shock transit time between the clumps, the abundances of the ionized molecular species that are produced in the clumps can exceed the values determined from steady state models by several orders of magnitude. Collisional excitation by the heated gas can lead to measurable line emission from several ionized species; as in previous investigations of X-ray-irradiated molecular gas, we find that electron impacts contribute significantly to this process. We apply these results to the interpretation of the HCO(+) line emission that has already been detected in several Herbig-Haro objects. We demonstrate that this picture provides a natural explanation of the fact that the line intensity typically peaks ahead of the associated shock, as well as of the reported low line-center velocities and narrow line widths. We tabulate several diagnostic line intensities of HCO(+) and other molecular species that may be used to infer the physical conditions in the emitting gas.

Shock-induced termination of reentrant cardiac arrhythmias: Comparing monophasic and biphasic shock protocols

NASA Astrophysics Data System (ADS)

Bragard, Jean; Simic, Ana; Elorza, Jorge; Grigoriev, Roman O.; Cherry, Elizabeth M.; Gilmour, Robert F.; Otani, Niels F.; Fenton, Flavio H.

2013-12-01

In this article, we compare quantitatively the efficiency of three different protocols commonly used in commercial defibrillators. These are based on monophasic and both symmetric and asymmetric biphasic shocks. A numerical one-dimensional model of cardiac tissue using the bidomain formulation is used in order to test the different protocols. In particular, we performed a total of 4.8 × 106 simulations by varying shock waveform, shock energy, initial conditions, and heterogeneity in internal electrical conductivity. Whenever the shock successfully removed the reentrant dynamics in the tissue, we classified the mechanism. The analysis of the numerical data shows that biphasic shocks are significantly more efficient (by about 25%) than the corresponding monophasic ones. We determine that the increase in efficiency of the biphasic shocks can be explained by the higher proportion of newly excited tissue through the mechanism of direct activation.

Direct Numerical Simulation of Passive Scalar Mixing in Shock Turbulence Interaction

NASA Astrophysics Data System (ADS)

Gao, Xiangyu; Bermejo-Moreno, Ivan; Larsson, Johan

2017-11-01

Passive scalar mixing in the canonical shock-turbulence interaction configuration is investigated through shock-capturing Direct Numerical Simulations (DNS). Scalar fields with different Schmidt numbers are transported by an initially isotropic turbulent flow field passing across a nominally planar shock wave. A solution-adaptive hybrid numerical scheme on Cartesian structured grids is used, that combines a fifth-order WENO scheme near shocks and a sixth-order central-difference scheme away from shocks. The simulations target variations in the shock Mach number, M (from 1.5 to 3), turbulent Mach number, Mt (from 0.1 to 0.4, including wrinkled- and broken-shock regimes), and scalar Schmidt numbers, Sc (from 0.5 to 2), while keeping the Taylor microscale Reynolds number constant (Reλ 40). The effects on passive scalar statistics are investigated, including the streamwise evolution of scalar variance budgets, pdfs and spectra, in comparison with their temporal evolution in decaying isotropic turbulence.

Detonation onset following shock wave focusing

NASA Astrophysics Data System (ADS)

Smirnov, N. N.; Penyazkov, O. G.; Sevrouk, K. L.; Nikitin, V. F.; Stamov, L. I.; Tyurenkova, V. V.

2017-06-01

The aim of the present paper is to study detonation initiation due to focusing of a shock wave reflected inside a cone. Both numerical and experimental investigations were conducted. Comparison of results made it possible to validate the developed 3-d transient mathematical model of chemically reacting gas mixture flows incorporating hydrogen - air mixtures. The results of theoretical and numerical experiments made it possible improving kinetic schemes and turbulence models. Several different flow scenarios were detected in reflection of shock waves all being dependent on incident shock wave intensity: reflecting of shock wave with lagging behind combustion zone, formation of detonation wave in reflection and focusing, and intermediate transient regimes.

Biodamage via shock waves initiated by irradiation with ions.

PubMed

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

2013-01-01

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

Table and charts of equilibrium normal shock and shock tube properties for pure argon with velocities to 18 km/sec

NASA Technical Reports Server (NTRS)

Miller, C. G., III; Wilder, S. E.

1976-01-01

Equilibrium thermodynamic and flow properties are presented in tabulated and graphical form for moving, standing, and reflected normal shock waves in pure argon. Properties include pressure, temperature, density, enthalpy, speed of sound, entropy, molecular-weight ratio, isentropic exponent, velocity, and species mole fractions. Incident (moving) shock velocities are varied from 2 to 18 km/sec for a range of initial pressure of 5 N/sq m to 500 kN/sq m. Working charts illustrating shock tube performance with argon test gas and heated helium and hydrogen driver gases are also presented.

Impact, thermal, and shock sensitivity of molten TNT and of asphalt-contaminated molten TNT

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mainiero, R.J.; Miron, Y.; Kwak, S.S.W.

1996-12-01

The research reported here was part of an effort to evaluate the safety of a process to recover TNT from MK-9 depth bombs by the autoclave meltout process. In this process the depth bombs are heated to 121 C so that the TNT will melt and run into a vat. Unfortunately, asphalt lining the inside surface of the bomb also melts and flows out with the TNT. Testing was conducted on molten TNT and molten TNT contaminated with 2 pct asphalt at 90, 100, 110, 120, 125, and 130 C. In the liquid drop test apparatus with a 2-kg weight,more » the molten TNT yielded a 50 pct probability of initiation at a drop height of 6.5 cm at 110 C, decreasing to 4.5 cm at 130 C. Asphalt-contaminated TNT was somewhat less impact-sensitive than pure TNT at temperatures of 110 to 125 C, but became more sensitive at 130 C. There is a 50 pct probability of initiation at a drop height of 7.8 cm at 110 C, decreasing to 3.3 cm at 130 C. In the card gap test, the molten TNT detonated at high velocity for a gap of 0.25 inches at 90 to 125 C and detonated at high velocity for a gap of 0.5 inches at 130 C. For gaps of 0.5 to 3 inches at 90 to 125 C and 0.75 inches to 3 inches at 130 C, the TNT did not detonate at high velocity but produced a violent explosion that caused significant damage to the test fixture. The thermal analysis test results showed that when asphalt is present in TNT, it greatly accelerates the exothermic decomposition of TNT, starting at temperatures near 200 C. It appears that at relatively low shock stimulus levels, the molten TNT may be undergoing a low velocity detonation, wherein the shock wave traveling through the gap test pipe cavitates the molten TNT, greatly increasing its sensitivity. These results are crucial for assuring continued safety in recovering TNT from munitions through the autoclave meltout process.« less

Dynamic transition in the structure of an energetic crystal during chemical reactions at shock front prior to detonation.

PubMed

Nomura, Ken-Ichi; Kalia, Rajiv K; Nakano, Aiichiro; Vashishta, Priya; van Duin, Adri C T; Goddard, William A

2007-10-05

Mechanical stimuli in energetic materials initiate chemical reactions at shock fronts prior to detonation. Shock sensitivity measurements provide widely varying results, and quantum-mechanical calculations are unable to handle systems large enough to describe shock structure. Recent developments in reactive force-field molecular dynamics (ReaxFF-MD) combined with advances in parallel computing have paved the way to accurately simulate reaction pathways along with the structure of shock fronts. Our multimillion-atom ReaxFF-MD simulations of l,3,5-trinitro-l,3,5-triazine (RDX) reveal that detonation is preceded by a transition from a diffuse shock front with well-ordered molecular dipoles behind it to a disordered dipole distribution behind a sharp front.

Shock tube and shock wave research; Proceedings of the Eleventh International Symposium, University of Washington, Seattle, Wash., July 11-14, 1977

NASA Technical Reports Server (NTRS)

Ahlborn, B. (Editor); Hertzberg, A.; Russell, D.

1978-01-01

Papers are presented on the applications of shock-wave technology to the study of hydrodynamics, the use of the pressure-wave machine for charging diesel engines, and measurements of the heat-transfer rate in gas-turbine components. Consideration is given to shock propagation along 90-degree bends, the explosive dissemination of liquids, and rotational and vibrational relaxation behind weak shock waves in water vapor. Shock phenomena associated with expansion flows are described and stratospheric-related research using the shock tube is outlined. Attention is given to shock-wave ignition of magnesium powders, Mach reflection and boundary layers, and transition in the shock-induced unsteady boundary layer on a flat plate. Shock-tube measurements of induction and post-induction rates for low-Btu gas mixtures are presented and shock-initiated ignition in COS-N2O-Ar mixtures is described. Cluster growth rates in supersaturated lead vapor are presented and a study of laser-induced plasma motion in a solenoidal magnetic field is reviewed.

Shock wave attenuation by grids and orifice plates

NASA Astrophysics Data System (ADS)

Britan, A.; Igra, O.; Ben-Dor, G.; Shapiro, H.

2006-11-01

The interaction of weak shock waves with porous barriers of different geometries and porosities is examined. Installing a barrier inside the shock tube test section will cause the development of the following wave pattern upon a head-on collision between the incident shock wave and the barrier: a reflected shock from the barrier and a transmitted shock propagating towards the shock tube end wall. Once the transmitted shock wave reaches the end wall it is reflected back towards the barrier. This is the beginning of multiple reflections between the barrier and the end wall. This full cycle of shock reflections/interactions resulting from the incident shock wave collision with the barrier can be studied in a single shock tube test. A one-dimensional (1D), inviscid flow model was proposed for simulating the flow resulting from the initial collision of the incident shock wave with the barrier. Fairly good agreement is found between experimental findings and simulations based on a 1D flow model. Based on obtained numerical and experimental findings an optimal design procedure for shock wave attenuator is suggested. The suggested attenuator may ensure the safety of the shelter’s ventilation systems.

The Numerical Simulation of the Shock Wave of Coal Gas Explosions in Gas Pipe*

NASA Astrophysics Data System (ADS)

Chen, Zhenxing; Hou, Kepeng; Chen, Longwei

2018-03-01

For the problem of large deformation and vortex, the method of Euler and Lagrange has both advantage and disadvantage. In this paper we adopt special fuzzy interface method(volume of fluid). Gas satisfies the conditions of conservation equations of mass, momentum, and energy. Based on explosion and three-dimension fluid dynamics theory, using unsteady, compressible, inviscid hydrodynamic equations and state equations, this paper considers pressure gradient’s effects to velocity, mass and energy in Lagrange steps by the finite difference method. To minimize transport errors of material, energy and volume in Finite Difference mesh, it also considers material transport in Euler steps. Programmed with Fortran PowerStation 4.0 and visualized with the software designed independently, we design the numerical simulation of gas explosion with specific pipeline structure, check the key points of the pressure change in the flow field, reproduce the gas explosion in pipeline of shock wave propagation, from the initial development, flame and accelerate the process of shock wave. This offers beneficial reference and experience to coal gas explosion accidents or safety precautions.

Influence of initial conditions on the flow patterns of a shock-accelerated thin fluid layer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Budzinski, J.M.; Benjamin, R.F.; Jacobs, J.W.

1994-11-01

Previous observations of three flow patterns generated by shock acceleration of a thin perturbed, fluid layer are now correlated with asymmetries in the initial conditions. Using a different diagnostic (planar laser Rayleigh scattering) than the previous experiments, upstream mushrooms, downstream mushrooms, and sinuous patterns are still observed. For each experiment the initial perturbation amplitude on one side of the layer can either be larger, smaller, or the same as the amplitude on the other side, as observed with two images per experiment, and these differences lead to the formation of the different patterns.

Hot spot formation from shock reflections

NASA Astrophysics Data System (ADS)

Menikoff, R.

2011-04-01

Heterogeneities sensitize an explosive to shock initiation. This is due to hot-spot formation and the sensitivity of chemical reaction rates to temperature. Here, we describe a numerical experiment aimed at elucidating a mechanism for hot-spot formation that occurs when a shock wave passes over a high-density impurity. The simulation performed is motivated by a physical experiment in which glass beads are added to liquid nitromethane. The impedance mismatch between the beads and the nitromethane results in shock reflections. These, in turn, give rise to transverse waves along the lead shock front. Hot spots arise on local portions of the lead front with a higher shock strength, rather than on the reflected shocks behind the beads. Moreover, the interactions generated by reflected waves from neighboring beads can significantly increase the peak hot-spot temperature when the beads are suitably spaced.

Multiscale modeling of shock wave localization in porous energetic material

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wood, M. A.; Kittell, D. E.; Yarrington, C. D.

Shock wave interactions with defects, such as pores, are known to play a key role in the chemical initiation of energetic materials. The shock response of hexanitrostilbene is studied through a combination of large-scale reactive molecular dynamics and mesoscale hydrodynamic simulations. In order to extend our simulation capability at the mesoscale to include weak shock conditions (< 6 GPa), atomistic simulations of pore collapse are used here to define a strain-rate-dependent strength model. Comparing these simulation methods allows us to impose physically reasonable constraints on the mesoscale model parameters. In doing so, we have been able to study shock wavesmore » interacting with pores as a function of this viscoplastic material response. Finally, we find that the pore collapse behavior of weak shocks is characteristically different than that of strong shocks.« less

Multiscale modeling of shock wave localization in porous energetic material

DOE PAGES

Wood, M. A.; Kittell, D. E.; Yarrington, C. D.; ...

2018-01-30

Shock wave interactions with defects, such as pores, are known to play a key role in the chemical initiation of energetic materials. The shock response of hexanitrostilbene is studied through a combination of large-scale reactive molecular dynamics and mesoscale hydrodynamic simulations. In order to extend our simulation capability at the mesoscale to include weak shock conditions (< 6 GPa), atomistic simulations of pore collapse are used here to define a strain-rate-dependent strength model. Comparing these simulation methods allows us to impose physically reasonable constraints on the mesoscale model parameters. In doing so, we have been able to study shock wavesmore » interacting with pores as a function of this viscoplastic material response. Finally, we find that the pore collapse behavior of weak shocks is characteristically different than that of strong shocks.« less

Unusual locations of Earth's bow shock on September 24 - 25, 1987: Mach number effects

NASA Technical Reports Server (NTRS)

Cairns, Iver H.; Fairfield, Donald H.; Anderson, Oger R.; Carlton, Victoria E. H.; Paularena, Karolen I.; Lazarus, Alan J.

1995-01-01

International Sun Earth Explorer 1 (ISEE 1) and Interplanetary Monitoring Platform 8 (IMP 8) data are used to identify 19 crossings of Earth's bow shock during a 30-hour period following 0000 UT on September 24, 1987. Apparent standoff distances for the shock are calculated for each crossing using two methods and the spacecraft location; one method assumes the average shock shape, while the other assumes a ram pressure-dependent shock shape. The shock's apparent standoff distance, normally approximately 14 R(sub E), is shown to increase from near 10 R(sub E) initially to near 19 R(sub E) during an 8-hour period, followed by an excursion to near 35 R(sub E) (where two IMP 8 shock crossings occur) and an eventual return to values smaller than 19 R(sub E). The Alfven M(sub A) and fast magnetosonic M(sub ms). Mach numbers remain above 2 and the number density above 4/cu cm for almost the entire period. Ram pressure effects produce the initial near-Earth shock location, whereas expansions and contractions of the bow shock due to low Mach number effects account, qualitatively and semiquantitatively, for the timing and existence of almost all the remaining ISEE crossings and both IMP 8 crossings. Significant quantitative differences exist between the apparent standoff distances for the shock crossings and those predicted using the observed plasma parameters and the standard model based on Spreiter et al.'s (1966) gasdynamic equation. These differences can be explained in terms of either a different dependence of the standoff distance on Mach number at low M(sub A) and M(sub ms), or variations in shock shape with M(sub A) and M(sub ms) (becoming increasingly "puffed up" with decreasing M(sub A) and M(sub ms), as expected theoretically), or by a combination of both effects.

3-D Spontaneous Rupture Simulations of the 2016 Kumamoto, Japan, Earthquake

NASA Astrophysics Data System (ADS)

Urata, Yumi; Yoshida, Keisuke; Fukuyama, Eiichi

2017-04-01

We investigated the M7.3 Kumamoto, Japan, earthquake to illuminate why and how the rupture of the main shock propagated successfully by 3-D dynamic rupture simulations, assuming a complicated fault geometry estimated based on the distributions of aftershocks. The M7.3 main shock occurred along the Futagawa and Hinagu faults. A few days before, three M6-class foreshocks occurred. Their hypocenters were located along by the Hinagu and Futagawa faults and their focal mechanisms were similar to those of the main shock; therefore, an extensive stress shadow can have been generated on the fault plane of the main shock. First, we estimated the geometry of the fault planes of the three foreshocks as well as that of the main shock based on the temporal evolution of relocated aftershock hypocenters. Then, we evaluated static stress changes on the main shock fault plane due to the occurrence of the three foreshocks assuming elliptical cracks with constant stress drops on the estimated fault planes. The obtained static stress change distribution indicated that the hypocenter of the main shock is located on the region with positive Coulomb failure stress change (ΔCFS) while ΔCFS in the shallow region above the hypocenter was negative. Therefore, these foreshocks could encourage the initiation of the main shock rupture and could hinder the rupture propagating toward the shallow region. Finally, we conducted 3-D dynamic rupture simulations of the main shock using the initial stress distribution, which was the sum of the static stress changes by these foreshocks and the regional stress field. Assuming a slip-weakening law with uniform friction parameters, we conducted 3-D dynamic rupture simulations by varying the friction parameters and the values of the principal stresses. We obtained feasible parameter ranges to reproduce the rupture propagation of the main shock consistent with those revealed by seismic waveform analyses. We also demonstrated that the free surface encouraged the slip evolution of the main shock.

Autophagy activation protects shock wave induced renal tubular epithelial cell apoptosis may through modulation of Akt/ GSK-3β pathway.

PubMed

Long, Qingzhi; Li, Xiang; He, Hui; He, Dalin

2016-01-01

Extracorporeal shock wave lithotripsy (ESWL) is well documented to exert destructive effect to renal cells and its mechanism is not clear. Autophagy is one of cell basic response for stressful conditions and it is important to determine cell's fate. The aim of this study is to elucidate the role of autophagy in the process of shock wave-induced renal cells injury. NRK-52E cell, a rat renal tubular epithelial cell, was exposed to shock wave at the voltage of 14KV. GFP-LC3 puncta was used to monitor Autophagy flux in the process of shock wave injury. Autophagic relative proteins, such as light chain 3 (LC3), beclin-1 and p62, were also examined. Cell variability and apoptosis were detected when inhibition autophagy with 3-methyladenine (3MA) or stimulating its activity with rapamycin during the process of shock wave injury. The role of Akt/ GSK-3β and its connection with autophagy in the process of shock wave injury were also investigated. Shock wave was confirmed to activate autophagy in renal cells, which was manifested in LC3-II turnover, beclin-1 induction and degradation of p62. Inhibition autophagy enhanced cell damage or apoptosis, whereas its stimulating was able to exert protection from shock wave injury. Akt/ GSK-3β, a cell-survival signaling pathway, can also be activated during the process. And its activation could be suppressed by blockade autophagy. Autophagy is a self-protective response for renal cells from shock wave injury. The cyto-protection of autophagy may be connected with modulation Akt/ GSK-3β pathway.

Impact-generated winds on Venus: Causes and effects

NASA Technical Reports Server (NTRS)

Schultz, Pater H.

1992-01-01

The pressure of the dense atmosphere of Venus significantly changes the appearance of ejecta deposits relative to craters on the Moon and Mercury. Conversely, specific styles and sequences of ejecta emplacement can be inferred to represent different intensities of atmospheric response winds acting over different timescales. Three characteristic timescales can be inferred from the geologic record: surface scouring and impactor-controlled (angle and direction) initiation of the long fluidized run-out flows; nonballistic emplacement of inner, radar-bright ejecta facies and radar-dark outer facies; and very late reworking of surface materials. These three timescales roughly correspond to processes observed in laboratory experiments that can be scaled to conditions on Venus (with appropriate assumptions): coupling between the atmosphere and earlytime vapor/melt (target and impactor) that produces an intense shock that subsequently evolves into blast/response winds; less energetic dynamic response of the atmosphere to the outward-moving ballistic ejecta curtain that generates nonthermal turbulent eddies; and late recovery of the atmosphere to impact-generated thermal and pressure gradients expressed as low-energy but long-lived winds. These different timescales and processes can be viewed as the atmosphere equivalent of shock melting, material motion, and far-field seismic response in the target. The three processes (early Processes, Atmospheric Processes, and Late Recovery Winds) are discussed at length.

Ion Movements in Shock in Relation to Survival and Its Modifications

DTIC Science & Technology

1985-01-01

from normal to irreversibly injured are initiated and modified by primary and/or secondary effects of ion redistributions taking place between the...reactions to injury by the shock state has become possible. However, spcclflc aspects concerning effects at the cellular and subcellular levels need...to be further clarified. Therefore, the aim of this study was to characterize the cellular and subcellular effects of hemorrhagic and bacteremic shock

Effect of male accessory gland secretions on sensitivity of porcine sperm acrosomes to cold shock, initiation of motility and loss of cytoplasmic droplets.

PubMed

Berger, T; Clegg, E D

1985-05-01

Hyaluronidase release was used as an index of acrosomal membrane damage during cold shock of epididymal boar sperm and ejaculated sperm from intact and vesiculectomized boars. Sperm were also incubated with seminal plasma from intact and vasectomized boars to examine the contributions of male accessory gland secretions. Acrosomal membranes of epididymal sperm were more resistant to cold shock than those of ejaculated sperm. Only 36% of the hyaluronidase released by ejaculated sperm was released by the epididymal sperm in spite of similar hyaluronidase content of the sperm. Preincubation of epididymal sperm in seminal plasma from both intact and vasectomized boars increased resistance to cold shock by 60 to 80%. Initial dilution of epididymal sperm with seminal plasma, rather than Ringer-fructose buffer, was associated with low progressive motility and with retention of cytoplasmic droplets. In contrast, acrosomal membranes of ejaculated sperm from intact and vesiculectomized boars exhibited similar sensitivity to cold shock, releasing hyaluronidase capable of forming .20 and .19 mumol N-acetylglucosamine from hyaluronic acid/10(8) sperm in 8 min. Moreover, seminal plasma from vasectomized boars had no effect on acrosomal sensitivity to cold shock of ejaculated sperm from vesiculectomized boars.

Statistics of peak overpressure and shock steepness for linear and nonlinear N-wave propagation in a kinematic turbulence.

PubMed

Yuldashev, Petr V; Ollivier, Sébastien; Karzova, Maria M; Khokhlova, Vera A; Blanc-Benon, Philippe

2017-12-01

Linear and nonlinear propagation of high amplitude acoustic pulses through a turbulent layer in air is investigated using a two-dimensional KZK-type (Khokhlov-Zabolotskaya-Kuznetsov) equation. Initial waves are symmetrical N-waves with shock fronts of finite width. A modified von Kármán spectrum model is used to generate random wind velocity fluctuations associated with the turbulence. Physical parameters in simulations correspond to previous laboratory scale experiments where N-waves with 1.4 cm wavelength propagated through a turbulence layer with the outer scale of about 16 cm. Mean value and standard deviation of peak overpressure and shock steepness, as well as cumulative probabilities to observe amplified peak overpressure and shock steepness, are analyzed. Nonlinear propagation effects are shown to enhance pressure level in random foci for moderate initial amplitudes of N-waves thus increasing the probability to observe highly peaked waveforms. Saturation of the pressure level is observed for stronger nonlinear effects. It is shown that in the linear propagation regime, the turbulence mainly leads to the smearing of shock fronts, thus decreasing the probability to observe high values of steepness, whereas nonlinear effects dramatically increase the probability to observe steep shocks.

The shock sensitivity of nitromethane/methanol mixtures

NASA Astrophysics Data System (ADS)

Bartram, Brian; Dattelbaum, Dana; Sheffield, Steve; Gibson, Lee

2013-06-01

The dilution of liquid explosives has multiple effects on detonation properties including an increase in critical diameter, spatiotemporal lengthening of the chemical reaction zone, and the development of propagating wave instabilities. Earlier detonation studies of NM/methanol mixtures have shown several effects of increasing dilution, including: 1) a continual increase in the critical diameter, 2) lowering of the Chapman-Jouguet detonation pressure, and 3) slowing of the steady detonation velocity (Koldunov et al., Comb. Expl. Shock Waves). Here, we present the results of a series of gas gun-driven plate-impact experiments to study the shock-to-detonation transition in NM/methanol mixtures. Embedded electromagnetic gauges were used to obtain in situ particle velocity wave profiles at multiple Lagrangian positions in the initiating explosive mixture. From the wave profiles obtained in each experiment, an unreacted Hugoniot locus, the initiation mechanism, and the overtake-time-to-detonation were obtained as a function of shock input condition for mixture concentrations from 100% NM to 50 wt%/50 wt% NM/methanol. Desensitization with dilution is less than expected. For example, little change in overtake time occurs in 80 wt%/20 wt% NM/methanol when compared with neat NM. Furthermore, the shock wave profiles from the gauges indicate that wave instabilities grow in as the overdriven detonation wave settles down following the shock-to-detonation transition.

Single-interface Richtmyer-Meshkov turbulent mixing at the Los Alamos Vertical Shock Tube

DOE PAGES

Wilson, Brandon Merrill; Mejia Alvarez, Ricardo; Prestridge, Katherine Philomena

2016-04-12

We studied Mach number and initial conditions effects on Richtmyer–Meshkov (RM) mixing by the vertical shock tube (VST) at Los Alamos National Laboratory (LANL). At the VST, a perturbed stable light-to-heavy (air–SF 6, A=0.64) interface is impulsively accelerated with a shock wave to induce RM mixing. We investigate changes to both large and small scales of mixing caused by changing the incident Mach number (Ma=1.3 and 1.45) and the three-dimensional (3D) perturbations on the interface. Simultaneous density (quantitative planar laser-induced fluorescence (PLIF)) and velocity (particle image velocimetry (PIV)) measurements are used to characterize preshock initial conditions and the dynamic shockedmore » interface. Initial conditions and fluid properties are characterized before shock. Using two types of dynamic measurements, time series (N=5 realizations at ten locations) and statistics (N=100 realizations at a single location) of the density and velocity fields, we calculate several mixing quantities. Mix width, density-specific volume correlations, density–vorticity correlations, vorticity, enstrophy, strain, and instantaneous dissipation rate are examined at one downstream location. Results indicate that large-scale mixing, such as the mix width, is strongly dependent on Mach number, whereas small scales are strongly influenced by initial conditions. Lastly, the enstrophy and strain show focused mixing activity in the spike regions.« less

Non-radial instabilities and progenitor asphericities in core-collapse supernovae

NASA Astrophysics Data System (ADS)

Müller, B.; Janka, H.-Th.

2015-04-01

Since core-collapse supernova simulations still struggle to produce robust neutrino-driven explosions in 3D, it has been proposed that asphericities caused by convection in the progenitor might facilitate shock revival by boosting the activity of non-radial hydrodynamic instabilities in the post-shock region. We investigate this scenario in depth using 42 relativistic 2D simulations with multigroup neutrino transport to examine the effects of velocity and density perturbations in the progenitor for different perturbation geometries that obey fundamental physical constraints (like the anelastic condition). As a framework for analysing our results, we introduce semi-empirical scaling laws relating neutrino heating, average turbulent velocities in the gain region, and the shock deformation in the saturation limit of non-radial instabilities. The squared turbulent Mach number, , reflects the violence of aspherical motions in the gain layer, and explosive runaway occurs for ≳ 0.3, corresponding to a reduction of the critical neutrino luminosity by ˜ 25 per cent compared to 1D. In the light of this theory, progenitor asphericities aid shock revival mainly by creating anisotropic mass flux on to the shock: differential infall efficiently converts velocity perturbations in the progenitor into density perturbations δρ/ρ at the shock of the order of the initial convective Mach number Maprog. The anisotropic mass flux and ram pressure deform the shock and thereby amplify post-shock turbulence. Large-scale (ℓ = 2, ℓ = 1) modes prove most conducive to shock revival, whereas small-scale perturbations require unrealistically high convective Mach numbers. Initial density perturbations in the progenitor are only of the order of Ma_prog^2 and therefore play a subdominant role.

The Dynamic Quasiperpendicular Shock: Cluster Discoveries

NASA Astrophysics Data System (ADS)

Krasnoselskikh, V.; Balikhin, M.; Walker, S. N.; Schwartz, S.; Sundkvist, D.; Lobzin, V.; Gedalin, M.; Bale, S. D.; Mozer, F.; Soucek, J.; Hobara, Y.; Comisel, H.

The physics of collisionless shocks is a very broad topic which has been studied for more than five decades. However, there are a number of important issues which remain unresolved. The energy repartition amongst particle populations in quasiperpendicular shocks is a multi-scale process related to the spatial and temporal structure of the electromagnetic fields within the shock layer. The most important processes take place in the close vicinity of the major magnetic transition or ramp region. The distribution of electromagnetic fields in this region determines the characteristics of ion reflection and thus defines the conditions for ion heating and energy dissipation for supercritical shocks and also the region where an important part of electron heating takes place. In other words, the ramp region determines the main characteristics of energy repartition. All these processes are crucially dependent upon the characteristic spatial scales of the ramp and foot region provided that the shock is stationary. The process of shock formation consists of the steepening of a large amplitude nonlinear wave. At some point in its evolution the steepening is arrested by processes occurring within the shock transition. From the earliest studies of collisionless shocks these processes were identified as nonlinearity, dissipation, and dispersion. Their relative role determines the scales of electric and magnetic fields, and so control the characteristics of processes such as ion reflection, electron heating and particle acceleration. The determination of the scales of the electric and magnetic field is one of the key issues in the physics of collisionless shocks. Moreover, it is well known that under certain conditions shocks manifest a nonstationary dynamic behaviour called reformation. It was suggested that the transition from stationary to nonstationary quasiperiodic dynamics is related to gradients, e.g. scales of the ramp region and its associated whistler waves that form a precursor wave train. This implies that the ramp region should be considered as the source of these waves. All these questions have been studied making use observations from the Cluster satellites. The Cluster project continues to provide a unique viewpoint from which to study the scales of shocks. During its lifetime the inter-satellite distance between the Cluster satellites has varied from 100 km to 10000 km allowing scientists to use the data best adapted for the given scientific objective.

A new facility for studying shock-wave passage over dust layers

NASA Astrophysics Data System (ADS)

Chowdhury, A. Y.; Marks, B. D.; Johnston, H. Greg; Mannan, M. Sam; Petersen, E. L.

2016-03-01

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 shock tubes to understand shock-dust interactions. For this reason, a new shock-tube test section was developed and integrated into an existing shock-tube facility. The test section has large windows to allow for the use of the shadowgraph technique to track dust-layer growth behind a passing normal shock wave, and it is designed to handle an initial pressure of 1 atm with an incident shock 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-layer thickness. The design also allows for changing the experimental variables such as initial pressure, shock Mach number (Ms), dust-layer 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 layer thickness of 3.2 mm was subjected to Ms = 1.23, 1.32, and 1.6 shock waves, and dust-layer rise height was mapped with respect to time after shock passage. Dust particles subjected to a Ms = 1.6 shock wave rose more rapidly and to a greater height with respect to shock wave propagation than particles subjected to Ms = 1.23 and 1.32 shock waves. Although these results are in general agreement with the literature, the new data also highlight physical trends for dust-layer growth that have not been recorded previously, to the best of the authors' knowledge. For example, the dust-layer height rises linearly until a certain time where the growth rate is dramatically reduced, and in this second regime there is clear evidence of surface vertical structures at the dust-air interface.

Extremely Bright GRB 160625B with Multiple Emission Episodes: Evidence for Long-term Ejecta Evolution

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lü, Hou-Jun; Lü, Jing; Zhong, Shu-Qing

GRB 160625B is an extremely bright GRB with three distinct emission episodes. By analyzing its data observed with the Gamma-Ray Burst Monitor (GBM) and Large Area Telescope (LAT) on board the Fermi mission, we find that a multicolor blackbody (mBB) model can be used to fit very well the spectra of the initial short episode (Episode I) within the hypothesis of photosphere emission of a fireball model. The time-resolved spectra of its main episode (Episode II), which was detected with both GBM and LAT after a long quiescent stage (∼180 s) following the initial episode, can be fitted with amore » model comprising an mBB component plus a cutoff power-law (CPL) component. This GRB was detected again in the GBM and LAT bands with a long extended emission (Episode III) after a quiescent period of ∼300 s. The spectrum of Episode III is adequately fitted with CPL plus single power-law models, and no mBB component is required. These features may imply that the emission of the three episodes are dominated by distinct physics processes, i.e., Episode I is possible from the cocoon emission surrounding the relativistic jet, Episode II may be from photosphere emission and internal shock of the relativistic jet, and Episode III is contributed by internal and external shocks of the relativistic jet. On the other hand, both X-ray and optical afterglows are consistent with the standard external shocks model.« less

Extremely Bright GRB 160625B with Multiple Emission Episodes: Evidence for Long-term Ejecta Evolution

NASA Astrophysics Data System (ADS)

Lü, Hou-Jun; Lü, Jing; Zhong, Shu-Qing; Huang, Xiao-Li; Zhang, Hai-Ming; Lan, Lin; Xie, Wei; Lu, Rui-Jing; Liang, En-Wei

2017-11-01

GRB 160625B is an extremely bright GRB with three distinct emission episodes. By analyzing its data observed with the Gamma-Ray Burst Monitor (GBM) and Large Area Telescope (LAT) on board the Fermi mission, we find that a multicolor blackbody (mBB) model can be used to fit very well the spectra of the initial short episode (Episode I) within the hypothesis of photosphere emission of a fireball model. The time-resolved spectra of its main episode (Episode II), which was detected with both GBM and LAT after a long quiescent stage (˜180 s) following the initial episode, can be fitted with a model comprising an mBB component plus a cutoff power-law (CPL) component. This GRB was detected again in the GBM and LAT bands with a long extended emission (Episode III) after a quiescent period of ˜300 s. The spectrum of Episode III is adequately fitted with CPL plus single power-law models, and no mBB component is required. These features may imply that the emission of the three episodes are dominated by distinct physics processes, I.e., Episode I is possible from the cocoon emission surrounding the relativistic jet, Episode II may be from photosphere emission and internal shock of the relativistic jet, and Episode III is contributed by internal and external shocks of the relativistic jet. On the other hand, both X-ray and optical afterglows are consistent with the standard external shocks model.

The 2012 July 23 Backside Eruption: An Extreme Energetic Particle Event?

NASA Technical Reports Server (NTRS)

Gopalswamy, N.; Yashiro, S.; Thakur, N.; Makela, P.; Xie, H.; Akiyama, S.

2016-01-01

The backside coronal mass ejection (CME) of 2012 July 23 had a short Sun-to-Earth shock transit time (18.5 hr).The associated solar energetic particle (SEP) event had a greater than 10 MeV proton flux peaking at approximately 5000 pfu, and the energetic storm particle event was an order of magnitude larger, making it the most intense event in the space era at these energies. By a detailed analysis of the CME, shock, and SEP characteristics, we find that the July 23 event is consistent with a high-energy SEP event (accelerating particles to giga-electron volt energies). The times of maximum and fluence spectra in the range 10100 MeV were very hard, similar to those of ground-level enhancement (GLE) events. We found a hierarchical relationship between the CME initial speeds and the fluence spectral indices: CMEs with low initial speeds had SEP events with the softest spectra, while those with the highest initial speeds had SEP events with the hardest spectra. CMEs attaining intermediate speeds result in moderately hard spectra. The July 23 event was in the group of hard-spectrum events. During the July 23 event, the shock speed greater than (2000 km s(exp -1), the initial acceleration (approximately 1.70 km s(exp -2), and the shock-formation height (approximately 1.5 solar radii)were all typical of GLE events. The associated type II burst had emission components from meter to kilometer wavelengths, suggesting a strong shock. These observations confirm that the 2012 July 23 event is likely to be an extreme event in terms of the energetic particles it accelerated.

THE 2012 JULY 23 BACKSIDE ERUPTION: AN EXTREME ENERGETIC PARTICLE EVENT?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gopalswamy, N.; Yashiro, S.; Thakur, N.

The backside coronal mass ejection (CME) of 2012 July 23 had a short Sun-to-Earth shock transit time (18.5 hr). The associated solar energetic particle (SEP) event had a >10 MeV proton flux peaking at ∼5000 pfu, and the energetic storm particle event was an order of magnitude larger, making it the most intense event in the space era at these energies. By a detailed analysis of the CME, shock, and SEP characteristics, we find that the July 23 event is consistent with a high-energy SEP event (accelerating particles to gigaelectronvolt energies). The times of maximum and fluence spectra in the rangemore » 10–100 MeV were very hard, similar to those of ground-level enhancement (GLE) events. We found a hierarchical relationship between the CME initial speeds and the fluence spectral indices: CMEs with low initial speeds had SEP events with the softest spectra, while those with the highest initial speeds had SEP events with the hardest spectra. CMEs attaining intermediate speeds result in moderately hard spectra. The July 23 event was in the group of hard-spectrum events. During the July 23 event, the shock speed (>2000 km s{sup −1}), the initial acceleration (∼1.70 km s{sup −2}), and the shock-formation height (∼1.5 solar radii) were all typical of GLE events. The associated type II burst had emission components from meter to kilometer wavelengths, suggesting a strong shock. These observations confirm that the 2012 July 23 event is likely to be an extreme event in terms of the energetic particles it accelerated.« less

The effect of compressor-administered defibrillation on peri-shock pauses in a simulated cardiac arrest scenario.

PubMed

Glick, Joshua; Lehman, Erik; Terndrup, Thomas

2014-03-01

Coordination of the tasks of performing chest compressions and defibrillation can lead to communication challenges that may prolong time spent off the chest. The purpose of this study was to determine whether defibrillation provided by the provider performing chest compressions led to a decrease in peri-shock pauses as compared to defibrillation administered by a second provider, in a simulated cardiac arrest scenario. This was a randomized, controlled study measuring pauses in chest compressions for defibrillation in a simulated cardiac arrest model. We approached hospital providers with current CPR certification for participation between July, 2011 and October, 2011. Volunteers were randomized to control (facilitator-administered defibrillation) or experimental (compressor-administered defibrillation) groups. All participants completed one minute of chest compressions on a mannequin in a shockable rhythm prior to administration of defibrillation. We measured and compared pauses for defibrillation in both groups. Out of 200 total participants, we analyzed data from 197 defibrillations. Compressor-initiated defibrillation resulted in a significantly lower pre-shock hands-off time (0.57 s; 95% CI: 0.47-0.67) compared to facilitator-initiated defibrillation (1.49 s; 95% CI: 1.35-1.64). Furthermore, compressor-initiated defibrillation resulted in a significantly lower peri-shock hands-off time (2.77 s; 95% CI: 2.58-2.95) compared to facilitator-initiated defibrillation (4.25 s; 95% CI: 4.08-4.43). Assigning the responsibility for shock delivery to the provider performing compressions encourages continuous compressions throughout the charging period and decreases total time spent off the chest. However, as this was a simulation-based study, clinical implementation is necessary to further evaluate these potential benefits.

Observations on the normal reflection of gaseous detonations

NASA Astrophysics Data System (ADS)

Damazo, J.; Shepherd, J. E.

2017-09-01

Experimental results are presented examining the behavior of the shock wave created when a gaseous detonation wave normally impinges upon a planar wall. Gaseous detonations are created in a 7.67-m-long, 280-mm-internal-diameter detonation tube instrumented with a test section of rectangular cross section enabling visualization of the region at the tube-end farthest from the point of detonation initiation. Dynamic pressure measurements and high-speed schlieren photography in the region of detonation reflection are used to examine the characteristics of the inbound detonation wave and outbound reflected shock wave. Data from a range of detonable fuel/oxidizer/diluent/initial pressure combinations are presented to examine the effect of cell-size and detonation regularity on detonation reflection. The reflected shock does not bifurcate in any case examined and instead remains nominally planar when interacting with the boundary layer that is created behind the incident wave. The trajectory of the reflected shock wave is examined in detail, and the wave speed is found to rapidly change close to the end-wall, an effect we attribute to the interaction of the reflected shock with the reaction zone behind the incident detonation wave. Far from the end-wall, the reflected shock wave speed is in reasonable agreement with the ideal model of reflection which neglects the presence of a finite-length reaction zone. The net far-field effect of the reaction zone is to displace the reflected shock trajectory from the predictions of the ideal model, explaining the apparent disagreement of the ideal reflection model with experimental reflected shock observations of previous studies.

Three-dimensional Mesoscale Simulations of Detonation Initiation in Energetic Materials with Density-based Kinetics

NASA Astrophysics Data System (ADS)

Jackson, Thomas; Jost, A. M.; Zhang, Ju; Sridharan, P.; Amadio, G.

2017-06-01

In this work we present three-dimensional mesoscale simulations of detonation initiation in energetic materials. We solve the reactive Euler equations, with the energy equation augmented by a power deposition term. The reaction rate at the mesoscale is modelled using a density-based kinetics scheme, adapted from standard Ignition and Growth models. The deposition term is based on previous results of simulations of pore collapse at the microscale, modelled at the mesoscale as hot-spots. We carry out three-dimensional mesoscale simulations of random packs of HMX crystals in a binder, and show that the transition between no-detonation and detonation depends on the number density of the hot-spots, the initial radius of the hot-spot, the post-shock pressure of an imposed shock, and the amplitude of the power deposition term. The trends of transition at lower pressure of the imposed shock for larger number density of pore observed in experiments is reproduced. Initial attempts to improve the agreement between the simulation and experiments through calibration of various parameters will also be made.

Use of Disjunctive Response Requirements in Dual-Task Environments: Implications for Automation.

DTIC Science & Technology

1986-05-01

could be momentarily held in a short-term sensory buffer for later processing. Broadbent, postulating an early filter model , assumed the physical nature...explicative power of the early filter model , further dichotic listening experiments began to support, as a minimum, a late filter model . Deutsch and Deutsch... filter 63 model came from a study by Cortecn and Wood (1972). Initially, they conditioned a list of city names to electrical shock until the

Simulations of Converging Shock Collisions for Shock Ignition

NASA Astrophysics Data System (ADS)

Sauppe, Joshua; Dodd, Evan; Loomis, Eric

2016-10-01

Shock ignition (SI) has been proposed as an alternative to achieving high gain in inertial confinement fusion (ICF) targets. A central hot spot below the ignition threshold is created by an initial compression pulse, and a second laser pulse drives a strong converging shock into the fuel. The collision between the rebounding shock from the compression pulse and the converging shock results in amplification of the converging shock and increases the hot spot pressure above the ignition threshold. We investigate shock collision in SI drive schemes for cylindrical targets with a polystyrene foam interior using radiation-hydrodynamics simulations with the RAGE code. The configuration is similar to previous targets fielded on the Omega laser. The CH interior results in a lower convergence ratio and the cylindrical geometry facilitates visualization of the shock transit using an axial X-ray backlighter, both of which are important for comparison to potential experimental measurements. One-dimensional simulations are used to determine shock timing, and the effects of low mode asymmetries in 2D computations are also quantified. LA-UR-16-24773.

A Study of the Unstable Modes in High Mach Number Gaseous Jets and Shear Layers

NASA Astrophysics Data System (ADS)

Bassett, Gene Marcel

1993-01-01

Instabilities affecting the propagation of supersonic gaseous jets have been studied using high resolution computer simulations with the Piecewise-Parabolic-Method (PPM). These results are discussed in relation to jets from galactic nuclei. These studies involve a detailed treatment of a single section of a very long jet, approximating the dynamics by using periodic boundary conditions. Shear layer simulations have explored the effects of shear layers on the growth of nonlinear instabilities. Convergence of the numerical approximations has been tested by comparing jet simulations with different grid resolutions. The effects of initial conditions and geometry on the dominant disruptive instabilities have also been explored. Simulations of shear layers with a variety of thicknesses, Mach numbers and densities perturbed by incident sound waves imply that the time for the excited kink modes to grow large in amplitude and disrupt the shear layer is taug = (546 +/- 24) (M/4)^{1.7 } (Apert/0.02) ^{-0.4} delta/c, where M is the jet Mach number, delta is the half-width of the shear layer, and A_ {pert} is the perturbation amplitude. For simulations of periodic jets, the initial velocity perturbations set up zig-zag shock patterns inside the jet. In each case a single zig-zag shock pattern (an odd mode) or a double zig-zag shock pattern (an even mode) grows to dominate the flow. The dominant kink instability responsible for these shock patterns moves approximately at the linear resonance velocity, nu_ {mode} = cextnu_ {relative}/(cjet + c_ {ext}). For high resolution simulations (those with 150 or more computational zones across the jet width), the even mode dominates if the even penetration is higher in amplitude initially than the odd perturbation. For low resolution simulations, the odd mode dominates even for a stronger even mode perturbation. In high resolution simulations the jet boundary rolls up and large amounts of external gas are entrained into the jet. In low resolution simulations this entrainment process is impeded by numerical viscosity. The three-dimensional jet simulations behave similarly to two-dimensional jet runs with the same grid resolutions.

Shock wave propagation in a magnetic flux tube

NASA Astrophysics Data System (ADS)

Ferriz-Mas, A.; Moreno-Insertis, F.

1992-12-01

The propagation of a shock wave in a magnetic flux tube is studied within the framework of the Brinkley-Kirkwood theory adapted to a radiating gas. Simplified thermodynamic paths along which the compressed plasma returns to its initial state are considered. It is assumed that the undisturbed medium is uniform and that the flux tube is optically thin. The shock waves investigated, which are described with the aid of the thin flux-tube approximation, are essentially slow magnetohydrodynamic shocks modified by the constraint of lateral pressure balance between the flux tube and the surrounding field-free fluid; the confining external pressure must be balanced by the internal gas plus magnetic pressures. Exact analytical solutions giving the evolution of the shock wave are obtained for the case of weak shocks.

Double shock front formation in cylindrical radiative blast waves produced by laser irradiation of krypton gas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, I.; Quevedo, H. J.; Feldman, S.

2013-12-15

Radiative blast waves were created by irradiating a krypton cluster source from a supersonic jet with a high intensity femtosecond laser pulse. It was found that the radiation from the shock surface is absorbed in the optically thick upstream medium creating a radiative heat wave that travels supersonically ahead of the main shock. As the blast wave propagates into the heated medium, it slows and loses energy, and the radiative heat wave also slows down. When the radiative heat wave slows down to the transonic regime, a secondary shock in the ionization precursor is produced. This paper presents experimental datamore » characterizing both the initial and secondary shocks and numerical simulations to analyze the double-shock dynamics.« less

Table and charts of equilibrium normal-shock and shock-tube properties for pure carbon dioxide with velocities from 1 to 16 km/sec

NASA Technical Reports Server (NTRS)

Miller, C. G., III; Wilder, S. E.

1976-01-01

Equilibrium thermodynamic and flow properties are presented in tabulated and graphical form for moving, standing, and reflected normal shock waves in pure CO2. Properties include pressure, temperature, density, enthalpy, speed of sound, entropy, molecular weight ratio, isentropic exponent, velocity, and species mole fractions. Incident (moving) shock velocities are varied from 1 to 16 km/sec for a range of initial pressure of 5 N/sq m to 500 kN/sq m. The present results are applicable to shock tube flows and to freeflight conditions for a blunt body at high velocities. Working charts illustrating idealized shock tube performance with CO2 test gas and heated helium and hydrogen driver gases are also presented.

[Phaeochromocytoma as an unusual aetiology of cardiogenic shock].

PubMed

Ouchikhe, A; Lehoux, P; Gringore, A; Renouf, P; Deredec, R; Tasle, M; Massetti, M; Khayat, A; Saloux, E; Grollier, G; Samama, G; Gérard, J-L

2006-01-01

The authors reported a case involving a young patient with a cardiogenic shock associated to an acute pulmonary oedema. According to the seriousness of the shock, an external ventricular assist device (VAD) was initially inserted and replaced thereafter because of the cardiovascular instability, by an external pneumatic biventricular assist device. A cardiogenic shock induced by an acute adrenergic myocarditis due to a phaeochromocytoma was diagnosed. The patient was weaned from the VAD on day 84 and was scheduled for elective surgery of the phaeochromocytoma on day 93. The authors discussed the time of the surgery according to the anticoagulation therapy necessary to the VAD and the necessary caution taken if a cardiogenic shock appeared around surgery.

Particle response to shock waves in solids: dynamic witness plate/PIV method for detonations

NASA Astrophysics Data System (ADS)

Murphy, Michael J.; Adrian, Ronald J.

2007-08-01

Studies using transparent, polymeric witness plates consisting of polydimethlysiloxane (PDMS) have been conducted to measure the output of exploding bridge wire (EBW) detonators and exploding foil initiators (EFI). Polymeric witness plates are utilized to alleviate particle response issues that arise in gaseous flow fields containing shock waves and to allow measurements of shock-induced material velocities to be made using particle image velocimetry (PIV). Quantitative comparisons of velocity profiles across the shock waves in air and in PDMS demonstrate the improved response achieved by the dynamic witness plate method. Schlieren photographs complement the analysis through direct visualization of detonator-induced shock waves in the witness plates.

Annular arc accelerator shock tube

NASA Technical Reports Server (NTRS)

Leibowitz, L. P. (Inventor)

1976-01-01

An annular arc accelerator shock tube employs a cold gas driver to flow a stream of gas from an expansion section through a high voltage electrode section to a test section, thus driving a shock wave in front of it. A glow discharge detects the shock wave and actuates a trigger generator which in turn fires spark-gap switches to discharge a bank of capacitors across a centered cathode and an annular anode in tandem electrode sections. The initial shock wave passes through the anode section from the cathode section thereby depositing energy into the flow gas without the necessity of any diaphragm opening in the gas flow from the expansion section through the electrode sections.

Flow behind an exponential shock wave in a rotational axisymmetric perfect gas with magnetic field and variable density.

PubMed

Nath, G; Sahu, P K

2016-01-01

A self-similar model for one-dimensional unsteady isothermal and adiabatic flows behind a strong exponential shock wave driven out by a cylindrical piston moving with time according to an exponential law in an ideal gas in the presence of azimuthal magnetic field and variable density is discussed in a rotating atmosphere. The ambient medium is assumed to possess radial, axial and azimuthal component of fluid velocities. The initial density, the fluid velocities and magnetic field of the ambient medium are assumed to be varying with time according to an exponential law. The gas is taken to be non-viscous having infinite electrical conductivity. Solutions are obtained, in both the cases, when the flow between the shock and the piston is isothermal or adiabatic by taking into account the components of vorticity vector. The effects of the variation of the initial density index, adiabatic exponent of the gas and the Alfven-Mach number on the flow-field behind the shock wave are investigated. It is found that the presence of the magnetic field have decaying effects on the shock wave. Also, it is observed that the effect of an increase in the magnetic field strength is more impressive in the case of adiabatic flow than in the case of isothermal flow. The assumption of zero temperature gradient brings a profound change in the density, non-dimensional azimuthal and axial components of vorticity vector distributions in comparison to those in the case of adiabatic flow. A comparison is made between isothermal and adiabatic flows. It is obtained that an increase in the initial density variation index, adiabatic exponent and strength of the magnetic field decrease the shock strength.

Shock-induced termination of reentrant cardiac arrhythmias: Comparing monophasic and biphasic shock protocols

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bragard, Jean, E-mail: jbragard@unav.es; Simic, Ana; Elorza, Jorge

2013-12-15

In this article, we compare quantitatively the efficiency of three different protocols commonly used in commercial defibrillators. These are based on monophasic and both symmetric and asymmetric biphasic shocks. A numerical one–dimensional model of cardiac tissue using the bidomain formulation is used in order to test the different protocols. In particular, we performed a total of 4.8 × 10{sup 6} simulations by varying shock waveform, shock energy, initial conditions, and heterogeneity in internal electrical conductivity. Whenever the shock successfully removed the reentrant dynamics in the tissue, we classified the mechanism. The analysis of the numerical data shows that biphasic shocksmore » are significantly more efficient (by about 25%) than the corresponding monophasic ones. We determine that the increase in efficiency of the biphasic shocks can be explained by the higher proportion of newly excited tissue through the mechanism of direct activation.« less

On the role of covarying functions in stimulus class formation and transfer of function.

PubMed Central

Markham, Rebecca G; Markham, Michael R

2002-01-01

This experiment investigated whether directly trained covarying functions are necessary for stimulus class formation and transfer of function in humans. Initial class training was designed to establish two respondent-based stimulus classes by pairing two visual stimuli with shock and two other visual stimuli with no shock. Next, two operant discrimination functions were trained to one stimulus of each putative class. The no-shock group received the same training and testing in all phases, except no stimuli were ever paired with shock. The data indicated that skin conductance response conditioning did not occur for the shock groups or for the no-shock group. Tests showed transfer of the established discriminative functions, however, only for the shock groups, indicating the formation of two stimulus classes only for those participants who received respondent class training. The results suggest that transfer of function does not depend on first covarying the stimulus class functions. PMID:12507017

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

NASA Technical Reports Server (NTRS)

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

1976-01-01

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

Admission blood glucose predicted haemorrhagic shock in multiple trauma patients.

PubMed

Kreutziger, Janett; Rafetseder, Andreas; Mathis, Simon; Wenzel, Volker; El Attal, René; Schmid, Stefan

2015-01-01

Admission blood glucose is known to be a predictor for outcome in several disease patterns, especially in critically ill trauma patients. The underlying mechanisms for the association of hyperglycaemia and poor outcome are still not proven. It was hypothesised that hyperglycaemia upon hospital admission is associated with haemorrhagic shock and in-hospital mortality. Data was extracted from an observational trauma database of the level 1 trauma centre at Innsbruck Medical University hospital. Trauma patients (≥18 years) with multiple injuries and an Injury Severity Score ≥17 were included and analysed. In total, 279 patients were analysed, of which 42 patients (15.1%) died. With increasing blood glucose upon hospital admission, the rate of patients with haemorrhagic shock rose significantly [from 4.4% (glucose 4.1-5.5mmol/L) to 87.5% (glucose >15mmol/L), p<0.0001]. Mortality was also associated with initial blood glucose [≤5.50mmol/L 8.3%; 5.51-7.50mmol/L 10.9%, 7.51-10mmol/L 12.4%; 10.01-15mmol/L 32.0%; ≥15.01mmol/L 12.5%, p=0.008]. Admission blood glucose was a better indicator for haemorrhagic shock (cut-off 9.4mmol/L, sensitivity 67.1%, specificity 83.9%) than haemoglobin, base excess, bicarbonate, pH, lactate, or vital parameters. Regarding haemorrhagic shock, admission blood glucose is more valuable during initial patient assessment than the second best predictive parameter, which was admission haemoglobin (cut-off value 6.5mmol/L (10.4g/dL): sensitivity 61.3%, specificity 83.9%). In multiple trauma, non-diabetic patients, admission blood glucose predicted the incidence of haemorrhagic shock. Admission blood glucose is an inexpensive, rapidly and easily available laboratory value that might help to identify patients at risk for haemorrhagic shock during initial evaluation upon hospital admission. Copyright © 2014 Elsevier Ltd. All rights reserved.

Molecular processes in a high temperature shock layer

NASA Technical Reports Server (NTRS)

Guberman, S. L.

1984-01-01

Models of the shock layer encountered by an Aeroassisted Orbital Transfer Vehicle require as input accurate cross sections and rate constants for the atomic and molecular processes that characterize the shock radiation. From the estimated atomic and molecular densities in the shock layer and the expected residence time of 1 m/s, it can be expected that electron-ion collision processes will be important in the shock model. Electron capture by molecular ions followed by dissociation, e.g., O2(+) + e(-) yields 0 + 0, can be expected to be of major importance since these processes are known to have high rates (e.g., 10 to the -7th power cu/cm/sec) at room temperature. However, there have been no experimental measurements of dissociative recombination (DR) at temperatures ( 12000K) that are expected to characterize the shock layer. Indeed, even at room temperature, it is often difficult to perform experiments that determine the dependence of the translational energy and quantum yields of the product atoms on the electronic and vibrational state of the reactant molecular ions. Presented are ab initio quantum chemical studies of DR for molecular ions that are likely to be important in the atmospheric shock layer.

The Shock and Vibration Bulletin. Part 1. Welcome, Keynote Address, Invited Papers, Pyrotechnic Shock, and Shock Testing and Analysis

DTIC Science & Technology

1983-05-01

DESIGN PROCEDURE M. S. IIAndal, University of Vermont, Burlington, VT Machinery Dynamics ANALYTICAL AND EXPERIMENTAL INVESTIGATION OF ROTATING BLADE... methodology to accurately predict rotor vibratory loads and has recently been initiated for detail design and bench test- coupled rotor/airframe vibrations... design methodology , a trating on the basic disciplines of aerodynamics and struc. coupled rotor/airframe vibration analysis has been developed. tural

Post-Shock Sampling of Shock-Heated Hydrocarbon Fuels

DTIC Science & Technology

2016-07-07

on the ability to measure key hydrocarbon fragments (e.g. ethylene , methane, and acetylene) over a wide range of temperatures and pressures. The...series of experiments was conducted to validate the sampling system results and explore the thermal decomposition of ethylene and methane. Initially, a...1% ethylene /0.1% methane/balance argon fuel mixture was shock-heated to ~960 K – a temperature low enough that no reaction would occur. GC analysis

Simulation of transient flow in a shock tunnel and a high Mach number nozzle

NASA Technical Reports Server (NTRS)

Jacobs, P. A.

1991-01-01

A finite volume Navier-Stokes code was used to simulate the shock reflection and nozzle starting processes in an axisymmetric shock tube and a high Mach number nozzle. The simulated nozzle starting processes were found to match the classical quasi-1-D theory and some features of the experimental measurements. The shock reflection simulation illustrated a new mechanism for the driver gas contamination of the stagnated test gas.

The Physics of Molecular Shocks in Star-Forming Regions

NASA Technical Reports Server (NTRS)

Hollenbach, David; Cuzzi, Jeffrey (Technical Monitor)

1996-01-01

Molecular shocks are produced by the impact of the supersonic infall of gas and dust onto protostars and by the interaction of the supersonic outflow from the protostar with the circumstellar material. Infalling gas creates an accretion shock around the circumstellar disk which emits a unique infrared spectrum and which processes the interstellar dust as it enters the disk. The winds and jets from protostars also impact the disk, the infalling material, and the ambient molecular cloud core creating shocks whose spectrum and morphology diagnose the mass loss processes of the protostar and the orientation and structure of the star forming system. We discuss the physics of these shocks, the model spectra derived from theoretical models, and comparisons with observations of H2O masers, H2 emission, as well as other shocks tracers. We show the strong effect of magnetic fields on molecular shock structure, and elucidate the chemical changes induced by the shock heating and compression.

Shock Initiation of Thermally Expanded TATB

NASA Astrophysics Data System (ADS)

Mulford, Roberta; Swift, Damian

2011-06-01

The plastic-bonded explosive PBX-9502 undergoes unusual hysteretic thermal expansion, or ``ratchet growth'' as a consequence of the uniaxial thermal expansion of the graphitic structure of the major component, TATB explosive. Upon thermal cycling, the density of the material can be reduced by as much as 9%, resulting in a distinct increase in the shock sensitivity of the solid. Run distances to detonation have been measured in thermally expanded samples of PBX-9502, using embedded particle velocity gauges and shock tracker gauges. Uniaxial shocks were generated using a light gas gun, to provide a repeatable stimulus for initiation of detonation. We have applied a porosity model to adjust standard Pop plot data to the reduced density of our samples, to investigate whether the sensitivity of the PBX 9502 increases ideally with the decreasing density, or whether the microscopically non-uniform expansion that occurs during ``ratchet growth'' leads to abnormal sensitivity, possibly as a result of cracking or debonding from the binder, as observed in micrographs of the sample.

Amorphization and nanocrystallization of silcon under shock compression

DOE PAGES

Remington, B. A.; Wehrenberg, C. E.; Zhao, S.; ...

2015-11-06

High-power, short-duration, laser-driven, shock compression and recovery experiments on [001] silicon unveiled remarkable structural changes above a pressure threshold. Two distinct amorphous regions were identified: (a) a bulk amorphous layer close to the surface and (b) amorphous bands initially aligned with {111} slip planes. Further increase of the laser energy leads to the re-crystallization of amorphous silicon into nanocrystals with high concentration of nano-twins. This amorphization is produced by the combined effect of high magnitude hydrostatic and shear stresses under dynamic shock compression. Shock-induced defects play a very important role in the onset of amorphization. Calculations of the free energymore » changes with pressure and shear, using the Patel-Cohen methodology, are in agreement with the experimental results. Molecular dynamics simulation corroborates the amorphization, showing that it is initiated by the nucleation and propagation of partial dislocations. As a result, the nucleation of amorphization is analyzed qualitatively by classical nucleation theory.« less

Simultaneous measurements of concentration and velocity in the Richtmyer-Meshkov instability

NASA Astrophysics Data System (ADS)

Reese, Dan; Ames, Alex; Noble, Chris; Oakley, Jason; Rothamer, David; Bonazza, Riccardo

2017-11-01

The Richtmyer-Meshkov instability (RMI) is studied experimentally in the Wisconsin Shock Tube Laboratory (WiSTL) using a broadband, shear layer initial condition at the interface between a helium-acetone mixture and argon. This interface (Atwood number A=0.7) is accelerated by either a M=1.6 or M=2.2 planar shock wave, and the development of the RMI is investigated through simultaneous planar laser-induced fluorescence (PLIF) and particle image velocimetry (PIV) measurements at the initial condition and four post-shock times. Three Reynolds stresses, the planar turbulent kinetic energy, the Taylor microscale are calculated from the concentration and velocity fields. The external Reynolds number is estimated from the Taylor scale and the velocity statistics. The results suggest that the flow transitions to fully developed turbulence by the third post-shock time for the high Mach number case, while it may not at the lower Mach number. The authors would like to acknowledge the support of the Department of Energy.

Fingering patterns in Hele-Shaw flows are density shock wave solutions of dispersionless KdV hierarchy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Teodorescu, Razvan; Lee, S - Y; Wiegmann, P

We investigate the hydrodynamics of a Hele-Shaw flow as the free boundary evolves from smooth initial conditions into a generic cusp singularity (of local geometry type x{sup 3} {approx} y{sup 2}), and then into a density shock wave. This novel solution preserves the integrability of the dynamics and, unlike all the weak solutions proposed previously, is not underdetermined. The evolution of the shock is such that the net vorticity remains zero, as before the critical time, and the shock can be interpreted as a singular line distribution of fluid deficit.

3-D dynamic rupture simulations of the 2016 Kumamoto, Japan, earthquake

NASA Astrophysics Data System (ADS)

Urata, Yumi; Yoshida, Keisuke; Fukuyama, Eiichi; Kubo, Hisahiko

2017-11-01

Using 3-D dynamic rupture simulations, we investigated the 2016 Mw7.1 Kumamoto, Japan, earthquake to elucidate why and how the rupture of the main shock propagated successfully, assuming a complicated fault geometry estimated on the basis of the distributions of the aftershocks. The Mw7.1 main shock occurred along the Futagawa and Hinagu faults. Within 28 h before the main shock, three M6-class foreshocks occurred. Their hypocenters were located along the Hinagu and Futagawa faults, and their focal mechanisms were similar to that of the main shock. Therefore, an extensive stress shadow should have been generated on the fault plane of the main shock. First, we estimated the geometry of the fault planes of the three foreshocks as well as that of the main shock based on the temporal evolution of the relocated aftershock hypocenters. We then evaluated the static stress changes on the main shock fault plane that were due to the occurrence of the three foreshocks, assuming elliptical cracks with constant stress drops on the estimated fault planes. The obtained static stress change distribution indicated that Coulomb failure stress change (ΔCFS) was positive just below the hypocenter of the main shock, while the ΔCFS in the shallow region above the hypocenter was negative. Therefore, these foreshocks could encourage the initiation of the main shock rupture and could hinder the propagation of the rupture toward the shallow region. Finally, we conducted 3-D dynamic rupture simulations of the main shock using the initial stress distribution, which was the sum of the static stress changes caused by these foreshocks and the regional stress field. Assuming a slip-weakening law with uniform friction parameters, we computed 3-D dynamic rupture by varying the friction parameters and the values of the principal stresses. We obtained feasible parameter ranges that could reproduce the characteristic features of the main shock rupture revealed by seismic waveform analyses. We also observed that the free surface encouraged the slip evolution of the main shock.[Figure not available: see fulltext.

Time-resolved spectroscopic measurements of shock-wave induced decomposition in cyclotrimethylene trinitramine (RDX) crystals: anisotropic response.

PubMed

Dang, Nhan C; Dreger, Zbigniew A; Gupta, Yogendra M; Hooks, Daniel E

2010-11-04

Plate impact experiments on the (210), (100), and (111) planes were performed to examine the role of crystalline anisotropy on the shock-induced decomposition of cyclotrimethylenetrinitramine (RDX) crystals. Time-resolved emission spectroscopy was used to probe the decomposition of single crystals shocked to peak stresses ranging between 7 and 20 GPa. Emission produced by decomposition intermediates was analyzed in terms of induction time to emission, emission intensity, and the emission spectra shapes as a function of stress and time. Utilizing these features, we found that the shock-induced decomposition of RDX crystals exhibits considerable anisotropy. Crystals shocked on the (210) and (100) planes were more sensitive to decomposition than crystals shocked on the (111) plane. The possible sources of the observed anisotropy are discussed with regard to the inelastic deformation mechanisms of shocked RDX. Our results suggest that, despite the anisotropy observed for shock initiation, decomposition pathways for all three orientations are similar.

Development of a flyer design to perform plate impact shock-release-shock experiments on explosives

NASA Astrophysics Data System (ADS)

Finnegan, Simon; Ferguson, James; Millett, Jeremy; Goff, Michael

2017-06-01

A flyer design to generate a shock-release-shock loading history within a gas gun target was developed before being used to study the response of an HMX based explosive. The flyer consisted of two flyer plates separated by a vacuum gap. This created a rear free surface that, with correct material choice, allowed the target to release to close to ambient pressure between the initial shock and subsequent re-shock. The design was validated by impacting piezoelectric pin arrays to record the front flyer deformation. Shots were performed on PCTFE targets to record the shock states generated in an inert material prior to subjecting an HMX based explosive to the same loading. The response of the explosive to this loading history was recorded using magnetic particle velocity (PV) gauges embedded within the targets. The behavior during the run to detonation is compared with the response to sustained shocks at similar input pressures.

Shock Waves and Defects in Energetic Materials, a Match Made in MD Heaven

NASA Astrophysics Data System (ADS)

Wood, Mitchell; Kittell, David; Yarrington, Cole; Thompson, Aidan

2017-06-01

Shock wave interactions with defects, such as pores, are known to play a key role in the chemical initiation of energetic materials. In this talk the shock response of Hexanitrostilbene (HNS) is studied through large scale reactive molecular dynamics (RMD) simulations. These RMD simulations provide a unique opportunity to elucidate mechanisms of viscoplastic pore collapse which are often neglected in larger scale hydrodynamic models. A discussion of the macroscopic effects of this viscoplastic material response, such as its role in hot spot formation and eventual initiation, will be provided. Through this work we have been able to map a transition from purely viscoplastic to fluid-like pore collapse that is a function of shock strength, pore size and material strength. In addition, these findings are important reference data for the validation of future multi-scale modeling efforts of the shock response of heterogeneous materials. Examples of how these RMD results are translated into mesoscale models will also be addressed. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the US DOE NNSA under Contract No. DE- AC04-94AL85000.

Shock front distortion and Richtmyer-Meshkov-type growth caused by a small preshock nonuniformity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Velikovich, A. L.; Wouchuk, J. G.; Huete Ruiz de Lira, C.

The response of a shock front to small preshock nonuniformities of density, pressure, and velocity is studied theoretically and numerically. These preshock nonuniformities emulate imperfections of a laser target, due either to its manufacturing, like joints or feeding tubes, or to preshock perturbation seeding/growth, as well as density fluctuations in foam targets, ''thermal layers'' near heated surfaces, etc. Similarly to the shock-wave interaction with a small nonuniformity localized at a material interface, which triggers a classical Richtmyer-Meshkov (RM) instability, interaction of a shock wave with periodic or localized preshock perturbations distributed in the volume distorts the shape of the shockmore » front and can cause a RM-type instability growth. Explicit asymptotic formulas describing distortion of the shock front and the rate of RM-type growth are presented. These formulas are favorably compared both to the exact solutions of the corresponding initial-boundary-value problem and to numerical simulations. It is demonstrated that a small density modulation localized sufficiently close to a flat target surface produces the same perturbation growth as an 'equivalent' ripple on the surface of a uniform target, characterized by the same initial areal mass modulation amplitude.« less

Examining the effects of microstructure and loading on the shock initiation of HMX with mesoscale simulations

NASA Astrophysics Data System (ADS)

Springer, H. Keo; Tarver, Craig; Bastea, Sorin

2015-06-01

We perform reactive mesoscale simulations to study shock initiation in HMX over a range of pore morphologies and sizes, porosities, and loading conditions in order to improve our understanding of structure-performance relationships. These relationships are important because they guide the development of advanced macroscale models incorporating hot spot mechanisms and the optimization of novel energetic material microstructures. Mesoscale simulations are performed using the multiphysics hydrocode, ALE3D. Spherical, elliptical, polygonal, and crack-like pore geometries 0.1, 1, 10, and 100 microns in size and 2, 5, 10, and 14% porosity are explored. Loading conditions are realized with shock pressures of 6, 10, 20, 38, and 50 GPa. A Cheetah-based tabular model, including temperature-dependent heat capacity, is used for the unreacted and the product equation-of-state. Also, in-line Cheetah is used to probe chemical species evolution. The influence of microstructure and shock loading on shock-to-detonation-transition run distance, reaction rate and product gas species evolution are discussed. This work performed under the auspices of the U.S. DOE by LLNL under Contract DE-AC52-07NA27344. This work is funded by the Joint DoD-DOE Munitions Program.

Effects of viscosity on shock-induced damping of an initial sinusoidal disturbance

NASA Astrophysics Data System (ADS)

Ma, Xiaojuan; Liu, Fusheng; Jing, Fuqian

2010-05-01

A lack of reliable data treatment method has been for several decades the bottleneck of viscosity measurement by disturbance amplitude damping method of shock waves. In this work the finite difference method is firstly applied to obtain the numerical solutions for disturbance amplitude damping behavior of sinusoidal shock front in inviscid and viscous flow. When water shocked to 15 GPa is taken as an example, the main results are as follows: (1) For inviscid and lower viscous flows the numerical method gives results in good agreement with the analytic solutions under the condition of small disturbance ( a 0/ λ=0.02); (2) For the flow of viscosity beyond 200 Pa s ( η = κ) the analytic solution is found to overestimate obviously the effects of viscosity. It is attributed to the unreal pre-conditions of analytic solution by Miller and Ahrens; (3) The present numerical method provides an effective tool with more confidence to overcome the bottleneck of data treatment when the effects of higher viscosity in experiments of Sakharov and flyer impact are expected to be analyzed, because it can in principle simulate the development of shock waves in flows with larger disturbance amplitude, higher viscosity, and complicated initial flow.

Extended asymmetric hot region formation due to shockwave interactions following void collapse in shocked high explosive

NASA Astrophysics Data System (ADS)

Shan, Tzu-Ray; Wixom, Ryan R.; Thompson, Aidan P.

2016-08-01

In both continuum hydrodynamics simulations and also multimillion atom reactive molecular dynamics simulations of shockwave propagation in single crystal pentaerythritol tetranitrate (PETN) containing a cylindrical void, we observed the formation of an initial radially symmetric hot spot. By extending the simulation time to the nanosecond scale, however, we observed the transformation of the small symmetric hot spot into a longitudinally asymmetric hot region extending over a much larger volume. Performing reactive molecular dynamics shock simulations using the reactive force field (ReaxFF) as implemented in the LAMMPS molecular dynamics package, we showed that the longitudinally asymmetric hot region was formed by coalescence of the primary radially symmetric hot spot with a secondary triangular hot zone. We showed that the triangular hot zone coincided with a double-shocked region where the primary planar shockwave was overtaken by a secondary cylindrical shockwave. The secondary cylindrical shockwave originated in void collapse after the primary planar shockwave had passed over the void. A similar phenomenon was observed in continuum hydrodynamics shock simulations using the CTH hydrodynamics package. The formation and growth of extended asymmetric hot regions on nanosecond timescales has important implications for shock initiation thresholds in energetic materials.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stevens, D.L.; Simonen, F.A.; Strosnider, J. Jr.

The VISA (Vessel Integrity Simulation Analysis) code was developed as part of the NRC staff evaluation of pressurized thermal shock. VISA uses Monte Carlo simulation to evaluate the failure probability of a pressurized water reactor (PWR) pressure vessel subjected to a pressure and thermal transient specified by the user. Linear elastic fracture mechanics are used to model crack initiation and propagation. parameters for initial crack size, copper content, initial RT/sub NDT/, fluence, crack-initiation fracture toughness, and arrest fracture toughness are treated as random variables. This report documents the version of VISA used in the NRC staff report (Policy Issue frommore » J.W. Dircks to NRC Commissioners, Enclosure A: NRC Staff Evaluation of Pressurized Thermal Shock, November 1982, SECY-82-465) and includes a user's guide for the code.« less

The Dynamics of Very High Alfvén Mach Number Shocks in Space Plasmas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sundberg, Torbjörn; Burgess, David; Scholer, Manfred

2017-02-10

Astrophysical shocks, such as planetary bow shocks or supernova remnant shocks, are often in the high or very-high Mach number regime, and the structure of such shocks is crucial for understanding particle acceleration and plasma heating, as well inherently interesting. Recent magnetic field observations at Saturn’s bow shock, for Alfvén Mach numbers greater than about 25, have provided evidence for periodic non-stationarity, although the details of the ion- and electron-scale processes remain unclear due to limited plasma data. High-resolution, multi-spacecraft data are available for the terrestrial bow shock, but here the very high Mach number regime is only attained onmore » extremely rare occasions. Here we present magnetic field and particle data from three such quasi-perpendicular shock crossings observed by the four-spacecraft Cluster mission. Although both ion reflection and the shock profile are modulated at the upstream ion gyroperiod timescale, the dominant wave growth in the foot takes place at sub-proton length scales and is consistent with being driven by the ion Weibel instability. The observed large-scale behavior depends strongly on cross-scale coupling between ion and electron processes, with ion reflection never fully suppressed, and this suggests a model of the shock dynamics that is in conflict with previous models of non-stationarity. Thus, the observations offer insight into the conditions prevalent in many inaccessible astrophysical environments, and provide important constraints for acceleration processes at such shocks.« less

The Dynamics of Very High Alfvén Mach Number Shocks in Space Plasmas

NASA Astrophysics Data System (ADS)

Sundberg, Torbjörn; Burgess, David; Scholer, Manfred; Masters, Adam; Sulaiman, Ali H.

2017-02-01

Astrophysical shocks, such as planetary bow shocks or supernova remnant shocks, are often in the high or very-high Mach number regime, and the structure of such shocks is crucial for understanding particle acceleration and plasma heating, as well inherently interesting. Recent magnetic field observations at Saturn’s bow shock, for Alfvén Mach numbers greater than about 25, have provided evidence for periodic non-stationarity, although the details of the ion- and electron-scale processes remain unclear due to limited plasma data. High-resolution, multi-spacecraft data are available for the terrestrial bow shock, but here the very high Mach number regime is only attained on extremely rare occasions. Here we present magnetic field and particle data from three such quasi-perpendicular shock crossings observed by the four-spacecraft Cluster mission. Although both ion reflection and the shock profile are modulated at the upstream ion gyroperiod timescale, the dominant wave growth in the foot takes place at sub-proton length scales and is consistent with being driven by the ion Weibel instability. The observed large-scale behavior depends strongly on cross-scale coupling between ion and electron processes, with ion reflection never fully suppressed, and this suggests a model of the shock dynamics that is in conflict with previous models of non-stationarity. Thus, the observations offer insight into the conditions prevalent in many inaccessible astrophysical environments, and provide important constraints for acceleration processes at such shocks.

Laser shock wave and its applications

NASA Astrophysics Data System (ADS)

Yang, Chaojun; Zhang, Yongkang; Zhou, Jianzhong; Zhang, Fang; Feng, Aixin

2007-12-01

The technology of laser shock wave is used to not only surface modification but also metal forming. It can be divided into three parts: laser shock processing, laser shock forming (LSF) and laser peenforming(LPF). Laser shock processing as a surface treatment to metals can make engineering components have a residual compressive stress so that it obviously improves their fatigue strength and stress corrosion performances, while laser shock forming (LSF) is a novel technique that is used in plastic deformation of sheet metal recently and Laser peen forming (LPF) is another new sheet metal forming process presented in recent years. They all can be carried out by a high-power and repetition pulse Nd:Glass laser device made by Jiangsu University. Laser shock technology has characterized of ultrahigh pressure and high strain rate (10 6 - 10 7s -1). Now, for different materials, we are able to form different metals to contours and shapes and simultaneity leave their surfaces in crack-resistant compressive stress state. The results show that the technology of laser shock wave can strengthen surface property and prolong fatigue life and especially can deform metals to shapes that could not be adequately made using conventional methods. With the development of the technology of laser shock wave, the applied fields of laser will become greater and greater.

Effects of Stone Size on the Comminution Process and Efficiency in Shock Wave Lithotripsy

PubMed Central

Zhang, Ying; Nault, Isaac; Mitran, Sorin; Iversen, Edwin S.; Zhong, Pei

2016-01-01

The effects of stone size on the process and comminution efficiency in shock wave lithotripsy (SWL) are investigated by experiments, numerical simulations, and scale analysis. Cylindrical BegoStone phantoms with approximately equal height and diameter of either 4-, or 7- or 10-mm, in a total aggregated mass of about 1.5 g, were treated in an electromagnetic shock wave lithotripter field. The resultant stone comminution (SC) was found to correlate closely with the average peak pressure, P+(avg), incident on the stones. The P+(avg) threshold to initiate stone fragmentation in water increased from 7.9 to 8.8 to 12.7 MPa, respectively, when the stone size decreased from 10 to 7 to 4 mm. Similar changes in the P+(avg) threshold were observed for the 7- and 10-mm stones treated in 1,3-butanediol where cavitation is suppressed, suggesting that the observed size dependency is due to changes in stress distribution within different size stones. Moreover, the slope of the correlation curve between SC and ln(P‒+(avg)) in water increased with decreasing stone size, while the opposite trend was observed in 1,3-butanediol. The progression of stone comminution in SWL showed a size-dependency with the 7- and 10-mm stones fragmented into progressively smaller pieces while a significant portion (> 30%) of the 4-mm stones were stalemated within the size range of 2.8 ~ 4 mm even after 1,000 shocks. Analytical scaling considerations suggest size-dependent fragmentation behaviour, a hypothesis further supported by numerical model calculations that exhibit changing patterns of constructive and destructive wave interference, and thus variations in the maximum tensile stress or stress integral produced in cylindrical and spherical stone of different sizes. PMID:27515177

Chondrules born in plasma? Simulation of gas-grain interaction using plasma arcs with applications to chondrule and cosmic spherule formation

NASA Astrophysics Data System (ADS)

Morlok, A.; Sutton, Y. C.; Braithwaite, N. St. J.; Grady, Monica M.

2012-12-01