An object-oriented and quadrilateral-mesh based solution adaptive algorithm for compressible multi-fluid flows

NASA Astrophysics Data System (ADS)

Zheng, H. W.; Shu, C.; Chew, Y. T.

2008-07-01

In this paper, an object-oriented and quadrilateral-mesh based solution adaptive algorithm for the simulation of compressible multi-fluid flows is presented. The HLLC scheme (Harten, Lax and van Leer approximate Riemann solver with the Contact wave restored) is extended to adaptively solve the compressible multi-fluid flows under complex geometry on unstructured mesh. It is also extended to the second-order of accuracy by using MUSCL extrapolation. The node, edge and cell are arranged in such an object-oriented manner that each of them inherits from a basic object. A home-made double link list is designed to manage these objects so that the inserting of new objects and removing of the existing objects (nodes, edges and cells) are independent of the number of objects and only of the complexity of O( 1). In addition, the cells with different levels are further stored in different lists. This avoids the recursive calculation of solution of mother (non-leaf) cells. Thus, high efficiency is obtained due to these features. Besides, as compared to other cell-edge adaptive methods, the separation of nodes would reduce the memory requirement of redundant nodes, especially in the cases where the level number is large or the space dimension is three. Five two-dimensional examples are used to examine its performance. These examples include vortex evolution problem, interface only problem under structured mesh and unstructured mesh, bubble explosion under the water, bubble-shock interaction, and shock-interface interaction inside the cylindrical vessel. Numerical results indicate that there is no oscillation of pressure and velocity across the interface and it is feasible to apply it to solve compressible multi-fluid flows with large density ratio (1000) and strong shock wave (the pressure ratio is 10,000) interaction with the interface.

Quasi-isentropic compression using compressed water flow generated by underwater electrical explosion of a wire array

NASA Astrophysics Data System (ADS)

Gurovich, V.; Virozub, A.; Rososhek, A.; Bland, S.; Spielman, R. B.; Krasik, Ya. E.

2018-05-01

A major experimental research area in material equation-of-state today involves the use of off-Hugoniot measurements rather than shock experiments that give only Hugoniot data. There is a wide range of applications using quasi-isentropic compression of matter including the direct measurement of the complete isentrope of materials in a single experiment and minimizing the heating of flyer plates for high-velocity shock measurements. We propose a novel approach to generating quasi-isentropic compression of matter. Using analytical modeling and hydrodynamic simulations, we show that a working fluid composed of compressed water, generated by an underwater electrical explosion of a planar wire array, might be used to efficiently drive the quasi-isentropic compression of a copper target to pressures ˜2 × 1011 Pa without any complex target designs.

Nonlinear waves and shocks in relativistic two-fluid hydrodynamics

NASA Astrophysics Data System (ADS)

Haim, L.; Gedalin, M.; Spitkovsky, A.; Krasnoselskikh, V.; Balikhin, M.

2012-06-01

Relativistic shocks are present in a number of objects where violent processes are accompanied by relativistic outflows of plasma. The magnetization parameter σ = B2/4πnmc2 of the ambient medium varies in wide range. Shocks with low σ are expected to substantially enhance the magnetic fields in the shock front. In non-relativistic shocks the magnetic compression is limited by nonlinear effects related to the deceleration of flow. Two-fluid analysis of perpendicular relativistic shocks shows that the nonlinearities are suppressed for σ<<1 and the magnetic field reaches nearly equipartition values when the magnetic energy density is of the order of the ion energy density, Beq2 ~ 4πnmic2γ. A large cross-shock potential eφ/mic2γ0 ~ B2/Beq2 develops across the electron-ion shock front. This potential is responsible for electron energization.

ELECTROMAGNETISM, OPTICS, ACOUSTICS, HEAT TRANSFER, CLASSICAL MECHANICS, AND FLUID DYNAMICS: Highly Efficient Lattice Boltzmann Model for Compressible Fluids: Two-Dimensional Case

NASA Astrophysics Data System (ADS)

Chen, Feng; Xu, Ai-Guo; Zhang, Guang-Cai; Gan, Yan-Biao; Cheng, Tao; Li, Ying-Jun

2009-10-01

We present a highly efficient lattice Boltzmann model for simulating compressible flows. This model is based on the combination of an appropriate finite difference scheme, a 16-discrete-velocity model [Kataoka and Tsutahara, Phys. Rev. E 69 (2004) 035701(R)] and reasonable dispersion and dissipation terms. The dispersion term effectively reduces the oscillation at the discontinuity and enhances numerical precision. The dissipation term makes the new model more easily meet with the von Neumann stability condition. This model works for both high-speed and low-speed flows with arbitrary specific-heat-ratio. With the new model simulation results for the well-known benchmark problems get a high accuracy compared with the analytic or experimental ones. The used benchmark tests include (i) Shock tubes such as the Sod, Lax, Sjogreen, Colella explosion wave, and collision of two strong shocks, (ii) Regular and Mach shock reflections, and (iii) Shock wave reaction on cylindrical bubble problems. With a more realistic equation of state or free-energy functional, the new model has the potential tostudy the complex procedure of shock wave reaction on porous materials.

Non-Ideal Compressible Fluid Dynamics: A Challenge for Theory

NASA Astrophysics Data System (ADS)

Kluwick, A.

2017-03-01

The possibility that compression as well as rarefaction shocks may form in single phase vapours was envisaged first by Bethe (1942). However calculations based on the Van der Waals equation of state indicated that the latter type of shock is possible only if the specific heat at constant volume cv divided by the universal gas constant R is larger than about 17.5 which he considered too large to be satisfied by real fluids. This conclusion was contested by Thompson (1971) who showed that the type of shock capable of forming in arbitrary fluids is determined by the sign of the thermodynamic quantity to which he referred to as fundamental derivative of gas dynamics. Here v, p, s and c denote the specific volume, the pressure, the entropy and the speed of sound. Thompson and co-workers also showed that the required condition for the existence of rarefaction shocks, that Γ may take on negative values, is indeed satisfied for a number of hydrocarbon and fluorocarbon vapours. This finding spawned a burst of theoretical studies elaborating on the unusual and often counterintuitive behaviour of shocks with rarefaction shocks present. These produced both results of theoretical character but also results suggesting the practical importance of Non-Ideal Compressible Fluid Dynamics in general. The present paper addresses some of the challenges encountered in connection with the theoretical treatment of the associated flow behaviour. Weakly nonlinear acoustic waves of finite amplitude serve as a starting point. Here mixed rather than strictly positive nonlinearity generates a wealth of phenomena not possible in perfect gases. Examples of steady flows where these non-classical effects play a decisive role (and which may be useful also for future experimental work) are quasi one-dimensional nozzle flows and transonic two-dimensional flows past corners. The study of viscous effects concentrates on laminar flows of boundary layer type. Here non-classical phenomena are caused by the uncommon smallness of the Eckert number but also by the unconventional Mach number dependence on p in the external inviscid flow region.

An immersed boundary method for fluid-structure interaction with compressible multiphase flows

NASA Astrophysics Data System (ADS)

Wang, Li; Currao, Gaetano M. D.; Han, Feng; Neely, Andrew J.; Young, John; Tian, Fang-Bao

2017-10-01

This paper presents a two-dimensional immersed boundary method for fluid-structure interaction with compressible multiphase flows involving large structure deformations. This method involves three important parts: flow solver, structure solver and fluid-structure interaction coupling. In the flow solver, the compressible multiphase Navier-Stokes equations for ideal gases are solved by a finite difference method based on a staggered Cartesian mesh, where a fifth-order accuracy Weighted Essentially Non-Oscillation (WENO) scheme is used to handle spatial discretization of the convective term, a fourth-order central difference scheme is employed to discretize the viscous term, the third-order TVD Runge-Kutta scheme is used to discretize the temporal term, and the level-set method is adopted to capture the multi-material interface. In this work, the structure considered is a geometrically non-linear beam which is solved by using a finite element method based on the absolute nodal coordinate formulation (ANCF). The fluid dynamics and the structure motion are coupled in a partitioned iterative manner with a feedback penalty immersed boundary method where the flow dynamics is defined on a fixed Lagrangian grid and the structure dynamics is described on a global coordinate. We perform several validation cases (including fluid over a cylinder, structure dynamics, flow induced vibration of a flexible plate, deformation of a flexible panel induced by shock waves in a shock tube, an inclined flexible plate in a hypersonic flow, and shock-induced collapse of a cylindrical helium cavity in the air), and compare the results with experimental and other numerical data. The present results agree well with the published data and the current experiment. Finally, we further demonstrate the versatility of the present method by applying it to a flexible plate interacting with multiphase flows.

Interactive computer graphics applications for compressible aerodynamics

NASA Technical Reports Server (NTRS)

Benson, Thomas J.

1994-01-01

Three computer applications have been developed to solve inviscid compressible fluids problems using interactive computer graphics. The first application is a compressible flow calculator which solves for isentropic flow, normal shocks, and oblique shocks or centered expansions produced by two dimensional ramps. The second application couples the solutions generated by the first application to a more graphical presentation of the results to produce a desk top simulator of three compressible flow problems: 1) flow past a single compression ramp; 2) flow past two ramps in series; and 3) flow past two opposed ramps. The third application extends the results of the second to produce a design tool which solves for the flow through supersonic external or mixed compression inlets. The applications were originally developed to run on SGI or IBM workstations running GL graphics. They are currently being extended to solve additional types of flow problems and modified to operate on any X-based workstation.

Shear Viscosity of Aluminium under Shock Compression

NASA Astrophysics Data System (ADS)

Liu, Fu-Sheng; Yang, Mei-Xia; Liu, Qi-Wen; Chen, Jun-Xiang; Jing, Fu-Qian

2005-03-01

Based on the Newtonian viscous fluid model and the analytic perturbation theory of Miller and Ahrens for the oscillatory damping of a sinusoidal shock front, a flyer-impact technique is developed to investigate the effective viscosity of shocked aluminium. The shear viscosity coefficient is determined to be about 5000 poises at 42 GPa with strain rate of 1.27×106 s-1, which is a reasonable estimation compared with the results of other measurement methods.

Finite element computation of compressible flows with the SUPG formulation

NASA Technical Reports Server (NTRS)

Le Beau, G. J.; Tezduyar, T. E.

1991-01-01

Finite element computation of compressible Euler equations is presented in the context of the streamline-upwind/Petrov-Galerkin (SUPG) formulation. The SUPG formulation, which is based on adding stabilizing terms to the Galerkin formulation, is further supplemented with a shock capturing operator which addresses the difficulty in maintaining a satisfactory solution near discontinuities in the solution field. The shock capturing operator, which has been derived from work done in entropy variables for a similar operator, is shown to lead to an appropriate level of additional stabilization near shocks, without resulting in excessive numerical diffusion. An implicit treatment of the impermeable wall boundary condition is also presented. This treatment of the no-penetration condition offers increased stability for large Courant numbers, and accelerated convergence of the computations for both implicit and explicit applications. Several examples are presented to demonstrate the ability of this method to solve the equations governing compressible fluid flow.

An immersed boundary formulation for simulating high-speed compressible viscous flows with moving solids

NASA Astrophysics Data System (ADS)

Qu, Yegao; Shi, Ruchao; Batra, Romesh C.

2018-02-01

We present a robust sharp-interface immersed boundary method for numerically studying high speed flows of compressible and viscous fluids interacting with arbitrarily shaped either stationary or moving rigid solids. The Navier-Stokes equations are discretized on a rectangular Cartesian grid based on a low-diffusion flux splitting method for inviscid fluxes and conservative high-order central-difference schemes for the viscous components. Discontinuities such as those introduced by shock waves and contact surfaces are captured by using a high-resolution weighted essentially non-oscillatory (WENO) scheme. Ghost cells in the vicinity of the fluid-solid interface are introduced to satisfy boundary conditions on the interface. Values of variables in the ghost cells are found by using a constrained moving least squares method (CMLS) that eliminates numerical instabilities encountered in the conventional MLS formulation. The solution of the fluid flow and the solid motion equations is advanced in time by using the third-order Runge-Kutta and the implicit Newmark integration schemes, respectively. The performance of the proposed method has been assessed by computing results for the following four problems: shock-boundary layer interaction, supersonic viscous flows past a rigid cylinder, moving piston in a shock tube and lifting off from a flat surface of circular, rectangular and elliptic cylinders triggered by shock waves, and comparing computed results with those available in the literature.

Compressible, multiphase semi-implicit method with moment of fluid interface representation

DOE PAGES

Jemison, Matthew; Sussman, Mark; Arienti, Marco

2014-09-16

A unified method for simulating multiphase flows using an exactly mass, momentum, and energy conserving Cell-Integrated Semi-Lagrangian advection algorithm is presented. The deforming material boundaries are represented using the moment-of-fluid method. Our new algorithm uses a semi-implicit pressure update scheme that asymptotically preserves the standard incompressible pressure projection method in the limit of infinite sound speed. The asymptotically preserving attribute makes the new method applicable to compressible and incompressible flows including stiff materials; enabling large time steps characteristic of incompressible flow algorithms rather than the small time steps required by explicit methods. Moreover, shocks are captured and material discontinuities aremore » tracked, without the aid of any approximate or exact Riemann solvers. As a result, wimulations of underwater explosions and fluid jetting in one, two, and three dimensions are presented which illustrate the effectiveness of the new algorithm at efficiently computing multiphase flows containing shock waves and material discontinuities with large “impedance mismatch.”« less

A new limiting procedure for discontinuous Galerkin methods applied to compressible multiphase flows with shocks and interfaces

NASA Astrophysics Data System (ADS)

Henry de Frahan, Marc T.; Varadan, Sreenivas; Johnsen, Eric

2015-01-01

Although the Discontinuous Galerkin (DG) method has seen widespread use for compressible flow problems in a single fluid with constant material properties, it has yet to be implemented in a consistent fashion for compressible multiphase flows with shocks and interfaces. Specifically, it is challenging to design a scheme that meets the following requirements: conservation, high-order accuracy in smooth regions and non-oscillatory behavior at discontinuities (in particular, material interfaces). Following the interface-capturing approach of Abgrall [1], we model flows of multiple fluid components or phases using a single equation of state with variable material properties; discontinuities in these properties correspond to interfaces. To represent compressible phenomena in solids, liquids, and gases, we present our analysis for equations of state belonging to the Mie-Grüneisen family. Within the DG framework, we propose a conservative, high-order accurate, and non-oscillatory limiting procedure, verified with simple multifluid and multiphase problems. We show analytically that two key elements are required to prevent spurious pressure oscillations at interfaces and maintain conservation: (i) the transport equation(s) describing the material properties must be solved in a non-conservative weak form, and (ii) the suitable variables must be limited (density, momentum, pressure, and appropriate properties entering the equation of state), coupled with a consistent reconstruction of the energy. Further, we introduce a physics-based discontinuity sensor to apply limiting in a solution-adaptive fashion. We verify this approach with one- and two-dimensional problems with shocks and interfaces, including high pressure and density ratios, for fluids obeying different equations of state to illustrate the robustness and versatility of the method. The algorithm is implemented on parallel graphics processing units (GPU) to achieve high speedup.

A non-oscillatory energy-splitting method for the computation of compressible multi-fluid flows

NASA Astrophysics Data System (ADS)

Lei, Xin; Li, Jiequan

2018-04-01

This paper proposes a new non-oscillatory energy-splitting conservative algorithm for computing multi-fluid flows in the Eulerian framework. In comparison with existing multi-fluid algorithms in the literature, it is shown that the mass fraction model with isobaric hypothesis is a plausible choice for designing numerical methods for multi-fluid flows. Then we construct a conservative Godunov-based scheme with the high order accurate extension by using the generalized Riemann problem solver, through the detailed analysis of kinetic energy exchange when fluids are mixed under the hypothesis of isobaric equilibrium. Numerical experiments are carried out for the shock-interface interaction and shock-bubble interaction problems, which display the excellent performance of this type of schemes and demonstrate that nonphysical oscillations are suppressed around material interfaces substantially.

Measurements of the equations of state and spectrum of nonideal xenon plasma under shock compression

NASA Astrophysics Data System (ADS)

Zheng, J.; Gu, Y. J.; Chen, Z. Y.; Chen, Q. F.

2010-08-01

Experimental equations of state on generation of nonideal xenon plasma by intense shock wave compression was presented in the ranges of pressure of 2-16 GPa and temperature of 31-50 kK, and the xenon plasma with the nonideal coupling parameter Γ range from 0.6-2.1 was generated. The shock wave was produced using the flyer plate impact and accelerated up to ˜6km/s with a two-stage light gas gun. Gaseous specimens were shocked from two initial pressures of 0.80 and 4.72 MPa at room temperature. Time-resolved spectral radiation histories were recorded by using a multiwavelength channel pyrometer. The transient spectra with the wavelength range of 460-700 nm were recorded by using a spectrometer to evaluate the shock temperature. Shock velocity was measured and particle velocity was determined by the impedance matching methods. The equations of state of xenon plasma and ionization degree have been discussed in terms of the self-consistent fluid variational theory.

Measurements of the equations of state and spectrum of nonideal xenon plasma under shock compression.

PubMed

Zheng, J; Gu, Y J; Chen, Z Y; Chen, Q F

2010-08-01

Experimental equations of state on generation of nonideal xenon plasma by intense shock wave compression was presented in the ranges of pressure of 2-16 GPa and temperature of 31-50 kK, and the xenon plasma with the nonideal coupling parameter Γ range from 0.6-2.1 was generated. The shock wave was produced using the flyer plate impact and accelerated up to ∼6 km/s with a two-stage light gas gun. Gaseous specimens were shocked from two initial pressures of 0.80 and 4.72 MPa at room temperature. Time-resolved spectral radiation histories were recorded by using a multiwavelength channel pyrometer. The transient spectra with the wavelength range of 460-700 nm were recorded by using a spectrometer to evaluate the shock temperature. Shock velocity was measured and particle velocity was determined by the impedance matching methods. The equations of state of xenon plasma and ionization degree have been discussed in terms of the self-consistent fluid variational theory.

Burnett-Cattaneo continuum theory for shock waves.

PubMed

Holian, Brad Lee; Mareschal, Michel; Ravelo, Ramon

2011-02-01

We model strong shock-wave propagation, both in the ideal gas and in the dense Lennard-Jones fluid, using a refinement of earlier work, which accounts for the cold compression in the early stages of the shock rise by a nonlinear, Burnett-like, strain-rate dependence of the thermal conductivity, and relaxation of kinetic-temperature components on the hot, compressed side of the shock front. The relaxation of the disequilibrium among the three components of the kinetic temperature, namely, the difference between the component in the direction of a planar shock wave and those in the transverse directions, particularly in the region near the shock front, is accomplished at a much more quantitative level by a rigorous application of the Cattaneo-Maxwell relaxation equation to a reference solution, namely, the steady shock-wave solution of linear Navier-Stokes-Fourier theory, along with the nonlinear Burnett heat-flux term. Our new continuum theory is in nearly quantitative agreement with nonequilibrium molecular-dynamics simulations under strong shock-wave conditions, using relaxation parameters obtained from the reference solution. ©2011 American Physical Society

Propagation of exponential shock wave in an axisymmetric rotating non-ideal dusty gas

NASA Astrophysics Data System (ADS)

Nath, G.

2016-09-01

One-dimensional unsteady isothermal and adiabatic flow behind a strong exponential shock wave propagating in a rotational axisymmetric mixture of non-ideal gas and small solid particles, which has variable azimuthal and axial fluid velocities, is analyzed. The shock wave is driven out by a piston moving with time according to exponential law. The azimuthal and axial components of the fluid velocity in the ambient medium are assumed to be varying and obeying exponential laws. In the present work, small solid particles are considered as pseudo-fluid with the assumption that the equilibrium flow-conditions are maintained in the flow-field, and the viscous-stress and heat conduction of the mixture are negligible. 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 and compressibility. It is found that the assumption of zero temperature gradient brings a profound change in the density, axial component of vorticity vector and compressibility distributions as compared to that of the adiabatic case. To investigate the behavior of the flow variables and the influence on the shock wave propagation by the parameter of non-idealness of the gas overline{b} in the mixture as well as by the mass concentration of solid particles in the mixture Kp and by the ratio of the density of solid particles to the initial density of the gas G1 are worked out in detail. It is interesting to note that the shock strength increases with an increase in G1 ; whereas it decreases with an increase in overline{b} . Also, a comparison between the solutions in the cases of isothermal and adiabatic flows is made.

Computation of Thermally Perfect Properties of Oblique Shock Waves

NASA Technical Reports Server (NTRS)

Tatum, Kenneth E.

1996-01-01

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

Optical pin apparatus for measuring the arrival time and velocity of shock waves and particles

DOEpatents

Benjamin, R.F.

1983-10-18

An apparatus for the detection of the arrival and for the determination of the velocity of disturbances such as shock-wave fronts and/or projectiles. Optical pins using fluid-filled microballoons as the light source and an optical fiber as a link to a photodetector have been used to investigate shock-waves and projectiles. A microballoon filled with a noble gas is affixed to one end of a fiber-optic cable, and the other end of the cable is attached to a high-speed streak camera. As the shock-front or projectile compresses the microballoon, the gas inside is heated and compressed producing a bright flash of light. The flash of light is transmitted via the optic cable to the streak camera where it is recorded. One image-converter streak camera is capable of recording information from more than 100 microballoon-cable combinations simultaneously.

Optical pin apparatus for measuring the arrival time and velocity of shock waves and particles

DOEpatents

Benjamin, Robert F.

1987-01-01

An apparatus for the detection of the arrival and for the determination of the velocity of disturbances such as shock-wave fronts and/or projectiles. Optical pins using fluid-filled microballoons as the light source and an optical fiber as a link to a photodetector have been used to investigate shock-waves and projectiles. A microballoon filled with a noble gas is affixed to one end of a fiber-optic cable, and the other end of the cable is attached to a high-speed streak camera. As the shock-front or projectile compresses the microballoon, the gas inside is heated and compressed producing a bright flash of light. The flash of light is transmitted via the optic cable to the streak camera where it is recorded. One image-converter streak camera is capable of recording information from more than 100 microballoon-cable combinations simultaneously.

Optical pin apparatus for measuring the arrival time and velocity of shock waves and particles

DOEpatents

Benjamin, R.F.

1987-03-10

An apparatus is disclosed for the detection of the arrival and for the determination of the velocity of disturbances such as shock-wave fronts and/or projectiles. Optical pins using fluid-filled microballoons as the light source and an optical fiber as a link to a photodetector have been used to investigate shock-waves and projectiles. A microballoon filled with a noble gas is affixed to one end of a fiber-optic cable, and the other end of the cable is attached to a high-speed streak camera. As the shock-front or projectile compresses the microballoon, the gas inside is heated and compressed producing a bright flash of light. The flash of light is transmitted via the optic cable to the streak camera where it is recorded. One image-converter streak camera is capable of recording information from more than 100 microballoon-cable combinations simultaneously. 3 figs.

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.

Instability analysis of cosmic viscoelastic gyro-gravitating clouds in the presence of dark matter

NASA Astrophysics Data System (ADS)

Karmakar, Pralay Kumar; Das, Papari

2017-08-01

A classical formalism for the weakly nonlinear instability analysis of a gravitating rotating viscoelastic gaseous cloud in the presence of gyratory dark matter is presented on the cosmic Jeans flat scales of space and time. The constituent neutral gaseous fluid (NGF) and dark matter fluid (DMF) are inter-coupled frictionally via mutual gravity alone. Application of standard nonlinear perturbation techniques over the complex gyro-gravitating clouds results in a unique conjugated pair of viscoelastic forced Burgers (VFB) equations. The VFB pair is conjointly twinned by correlational viscoelastic effects. There is no regular damping term here, unlike, in the conventional Burgers equation for the luminous (bright) matter solely. Instead, an interesting linear self-consistent derivative force-term naturalistically appears. A numerical illustrative platform is provided to reveal the micro-physical insights behind the weakly non-linear natural diffusive eigen-modes. It is fantastically seen that the perturbed NGF evolves as extended compressive solitons and compressive shock-like structures. In contrast, the perturbed DMF grows as rarefactive extended solitons and hybrid shocks. The latter is micro-physically composed of rarefactive solitons and compressive shocks. The consistency and reliability of the results are validated in the panoptic light of the existing reports based on the preeminent nonlinear advection-diffusion-based Burgers fabric. At the last, we highlight the main implications and non-trivial futuristic applications of the explored findings.

Artificial fluid properties for large-eddy simulation of compressible turbulent mixing

NASA Astrophysics Data System (ADS)

Cook, Andrew W.

2007-05-01

An alternative methodology is described for large-eddy simulation (LES) of flows involving shocks, turbulence, and mixing. In lieu of filtering the governing equations, it is postulated that the large-scale behavior of a LES fluid, i.e., a fluid with artificial properties, will be similar to that of a real fluid, provided the artificial properties obey certain constraints. The artificial properties consist of modifications to the shear viscosity, bulk viscosity, thermal conductivity, and species diffusivity of a fluid. The modified transport coefficients are designed to damp out high wavenumber modes, close to the resolution limit, without corrupting lower modes. Requisite behavior of the artificial properties is discussed and results are shown for a variety of test problems, each designed to exercise different aspects of the models. When combined with a tenth-order compact scheme, the overall method exhibits excellent resolution characteristics for turbulent mixing, while capturing shocks and material interfaces in a crisp fashion.

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.

Deflagration Wave Profiles

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

Menikoff, Ralph

2012-04-03

Shock initiation in a plastic-bonded explosives (PBX) is due to hot spots. Current reactive burn models are based, at least heuristically, on the ignition and growth concept. The ignition phase occurs when a small localized region of high temperature (or hot spot) burns on a fast time scale. This is followed by a growth phase in which a reactive front spreads out from the hot spot. Propagating reactive fronts are deflagration waves. A key question is the deflagration speed in a PBX compressed and heated by a shock wave that generated the hot spot. Here, the ODEs for a steadymore » deflagration wave profile in a compressible fluid are derived, along with the needed thermodynamic quantities of realistic equations of state corresponding to the reactants and products of a PBX. The properties of the wave profile equations are analyzed and an algorithm is derived for computing the deflagration speed. As an illustrative example, the algorithm is applied to compute the deflagration speed in shock compressed PBX 9501 as a function of shock pressure. The calculated deflagration speed, even at the CJ pressure, is low compared to the detonation speed. The implication of this are briefly discussed.« less

Shock-jump conditions in a general medium: weak-solution approach

NASA Astrophysics Data System (ADS)

Forbes, L. K.; Krzysik, O. A.

2017-05-01

General conservation laws are considered, and the concept of a weak solution is extended to the case of an equation involving three space variables and time. Four-dimensional vector calculus is used to develop general jump conditions at a shock wave in the material. To illustrate the use of this result, jump conditions at a shock in unsteady three-dimensional compressible gas flow are presented. It is then proved rigorously that these reduce to the commonly assumed conditions in coordinates normal and tangential to the shock face. A similar calculation is also outlined for an unsteady three-dimensional shock in magnetohydrodynamics, and in a chemically reactive fluid. The technique is available for determining shock-jump conditions in quite general continuous media.

On the use of adaptive multiresolution method with time-varying tolerance for compressible fluid flows

NASA Astrophysics Data System (ADS)

Soni, V.; Hadjadj, A.; Roussel, O.

2017-12-01

In this paper, a fully adaptive multiresolution (MR) finite difference scheme with a time-varying tolerance is developed to study compressible fluid flows containing shock waves in interaction with solid obstacles. To ensure adequate resolution near rigid bodies, the MR algorithm is combined with an immersed boundary method based on a direct-forcing approach in which the solid object is represented by a continuous solid-volume fraction. The resulting algorithm forms an efficient tool capable of solving linear and nonlinear waves on arbitrary geometries. Through a one-dimensional scalar wave equation, the accuracy of the MR computation is, as expected, seen to decrease in time when using a constant MR tolerance considering the accumulation of error. To overcome this problem, a variable tolerance formulation is proposed, which is assessed through a new quality criterion, to ensure a time-convergence solution for a suitable quality resolution. The newly developed algorithm coupled with high-resolution spatial and temporal approximations is successfully applied to shock-bluff body and shock-diffraction problems solving Euler and Navier-Stokes equations. Results show excellent agreement with the available numerical and experimental data, thereby demonstrating the efficiency and the performance of the proposed method.

Fluid Dynamics for Physicists

NASA Astrophysics Data System (ADS)

Faber, T. E.

1995-08-01

This textbook provides an accessible and comprehensive account of fluid dynamics that emphasizes fundamental physical principles and stresses connections with other branches of physics. Beginning with a basic introduction, the book goes on to cover many topics not typically treated in texts, such as compressible flow and shock waves, sound attenuation and bulk viscosity, solitary waves and ship waves, thermal convection, instabilities, turbulence, and the behavior of anisotropic, non-Newtonian and quantum fluids. Undergraduate or graduate students in physics or engineering who are taking courses in fluid dynamics will find this book invaluable.

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.

Methods for compressible multiphase flows and their applications

NASA Astrophysics Data System (ADS)

Kim, H.; Choe, Y.; Kim, H.; Min, D.; Kim, C.

2018-06-01

This paper presents an efficient and robust numerical framework to deal with multiphase real-fluid flows and their broad spectrum of engineering applications. A homogeneous mixture model incorporated with a real-fluid equation of state and a phase change model is considered to calculate complex multiphase problems. As robust and accurate numerical methods to handle multiphase shocks and phase interfaces over a wide range of flow speeds, the AUSMPW+_N and RoeM_N schemes with a system preconditioning method are presented. These methods are assessed by extensive validation problems with various types of equation of state and phase change models. Representative realistic multiphase phenomena, including the flow inside a thermal vapor compressor, pressurization in a cryogenic tank, and unsteady cavitating flow around a wedge, are then investigated as application problems. With appropriate physical modeling followed by robust and accurate numerical treatments, compressible multiphase flow physics such as phase changes, shock discontinuities, and their interactions are well captured, confirming the suitability of the proposed numerical framework to wide engineering applications.

Astrophysical fluid dynamics

NASA Astrophysics Data System (ADS)

Ogilvie, Gordon I.

2016-06-01

> These lecture notes and example problems are based on a course given at the University of Cambridge in Part III of the Mathematical Tripos. Fluid dynamics is involved in a very wide range of astrophysical phenomena, such as the formation and internal dynamics of stars and giant planets, the workings of jets and accretion discs around stars and black holes and the dynamics of the expanding Universe. Effects that can be important in astrophysical fluids include compressibility, self-gravitation and the dynamical influence of the magnetic field that is `frozen in' to a highly conducting plasma. The basic models introduced and applied in this course are Newtonian gas dynamics and magnetohydrodynamics (MHD) for an ideal compressible fluid. The mathematical structure of the governing equations and the associated conservation laws are explored in some detail because of their importance for both analytical and numerical methods of solution, as well as for physical interpretation. Linear and nonlinear waves, including shocks and other discontinuities, are discussed. The spherical blast wave resulting from a supernova, and involving a strong shock, is a classic problem that can be solved analytically. Steady solutions with spherical or axial symmetry reveal the physics of winds and jets from stars and discs. The linearized equations determine the oscillation modes of astrophysical bodies, as well as their stability and their response to tidal forcing.

The Investigation of Ghost Fluid Method for Simulating the Compressible Two-Medium Flow

NASA Astrophysics Data System (ADS)

Lu, Hai Tian; Zhao, Ning; Wang, Donghong

2016-06-01

In this paper, we investigate the conservation error of the two-dimensional compressible two-medium flow simulated by the front tracking method. As the improved versions of the original ghost fluid method, the modified ghost fluid method and the real ghost fluid method are selected to define the interface boundary conditions, respectively, to show different effects on the conservation error. A Riemann problem is constructed along the normal direction of the interface in the front tracking method, with the goal of obtaining an efficient procedure to track the explicit sharp interface precisely. The corresponding Riemann solutions are also used directly in these improved ghost fluid methods. Extensive numerical examples including the sod tube and the shock-bubble interaction are tested to calculate the conservation error. It is found that these two ghost fluid methods have distinctive performances for different initial conditions of the flow field, and the related conclusions are made to suggest the best choice for the combination.

Resistivity behavior of hydrogen and liquid silane at high shock compression

NASA Astrophysics Data System (ADS)

Wang, Yi-Gao; Liu, Fu-Sheng; Liu, Qi-Jun

2018-07-01

To study the electrical properties of hydrogen rich compounds under extreme conditions, the electrical resistivity of density hydrogen and silane fluid was measured, respectively. The hydrogen sample was prepared by compressing pure hydrogen gas to 10 MPa in a coolant target system at the temperature of 77 K. The silane sample can be obtained with the same method. High-pressure and high-temperature experiments were performed using a two-stage light-gas gun. The electrical resistivity of the sample decreased with increasing pressure and temperature as expected. A minimum electrical resistivity value of 0.3 × 10-3 Ω cm at 138 GPa and 4100 K was obtained for silane. The minimum resistivity of hydrogen in the state of 102 GPa and 4300 K was 0.35 Ω cm. It showed that the measured electrical resistivity of the shock-compressed hydrogen was an order of magnitude higher than fluid silane at 50-90 GPa. However, beyond 100 GPa, the resistivity difference between silane and hydrogen was very minor. The carriers in the sample were hydrogen, and the concentration of hydrogen atoms in these two substances was close to each other. These results supported the theoretical prediction that silane was interpreted simply in terms of chemical decomposition into silicon nanoparticles and fluid hydrogen, and electrical conduction flows predominately dominated by the fluid hydrogen. In addition, the results also supported the theory of "chemical precompression", the existence of Sisbnd H bond helped to reduce the pressure of hydrogen metallization. These findings could lead the way for further metallic phases of hydrogen-rich materials and experimental studies.

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.

Nonstandard Analysis and Jump Conditions for Converging Shock Waves

NASA Technical Reports Server (NTRS)

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

2008-01-01

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

Growth rate of the linear Richtmyer-Meshkov instability when a shock is reflected

NASA Astrophysics Data System (ADS)

Wouchuk, J. G.

2001-05-01

An analytic model is presented to calculate the growth rate of the linear Richtmyer-Meshkov instability in the shock-reflected case. The model allows us to calculate the asymptotic contact surface perturbation velocity for any value of the incident shock intensity, arbitrary fluids compressibilities, and for any density ratio at the interface. The growth rate comes out as the solution of a system of two coupled functional equations and is expressed formally as an infinite series. The distinguishing feature of the procedure shown here is the high speed of convergence of the intermediate calculations. There is excellent agreement with previous linear simulations and experiments done in shock tubes.

Entropic lattice Boltzmann model for compressible flows.

PubMed

Frapolli, N; Chikatamarla, S S; Karlin, I V

2015-12-01

We present a lattice Boltzmann model (LBM) that covers the entire range of fluid flows, from low Mach weakly compressible to transonic and supersonic flows. One of the most restrictive limitations of the lattice Boltzmann method, the low Mach number limit, is overcome here by three fundamental changes to the LBM scheme: use of an appropriately chosen multispeed lattice, accurate evaluation of the equilibrium, and the entropic relaxation for the collision. The range of applications is demonstrated through the simulation of a bow shock in front of an airfoil and the simulation of decaying compressible turbulence with shocklets.

Studies in turbulence

NASA Technical Reports Server (NTRS)

Gatski, Thomas B. (Editor); Sarkar, Sutanu (Editor); Speziale, Charles G. (Editor)

1992-01-01

Various papers on turbulence are presented. Individual topics addressed include: modeling the dissipation rate in rotating turbulent flows, mapping closures for turbulent mixing and reaction, understanding turbulence in vortex dynamics, models for the structure and dynamics of near-wall turbulence, complexity of turbulence near a wall, proper orthogonal decomposition, propagating structures in wall-bounded turbulence flows. Also discussed are: constitutive relation in compressible turbulence, compressible turbulence and shock waves, direct simulation of compressible turbulence in a shear flow, structural genesis in wall-bounded turbulence flows, vortex lattice structure of turbulent shear slows, etiology of shear layer vortices, trilinear coordinates in fluid mechanics.

A shock absorber model for structure-borne noise analyses

NASA Astrophysics Data System (ADS)

Benaziz, Marouane; Nacivet, Samuel; Thouverez, Fabrice

2015-08-01

Shock absorbers are often responsible for undesirable structure-borne noise in cars. The early numerical prediction of this noise in the automobile development process can save time and money and yet remains a challenge for industry. In this paper, a new approach to predicting shock absorber structure-borne noise is proposed; it consists in modelling the shock absorber and including the main nonlinear phenomena responsible for discontinuities in the response. The model set forth herein features: compressible fluid behaviour, nonlinear flow rate-pressure relations, valve mechanical equations and rubber mounts. The piston, base valve and complete shock absorber model are compared with experimental results. Sensitivity of the shock absorber response is evaluated and the most important parameters are classified. The response envelope is also computed. This shock absorber model is able to accurately reproduce local nonlinear phenomena and improves our state of knowledge on potential noise sources within the shock absorber.

Richtmyer-Meshkov instability for elastic-plastic solids in converging geometries

NASA Astrophysics Data System (ADS)

López Ortega, A.; Lombardini, M.; Barton, P. T.; Pullin, D. I.; Meiron, D. I.

2015-03-01

We present a detailed study of the interface instability that develops at the boundary between a shell of elastic-plastic material and a cylindrical core of confined gas during the inbound implosive motion generated by a shock-wave. The main instability in this configuration is the so-called Richtmyer-Meshkov instability that arises when the shock wave crosses the material interface. Secondary instabilities, such as Rayleigh-Taylor, due to the acceleration of the interface, and Kelvin-Helmholtz, due to slip between solid and fluid, arise as the motion progresses. The reflection of the shock wave at the axis and its second interaction with the material interface as the shock moves outbound, commonly known as re-shock, results in a second Richtmyer-Meshkov instability that potentially increases the growth rate of interface perturbations, resulting in the formation of a mixing zone typical of fluid-fluid configurations and the loss of the initial perturbation length scales. The study of this problem is of interest for achieving stable inertial confinement fusion reactions but its complexity and the material conditions produced by the implosion close to the axis prove to be challenging for both experimental and numerical approaches. In this paper, we attempt to circumvent some of the difficulties associated with a classical numerical treatment of this problem, such as element inversion in Lagrangian methods or failure to maintain the relationship between the determinant of the deformation tensor and the density in Eulerian approaches, and to provide a description of the different events that occur during the motion of the interface. For this purpose, a multi-material numerical solver for evolving in time the equations of motion for solid and fluid media in an Eulerian formalism has been implemented in a Cartesian grid. Equations of state are derived using thermodynamically consistent hyperelastic relations between internal energy and stresses. The resolution required for capturing the state of solid and fluid materials close to the origin is achieved by making use of adaptive mesh refinement techniques. Rigid-body rotations contained in the deformation tensor have been shown to have a negative effect on the accuracy of the method in extreme compression conditions and are removed by transforming the deformation tensor into a stretch tensor at each time step. With this methodology, the evolution of the interface can be tracked up to a point at which numerical convergence cannot be achieved due to the inception of numerical Kelvin-Helmholtz instabilities caused by slip between materials. From that point, only qualitative conclusions can be extracted from this analysis. The influence of different geometrical parameters, initial conditions, and material properties on the motion of the interface are investigated. Some major differences are found with respect to the better understood fluid-fluid case. For example, increasing the wave number of the interface perturbations leads to a second phase reversal of the interface (i.e., the first phase reversal of the interface naturally occurs due to the initial negative growth-rate of the instability as the shock wave transitions from the high-density material to the low-density one). This phenomenon is caused by the compressive effect of the converging geometry and the low density of the gas with respect to the solid, which allows for the formation of an incipient spike in the center of an already existing bubble. Multiple solid-gas density ratios are also considered. Results show that the motion of the interface asymptotically converges to the solid-vacuum case. When a higher initial density for the gas is considered, the growth rate of interface perturbations decreases and, in some situations, its sign may reverse, as the fluid becomes more dense than the solid due to having higher compressibility. Finally, the influence of the Mach number of the driving shock and the yield stress on the mixing-zone is examined. We find that the width of the mixing zone produced after the re-shock increases in proportion to the strength of the incident shock. An increased yield stress in the solid material makes the interface less unstable due to vorticity being carried away from the interface by shear waves and limits the generation of smaller length scales after the re-shock.

Mathematical modeling of impact of two metal plates using two-fluid approach

NASA Astrophysics Data System (ADS)

Utkin, P. S.; Fortova, S. V.

2018-01-01

The paper is devoted to the development of the two-fluid mathematical model and the computational algorithm for the modeling of two metal plates impact. In one-dimensional case the governing system of equations comprises seven equations: three conservation laws for each fluid and transfer equation for the volume fraction of one of the fluids. Both fluids are considered to be compressible and equilibrium on velocities. Pressures equilibrium is used as fluids interface condition. The system has hyperbolic type but could not be written in the conservative form because of nozzling terms in the right-hand side of the equations. The algorithm is based on the Harten-Lax-van Leer numerical flux function. The robust computation in the presence of the interface boundary is carried out due to the special pressure relaxation procedure. The problem is solved using stiffened gas equations of state for each fluid. The parameters in the equations of state are calibrated using the results of computations using wide-range equations of state for the metals. In simulations of metal plates impact we get two shocks after the initial impact that propagate to the free surfaces of the samples. The characteristics of shock waves are close (maximum relative error in characteristics of shocks is not greater than 7%) to the data from the wide-range equations of states computations.

Equations of state of detonation products: ammonia and methane

NASA Astrophysics Data System (ADS)

Lang, John; Dattelbaum, Dana; Goodwin, Peter; Garcia, Daniel; Coe, Joshua; Leiding, Jeffery; Gibson, Lloyd; Bartram, Brian

2015-06-01

Ammonia (NH3) and methane (CH4) are two principal product gases resulting from explosives detonation, and the decomposition of other organic materials under shockwave loading (such as foams). Accurate thermodynamic descriptions of these gases are important for understanding the detonation performance of high explosives. However, shock compression data often do not exist for molecular species in the dense gas phase, and are limited in the fluid phase. Here, we present equation of state measurements of elevated initial density ammonia and methane gases dynamically compressed in gas-gun driven plate impact experiments. Pressure and density of the shocked gases on the principal Hugoniot were determined from direct particle velocity and shock wave velocity measurements recorded using optical velocimetry (Photonic Doppler velocimetry (PDV) and VISAR (velocity interferometer system for any reflector)). Streak spectroscopy and 5-color pyrometry were further used to measure the emission from the shocked gases, from which the temperatures of the shocked gases were estimated. Up to 0.07 GPa, ammonia was not observed to ionize, with temperature remaining below 7000 K. These results provide quantitative measurements of the Hugoniot locus for improving equations of state models of detonation products.

Three dimensional investigation of the shock train structure in a convergent-divergent nozzle

NASA Astrophysics Data System (ADS)

Mousavi, Seyed Mahmood; Roohi, Ehsan

2014-12-01

Three-dimensional computational fluid dynamics analyses have been employed to study the compressible and turbulent flow of the shock train in a convergent-divergent nozzle. The primary goal is to determine the behavior, location, and number of shocks. In this context, full multi-grid initialization, Reynolds stress turbulence model (RSM), and the grid adaption techniques in the Fluent software are utilized under the 3D investigation. The results showed that RSM solution matches with the experimental data suitably. The effects of applying heat generation sources and changing inlet flow total temperature have been investigated. Our simulations showed that changes in the heat generation rate and total temperature of the intake flow influence on the starting point of shock, shock strength, minimum pressure, as well as the maximum flow Mach number.

Lagrangian averaging, nonlinear waves, and shock regularization

NASA Astrophysics Data System (ADS)

Bhat, Harish S.

In this thesis, we explore various models for the flow of a compressible fluid as well as model equations for shock formation, one of the main features of compressible fluid flows. We begin by reviewing the variational structure of compressible fluid mechanics. We derive the barotropic compressible Euler equations from a variational principle in both material and spatial frames. Writing the resulting equations of motion requires certain Lie-algebraic calculations that we carry out in detail for expository purposes. Next, we extend the derivation of the Lagrangian averaged Euler (LAE-alpha) equations to the case of barotropic compressible flows. The derivation in this thesis involves averaging over a tube of trajectories etaepsilon centered around a given Lagrangian flow eta. With this tube framework, the LAE-alpha equations are derived by following a simple procedure: start with a given action, expand via Taylor series in terms of small-scale fluid fluctuations xi, truncate, average, and then model those terms that are nonlinear functions of xi. We then analyze a one-dimensional subcase of the general models derived above. We prove the existence of a large family of traveling wave solutions. Computing the dispersion relation for this model, we find it is nonlinear, implying that the equation is dispersive. We carry out numerical experiments that show that the model possesses smooth, bounded solutions that display interesting pattern formation. Finally, we examine a Hamiltonian partial differential equation (PDE) that regularizes the inviscid Burgers equation without the addition of standard viscosity. Here alpha is a small parameter that controls a nonlinear smoothing term that we have added to the inviscid Burgers equation. We show the existence of a large family of traveling front solutions. We analyze the initial-value problem and prove well-posedness for a certain class of initial data. We prove that in the zero-alpha limit, without any standard viscosity, solutions of the PDE converge strongly to weak solutions of the inviscid Burgers equation. We provide numerical evidence that this limit satisfies an entropy inequality for the inviscid Burgers equation. We demonstrate a Hamiltonian structure for the PDE.

Assessment of WENO-extended two-fluid modelling in compressible multiphase flows

NASA Astrophysics Data System (ADS)

Kitamura, Keiichi; Nonomura, Taku

2017-03-01

The two-fluid modelling based on an advection-upwind-splitting-method (AUSM)-family numerical flux function, AUSM+-up, following the work by Chang and Liou [Journal of Computational Physics 2007;225: 840-873], has been successfully extended to the fifth order by weighted-essentially-non-oscillatory (WENO) schemes. Then its performance is surveyed in several numerical tests. The results showed a desired performance in one-dimensional benchmark test problems: Without relying upon an anti-diffusion device, the higher-order two-fluid method captures the phase interface within a fewer grid points than the conventional second-order method, as well as a rarefaction wave and a very weak shock. At a high pressure ratio (e.g. 1,000), the interpolated variables appeared to affect the performance: the conservative-variable-based characteristic-wise WENO interpolation showed less sharper but more robust representations of the shocks and expansions than the primitive-variable-based counterpart did. In two-dimensional shock/droplet test case, however, only the primitive-variable-based WENO with a huge void fraction realised a stable computation.

Prediction of Shock-Induced Cavitation in Water

NASA Astrophysics Data System (ADS)

Brundage, Aaron

2013-06-01

Fluid-structure interaction problems that require estimating the response of thin structures within fluids to shock loading has wide applicability. For example, these problems may include underwater explosions and the dynamic response of ships and submarines; and biological applications such as Traumatic Brain Injury (TBI) and wound ballistics. In all of these applications the process of cavitation, where small cavities with dissolved gases or vapor are formed as the local pressure drops below the vapor pressure due to shock hydrodynamics, can cause significant damage to the surrounding thin structures or membranes if these bubbles collapse, generating additional shock loading. Hence, a two-phase equation of state (EOS) with three distinct regions of compression, expansion, and tension was developed to model shock-induced cavitation. This EOS was evaluated by comparing data from pressure and temperature shock Hugoniot measurements for water up to 400 kbar, and data from ultrasonic pressure measurements in tension to -0.3 kbar, to simulated responses from CTH, an Eulerian, finite volume shock code. The new EOS model showed significant improvement over pre-existing CTH models such as the SESAME EOS for capturing cavitation. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy/NNSA under contract DE-AC04-94AL85000.

A Cartesian-based embedded geometry technique with adaptive high-order finite differences for compressible flow around complex geometries

NASA Astrophysics Data System (ADS)

Uddin, H.; Kramer, R. M. J.; Pantano, C.

2014-04-01

An immersed boundary methodology to solve the compressible Navier-Stokes equations around complex geometries in Cartesian fluid dynamics solvers is described. The objective of the new approach is to enable smooth reconstruction of pressure and viscous stresses around the embedded objects without spurious numerical artifacts. A standard level set represents the boundary of the object and defines a fictitious domain into which the flow fields are smoothly extended. Boundary conditions on the surface are enforced by an approach inspired by analytic continuation. Each fluid field is extended independently, constrained only by the boundary condition associated with that field. Unlike most existing methods, no jump conditions or explicit derivation of them from the boundary conditions are required in this approach. Numerical stiffness that arises when the fluid-solid interface is close to grid points of the mesh is addressed by preconditioning. In addition, the embedded geometry technique is coupled with a stable high-order adaptive discretization that is enabled around the object boundary to enhance resolution. The stencils used to transition the order of accuracy of the discretization are derived using the summation-by-parts technique that ensures stability. Applications to shock reflections, shock-ramp interactions, and supersonic and low-Mach number flows over two- and three-dimensional geometries are presented.

A Finite-Volume approach for compressible single- and two-phase flows in flexible pipelines with fluid-structure interaction

NASA Astrophysics Data System (ADS)

Daude, F.; Galon, P.

2018-06-01

A Finite-Volume scheme for the numerical computations of compressible single- and two-phase flows in flexible pipelines is proposed based on an approximate Godunov-type approach. The spatial discretization is here obtained using the HLLC scheme. In addition, the numerical treatment of abrupt changes in area and network including several pipelines connected at junctions is also considered. The proposed approach is based on the integral form of the governing equations making it possible to tackle general equations of state. A coupled approach for the resolution of fluid-structure interaction of compressible fluid flowing in flexible pipes is considered. The structural problem is solved using Euler-Bernoulli beam finite elements. The present Finite-Volume method is applied to ideal gas and two-phase steam-water based on the Homogeneous Equilibrium Model (HEM) in conjunction with a tabulated equation of state in order to demonstrate its ability to tackle general equations of state. The extensive application of the scheme for both shock tube and other transient flow problems demonstrates its capability to resolve such problems accurately and robustly. Finally, the proposed 1-D fluid-structure interaction model appears to be computationally efficient.

Laboratory and numerical decompression experiments: an insight into the nucleation and growth of bubbles

NASA Astrophysics Data System (ADS)

Spina, L.; Colucci, S.; De'Michieli Vitturi, M.; Scheu, B.; Dingwell, D. B.

2014-12-01

Numerical modeling, joined with experimental investigations, is fundamental for studying the dynamics of magmatic fluid into the conduit, where direct observations are unattainable. Furthermore, laboratory experiments can provide invaluable data to vunalidate complex multiphase codes. With the aim on unveil the essence of nucleation process, as well as the behavior of the multiphase magmatic fluid, we performed slow decompression experiments in a shock tube system. We choose silicon oil as analogue for the magmatic melt, and saturated it with Argon at 10 MPa for 72h. The slow decompression to atmospheric conditions was monitored through a high speed camera and pressure sensors, located into the experimental conduit. The experimental conditions of the decompression process have then been reproduced numerically with a compressible multiphase solver based on OpenFOAM. Numerical simulations have been performed by the OpenFOAM compressibleInterFoam solver for 2 compressible, non-isothermal immiscible fluids, using a VOF (volume of fluid) phase-fraction based interface capturing approach. The data extracted from 2D images obtained from laboratory analyses were compared to the outcome of numerical investigation, showing the capability of the model to capture the main processes studied.

The principal Hugoniot of Mg2SiO4 to 950 GPa

NASA Astrophysics Data System (ADS)

Townsend, J. P.; Root, S.; Shulenburger, L.; Lemke, R. W.; Kraus, R. G.; Jacobsen, S. B.; Spaulding, D.; Davies, E.; Stewart, S. T.

2017-12-01

We present new measurements and ab-initio calculations of the principal Hugoniot states of forsterite Mg2SiO4 in the liquid regime between 200-950 GPa.Forsterite samples were shock compressed along the principal Hugoniot using plate-impact shock compression experiments on the Sandia National Laboratories Z machine facility.In order to gain insight into the physical state of the liquid, we performed quantum molecular dynamics calculations of the Hugoniot and compare the results to experiment.We show that the principal Hugoniot is consistent with that of a single molecular fluid phase of Mg2SiO4, and compare our results to previous dynamic compression experiments and QMD calculations.Finally, we discuss how the results inform planetary accretion and impact models.Sandia National Laboratories is a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-NA0003525.

Laser driven supersonic flow over a compressible foam surface on the Nike lasera)

NASA Astrophysics Data System (ADS)

Harding, E. C.; Drake, R. P.; Aglitskiy, Y.; Plewa, T.; Velikovich, A. L.; Gillespie, R. S.; Weaver, J. L.; Visco, A.; Grosskopf, M. J.; Ditmar, J. R.

2010-05-01

A laser driven millimeter-scale target was used to generate a supersonic shear layer in an attempt to create a Kelvin-Helmholtz (KH) unstable interface in a high-energy-density (HED) plasma. The KH instability is a fundamental fluid instability that remains unexplored in HED plasmas, which are relevant to the inertial confinement fusion and astrophysical environments. In the experiment presented here the Nike laser [S. P. Obenschain et al., Phys. Plasmas 3, 2098 (1996)] was used to create and drive Al plasma over a rippled foam surface. In response to the supersonic Al flow (Mach=2.6±1.1) shocks should form in the Al flow near the perturbations. The experimental data were used to infer the existence and location of these shocks. In addition, the interface perturbations show growth that has possible contributions from both KH and Richtmyer-Meshkov instabilities. Since compressible shear layers exhibit smaller growth, it is important to use the KH growth rate derived from the compressible dispersion relation.

Shock-adiabatic to quasi-isentropic compression of warm dense helium up to 150 GPa

NASA Astrophysics Data System (ADS)

Zheng, J.; Chen, Q. F.; Gu, Y. J.; Li, J. T.; Li, Z. G.; Li, C. J.; Chen, Z. Y.

2017-06-01

Multiple reverberation compression can achieve higher pressure, higher temperature, but lower entropy. It is available to provide an important validation for the elaborate and wider planetary models and simulate the inertial confinement fusion capsule implosion process. In the work, we have developed the thermodynamic and optical properties of helium from shock-adiabatic to quasi-isentropic compression by means of a multiple reverberation technique. By this technique, the initial dense gaseous helium was compressed to high pressure and high temperature and entered the warm dense matter (WDM) region. The experimental equation of state (EOS) of WDM helium in the pressure-density-temperature (P-ρ -T) range of 1 -150 GPa , 0.1 -1.1 g c m-3 , and 4600-24 000 K were measured. The optical radiations emanating from the WDM helium were recorded, and the particle velocity profiles detecting from the sample/window interface were obtained successfully up to 10 times compression. The optical radiation results imply that dense He has become rather opaque after the 2nd compression with a density of about 0.3 g c m-3 and a temperature of about 1 eV. The opaque states of helium under multiple compression were analyzed by the particle velocity measurements. The multiple compression technique could efficiently enhanced the density and the compressibility, and our multiple compression ratios (ηi=ρi/ρ0,i =1 -10 ) of helium are greatly improved from 3.5 to 43 based on initial precompressed density (ρ0) . For the relative compression ratio (ηi'=ρi/ρi -1) , it increases with pressure in the lower density regime and reversely decreases in the higher density regime, and a turning point occurs at the 3rd and 4th compression states under the different loading conditions. This nonmonotonic evolution of the compression is controlled by two factors, where the excitation of internal degrees of freedom results in the increasing compressibility and the repulsive interactions between the particles results in the decreasing compressibility at the onset of electron excitation and ionization. In the P-ρ -T contour with the experiments and the calculations, our multiple compression states from insulating to semiconducting fluid (from transparent to opaque fluid) are illustrated. Our results give an elaborate validation of EOS models and have applications for planetary and stellar opaque atmospheres.

Wedge Shock and Nozzle Exhaust Plume Interaction in a Supersonic Jet Flow

NASA Technical Reports Server (NTRS)

Castner, Raymond; Zaman, Khairul; Fagan, Amy; Heath, Christopher

2014-01-01

Fundamental research for sonic boom reduction is needed to quantify the interaction of shock waves generated from the aircraft wing or tail surfaces with the nozzle exhaust plume. Aft body shock waves that interact with the exhaust plume contribute to the near-field pressure signature of a vehicle. The plume and shock interaction was studied using computational fluid dynamics and compared with experimental data from a coaxial convergent-divergent nozzle flow in an open jet facility. A simple diamond-shaped wedge was used to generate the shock in the outer flow to study its impact on the inner jet flow. Results show that the compression from the wedge deflects the nozzle plume and shocks form on the opposite plume boundary. The sonic boom pressure signature of the nozzle exhaust plume was modified by the presence of the wedge. Both the experimental results and computational predictions show changes in plume deflection.

Computational-hydrodynamic studies of the Noh compressible flow problem using non-ideal equations of state

NASA Astrophysics Data System (ADS)

Honnell, Kevin; Burnett, Sarah; Yorke, Chloe'; Howard, April; Ramsey, Scott

2017-06-01

The Noh problem is classic verification problem in the field of compressible flows. Simple to conceptualize, it is nonetheless difficult for numerical codes to predict correctly, making it an ideal code-verification test bed. In its original incarnation, the fluid is a simple ideal gas; once validated, however, these codes are often used to study highly non-ideal fluids and solids. In this work the classic Noh problem is extended beyond the commonly-studied polytropic ideal gas to more realistic equations of state (EOS) including the stiff gas, the Nobel-Abel gas, and the Carnahan-Starling hard-sphere fluid, thus enabling verification studies to be performed on more physically-realistic fluids. Exact solutions are compared with numerical results obtained from the Lagrangian hydrocode FLAG, developed at Los Alamos. For these more realistic EOSs, the simulation errors decreased in magnitude both at the origin and at the shock, but also spread more broadly about these points compared to the ideal EOS. The overall spatial convergence rate remained first order.

Magnetohydrodynamic Jump Conditions for Oblique Relativistic Shocks with Gyrotropic Pressure

NASA Technical Reports Server (NTRS)

Double, Glen P.; Baring, Matthew G.; Jones, Frank C.; Ellison, Donald C.

2003-01-01

Shock jump conditions, i.e., the specification of the downstream parameters of the gas in terms of the upstream parameters, are obtained for steady-state, plane shocks with oblique magnetic fields and arbitrary flow speeds. This is done by combining the continuity of particle number flux and the electromagnetic boundary conditions at the shock with the magnetohydrodynamic conservation laws derived from the stress-energy tensor. For ultrarelativistic and nonrelativistic shocks, the jump conditions may be solved analytically. For mildly relativistic shocks, analytic solutions are obtained for isotropic pressure using an approximation for the adiabatic index that is valid in high sonic Mach number cases. Examples assuming isotropic pressure illustrate how the shock compression ratio depends on the shock speed and obliquity. In the more general case of gyrotropic pressure, the jump conditions cannot be solved analytically with- out additional assumptions, and the effects of gyrotropic pressure are investigated by parameterizing the distribution of pressure parallel and perpendicular to the magnetic field. Our numerical solutions reveal that relatively small departures from isotropy (e.g., approximately 20%) produce significant changes in the shock compression ratio, r , at all shock Lorentz factors, including ultrarelativistic ones, where an analytic solution with gyrotropic pressure is obtained. In particular, either dynamically important fields or significant pressure anisotropies can incur marked departures from the canonical gas dynamic value of r = 3 for a shocked ultrarelativistic flow and this may impact models of particle acceleration in gamma-ray bursts and other environments where relativistic shocks are inferred. The jump conditions presented apply directly to test-particle acceleration, and will facilitate future self-consistent numerical modeling of particle acceleration at oblique, relativistic shocks; such models include the modification of the fluid velocity profile due to the contribution of energetic particles to the momentum and energy fluxes.

Generalized Sagdeev potential theory for shock waves modeling

NASA Astrophysics Data System (ADS)

Akbari-Moghanjoughi, M.

2017-05-01

In this paper, we develop an innovative approach to study the shock wave propagation using the Sagdeev potential method. We also present an analytical solution for Korteweg de Vries Burgers (KdVB) and modified KdVB equation families with a generalized form of the nonlinearity term which agrees well with the numerical one. The novelty of the current approach is that it is based on a simple analogy of the particle in a classical potential with the variable particle energy providing one with a deeper physical insight into the problem and can easily be extended to more complex physical situations. We find that the current method well describes both monotonic and oscillatory natures of the dispersive-diffusive shock structures in different viscous fluid configurations. It is particularly important that all essential parameters of the shock structure can be deduced directly from the Sagdeev potential in small and large potential approximation regimes. Using the new method, we find that supercnoidal waves can decay into either compressive or rarefactive shock waves depending on the initial wave amplitude. Current investigation provides a general platform to study a wide range of phenomena related to nonlinear wave damping and interactions in diverse fluids including plasmas.

Electromotive force in strongly compressible magnetohydrodynamic turbulence

NASA Astrophysics Data System (ADS)

Yokoi, N.

2017-12-01

Variable density fluid turbulence is ubiquitous in geo-fluids, not to mention in astrophysics. Depending on the source of density variation, variable density fluid turbulence may be divided into two categories: the weak compressible (entropy mode) turbulence for slow flow and the strong compressible (acoustic mode) turbulence for fast flow. In the strong compressible turbulence, the pressure fluctuation induces a strong density fluctuation ρ ', which is represented by the density variance <ρ'2> (<·> denotes the ensemble average). The turbulent effect on the large-scale magnetic-field B induction is represented by the turbulent electromotive force (EMF) (u': velocity fluctuation, b': magnetic-field fluctuation). In the usual treatment in the dynamo theory, the expression for the EMF has been obtained in the framework of incompressible or weak compressible turbulence, where only the variation of the mean density <ρ>, if any, is taken into account. We see from the equation of the density fluctuation ρ', the density variance <ρ'2> is generated by the large mean density variation ∂<ρ> coupled with the turbulent mass flux <ρ'u'>. This means that in the region where the mean density steeply changes, the density variance effect becomes relevant for the magnetic field evolution. This situation is typically the case for phenomena associated with shocks and compositional discontinuities. With the aid of the analytical theory of inhomogeneous compressible magnetohydrodynamic (MHD) turbulence, the expression for the turbulent electromotive force is investigated. It is shown that, among others, an obliqueness (misalignment) between the mean density gradient ∂<ρ> and the mean magnetic field B may contribute to the EMF as ≈χ B×∂<ρ> with the turbulent transport coefficient χ proportional to the density variance (χ <ρ'2>). This density variance effect is expected to strongly affect the EMF near the interface, and changes the transport properties of turbulence. In the case of an interface under the MHD slow shock, the magnetic reconnection rate may be enhanced by this effect. Physical origin of this effect is discussed in some possible geophysical applications.

Steady state and dynamical structure of a cosmic-ray-modified termination shock

NASA Technical Reports Server (NTRS)

Donohue, D. J.; Zank, G. P.

1993-01-01

A hydrodynamic model is developed for the structure of a cosmic-ray-modified termination shock. The model is based on the two-fluid equations of diffuse shock acceleration (Drury and Volk, 1981). Both the steady state structure of the shock and its interaction with outer heliospheric disturbances are considered. Under the assumption that the solar wind is decelerated by diffusing interstellar cosmic rates, it is shown that the natural state of the termination shock is a gradual deceleration and compression, followed by a discontinuous jump to a downstream state which is dominated by the pressure contribution of the cosmic rays. A representative model is calculated for the steady state which incorporates both interstellar cosmic ray mediation and diffusively accelerated anomalous ions through a proposed thermal leakage mechanism. The interaction of large-scale disturbances with the equilibrium termination shock model is shown to result in some unusual downstream structure, including transmitted shocks and cosmic-ray-modified contact discontinuities. The structure observed may be connected to the 2-kHz outer heliospheric radio emission (Cairns et al., 1992a, b). The time-dependent simulations also demonstrate that interaction with solar wind compressible turbulence (e.g., traveling interplanetary shocks, etc.) could induce the termination shock to continually fluctuate between cosmic-ray-dominated and gas-dynamic states. This fluctuation may represent a partial explanation of the galactic cosmic ray modulation effect and illustrates that the Pioneer and Voyager satellites will encounter an evolving shock whose structure and dynamic properties are strongly influence by the mediation of interstellar and anomalous cosmic rays.

Steady state and dynamical structure of a cosmic-ray-modified termination shock

NASA Astrophysics Data System (ADS)

Donohue, D. J.; Zank, G. P.

1993-11-01

A hydrodynamic model is developed for the structure of a cosmic-ray-modified termination shock. The model is based on the two-fluid equations of diffuse shock acceleration (Drury and Volk, 1981). Both the steady state structure of the shock and its interaction with outer heliospheric disturbances are considered. Under the assumption that the solar wind is decelerated by diffusing interstellar cosmic rates, it is shown that the natural state of the termination shock is a gradual deceleration and compression, followed by a discontinuous jump to a downstream state which is dominated by the pressure contribution of the cosmic rays. A representative model is calculated for the steady state which incorporates both interstellar cosmic ray mediation and diffusively accelerated anomalous ions through a proposed thermal leakage mechanism. The interaction of large-scale disturbances with the equilibrium termination shock model is shown to result in some unusual downstream structure, including transmitted shocks and cosmic-ray-modified contact discontinuities. The structure observed may be connected to the 2-kHz outer heliospheric radio emission (Cairns et al., 1992a, b). The time-dependent simulations also demonstrate that interaction with solar wind compressible turbulence (e.g., traveling interplanetary shocks, etc.) could induce the termination shock to continually fluctuate between cosmic-ray-dominated and gas-dynamic states. This fluctuation may represent a partial explanation of the galactic cosmic ray modulation effect and illustrates that the Pioneer and Voyager satellites will encounter an evolving shock whose structure and dynamic properties are strongly influence by the mediation of interstellar and anomalous cosmic rays.

Experimental exploration of underexpanded supersonic jets

NASA Astrophysics Data System (ADS)

André, Benoît; Castelain, Thomas; Bailly, Christophe

2014-01-01

Two underexpanded free jets at fully expanded Mach numbers = 1.15 and 1.50 are studied. Schlieren visualizations as well as measurements of static pressure, Pitot pressure and velocity are performed. All these experimental techniques are associated to obtain an accurate picture of the jet flow development. In particular, expansion, compression and neutral zones have been identified in each shock cell. Particle lag is considered by integrating the equation of motion for particles in a fluid flow and it is found that the laser Doppler velocimetry is suitable for investigating shock-containing jets. Even downstream of the normal shock arising in the = 1.50 jet, the measured gradual velocity decrease is shown to be relevant.

Solitonic Dispersive Hydrodynamics: Theory and Observation

NASA Astrophysics Data System (ADS)

Maiden, Michelle D.; Anderson, Dalton V.; Franco, Nevil A.; El, Gennady A.; Hoefer, Mark A.

2018-04-01

Ubiquitous nonlinear waves in dispersive media include localized solitons and extended hydrodynamic states such as dispersive shock waves. Despite their physical prominence and the development of thorough theoretical and experimental investigations of each separately, experiments and a unified theory of solitons and dispersive hydrodynamics are lacking. Here, a general soliton-mean field theory is introduced and used to describe the propagation of solitons in macroscopic hydrodynamic flows. Two universal adiabatic invariants of motion are identified that predict trapping or transmission of solitons by hydrodynamic states. The result of solitons incident upon smooth expansion waves or compressive, rapidly oscillating dispersive shock waves is the same, an effect termed hydrodynamic reciprocity. Experiments on viscous fluid conduits quantitatively confirm the soliton-mean field theory with broader implications for nonlinear optics, superfluids, geophysical fluids, and other dispersive hydrodynamic media.

Dynamic compression of dense oxide (Gd3Ga5O12) from 0.4 to 2.6 TPa: Universal Hugoniot of fluid metals

PubMed Central

Ozaki, N.; Nellis, W. J.; Mashimo, T.; Ramzan, M.; Ahuja, R.; Kaewmaraya, T.; Kimura, T.; Knudson, M.; Miyanishi, K.; Sakawa, Y.; Sano, T.; Kodama, R.

2016-01-01

Materials at high pressures and temperatures are of great current interest for warm dense matter physics, planetary sciences, and inertial fusion energy research. Shock-compression equation-of-state data and optical reflectivities of the fluid dense oxide, Gd3Ga5O12 (GGG), were measured at extremely high pressures up to 2.6 TPa (26 Mbar) generated by high-power laser irradiation and magnetically-driven hypervelocity impacts. Above 0.75 TPa, the GGG Hugoniot data approach/reach a universal linear line of fluid metals, and the optical reflectivity most likely reaches a constant value indicating that GGG undergoes a crossover from fluid semiconductor to poor metal with minimum metallic conductivity (MMC). These results suggest that most fluid compounds, e.g., strong planetary oxides, reach a common state on the universal Hugoniot of fluid metals (UHFM) with MMC at sufficiently extreme pressures and temperatures. The systematic behaviors of warm dense fluid would be useful benchmarks for developing theoretical equation-of-state and transport models in the warm dense matter regime in determining computational predictions. PMID:27193942

Dynamic compression of dense oxide (Gd 3Ga 5O 12) from 0.4 to 2.6 TPa: Universal Hugoniot of fluid metals

DOE PAGES

Ozaki, N.; Nellis, W. J.; Mashimo, T.; ...

2016-05-19

Materials at high pressures and temperatures are of great current interest for warm dense matter physics, planetary sciences, and inertial fusion energy research. Shock-compression equation-of-state data and optical reflectivities of the fluid dense oxide, Gd 3Ga 5O 12 (GGG), were measured at extremely high pressures up to 2.6 TPa (26 Mbar) generated by high-power laser irradiation and magnetically-driven hypervelocity impacts. Above 0.75 TPa, the GGG Hugoniot data approach/reach a universal linear line of fluid metals, and the optical reflectivity most likely reaches a constant value indicating that GGG undergoes a crossover from fluid semiconductor to poor metal with minimum metallicmore » conductivity (MMC). These results suggest that most fluid compounds, e.g., strong planetary oxides, reach a common state on the universal Hugoniot of fluid metals (UHFM) with MMC at sufficiently extreme pressures and temperatures. Lastly, the systematic behaviors of warm dense fluid would be useful benchmarks for developing theoretical equation-of-state and transport models in the warm dense matter regime in determining computational predictions.« less

Dynamic compression of dense oxide (Gd3Ga5O12) from 0.4 to 2.6 TPa: Universal Hugoniot of fluid metals.

PubMed

Ozaki, N; Nellis, W J; Mashimo, T; Ramzan, M; Ahuja, R; Kaewmaraya, T; Kimura, T; Knudson, M; Miyanishi, K; Sakawa, Y; Sano, T; Kodama, R

2016-05-19

Materials at high pressures and temperatures are of great current interest for warm dense matter physics, planetary sciences, and inertial fusion energy research. Shock-compression equation-of-state data and optical reflectivities of the fluid dense oxide, Gd3Ga5O12 (GGG), were measured at extremely high pressures up to 2.6 TPa (26 Mbar) generated by high-power laser irradiation and magnetically-driven hypervelocity impacts. Above 0.75 TPa, the GGG Hugoniot data approach/reach a universal linear line of fluid metals, and the optical reflectivity most likely reaches a constant value indicating that GGG undergoes a crossover from fluid semiconductor to poor metal with minimum metallic conductivity (MMC). These results suggest that most fluid compounds, e.g., strong planetary oxides, reach a common state on the universal Hugoniot of fluid metals (UHFM) with MMC at sufficiently extreme pressures and temperatures. The systematic behaviors of warm dense fluid would be useful benchmarks for developing theoretical equation-of-state and transport models in the warm dense matter regime in determining computational predictions.

MacCormack's technique-based pressure reconstruction approach for PIV data in compressible flows with shocks

NASA Astrophysics Data System (ADS)

Liu, Shun; Xu, Jinglei; Yu, Kaikai

2017-06-01

This paper proposes an improved approach for extraction of pressure fields from velocity data, such as obtained by particle image velocimetry (PIV), especially for steady compressible flows with strong shocks. The principle of this approach is derived from Navier-Stokes equations, assuming adiabatic condition and neglecting viscosity of flow field boundaries measured by PIV. The computing method is based on MacCormack's technique in computational fluid dynamics. Thus, this approach is called the MacCormack method. Moreover, the MacCormack method is compared with several approaches proposed in previous literature, including the isentropic method, the spatial integration and the Poisson method. The effects of velocity error level and PIV spatial resolution on these approaches are also quantified by using artificial velocity data containing shock waves. The results demonstrate that the MacCormack method has higher reconstruction accuracy than other approaches, and its advantages become more remarkable with shock strengthening. Furthermore, the performance of the MacCormack method is also validated by using synthetic PIV images with an oblique shock wave, confirming the feasibility and advantage of this approach in real PIV experiments. This work is highly significant for the studies on aerospace engineering, especially the outer flow fields of supersonic aircraft and the internal flow fields of ramjets.

Nonstandard Analysis and Shock Wave Jump Conditions in a One-Dimensional Compressible Gas

NASA Technical Reports Server (NTRS)

Baty, Roy S.; Farassat, Fereidoun; Hargreaves, John

2007-01-01

Nonstandard analysis is a relatively new area of mathematics in which infinitesimal numbers can be defined and manipulated rigorously like real numbers. This report presents a fairly comprehensive tutorial on nonstandard analysis for physicists and engineers with many examples applicable to generalized functions. To demonstrate the power of the subject, the problem of shock wave jump conditions is studied for a one-dimensional compressible gas. It is assumed that the shock thickness occurs on an infinitesimal interval and the jump functions in the thermodynamic and fluid dynamic parameters occur smoothly across this interval. To use conservations laws, smooth pre-distributions of the Dirac delta measure are applied whose supports are contained within the shock thickness. Furthermore, smooth pre-distributions of the Heaviside function are applied which vary from zero to one across the shock wave. It is shown that if the equations of motion are expressed in nonconservative form then the relationships between the jump functions for the flow parameters may be found unambiguously. The analysis yields the classical Rankine-Hugoniot jump conditions for an inviscid shock wave. Moreover, non-monotonic entropy jump conditions are obtained for both inviscid and viscous flows. The report shows that products of generalized functions may be defined consistently using nonstandard analysis; however, physically meaningful products of generalized functions must be determined from the physics of the problem and not the mathematical form of the governing equations.

Cardiorespiratory interactions and blood flow generation during cardiac arrest and other states of low blood flow.

PubMed

Sigurdsson, Gardar; Yannopoulos, Demetris; McKnite, Scott H; Lurie, Keith G

2003-06-01

Recent advances in cardiopulmonary resuscitation have shed light on the importance of cardiorespiratory interactions during shock and cardiac arrest. This review focuses on recently published studies that evaluate factors that determine preload during chest compression, methods that can augment preload, and the detrimental effects of hyperventilation and interrupting chest compressions. Refilling of the ventricles, so-called ventricular preload, is diminished during cardiovascular collapse and resuscitation from cardiac arrest. In light of the potential detrimental effects and challenges of large-volume fluid resuscitations, other methods have increasing importance. During cardiac arrest, active decompression of the chest and impedance of inspiratory airflow during the recoil of the chest work by increasing negative intrathoracic pressure and, hence, increase refilling of the ventricles and increase cardiac preload, with improvement in survival. Conversely, increased frequency of ventilation has detrimental effects on coronary perfusion pressure and survival rates in cardiac arrest and severe shock. Prolonged interruption of chest compressions for delivering single-rescuer ventilation or analyzing rhythm before shock delivery is associated with decreased survival rate. Cardiorespiratory interactions are of profound importance in states of cardiovascular collapse in which increased negative intrathoracic pressure during decompression of the chest has a favorable effect and increased intrathoracic pressure with ventilation has a detrimental effect on survival rate.

Treatment of Viscosity in the Shock Waves Observed After Two Consecutive Coronal Mass Ejection Activities CME08/03/2012 and CME15/03/2012

NASA Astrophysics Data System (ADS)

Cavus, Huseyin

2016-11-01

A coronal mass ejection (CME) is one of the most the powerful activities of the Sun. There is a possibility to produce shocks in the interplanetary medium after CMEs. Shock waves can be observed when the solar wind changes its velocity from being supersonic nature to being subsonic nature. The investigations of such activities have a central place in space weather purposes, since; the interaction of shocks with viscosity is one of the most important problems in the supersonic and compressible gas flow regime (Blazek in Computational fluid dynamics: principles and applications. Elsevier, Amsterdam 2001). The main aim of present work is to achieve a search for the viscosity effects in the shocks occurred after two consecutive coronal mass ejection activities in 2012 (i.e. CME08/03/2012 and CME15/03/2012).

Analytical scalings of the linear Richtmyer-Meshkov instability when a shock is reflected.

PubMed

Campos, F Cobos; Wouchuk, J G

2016-05-01

When a planar shock hits a corrugated contact surface between two fluids, hydrodynamic perturbations are generated in both fluids that result in asymptotic normal and tangential velocity perturbations in the linear stage, the so called Richtmyer-Meshkov instability. In this work, explicit and exact analytical expansions of the asymptotic normal velocity (δv_{i}^{∞}) are presented for the general case in which a shock is reflected back. The expansions are derived from the conservation equations and take into account the whole perturbation history between the transmitted and reflected fronts. The important physical limits of weak and strong shocks and the high/low preshock density ratio at the contact surface are shown. An approximate expression for the normal velocity, valid even for high compression regimes, is given. A comparison with recent experimental data is done. The contact surface ripple growth is studied during the linear phase showing good agreement between theory and experiments done in a wide range of incident shock Mach numbers and preshock density ratios, for the cases in which the initial ripple amplitude is small enough. In particular, it is shown that in the linear asymptotic phase, the contact surface ripple (ψ_{i}) grows as ψ_{∞}+δv_{i}^{∞}t, where ψ_{∞} is an asymptotic ordinate different from the postshock ripple amplitude at t=0+. This work is a continuation of the calculations of F. Cobos Campos and J. G. Wouchuk, [Phys. Rev. E 90, 053007 (2014)PLEEE81539-375510.1103/PhysRevE.90.053007] for a single shock moving into one fluid.

The 3D Navier-Stokes analysis of a Mach 2.68 bifurcated rectangular mixed-compression inlet

NASA Technical Reports Server (NTRS)

Mizukami, M.; Saunders, J. D.

1995-01-01

The supersonic diffuser of a Mach 2.68 bifurcated, rectangular, mixed-compression inlet was analyzed using a three-dimensional (3D) Navier-Stokes flow solver. A two-equation turbulence model, and a porous bleed model based on unchoked bleed hole discharge coefficients were used. Comparisons were made with experimental data, inviscid theory, and two-dimensional Navier-Stokes analyses. The main objective was to gain insight into the inlet fluid dynamics. Examination of the computational results along with the experimental data suggest that the cowl shock-sidewall boundary layer interaction near the leading edge caused a substantial separation in the wind tunnel inlet model. As a result, the inlet performance may have been compromised by increased spillage and higher bleed mass flow requirements. The internal flow contained substantial waves that were not in the original inviscid design. 3D effects were fairly minor for this inlet at on-design conditions. Navier-Stokes analysis appears to be an useful tool for gaining insight into the inlet fluid dynamics. It provides a higher fidelity simulation of the flowfield than the original inviscid design, by taking into account boundary layers, porous bleed, and their interactions with shock waves.

Hypersonic flow analysis

NASA Technical Reports Server (NTRS)

Chow, Chuen-Yen; Ryan, James S.

1987-01-01

While the zonal grid system of Transonic Navier-Stokes (TNS) provides excellent modeling of complex geometries, improved shock capturing, and a higher Mach number range will be required if flows about hypersonic aircraft are to be modeled accurately. A computational fluid dynamics (CFD) code, the Compressible Navier-Stokes (CNS), is under development to combine the required high Mach number capability with the existing TNS geometry capability. One of several candidate flow solvers for inclusion in the CNS is that of F3D. This upwinding flow solver promises improved shock capturing, and more accurate hypersonic solutions overall, compared to the solver currently used in TNS.

Numerical simulation of fluid flow around a scramaccelerator projectile

NASA Technical Reports Server (NTRS)

Pepper, Darrell W.; Humphrey, Joseph W.; Sobota, Thomas H.

1991-01-01

Numerical simulations of the fluid motion and temperature distribution around a 'scramaccelerator' projectile are obtained for Mach numbers in the 5-10 range. A finite element method is used to solve the equations of motion for inviscid and viscous two-dimensional or axisymmetric compressible flow. The time-dependent equations are solved explicitly, using bilinear isoparametric quadrilateral elements, mass lumping, and a shock-capturing Petrov-Galerkin formulation. Computed results indicate that maintaining on-design performance for controlling and stabilizing oblique detonation waves is critically dependent on projectile shape and Mach number.

In vitro study of the mechanical effects of shock-wave lithotripsy.

PubMed

Howard, D; Sturtevant, B

1997-01-01

Impulsive stress in repeated shock waves administered during extracorporeal shock-wave lithotripsy (ESWL) causes injury to kidney tissue. In a study of the mechanical input of ESWL, the effects of focused shock waves on thin planar polymeric membranes immersed in a variety of tissue-mimicking fluids have been examined. A direct mechanism of failure by shock compression and an indirect mechanism by bubble collapse have been observed. Thin membranes are easily damaged by bubble collapse. After propagating through cavitation-free acoustically heterogeneous media (liquids mixed with hollow glass spheres, and tissue) shock waves cause membranes to fail in fatigue by a shearing mechanism. As is characteristic of dynamic fatigue, the failure stress increases with strain rate, determined by the amplitude and rise time of the attenuated shock wave. Shocks with large amplitude and short rise time (i.e., in uniform media) cause no damage. Thus the inhomogeneity of tissue is likely to contribute to injury in ESWL. A definition of dose is proposed which yields a criterion for damage based on measurable shock wave properties.

Dispersive MHD Shock Properties and Interactions with Alfven Solitons

NASA Astrophysics Data System (ADS)

Hamilton, R.; Toll, K.; Ellis, C.

2017-12-01

The weakly nonlinear, weakly dispersive limit of Hall MHD with resistivity for 1D waves travelling nearly parallel to the ambient magnetic field reduces to the derivative nonlinear Schrödinger-Burgers (DNLSB) equation. This model equation describes the coupling between the Alfvenic and magnetosonic modes for a low b plasma. Without dissipation this model equation reduces to the DNLS which can be solved as an initial value problem using the Inverse Scattering Transformation through which the nonlinear component of the magnetic field profile can be represented as a combination of one-parameter bright and dark solitons as well as two-parameter solitons. The one-parameter solitons are constrained to travel at speeds ranging between the Alfvenic and magnetosonic characteristic speeds of the ambient field. We have found that these one-parameter solitons are effectively bound to a 1-2 Fast Shock and will pass back and forth across the shock until they are damped away with no apparent effect on the Fast Shock. A similar mechanism is expected for a sufficiently compressive Intermediate Shock as it arises simply from two effects: damping of a one-parameter soliton causes it to speed up and, if it does not damp away, it will eventually overtake the shock; passing forwards through a compressive shock the decrease of the field strength leads to a slowing of the soliton. We also discuss an extension of results [C. F. Kennel, R. D. Blandford, C. C. Wu, Phys. Fluids B 2(2), 1990] related to the time dependence of Intermediate Shocks in the presence of dispersion.

Diffuse-Interface Capturing Methods for Compressible Two-Phase Flows

NASA Astrophysics Data System (ADS)

Saurel, Richard; Pantano, Carlos

2018-01-01

Simulation of compressible flows became a routine activity with the appearance of shock-/contact-capturing methods. These methods can determine all waves, particularly discontinuous ones. However, additional difficulties may appear in two-phase and multimaterial flows due to the abrupt variation of thermodynamic properties across the interfacial region, with discontinuous thermodynamical representations at the interfaces. To overcome this difficulty, researchers have developed augmented systems of governing equations to extend the capturing strategy. These extended systems, reviewed here, are termed diffuse-interface models, because they are designed to compute flow variables correctly in numerically diffused zones surrounding interfaces. In particular, they facilitate coupling the dynamics on both sides of the (diffuse) interfaces and tend to the proper pure fluid-governing equations far from the interfaces. This strategy has become efficient for contact interfaces separating fluids that are governed by different equations of state, in the presence or absence of capillary effects, and with phase change. More sophisticated materials than fluids (e.g., elastic-plastic materials) have been considered as well.

Optimal sensor placement for control of a supersonic mixed-compression inlet with variable geometry

NASA Astrophysics Data System (ADS)

Moore, Kenneth Thomas

A method of using fluid dynamics models for the generation of models that are useable for control design and analysis is investigated. The problem considered is the control of the normal shock location in the VDC inlet, which is a mixed-compression, supersonic, variable-geometry inlet of a jet engine. A quasi-one-dimensional set of fluid equations incorporating bleed and moving walls is developed. An object-oriented environment is developed for simulation of flow systems under closed-loop control. A public interface between the controller and fluid classes is defined. A linear model representing the dynamics of the VDC inlet is developed from the finite difference equations, and its eigenstructure is analyzed. The order of this model is reduced using the square root balanced model reduction method to produce a reduced-order linear model that is suitable for control design and analysis tasks. A modification to this method that improves the accuracy of the reduced-order linear model for the purpose of sensor placement is presented and analyzed. The reduced-order linear model is used to develop a sensor placement method that quantifies as a function of the sensor location the ability of a sensor to provide information on the variable of interest for control. This method is used to develop a sensor placement metric for the VDC inlet. The reduced-order linear model is also used to design a closed loop control system to control the shock position in the VDC inlet. The object-oriented simulation code is used to simulate the nonlinear fluid equations under closed-loop control.

Quasi 1D Modeling of Mixed Compression Supersonic Inlets

NASA Technical Reports Server (NTRS)

Kopasakis, George; Connolly, Joseph W.; Paxson, Daniel E.; Woolwine, Kyle J.

2012-01-01

The AeroServoElasticity task under the NASA Supersonics Project is developing dynamic models of the propulsion system and the vehicle in order to conduct research for integrated vehicle dynamic performance. As part of this effort, a nonlinear quasi 1-dimensional model of the 2-dimensional bifurcated mixed compression supersonic inlet is being developed. The model utilizes computational fluid dynamics for both the supersonic and subsonic diffusers. The oblique shocks are modeled utilizing compressible flow equations. This model also implements variable geometry required to control the normal shock position. The model is flexible and can also be utilized to simulate other mixed compression supersonic inlet designs. The model was validated both in time and in the frequency domain against the legacy LArge Perturbation INlet code, which has been previously verified using test data. This legacy code written in FORTRAN is quite extensive and complex in terms of the amount of software and number of subroutines. Further, the legacy code is not suitable for closed loop feedback controls design, and the simulation environment is not amenable to systems integration. Therefore, a solution is to develop an innovative, more simplified, mixed compression inlet model with the same steady state and dynamic performance as the legacy code that also can be used for controls design. The new nonlinear dynamic model is implemented in MATLAB Simulink. This environment allows easier development of linear models for controls design for shock positioning. The new model is also well suited for integration with a propulsion system model to study inlet/propulsion system performance, and integration with an aero-servo-elastic system model to study integrated vehicle ride quality, vehicle stability, and efficiency.

The importance of electrothermal terms in Ohm's law for magnetized spherical implosions

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

Davies, J. R., E-mail: jdav@lle.rochester.edu; Betti, R.; Chang, P.-Y.

2015-11-15

The magnetohydrodynamics (MHD) of magnetic-field compression in laser-driven spherical targets is considered. Magnetic-field evolution is cast in terms of an effective fluid velocity, a convective term resulting from resistivity gradients, a resistive diffusion term, and a source term. Effective velocity is the sum of fluid velocity, drift velocity, and heat-flux velocity, given by electron heat flux divided by electron enthalpy density, which has two components: the perpendicular or Nernst velocity and the cross-field velocity. The Nernst velocity compresses the magnetic field as the heat front moves into gas. The cross-field velocity leads to dynamo generation of an azimuthal magnetic field.more » It is proposed that the heat-flux velocity should be flux limited using a “Nernst” flux limiter independent of the thermal flux limiter but should not exceed it. The addition of the MHD routines to the 1D, Lagrangian hydrocode LILAC and the Eulerian version of the 2D hydrocode DRACO is described, and the codes are used to model a magnetized spherical compression on the OMEGA laser. Thermal flux limiting at a shock front is found to cause unphysical electron temperature gradients that lead to large, unphysical magnetic fields caused by the resistivity gradient, so thermal flux limiting in the gas is removed. The Nernst term reduces the benefits of magnetization in inertial fusion. A Nernst flux limiter ≤0.12 is required in the gas in order to agree with measured neutron yield and increases in the neutron-averaged ion temperature caused by magnetization. This corresponds to preventing the Nernst velocity from exceeding the shock velocity, which prevents significant decoupling of the magnetic field and gas compression.« less

The importance of electrothermal terms in Ohm's law for magnetized spherical implosions

DOE PAGES

Davies, J. R.; Betti, R.; Chang, P. -Y.; ...

2015-11-06

The magnetohydrodynamics (MHD) of magnetic-field compression in laser-driven spherical targets is considered. Magnetic-field evolution is cast in terms of an effective fluid velocity, a convective term resulting from resistivity gradients, a resistive diffusion term, and a source term. Effective velocity is the sum of fluid velocity, drift velocity, and heat-flux velocity, given by electron heat flux divided by electron enthalpy density, which has two components: the perpendicular or Nernst velocity and the cross-field velocity. The Nernst velocity compresses the magnetic field as a heat front moves into the gas. The cross-field velocity leads to dynamo generation of an azimuthal magneticmore » field. It is proposed that the heat-flux velocity should be flux limited using a “Nernst” flux limiter independent of the thermal flux limiter but should not exceed it. The addition of MHD routines to the 1-D, Lagrangian hydrocode LILAC and the Eulerian version of the 2-D hydrocode DRACO is described, and the codes are used to model a magnetized spherical compression on the OMEGA laser. Thermal flux limiting at a shock front is found to cause unphysical electron temperature gradients that lead to large, unphysical magnetic fields caused by the resistivity gradient, so thermal flux limiting in the gas is removed. The Nernst term reduces the benefits of magnetization in inertial fusion. In addition, a Nernst flux limiter ≤ 0.12 is required in the gas in order to agree with measured neutron yield and increases in the neutron-averaged ion temperature caused by magnetization. This corresponds to maintaining the Nernst velocity below the shock velocity, which prevents significant decoupling of the magnetic field and gas compression.« less

Interactions of solitary waves and compression/expansion waves in core-annular flows

NASA Astrophysics Data System (ADS)

Maiden, Michelle; Anderson, Dalton; El, Gennady; Franco, Nevil; Hoefer, Mark

2017-11-01

The nonlinear hydrodynamics of an initial step leads to the formation of rarefaction waves and dispersive shock waves in dispersive media. Another hallmark of these media is the soliton, a localized traveling wave whose speed is amplitude dependent. Although compression/expansion waves and solitons have been well-studied individually, there has been no mathematical description of their interaction. In this talk, the interaction of solitons and shock/rarefaction waves for interfacial waves in viscous, miscible core-annular flows are modeled mathematically and explored experimentally. If the interior fluid is continuously injected, a deformable conduit forms whose interfacial dynamics are well-described by a scalar, dispersive nonlinear partial differential equation. The main focus is on interactions of solitons with dispersive shock waves and rarefaction waves. Theory predicts that a soliton can either be transmitted through or trapped by the extended hydrodynamic state. The notion of reciprocity is introduced whereby a soliton interacts with a shock wave in a reciprocal or dual fashion as with the rarefaction. Soliton reciprocity, trapping, and transmission are observed experimentally and are found to agree with the modulation theory and numerical simulations. This work was partially supported by NSF CAREER DMS-1255422 (M.A.H.) and NSF GRFP (M.D.M.).

Hugoniot measurements of double-shocked precompressed dense xenon plasmas

NASA Astrophysics Data System (ADS)

Zheng, J.; Chen, Q. F.; Gu, Y. J.; Chen, Z. Y.

2012-12-01

The current partially ionized plasmas models for xenon show substantial differences since the description of pressure and thermal ionization region becomes a formidable task, prompting the need for an improved understanding of dense xenon plasmas behavior at above 100 GPa. We performed double-shock compression experiments on dense xenon to determine accurately the Hugoniot up to 172 GPa using a time-resolved optical radiation method. The planar strong shock wave was produced using a flyer plate impactor accelerated up to ˜6 km/s with a two-stage light-gas gun. The time-resolved optical radiation histories were acquired by using a multiwavelength channel optical transience radiance pyrometer. Shock velocity was measured and mass velocity was determined by the impedance-matching methods. The experimental equation of state of dense xenon plasmas are compared with the self-consistent fluid variational calculations of dense xenon in the region of partial ionization over a wide range of pressures and temperatures.

Structure of shock compressed model basaltic glass: Insights from O K-edge X-ray Raman scattering and high-resolution 27Al NMR spectroscopy

NASA Astrophysics Data System (ADS)

Lee, Sung Keun; Park, Sun Young; Kim, Hyo-Im; Tschauner, Oliver; Asimow, Paul; Bai, Ligang; Xiao, Yuming; Chow, Paul

2012-03-01

The detailed atomic structures of shock compressed basaltic glasses are not well understood. Here, we explore the structures of shock compressed silicate glass with a diopside-anorthite eutectic composition (Di64An36), a common Fe-free model basaltic composition, using oxygen K-edge X-ray Raman scattering and high- resolution 27Al solid-state NMR spectroscopy and report previously unknown details of shock-induced changes in the atomic configurations. A topologically driven densification of the Di64An36 glass is indicated by the increase in oxygen K-edge energy for the glass upon shock compression. The first experimental evidence of the increase in the fraction of highly coordinated Al in shock compressed glass is found in the 27Al NMR spectra. This unambiguous evidence of shock-induced changes in Al coordination environments provides atomistic insights into shock compression in basaltic glasses and allows us to microscopically constrain the magnitude of impact events or relevant processes involving natural basalts on Earth and planetary surfaces.

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.

Viscous flow computations using a second-order upwind differencing scheme

NASA Technical Reports Server (NTRS)

Chen, Y. S.

1988-01-01

In the present computations of a wide range of fluid flow problems by means of the primitive variables-incorporating Navier-Stokes equations, a mixed second-order upwinding scheme approximates the convective terms of the transport equations and the scheme's accuracy is verified for convection-dominated high Re number flow problems. An adaptive dissipation scheme is used as a monotonic supersonic shock flow capture mechanism. Many benchmark fluid flow problems, including the compressible and incompressible, laminar and turbulent, over a wide range of M and Re numbers, are presently studied to verify the accuracy and robustness of this numerical method.

Thermal and Mechanical Non-equilibrium Effects on Turbulent Flows Fundamental Studies of Energy Exchanges Through Direct Numerical Simulations and Experiments

DTIC Science & Technology

2013-10-21

AFOSR-2012-0001, 2012. Chu, B., and Kovásznay, L . S . G ., “Non-linear Interactions in a Viscous Heat-Conducting Compressible Gas,” Journal of Fluid...229-247. Kovásznay, L . S . G ., “Turbulence in Supersonic Flow,” Journal of the Aeronautical Sciences, Vol. 20, No. 10, 1953, pp. 657-674, 682. Larsson...Interactions,” Annual Review of Fluid Mechanics, Vol. 32, 2000, pp. 309-345. Barre, S ., Alem, D., and Bonnet, J. P ., “Experimental Study of a Normal Shock

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.

Three-dimensional lattice Boltzmann model for compressible flows.

PubMed

Sun, Chenghai; Hsu, Andrew T

2003-07-01

A three-dimensional compressible lattice Boltzmann model is formulated on a cubic lattice. A very large particle-velocity set is incorporated in order to enable a greater variation in the mean velocity. Meanwhile, the support set of the equilibrium distribution has only six directions. Therefore, this model can efficiently handle flows over a wide range of Mach numbers and capture shock waves. Due to the simple form of the equilibrium distribution, the fourth-order velocity tensors are not involved in the formulation. Unlike the standard lattice Boltzmann model, no special treatment is required for the homogeneity of fourth-order velocity tensors on square lattices. The Navier-Stokes equations were recovered, using the Chapman-Enskog method from the Bhatnagar-Gross-Krook (BGK) lattice Boltzmann equation. The second-order discretization error of the fluctuation velocity in the macroscopic conservation equation was eliminated by means of a modified collision invariant. The model is suitable for both viscous and inviscid compressible flows with or without shocks. Since the present scheme deals only with the equilibrium distribution that depends only on fluid density, velocity, and internal energy, boundary conditions on curved wall are easily implemented by an extrapolation of macroscopic variables. To verify the scheme for inviscid flows, we have successfully simulated a three-dimensional shock-wave propagation in a box and a normal shock of Mach number 10 over a wedge. As an application to viscous flows, we have simulated a flat plate boundary layer flow, flow over a cylinder, and a transonic flow over a NACA0012 airfoil cascade.

Optical Radiation from Shock-Compressed Materials. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Svendsen, Robert F., Jr.

1987-01-01

Recent observations of shock-induced radiation from oxides, silicates, and metals of geophysical interest constrain the shock-compressed temperature of these materials. The relationships between the temperature inferred from the observed radiation and the temperature of the shock-compressed film or foil and/or window were investigated. Changes of the temperature field in each target component away from that of their respective shock-compressed states occur because of: shock-impedance mismatch between target components; thermal mismatch between target components; surface roughness at target interfaces; and conduction within and between target components. In particular, conduction may affect the temperature of the film/foil window interface on the time scale of the experiments, and so control the intensity and history of the dominant thermal radiation sources in the target. This type of model was used to interpret the radiation emitted by a variety of shock-compressed materials and interfaces.

Hugoniot and refractive indices of bromoform under shock compression

NASA Astrophysics Data System (ADS)

Liu, Q. C.; Zeng, X. L.; Zhou, X. M.; Luo, S. N.

2018-01-01

We investigate physical properties of bromoform (liquid CHBr3) including compressibility and refractive index under dynamic extreme conditions of shock compression. Planar shock experiments are conducted along with high-speed laser interferometry. Our experiments and previous results establish a linear shock velocity-particle velocity relation for particle velocities below 1.77 km/s, as well as the Hugoniot and isentropic compression curves up to ˜21 GPa. Shock-state refractive indices of CHBr3 up to 2.3 GPa or ˜26% compression, as a function of density, can be described with a linear relation and follows the Gladstone-Dale relation. The velocity corrections for laser interferometry measurements at 1550 nm are also obtained.

Shock temperature measurement of transparent materials under shock compression

NASA Astrophysics Data System (ADS)

Hu, Jinbiao

1999-06-01

Under shock compression, some materials have very small absorptance. So it's emissivity is very small too. For this kinds of materials, although they stand in high temperature state under shock compression, the temperature can not be detected easily by using optical radiation technique because of the low emissivity. In this paper, an optical radiation temperature measurement technique of measuring temperature of very low emissive material under shock compression was proposed. For making sure this technique, temperature of crystal NaCl at shock pressure 41 GPa was measured. The result agrees with the results of Kormer et al and Ahrens et al very well. This shows that this technique is reliable and can be used to measuring low emissive shock temperature.

Modeling of a Two-Phase Jet Pump with Phase Change, Shocks and Temperature-Dependent Properties

NASA Technical Reports Server (NTRS)

Sherif, S. A.

1998-01-01

One of the primary motivations behind this work is the attempt to understand the physics of a two-phase jet pump which constitutes part of a flow boiling test facility at NASA-Marshall. The flow boiling apparatus is intended to provide data necessary to design highly efficient two-phase thermal control systems for aerospace applications. The facility will also be capable of testing alternative refrigerants and evaluate their performance using various heat exchangers with enhanced surfaces. The test facility is also intended for use in evaluating single-phase performance of systems currently using CFC refrigerants. Literature dealing with jet pumps is abundant and covers a very wide array of application areas. Example application areas include vacuum pumps which are used in the food industry, power station work, and the chemical industry; ejector systems which have applications in the aircraft industry as cabin ventilators and for purposes of jet thrust augmentation; jet pumps which are used in the oil industry for oil well pumping; and steam-jet ejector refrigeration, to just name a few. Examples of work relevant to this investigation includes those of Fairuzov and Bredikhin (1995). While past researchers have been able to model the two-phase flow jet pump using the one-dimensional assumption with no shock waves and no phase change, there is no research known to the author apart from that of Anand (1992) who was able to account for condensation shocks. Thus, one of the objectives of this work is to model the dynamics of fluid interaction between a two-phase primary fluid and a subcooled liquid secondary fluid which is being injected employing atomizing spray injectors. The model developed accounts for phase transformations due to expansion, compression, and mixing. It also accounts for shock waves developing in the different parts of the jet pump as well as temperature and pressure dependencies of the fluid properties for both the primary two-phase mixture and the secondary subcooled liquid. The research effort on which this document partly reports described a relatively simple model capable of describing the performance of a two-phase flow jet pump. The model is based on the isentropic homogeneous expansion/compression hypothesis and is capable of fully incorporating the effects of shocks in both the mixing chamber and the throat/diffuser parts of the pump. The physical system chosen is identical to that experimentally tested by Fairuzov and Bredikhin (1995) and should therefore be relatively easy to validate.

Causal implications of viscous damping in compressible fluid flows

PubMed

Jordan; Meyer; Puri

2000-12-01

Classically, a compressible, isothermal, viscous fluid is regarded as a mathematical continuum and its motion is governed by the linearized continuity, Navier-Stokes, and state equations. Unfortunately, solutions of this system are of a diffusive nature and hence do not satisfy causality. However, in the case of a half-space of fluid set to motion by a harmonically vibrating plate the classical equation of motion can, under suitable conditions, be approximated by the damped wave equation. Since this equation is hyperbolic, the resulting solutions satisfy causal requirements. In this work the Laplace transform and other analytical and numerical tools are used to investigate this apparent contradiction. To this end the exact solutions, as well as their special and limiting cases, are found and compared for the two models. The effects of the physical parameters on the solutions and associated quantities are also studied. It is shown that propagating wave fronts are only possible under the hyperbolic model and that the concept of phase speed has different meanings in the two formulations. In addition, discontinuities and shock waves are noted and a physical system is modeled under both formulations. Overall, it is shown that the hyperbolic form gives a more realistic description of the physical problem than does the classical theory. Lastly, a simple mechanical analog is given and connections to viscoelastic fluids are noted. In particular, the research presented here supports the notion that linear compressible, isothermal, viscous fluids can, at least in terms of causality, be better characterized as a type of viscoelastic fluid.

Lethal mechanisms in gastric volvulus.

PubMed

Omond, Kimberley J; Byard, Roger W

2017-01-01

A 55-year-old wheelchair-bound woman with severe cerebral palsy was found at autopsy to have marked distention of the stomach due to a volvulus. The stomach was viable, and filled with air and fluid and had pushed the left dome of the diaphragm upwards causing marked compression of the left lung with a mediastinal shift to the right (including the heart). There was no evidence of gastric perforation, ischaemic necrosis or peritonitis. Removal of the organ block revealed marked kyphoscoliosis. Histology confirmed the viability of the stomach and biochemistry showed no dehydration. Death in cases of acute gastric volvulus usually occurs because of compromise of the gastric blood supply resulting in ischaemic necrosis with distention from swallowed air and fluid resulting in perforation with lethal peritonitis. Hypovolaemic shock may also occur. However, the current case demonstrates an alternative lethal mechanism, that of respiratory compromise due to marked thoracic organ compression.

Minimizing pre- and post-defibrillation pauses increases the likelihood of return of spontaneous circulation (ROSC).

PubMed

Sell, Rebecca E; Sarno, Renee; Lawrence, Brenna; Castillo, Edward M; Fisher, Roger; Brainard, Criss; Dunford, James V; Davis, Daniel P

2010-07-01

The three-phase model of ventricular fibrillation (VF) arrest suggests a period of compressions to "prime" the heart prior to defibrillation attempts. In addition, post-shock compressions may increase the likelihood of return of spontaneous circulation (ROSC). The optimal intervals for shock delivery following cessation of compressions (pre-shock interval) and resumption of compressions following a shock (post-shock interval) remain unclear. To define optimal pre- and post-defibrillation compression pauses for out-of-hospital cardiac arrest (OOHCA). All patients suffering OOHCA from VF were identified over a 1-month period. Defibrillator data were abstracted and analyzed using the combination of ECG, impedance, and audio recording. Receiver-operator curve (ROC) analysis was used to define the optimal pre- and post-shock compression intervals. Multiple logistic regression analysis was used to quantify the relationship between these intervals and ROSC. Covariates included cumulative number of defibrillation attempts, intubation status, and administration of epinephrine in the immediate pre-shock compression cycle. Cluster adjustment was performed due to the possibility of multiple defibrillation attempts for each patient. A total of 36 patients with 96 defibrillation attempts were included. The ROC analysis identified an optimal pre-shock interval of <3s and an optimal post-shock interval of <6s. Increased likelihood of ROSC was observed with a pre-shock interval <3s (adjusted OR 6.7, 95% CI 2.0-22.3, p=0.002) and a post-shock interval of <6s (adjusted OR 10.7, 95% CI 2.8-41.4, p=0.001). Likelihood of ROSC was substantially increased with the optimization of both pre- and post-shock intervals (adjusted OR 13.1, 95% CI 3.4-49.9, p<0.001). Decreasing pre- and post-shock compression intervals increases the likelihood of ROSC in OOHCA from VF.

Theoretical fluid dynamics

NASA Astrophysics Data System (ADS)

Shivamoggi, B. K.

This book is concerned with a discussion of the dynamical behavior of a fluid, and is addressed primarily to graduate students and researchers in theoretical physics and applied mathematics. A review of basic concepts and equations of fluid dynamics is presented, taking into account a fluid model of systems, the objective of fluid dynamics, the fluid state, description of the flow field, volume forces and surface forces, relative motion near a point, stress-strain relation, equations of fluid flows, surface tension, and a program for analysis of the governing equations. The dynamics of incompressible fluid flows is considered along with the dynamics of compressible fluid flows, the dynamics of viscous fluid flows, hydrodynamic stability, and dynamics of turbulence. Attention is given to the complex-variable method, three-dimensional irrotational flows, vortex flows, rotating flows, water waves, applications to aerodynamics, shock waves, potential flows, the hodograph method, flows at low and high Reynolds numbers, the Jeffrey-Hamel flow, and the capillary instability of a liquid jet.

CFD Simulations of the IHF Arc-Jet Flow: Compression-Pad Separation Bolt Wedge Tests

NASA Technical Reports Server (NTRS)

Gokcen, Tahir; Skokova, Kristina A.

2017-01-01

This paper reports computational analyses in support of two wedge tests in a high enthalpy arc-jet facility at NASA Ames Research Center. These tests were conducted using two different wedge models, each placed in a free jet downstream of a corresponding different conical nozzle in the Ames 60-MW Interaction Heating Facility. Each panel test article included a metallic separation bolt imbedded in Orion compression-pad and heatshield materials, resulting in a circular protuberance over a flat plate. The protuberances produce complex model flowfields, containing shock-shock and shock-boundary layer interactions, and multiple augmented heating regions on the test plate. As part of the test calibration runs, surface pressure and heat flux measurements on water-cooled calibration plates integrated with the wedge models were also obtained. Surface heating distributions on the test articles as well as arc-jet test environment parameters for each test configuration are obtained through computational fluid dynamics simulations, consistent with the facility and calibration measurements. The present analysis comprises simulations of the non-equilibrium flow field in the facility nozzle, test box, and flow field over test articles, and comparisons with the measured calibration data.

CFD Simulations of the IHF Arc-Jet Flow: Compression-Pad/Separation Bolt Wedge Tests

NASA Technical Reports Server (NTRS)

Goekcen, Tahir; Skokova, Kristina A.

2017-01-01

This paper reports computational analyses in support of two wedge tests in a high enthalpy arc-jet facility at NASA Ames Research Center. These tests were conducted using two different wedge models, each placed in a free jet downstream of a corresponding different conical nozzle in the Ames 60-MW Interaction Heating Facility. Each panel test article included a metallic separation bolt imbedded in Orion compression-pad and heatshield materials, resulting in a circular protuberance over a flat plate. The protuberances produce complex model flowfields, containing shock-shock and shock-boundary layer interactions, and multiple augmented heating regions on the test plate. As part of the test calibration runs, surface pressure and heat flux measurements on water-cooled calibration plates integrated with the wedge models were also obtained. Surface heating distributions on the test articles as well as arc-jet test environment parameters for each test configuration are obtained through computational fluid dynamics simulations, consistent with the facility and calibration measurements. The present analysis comprises simulations of the nonequilibrium flowfield in the facility nozzle, test box, and flowfield over test articles, and comparisons with the measured calibration data.

A Computational Study of a Circular Interface Richtmyer-Meshkov Instability in MHD

NASA Astrophysics Data System (ADS)

Maxon, William; Black, Wolfgang; Denissen, Nicholas; McFarland, Jacob; Los Alamos National Laboratory Collaboration; University of Missouri Shock Tube Laboratory Team

2017-11-01

The Richtmyer-Meshkov instability (RMI) is a hydrodynamic instability that appears in several high energy density applications such as inertial confinement fusion (ICF). In ICF, as the thermonuclear fuel is being compressed it begins to mix due to fluid instabilities including the RMI. This mixing greatly decreases the energy output. The RMI occurs when two fluids of different densities are impulsively accelerated and the pressure and density gradients are misaligned. In magnetohydrodynamics (MHD), the RMI may be suppressed by introducing a magnetic field in an electrically conducting fluid, such as a plasma. This suppression has been studied as a possible mechanism for improving confinement in ICF targets. In this study,ideal MHD simulations are performed with a circular interface impulsively accelerated by a shock wave in the presence of a magnetic field. These simulations are executed with the research code FLAG, a multiphysics, arbitrary Lagrangian/Eulerian, hydrocode developed and utilized at Los Alamos National Laboratory. The simulation results will be assessed both quantitatively and qualitatively to examine the stabilization mechanism. These simulations will guide ongoing MHD experiments at the University of Missouri Shock Tube Facility.

A randomized control hands-on defibrillation study-Barrier use evaluation.

PubMed

Wampler, David; Kharod, Chetan; Bolleter, Scotty; Burkett, Alison; Gabehart, Caitlin; Manifold, Craig

2016-06-01

Chest compressions and defibrillation are the only therapies proven to increase survival in cardiac arrest. Historically, rescuers must remove hands to shock, thereby interrupting chest compressions. This hands-off time results in a zero blood flow state. Pauses have been associated with poorer neurological recovery. This was a blinded randomized control cadaver study evaluating the detection of defibrillation during manual chest compressions. An active defibrillator was connected to the cadaver in the sternum-apex configuration. The sham defibrillator was not connected to the cadaver. Subjects performed chest compressions using 6 barrier types: barehand, single and double layer nitrile gloves, firefighter gloves, neoprene pad, and a manual chest compression/decompression device. Randomized defibrillations (10 per barrier type) were delivered at 30 joules (J) for bare hand and 360J for all other barriers. After each shock, the subject indicated degree of sensation on a VAS scale. Ten subjects participated. All subjects detected 30j shocks during barehand compressions, with only 1 undetected real shock. All barriers combined totaled 500 shocks delivered. Five (1%) active shocks were detected, 1(0.2%) single layer of Nitrile, 3(0.6%) with double layer nitrile, and 1(0.2%) with the neoprene barrier. One sham shock was reported with the single layer nitrile glove. No shocks were detected with fire gloves or compression decompression device. All shocks detected barely perceptible (0.25(±0.05)cm on 10cm VAS scale). Nitrile gloves and neoprene pad prevent (99%) responder's detection of defibrillation of a cadaver. Fire gloves and compression decompression device prevented detection. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

An interface capturing scheme for modeling atomization in compressible flows

NASA Astrophysics Data System (ADS)

Garrick, Daniel P.; Hagen, Wyatt A.; Regele, Jonathan D.

2017-09-01

The study of atomization in supersonic flow is critical to ensuring reliable ignition of scramjet combustors under startup conditions. Numerical methods incorporating surface tension effects have largely focused on the incompressible regime as most atomization applications occur at low Mach numbers. Simulating surface tension effects in compressible flow requires robust numerical methods that can handle discontinuities caused by both shocks and material interfaces with high density ratios. In this work, a shock and interface capturing scheme is developed that uses the Harten-Lax-van Leer-Contact (HLLC) Riemann solver while a Tangent of Hyperbola for INterface Capturing (THINC) interface reconstruction scheme retains the fluid immiscibility condition in the volume fraction and phasic densities in the context of the five equation model. The approach includes the effects of compressibility, surface tension, and molecular viscosity. One and two-dimensional benchmark problems demonstrate the desirable interface sharpening and conservation properties of the approach. Simulations of secondary atomization of a cylindrical water column after its interaction with a shockwave show good qualitative agreement with experimentally observed behavior. Three-dimensional examples of primary atomization of a liquid jet in a Mach 2 crossflow demonstrate the robustness of the method.

Equation of State Measurements of Deuterium up to 2 Mbar

NASA Astrophysics Data System (ADS)

Collins, G. W.

1997-04-01

While the hydrogen Equation of State at high density and temperature is integral to many astrophysical and planetary models, few experimental techniques can access the strongly-coupled region where molecular dissociation or electronic excitation occur. High power lasers can access much of this unexplored phase space. We(This work was done in collaboration with L. B. Da Silva, P. Celliers, K. S. Budil, R. Cauble, N. C. Holmes, T. W. Barbee Jr, B. A. Hammel, J. D. Kilkenny, R. J. Wallace, M. Ross, A. Ng and G. Chiu.) present the pressure (from 0.25 to 2.1 Mbar) and density on the first Hugoniot, derived from shock speed, particle speed, and compression measurements of liquid deuterium. Shock waves were produced with the Nova laser. The data show a significant increase in compressibility near 1 Mbar compared to existing widely-used equation of state models. The data are consistent with a thermal molecular dissociation of the diatomic fluid into a monatomic phase.

Simulating compressible-incompressible two-phase flows

NASA Astrophysics Data System (ADS)

Denner, Fabian; van Wachem, Berend

2017-11-01

Simulating compressible gas-liquid flows, e.g. air-water flows, presents considerable numerical issues and requires substantial computational resources, particularly because of the stiff equation of state for the liquid and the different Mach number regimes. Treating the liquid phase (low Mach number) as incompressible, yet concurrently considering the gas phase (high Mach number) as compressible, can improve the computational performance of such simulations significantly without sacrificing important physical mechanisms. A pressure-based algorithm for the simulation of two-phase flows is presented, in which a compressible and an incompressible fluid are separated by a sharp interface. The algorithm is based on a coupled finite-volume framework, discretised in conservative form, with a compressive VOF method to represent the interface. The bulk phases are coupled via a novel acoustically-conservative interface discretisation method that retains the acoustic properties of the compressible phase and does not require a Riemann solver. Representative test cases are presented to scrutinize the proposed algorithm, including the reflection of acoustic waves at the compressible-incompressible interface, shock-drop interaction and gas-liquid flows with surface tension. Financial support from the EPSRC (Grant EP/M021556/1) is gratefully acknowledged.

On the finite length-scale of compressible shock-waves formed in free-surface flows of dry granular materials down a slope

NASA Astrophysics Data System (ADS)

Faug, Thierry

2017-04-01

The Rankine-Hugoniot jump conditions traditionally describe the theoretical relationship between the equilibrium state on both sides of a shock-wave. They are based on the crucial assumption that the length-scale needed to adjust the equilibrium state upstream of the shock to downstream of it is too small to be of significance to the problem. They are often used with success to describe the shock-waves in a number of applications found in both fluid and solid mechanics. However, the relations based on jump conditions at singular surfaces may fail to capture some features of the shock-waves formed in complex materials, such as granular matter. This study addresses the particular problem of compressible shock-waves formed in flows of dry granular materials down a slope. This problem is for instance relevant to full-scale geophysical granular flows in interaction with natural obstacles or man-made structures, such as topographical obstacles or mitigation dams respectively. Steady-state jumps formed in granular flows and travelling shock-waves produced at the impact of a granular avalanche-flow with a rigid wall are considered. For both situations, new analytical relations which do not consider that the granular shock-wave shrinks into a singular surface are derived, by using balance equations in their depth-averaged forms for mass and momentum. However, these relations need additional inputs that are closure relations for the size and the shape of the shock-wave, and a relevant constitutive friction law. Small-scale laboratory tests and numerical simulations based on the discrete element method are shortly presented and used to infer crucial information needed for the closure relations. This allows testing some predictive aspects of the simple analytical approach proposed for both steady-state and travelling shock-waves formed in free-surface flows of dry granular materials down a slope.

Shock-wave studies of anomalous compressibility of glassy carbon

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

Molodets, A. M., E-mail: molodets@icp.ac.ru; Golyshev, A. A.; Savinykh, A. S.

2016-02-15

The physico-mechanical properties of amorphous glassy carbon are investigated under shock compression up to 10 GPa. Experiments are carried out on the continuous recording of the mass velocity of compression pulses propagating in glassy carbon samples with initial densities of 1.502(5) g/cm{sup 3} and 1.55(2) g/cm{sup 3}. It is shown that, in both cases, a compression wave in glassy carbon contains a leading precursor with amplitude of 0.135(5) GPa. It is established that, in the range of pressures up to 2 GPa, a shock discontinuity in glassy carbon is transformed into a broadened compression wave, and shock waves are formedmore » in the release wave, which generally means the anomalous compressibility of the material in both the compression and release waves. It is shown that, at pressure higher than 3 GPa, anomalous behavior turns into normal behavior, accompanied by the formation of a shock compression wave. In the investigated area of pressure, possible structural changes in glassy carbon under shock compression have a reversible character. A physico-mechanical model of glassy carbon is proposed that involves the equation of state and a constitutive relation for Poisson’s ratio and allows the numerical simulation of physico-mechanical and thermophysical properties of glassy carbon of different densities in the region of its anomalous compressibility.« less

The Link Between Shocks, Turbulence, and Magnetic Reconnection in Collisionless Plasmas

NASA Technical Reports Server (NTRS)

Karimabadi, H.; Roytershteyn, V.; Vu, H. X.; Omelchenko, Y. A.; Scudder, J.; Daughton, W.; Dimmock, A.; Nykyri, K.; Wan, M.; Sibeck, D.;

Anomalous elastic response of silicon to uniaxial shock compression on nanosecond time scales.

PubMed

Loveridge-Smith, A; Allen, A; Belak, J; Boehly, T; Hauer, A; Holian, B; Kalantar, D; Kyrala, G; Lee, R W; Lomdahl, P; Meyers, M A; Paisley, D; Pollaine, S; Remington, B; Swift, D C; Weber, S; Wark, J S

2001-03-12

We have used x-ray diffraction with subnanosecond temporal resolution to measure the lattice parameters of orthogonal planes in shock compressed single crystals of silicon (Si) and copper (Cu). Despite uniaxial compression along the (400) direction of Si reducing the lattice spacing by nearly 11%, no observable changes occur in planes with normals orthogonal to the shock propagation direction. In contrast, shocked Cu shows prompt hydrostaticlike compression. These results are consistent with simple estimates of plastic strain rates based on dislocation velocity data.

Transparency of the strong shock-compressed diamond for 532 nm laser light

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

Zhang, Zhiyu; Department of Engineering Physics, Tsinghua University, Beijing 100084; Zhao, Yang

2016-04-15

An optical reflectivity and transmissivity model for the shock-compressed diamond is established and used to calculate the optical reflectivity and transmissivity of the diamond under different shock compressions. The simulated results indicate that the reflection occurs at the shock front and does not depend on the thickness of the compressed diamond, but the transmissivity decreases with the thickness. The simulated reflectivity is consistent with the experimental results in the literature, which validates the model. It is shown that the diamond keeps transparent when the shock pressure is lower than 2.00 Mbar, and becomes opaque but does not reflect the probemore » laser as the shock pressure increases from 2.00 Mbar to 4.60 Mbar and reflects the probe laser markedly when the shock pressure is higher than 4.60 Mbar.« less

Methodology for the Design of Streamline-Traced External-Compression Supersonic Inlets

NASA Technical Reports Server (NTRS)

Slater, John W.

2014-01-01

A design methodology based on streamline-tracing is discussed for the design of external-compression, supersonic inlets for flight below Mach 2.0. The methodology establishes a supersonic compression surface and capture cross-section by tracing streamlines through an axisymmetric Busemann flowfield. The compression system of shock and Mach waves is altered through modifications to the leading edge and shoulder of the compression surface. An external terminal shock is established to create subsonic flow which is diffused in the subsonic diffuser. The design methodology was implemented into the SUPIN inlet design tool. SUPIN uses specified design factors to design the inlets and computes the inlet performance, which includes the flow rates, total pressure recovery, and wave drag. A design study was conducted using SUPIN and the Wind-US computational fluid dynamics code to design and analyze the properties of two streamline-traced, external-compression (STEX) supersonic inlets for Mach 1.6 freestream conditions. The STEX inlets were compared to axisymmetric pitot, two-dimensional, and axisymmetric spike inlets. The STEX inlets had slightly lower total pressure recovery and higher levels of total pressure distortion than the axisymmetric spike inlet. The cowl wave drag coefficients of the STEX inlets were 20% of those for the axisymmetric spike inlet. The STEX inlets had external sound pressures that were 37% of those of the axisymmetric spike inlet, which may result in lower adverse sonic boom characteristics. The flexibility of the shape of the capture cross-section may result in benefits for the integration of STEX inlets with aircraft.

Advanced computational techniques for incompressible/compressible fluid-structure interactions

NASA Astrophysics Data System (ADS)

Kumar, Vinod

2005-07-01

Fluid-Structure Interaction (FSI) problems are of great importance to many fields of engineering and pose tremendous challenges to numerical analyst. This thesis addresses some of the hurdles faced for both 2D and 3D real life time-dependent FSI problems with particular emphasis on parachute systems. The techniques developed here would help improve the design of parachutes and are of direct relevance to several other FSI problems. The fluid system is solved using the Deforming-Spatial-Domain/Stabilized Space-Time (DSD/SST) finite element formulation for the Navier-Stokes equations of incompressible and compressible flows. The structural dynamics solver is based on a total Lagrangian finite element formulation. Newton-Raphson method is employed to linearize the otherwise nonlinear system resulting from the fluid and structure formulations. The fluid and structural systems are solved in decoupled fashion at each nonlinear iteration. While rigorous coupling methods are desirable for FSI simulations, the decoupled solution techniques provide sufficient convergence in the time-dependent problems considered here. In this thesis, common problems in the FSI simulations of parachutes are discussed and possible remedies for a few of them are presented. Further, the effects of the porosity model on the aerodynamic forces of round parachutes are analyzed. Techniques for solving compressible FSI problems are also discussed. Subsequently, a better stabilization technique is proposed to efficiently capture and accurately predict the shocks in supersonic flows. The numerical examples simulated here require high performance computing. Therefore, numerical tools using distributed memory supercomputers with message passing interface (MPI) libraries were developed.

Thermophysical properties of multi-shock compressed dense argon.

PubMed

Chen, Q F; Zheng, J; Gu, Y J; Chen, Y L; Cai, L C; Shen, Z J

2014-02-21

In contrast to the single shock compression state that can be obtained directly via experimental measurements, the multi-shock compression states, however, have to be calculated with the aid of theoretical models. In order to determine experimentally the multiple shock states, a diagnostic approach with the Doppler pins system (DPS) and the pyrometer was used to probe multiple shocks in dense argon plasmas. Plasma was generated by a shock reverberation technique. The shock was produced using the flyer plate impact accelerated up to ∼6.1 km/s by a two-stage light gas gun and introduced into the plenum argon gas sample, which was pre-compressed from the environmental pressure to about 20 MPa. The time-resolved optical radiation histories were determined using a multi-wavelength channel optical transience radiance pyrometer. Simultaneously, the particle velocity profiles of the LiF window was measured with multi-DPS. The states of multi-shock compression argon plasma were determined from the measured shock velocities combining the particle velocity profiles. We performed the experiments on dense argon plasmas to determine the principal Hugonoit up to 21 GPa, the re-shock pressure up to 73 GPa, and the maximum measure pressure of the fourth shock up to 158 GPa. The results are used to validate the existing self-consistent variational theory model in the partial ionization region and create new theoretical models.

Thermophysical properties of multi-shock compressed dense argon

NASA Astrophysics Data System (ADS)

Chen, Q. F.; Zheng, J.; Gu, Y. J.; Chen, Y. L.; Cai, L. C.; Shen, Z. J.

2014-02-01

In contrast to the single shock compression state that can be obtained directly via experimental measurements, the multi-shock compression states, however, have to be calculated with the aid of theoretical models. In order to determine experimentally the multiple shock states, a diagnostic approach with the Doppler pins system (DPS) and the pyrometer was used to probe multiple shocks in dense argon plasmas. Plasma was generated by a shock reverberation technique. The shock was produced using the flyer plate impact accelerated up to ˜6.1 km/s by a two-stage light gas gun and introduced into the plenum argon gas sample, which was pre-compressed from the environmental pressure to about 20 MPa. The time-resolved optical radiation histories were determined using a multi-wavelength channel optical transience radiance pyrometer. Simultaneously, the particle velocity profiles of the LiF window was measured with multi-DPS. The states of multi-shock compression argon plasma were determined from the measured shock velocities combining the particle velocity profiles. We performed the experiments on dense argon plasmas to determine the principal Hugonoit up to 21 GPa, the re-shock pressure up to 73 GPa, and the maximum measure pressure of the fourth shock up to 158 GPa. The results are used to validate the existing self-consistent variational theory model in the partial ionization region and create new theoretical models.

Shock-induced perturbation evolution in planar laser targets

NASA Astrophysics Data System (ADS)

Aglitskiy, Y.; Karasik, M.; Velikovich, A. L.; Serlin, V.; Weaver, J. L.; Kessler, T. J.; Schmitt, A. J.; Obenschain, S. P.; Metzler, N.; Oh, J.

2013-10-01

Experimental studies of hydrodynamic perturbation evolution triggered by a laser-driven shock wave in a planar target done on the KrF Nike laser facility are reported. The targets were made of solid plastic and/or plastic foam with single mode sinusoidal perturbation on the front or back surface or plastic/foam interface. Two specific cases are discussed. When a planar solid plastic target rippled at the front side is irradiated with a 350 ps long laser pulse, ablative Richtmyer-Meshkov (RM) oscillation of its areal mass modulation amplitude is detected while the laser is on, followed by observed strong oscillations of the areal mass in the unsupported shock flow after the laser pulse ends. When the target is rippled at the rear side, the nature of the perturbation evolution after the shock breakout is determined by the strength of the laser-driven shock wave. At pressure below 1 Mbar shock interaction with rear-surface ripples produces planar collimated jets manifesting the development of a classical RM instability in a weakly compressible shocked fluid. At shock pressure ~ 8 Mbar sufficient for vaporizing the shocked target material we observed instead the strong areal mass oscillations characteristic of a rippled centered rarefaction wave. Work supported by US DOE, Defense Programs.

A model and numerical method for compressible flows with capillary effects

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

Schmidmayer, Kevin, E-mail: kevin.schmidmayer@univ-amu.fr; Petitpas, Fabien, E-mail: fabien.petitpas@univ-amu.fr; Daniel, Eric, E-mail: eric.daniel@univ-amu.fr

2017-04-01

A new model for interface problems with capillary effects in compressible fluids is presented together with a specific numerical method to treat capillary flows and pressure waves propagation. This new multiphase model is in agreement with physical principles of conservation and respects the second law of thermodynamics. A new numerical method is also proposed where the global system of equations is split into several submodels. Each submodel is hyperbolic or weakly hyperbolic and can be solved with an adequate numerical method. This method is tested and validated thanks to comparisons with analytical solutions (Laplace law) and with experimental results onmore » droplet breakup induced by a shock wave.« less

Deceleration of a supersonic flow behind a curved shock wave with isentropic precompression

NASA Technical Reports Server (NTRS)

Dulov, V. G.; Shchepanovskiy, V. A.

1985-01-01

Three-dimensional supersonic flows of an ideal fluid in the neighborhood of bodies formed by being cut out along the streamlines of an axisymmetric flow are investigated. The flow consists of a region of isoentropic compression and a region of vortex flow. An exact solution with variable entropy is used to describe the flow in the vortex region. In the continuous flow region an approximate solution is constructed by expanding the solution in a series in a small parameter. The effect of the shape of the excision and the vorticity of the flow on compression of the jet and and the total pressure loss coefficient is studied.

A Level-set based framework for viscous simulation of particle-laden supersonic flows

NASA Astrophysics Data System (ADS)

Das, Pratik; Sen, Oishik; Jacobs, Gustaaf; Udaykumar, H. S.

2017-06-01

Particle-laden supersonic flows are important in natural and industrial processes, such as, volcanic eruptions, explosions, pneumatic conveyance of particle in material processing etc. Numerical study of such high-speed particle laden flows at the mesoscale calls for a numerical framework which allows simulation of supersonic flow around multiple moving solid objects. Only a few efforts have been made toward development of numerical frameworks for viscous simulation of particle-fluid interaction in supersonic flow regime. The current work presents a Cartesian grid based sharp-interface method for viscous simulations of interaction between supersonic flow with moving rigid particles. The no-slip boundary condition is imposed at the solid-fluid interfaces using a modified ghost fluid method (GFM). The current method is validated against the similarity solution of compressible boundary layer over flat-plate and benchmark numerical solution for steady supersonic flow over cylinder. Further validation is carried out against benchmark numerical results for shock induced lift-off of a cylinder in a shock tube. 3D simulation of steady supersonic flow over sphere is performed to compare the numerically obtained drag co-efficient with experimental results. A particle-resolved viscous simulation of shock interaction with a cloud of particles is performed to demonstrate that the current method is suitable for large-scale particle resolved simulations of particle-laden supersonic flows.

Investigations of Compression Shocks and Boundary Layers in Gases Moving at High Speed

NASA Technical Reports Server (NTRS)

Ackeret, J.; Feldmann, F.; Rott, N.

1947-01-01

The mutual influences of compression shocks and friction boundary layers were investigated by means of high speed wind tunnels.Schlieren optics provided a clear picture of the flow phenomena and were used for determining the location of the compression shocks, measurement of shock angles, and also for Mach angles. Pressure measurement and humidity measurements were also taken into consideration.Results along with a mathematical model are described.

Numerical Simulations of High-Speed Chemically Reacting Flow

NASA Technical Reports Server (NTRS)

Ton, V. T.; Karagozian, A. R.; Marble, F. E.; Osher, S. J.; Engquist, B. E.

1994-01-01

The essentially nonoscillatory (ENO) shock-capturing scheme for the solution of hyperbolic equations is extended to solve a system of coupled conservation equations governing two-dimensional, time-dependent, compressible chemically reacting flow with full chemistry. The thermodynamic properties of the mixture are modeled accurately, and stiff kinetic terms are separated from the fluid motion by a fractional step algorithm. The methodology is used to study the concept of shock-induced mixing and combustion, a process by which the interaction of a shock wave with a jet of low-density hydrogen fuel enhances mixing through streamwise vorticity generation. Test cases with and without chemical reaction are explored here. Our results indicate that, in the temperature range examined, vorticity generation as well as the distribution of atomic species do not change significantly with the introduction of a chemical reaction and subsequent heat release. The actual diffusion of hydrogen is also relatively unaffected by the reaction process. This suggests that the fluid mechanics of this problem may be successfully decoupled from the combustion processes, and that computation of the mixing problem (without combustion chemistry) can elucidate much of the important physical features of the flow.

Numerical Simulations of High-Speed Chemically Reacting Flow

NASA Technical Reports Server (NTRS)

Ton, V. T.; Karagozin, A. R.; Marble, F. E.; Osher, S. J.; Engquist, B. E.

1994-01-01

The Essentially NonOscillatory (ENO) shock-capturing scheme for the solution of hyperbolic equations is extended to solve a system of coupled conservation equations governing two-dimensional, time-dependent, compressible chemically reacting flow with full chemistry. The thermodynamic properties of the mixture are modeled accurately, and stiff kinetic terms are separated from the fluid motion by a fractional step algorithm. The methodology is used to study the concept of shock-induced mixing and combustion, a process by which the interaction of a shock wave with a jet of low-density hydrogen fuel enhances mixing through streamwise vorticity generation. Test cases with and without chemical reaction are explored here. Our results indicate that, in the temperature range examined, vorticity generation as well as the distribution of atomic species do not change significantly with the introduction of a chemical reaction and subsequent heat release. The actual diffusion of hydrogen is also relatively unaffected by the reaction process. This suggests that the fluid mechanics of this problem may be successfully decoupled from the combustion processes, and that computation of the mixing problem (without combustion chemistry) can elucidate much of the important physical features of the flow.

A hybrid numerical fluid dynamics code for resistive magnetohydrodynamics

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

Johnson, Jeffrey

2006-04-01

Spasmos is a computational fluid dynamics code that uses two numerical methods to solve the equations of resistive magnetohydrodynamic (MHD) flows in compressible, inviscid, conducting media[1]. The code is implemented as a set of libraries for the Python programming language[2]. It represents conducting and non-conducting gases and materials with uncomplicated (analytic) equations of state. It supports calculations in 1D, 2D, and 3D geometry, though only the 1D configuation has received significant testing to date. Because it uses the Python interpreter as a front end, users can easily write test programs to model systems with a variety of different numerical andmore » physical parameters. Currently, the code includes 1D test programs for hydrodynamics (linear acoustic waves, the Sod weak shock[3], the Noh strong shock[4], the Sedov explosion[5], magnetic diffusion (decay of a magnetic pulse[6], a driven oscillatory "wine-cellar" problem[7], magnetic equilibrium), and magnetohydrodynamics (an advected magnetic pulse[8], linear MHD waves, a magnetized shock tube[9]). Spasmos current runs only in a serial configuration. In the future, it will use MPI for parallel computation.« less

Dissipative processes under the shock compression of glass

NASA Astrophysics Data System (ADS)

Savinykh, A. S.; Kanel, G. I.; Cherepanov, I. A.; Razorenov, S. V.

2016-03-01

New experimental data on the behavior of the K8 and TF1 glasses under shock-wave loading conditions are obtained. It is found that the propagation of shock waves is close to the self-similar one in the maximum compression stress range 4-12 GPa. Deviations from a general deformation diagram, which are related to viscous dissipation, take place when the final state of compression is approached. The parameter region in which failure waves form in glass is found not to be limited to the elastic compression stress range, as was thought earlier. The failure front velocity increases with the shock compression stress. Outside the region covered by a failure wave, the glasses demonstrate a high tensile dynamic strength (6-7 GPa) in the case of elastic compression, and this strength is still very high after transition through the elastic limit in a compression wave.

Ultra high-speed x-ray imaging of laser-driven shock compression using synchrotron light

NASA Astrophysics Data System (ADS)

Olbinado, Margie P.; Cantelli, Valentina; Mathon, Olivier; Pascarelli, Sakura; Grenzer, Joerg; Pelka, Alexander; Roedel, Melanie; Prencipe, Irene; Laso Garcia, Alejandro; Helbig, Uwe; Kraus, Dominik; Schramm, Ulrich; Cowan, Tom; Scheel, Mario; Pradel, Pierre; De Resseguier, Thibaut; Rack, Alexander

2018-02-01

A high-power, nanosecond pulsed laser impacting the surface of a material can generate an ablation plasma that drives a shock wave into it; while in situ x-ray imaging can provide a time-resolved probe of the shock-induced material behaviour on macroscopic length scales. Here, we report on an investigation into laser-driven shock compression of a polyurethane foam and a graphite rod by means of single-pulse synchrotron x-ray phase-contrast imaging with MHz frame rate. A 6 J, 10 ns pulsed laser was used to generate shock compression. Physical processes governing the laser-induced dynamic response such as elastic compression, compaction, pore collapse, fracture, and fragmentation have been imaged; and the advantage of exploiting the partial spatial coherence of a synchrotron source for studying low-density, carbon-based materials is emphasized. The successful combination of a high-energy laser and ultra high-speed x-ray imaging using synchrotron light demonstrates the potentiality of accessing complementary information from scientific studies of laser-driven shock compression.

The effect of artificial bulk viscosity in simulations of forced compressible turbulence

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

Campos, A.; Morgan, B.

The use of an artificial bulk viscosity for shock stabilization is a common approach employed in turbulence simulations with high-order numerics. The effect of the artificial bulk viscosity is analyzed in the context of large eddy simulations by using as a test case simulations of linearly-forced compressible homogeneous turbulence (Petersen and Livescu, 2010 [12]). This case is unique in that it allows for the specification of a priori target values for total dissipation and ratio of solenoidal to dilatational dissipation. A comparison between these target values and the true predicted levels of dissipation is thus used to investigate the performancemore » of the artificial bulk viscosity. Results show that the artificial bulk viscosity is effective at achieving stable solutions, but also leads to large values of artificial dissipation that outweigh the physical dissipation caused by fluid viscosity. An alternate approach, which employs the artificial thermal conductivity only, shows that the dissipation of dilatational modes is entirely due to the fluid viscosity. However, this method leads to unwanted Gibbs oscillations around the shocklets. The use of shock sensors that further localize the artificial bulk viscosity did not reduce the amount of artificial dissipation introduced by the artificial bulk viscosity. Finally, an improved forcing function that explicitly accounts for the role of the artificial bulk viscosity in the budget of turbulent kinetic energy was explored.« less

The effect of artificial bulk viscosity in simulations of forced compressible turbulence

DOE PAGES

Campos, A.; Morgan, B.

2018-05-17

The use of an artificial bulk viscosity for shock stabilization is a common approach employed in turbulence simulations with high-order numerics. The effect of the artificial bulk viscosity is analyzed in the context of large eddy simulations by using as a test case simulations of linearly-forced compressible homogeneous turbulence (Petersen and Livescu, 2010 [12]). This case is unique in that it allows for the specification of a priori target values for total dissipation and ratio of solenoidal to dilatational dissipation. A comparison between these target values and the true predicted levels of dissipation is thus used to investigate the performancemore » of the artificial bulk viscosity. Results show that the artificial bulk viscosity is effective at achieving stable solutions, but also leads to large values of artificial dissipation that outweigh the physical dissipation caused by fluid viscosity. An alternate approach, which employs the artificial thermal conductivity only, shows that the dissipation of dilatational modes is entirely due to the fluid viscosity. However, this method leads to unwanted Gibbs oscillations around the shocklets. The use of shock sensors that further localize the artificial bulk viscosity did not reduce the amount of artificial dissipation introduced by the artificial bulk viscosity. Finally, an improved forcing function that explicitly accounts for the role of the artificial bulk viscosity in the budget of turbulent kinetic energy was explored.« less

In situ X-Ray Diffraction of Shock-Compressed Fused Silica

NASA Astrophysics Data System (ADS)

Tracy, Sally June; Turneaure, Stefan J.; Duffy, Thomas S.

2018-03-01

Because of its widespread applications in materials science and geophysics, SiO2 has been extensively examined under shock compression. Both quartz and fused silica transform through a so-called "mixed-phase region" to a dense, low compressibility high-pressure phase. For decades, the nature of this phase has been a subject of debate. Proposed structures include crystalline stishovite, another high-pressure crystalline phase, or a dense amorphous phase. Here we use plate-impact experiments and pulsed synchrotron x-ray diffraction to examine the structure of fused silica shock compressed to 63 GPa. In contrast to recent laser-driven compression experiments, we find that fused silica adopts a dense amorphous structure at 34 GPa and below. When compressed above 34 GPa, fused silica transforms to untextured polycrystalline stishovite. Our results can explain previously ambiguous features of the shock-compression behavior of fused silica and are consistent with recent molecular dynamics simulations. Stishovite grain sizes are estimated to be ˜5 - 30 nm for compression over a few hundred nanosecond time scale.

The impact of manual defibrillation technique on no-flow time during simulated cardiopulmonary resuscitation.

PubMed

Perkins, Gavin D; Davies, Robin P; Soar, Jasmeet; Thickett, David R

2007-04-01

Rapid defibrillation is the most effective strategy for establishing return of spontaneous circulation following cardiac arrest due to ventricular fibrillation. The aim of this study is to measure the delay due to of charging the defibrillator during chest compression in an attempt to reduce the duration of the pre-shock pause in between cessation of chest compressions and shock delivery as advocated by the American Heart Association (AHA) guidelines compared to charging the defibrillator immediately following rhythm analysis without resuming chest compressions as recommended by the European Resuscitation Council (ERC). This was a randomised controlled cross over trial comparing pre-shock pause times when defibrillation was performed on a manikin according to the AHA and ERC guidelines using paddles and hands free defibrillation systems. The pre-shock pause between cessation of chest compression and shock delivery was significantly different between techniques (Friedman test, P<0.0001). ERC paddles technique had the greatest pre-shock pause (7.4 s [6.7-11.2]) followed by ERC hands free (7.0 s [6.5-8.5]) and AHA paddles (1.6 s [1.1-2.3]). AHA hands free took the least amount of time (1.5 s [0.8-1.5]). Extrapolating these data to older defibrillators with longer charge times saw pre-shock pause intervals of 9 s (Codemaster XL) and 12 s (Lifepak 20) with the ERC approach. This study demonstrated clinically significant delays to defibrillation by analysing and charging the defibrillator without performing concurrent chest compressions. In a simulated scenario, charging the defibrillator whilst performing chest compressions was perceived as safe and significantly reduced the pre-shock pause between cessation of chest compression and shock delivery.

Structure of relativistic shocks in pulsar winds: A model of the wisps in the Crab Nebula

NASA Technical Reports Server (NTRS)

Gallant, Yves A.; Arons, Jonathan

1994-01-01

We propose a model of a optical 'wisps' of the Crab Nebula, features observed in the nebular synchrotron surface brightness near the central pulsar, as manifestations of the internal structure of the shock terminating the pulsar wind. We assume that this wind is composed of ions and a much denser plasma of electrons and positrons, frozen together to a toroidal magnetic field and flowing relativistically. We construct a form of solitary wave model of the shock structure in which we self-consistently solve for the ion orbits and the dynamics of the relativistically hot, magnetized e(+/-) background flow. We ignore dispersion in the ion energies, and we treat the pairs as an adiabatic fluid. The synchrotron emission enhancements, observed as the wisps, are then explained as the regions where reflection of the ions in the self-consistent magnetic field causes compressions of the e(+/-).

Preliminary Numerical Simulations of Nozzle Formation in the Host Rock of Supersonic Volcanic Jets

NASA Astrophysics Data System (ADS)

Wohletz, K. H.; Ogden, D. E.; Glatzmaier, G. A.

2006-12-01

Recognizing the difficulty in quantitatively predicting how a vent changes during an explosive eruption, Kieffer (Kieffer, S.W., Rev. Geophys. 27, 1989) developed the theory of fluid dynamic nozzles for volcanism, utilizing a highly developed predictive scheme used extensively in aerodynamics for design of jet and rocket nozzles. Kieffer's work shows that explosive eruptions involve flow from sub to supersonic conditions through the vent and that these conditions control the erosion of the vent to nozzle shapes and sizes that maximize mass flux. The question remains how to predict the failure and erosion of vent host rocks by a high-speed, multiphase, compressible fluid that represents an eruption column. Clearly, in order to have a quantitative model of vent dynamics one needs a robust computational method for a turbulent, compressible, multiphase fluid. Here we present preliminary simulations of fluid flowing from a high-pressure reservoir through an eroding conduit and into the atmosphere. The eruptive fluid is modeled as an ideal gas, the host rock as a simple incompressible fluid with sandstone properties. Although these simulations do not yet include the multiphase dynamics of the eruptive fluid or the solid mechanics of the host rock, the evolution of the host rock into a supersonic nozzle is clearly seen. Our simulations show shock fronts both above the conduit, where the gas has expanded into the atmosphere, and within the conduit itself, thereby influencing the dynamics of the jet decompression.

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

Use of a wave reverberation technique to infer the density compression of shocked liquid deuterium to 75 GPa.

PubMed

Knudson, M D; Hanson, D L; Bailey, J E; Hall, C A; Asay, J R

2003-01-24

A novel approach was developed to probe density compression of liquid deuterium (L-D2) along the principal Hugoniot. Relative transit times of shock waves reverberating within the sample are shown to be sensitive to the compression due to the first shock. This technique has proven to be more sensitive than the conventional method of inferring density from the shock and mass velocity, at least in this high-pressure regime. Results in the range of 22-75 GPa indicate an approximately fourfold density compression, and provide data to differentiate between proposed theories for hydrogen and its isotopes.

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

Ozaki, N.; Nellis, W. J.; Mashimo, T.

Materials at high pressures and temperatures are of great current interest for warm dense matter physics, planetary sciences, and inertial fusion energy research. Shock-compression equation-of-state data and optical reflectivities of the fluid dense oxide, Gd 3Ga 5O 12 (GGG), were measured at extremely high pressures up to 2.6 TPa (26 Mbar) generated by high-power laser irradiation and magnetically-driven hypervelocity impacts. Above 0.75 TPa, the GGG Hugoniot data approach/reach a universal linear line of fluid metals, and the optical reflectivity most likely reaches a constant value indicating that GGG undergoes a crossover from fluid semiconductor to poor metal with minimum metallicmore » conductivity (MMC). These results suggest that most fluid compounds, e.g., strong planetary oxides, reach a common state on the universal Hugoniot of fluid metals (UHFM) with MMC at sufficiently extreme pressures and temperatures. Lastly, the systematic behaviors of warm dense fluid would be useful benchmarks for developing theoretical equation-of-state and transport models in the warm dense matter regime in determining computational predictions.« less

A Multiscale Approach to Blast Neurotrauma Modeling: Part I – Development of Novel Test Devices for in vivo and in vitro Blast Injury Models

PubMed Central

Panzer, Matthew B.; Matthews, Kyle A.; Yu, Allen W.; Morrison, Barclay; Meaney, David F.; Bass, Cameron R.

2012-01-01

The loading conditions used in some current in vivo and in vitro blast-induced neurotrauma models may not be representative of real-world blast conditions. To address these limitations, we developed a compressed-gas driven shock tube with different driven lengths that can generate Friedlander-type blasts. The shock tube can generate overpressures up to 650 kPa with durations between 0.3 and 1.1 ms using compressed helium driver gas, and peak overpressures up to 450 kPa with durations between 0.6 and 3 ms using compressed nitrogen. This device is used for short-duration blast overpressure loading for small animal in vivo injury models, and contrasts the more frequently used long duration/high impulse blast overpressures in the literature. We also developed a new apparatus that is used with the shock tube to recreate the in vivo intracranial overpressure response for loading in vitro culture preparations. The receiver device surrounds the culture with materials of similar impedance to facilitate the propagation of a single overpressure pulse through the tissue. This method prevents pressure waves reflecting off the tissue that can cause unrealistic deformation and injury. The receiver performance was characterized using the longest helium-driven shock tube, and produced in-fluid overpressures up to 1500 kPa at the location where a culture would be placed. This response was well correlated with the overpressure conditions from the shock tube (R2 = 0.97). Finite element models of the shock tube and receiver were developed and validated to better elucidate the mechanics of this methodology. A demonstration exposing a culture to the loading conditions created by this system suggest tissue strains less than 5% for all pressure levels simulated, which was well below functional deficit thresholds for strain rates less than 50 s−1. This novel system is not limited to a specific type of culture model and can be modified to reproduce more complex pressure pulses. PMID:22470367

Reshocks, rarefactions, and the generalized Layzer model for hydrodynamic instabilities

NASA Astrophysics Data System (ADS)

Mikaelian, Karnig O.

2009-02-01

We report numerical simulations and analytic modeling of shock tube experiments on Rayleigh-Taylor and Richtmyer-Meshkov instabilities. We examine single interfaces of the type A /B where the incident shock is initiated in A and the transmitted shock proceeds into B. Examples are He/air and air/He. In addition, we study finite-thickness or double-interface A /B/A configurations such as air/SF6/air gas-curtain experiments. We first consider conventional shock tubes that have a "fixed" boundary: A solid endwall which reflects the transmitted shock and reshocks the interface(s). Then we focus on new experiments with a "free" boundary—a membrane disrupted mechanically or by the transmitted shock, sending back a rarefaction toward the interface(s). Complex acceleration histories are achieved, relevant for inertial confinement fusion implosions. We compare our simulation results with a generalized Layzer model for two fluids with time-dependent densities and derive a new freeze-out condition whereby accelerating and compressive forces cancel each other out. Except for the recently reported failures of the Layzer model, the generalized Layzer model and hydrocode simulations for reshocks and rarefactions agree well with each other and remain to be verified experimentally.

ρ-VOF: An interface sharpening method for gas-liquid flow simulation

NASA Astrophysics Data System (ADS)

Wang, Jiantao; Liu, Gang; Jiang, Xiong; Mou, Bin

2018-05-01

The study on simulation of compressible gas-liquid flow remains open. Popular methods are either confined to incompressible flow regime, or inevitably induce smear of the free interface. A new finite volume method for compressible two-phase flow simulation is contributed for this subject. First, the “heterogeneous equilibrium” assumption is introduced to the control volume, by hiring free interface reconstruction technology, the distribution of each component in the control volume is achieved. Next, AUSM+-up (advection upstream splitting method) scheme is employed to calculate the convective fluxes and pressure fluxes, with the contact discontinuity characteristic considered, followed by the update of the whole flow field. The new method features on density-based pattern and interface reconstruction technology from VOF (volume of fluid), thus we name it “ρ-VOF method”. Inherited from AUSM families and VOF, ρ-VOF behaves as an all-speed method, capable of simulating shock in gas-liquid flow, and preserving the sharpness of the free interface. Gas-liquid shock tube is simulated to evaluate the method, from which good agreement is obtained between the predicted results and those of the cited literature, meanwhile, sharper free interface is identified. Finally, the capability and validity of ρ-VOF method can be concluded in compressible gas-liquid flow simulation.

X-ray scattering measurements of dissociation-induced metallization of dynamically compressed deuterium

DOE PAGES

Davis, P.; Döppner, T.; Rygg, J. R.; ...

2016-04-18

Hydrogen, the simplest element in the universe, has a surprisingly complex phase diagram. Because of applications to planetary science, inertial confinement fusion and fundamental physics, its high-pressure properties have been the subject of intense study over the past two decades. While sophisticated static experiments have probed hydrogen’s structure at ever higher pressures, studies examining the higher-temperature regime using dynamic compression have mostly been limited to optical measurement techniques. Here we present spectrally resolved x-ray scattering measurements from plasmons in dynamically compressed deuterium. Combined with Compton scattering, and velocity interferometry to determine shock pressure and mass density, this allows us tomore » extract ionization state as a function of compression. Furthermore, the onset of ionization occurs close in pressure to where density functional theory-molecular dynamics (DFT-MD) simulations show molecular dissociation, suggesting hydrogen transitions from a molecular and insulating fluid to a conducting state without passing through an intermediate atomic phase.« less

A Mass Tracking Formulation for Bubbles in Incompressible Flow

DTIC Science & Technology

2012-10-14

incompressible flow to fully nonlinear compressible flow including the effects of shocks and rarefactions , and then subsequently making a number of...using the ideas from [19] to couple together incompressible flow with fully nonlinear compressible flow including shocks and rarefactions . The results...compressible flow including the effects of shocks and rarefactions , and then subsequently making a number of simplifying assumptions on the air flow

Laser shock compression experiments on precompressed water in ``SG-II'' laser facility

NASA Astrophysics Data System (ADS)

Shu, Hua; Huang, Xiuguang; Ye, Junjian; Fu, Sizu

2017-06-01

Laser shock compression experiments on precompressed samples offer the possibility to obtain new hugoniot data over a significantly broader range of density-temperature phase than was previously achievable. This technique was developed in ``SG-II'' laser facility. Hugoniot data were obtained for water in 300 GPa pressure range by laser-driven shock compression of samples statically precompressed in diamond-anvil cells.

A cut-cell finite volume – finite element coupling approach for fluid–structure interaction in compressible flow

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

Pasquariello, Vito, E-mail: vito.pasquariello@tum.de; Hammerl, Georg; Örley, Felix

2016-02-15

We present a loosely coupled approach for the solution of fluid–structure interaction problems between a compressible flow and a deformable structure. The method is based on staggered Dirichlet–Neumann partitioning. The interface motion in the Eulerian frame is accounted for by a conservative cut-cell Immersed Boundary method. The present approach enables sub-cell resolution by considering individual cut-elements within a single fluid cell, which guarantees an accurate representation of the time-varying solid interface. The cut-cell procedure inevitably leads to non-matching interfaces, demanding for a special treatment. A Mortar method is chosen in order to obtain a conservative and consistent load transfer. Wemore » validate our method by investigating two-dimensional test cases comprising a shock-loaded rigid cylinder and a deformable panel. Moreover, the aeroelastic instability of a thin plate structure is studied with a focus on the prediction of flutter onset. Finally, we propose a three-dimensional fluid–structure interaction test case of a flexible inflated thin shell interacting with a shock wave involving large and complex structural deformations.« less

Multiple shock reverberation compression of dense Ne up to the warm dense regime: Evaluating the theoretical models

NASA Astrophysics Data System (ADS)

Tang, J.; Gu, Y. J.; Chen, Q. F.; Li, Z. G.; Zheng, J.; Li, C. J.; Li, J. T.

2018-04-01

Multiple shock reverberation compression experiments are designed and performed to determine the equation of state of neon ranging from the initial dense gas up to the warm dense regime where the pressure is from about 40 MPa to 120 GPa and the temperature is from about 297 K up to above 20 000 K. The wide region experimental data are used to evaluate the available theoretical models. It is found that, for neon below 1.1 g/cm 3 , within the framework of density functional theory molecular dynamics, a van der Waals correction is meaningful. Under high pressure and temperature, results from the self-consistent fluid variational theory model are sensitive to the potential parameter and could give successful predictions in the whole experimental regime if a set of proper parameters is employed. The new observations on neon under megabar (1 Mbar =1011Pa ) pressure and eV temperature (1 eV ≈104K ) enrich the understanding on properties of warm dense matter and have potential applications in revealing the formation and evolution of gaseous giants or mega-Earths.

Bimodal pair f-KdV dynamics in star-forming clouds

NASA Astrophysics Data System (ADS)

Karmakar, Pralay Kumar; Haloi, Archana; Roy, Supriya

2018-04-01

A theoretical formalism for investigating the bimodal conjugational mode dynamics of hybrid source, dictated by a unique pair of forced Korteweg-de Vries (f-KdV) equations in a complex turbo-magnetized star-forming cloud, is reported. It uses a standard multi-scale analysis executed over the cloud-governing equations in a closure form to derive the conjugated pair f-KdV system. We numerically see the structural features of two distinctive classes of eigenmode patterns stemming from the conjoint gravito-electrostatic interplay. The electrostatic compressive monotonic aperiodic shock-like patterns and gravitational compressive non-monotonic oscillatory shock-like structures are excitable. It is specifically revealed that the constitutive grain-charge (grain-mass) acts as electrostatic stabilizer (gravitational destabilizer) against the global cloud collapse dynamics. The basic features of the nonlinear coherent structures are confirmed in systematic phase-plane landscapes, indicating electrostatic irregular non-homoclinic open trajectories and gravitational atypical non-chaotic homoclinic fixed-point attractors. The relevance in the real astro-cosmic scenarios of the early phases of structure formation via wave-driven fluid-accretive transport processes is summarily emphasized.

Effect of shock waves on the statistics and scaling in compressible isotropic turbulence

NASA Astrophysics Data System (ADS)

Wang, Jianchun; Wan, Minping; Chen, Song; Xie, Chenyue; Chen, Shiyi

2018-04-01

The statistics and scaling of compressible isotropic turbulence in the presence of large-scale shock waves are investigated by using numerical simulations at turbulent Mach number Mt ranging from 0.30 to 0.65. The spectra of the compressible velocity component, density, pressure, and temperature exhibit a k-2 scaling at different turbulent Mach numbers. The scaling exponents for structure functions of the compressible velocity component and thermodynamic variables are close to 1 at high orders n ≥3 . The probability density functions of increments of the compressible velocity component and thermodynamic variables exhibit a power-law region with the exponent -2 . Models for the conditional average of increments of the compressible velocity component and thermodynamic variables are developed based on the ideal shock relations and are verified by numerical simulations. The overall statistics of the compressible velocity component and thermodynamic variables are similar to one another at different turbulent Mach numbers. It is shown that the effect of shock waves on the compressible velocity spectrum and kinetic energy transfer is different from that of acoustic waves.

RIACS

NASA Technical Reports Server (NTRS)

Oliger, Joseph

1997-01-01

Topics considered include: high-performance computing; cognitive and perceptual prostheses (computational aids designed to leverage human abilities); autonomous systems. Also included: development of a 3D unstructured grid code based on a finite volume formulation and applied to the Navier-stokes equations; Cartesian grid methods for complex geometry; multigrid methods for solving elliptic problems on unstructured grids; algebraic non-overlapping domain decomposition methods for compressible fluid flow problems on unstructured meshes; numerical methods for the compressible navier-stokes equations with application to aerodynamic flows; research in aerodynamic shape optimization; S-HARP: a parallel dynamic spectral partitioner; numerical schemes for the Hamilton-Jacobi and level set equations on triangulated domains; application of high-order shock capturing schemes to direct simulation of turbulence; multicast technology; network testbeds; supercomputer consolidation project.

Astrophysical Flows

NASA Astrophysics Data System (ADS)

Pringle, James E.; King, Andrew

2003-07-01

Almost all conventional matter in the Universe is fluid, and fluid dynamics plays a crucial role in astrophysics. This new graduate textbook provides a basic understanding of the fluid dynamical processes relevant to astrophysics. The mathematics used to describe these processes is simplified to bring out the underlying physics. The authors cover many topics, including wave propagation, shocks, spherical flows, stellar oscillations, the instabilities caused by effects such as magnetic fields, thermal driving, gravity, shear flows, and the basic concepts of compressible fluid dynamics and magnetohydrodynamics. The authors are Directors of the UK Astrophysical Fluids Facility (UKAFF) at the University of Leicester, and editors of the Cambridge Astrophysics Series. This book has been developed from a course in astrophysical fluid dynamics taught at the University of Cambridge. It is suitable for graduate students in astrophysics, physics and applied mathematics, and requires only a basic familiarity with fluid dynamics.• Provides coverage of the fundamental fluid dynamical processes an astrophysical theorist needs to know • Introduces new mathematical theory and techniques in a straightforward manner • Includes end-of-chapter problems to illustrate the course and introduce additional ideas

Simulation of the effects of cavitation and anatomy in the shock path of model lithotripters

PubMed Central

Krimmel, Jeff; Colonius, Tim; Tanguay, Michel

2011-01-01

We report on recent efforts to develop predictive models for the pressure and other flow variables in the focal region of shock wave lithotripters. Baseline simulations of three representative lithotripters (electrohydraulic, electromagnetic, and piezoelectric) compare favorably with in vitro experiments (in a water bath). We proceed to model and investigate how shock focusing is altered by the presence of material interfaces associated with different types of tissue encountered along the shock path, and by the presence of cavitation bubbles that are excited by tensile pressures associated with the focused shock wave. We use human anatomical data, but simplify the description by assuming that the tissue behaves as a fluid, and by assuming cylindrical symmetry along the shock path. Scattering by material interfaces is significant, and regions of high pressure amplitudes (both compressive and tensile) are generated almost 4 cm postfocus. Bubble dynamics generate secondary shocks whose strength depends on the density of bubbles and the pulse repetition frequency (PRF). At sufficiently large densities, the bubbles also attenuate the shock. Together with experimental evidence, the simulations suggest that high PRF may be counter-productive for stone comminution. Finally, we discuss how the lithotripter simulations can be used as input to more detailed physical models that attempt to characterize the mechanisms by which collapsing cavitation models erode stones, and by which shock waves and bubbles may damage tissue. PMID:21063697

The effect of shock dynamics on compressibility of ignition-scale National Ignition Facility implosions

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

Zylstra, A. B.; Frenje, J. A.; Séguin, F. H.

The effects of shock dynamics on compressibility of indirect-drive ignition-scale surrogate implosions, CH shells filled with D 3He gas, have been studied using charged-particle spectroscopy. Spectral measurements of D 3He protons produced at the shock-bang time probe the shock dynamics and in-flight characteristics of an implosion. The proton shock yield is found to vary by over an order of magnitude. A simple model relates the observed yield to incipient hot-spot adiabat, suggesting that implosions with rapid radiation-power increase during the main drive pulse may have a 2x higher hot-spot adiabat, potentially reducing compressibility. A self-consistent 1-D implosion model was usedmore » to infer the areal density (pR) and the shell center-of-mass radius (R cm) from the downshift of the shock-produced D 3He protons. The observed pR at shock-bang time is substantially higher for implosions, where the laser drive is on until near the compression bang time ('short-coast'), while longer-coasting implosions have lower pR. This corresponds to a much larger temporal difference between the shock- and compression-bang time in the long-coast implosions (~800 ps) than in the short-coast (~400 ps); this will be verified with a future direct bang-time diagnostic. This model-inferred differential bang time contradicts radiation-hydrodynamic simulations, which predict constant 700–800 ps differential independent of coasting time. This result is potentially explained by uncertainties in modeling late-time ablation drive on the capsule. In an ignition experiment, an earlier shock-bang time resulting in an earlier onset of shell deceleration, potentially reducing compression and, thus, fuel pR.« less

The effect of shock dynamics on compressibility of ignition-scale National Ignition Facility implosions

DOE PAGES

Zylstra, A. B.; Frenje, J. A.; Séguin, F. H.; ...

2014-11-03

The effects of shock dynamics on compressibility of indirect-drive ignition-scale surrogate implosions, CH shells filled with D 3He gas, have been studied using charged-particle spectroscopy. Spectral measurements of D 3He protons produced at the shock-bang time probe the shock dynamics and in-flight characteristics of an implosion. The proton shock yield is found to vary by over an order of magnitude. A simple model relates the observed yield to incipient hot-spot adiabat, suggesting that implosions with rapid radiation-power increase during the main drive pulse may have a 2x higher hot-spot adiabat, potentially reducing compressibility. A self-consistent 1-D implosion model was usedmore » to infer the areal density (pR) and the shell center-of-mass radius (R cm) from the downshift of the shock-produced D 3He protons. The observed pR at shock-bang time is substantially higher for implosions, where the laser drive is on until near the compression bang time ('short-coast'), while longer-coasting implosions have lower pR. This corresponds to a much larger temporal difference between the shock- and compression-bang time in the long-coast implosions (~800 ps) than in the short-coast (~400 ps); this will be verified with a future direct bang-time diagnostic. This model-inferred differential bang time contradicts radiation-hydrodynamic simulations, which predict constant 700–800 ps differential independent of coasting time. This result is potentially explained by uncertainties in modeling late-time ablation drive on the capsule. In an ignition experiment, an earlier shock-bang time resulting in an earlier onset of shell deceleration, potentially reducing compression and, thus, fuel pR.« less

Time-resolved Sensing of Meso-scale Shock Compression with Multilayer Photonic Crystal Structures

NASA Astrophysics Data System (ADS)

Scripka, David; Lee, Gyuhyon; Summers, Christopher J.; Thadhani, Naresh

2017-06-01

Multilayer Photonic Crystal structures can provide spatially and temporally resolved data needed to validate theoretical and computational models relevant for understanding shock compression in heterogeneous materials. Two classes of 1-D photonic crystal multilayer structures were studied: optical microcavities (OMC) and distributed Bragg reflectors (DBR). These 0.5 to 5 micron thick structures were composed of SiO2, Al2O3, Ag, and PMMA layers fabricated primarily via e-beam evaporation. The multilayers have unique spectral signatures inherently linked to their time-resolved physical states. By observing shock-induced changes in these signatures, an optically-based pressure sensor was developed. Results to date indicate that both OMCs and DBRs exhibit nanosecond-resolved spectral shifts of several to 10s of nanometers under laser-driven shock compression loads of 0-10 GPa, with the magnitude of the shift strongly correlating to the shock load magnitude. Additionally, spatially and temporally resolved spectral shifts under heterogeneous laser-driven shock compression created by partial beam blocking have been successfully demonstrated. These results illustrate the potential for multilayer structures to serve as meso-scale sensors, capturing temporal and spatial pressure profile evolutions in shock-compressed heterogeneous materials, and revealing meso-scale pressure distributions across a shocked surface. Supported by DTRA Grant HDTRA1-12-1-005 and DoD, AFOSR, National Defense Science and Eng. Graduate Fellowship, 32 CFR 168a.

Experimental growth of inertial forced Richtmyer-Meshkov instabilities for different Atwood numbers

NASA Astrophysics Data System (ADS)

Redondo, J. M.; Castilla, R.

2009-04-01

Richtmyer-Meshkov instability occurs when a shock wave impinges on an interface separating two fluids having different densities [1,2]. The instability causes perturbations on the interface to grow, bubbles and spikes, producing vortical structures which potentially result in a turbulent mixing layer. In addition to shock tube experiments, the incompressible Richtmyer-Meshkov instability has also been studied by impulsively accelerating containers of incompressible fluids. Castilla and Redondo (1994) [3] first exploited this technique by dropping tanks containing a liquid and air or two liquids onto a cushioned surface. This technique was improved upon by Niederhaus and Jacobs (2003)[4] by mounting the tank onto a rail system and then allowing it to bounce off of a fixed spring. A range of both miscible and inmiscible liquids were used, giving a wide range of Atwood numbers using the combinations of air, water, alcohol, oil and mercury. Experimental results show the different pattern selection of both the bubbles and spikes for the different Atwood numbers. Visual analysis of the marked interfaces allows to distinguish the regions of strong mixing and compare self-similarity growth of the mixing region. [1] Meshkov, E. E. 1969 Instability of the interface of two gases accelerated by a shock wave. Fluid Dynamics 4, 101-104. [2] Brouillette, M. & Sturtevant, B. 1994 Experiments on the Richtmyer-Meshkov instability: single-scale perturbations on a continuous interface. Journal of Fluid Mechanics 263, 271-292. [3] Castilla, R. & Redondo, J. M. 1994 Mixing Front Growth in RT and RM Instabilities. Proceedings of the Fourth International Workshop on the Physics of Compressible Turbulent Mixing, Cambridge, United Kingdom, edited by P. F. Linden, D. L. Youngs, and S. B. Dalziel, 11-31. [4] Niederhaus, C. E. & Jacobs, J. W. 2003 Experimental study of the Richtmyer-Meshkov instability of incompressible fluids. Journal of Fluid Mechanics 485, 243-277.

A sharp interface method for compressible liquid–vapor flow with phase transition and surface tension

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

Fechter, Stefan, E-mail: stefan.fechter@iag.uni-stuttgart.de; Munz, Claus-Dieter, E-mail: munz@iag.uni-stuttgart.de; Rohde, Christian, E-mail: Christian.Rohde@mathematik.uni-stuttgart.de

The numerical approximation of non-isothermal liquid–vapor flow within the compressible regime is a difficult task because complex physical effects at the phase interfaces can govern the global flow behavior. We present a sharp interface approach which treats the interface as a shock-wave like discontinuity. Any mixing of fluid phases is avoided by using the flow solver in the bulk regions only, and a ghost-fluid approach close to the interface. The coupling states for the numerical solution in the bulk regions are determined by the solution of local two-phase Riemann problems across the interface. The Riemann solution accounts for the relevantmore » physics by enforcing appropriate jump conditions at the phase boundary. A wide variety of interface effects can be handled in a thermodynamically consistent way. This includes surface tension or mass/energy transfer by phase transition. Moreover, the local normal speed of the interface, which is needed to calculate the time evolution of the interface, is given by the Riemann solution. The interface tracking itself is based on a level-set method. The focus in this paper is the description of the two-phase Riemann solver and its usage within the sharp interface approach. One-dimensional problems are selected to validate the approach. Finally, the three-dimensional simulation of a wobbling droplet and a shock droplet interaction in two dimensions are shown. In both problems phase transition and surface tension determine the global bulk behavior.« less

Molecular dynamics simulation of the plastic behavior anisotropy of shock-compressed monocrystal nickel

NASA Astrophysics Data System (ADS)

Chen, Ya-Zhou; Zhou, Liu-Cheng; He, Wei-Feng; Sun, Yu; Li, Ying-Hong; Jiao, Yang; Luo, Si-Hai

2017-01-01

Molecular dynamics simulations were used to study the plastic behavior of monocrystalline nickel under shock compression along the [100] and [110] orientations. The shock Hugoniot relation, local stress curve, and process of microstructure development were determined. Results showed the apparent anisotropic behavior of monocrystalline nickel under shock compression. The separation of elastic and plastic waves was also obvious. Plastic deformation was more severely altered along the [110] direction than the [100] direction. The main microstructure phase transformed from face-centered cubic to body-centered cubic and generated a large-scale and low-density stacking fault along the family of { 111 } crystal planes under shock compression along the [100] direction. By contrast, the main mechanism of plastic deformation in the [110] direction was the nucleation of the hexagonal, close-packed phase, which generated a high density of stacking faults along the [110] and [1̅10] directions.

Radiative shocks produced from spherical cryogenic implosions at the National Ignition Facilitya)

NASA Astrophysics Data System (ADS)

Pak, A.; Divol, L.; Gregori, G.; Weber, S.; Atherton, J.; Bennedetti, R.; Bradley, D. K.; Callahan, D.; Casey, D. T.; Dewald, E.; Döppner, T.; Edwards, M. J.; Frenje, J. A.; Glenn, S.; Grim, G. P.; Hicks, D.; Hsing, W. W.; Izumi, N.; Jones, O. S.; Johnson, M. G.; Khan, S. F.; Kilkenny, J. D.; Kline, J. L.; Kyrala, G. A.; Lindl, J.; Landen, O. L.; Le Pape, S.; Ma, T.; MacPhee, A.; MacGowan, B. J.; MacKinnon, A. J.; Masse, L.; Meezan, N. B.; Moody, J. D.; Olson, R. E.; Ralph, J. E.; Robey, H. F.; Park, H.-S.; Remington, B. A.; Ross, J. S.; Tommasini, R.; Town, R. P. J.; Smalyuk, V.; Glenzer, S. H.; Moses, E. I.

2013-05-01

Spherically expanding radiative shock waves have been observed from inertially confined implosion experiments at the National Ignition Facility. In these experiments, a spherical fusion target, initially 2 mm in diameter, is compressed via the pressure induced from the ablation of the outer target surface. At the peak compression of the capsule, x-ray and nuclear diagnostics indicate the formation of a central core, with a radius and ion temperature of ˜20 μm and ˜ 2 keV, respectively. This central core is surrounded by a cooler compressed shell of deuterium-tritium fuel that has an outer radius of ˜40 μm and a density of >500 g/cm3. Using inputs from multiple diagnostics, the peak pressure of the compressed core has been inferred to be of order 100 Gbar for the implosions discussed here. The shock front, initially located at the interface between the high pressure compressed fuel shell and surrounding in-falling low pressure ablator plasma, begins to propagate outwards after peak compression has been reached. Approximately 200 ps after peak compression, a ring of x-ray emission created by the limb-brightening of a spherical shell of shock-heated matter is observed to appear at a radius of ˜100 μm. Hydrodynamic simulations, which model the experiment and include radiation transport, indicate that the sudden appearance of this emission occurs as the post-shock material temperature increases and upstream density decreases, over a scale length of ˜10 μm, as the shock propagates into the lower density (˜1 g/cc), hot (˜250 eV) plasma that exists at the ablation front. The expansion of the shock-heated matter is temporally and spatially resolved and indicates a shock expansion velocity of ˜300 km/s in the laboratory frame. The magnitude and temporal evolution of the luminosity produced from the shock-heated matter was measured at photon energies between 5.9 and 12.4 keV. The observed radial shock expansion, as well as the magnitude and temporal evolution of the luminosity from the shock-heated matter, is consistent with 1-D radiation hydrodynamic simulations. Analytic estimates indicate that the radiation energy flux from the shock-heated matter is of the same order as the in-flowing material energy flux, and suggests that this radiation energy flux modifies the shock front structure. Simulations support these estimates and show the formation of a radiative shock, with a precursor that raises the temperature ahead of the shock front, a sharp μm-scale thick spike in temperature at the shock front, followed by a post-shock cooling layer.

Fast Electron Deposition in Laser Shock Compressed Plastic Targets

NASA Astrophysics Data System (ADS)

Hall, T. A.; Ellwi, S.; Batani, D.; Bernardinello, A.; Masella, V.; Koenig, M.; Benuzzi, A.; Krishnan, J.; Pisani, F.; Djaoui, A.; Norreys, P.; Neely, D.; Rose, S.; Key, M. H.; Fews, P.

1998-08-01

We present the first results of fast electron deposition in a laser shock compressed plasma. The interaction of a 3 ps, 15 J laser pulse with solid polyethylene targets is used to produce fast electrons on one side of foil targets and a 2 ns duration laser pulse is used to drive a shock wave into the target from the opposite side. Kα emission from chlorine fluor buried layers is used to measure the electron transport. The hot electron range in the shock compressed plastic is found to be approximately twice as large as the range in the solid density plastic.

On the dynamics of a shock-bubble interaction

NASA Technical Reports Server (NTRS)

Quirk, James J.; Karni, Smadar

1994-01-01

We present a detailed numerical study of the interaction of a weak shock wave with an isolated cylindrical gas inhomogenity. Such interactions have been studied experimentally in an attempt to elucidate the mechanisms whereby shock waves propagating through random media enhance mixing. Our study concentrates on the early phases of the interaction process which are dominated by repeated refractions of acoustic fronts at the bubble interface. Specifically, we have reproduced two of the experiments performed by Haas and Sturtevant : M(sub s) = 1.22 planar shock wave, moving through air, impinges on a cylindrical bubble which contains either helium or Refrigerant 22. These flows are modelled using the two-dimensional, compressible Euler equations for a two component fluid (air-helium or air-Refrigerant 22). Although simulations of shock wave phenomena are now fairly commonplace, they are mostly restricted to single component flows. Unfortunately, multi-component extensions of successful single component schemes often suffer from spurious oscillations which are generated at material interfaces. Here we avoid such problems by employing a novel, nonconservative shock-capturing scheme. In addition, we have utilized a sophisticated adaptive mesh refinement algorithm which enables extremely high resolution simulations to be performed relatively cheaply. Thus we have been able to reproduce numerically all the intricate mechanisms that were observed experimentally (e.g., transitions from regular to irregular refraction, cusp formation and shock wave focusing, multi-shock and Mach shock structures, jet formation, etc.), and we can now present an updated description for the dynamics of a shock-bubble interaction.

Shock waves in weakly compressed granular media.

PubMed

van den Wildenberg, Siet; van Loo, Rogier; van Hecke, Martin

2013-11-22

We experimentally probe nonlinear wave propagation in weakly compressed granular media and observe a crossover from quasilinear sound waves at low impact to shock waves at high impact. We show that this crossover impact grows with the confining pressure P0, whereas the shock wave speed is independent of P0-two hallmarks of granular shocks predicted recently. The shocks exhibit surprising power law attenuation, which we model with a logarithmic law implying that shock dissipation is weak and qualitatively different from other granular dissipation mechanisms. We show that elastic and potential energy balance in the leading part of the shocks.

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.

Mach 5 bow shock control by a nanosecond pulse surface dielectric barrier discharge

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

Nishihara, M.; Takashima, K.; Rich, J. W.

2011-06-15

Bow shock perturbations in a Mach 5 air flow, produced by low-temperature, nanosecond pulse, and surface dielectric barrier discharge (DBD), are detected by phase-locked schlieren imaging. A diffuse nanosecond pulse discharge is generated in a DBD plasma actuator on a surface of a cylinder model placed in air flow in a small scale blow-down supersonic wind tunnel. Discharge energy coupled to the actuator is 7.3-7.8 mJ/pulse. Plasma temperature inferred from nitrogen emission spectra is a few tens of degrees higher than flow stagnation temperature, T = 340 {+-} 30 K. Phase-locked Schlieren images are used to detect compression waves generatedmore » by individual nanosecond discharge pulses near the actuator surface. The compression wave propagates upstream toward the baseline bow shock standing in front of the cylinder model. Interaction of the compression wave and the bow shock causes its displacement in the upstream direction, increasing shock stand-off distance by up to 25%. The compression wave speed behind the bow shock and the perturbed bow shock velocity are inferred from the Schlieren images. The effect of compression waves generated by nanosecond discharge pulses on shock stand-off distance is demonstrated in a single-pulse regime (at pulse repetition rates of a few hundred Hz) and in a quasi-continuous mode (using a two-pulse sequence at a pulse repetition rate of 100 kHz). The results demonstrate feasibility of hypersonic flow control by low-temperature, repetitive nanosecond pulse discharges.« less

Adaptive mesh fluid simulations on GPU

NASA Astrophysics Data System (ADS)

Wang, Peng; Abel, Tom; Kaehler, Ralf

2010-10-01

We describe an implementation of compressible inviscid fluid solvers with block-structured adaptive mesh refinement on Graphics Processing Units using NVIDIA's CUDA. We show that a class of high resolution shock capturing schemes can be mapped naturally on this architecture. Using the method of lines approach with the second order total variation diminishing Runge-Kutta time integration scheme, piecewise linear reconstruction, and a Harten-Lax-van Leer Riemann solver, we achieve an overall speedup of approximately 10 times faster execution on one graphics card as compared to a single core on the host computer. We attain this speedup in uniform grid runs as well as in problems with deep AMR hierarchies. Our framework can readily be applied to more general systems of conservation laws and extended to higher order shock capturing schemes. This is shown directly by an implementation of a magneto-hydrodynamic solver and comparing its performance to the pure hydrodynamic case. Finally, we also combined our CUDA parallel scheme with MPI to make the code run on GPU clusters. Close to ideal speedup is observed on up to four GPUs.

Traveling waves in Hall-magnetohydrodynamics and the ion-acoustic shock structure

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

Hagstrom, George I.; Hameiri, Eliezer

Hall-magnetohydrodynamics (HMHD) is a mixed hyperbolic-parabolic partial differential equation that describes the dynamics of an ideal two fluid plasma with massless electrons. We study the only shock wave family that exists in this system (the other discontinuities being contact discontinuities and not shocks). We study planar traveling wave solutions and we find solutions with discontinuities in the hydrodynamic variables, which arise due to the presence of real characteristics in Hall-MHD. We introduce a small viscosity into the equations and use the method of matched asymptotic expansions to show that solutions with a discontinuity satisfying the Rankine-Hugoniot conditions and also anmore » entropy condition have continuous shock structures. The lowest order inner equations reduce to the compressible Navier-Stokes equations, plus an equation which implies the constancy of the magnetic field inside the shock structure. We are able to show that the current is discontinuous across the shock, even as the magnetic field is continuous, and that the lowest order outer equations, which are the equations for traveling waves in inviscid Hall-MHD, are exactly integrable. We show that the inner and outer solutions match, which allows us to construct a family of uniformly valid continuous composite solutions that become discontinuous when the diffusivity vanishes.« less

Progress in the Development of a Class of Efficient Low Dissipative High Order Shock-capturing Methods

NASA Technical Reports Server (NTRS)

Yee, H. C.; Sjogreen, B.; Sandham, N. D.; Hadjadj, A.; Kwak, Dochan (Technical Monitor)

2000-01-01

In a series of papers, Olsson (1994, 1995), Olsson & Oliger (1994), Strand (1994), Gerritsen Olsson (1996), Yee et al. (1999a,b, 2000) and Sandham & Yee (2000), the issue of nonlinear stability of the compressible Euler and Navier-Stokes Equations, including physical boundaries, and the corresponding development of the discrete analogue of nonlinear stable high order schemes, including boundary schemes, were developed, extended and evaluated for various fluid flows. High order here refers to spatial schemes that are essentially fourth-order or higher away from shock and shear regions. The objective of this paper is to give an overview of the progress of the low dissipative high order shock-capturing schemes proposed by Yee et al. (1999a,b, 2000). This class of schemes consists of simple non-dissipative high order compact or non-compact central spatial differencings and adaptive nonlinear numerical dissipation operators to minimize the use of numerical dissipation. The amount of numerical dissipation is further minimized by applying the scheme to the entropy splitting form of the inviscid flux derivatives, and by rewriting the viscous terms to minimize odd-even decoupling before the application of the central scheme (Sandham & Yee). The efficiency and accuracy of these scheme are compared with spectral, TVD and fifth- order WENO schemes. A new approach of Sjogreen & Yee (2000) utilizing non-orthogonal multi-resolution wavelet basis functions as sensors to dynamically determine the appropriate amount of numerical dissipation to be added to the non-dissipative high order spatial scheme at each grid point will be discussed. Numerical experiments of long time integration of smooth flows, shock-turbulence interactions, direct numerical simulations of a 3-D compressible turbulent plane channel flow, and various mixing layer problems indicate that these schemes are especially suitable for practical complex problems in nonlinear aeroacoustics, rotorcraft dynamics, direct numerical simulation or large eddy simulation of compressible turbulent flows at various speeds including high-speed shock-turbulence interactions, and general long time wave propagation problems. These schemes, including entropy splitting, have also been extended to freestream preserving schemes on curvilinear moving grids for a thermally perfect gas (Vinokur & Yee 2000).

General relativistic study of astrophysical jets with internal shocks

NASA Astrophysics Data System (ADS)

Vyas, Mukesh K.; Chattopadhyay, Indranil

2017-08-01

We explore the possibility of the formation of steady internal shocks in jets around black holes. We consider a fluid described by a relativistic equation of state, flowing about the axis of symmetry (θ = 0) in a Schwarzschild metric. We use two models for the jet geometry: (I) a conical geometry and (II) a geometry with non-conical cross-section. A jet with conical geometry has a smooth flow, while the jet with non-conical cross-section undergoes multiple sonic points and even standing shock. The jet shock becomes stronger, as the shock location is situated farther from the central black hole. Jets with very high energy and very low energy do not harbour shocks, but jets with intermediate energies do harbour shocks. One advantage of these shocks, as opposed to shocks mediated by external medium, is that these shocks have no effect on the jet terminal speed, but may act as possible sites for particle acceleration. Typically, a jet with specific energy 1.8c2 will achieve a terminal speed of v∞ = 0.813c for jet with any geometry, where, c is the speed of light in vacuum. But for a jet of non-conical cross-section for which the length scale of the inner torus of the accretion disc is 40rg, then, in addition, a steady shock will form at rsh ˜ 7.5rg and compression ratio of R ˜ 2.7. Moreover, electron-proton jet seems to harbour the strongest shock. We will discuss possible consequences of such a scenario.

Cascades and Dissipative Anomalies in Compressible Fluid Turbulence

NASA Astrophysics Data System (ADS)

Eyink, Gregory L.; Drivas, Theodore D.

2018-02-01

We investigate dissipative anomalies in a turbulent fluid governed by the compressible Navier-Stokes equation. We follow an exact approach pioneered by Onsager, which we explain as a nonperturbative application of the principle of renormalization-group invariance. In the limit of high Reynolds and Péclet numbers, the flow realizations are found to be described as distributional or "coarse-grained" solutions of the compressible Euler equations, with standard conservation laws broken by turbulent anomalies. The anomalous dissipation of kinetic energy is shown to be due not only to local cascade but also to a distinct mechanism called pressure-work defect. Irreversible heating in stationary, planar shocks with an ideal-gas equation of state exemplifies the second mechanism. Entropy conservation anomalies are also found to occur via two mechanisms: an anomalous input of negative entropy (negentropy) by pressure work and a cascade of negentropy to small scales. We derive "4 /5 th-law"-type expressions for the anomalies, which allow us to characterize the singularities (structure-function scaling exponents) required to sustain the cascades. We compare our approach with alternative theories and empirical evidence. It is argued that the "Big Power Law in the Sky" observed in electron density scintillations in the interstellar medium is a manifestation of a forward negentropy cascade or an inverse cascade of usual thermodynamic entropy.

Sandia 25-meter compressed helium/air gun

NASA Astrophysics Data System (ADS)

Setchell, R. E.

1982-04-01

For nearly twenty years the Sandia 25-meter compressed gas gun has been an important tool for studying condensed materials subjected to transient shock compression. Major system modifications are now in progress to provide new control, instrumentation, and data acquisition capabilities. These features will ensure that the facility can continue as an effective means of investigating a variety of physical and chemical processes in shock-compressed solids.

Shock interaction with a two-gas interface in a novel dual-driver shock tube

NASA Astrophysics Data System (ADS)

Labenski, John R.

Fluid instabilities exist at the interface between two fluids having different densities if the flow velocity and density gradient are anti-parallel or if a shock wave crosses the boundary. The former case is called the Rayleigh-Taylor (R-T) instability and the latter, the Richtmyer-Meshkov (R-M) instability. Small initial perturbations on the interface destabilize and grow into larger amplitude structures leading to turbulent mixing. Instabilities of this type are seen in inertial confinement fusion (ICF) experiments, laser produced plasmas, supernova explosions, and detonations. A novel dual-driver shock tube was used to investigate the growth rate of the R-M instability. One driver is used to create an argon-refrigerant interface, and the other at the opposite end of the driven section generates a shock to force the interface with compressible flows behind the shock. The refrigerant gas in the first driver is seeded with sub-micron oil droplets for visualization of the interface. The interface travels down the driven section past the test section for a fixed amount of time. A stronger shock of Mach 1.1 to 1.3 drives the interface back past the test section where flow diagnostics are positioned. Two schlieren systems record the density fluctuations while light scattering detectors record the density of the refrigerant as a function of position over the interface. A pair of digital cameras take stereo images of the interface, as mapped out by the tracer particles under illumination by a Q-switched ruby laser. The amount of time that the interface is allowed to travel up the driven section determines the interaction time as a control. Comparisons made between the schlieren signals, light scattering detector outputs, and the images quantify the fingered characteristics of the interface and its growth due to shock forcing. The results show that the interface has a distribution of thickness and that the interaction with a shock further broadens the interface. The growth rate was found to exhibit a dependence on the shock strength.

Flowfield-Dependent Mixed Explicit-Implicit (FDMEL) Algorithm for Computational Fluid Dynamics

NASA Technical Reports Server (NTRS)

Garcia, S. M.; Chung, T. J.

1997-01-01

Despite significant achievements in computational fluid dynamics, there still remain many fluid flow phenomena not well understood. For example, the prediction of temperature distributions is inaccurate when temperature gradients are high, particularly in shock wave turbulent boundary layer interactions close to the wall. Complexities of fluid flow phenomena include transition to turbulence, relaminarization separated flows, transition between viscous and inviscid incompressible and compressible flows, among others, in all speed regimes. The purpose of this paper is to introduce a new approach, called the Flowfield-Dependent Mixed Explicit-Implicit (FDMEI) method, in an attempt to resolve these difficult issues in Computational Fluid Dynamics (CFD). In this process, a total of six implicitness parameters characteristic of the current flowfield are introduced. They are calculated from the current flowfield or changes of Mach numbers, Reynolds numbers, Peclet numbers, and Damkoehler numbers (if reacting) at each nodal point and time step. This implies that every nodal point or element is provided with different or unique numerical scheme according to their current flowfield situations, whether compressible, incompressible, viscous, inviscid, laminar, turbulent, reacting, or nonreacting. In this procedure, discontinuities or fluctuations of an variables between adjacent nodal points are determined accurately. If these implicitness parameters are fixed to certain numbers instead of being calculated from the flowfield information, then practically all currently available schemes of finite differences or finite elements arise as special cases. Some benchmark problems to be presented in this paper will show the validity, accuracy, and efficiency of the proposed methodology.

Shock formation in Ne, Ar, Kr, and Xe on deuterium gas puff implosions

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

Narkis, J.; Rahman, H. U.; Ney, P.

2016-12-29

1- and 2-D simulations of 1-cm radius, gas-puff liners of Ne, Ar, Kr, and Xe imploding onto a deuterium target are conducted using the discharge parameters for the Zebra (1 MA, 130 ns) driver using the resistive MHD code MACH2. This is an implementation of the Staged Z-pinch concept, in which the target is driven to high-energy-density first by shock compression launched by a diffused azimuthal magnetic field (J×B force), and then by the adiabatic compression as the liner converges on axis. During the run-in phase, the initial shock heating preheats the deuterium plasma, with a subsequent stable, adiabatic compressionmore » heating the target to high energy density. Shock compression of the target coincides with the development of a J×B force at the target/liner interface. Stronger B-field transport and earlier shock compression increases with higher-Z liners, which results in an earlier shock arrival on axis. As a result, delayed shock formation in lower-Z liners yields a relative increase in shock heating, however, the 2-D simulations show an increased target isolation from magneto-Rayleigh-Taylor instability penetration, suggesting that an optimal balance between these two effects is reached in an Ar or Kr liner, rather than with Xe.« less

Generalized conjugate-gradient methods for the Navier-Stokes equations

NASA Technical Reports Server (NTRS)

Ajmani, Kumud; Ng, Wing-Fai; Liou, Meng-Sing

1991-01-01

A generalized conjugate-gradient method is used to solve the two-dimensional, compressible Navier-Stokes equations of fluid flow. The equations are discretized with an implicit, upwind finite-volume formulation. Preconditioning techniques are incorporated into the new solver to accelerate convergence of the overall iterative method. The superiority of the new solver is demonstrated by comparisons with a conventional line Gauss-Siedel Relaxation solver. Computational test results for transonic flow (trailing edge flow in a transonic turbine cascade) and hypersonic flow (M = 6.0 shock-on-shock phenoena on a cylindrical leading edge) are presented. When applied to the transonic cascade case, the new solver is 4.4 times faster in terms of number of iterations and 3.1 times faster in terms of CPU time than the Relaxation solver. For the hypersonic shock case, the new solver is 3.0 times faster in terms of number of iterations and 2.2 times faster in terms of CPU time than the Relaxation solver.

Rayleigh-Taylor and Richtmyer-Meshkov Instabilities in Turbulent Regime

NASA Astrophysics Data System (ADS)

Dimonte, G.

1998-11-01

The Rayleigh-Taylor instability (RTI) and its shock driven analog, the Richtmyer-Meshkov instability (RMI), affect a wide variety of important phenomena from sub-terrainian to astrophysical environments. The ``fluids" are equally varied from plasmas and magnetic fields to elastic-plastic solids. In most applications, the instabilities occur with a complex acceleration history and evolve to a highly nonlinear state, making the theoretical description formidable. We will link the fluid and plasma regimes while describing the theoretical issues and basic experiments in different venues to isolate key physics issues. RMI experiments on the Nova laser investigate the affects of compressibility with strong radiatively driven shocks (Mach > 10) in near solid density plasmas of sub-millimeter scale. The growth of single sinusoidal and random 3-D perturbations are measured using backlit radiography. RTI experiments with the Linear Electric Motor (LEM) are conducted with a variety of acceleration (<< 10^4 m/s^2) histories and fluids of 10 cm scale. Turbulent RTI experiments with high Reynolds number liquids show self-similar growth which is characterized with laser induced fluorescence. LEM experiments with an elastic-plastic material (yogurt) exhibit a critical wavelength and amplitude for instability. The experimental results will be compared with linear and nonlinear theories and hydrodynamic simulations.

Magnetohydrodynamic simulation of the interaction between two interplanetary magnetic clouds and its consequent geoeffectiveness

NASA Astrophysics Data System (ADS)

Xiong, Ming; Zheng, Huinan; Wu, S. T.; Wang, Yuming; Wang, Shui

2007-11-01

Numerical studies of the interplanetary "multiple magnetic clouds (Multi-MC)" are performed by a 2.5-dimensional ideal magnetohydrodynamic (MHD) model in the heliospheric meridional plane. Both slow MC1 and fast MC2 are initially emerged along the heliospheric equator, one after another with different time intervals. The coupling of two MCs could be considered as the comprehensive interaction between two systems, each comprising of an MC body and its driven shock. The MC2-driven shock and MC2 body are successively involved into interaction with MC1 body. The momentum is transferred from MC2 to MC1. After the passage of MC2-driven shock front, magnetic field lines in MC1 medium previously compressed by MC2-driven shock are prevented from being restored by the MC2 body pushing. MC1 body undergoes the most violent compression from the ambient solar wind ahead, continuous penetration of MC2-driven shock through MC1 body, and persistent pushing of MC2 body at MC1 tail boundary. As the evolution proceeds, the MC1 body suffers from larger and larger compression, and its original vulnerable magnetic elasticity becomes stiffer and stiffer. So there exists a maximum compressibility of Multi-MC when the accumulated elasticity can balance the external compression. This cutoff limit of compressibility mainly decides the maximally available geoeffectiveness of Multi-MC because the geoeffectiveness enhancement of MCs interacting is ascribed to the compression. Particularly, the greatest geoeffectiveness is excited among all combinations of each MC helicity, if magnetic field lines in the interacting region of Multi-MC are all southward. Multi-MC completes its final evolutionary stage when the MC2-driven shock is merged with MC1-driven shock into a stronger compound shock. With respect to Multi-MC geoeffectiveness, the evolution stage is a dominant factor, whereas the collision intensity is a subordinate one. The magnetic elasticity, magnetic helicity of each MC, and compression between each other are the key physical factors for the formation, propagation, evolution, and resulting geoeffectiveness of interplanetary Multi-MC.

Waste Heat Approximation for Understanding Dynamic Compression in Nature and Experiments

NASA Astrophysics Data System (ADS)

Jeanloz, R.

2015-12-01

Energy dissipated during dynamic compression quantifies the residual heat left in a planet due to impact and accretion, as well as the deviation of a loading path from an ideal isentrope. Waste heat ignores the difference between the pressure-volume isentrope and Hugoniot in approximating the dissipated energy as the area between the Rayleigh line and Hugoniot (assumed given by a linear dependence of shock velocity on particle velocity). Strength and phase transformations are ignored: justifiably, when considering sufficiently high dynamic pressures and reversible transformations. Waste heat mis-estimates the dissipated energy by less than 10-20 percent for volume compressions under 30-60 percent. Specific waste heat (energy per mass) reaches 0.2-0.3 c02 at impact velocities 2-4 times the zero-pressure bulk sound velocity (c0), its maximum possible value being 0.5 c02. As larger impact velocities are implied for typical orbital velocities of Earth-like planets, and c02 ≈ 2-30 MJ/kg for rock, the specific waste heat due to accretion corresponds to temperature rises of about 3-15 x 103 K for rock: melting accompanies accretion even with only 20-30 percent waste heat retained. Impact sterilization is similarly quantified in terms of waste heat relative to the energy required to vaporize H2O (impact velocity of 7-8 km/s, or 4.5-5 c0, is sufficient). Waste heat also clarifies the relationship between shock, multi-shock and ramp loading experiments, as well as the effect of (static) pre-compression. Breaking a shock into 2 steps significantly reduces the dissipated energy, with minimum waste heat achieved for two equal volume compressions in succession. Breaking a shock into as few as 4 steps reduces the waste heat to within a few percent of zero, documenting how multi-shock loading approaches an isentrope. Pre-compression, being less dissipative than an initial shock to the same strain, further reduces waste heat. Multi-shock (i.e., high strain-rate) loading of pre-compressed samples may thus offer the closest approach to an isentrope, and therefore the most extreme compression at which matter can be studied at the "warm" temperatures of planetary interiors.

GASOLINE: Smoothed Particle Hydrodynamics (SPH) code

NASA Astrophysics Data System (ADS)

N-Body Shop

2017-10-01

Gasoline solves the equations of gravity and hydrodynamics in astrophysical problems, including simulations of planets, stars, and galaxies. It uses an SPH method that features correct mixing behavior in multiphase fluids and minimal artificial viscosity. This method is identical to the SPH method used in the ChaNGa code (ascl:1105.005), allowing users to extend results to problems requiring >100,000 cores. Gasoline uses a fast, memory-efficient O(N log N) KD-Tree to solve Poisson's Equation for gravity and avoids artificial viscosity in non-shocking compressive flows.

Refinement Of Hexahedral Cells In Euler Flow Computations

NASA Technical Reports Server (NTRS)

Melton, John E.; Cappuccio, Gelsomina; Thomas, Scott D.

1996-01-01

Topologically Independent Grid, Euler Refinement (TIGER) computer program solves Euler equations of three-dimensional, unsteady flow of inviscid, compressible fluid by numerical integration on unstructured hexahedral coordinate grid refined where necessary to resolve shocks and other details. Hexahedral cells subdivided, each into eight smaller cells, as needed to refine computational grid in regions of high flow gradients. Grid Interactive Refinement and Flow-Field Examination (GIRAFFE) computer program written in conjunction with TIGER program to display computed flow-field data and to assist researcher in verifying specified boundary conditions and refining grid.

The History of the APS Topical Group on Shock Compression of Condensed Matter

NASA Astrophysics Data System (ADS)

Forbes, Jerry W.

2002-07-01

In order to provide broader scientific recognition and to advance the science of shock compressed condensed matter, a group of American Physical Society (APS) members worked within the Society to make this field an active part of the APS. Individual papers were presented at APS meetings starting in the 1940's and shock wave sessions were organized starting with the 1967 Pasadena meeting. Shock wave topical conferences began in 1979 in Pullman, WA. Signatures were obtained on a petition in 1984 from a balanced cross-section of the shock wave community to form an APS Topical Group (TG). The APS Council officially accepted the formation of the Shock Compression of Condensed Matter (SCCM) TG at its October 1984 meeting. This action firmly aligned the shock wave field with a major physical science organization. Most early topical conferences were sanctioned by the APS while those held after 1992 were official APS meetings. The topical group organizes a shock wave topical conference in odd numbered years while participating in shock wave/high pressure sessions at APS general meetings in even numbered years.

Heat Pipe Vapor Dynamics. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Issacci, Farrokh

1990-01-01

The dynamic behavior of the vapor flow in heat pipes is investigated at startup and during operational transients. The vapor is modeled as two-dimensional, compressible viscous flow in an enclosure with inflow and outflow boundary conditions. For steady-state and operating transients, the SIMPLER method is used. In this method a control volume approach is employed on a staggered grid which makes the scheme very stable. It is shown that for relatively low input heat fluxes the compressibility of the vapor flow is low and the SIMPLER scheme is suitable for the study of transient vapor dynamics. When the input heat flux is high or the process under a startup operation starts at very low pressures and temperatures, the vapor is highly compressible and a shock wave is created in the evaporator. It is shown that for a wide range of input heat fluxes, the standard methods, including the SIMPLER scheme, are not suitable. A nonlinear filtering technique, along with the centered difference scheme, are then used for shock capturing as well as for the solution of the cell Reynolds-number problem. For high heat flux, the startup transient phase involves multiple shock reflections in the evaporator region. Each shock reflection causes a significant increase in the local pressure and a large pressure drop along the heat pipe. Furthermore, shock reflections cause flow reversal in the evaporation region and flow circulations in the adiabatic region. The maximum and maximum-averaged pressure drops in different sections of the heat pipe oscillate periodically with time because of multiple shock reflections. The pressure drop converges to a constant value at steady state. However, it is significantly higher than its steady-state value at the initiation of the startup transient. The time for the vapor core to reach steady-state condition depends on the input heat flux, the heat pipe geometry, the working fluid, and the condenser conditions. However, the vapor transient time, for an Na-filled heat pipe is on the order of seconds. Depending on the time constant for the overall system, the vapor transient time may be very short. Therefore, the vapor core may be assumed to be quasi-steady in the transient analysis of a heat pipe operation.

Method and apparatus for determining pressure-induced frequency-shifts in shock-compressed materials

DOEpatents

Moore, David S.; Schmidt, Stephen C.

1985-01-01

A method and an apparatus for conducting coherent anti-Stokes Raman scattering spectroscopy in shock-compressed materials are disclosed. The apparatus includes a sample vessel having an optically transparent wall and an opposing optically reflective wall. Two coherent laser beams, a pump beam and a broadband Stokes beam, are directed through the window and focused on a portion of the sample. In the preferred embodiment, a projectile is fired from a high-pressure gas gun to impact the outside of the reflective wall, generating a planar shock wave which travels through the sample toward the window. The pump and Stokes beams result in the emission from the shock-compressed sample of a coherent anti-Stokes beam, which is emitted toward the approaching reflective wall of the vessel and reflected back through the window. The anti-Stokes beam is folded into a spectrometer for frequency analysis. The results of such analysis are useful for determining chemical and physical phenomena which occur during the shock-compression of the sample.

Ultrafast visualization of crystallization and grain growth in shock-compressed SiO2

PubMed Central

Gleason, A. E.; Bolme, C. A.; Lee, H. J.; Nagler, B.; Galtier, E.; Milathianaki, D.; Hawreliak, J.; Kraus, R. G.; Eggert, J. H.; Fratanduono, D. E.; Collins, G. W.; Sandberg, R.; Yang, W.; Mao, W. L.

2015-01-01

Pressure- and temperature-induced phase transitions have been studied for more than a century but very little is known about the non-equilibrium processes by which the atoms rearrange. Shock compression generates a nearly instantaneous propagating high-pressure/temperature condition while in situ X-ray diffraction (XRD) probes the time-dependent atomic arrangement. Here we present in situ pump–probe XRD measurements on shock-compressed fused silica, revealing an amorphous to crystalline high-pressure stishovite phase transition. Using the size broadening of the diffraction peaks, the growth of nanocrystalline stishovite grains is resolved on the nanosecond timescale just after shock compression. At applied pressures above 18 GPa the nuclueation of stishovite appears to be kinetically limited to 1.4±0.4 ns. The functional form of this grain growth suggests homogeneous nucleation and attachment as the growth mechanism. These are the first observations of crystalline grain growth in the shock front between low- and high-pressure states via XRD. PMID:26337754

Ultrafast visualization of crystallization and grain growth in shock-compressed SiO 2

DOE PAGES

Gleason, A. E.; Bolme, C. A.; Lee, H. J.; ...

2015-09-04

Pressure- and temperature-induced phase transitions have been studied for more than a century but very little is known about the non-equilibrium processes by which the atoms rearrange. Shock compression generates a nearly instantaneous propagating high-pressure/temperature condition while in situ X-ray diffraction (XRD) probes the time-dependent atomic arrangement. Here we present in situ pump–probe XRD measurements on shock-compressed fused silica, revealing an amorphous to crystalline high-pressure stishovite phase transition. Using the size broadening of the diffraction peaks, the growth of nanocrystalline stishovite grains is resolved on the nanosecond timescale just after shock compression. At applied pressures above 18 GPa the nuclueationmore » of stishovite appears to be kinetically limited to 1.4 ± 0.4 ns. The functional form of this grain growth suggests homogeneous nucleation and attachment as the growth mechanism. As a result, these are the first observations of crystalline grain growth in the shock front between low- and high-pressure states via XRD.« less

Method and apparatus for determining pressure-induced frequency-shifts in shock-compressed materials

DOEpatents

Moore, D.S.; Schmidt, S.C.

1983-12-16

A method and an apparatus for conducting coherent anti-Stokes Raman scattering spectroscopy in shock-compressed materials are disclosed. The apparatus includes a sample vessel having an optically transparent wall and an opposing optically reflective wall. Two coherent laser beams, a pump beam and a broadband Stokes beam, are directed through the window and focused on a portion of the sample. In the preferred embodiment, a projectile is fired from a high-pressure gas gun to impact the outside of the reflective wall, generating a planar shock wave which travels through the sample toward the window. The pump and Stokes beams result in the emission from the shock-compressed sample of a coherent anti-Stokes beam, which is emitted toward the approaching reflective wall of the vessel and reflected back through the window. The anti-Stokes beam is folded into a spectrometer for frequency analysis. The results of such analysis are useful for determining chemical and physical phenomena which occur during the shock-compression of the sample.

Ultrafast transformation of graphite to diamond: an ab initio study of graphite under shock compression.

PubMed

Mundy, Christopher J; Curioni, Alessandro; Goldman, Nir; Will Kuo, I-F; Reed, Evan J; Fried, Laurence E; Ianuzzi, Marcella

2008-05-14

We report herein ab initio molecular dynamics simulations of graphite under shock compression in conjunction with the multiscale shock technique. Our simulations reveal that a novel short-lived layered diamond intermediate is formed within a few hundred of femtoseconds upon shock loading at a shock velocity of 12 kms (longitudinal stress>130 GPa), followed by formation of cubic diamond. The layered diamond state differs from the experimentally observed hexagonal diamond intermediate found at lower pressures and previous hydrostatic calculations in that a rapid buckling of the graphitic planes produces a mixture of hexagonal and cubic diamond (layered diamond). Direct calculation of the x-ray absorption spectra in our simulations reveals that the electronic structure of the final state closely resembles that of compressed cubic diamond.

Hugoniot equation of state and dynamic strength of boron carbide

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

Grady, Dennis E.

Boron carbide ceramics have been particularly problematic in attempts to develop adequate constitutive model descriptions for purposes of analysis of dynamic response in the shock and impact environment. Dynamic strength properties of boron carbide ceramic differ uniquely from comparable ceramics. Furthermore, boron carbide is suspected, but not definitely shown, to undergoing polymorphic phase transformation under shock compression. In the present paper, shock-wave compression measurements conducted over the past 40 years are assessed for the purpose of achieving improved understanding of the dynamic equation of state and strength of boron carbide. In particular, attention is focused on the often ignored Losmore » Alamos National Laboratory (LANL) Hugoniot measurements performed on porous sintered boron carbide ceramic. The LANL data are shown to exhibit two compression anomalies on the shock Hugoniot within the range of 20–60 GPa that may relate to crystallographic structure transitions. More recent molecular dynamics simulations on the compressibility of the boron carbide crystal lattice reveal compression transitions that bear similarities to the LANL Hugoniot results. The same Hugoniot data are complemented with dynamic isentropic compression data for boron carbide extracted from Hugoniot measurements on boron carbide and copper granular mixtures. Other Hugoniot measurements, however, performed on near-full-density boron carbide ceramic differ markedly from the LANL Hugoniot data. These later data exhibit markedly less compressibility and tend not to show comparable anomalies in compressibility. Alternative Hugoniot anomalies, however, are exhibited by the near-full-density data. Experimental uncertainty, Hugoniot strength, and phase transformation physics are all possible explanations for the observed discrepancies. It is reasoned that experimental uncertainty and Hugoniot strength are not likely explanations for the observed differences. The notable mechanistic difference in the processes of shock compression between the LANL data and that of the other studies is the markedly larger inelastic deformation and dissipation experienced in the shock event brought about by compaction of the substantially larger porosity LANL test ceramics. High-pressure diamond anvil cell experiments reveal extensive amorphization, reasoned to be a reversion product of a higher-pressure crystallographic phase, which is a consequence of application of both high pressure and shear deformation to the boron carbide crystal structure. A dependence of shock-induced high-pressure phase transformation in boron carbide on the extent of shear deformation experienced in the shock process offers a plausible explanation for the differences observed in the LANL Hugoniot data on porous ceramic and that of other shock data on near-full-density boron carbide.« less

[Current international recommendations for pediatric cardiopulmonary resuscitation: the European guidelines].

PubMed

López-Herce, Jesús; Rodríguez Núñez, Antonio; Maconochie, Ian; Van de Voorde, Patric; Biarent, Dominique; Eich, Christof; Bingham, Robert; Rajka, Thomas; Zideman, David; Carrillo, Ángel; de Lucas, Nieves; Calvo, Custodio; Manrique, Ignacio

2017-07-01

This summary of the European guidelines for pediatric cardiopulmonary resuscitation (CPR) emphasizes the main changes and encourages health care professionals to keep their pediatric CPR knowledge and skills up to date. Basic and advanced pediatric CPR follow the same algorithm in the 2015 guidelines. The main changes affect the prevention of cardiac arrest and the use of fluids. Fluid expansion should not be used routinely in children with fever in the abuse of signs of shock because too high a volume can worsen prognosis. Rescue breaths should last around 1 second in basic CPR, making pediatric recommendations consistent with those for adults. Chest compressions should be at least as deep as one-third the anteroposterior diameter of the thorax. Most children in cardiac arrest lack a shockable rhythm, and in such cases a coordinated sequence of breaths, chest compressions, and administration of adrenalin is essential. An intraosseous canula may be the first choice for introducing fluids and medications, especially in young infants. In treating supraventricular tachycardia with cardioversion, an initial dose of 1 J/kg is currently recommended (vs the dose of 0.5 J/kg previously recommended). After spontaneous circulation is recovered, measures to control fever should be taken. The goal is to reach a normal temperature even before arrival to the hospital.

Microscale investigation of dynamic impact of dry and saturated glass powder

NASA Astrophysics Data System (ADS)

Herbold, Eric; Crum, Ryan; Hurley, Ryan; Lind, Jonathan; Homel, Michael; Akin, Minta

2017-06-01

The response of particulate materials to shock loading involves complex interactions between grains involving fracture/comminution and possible interstitial material. The strength of saturated powders is attributed to ``effective stress'' where the fluid stiffens the material response and reduces the shear strength. However, detailed information regarding the effects of saturation under dynamic loading is lacking since static equilibrium between phases cannot be assumed and the interaction becomes more complex. Recent experiments at the dynamic compression sector (DCS) have captured in-situ images of shock loaded soda lime glass spheres in dry and saturated conditions. The differences between the modes of deformation and compaction are compared with mesoscale simulations to help develop our ideas about the observed response. This work was performed under the auspices of the U.S. Department of Energy (DOE) by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. LDRD tracking code 16-ERD-010. The Dynamic Compression Sector (DCS, sector 35) is supported by DOE/NNSA Award Number DE-NA0002442. The use of Advanced Photon Source is operated by Argonne National Laboratory under Contract No. DE-AC02-06CH11357.

Dynamic compression and volatile release of carbonates

NASA Technical Reports Server (NTRS)

Tyburczy, J. A.; Ahrens, T. J.

1984-01-01

Particle velocity profiles upon shock compression and isentropic releases were measured for polycrystalline calcite. The Solenhofen limestone release paths lie, close to the Hugoniot. Calcite 3 to 2 transition, upon release, was observed, but rarefaction shocks were not detected. The equation of state is used to predict the fraction of material devolatilized upon isentropic release as a function of shock pressure. The effect of ambient partial pressure of CO2 on the calculations is demonstrated and considered in models of atmospheric evolution by impact induced mineral devolatilization. The radiative characteristics of shocked calcite indicate that localization of thermal energy occurs under shock compression. Shock entropy calculations result in a minimum estimate of 90% devolatilization upon complete release from 10 GPa. Isentropic release paths from calculated continuum Hugoniot temperatures cross into the CaO (solid) + CO2 (vapor) field at improbably low pressures. It is found that release paths from measured shock temperatures cross into the melt plus vapor field at pressures greater than .5 GPa, which suggests that devolatilization is initiated at the shear banding sites.

Using phase contrast imaging to measure the properties of shock compressed aerogel

NASA Astrophysics Data System (ADS)

Hawreliak, James; Erskine, Dave; Schropp, Andres; Galtier, Eric C.; Heimann, Phil

2017-01-01

The Hugoniot states of low density materials, such as silica aerogel, are used in high energy density physics research because they can achieve a range of high temperature and pressure states through shock compression. The shock properties of 100mg/cc silica aerogel were studied at the Materials in Extreme Conditions end station using x-ray phase contrast imaging of spherically expanding shock waves. The shockwaves were generated by focusing a high power 532nm laser to a 50μm focal spot on a thin aluminum ablator. The shock speed was measured in separate experiments using line-VISAR measurements from the reflecting shock front. The relative timing between the x-ray probe and the optical laser pump was varied so x-ray PCI images were taken at pressures between 10GPa and 30GPa. Modeling the compression of the foam in the strong shock limit uses a Gruneisen parameter of 0.49 to fit the data rather than a value of 0.66 that would correspond to a plasma state.

Shock Compression Induced Hot Spots in Energetic Material Detected by Thermal Imaging Microscopy

NASA Astrophysics Data System (ADS)

Chen, Ming-Wei; Dlott, Dana

2014-06-01

The chemical reaction of powder energetic material is of great interest in energy and pyrotechnic applications since the high reaction temperature. Under the shock compression, the chemical reaction appears in the sub-microsecond to microsecond time scale, and releases a large amount of energy. Experimental and theoretical research progresses have been made in the past decade, in order to characterize the process under the shock compression. However, the knowledge of energy release and temperature change of this procedure is still limited, due to the difficulties of detecting technologies. We have constructed a thermal imaging microscopy apparatus, and studied the temperature change in energetic materials under the long-wavelength infrared (LWIR) and ultrasound exposure. Additionally, the real-time detection of the localized heating and energy concentration in composite material is capable with our thermal imaging microscopy apparatus. Recently, this apparatus is combined with our laser driven flyer plate system to provide a lab-scale source of shock compression to energetic material. A fast temperature increase of thermite particulars induced by the shock compression is directly observed by thermal imaging with 15-20 μm spatial resolution. Temperature change during the shock loading is evaluated to be at the order of 10^9K/s, through the direct measurement of mid-wavelength infrared (MWIR) emission intensity change. We observe preliminary results to confirm the hot spots appear with shock compression on energetic crystals, and will discuss the data and analysis in further detail. M.-W. Chen, S. You, K. S. Suslick, and D. D. Dlott, {Rev. Sci. Instr., 85, 023705 (2014) M.-W. Chen, S. You, K. S. Suslick, and D. D. Dlott, {Appl. Phys. Lett., 104, 061907 (2014)} K. E. Brown, W. L. Shaw, X. Zheng, and D. D. Dlott, {Rev. Sci. Instr., 83, 103901 (2012)}

A numerical analysis of the British Experimental Rotor Program blade

NASA Technical Reports Server (NTRS)

Duque, Earl P. N.

1989-01-01

Two Computational Fluid Dynamic codes which solve the compressible full-potential and the Reynolds-Averaged Thin-Layer Navier-Stokes equations were used to analyze the nonrotating aerodynamic characteristics of the British Experimental Rotor Program (BERP) helicopter blade at three flow regimes: low angle of attack, high angle of attack and transonic. Excellent agreement was found between the numerical results and experiment. In the low angle of attack regime, the BERP had less induced drag than a comparable aspect ratio rectangular planform wing. At high angle of attack, the blade attained high-lift by maintaining attached flow at the outermost spanwise locations. In the transonic regime, the BERP design reduces the shock strength at the outer spanwise locations which affects wave drag and shock-induced separation. Overall, the BERP blade exhibited many favorable aerodynamic characteristics in comparison to conventional helicopter rotor blades.

Isentropic compressive wave generator impact pillow and method of making same

DOEpatents

Barker, Lynn M.

1985-01-01

An isentropic compressive wave generator and method of making same. The w generator comprises a disk or flat "pillow" member having component materials of different shock impedances formed in a configuration resulting in a smooth shock impedance gradient over the thickness thereof for interpositioning between an impactor member and a target specimen for producing a shock wave of a smooth predictable rise time. The method of making the pillow member comprises the reduction of the component materials to a powder form and forming the pillow member by sedimentation and compressive techniques.

Isentropic compressive wave generator and method of making same

DOEpatents

Barker, L.M.

An isentropic compressive wave generator and method of making same are disclosed. The wave generator comprises a disk or flat pillow member having component materials of different shock impedances formed in a configuration resulting in a smooth shock impedance gradient over the thickness thereof for interpositioning between an impactor member and a target specimen for producing a shock wave of a smooth predictable rise time. The method of making the pillow member comprises the reduction of the component materials to a powder form and forming the pillow member by sedimentation and compressive techniques.

Shock-Wave Pulse Compression and Stretching of Dodecane and Mineral Oils

NASA Astrophysics Data System (ADS)

Bannikova, I. A.; Zubareva, A. N.; Utkin, A. V.

2018-04-01

The behavior of dodecane, vacuum, and transformer oils under shock-wave pulse compression and stretching are studied experimentally. The wave profiles are registered using a VISAR laser interferometer. The shock adiabats, the dependence of the sound velocity on the pressure, and the maximum negative pressures developed in the studied liquids are determined. It is shown that the negative pressure value does not depend on the deformation rate in the case of oils and is a strong function of the compression pulse amplitude in the case of dodecane.

Converging shocks in elastic-plastic solids.

PubMed

Ortega, A López; Lombardini, M; Hill, D J

2011-11-01

We present an approximate description of the behavior of an elastic-plastic material processed by a cylindrically or spherically symmetric converging shock, following Whitham's shock dynamics theory. Originally applied with success to various gas dynamics problems, this theory is presently derived for solid media, in both elastic and plastic regimes. The exact solutions of the shock dynamics equations obtained reproduce well the results obtained by high-resolution numerical simulations. The examined constitutive laws share a compressible neo-Hookean structure for the internal energy e=e(s)(I(1))+e(h)(ρ,ς), where e(s) accounts for shear through the first invariant of the Cauchy-Green tensor, and e(h) represents the hydrostatic contribution as a function of the density ρ and entropy ς. In the strong-shock limit, reached as the shock approaches the axis or origin r=0, we show that compression effects are dominant over shear deformations. For an isothermal constitutive law, i.e., e(h)=e(h)(ρ), with a power-law dependence e(h) is proportional to ρ(α), shock dynamics predicts that for a converging shock located at r=R(t) at time t, the Mach number increases as M is proportional to [log(1/R)](α), independently of the space index s, where s=2 in cylindrical geometry and 3 in spherical geometry. An alternative isothermal constitutive law with p(ρ) of the arctanh type, which enforces a finite density in the strong-shock limit, leads to M is proportional to R(-(s-1)) for strong shocks. A nonisothermal constitutive law, whose hydrostatic part e(h) is that of an ideal gas, is also tested, recovering the strong-shock limit M is proportional to R(-(s-1)/n(γ)) originally derived by Whitham for perfect gases, where γ is inherently related to the maximum compression ratio that the material can reach, (γ+1)/(γ-1). From these strong-shock limits, we also estimate analytically the density, radial velocity, pressure, and sound speed immediately behind the shock. While the hydrostatic part of the energy essentially commands the strong-shock behavior, the shear modulus and yield stress modify the compression ratio and velocity of the shock far from the axis or origin. A characterization of the elastic-plastic transition in converging shocks, which involves an elastic precursor and a plastic compression region, is finally exposed.

Exploration of CdTe quantum dots as mesoscale pressure sensors via time-resolved shock-compression photoluminescent emission spectroscopy

NASA Astrophysics Data System (ADS)

Kang, Zhitao; Banishev, Alexandr A.; Lee, Gyuhyon; Scripka, David A.; Breidenich, Jennifer; Xiao, Pan; Christensen, James; Zhou, Min; Summers, Christopher J.; Dlott, Dana D.; Thadhani, Naresh N.

2016-07-01

The nanometer size of CdTe quantum dots (QDs) and their unique optical properties, including size-tunable narrow photoluminescent emission, broad absorption, fast photoluminescence decay, and negligible light scattering, are ideal features for spectrally tagging the shock response of localized regions in highly heterogeneous materials such as particulate media. In this work, the time-resolved laser-excited photoluminescence response of QDs to shock-compression was investigated to explore their utilization as mesoscale sensors for pressure measurements and in situ diagnostics during shock loading experiments. Laser-driven shock-compression experiments with steady-state shock pressures ranging from 2.0 to 13 GPa were performed on nanocomposite films of CdTe QDs dispersed in a soft polyvinyl alcohol polymer matrix and in a hard inorganic sodium silicate glass matrix. Time-resolved photoluminescent emission spectroscopy was used to correlate photoluminescence changes with the history of shock pressure and the dynamics of the matrix material surrounding the QDs. The results revealed pressure-induced blueshifts in emitted wavelength, decreases in photoluminescent emission intensity, reductions in peak width, and matrix-dependent response times. Data obtained for these QD response characteristics serve as indicators for their use as possible time-resolved diagnostics of the dynamic shock-compression response of matrix materials in which such QDs are embedded as in situ sensors.

Multiple film plane diagnostic for shocked lattice measurements (invited)

NASA Astrophysics Data System (ADS)

Kalantar, Daniel H.; Bringa, E.; Caturla, M.; Colvin, J.; Lorenz, K. T.; Kumar, M.; Stölken, J.; Allen, A. M.; Rosolankova, K.; Wark, J. S.; Meyers, M. A.; Schneider, M.; Boehly, T. R.

2003-03-01

Laser-based shock experiments have been conducted in thin Si and Cu crystals at pressures above the Hugoniot elastic limit. In these experiments, static film and x-ray streak cameras recorded x rays diffracted from lattice planes both parallel and perpendicular to the shock direction. These data showed uniaxial compression of Si(100) along the shock direction and three-dimensional compression of Cu(100). In the case of the Si diffraction, there was a multiple wave structure observed, which may be due to a one-dimensional phase transition or a time variation in the shock pressure. A new film-based detector has been developed for these in situ dynamic diffraction experiments. This large-angle detector consists of three film cassettes that are positioned to record x rays diffracted from a shocked crystal anywhere within a full π steradian. It records x rays that are diffracted from multiple lattice planes both parallel and at oblique angles with respect to the shock direction. It is a time-integrating measurement, but time-resolved data may be recorded using a short duration laser pulse to create the diffraction source x rays. This new instrument has been fielded at the OMEGA and Janus lasers to study single-crystal materials shock compressed by direct laser irradiation. In these experiments, a multiple wave structure was observed on many different lattice planes in Si. These data provide information on the structure under compression.

Exploration of CdTe quantum dots as mesoscale pressure sensors via time-resolved shock-compression photoluminescent emission spectroscopy

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

Kang, Zhitao; School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332-0245; Banishev, Alexandr A.

The nanometer size of CdTe quantum dots (QDs) and their unique optical properties, including size-tunable narrow photoluminescent emission, broad absorption, fast photoluminescence decay, and negligible light scattering, are ideal features for spectrally tagging the shock response of localized regions in highly heterogeneous materials such as particulate media. In this work, the time-resolved laser-excited photoluminescence response of QDs to shock-compression was investigated to explore their utilization as mesoscale sensors for pressure measurements and in situ diagnostics during shock loading experiments. Laser-driven shock-compression experiments with steady-state shock pressures ranging from 2.0 to 13 GPa were performed on nanocomposite films of CdTe QDs dispersedmore » in a soft polyvinyl alcohol polymer matrix and in a hard inorganic sodium silicate glass matrix. Time-resolved photoluminescent emission spectroscopy was used to correlate photoluminescence changes with the history of shock pressure and the dynamics of the matrix material surrounding the QDs. The results revealed pressure-induced blueshifts in emitted wavelength, decreases in photoluminescent emission intensity, reductions in peak width, and matrix-dependent response times. Data obtained for these QD response characteristics serve as indicators for their use as possible time-resolved diagnostics of the dynamic shock-compression response of matrix materials in which such QDs are embedded as in situ sensors.« less

Bacterial survival following shock compression in the GigaPascal range

NASA Astrophysics Data System (ADS)

Hazael, Rachael; Fitzmaurice, Brianna C.; Foglia, Fabrizia; Appleby-Thomas, Gareth J.; McMillan, Paul F.

2017-09-01

The possibility that life can exist within previously unconsidered habitats is causing us to expand our understanding of potential planetary biospheres. Significant populations of living organisms have been identified at depths extending up to several km below the Earth's surface; whereas laboratory experiments have shown that microbial species can survive following exposure to GigaPascal (GPa) pressures. Understanding the degree to which simple organisms such as microbes survive such extreme pressurization under static compression conditions is being actively investigated. The survival of bacteria under dynamic shock compression is also of interest. Such studies are being partly driven to test the hypothesis of potential transport of biological organisms between planetary systems. Shock compression is also of interest for the potential modification and sterilization of foodstuffs and agricultural products. Here we report the survival of Shewanella oneidensis bacteria exposed to dynamic (shock) compression. The samples examined included: (a) a "wild type" (WT) strain and (b) a "pressure adapted" (PA) population obtained by culturing survivors from static compression experiments to 750 MPa. Following exposure to peak shock pressures of 1.5 and 2.5 GPa the proportion of survivors was established as the number of colony forming units (CFU) present after recovery to ambient conditions. The data were compared with previous results in which the same bacterial samples were exposed to static pressurization to the same pressures, for 15 minutes each. The results indicate that shock compression leads to survival of a significantly greater proportion of both WT and PA organisms. The significantly shorter duration of the pressure pulse during the shock experiments (2-3 μs) likely contributes to the increased survival of the microbial species. One reason for this can involve the crossover from deformable to rigid solid-like mechanical relaxational behavior that occurs for bacterial cell walls on the order of seconds in the time-dependent strain rate.

Ultrafast Kα x-ray Thomson scattering from shock compressed lithium hydride

DOE PAGES

Kritcher, A. L.; Neumayer, P.; Castor, J.; ...

2009-04-13

Spectrally and temporally resolved x-ray Thomson scattering using ultrafast Ti Kα x rays has provided experimental validation for modeling of the compression and heating of shocked matter. The coalescence of two shocks launched into a solid density LiH target by a shaped 6 ns heater beam was observed from rapid heating to temperatures of 2.2 eV, enabling tests of shock timing models. Here, the temperature evolution of the target at various times during shock progression was characterized from the intensity of the elastic scattering component. The observation of scattering from plasmons, electron plasma oscillations, at shock coalescence indicates a transitionmore » to a dense metallic plasma state in LiH. From the frequency shift of the measured plasmon feature the electron density was directly determined with high accuracy, providing a material compression of a factor of 3 times solid density. The quality of data achieved in these experiments demonstrates the capability for single shot dynamic characterization of dense shock compressed matter. Here, the conditions probed in this experiment are relevant for the study of the physics of planetary formation and to characterize inertial confinement fusion targets for experiments such as on the National Ignition Facility, Lawrence Livermore National Laboratory.« less

Luminescent Measurement Systems for the Investigation of a Scramjet Inlet-Isolator

PubMed Central

Idris, Azam Che; Saad, Mohd Rashdan; Zare-Behtash, Hossein; Kontis, Konstantinos

2014-01-01

Scramjets have become a main focus of study for many researchers, due to their application as propulsive devices in hypersonic flight. This entails a detailed understanding of the fluid mechanics involved to be able to design and operate these engines with maximum efficiency even at their off-design conditions. It is the objective of the present cold-flow investigation to study and analyse experimentally the mechanics of the fluid structures encountered within a generic scramjet inlet at M = 5. Traditionally, researchers have to rely on stream-thrust analysis, which requires the complex setup of a mass flow meter, a force balance and a heat transducer in order to measure inlet-isolator performance. Alternatively, the pitot rake could be positioned at inlet-isolator exit plane, but this method is intrusive to the flow, and the number of pitot tubes is limited by the model size constraint. Thus, this urgent need for a better flow diagnostics method is addressed in this paper. Pressure-sensitive paint (PSP) has been applied to investigate the flow characteristics on the compression ramp, isolator surface and isolator sidewall. Numerous shock-shock interactions, corner and shoulder separation regions, as well as shock trains were captured by the luminescent system. The performance of the scramjet inlet-isolator has been shown to improve when operated in a modest angle of attack. PMID:24721773

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 XRD, Shock and Static Compression of CaF2

NASA Astrophysics Data System (ADS)

Kalita, Patricia; Specht, Paul; Root, Seth; Sinclair, Nicholas; Schuman, Adam; White, Melanie; Cornelius, Andrew; Smith, Jesse; Sinogeikin, Stanislav

2017-06-01

The high-pressure behavior of CaF2 is probed with x-ray diffraction (XRD) combined with both dynamic compression, using a two-stage light gas gun, and static compression, using diamond anvil cells. We use XRD to follow the unfolding of a shock-driven, fluorite to cotunnite phase transition, on the timescale of nanoseconds. The dynamic behavior of CaF2 under shock loading is contrasted with that under static compression. This work leverages experimental capabilities at the Advanced Photon Source: dynamic XRD and shock experiments at the Dynamic Compression Sector, as well as XRD and static compression in diamond anvil cell at the High-Pressure Collaborative Access Team. These experiments and cross-platform comparisons, open the door to an unprecedented understanding of equations of state and phase transitions at the microstructural level and at different time scales and will ultimately improve our capability to simulate the behavior of materials at extreme conditions. Sandia National Laboratories is a multi-mission laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

Interactive calculation procedures for mixed compression inlets

NASA Technical Reports Server (NTRS)

Reshotko, Eli

1983-01-01

The proper design of engine nacelle installations for supersonic aircraft depends on a sophisticated understanding of the interactions between the boundary layers and the bounding external flows. The successful operation of mixed external-internal compression inlets depends significantly on the ability to closely control the operation of the internal compression portion of the inlet. This portion of the inlet is one where compression is achieved by multiple reflection of oblique shock waves and weak compression waves in a converging internal flow passage. However weak these shocks and waves may seem gas-dynamically, they are of sufficient strength to separate a laminar boundary layer and generally even strong enough for separation or incipient separation of the turbulent boundary layers. An understanding was developed of the viscous-inviscid interactions and of the shock wave boundary layer interactions and reflections.

Numerical predictions of shock propagation through unreactive and reactive liquids with experimental validation

NASA Astrophysics Data System (ADS)

Stekovic, Svjetlana; Nissen, Erin; Bhowmick, Mithun; Stewart, Donald S.; Dlott, Dana D.

2017-06-01

The objective of this work is to numerically analyze shock behavior as it propagates through compressed, unreactive and reactive liquid, such as liquid water and liquid nitromethane. Parameters, such as pressure and density, are analyzed using the Mie-Gruneisen EOS and each multi-material system is modeled using the ALE3D software. The motivation for this study is based on provided high-resolution, optical interferometer (PDV) and optical pyrometer measurements. In the experimental set-up, a liquid is placed between an Al 1100 plate and Pyrex BK-7 glass. A laser-driven Al 1100 flyer impacts the plate, causing the liquid to be highly compressed. The numerical model investigates the influence of the high pressure, shock-compressed behavior in each liquid, the energy transfer, and the wave impedance at the interface of each material in contact. The numerical results using ALE3D will be validated by experimental data. This work aims to provide further understanding of shock-compressed behavior and how the shock influences phase transition in each liquid.

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

DOE PAGES

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

2015-04-16

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

Shock compression experiments on Lithium Deuteride (LiD) single crystals

DOE PAGES

Knudson, M. D.; Desjarlais, M. P.; Lemke, R. W.

2016-12-21

Shock compression experiments in the few hundred GPa (multi-Mabr) regime were performed on Lithium Deuteride (LiD) single crystals. This study utilized the high velocity flyer plate capability of the Sandia Z Machine to perform impact experiments at flyer plate velocities in the range of 17-32 km/s. Measurements included pressure, density, and temperature between ~200-600 GPa along the Principal Hugoniot – the locus of end states achievable through compression by large amplitude shock waves – as well as pressure and density of re - shock states up to ~900 GPa. Lastly, the experimental measurements are compared with recent density functional theorymore » calculations as well as a new tabular equation of state developed at Los Alamos National Labs.« less

Shock Re-equilibration of Fluid Inclusions

NASA Technical Reports Server (NTRS)

Madden, M. E. Elwood; Horz, F.; Bodnar, R. J.

2004-01-01

Fluid inclusions (microscopic volumes of fluid trapped within minerals as they precipitate) are extremely common in terrestrial minerals formed under a wide range of geological conditions from surface evaporite deposits to kimberlite pipes. While fluid inclusions in terrestrial rocks are nearly ubiquitous, only a few fluid inclusion-bearing meteorites have been documented. The scarcity of fluid inclusions in meteoritic materials may be a result of (a) the absence of fluids when the mineral was formed on the meteorite parent body or (b) the destruction of fluid inclusions originally contained in meteoritic materials by subsequent shock metamorphism. However, the effects of impact events on pre-existing fluid inclusions trapped in target and projectile rocks has received little study. Fluid inclusions trapped prior to the shock event may be altered (re-equilibrated) or destroyed due to the high pressures, temperatures, and strain rates associated with impact events. By examining the effects of shock deformation on fluid inclusion properties and textures we may be able to better constrain the pressure-temperature path experienced by terrestrial and meteoritic shocked materials and also gain a clearer understanding of why fluid inclusions are rarely found in meteorite samples.

The Shock Compression Laboratory at Harvard: A New Facility for Planetary Impact Processes

NASA Technical Reports Server (NTRS)

Stewart, S. T.

2004-01-01

The Shock Compression Laboratory in the Department of Earth and Planetary Sciences at Harvard is a new facility for the study of impact and collisional phenomena. The following describes the experimental capabilities of the laboratory.

Observations of subsonic and supersonic shear flows in laser driven high-energy-density plasmas

NASA Astrophysics Data System (ADS)

Harding, E. C.

2009-11-01

Shear layers containing strong velocity gradients appear in many high-energy-density (HED) systems and play important roles in mixing and the transition to turbulence. Yet few laboratory experiments have been carried out to study their detailed evolution in this extreme environment where plasmas are compressible, actively ionizing, often involve strong shock waves and have complex material properties. Many shear flows produce the Kelvin-Helmholtz (KH) instability, which initiates the mixing at a fluid interface. We present results from two dedicated shear flow experiments that produced overall subsonic and supersonic flows using novel target designs. In the subsonic case, the Omega laser was used to drive a blast wave along a rippled interface between plastic and foam, shocking both the materials to produce two fluids separated by a sharp shear layer. The interface subsequently rolled-upped into large KH vortices that were accompanied by bubble-like structures of unknown origin. This was the first time the evolution of a well-resolved KH instability was observed in a HED plasma in the laboratory. We have analyzed the properties and dynamics of the plasma based on the data and fundamental models, without resorting to simulated values. In the second, supersonic experiment the Nike laser was used to drive a supersonic flow of Al plasma along a rippled, low-density foam surface. Here again the flowing plasma drove a shock into the second material, so that two fluids were separated by a shear layer. In contrast to the subsonic case, the flow developed shocks around the ripples in response to the supersonic flow of Al. Collaborators: R.P. Drake, O.A. Hurricane, J.F. Hansen, Y. Aglitskiy, T. Plewa, B.A. Remington, H.F. Robey, J.L. Weaver, A.L. Velikovich, R.S. Gillespie, M.J. Bono, M.J. Grosskopf, C.C. Kuranz, A. Visco.

First-principles calculation of the reflectance of shock-compressed xenon

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

Norman, G. E.; Saitov, I. M., E-mail: saitovilnur@gmail.com; Stegailov, V. V.

2015-05-15

Within electron density functional theory (DFT), the reflectance of radiation from shock-compressed xenon plasma is calculated. The dependence of the reflectance on the frequency of the incident radiation and on the plasma density is considered. The Fresnel formula is used. The expression for the longitudinal dielectric tensor in the long-wavelength limit is used to calculate the imaginary part of the dielectric function (DF). The real part of the DF is determined by the Kramers-Kronig transformation. The results are compared with experimental data. An approach is proposed to estimate the plasma frequency in shock-compressed xenon.

Cartilage elasticity resides in shape module decoran and aggrecan sumps of damping fluid: implications in osteoarthrosis

PubMed Central

Scott, John E; Stockwell, Robin A

2006-01-01

Cartilage ultrastructure is based on collagen fibrils tied together by proteoglycans (PGs). Interfibrillar orthogonal PG bridges (‘shape modules’) were located by electron histochemistry using Cupromeronic blue methodology. Their frequency and size, similar to those in tendon, cornea, etc., were compatible with biochemical estimates of tissue decoran (formerly decorin), the PG component of shape module bridges. Digestion by hyaluronanase and chondroitinase AC helped to identify aggrecan and decoran and exemplified the destruction of shape modular organization by glycan-splitting agents. The anionic glycosaminoglycan (AGAG) of decoran, dermochondan sulphate (DS, formerly dermatan sulphate), contains l-iduronate, an elastic sugar unit. Chondroitan, keratan (present in aggrecan) and hyaluronan are not similarly elastic but can participate in sliding-filament reversible deformability. Mechanical properties predicted for the interfibrillar bridges accord with anisotropic stress/strain responses of articular cartilage to compressive or tensile stresses. We propose that fluid from pericellular aggrecan-rich domains moves under pressure into the interterritorial fibrillar arrays against the elastic resistance of the shape modules, which return the fluid, post-compression, to its original position. Cartilage is tendon-like, with the addition of expansile aggrecan-rich reservoirs of aqueous shock absorber fluid. Rupture or loss of interfibrillar ties would allow expansile PG to force the collagenous matrix apart, imbibing water, increasing swelling and fissuring – characteristic manifestations of osteoarthrosis (OA), a joint disease of major economic importance. Decoran may be a primary target of the OA disease process. PMID:16581860

Equation of state for shock compression of distended solids

NASA Astrophysics Data System (ADS)

Grady, Dennis; Fenton, Gregg; Vogler, Tracy

2014-05-01

Shock Hugoniot data for full-density and porous compounds of boron carbide, silicon dioxide, tantalum pentoxide, uranium dioxide and playa alluvium are investigated for the purpose of equation-of-state representation of intense shock compression. Complications of multivalued Hugoniot behavior characteristic of highly distended solids are addressed through the application of enthalpy-based equations of state of the form originally proposed by Rice and Walsh in the late 1950's. Additive measures of cold and thermal pressure intrinsic to the Mie-Gruneisen EOS framework is replaced by isobaric additive functions of the cold and thermal specific volume components in the enthalpy-based formulation. Additionally, experimental evidence reveals enhancement of shock-induced phase transformation on the Hugoniot with increasing levels of initial distension for silicon dioxide, uranium dioxide and possibly boron carbide. Methods for addressing this experimentally observed feature of the shock compression are incorporated into the EOS model.

Equation of State for Shock Compression of High Distension Solids

NASA Astrophysics Data System (ADS)

Grady, Dennis

2013-06-01

Shock Hugoniot data for full-density and porous compounds of boron carbide, silicon dioxide, tantalum pentoxide, uranium dioxide and playa alluvium are investigated for the purpose of equation-of-state representation of intense shock compression. Complications of multivalued Hugoniot behavior characteristic of highly distended solids are addressed through the application of enthalpy-based equations of state of the form originally proposed by Rice and Walsh in the late 1950's. Additivity of cold and thermal pressure intrinsic to the Mie-Gruneisen EOS framework is replaced by isobaric additive functions of the cold and thermal specific volume components in the enthalpy-based formulation. Additionally, experimental evidence supports acceleration of shock-induced phase transformation on the Hugoniot with increasing levels of initial distention for silicon dioxide, uranium dioxide and possibly boron carbide. Methods for addressing this experimentally observed facet of the shock compression are introduced into the EOS model.

Complete equation of state for shocked liquid nitrogen: Analytical developments

DOE PAGES

Winey, J. M.; Gupta, Y. M.

2016-08-02

The thermodynamic response of liquid nitrogen has been studied extensively, in part, due to the long-standing interest in the high pressure and high temperature dissociation of shocked molecular nitrogen. Previous equation of state (EOS) developments regarding shocked liquid nitrogen have focused mainly on the use of intermolecular pair potentials in atomistic calculations. Here, we present EOS developments for liquid nitrogen, incorporating analytical models, for use in continuum calculations of the shock compression response. The analytical models, together with available Hugoniot data, were used to extrapolate a low pressure reference EOS for molecular nitrogen [Span, et al., J. Phys. Chem. Ref.more » Data 29, 1361 (2000)] to high pressures and high temperatures. Using the EOS presented here, the calculated pressures and temperatures for single shock, double shock, and multiple shock compression of liquid nitrogen provide a good match to the measured results over a broad range of P-T space. Our calculations provide the first comparison of EOS developments with recently-measured P-T states under multiple shock compression. The present EOS developments are general and are expected to be useful for other liquids that have low pressure reference EOS information available.« less

Equalizing resolution in smoothed-particle hydrodynamics calculations using self-adaptive sinc kernels

NASA Astrophysics Data System (ADS)

García-Senz, Domingo; Cabezón, Rubén M.; Escartín, José A.; Ebinger, Kevin

2014-10-01

Context. The smoothed-particle hydrodynamics (SPH) technique is a numerical method for solving gas-dynamical problems. It has been applied to simulate the evolution of a wide variety of astrophysical systems. The method has a second-order accuracy, with a resolution that is usually much higher in the compressed regions than in the diluted zones of the fluid. Aims: We propose and check a method to balance and equalize the resolution of SPH between high- and low-density regions. This method relies on the versatility of a family of interpolators called sinc kernels, which allows increasing the interpolation quality by varying only a single parameter (the exponent of the sinc function). Methods: The proposed method was checked and validated through a number of numerical tests, from standard one-dimensional Riemann problems in shock tubes, to multidimensional simulations of explosions, hydrodynamic instabilities, and the collapse of a Sun-like polytrope. Results: The analysis of the hydrodynamical simulations suggests that the scheme devised to equalize the accuracy improves the treatment of the post-shock regions and, in general, of the rarefacted zones of fluids while causing no harm to the growth of hydrodynamic instabilities. The method is robust and easy to implement with a low computational overload. It conserves mass, energy, and momentum and reduces to the standard SPH scheme in regions of the fluid that have smooth density gradients.

Modelling cavitation erosion using fluid–material interaction simulations

PubMed Central

Chahine, Georges L.; Hsiao, Chao-Tsung

2015-01-01

Material deformation and pitting from cavitation bubble collapse is investigated using fluid and material dynamics and their interaction. In the fluid, a novel hybrid approach, which links a boundary element method and a compressible finite difference method, is used to capture non-spherical bubble dynamics and resulting liquid pressures efficiently and accurately. The bubble dynamics is intimately coupled with a finite-element structure model to enable fluid/structure interaction simulations. Bubble collapse loads the material with high impulsive pressures, which result from shock waves and bubble re-entrant jet direct impact on the material surface. The shock wave loading can be from the re-entrant jet impact on the opposite side of the bubble, the fast primary collapse of the bubble, and/or the collapse of the remaining bubble ring. This produces high stress waves, which propagate inside the material, cause deformation, and eventually failure. A permanent deformation or pit is formed when the local equivalent stresses exceed the material yield stress. The pressure loading depends on bubble dynamics parameters such as the size of the bubble at its maximum volume, the bubble standoff distance from the material wall and the pressure driving the bubble collapse. The effects of standoff and material type on the pressure loading and resulting pit formation are highlighted and the effects of bubble interaction on pressure loading and material deformation are preliminarily discussed. PMID:26442140

Analysis of Shock Compression of Strong Single Crystals With Logarithmic Thermoelastic-Plastic Theory

DTIC Science & Technology

2014-05-01

Royal Society of London Series A, 465, 307–334. Clayton, J. (2010a). Modeling nonlinear electromechanical behavior of shocked silicon carbide . Journal...and fourth-order longitudinal elastic constants by shock compression techniques–application to sapphire and fused quartz. Journal of the Acoustical...Vogler, T., & Clayton, J. (2008). Heterogeneous deformation and spall of an extruded tungsten alloy: Plate impact experiments and crystal plasticity

On the fundamental unsteady fluid dynamics of shock-induced flows through ducts

NASA Astrophysics Data System (ADS)

Mendoza, Nicole Renee

Unsteady shock wave propagation through ducts has many applications, ranging from blast wave shelter design to advanced high-speed propulsion systems. The research objective of this study was improved fundamental understanding of the transient flow structures during unsteady shock wave propagation through rectangular ducts with varying cross-sectional area. This research focused on the fluid dynamics of the unsteady shock-induced flow fields, with an emphasis placed on understanding and characterizing the mechanisms behind flow compression (wave structures), flow induction (via shock waves), and enhanced mixing (via shock-induced viscous shear layers). A theoretical and numerical (CFD) parametric study was performed, in which the effects of these parameters on the unsteady flow fields were examined: incident shock strength, area ratio, and viscous mode (inviscid, laminar, and turbulent). Two geometries were considered: the backward-facing step (BFS) geometry, which provided a benchmark and conceptual framework, and the splitter plate (SP) geometry, which was a canonical representation of the engine flow path. The theoretical analysis was inviscid, quasi-1 D and quasi-steady; and the computational analysis was fully 2D, time-accurate, and VISCOUS. The theory provided the wave patterns and primary wave strengths for the BFS geometry, and the simulations verified the wave pattems and quantified the effects of geometry and viscosity. It was shown that the theoretical wave patterns on the BFS geometry can be used to systematically analyze the transient, 20, viscous flows on the SP geometry. This work also highlighted the importance and the role of oscillating shock and expansion waves in the development of these unsteady flows. The potential for both upstream and downstream flow induction was addressed. Positive upstream flow induction was not found in this study due to the persistent formation of an upstream-moving shock wave. Enhanced mixing was addressed by examining the evolution of the unsteady shear layer, its instability, and their effects on the flow field. The instability always appeared after the reflected shock interaction, and was exacerbated in the laminar cases and damped out in the turbulent cases. This research provided new understanding of the long-term evolution of these confined flows. Lastly, the turbulent work is one of the few turbulent studies on these flows.

Frequency shift measurement in shock-compressed materials

DOEpatents

Moore, David S.; Schmidt, Stephen C.

1985-01-01

A method for determining molecular vibrational frequencies in shock-compressed transparent materials. A single laser beam pulse is directed into a sample material while the material is shock-compressed from a direction opposite that of the incident laser beam. A Stokes beam produced by stimulated Raman scattering is emitted back along the path of the incident laser beam, that is, in the opposite direction to that of the incident laser beam. The Stokes beam is separated from the incident beam and its frequency measured. The difference in frequency between the Stokes beam and the incident beam is representative of the characteristic frequency of the Raman active mode of the sample. Both the incident beam and the Stokes beam pass perpendicularly through the shock front advancing through the sample, thereby minimizing adverse effects of refraction.

Dynamic Material Properties of Orthotropic Polymer and Molybdenum for Use in Next Generation Composite Armor Concept?

DTIC Science & Technology

2011-06-01

1. Shock Compression Experimental Techniques ...............................22 a. Target...3 Figure 2. Composite plate (left) shown by Poh defeating Tantalum projectile while armor grade steel (right) failed...entire target buildup used for a shock compression experiment ..................................................................................23 Figure

Structural changes in shock compressed silicon observed using time-resolved x-ray diffraction at the Dynamic Compression Sector

NASA Astrophysics Data System (ADS)

Turneaure, Stefan; Zdanowicz, E.; Sinclair, N.; Graber, T.; Gupta, Y. M.

2015-06-01

Structural changes in shock compressed silicon were observed directly using time-resolved x-ray diffraction (XRD) measurements at the Dynamic Compression Sector at the Advanced Photon Source. The silicon samples were impacted by polycarbonate impactors accelerated to velocities greater than 5 km/s using a two-stage light gas gun resulting in impact stresses of about 25 GPa. The 23.5 keV synchrotron x-ray beam passed through the polycarbonate impactor, the silicon sample, and an x-ray window (polycarbonate or LiF) at an angle of 30 degrees relative to the impact plane. Four XRD frames (~ 100 ps snapshots) were obtained with 153.4 ns between frames near the time of impact. The XRD measurements indicate that in the peak shocked state, the silicon samples completely transformed to a high-pressure phase. XRD results for both shocked polycrystalline silicon and single crystal silicon will be presented and compared. Work supported by DOE/NNSA.

Initial decay of flow properties of planar, cylindrical and spherical blast waves

NASA Astrophysics Data System (ADS)

Sadek, H. S. I.; Gottlieb, J. J.

1983-10-01

Analytical expressions are presented for the initial decay of all major flow properties just behind planar, cylindrical, and spherical shock wave fronts whose trajectories are known as a function of either distance versus time or shock overpressure versus distance. These expressions give the time and/or distance derivatives of the flow properties not only along constant time and distance lines but also along positive and negative characteristic lines and a fluid-particle path. Conventional continuity, momentum and energy equations for the nonstationary motion of an inviscid, non-heat conducting, compressible gas are used in their derivation, along with the equation of state of a perfect gas. All analytical expressions are validated by comparing the results to those obtained indirectly from known self-similar solutions for planar, cylindrical and spherical shock-wave flows generated both by a sudden energy release and by a moving piston. Futhermore, time derivatives of pressure and flow velocity are compared to experimental data from trinitrotoluene (TNT), pentolite, ammonium nitrate-fuel oil (ANFO) and propane-oxygen explosions, and good agreement is obtained.

Compression Shocks in Two-Dimensional Gas Flows

NASA Technical Reports Server (NTRS)

Busemann, A.

1949-01-01

The following are arguments on the compression shocks in gas flow start with a simplified representation of the results of the study made by Th. Meyer as published in the Forschungsheft 62 of the VDI, supplemented by several amplifications for the application.In the treatment of compression shocks, the equation of energy, the equation of continuity, the momentum equation, the equation of state of the particular gas, as well as the condition Of the second law of thermodynamics that no decrease of entropy is possible in an isolated system, must be taken into consideration. The result is that, in those cases where the sudden change of state according to the second law of thermodynamics is possible, there always occurs a compression of the gas which is uniquely determined by the other conditions.

(BARS) -- Bibliographic Retrieval System Sandia Shock Compression (SSC) database Shock Physics Index (SPHINX) database. Volume 1: UNIX version query guide customized application for INGRES

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

Herrmann, W.; von Laven, G.M.; Parker, T.

1993-09-01

The Bibliographic Retrieval System (BARS) is a data base management system specially designed to retrieve bibliographic references. Two databases are available, (i) the Sandia Shock Compression (SSC) database which contains over 5700 references to the literature related to stress waves in solids and their applications, and (ii) the Shock Physics Index (SPHINX) which includes over 8000 further references to stress waves in solids, material properties at intermediate and low rates, ballistic and hypervelocity impact, and explosive or shock fabrication methods. There is some overlap in the information in the two data bases.

Ultrafast shock compression of self-assembled monolayers: a molecular picture.

PubMed

Patterson, James E; Dlott, Dana D

2005-03-24

Simulations of self-assembled monolayers (SAMs) are performed to interpret experimental measurements of ultrafast approximately 1 GPa (volume compression deltaV approximately 0.1) planar shock compression dynamics probed by vibrational sum-frequency generation (SFG) spectroscopy (Lagutchev, A. S.; Patterson, J. E.; Huang, W.; Dlott, D. D. J. Phys. Chem. B 2005, 109, XXXX). The SAMs investigated are octadecanethiol (ODT) and pentadecanethiol (PDT) on Au(111) and Ag(111) substrates, and benzyl mercaptan (BMT) on Au(111). In the alkane SAMs, SFG is sensitive to the instantaneous orientation of the terminal methyl; in BMT it is sensitive to the phenyl orientation. Computed structures of alkane SAMs are in good agreement with experiment. In alkanes, the energies of gauche defects increase with increasing number and depth below the methyl plane, with the exception of ODT/Au where both single and double gauche defects at the two uppermost dihedrals have similar energies. Simulations of isothermal uniaxial compression of SAM lattices show that chain and methyl tilting is predominant in PDT/Au, ODT/Ag and PDT/Ag, whereas single and double gauche defect formation is predominant in ODT/Au. Time-resolved shock data showing transient SFG signal loss of ODT/Au and PDT/Au are fit by calculations of the terminal group orientations as a function of deltaV and their contributions to the SFG hyperpolarizability. The highly elastic response of PDT/Au results from shock-generated methyl and chain tilting. The viscoelastic response of ODT/Au results from shock generation of single and double gauche defects. Isothermal compression simulations help explain and fit the time dependence of shock spectra but generally underestimate the magnitude of SFG signal loss because they do not include effects of high-strain-rate dynamics and shock front and surface irregularities.

Unified solver for fluid dynamics and aeroacoustics in isentropic gas flows

NASA Astrophysics Data System (ADS)

Pont, Arnau; Codina, Ramon; Baiges, Joan; Guasch, Oriol

2018-06-01

The high computational cost of solving numerically the fully compressible Navier-Stokes equations, together with the poor performance of most numerical formulations for compressible flow in the low Mach number regime, has led to the necessity for more affordable numerical models for Computational Aeroacoustics. For low Mach number subsonic flows with neither shocks nor thermal coupling, both flow dynamics and wave propagation can be considered isentropic. Therefore, a joint isentropic formulation for flow and aeroacoustics can be devised which avoids the need for segregating flow and acoustic scales. Under these assumptions density and pressure fluctuations are directly proportional, and a two field velocity-pressure compressible formulation can be derived as an extension of an incompressible solver. Moreover, the linear system of equations which arises from the proposed isentropic formulation is better conditioned than the homologous incompressible one due to the presence of a pressure time derivative. Similarly to other compressible formulations the prescription of boundary conditions will have to deal with the backscattering of acoustic waves. In this sense, a separated imposition of boundary conditions for flow and acoustic scales which allows the evacuation of waves through Dirichlet boundaries without using any tailored damping model will be presented.

The effect of shear strength on isentropic compression experiments

NASA Astrophysics Data System (ADS)

Thomson, Stuart; Howell, Peter; Ockendon, John; Ockendon, Hilary

2015-06-01

Isentropic compression experiments (ICE) are a novel way of obtaining equation of state information for metals undergoing violent plastic deformation. In a typical experiment, millimetre thick metal samples are subjected to pressures on the order of 10 -102 GPa, while the yield strength of the material can be as low as 10-1GPa. The analysis of such experiments has so far neglected the effect of shear strength, instead treating the highly plasticised metal as an inviscid compressible fluid. However making this approximation belies the basic elastic nature of a solid object. A more accurate method should strive to incorporate the small but measurable effects of shear strength. Here we present a one-dimensional mathematical model for elastoplasticity at high stress which allows for both compressibility and the shear strength of the material. In the limit of zero yield stress this model reproduces the hydrodynamic models currently used to analyse ICEs. We will also show using a systematic asymptotic analysis that entropy changes are universally negligible in the absence of shocks. Numerical solutions of the governing equations will then be presented for problems relevant to ICEs in order to investigate the effects of shear strength over a model based purely on hydrodynamics.

Terminal shock position and restart control of a Mach 2.7, two-dimensional, twin duct mixed compression inlet

NASA Technical Reports Server (NTRS)

Cole, G. L.; Neiner, G. H.; Baumbick, R. J.

1973-01-01

Experimental results of terminal shock and restart control system tests of a two-dimensional, twin-duct mixed compression inlet are presented. High-response (110-Hz bandwidth) overboard bypass doors were used, both as the variable to control shock position and as the means of disturbing the inlet airflow. An inherent instability in inlet shock position resulted in noisy feedback signals and thus restricted the terminal shock position control performance that was achieved. Proportional-plus-integral type controllers using either throat exit static pressure or shock position sensor feedback gave adequate low-frequency control. The inlet restart control system kept the terminal shock control loop closed throughout the unstart-restart transient. The capability to restart the inlet was non limited by the inlet instability.

[Fluid management and cause of death during shock period in patients with severe burns or burns complicated by inhalation injury].

PubMed

Zhang, Ming-liang; Li, Chi; Ma, Chun-xu

2003-11-01

To explore fluid management and cause of death during shock period in severe burns or burns with inhalation injury. One hundred and twelve patients with severe burns or burn complicated by inhalation injury admitted to our hospital from 1991 to 2000 were analyzed. The fluid management and death conditions during shock period were discussed. The fluid volume for resuscitation could be described as follows: the total fluid volume was 2.2 ml/(%TBSA.kg) including colloid fluid 0.5 ml/(%TBSA.kg), crystalloid fluid 1 ml/(%TBSA.kg)and water 0.7 ml/(%TBSA.kg) during first 24 hours. The total fluid volume was 1.8 ml/(%TBSA.kg) including colloid fluid 0.4 ml/(%TBSA.kg), crystalloid fluid 0.7 ml/(%TBSA.kg) and water 0.7 ml/(%TBSA.kg) during second 24 hours. There were no difference in fluid management between burns and burns with inhalation injury. Seven patients died due to respiratory failure during shock period. Many fluid formula can provide guidance for resuscitation and it is very important that early fluid therapy should accord with concrete clinical conditions of patients in order to pass smoothly through shock period. Early fluid management is not different between burns and burns with inhalation injury.

Strain Gage Measurements of Aft Nacelle Shock Absorbers.

DTIC Science & Technology

ENGINE NACELLES, SHOCK ABSORBERS ), (* SHOCK ABSORBERS , STRESSES), SURFACE TO SURFACE MISSILES, LAUNCHING, STRAIN GAGES, COMPRESSIVE PROPERTIES, CALIBRATION, STRAIN(MECHANICS), FAILURE, GROUND SUPPORT EQUIPMENT.

Highs and lows of 30 years research of fluid physics in microgravity, a personal memory

NASA Astrophysics Data System (ADS)

Straub, Johannes

2006-09-01

On October 4th 1957 the western world was shocked from the news that a Russian satellite, called Sputnik, had been launched and revolves the earth within 90 minutes periodically. This was the starting signal for the race to monde and stars; the "Star War" began. Just at that time I started with the investigation of the static and dynamic behavior of fluids at and near their critical point [1]. With an optical method I measured density stratifications caused by the diverging compressibility of critical fluids in the earth gravity field. There, the real critical state is compressed by its own weight to a layer of the order of the correlation length. I was myself aware that in a satellite a weightlessness environment exists. Thus a dream waked up within me; if it would be possible to perform critical point experiments in such a satellite our knowledge and understanding of its physics must be much improved, and questions violently discussed at that moment should find an answer. But I would never had thoughts that such a dream could be realized within my lifetime. However, in 1975 the German ministry for development and research instructed the DLR to inquiry scientists if weightlessness can support their research. Based on my experience I proposed two research programs: • Study of critical phenomenon, and

Proceedings of Workshop on Laser Diagnostics in Fluid Mechanics and Combustion

NASA Astrophysics Data System (ADS)

1993-10-01

Proceedings of the Workshop on Laser Diagnostics in Fluid Mechanics and Combustion are presented. Topics included are: Accuracy of Laser Doppler Anemometry; Applications of Raman-Rayleigh-LIF Diagnostics in Combustion Research; Phase Doppler Anemometer Technique Concepts and Applications; CARS; Particle Image Velocimetry; Practical Consideration in the Use and Design of Laser Velocimetry Systems in Turbomachinery Applications; Phase Doppler Measurements of Gas-Particle Flow Through a Tube Bank; Degenerate Four Wave Mixing for Shock Tunnel Studies of Supersonic Combustion; Laser Induced Photodissociation and Fluorescence (LIPF) of Sodium Species Present in Coal Combustion; 3D Holographic Measurements Inside a Spark Ignition Engine; Laser Doppler Velocimeter Measurements in Compressible Flow; Bursting in a Tornado Vortex; Quantitative Imaging of OH and Temperature Using a Single Laser Source and Single Intensified Camera; and Laser Doppler Measurements Inside an Artificial Heart Valve.

The application of CFD to the modelling of fires in complex geometries

NASA Astrophysics Data System (ADS)

Burns, A. D.; Clarke, D. S.; Guilbert, P.; Jones, I. P.; Simcox, S.; Wilkes, N. S.

The application of Computational Fluid Dynamics (CFD) to industrial safety is a challenging activity. In particular it involves the interaction of several different physical processes, including turbulence, combustion, radiation, buoyancy, compressible flow and shock waves in complex three-dimensional geometries. In addition, there may be multi-phase effects arising, for example, from sprinkler systems for extinguishing fires. The FLOW3D software (1-3) from Computational Fluid Dynamics Services (CFDS) is in widespread use in industrial safety problems, both within AEA Technology, and also by CFDS's commercial customers, for example references (4-13). This paper discusses some other applications of FLOW3D to safety problems. These applications illustrate the coupling of the gas flows with radiation models and combustion models, particularly for complex geometries where simpler radiation models are not applicable.

Proton spectra diagnostics for shock-compression studies

NASA Astrophysics Data System (ADS)

Welch, D. R.; Harris, D. B.; Bennish, A. H.; Miley, G. H.

1984-12-01

The energy spectra of fusion products escaping long-pulse-length laser-imploded deuterium-tritium filled glass microballoons have been measured with a time-of-flight spectrometer. The D(d,p)T reaction proton energy spectra showed two distinct peaks, indicating two burn phases in the target. The first burn phase is attributed to a spherically converging shock, while the second is attributed to subsequent compression heating. The analysis of these spectra provides the first conclusive proof of significant compression yields in these targets, where approximately half of the yield occurs during the compression burn phase.

Methods of Investigation of Equations that Describe Waves in Tubes with Elastic Walls and Application of the Theory of Reversible and Weak Dissipative Shocks

NASA Astrophysics Data System (ADS)

Bakholdin, Igor

2018-02-01

Various models of a tube with elastic walls are investigated: with controlled pressure, filled with incompressible fluid, filled with compressible gas. The non-linear theory of hyperelasticity is applied. The walls of a tube are described with complete membrane model. It is proposed to use linear model of plate in order to take the bending resistance of walls into account. The walls of the tube were treated previously as inviscid and incompressible. Compressibility of material of walls and viscosity of material, either gas or liquid are considered. Equations are solved numerically. Three-layer time and space centered reversible numerical scheme and similar two-layer space reversible numerical scheme with approximation of time derivatives by Runge-Kutta method are used. A method of correction of numerical schemes by inclusion of terms with highorder derivatives is developed. Simplified hyperbolic equations are derived.

Experience in using a numerical scheme with artificial viscosity at solving the Riemann problem for a multi-fluid model of multiphase flow

NASA Astrophysics Data System (ADS)

Bulovich, S. V.; Smirnov, E. M.

2018-05-01

The paper covers application of the artificial viscosity technique to numerical simulation of unsteady one-dimensional multiphase compressible flows on the base of the multi-fluid approach. The system of the governing equations is written under assumption of the pressure equilibrium between the "fluids" (phases). No interfacial exchange is taken into account. A model for evaluation of the artificial viscosity coefficient that (i) assumes identity of this coefficient for all interpenetrating phases and (ii) uses the multiphase-mixture Wood equation for evaluation of a scale speed of sound has been suggested. Performance of the artificial viscosity technique has been evaluated via numerical solution of a model problem of pressure discontinuity breakdown in a three-fluid medium. It has been shown that a relatively simple numerical scheme, explicit and first-order, combined with the suggested artificial viscosity model, predicts a physically correct behavior of the moving shock and expansion waves, and a subsequent refinement of the computational grid results in a monotonic approaching to an asymptotic time-dependent solution, without non-physical oscillations.

Pressure wave propagation in fluid-filled co-axial elastic tubes. Part 1: Basic theory.

PubMed

Berkouk, K; Carpenter, P W; Lucey, A D

2003-12-01

Our work is motivated by ideas about the pathogenesis of syringomyelia. This is a serious disease characterized by the appearance of longitudinal cavities within the spinal cord. Its causes are unknown, but pressure propagation is probably implicated. We have developed an inviscid theory for the propagation of pressure waves in co-axial, fluid-filled, elastic tubes. This is intended as a simple model of the intraspinal cerebrospinal-fluid system. Our approach is based on the classic theory for the propagation of longitudinal waves in single, fluid-filled, elastic tubes. We show that for small-amplitude waves the governing equations reduce to the classic wave equation. The wave speed is found to be a strong function of the ratio of the tubes' cross-sectional areas. It is found that the leading edge of a transmural pressure pulse tends to generate compressive waves with converging wave fronts. Consequently, the leading edge of the pressure pulse steepens to form a shock-like elastic jump. A weakly nonlinear theory is developed for such an elastic jump.

Notes on Earth Atmospheric Entry for Mars Sample Return Missions

NASA Technical Reports Server (NTRS)

Rivell, Thomas

2006-01-01

The entry of sample return vehicles (SRVs) into the Earth's atmosphere is the subject of this document. The Earth entry environment for vehicles, or capsules, returning from the planet Mars is discussed along with the subjects of dynamics, aerodynamics, and heat transfer. The material presented is intended for engineers and scientists who do not have strong backgrounds in aerodynamics, aerothermodynamics and flight mechanics. The document is not intended to be comprehensive and some important topics are omitted. The topics considered in this document include basic principles of physics (fluid mechanics, dynamics and heat transfer), chemistry and engineering mechanics. These subjects include: a) fluid mechanics (aerodynamics, aerothermodynamics, compressible fluids, shock waves, boundary layers, and flow regimes from subsonic to hypervelocity; b) the Earth s atmosphere and gravity; c) thermal protection system design considerations; d) heat and mass transfer (convection, radiation, and ablation); e) flight mechanics (basic rigid body dynamics and stability); and f) flight- and ground-test requirements; and g) trajectory and flow simulation methods.

Numerical simulation of exploding pusher targets

NASA Astrophysics Data System (ADS)

Atzeni, S.; Rosenberg, M. J.; Gatu Johnson, M.; Petrasso, R. D.

2017-10-01

Exploding pusher targets, i.e. gas-filled large aspect-ratio glass or plastic shells, driven by a strong laser-generated shock, are widely used as pulsed sources of neutrons and fast charged particles. Recent experiments on exploding pushers provided evidence for the transition from a purely fluid behavior to a kinetic one. Indeed, fluid models largely overpredict yield and temperature as the Knudsen number Kn (ratio of ion mean-free path to compressed gas radius) is comparable or larger than one. At Kn = 0.3 - 1, fluid codes reasonably estimate integral quantities as yield and neutron-averaged temperatures, but do not reproduce burn radii, burn profiles and DD/DHe3 yield ratio. This motivated a detailed simulation study of intermediate-Kn exploding pushers. We will show how simulation results depend on models for laser-interaction, electron conductivity (flux-limited local vs nonlocal), viscosity (physical vs artificial), and ion mixing. Work partially supported by Sapienza Project C26A15YTMA, Sapienza 2016 (n. 257584), and Eurofusion Project AWP17-ENR-IFE-CEA-01.

Metallization of aluminum hydride AlH3 at high multiple-shock pressures

NASA Astrophysics Data System (ADS)

Molodets, A. M.; Shakhray, D. V.; Khrapak, A. G.; Fortov, V. E.

2009-05-01

A study of electrophysical and thermodynamic properties of alane AlH3 under multishock compression has been carried out. The increase in specific electroconductivity of alane at shock compression up to pressure 100 GPa has been measured. High pressures and temperatures were obtained with an explosive device, which accelerates the stainless impactor up to 3 km/s. A strong shock wave is generated on impact with a holder containing alane. The impact shock is split into a shock wave reverberating in alane between two stiff metal anvils. This compression loads the alane sample by a multishock manner up to pressure 80-90 GPa, heats alane to the temperature of about 1500-2000 K, and lasts 1μs . The conductivity of shocked alane increases in the range up to 60-75 GPa and is about 30(Ωcm)-1 . In this region the semiconductor regime is true for shocked alane. The conductivity of alane achieves approximately 500(Ωcm)-1 at 80-90 GPa. In this region, conductivity is interpreted in frames of the conception of the “dielectric catastrophe,” taking into consideration significant differences between the electronic states of isolated molecule AlH3 and condensed alane.

Finite Strain Analysis of Shock Compression of Brittle Solids Applied to Titanium Diboride

DTIC Science & Technology

2014-07-01

dislocation motion [18,19] may take place at high pressures. Multiple investigations have discovered that tita - nium diboride demonstrates a rather unique...mean stress under shock compression. It has been suggested [5] that pore collapse may be an important source of inelasticity in tita - nium diboride

Supernova dynamics in the laboratory: Radiative shocks produced by ultra-high pressure implosion experiments on the National Ignition Facility

NASA Astrophysics Data System (ADS)

Pak, Arthur

2012-10-01

Thermonuclear fuel experiments on the National Ignition Facility implode 2-mm diameter capsules with a cryogenic deuterium-tritium ice layer to 1000x liquid density and pressures exceeding 100 Gbar (10^11 atm). About 200 ps after peak compression, a spherical supernova-like radiative shock wave is observed that expands with shock velocities of uS = 300 km/s, temperatures of order 1 keV at densities of 1 g/cc resulting in a radiation strength parameter of Q ˜uS^5 = 10^4. Radiation-hydrodynamic simulations indicate that the shock launched at stagnation first goes down a strong density gradient while propagating outward from the highly compressed DT fuel (˜ 1000g/cc) to the ablation front (˜ 1 g/cc). Similar to what happens inside a star, the shock pressure drops as it accelerates and heats. The radiative shock emission is first observed when it breaks out of the dense compressed fuel shell into the low-density inflowing plasma at the ablation front mimicking the supernova situation where the shock breaks out through the star surface into surrounding in-falling matter [1,2]; the shock is subsequently approaching the supercritical state with a strong pre-cursor followed by rapid cooling. These observations are consistent with the rapid vanishing of the radiation ring 400 ps after peak compression due to strong radiation losses and spherical expansion. The evolution and brightness of the radiative shock provides insight into the performance of these implosions that have the goal to produce burning fusion plasmas in the laboratory. By modifying the capsule ablator composition and thickness, the stagnation pressure, density gradients, shock velocity and radiative properties could be tailored to study various regimes related to supernovae radiative remnants.[4pt] [1] W. David Arnett, Supernovae as phenomena of high-energy astrophysics, Ann NY Aca. Science 302, 90 (1977).[0pt] [2] L. Ensman and A. Burrows, Shock breakout in SN1987A, ApJ 393, 742.

Strength properties and structure of a submicrocrystalline Al-Mg-Mn alloy under shock compression

NASA Astrophysics Data System (ADS)

Petrova, A. N.; Brodova, I. G.; Razorenov, S. V.

2017-06-01

The results of studying the strength of a submicrocrystalline aluminum A5083 alloy (chemical composition was 4.4Mg-0.6Mn-0.11Si-0.23Fe-0.03Cr-0.02Cu-0.06Ti wt % and Al base) under shockwave compression are presented. The submicrocrystalline structure of the alloy was produced in the process of dynamic channel-angular pressing at a strain rate of 104 s-1. The average size of crystallites in the alloy was 180-460 nm. Hugoniot elastic limit σHEL, dynamic yield stress σy, and the spall strength σSP of the submicrocrystalline alloy were determined based on the free-surface velocity profiles of samples during shock compression. It has been established that upon shock compression, the σHEL and σy of the submicrocrystalline alloy are higher than those of the coarse-grained alloy and σsp does not depend on the grain size. The maximum value of σHEL reached for the submicrocrystalline alloy is 0.66 GPa, which is greater than that in the coarse-crystalline alloy by 78%. The dynamic yield stress is σy = 0.31 GPa, which is higher than that of the coarse-crystalline alloy by 63%. The spall strength is σsp = 1.49 GPa. The evolution of the submicrocrystalline structure of the alloy during shock compression was studied. It has been established that a mixed nonequilibrium grain-subgrain structure with a fragment size of about 400 nm is retained after shock compression, and the dislocation density and the hardness of the alloy are increased.

One-dimensional high-order compact method for solving Euler's equations

NASA Astrophysics Data System (ADS)

Mohamad, M. A. H.; Basri, S.; Basuno, B.

2012-06-01

In the field of computational fluid dynamics, many numerical algorithms have been developed to simulate inviscid, compressible flows problems. Among those most famous and relevant are based on flux vector splitting and Godunov-type schemes. Previously, this system was developed through computational studies by Mawlood [1]. However the new test cases for compressible flows, the shock tube problems namely the receding flow and shock waves were not investigated before by Mawlood [1]. Thus, the objective of this study is to develop a high-order compact (HOC) finite difference solver for onedimensional Euler equation. Before developing the solver, a detailed investigation was conducted to assess the performance of the basic third-order compact central discretization schemes. Spatial discretization of the Euler equation is based on flux-vector splitting. From this observation, discretization of the convective flux terms of the Euler equation is based on a hybrid flux-vector splitting, known as the advection upstream splitting method (AUSM) scheme which combines the accuracy of flux-difference splitting and the robustness of flux-vector splitting. The AUSM scheme is based on the third-order compact scheme to the approximate finite difference equation was completely analyzed consequently. In one-dimensional problem for the first order schemes, an explicit method is adopted by using time integration method. In addition to that, development and modification of source code for the one-dimensional flow is validated with four test cases namely, unsteady shock tube, quasi-one-dimensional supersonic-subsonic nozzle flow, receding flow and shock waves in shock tubes. From these results, it was also carried out to ensure that the definition of Riemann problem can be identified. Further analysis had also been done in comparing the characteristic of AUSM scheme against experimental results, obtained from previous works and also comparative analysis with computational results generated by van Leer, KFVS and AUSMPW schemes. Furthermore, there is a remarkable improvement with the extension of the AUSM scheme from first-order to third-order accuracy in terms of shocks, contact discontinuities and rarefaction waves.

Numerical solutions of Navier-Stokes equations for compressible turbulent two/three dimensional flows in terminal shock region of an inlet/diffuser

NASA Technical Reports Server (NTRS)

Liu, N. S.; Shamroth, S. J.; Mcdonald, H.

1983-01-01

The multidimensional ensemble averaged compressible time dependent Navier Stokes equations in conjunction with mixing length turbulence model and shock capturing technique were used to study the terminal shock type of flows in various flight regimes occurring in a diffuser/inlet model. The numerical scheme for solving the governing equations is based on a linearized block implicit approach and the following high Reynolds number calculations were carried out: (1) 2 D, steady, subsonic; (2) 2 D, steady, transonic with normal shock; (3) 2 D, steady, supersonic with terminal shock; (4) 2 D, transient process of shock development and (5) 3 D, steady, transonic with normal shock. The numerical results obtained for the 2 D and 3 D transonic shocked flows were compared with corresponding experimental data; the calculated wall static pressure distributions agree well with the measured data.

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.

Shock compression of [001] single crystal silicon

DOE PAGES

Zhao, S.; Remington, B.; Hahn, E. N.; ...

2016-03-14

Silicon is ubiquitous in our advanced technological society, yet our current understanding of change to its mechanical response at extreme pressures and strain-rates is far from complete. This is due to its brittleness, making recovery experiments difficult. High-power, short-duration, laser-driven, shock compression and recovery experiments on [001] silicon (using impedance-matched momentum traps) unveiled remarkable structural changes observed by transmission electron microscopy. As laser energy increases, corresponding to an increase in peak shock pressure, the following plastic responses are are observed: surface cleavage along {111} planes, dislocations and stacking faults; bands of amorphized material initially forming on crystallographic orientations consistent withmore » dislocation slip; and coarse regions of amorphized material. Molecular dynamics simulations approach equivalent length and time scales to laser experiments and reveal the evolution of shock-induced partial dislocations and their crucial role in the preliminary stages of amorphization. Furthermore, application of coupled hydrostatic and shear stresses produce amorphization below the hydrostatically determined critical melting pressure under dynamic shock compression.« less

Shock compression of [001] single crystal silicon

NASA Astrophysics Data System (ADS)

Zhao, S.; Hahn, E. N.; Kad, B.; Remington, B. A.; Bringa, E. M.; Meyers, M. A.

2016-05-01

Silicon is ubiquitous in our advanced technological society, yet our current understanding of change to its mechanical response at extreme pressures and strain-rates is far from complete. This is due to its brittleness, making recovery experiments difficult. High-power, short-duration, laser-driven, shock compression and recovery experiments on [001] silicon (using impedance-matched momentum traps) unveiled remarkable structural changes observed by transmission electron microscopy. As laser energy increases, corresponding to an increase in peak shock pressure, the following plastic responses are are observed: surface cleavage along {111} planes, dislocations and stacking faults; bands of amorphized material initially forming on crystallographic orientations consistent with dislocation slip; and coarse regions of amorphized material. Molecular dynamics simulations approach equivalent length and time scales to laser experiments and reveal the evolution of shock-induced partial dislocations and their crucial role in the preliminary stages of amorphization. Application of coupled hydrostatic and shear stresses produce amorphization below the hydrostatically determined critical melting pressure under dynamic shock compression.

Transformation of shock-compressed graphite to hexagonal diamond in nanoseconds

PubMed Central

Turneaure, Stefan J.; Sharma, Surinder M.; Volz, Travis J.; Winey, J. M.; Gupta, Yogendra M.

2017-01-01

The graphite-to-diamond transformation under shock compression has been of broad scientific interest since 1961. The formation of hexagonal diamond (HD) is of particular interest because it is expected to be harder than cubic diamond and due to its use in terrestrial sciences as a marker at meteorite impact sites. However, the formation of diamond having a fully hexagonal structure continues to be questioned and remains unresolved. Using real-time (nanosecond), in situ x-ray diffraction measurements, we show unequivocally that highly oriented pyrolytic graphite, shock-compressed along the c axis to 50 GPa, transforms to highly oriented elastically strained HD with the (100)HD plane parallel to the graphite basal plane. These findings contradict recent molecular dynamics simulation results for the shock-induced graphite-to-diamond transformation and provide a benchmark for future theoretical simulations. Additionally, our results show that an earlier report of HD forming only above 170 GPa for shocked pyrolytic graphite may lead to incorrect interpretations of meteorite impact events. PMID:29098183

Transformation of shock-compressed graphite to hexagonal diamond in nanoseconds

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

Turneaure, Stefan J.; Sharma, Surinder M.; Volz, Travis J.

The graphite-to-diamond transformation under shock compression has been of broad scientific interest since 1961. The formation of hexagonal diamond (HD) is of particular interest because it is expected to be harder than cubic diamond and due to its use in terrestrial sciences as a marker at meteorite impact sites. However, the formation of diamond having a fully hexagonal structure continues to be questioned and remains unresolved. Using real-time (nanosecond), in situ x-ray diffraction measurements, we show unequivocally that highly oriented pyrolytic graphite, shock-compressed along the c axis to 50 GPa, transforms to highly oriented elastically strained HD with the (100)HDmore » plane parallel to the graphite basal plane. These findings contradict recent molecular dynamics simulation results for the shock-induced graphite-to-diamond transformation and provide a benchmark for future theoretical simulations. Additionally, our results show that an earlier report of HD forming only above 170 GPa for shocked pyrolytic graphite may lead to incorrect interpretations of meteorite impact events.« less

Transformation of shock-compressed graphite to hexagonal diamond in nanoseconds

DOE PAGES

Turneaure, Stefan J.; Sharma, Surinder M.; Volz, Travis J.; ...

2017-10-27

The graphite-to-diamond transformation under shock compression has been of broad scientific interest since 1961. The formation of hexagonal diamond (HD) is of particular interest because it is expected to be harder than cubic diamond and due to its use in terrestrial sciences as a marker at meteorite impact sites. However, the formation of diamond having a fully hexagonal structure continues to be questioned and remains unresolved. Using real-time (nanosecond), in situ x-ray diffraction measurements, we show unequivocally that highly oriented pyrolytic graphite, shock-compressed along the c axis to 50 GPa, transforms to highly oriented elastically strained HD with the (100)HDmore » plane parallel to the graphite basal plane. These findings contradict recent molecular dynamics simulation results for the shock-induced graphite-to-diamond transformation and provide a benchmark for future theoretical simulations. Additionally, our results show that an earlier report of HD forming only above 170 GPa for shocked pyrolytic graphite may lead to incorrect interpretations of meteorite impact events.« less

Ultrafast X-Ray Diffraction Studies of the Phase Transitions and Equation of State of Scandium Shock Compressed to 82 GPa

DOE PAGES

Briggs, R.; Gorman, M. G.; Coleman, A. L.; ...

2017-01-09

Using x-ray diffraction at the Linac Coherent Light Source x-ray free-electron laser, we have determined simultaneously and self-consistently the phase transitions and equation of state (EOS) of the lightest transition metal, scandium, under shock compression. On compression scandium undergoes a structural phase transition between 32 and 35 GPa to the same bcc structure seen at high temperatures at ambient pressures, and then a further transition at 46 GPa to the incommensurate host-guest polymorph found above 21 GPa in static compression at room temperature. Furthermore, shock melting of the host-guest phase is observed between 53 and 72 GPa with the disappearancemore » of Bragg scattering and the growth of a broad asymmetric diffraction peak from the high-density liquid.« less

Ultrafast X-Ray Diffraction Studies of the Phase Transitions and Equation of State of Scandium Shock Compressed to 82 GPa.

PubMed

Briggs, R; Gorman, M G; Coleman, A L; McWilliams, R S; McBride, E E; McGonegle, D; Wark, J S; Peacock, L; Rothman, S; Macleod, S G; Bolme, C A; Gleason, A E; Collins, G W; Eggert, J H; Fratanduono, D E; Smith, R F; Galtier, E; Granados, E; Lee, H J; Nagler, B; Nam, I; Xing, Z; McMahon, M I

2017-01-13

Using x-ray diffraction at the Linac Coherent Light Source x-ray free-electron laser, we have determined simultaneously and self-consistently the phase transitions and equation of state (EOS) of the lightest transition metal, scandium, under shock compression. On compression scandium undergoes a structural phase transition between 32 and 35 GPa to the same bcc structure seen at high temperatures at ambient pressures, and then a further transition at 46 GPa to the incommensurate host-guest polymorph found above 21 GPa in static compression at room temperature. Shock melting of the host-guest phase is observed between 53 and 72 GPa with the disappearance of Bragg scattering and the growth of a broad asymmetric diffraction peak from the high-density liquid.

Exact Theory of Compressible Fluid Turbulence

NASA Astrophysics Data System (ADS)

Drivas, Theodore; Eyink, Gregory

2017-11-01

We obtain exact results for compressible turbulence with any equation of state, using coarse-graining/filtering. We find two mechanisms of turbulent kinetic energy dissipation: scale-local energy cascade and ``pressure-work defect'', or pressure-work at viscous scales exceeding that in the inertial-range. Planar shocks in an ideal gas dissipate all kinetic energy by pressure-work defect, but the effect is omitted by standard LES modeling of pressure-dilatation. We also obtain a novel inverse cascade of thermodynamic entropy, injected by microscopic entropy production, cascaded upscale, and removed by large-scale cooling. This nonlinear process is missed by the Kovasznay linear mode decomposition, treating entropy as a passive scalar. For small Mach number we recover the incompressible ``negentropy cascade'' predicted by Obukhov. We derive exact Kolmogorov 4/5th-type laws for energy and entropy cascades, constraining scaling exponents of velocity, density, and internal energy to sub-Kolmogorov values. Although precise exponents and detailed physics are Mach-dependent, our exact results hold at all Mach numbers. Flow realizations at infinite Reynolds are ``dissipative weak solutions'' of compressible Euler equations, similarly as Onsager proposed for incompressible turbulence.

A shock-capturing SPH scheme based on adaptive kernel estimation

NASA Astrophysics Data System (ADS)

Sigalotti, Leonardo Di G.; López, Hender; Donoso, Arnaldo; Sira, Eloy; Klapp, Jaime

2006-02-01

Here we report a method that converts standard smoothed particle hydrodynamics (SPH) into a working shock-capturing scheme without relying on solutions to the Riemann problem. Unlike existing adaptive SPH simulations, the present scheme is based on an adaptive kernel estimation of the density, which combines intrinsic features of both the kernel and nearest neighbor approaches in a way that the amount of smoothing required in low-density regions is effectively controlled. Symmetrized SPH representations of the gas dynamic equations along with the usual kernel summation for the density are used to guarantee variational consistency. Implementation of the adaptive kernel estimation involves a very simple procedure and allows for a unique scheme that handles strong shocks and rarefactions the same way. Since it represents a general improvement of the integral interpolation on scattered data, it is also applicable to other fluid-dynamic models. When the method is applied to supersonic compressible flows with sharp discontinuities, as in the classical one-dimensional shock-tube problem and its variants, the accuracy of the results is comparable, and in most cases superior, to that obtained from high quality Godunov-type methods and SPH formulations based on Riemann solutions. The extension of the method to two- and three-space dimensions is straightforward. In particular, for the two-dimensional cylindrical Noh's shock implosion and Sedov point explosion problems the present scheme produces much better results than those obtained with conventional SPH codes.

Control of shock-wave boundary-layer interactions by bleed in supersonic mixed compression inlets

NASA Technical Reports Server (NTRS)

Fukuda, M. K.; Reshotko, E.; Hingst, W. R.

1975-01-01

An experimental investigation has been conducted to determine the effect of bleed region geometry and bleed rate on shock wave-boundary layer interactions in an axisymmetric, mixed-compression inlet at a Mach number of 2.5. The full realizable reduction in transformed form factor is obtained by bleeding off about half the incident boundary layer mass flow. Bleeding upstream or downstream of the shock-induced pressure rise is preferable to bleeding across the shock-induced pressure rise. Slanted holes are more effective than normal holes. Two different bleed hole sizes were tested without detectable difference in performance.

Nitro stretch probing of a single molecular layer to monitor shock compression with picosecond time resolution

NASA Astrophysics Data System (ADS)

Berg, Christopher; Lagutchev, Alexei; Fu, Yuanxi; Dlott, Dana

2012-03-01

Ultrafast shock compression vibrational spectroscopy experiments with molecular monolayers provide atomic-scale time and space resolution, which enables critical testing of reactive molecular simulations. Since the origination of this project, we have greatly improved the ability to detect shocked monolayers by nonlinear coherent vibrational spectroscopy with nonresonant suppression. In this study, we show new results on a nitroaromatic monolayer, where the nitro symmetric stretch is probed. A small frequency blue-shift under shock conditions compared to measurements with static high pressure shows the shock is ~1 GPa. The ability to flash-preheat the monolayer by several hundred K is demonstrated. In order to observe shock monolayer chemistry in real time, along with pre-heating, the shock pressure needs to be increased and methods to do so are described.

Radiative shocks produced from spherical cryogenic implosions at the National Ignition Facility

DOE PAGES

Pak, A.; Divol, L.; Gregori, G.; ...

2013-05-20

Spherically expanding radiative shock waves have been observed from inertially confined implosion experiments at the National Ignition Facility. In these experiments, a spherical fusion target, initially 2 mm in diameter, is compressed via the pressure induced from the ablation of the outer target surface. At the peak compression of the capsule, x-ray and nuclear diagnostics indicate the formation of a central core, with a radius and ion temperature of ~20 μm and ~ 2 keV, respectively. This central core is surrounded by a cooler compressed shell of deuterium-tritium fuel that has an outer radius of ~40 μm and a densitymore » of >500 g/cm 3. Using inputs from multiple diagnostics, the peak pressure of the compressed core has been inferred to be of order 100 Gbar for the implosions discussed here. Furthermore, the shock front, initially located at the interface between the high pressure compressed fuel shell and surrounding in-falling low pressure ablator plasma, begins to propagate outwards after peak compression has been reached.« less

High-Speed Photography of Detonation Propagation in Dynamically Precompressed Liquid Explosives

NASA Astrophysics Data System (ADS)

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

2007-12-01

The propagation of detonation in shock-compressed nitromethane was observed with a high-speed framing camera. The test explosive, nitromethane, was compressed by a reverberating shock wave to pressures as high as 10 GPa prior to being detonated by a secondary detonation event. The pressure and density in the test explosive prior to detonation were determined using two methods: manganin stress gauge measurements and LS-DYNA simulations. The velocity of the detonation front was determined from consecutive frames and correlated to the density of the reverberating shock-compressed explosive prior to detonation. Observing detonation propagation under these non-ambient conditions provides data which can be useful in the validation of equation of state models.

User Guide for Compressible Flow Toolbox Version 2.1 for Use With MATLAB(Registered Trademark); Version 7

NASA Technical Reports Server (NTRS)

Melcher, Kevin J.

2006-01-01

This report provides a user guide for the Compressible Flow Toolbox, a collection of algorithms that solve almost 300 linear and nonlinear classical compressible flow relations. The algorithms, implemented in the popular MATLAB programming language, are useful for analysis of one-dimensional steady flow with constant entropy, friction, heat transfer, or shock discontinuities. The solutions do not include any gas dissociative effects. The toolbox also contains functions for comparing and validating the equation-solving algorithms against solutions previously published in the open literature. The classical equations solved by the Compressible Flow Toolbox are: isentropic-flow equations, Fanno flow equations (pertaining to flow of an ideal gas in a pipe with friction), Rayleigh flow equations (pertaining to frictionless flow of an ideal gas, with heat transfer, in a pipe of constant cross section.), normal-shock equations, oblique-shock equations, and Prandtl-Meyer expansion equations. At the time this report was published, the Compressible Flow Toolbox was available without cost from the NASA Software Repository.

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.

X-ray Thomson scattering measurements of temperature and density from multi-shocked CH capsules

DOE PAGES

Fletcher, L. B.; Glenzer, S. H.; Kritcher, A.; ...

2013-05-24

Proof-of-principle measurements of the electron densities, temperatures, and ionization states of spherically compressed multi-shocked CH (polystyrene) capsules have been achieved using spectrally resolved x-ray Thomson scattering. A total energy of 13.5 kJ incident on target is used to compress a 70 μm thick CH shell above solid-mass density using three coalescing shocks. Separately, a laser-produced zinc He-α x-ray source at 9 keV delayed 200 ps-800 ps after maximum compression is used to probe the plasma in the non-collective scattering regime. The data show that x-ray Thomson scattering enables a complete description of the time-dependent hydrodynamic evolution of shock-compressed CH capsules,more » with a maximum measured density of ρ > 6 g cm –3. Additionally, the results demonstrate that accurate measurements of x-ray scattering from bound-free transitions in the CH plasma demonstrate strong evidence that continuum lowering is the primary ionization mechanism of carbon L-shell electrons.« less

Compression in Working Memory and Its Relationship With Fluid Intelligence.

PubMed

Chekaf, Mustapha; Gauvrit, Nicolas; Guida, Alessandro; Mathy, Fabien

2018-06-01

Working memory has been shown to be strongly related to fluid intelligence; however, our goal is to shed further light on the process of information compression in working memory as a determining factor of fluid intelligence. Our main hypothesis was that compression in working memory is an excellent indicator for studying the relationship between working-memory capacity and fluid intelligence because both depend on the optimization of storage capacity. Compressibility of memoranda was estimated using an algorithmic complexity metric. The results showed that compressibility can be used to predict working-memory performance and that fluid intelligence is well predicted by the ability to compress information. We conclude that the ability to compress information in working memory is the reason why both manipulation and retention of information are linked to intelligence. This result offers a new concept of intelligence based on the idea that compression and intelligence are equivalent problems. Copyright © 2018 Cognitive Science Society, Inc.

Invariant Functional Forms for K(r,P) Type Equations of State for Hydrodynamically Driven Flow

NASA Astrophysics Data System (ADS)

Hrbek, George

2001-06-01

At the 11th American Physical Society Topical Group Meeting on Shock Compression of Condensed Matter, Group Theoretic Methods, as defined by Lie were applied to the problem of temperature independent, hydrodynamic shock in a Birch-Murnaghan continuum. (1) Group parameter ratios were linked to the physical quantities (i.e., KT, K'T, and K''T) specified for the various order Birch-Murnaghan approximations. This technique has now been generalized to provide a mathematical formalism applicable to a wide class of forms (i.e., K(r,P)) for the equation of state. Variations in material expansion and resistance (i.e., counter pressure) are shown to be functions of compression and material variation ahead of the expanding front. Illustrative examples include the Birch-Murnaghan, Vinet, Brennan-Stacey, Shanker, Tait, Poirier, and Jones-Wilkins-Lee (JWL) forms. The results of this study will allow the various equations of state, and their respective fitting coefficients, to be compared with experiments. To do this, one must introduce the group ratios into a numerical simulation for the flow and generate the density, pressure, and particle velocity profiles as the shock moves through the material. (2) (1) Hrbek, G. M., Invariant Functional Forms For The Second, Third, And Fourth Order Birch-Murnaghan Equation of State For Materials Subject to Hydrodynamic Shock, Proceedings of the 11th American Physical Society Topical Group Meeting on Shock Compression of Condensed Matter (SCCM Shock 99), Snowbird, Utah (2) Hrbek, G. M., Physical Interpretation of Mathematically Invariant K(r,P) Type Equations Of State For Hydrodynamically Driven Flows, Submitted to the 12th American Physical Society Topical Group Meeting on Shock Compression of Condensed Matter (SCCM Shock 01), Atlanta, Georgia

Implementation of Hydrodynamic Simulation Code in Shock Experiment Design for Alkali Metals

NASA Astrophysics Data System (ADS)

Coleman, A. L.; Briggs, R.; Gorman, M. G.; Ali, S.; Lazicki, A.; Swift, D. C.; Stubley, P. G.; McBride, E. E.; Collins, G.; Wark, J. S.; McMahon, M. I.

2017-10-01

Shock compression techniques enable the investigation of extreme P-T states. In order to probe off-Hugoniot regions of P-T space, target makeup and laser pulse parameters must be carefully designed. HYADES is a hydrodynamic simulation code which has been successfully utilised to simulate shock compression events and refine the experimental parameters required in order to explore new P-T states in alkali metals. Here we describe simulations and experiments on potassium, along with the techniques required to access off-Hugoniot states.

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

NASA Astrophysics Data System (ADS)

Mikaelian, Karnig O.

2016-07-01

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

Supersonic compressor

DOEpatents

Lawlor, Shawn P [Bellevue, WA; Novaresi, Mark A [San Diego, CA; Cornelius, Charles C [Kirkland, WA

2008-02-26

A gas compressor based on the use of a driven rotor having an axially oriented compression ramp traveling at a local supersonic inlet velocity (based on the combination of inlet gas velocity and tangential speed of the ramp) which forms a supersonic shockwave axially, between adjacent strakes. In using this method to compress inlet gas, the supersonic compressor efficiently achieves high compression ratios while utilizing a compact, stabilized gasdynamic flow path. Operated at supersonic speeds, the inlet stabilizes an oblique/normal shock system in the gasdyanamic flow path formed between the gas compression ramp on a strake, the shock capture lip on the adjacent strake, and captures the resultant pressure within the stationary external housing while providing a diffuser downstream of the compression ramp.

The Compressibility Burble

NASA Technical Reports Server (NTRS)

Stack, John

1935-01-01

Simultaneous air-flow photographs and pressure-distribution measurements have been made of the NACA 4412 airfoil at high speeds in order to determine the physical nature of the compressibility burble. The flow photographs were obtained by the Schlieren method and the pressures were simultaneously measured for 54 stations on the 5-inch-chord wing by means of a multiple-tube photographic manometer. Pressure-measurement results and typical Schlieren photographs are presented. The general nature of the phenomenon called the "compressibility burble" is shown by these experiments. The source of the increased drag is the compression shock that occurs, the excess drag being due to the conversion of a considerable amount of the air-stream kinetic energy into heat at the compression shock.

High-energy synchrotron X-ray radiography of shock-compressed materials

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 presentation will discuss the development and application of a high-energy (50 to 250 keV) synchrotron X-ray imaging method to study shock-compressed, high-Z samples at Beamline I12 at the Diamond Light Source synchrotron (Rutherford-Appleton Laboratory, UK). Shock waves are driven into materials using a portable, single-stage gas gun designed by the Institute of Shock Physics. Following plate impact, material deformation is probed in-situ by white-beam X-ray radiography and complimentary velocimetry diagnostics. The high energies, large beam size (13 x 13 mm), and appreciable sample volumes (~ 1 cm3) viable for study at Beamline I12 compliment existing in-house pulsed X-ray capabilities and studies at the Dynamic Compression Sector. The authors gratefully acknowledge the ongoing support of Imperial College London, EPSRC, STFC and the Diamond Light Source, and AWE Plc.

A magnetic particle time-of-flight (MagPTOF) diagnostic for measurements of shock- and compression-bang time at the NIF (invited).

PubMed

Rinderknecht, H G; Sio, H; Frenje, J A; Magoon, J; Agliata, A; Shoup, M; Ayers, S; Bailey, C G; Gatu Johnson, M; Zylstra, A B; Sinenian, N; Rosenberg, M J; Li, C K; Sèguin, F H; Petrasso, R D; Rygg, J R; Kimbrough, J R; Mackinnon, A; Bell, P; Bionta, R; Clancy, T; Zacharias, R; House, A; Döppner, T; Park, H S; LePape, S; Landen, O; Meezan, N; Robey, H; Glebov, V U; Hohenberger, M; Stoeckl, C; Sangster, T C; Li, C; Parat, J; Olson, R; Kline, J; Kilkenny, J

2014-11-01

A magnetic particle time-of-flight (MagPTOF) diagnostic has been designed to measure shock- and compression-bang time using D(3)He-fusion protons and DD-fusion neutrons, respectively, at the National Ignition Facility (NIF). This capability, in combination with shock-burn weighted areal density measurements, will significantly constrain the modeling of the implosion dynamics. This design is an upgrade to the existing particle time-of-flight (pTOF) diagnostic, which records bang times using DD or DT neutrons with an accuracy better than ±70 ps [H. G. Rinderknecht et al., Rev. Sci. Instrum. 83, 10D902 (2012)]. The inclusion of a deflecting magnet will increase D(3)He-proton signal-to-background by a factor of 1000, allowing for the first time simultaneous measurements of shock- and compression-bang times in D(3)He-filled surrogate implosions at the NIF.

Effect of fluid compressibility on journal bearing performance

NASA Technical Reports Server (NTRS)

Dimofte, Florin

1993-01-01

An analysis was undertaken to determine the effect of fluid film compressibility on the performance of fluid film bearings. A new version of the Reynolds equation was developed, using a polytropic expansion, for both steady-state and dynamic conditions. Polytropic exponents from 1 (isothermal) to 1000 (approaching an incompressible liquid) were evaluated for two bearing numbers, selected from a range of practical interest for cryogenic application, and without cavitation. Bearing loads were insensitive to fluid compressibility for low bearing numbers, as was expected. The effect of compressibility on attitude angle was significant, even when the bearing number was low. A small amount of fluid compressibility was enough to obtain stable running conditions. Incompressible liquid lacked stability at all conditions. Fluid compressibility can be used to control the bearing dynamic coefficients, thereby influencing the dynamic behavior of the rotor-bearing system.

The Impact Induced Demagnetization Mechanism in NdFeB Permanent Magnets

NASA Astrophysics Data System (ADS)

Li, Yan-Feng; Zhu, Ming-Gang; Li, Wei; Zhou, Dong; Lu, Feng; Chen, Lang; Wu, Jun-Ying; Qi, Yan; Du, An

2013-09-01

Compression of unmagnetized Nd2Fe14B permanent magnets is executed by using shock waves with different pressures in a one-stage light gas gun system. The microstructure, crystal structure, and magnetic properties of the magnets are examined with scanning electronic microscopy, x-ray diffraction, hysteresis loop instruments, and a vibrating sample magnetometer, respectively. The NdFeB magnets display a demagnetization phenomenon after shock wave compression. The coercivity dropped from about 21.4 kOe to 3.2 kOe. The critical pressure of irreversible demagnetization of NdFeB magnets should be less than 4.92 GPa. The coercivity of the NdFeB magnets compressed by shock waves could be recovered after annealing at 900°C and 520°C for 2 h, sequentially. The chaotic orientation of Nd2Fe14B grains in the compressed magnets is the source of demagnetization.

In situ observation of stishovite formation in shock-compressed fused silica

NASA Astrophysics Data System (ADS)

Tracy, Sally June; Turneaure, Stefan; Duffy, Thomas

2017-06-01

Silica, SiO2, has widespread applications ranging from optical components to refractory materials and is of geological importance as one of the major oxide components of the Earth's crust and mantle. The response of silica phases to dynamic loading has long been of interest for understanding the structural evolution of this fundamental oxide. Under shock compression both crystalline quartz and fused silica are characterized by the occurrence of a broad `mixed-phase region' (15-40 GPa) and a dense, high-pressure phase with much lower compressibility. Despite decades of study, the nature of this transformation and the identity of the high-pressure phase(s) remain poorly understood. In situ x-ray diffraction experiments on shock-compressed fused silica were conducted at the Dynamic Compression Sector of the Advanced Photon Source. The lattice-level structure was investigated through time-resolved x-ray diffraction measurements on samples reaching peak stress ranging from 12 to 47 GPa. Our results demonstrate that SiO2 adopts a dense amorphous structure in the `mixed-phase region' and abruptly transforms to stishovite above 34 GPa. These results provide clear evidence that high-pressure crystalline silicate phases can form from amorphous starting materials on the time-scale of laboratory shock experiments.

Effect of a core-softened O-O interatomic interaction on the shock compression of fused silica

NASA Astrophysics Data System (ADS)

Izvekov, Sergei; Weingarten, N. Scott; Byrd, Edward F. C.

2018-03-01

Isotropic soft-core potentials have attracted considerable attention due to their ability to reproduce thermodynamic, dynamic, and structural anomalies observed in tetrahedral network-forming compounds such as water and silica. The aim of the present work is to assess the relevance of effective core-softening pertinent to the oxygen-oxygen interaction in silica to the thermodynamics and phase change mechanisms that occur in shock compressed fused silica. We utilize the MD simulation method with a recently published numerical interatomic potential derived from an ab initio MD simulation of liquid silica via force-matching. The resulting potential indicates an effective shoulder-like core-softening of the oxygen-oxygen repulsion. To better understand the role of the core-softening we analyze two derivative force-matching potentials in which the soft-core is replaced with a repulsive core either in the three-body potential term or in all the potential terms. Our analysis is further augmented by a comparison with several popular empirical models for silica that lack an explicit core-softening. The first outstanding feature of shock compressed glass reproduced with the soft-core models but not with the other models is that the shock compression values at pressures above 20 GPa are larger than those observed under hydrostatic compression (an anomalous shock Hugoniot densification). Our calculations indicate the occurrence of a phase transformation along the shock Hugoniot that we link to the O-O repulsion core-softening. The phase transformation is associated with a Hugoniot temperature reversal similar to that observed experimentally. With the soft-core models, the phase change is an isostructural transformation between amorphous polymorphs with no associated melting event. We further examine the nature of the structural transformation by comparing it to the Hugoniot calculations for stishovite. For stishovite, the Hugoniot exhibits temperature reversal and associated phase transformation, which is a transition to a disordered phase (liquid or dense amorphous), regardless of whether or not the model accounts for core-softening. The onset pressures of the transformation predicted by different models show a wide scatter within 60-110 GPa; for potentials without core-softening, the onset pressure is much higher than 110 GPa. Our results show that the core-softening of the interaction in the oxygen subsystem of silica is the key mechanism for the structural transformation and thermodynamics in shock compressed silica. These results may provide an important contribution to a unified picture of anomalous response to shock compression observed in other network-forming oxides and single-component systems with core-softening of effective interactions.

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.

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.

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.

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.

Safety and Efficacy of Defibrillator Charging During Ongoing Chest Compressions: A Multicenter Study

PubMed Central

Edelson, Dana P.; Robertson-Dick, Brian J.; Yuen, Trevor C.; Eilevstjønn, Joar; Walsh, Deborah; Bareis, Charles J.; Vanden Hoek, Terry L.; Abella, Benjamin S.

2013-01-01

BACKGROUND Pauses in chest compressions during cardiopulmonary resuscitation have been shown to correlate with poor outcomes. In an attempt to minimize these pauses, the American Heart Association recommends charging the defibrillator during chest compressions. While simulation work suggests decreased pause times using this technique, little is known about its use in clinical practice. METHODS We conducted a multicenter, retrospective study of defibrillator charging at three US academic teaching hospitals between April 2006 and April 2009. Data were abstracted from CPR-sensing defibrillator transcripts. Pre-shock pauses and total hands- off time preceding the defibrillation attempts were compared among techniques. RESULTS A total of 680 charge-cycles from 244 cardiac arrests were analyzed. The defibrillator was charged during ongoing chest compressions in 448 (65.9%) instances with wide variability across the three sites. Charging during compressions correlated with a decrease in median pre-shock pause [2.6 (IQR 1.9–3.8) vs 13.3 (IQR 8.6–19.5) s; p < 0.001] and total hands-off time in the 30 s preceding defibrillation [10.3 (IQR 6.4–13.8) vs 14.8 (IQR 11.0–19.6) s; p < 0.001]. The improvement in hands-off time was most pronounced when rescuers charged the defibrillator in anticipation of the pause, prior to any rhythm analysis. There was no difference in inappropriate shocks when charging during chest compressions (20.0 vs 20.1%; p=0.97) and there was only one instance noted of inadvertent shock administration during compressions, which went unnoticed by the compressor. CONCLUSIONS Charging during compressions is underutilized in clinical practice. The technique is associated with decreased hands-off time preceding defibrillation, with minimal risk to patients or rescuers. PMID:20807672

Monte Carlo simulation of steady state shock structure including cosmic ray mediation and particle escape

NASA Technical Reports Server (NTRS)

Ellison, D. C.; Jones, F. C.; Eichler, D.

1983-01-01

Both hydrodynamic calculations (Drury and Volk, 1981, and Axford et al., 1982) and kinetic simulations imply the existence of thermal subshocks in high-Mach-number cosmic-ray-mediated shocks. The injection efficiency of particles from the thermal background into the diffusive shock-acceleration process is determined in part by the sharpness and compression ratio of these subshocks. Results are reported for a Monte Carlo simulation that includes both the back reaction of accelerated particles on the inflowing plasma, producing a smoothing of the shock transition, and the free escape of particles allowing arbitrarily large overall compression ratios in high-Mach-number steady-state shocks. Energy spectra and estimates of the proportion of thermal ions accelerated to high energy are obtained.

Monte Carlo simulation of steady state shock structure including cosmic ray mediation and particle escape

NASA Astrophysics Data System (ADS)

Ellison, D. C.; Jones, F. C.; Eichler, D.

1983-08-01

Both hydrodynamic calculations (Drury and Volk, 1981, and Axford et al., 1982) and kinetic simulations imply the existence of thermal subshocks in high-Mach-number cosmic-ray-mediated shocks. The injection efficiency of particles from the thermal background into the diffusive shock-acceleration process is determined in part by the sharpness and compression ratio of these subshocks. Results are reported for a Monte Carlo simulation that includes both the back reaction of accelerated particles on the inflowing plasma, producing a smoothing of the shock transition, and the free escape of particles allowing arbitrarily large overall compression ratios in high-Mach-number steady-state shocks. Energy spectra and estimates of the proportion of thermal ions accelerated to high energy are obtained.

Energy recovery during expansion of compressed gas using power plant low-quality heat sources

DOEpatents

Ochs, Thomas L [Albany, OR; O'Connor, William K [Lebanon, OR

2006-03-07

A method of recovering energy from a cool compressed gas, compressed liquid, vapor, or supercritical fluid is disclosed which includes incrementally expanding the compressed gas, compressed liquid, vapor, or supercritical fluid through a plurality of expansion engines and heating the gas, vapor, compressed liquid, or supercritical fluid entering at least one of the expansion engines with a low quality heat source. Expansion engines such as turbines and multiple expansions with heating are disclosed.

Two-Fluid Description of Collisionless Perpendicular Shocks

NASA Astrophysics Data System (ADS)

Gomez, D. O.; Morales, L. F.; Dmitruk, P.; Bertucci, C.

2017-12-01

Collisionless shocks are ubiquitous in space physics and astrophysics, such as the bow shocks formed by the solar wind in front of planets, the termination shock at the heliospheric boundary or the supernova shock fronts expanding in the interstellar plasma. Although the one-fluid magnetohydrodynamic framework provides a reasonable description of the large scale structures of the upstream and downstream plasmas, it falls short of providing an adequate description of the internal structure of the shock. A more comprehensive description of the inner and outer features of collisionless shocks would require the use of kinetic theory. Nonetheless, in the present work we show that a complete two-fluid framework (considering the role of both ions and electrons in the dynamics) can properly capture some of the features observed in real shocks. For the specific case of perpendicular shocks, i.e. cases in which the magnetic field is perpendicular to the shock normal, we integrate the one-dimensional two-fluid MHD equations numerically, to describe the generation of shocks and their spatial structure along the shock normal. Starting from finite amplitude fast-magnetosonic waves, our simulations show the generation of a stationary fast-magnetosonic shock. More importantly, we show that the ramp thickness is of the order of a few electron inertial lengths. The parallel and perpendicular components of the self-consistent electric field are derived, and their role in accelerating particles is discussed.

A mechanism for pressure anisotropy and mirror instability in the dayside magnetosheath

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

Crooker, N.U.; Siscoe, G.L.

1977-01-01

The plasma in the dayside magnetosheaht exhibits a persistent pressure anisotropy in the sense p/sub perpendicular/>p/sub parallel/. A likely source for this anisotropy is the effect of field compression and plasma depletion along field lines as magnetosheath plasma flows toward the magnetopause. The model of Zwan and Wolf describing this effect for the case of isotropic pressure is combined with the double-adiabatic fluid equations to predict the behavior of the anisotropic pressure. For a fluid element following a streamline inward from the bow shock, we find theoretical pressure anisotropies of magnitude large enough to trigger the mirror instability over mostmore » of the dayside magnetosheath. These findings are supported by the observations of Kaufmann et al. of large-amplitude hydromagnetic waves in the inner magnetosheath believed to be generated by the mirror instability. (AIP)« less

ISCFD Nagoya 1989 - International Symposium on Computational Fluid Dynamics, 3rd, Nagoya, Japan, Aug. 28-31, 1989, Technical Papers

NASA Astrophysics Data System (ADS)

Recent advances in computational fluid dynamics are discussed in reviews and reports. Topics addressed include large-scale LESs for turbulent pipe and channel flows, numerical solutions of the Euler and Navier-Stokes equations on parallel computers, multigrid methods for steady high-Reynolds-number flow past sudden expansions, finite-volume methods on unstructured grids, supersonic wake flow on a blunt body, a grid-characteristic method for multidimensional gas dynamics, and CIC numerical simulation of a wave boundary layer. Consideration is given to vortex simulations of confined two-dimensional jets, supersonic viscous shear layers, spectral methods for compressible flows, shock-wave refraction at air/water interfaces, oscillatory flow in a two-dimensional collapsible channel, the growth of randomness in a spatially developing wake, and an efficient simplex algorithm for the finite-difference and dynamic linear-programming method in optimal potential control.

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.

An equation of state for polyurea aerogel based on multi-shock response

NASA Astrophysics Data System (ADS)

Aslam, T. D.; Gustavsen, R. L.; Bartram, B. D.

2014-05-01

The equation of state (EOS) of polyurea aerogel (PUA) is examined through both single shock Hugoniot data as well as more recent multi-shock compression experiments performed on the LANL 2-stage gas gun. A simple conservative Lagrangian numerical scheme, utilizing total variation diminishing (TVD) interpolation and an approximate Riemann solver, will be presented as well as the methodology of calibration. It will been demonstrated that a p-a model based on a Mie-Gruneisen fitting form for the solid material can reasonably replicate multi-shock compression response at a variety of initial densities; such a methodology will be presented for a commercially available polyurea aerogel.

Transformation of shock-compressed graphite to hexagonal diamond in nanoseconds

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

Turneaure, Stefan J.; Sharma, Surinder M.; Volz, Travis J.

2017-10-01

The graphite-to-diamond transformation under shock compression has been of broad scientific interest since 1961. The formation of hexagonal diamond (HD) is of particular interest because it is expected to be harder than cubic diamond and due to its use in terrestrial sciences as a marker at meteorite impact sites. However, the formation of diamond having a fully hexagonal structure continues to be questioned and remains unresolved. Using real-time (nanosecond), in situ x-ray diffraction measurements, we show unequivocally that highly oriented pyrolytic graphite, shock-compressed along the c axis to 50 GPa, transforms to highly oriented elastically strained HD with the (100)HDmore » plane parallel to the graphite basal plane.« less

Simulations of X-ray diffraction of shock-compressed single-crystal tantalum with synchrotron undulator sources.

PubMed

Tang, M X; Zhang, Y Y; E, J C; Luo, S N

2018-05-01

Polychromatic synchrotron undulator X-ray sources are useful for ultrafast single-crystal diffraction under shock compression. Here, simulations of X-ray diffraction of shock-compressed single-crystal tantalum with realistic undulator sources are reported, based on large-scale molecular dynamics simulations. Purely elastic deformation, elastic-plastic two-wave structure, and severe plastic deformation under different impact velocities are explored, as well as an edge release case. Transmission-mode diffraction simulations consider crystallographic orientation, loading direction, incident beam direction, X-ray spectrum bandwidth and realistic detector size. Diffraction patterns and reciprocal space nodes are obtained from atomic configurations for different loading (elastic and plastic) and detection conditions, and interpretation of the diffraction patterns is discussed.

Simulations of X-ray diffraction of shock-compressed single-crystal tantalum with synchrotron undulator sources

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

Tang, M. X.; Zhang, Y. Y.; E, J. C.

Polychromatic synchrotron undulator X-ray sources are useful for ultrafast single-crystal diffraction under shock compression. Here, simulations of X-ray diffraction of shock-compressed single-crystal tantalum with realistic undulator sources are reported, based on large-scale molecular dynamics simulations. Purely elastic deformation, elastic–plastic two-wave structure, and severe plastic deformation under different impact velocities are explored, as well as an edge release case. Transmission-mode diffraction simulations consider crystallographic orientation, loading direction, incident beam direction, X-ray spectrum bandwidth and realistic detector size. Diffraction patterns and reciprocal space nodes are obtained from atomic configurations for different loading (elastic and plastic) and detection conditions, and interpretation of themore » diffraction patterns is discussed.« less

Experimental Simulation of Shock Reequilibration of Fluid Inclusions During Meteorite Impact

NASA Technical Reports Server (NTRS)

Madden, M. E. Elwood; Hoerz, R. J.; Bodnar, R. J.

2003-01-01

Fluid inclusions are microscopic volumes of fluid trapped within minerals as they precipitate. Fluid inclusions are common in terrestrial minerals formed under a wide array of geological settings from surface evaporite deposits to kimberlite pipes. While fluid inclusions in terrestrial rocks are the rule rather than the exception, only few fluid inclusion-bearing meteorites have been documented. The rarity of fluid inclusions in meteoritic material may be explained in two ways. First, it may reflect the absence of fluids (water?) on meteorite parent bodies. Alternatively, fluids may have been present when the rock formed, but any fluid inclusions originally trapped on the parent body were destroyed by the extreme P-T conditions meteorites often experience during impact events. Distinguishing between these two possibilities can provide significant constraints on the likelihood of life on the parent body. Just as textures, structures, and compositions of mineral phases can be significantly altered by shock metamorphism upon hypervelocity impact, fluid inclusions contained within component minerals may be altered or destroyed due to the high pressures, temperatures, and strain rates associated with impact events. Reequilibration may occur when external pressure-temperature conditions differ significantly from internal fluid isochoric conditions, and result in changes in fluid inclusion properties and/or textures. Shock metamorphism and fluid inclusion reequilibration can affect both the impacted target material and the meteoritic projectile. By examining the effects of shock deformation on fluid inclusion properties and textures we may be able to better constrain the pressure-temperature path experienced by shocked materials and also gain a clearer understanding of why fluid inclusions are rarely found in meteoritic samples.

Integration of a wave rotor to an ultra-micro gas turbine (UmuGT)

NASA Astrophysics Data System (ADS)

Iancu, Florin

2005-12-01

Wave rotor technology has shown a significant potential for performance improvement of thermodynamic cycles. The wave rotor is an unsteady flow machine that utilizes shock waves to transfer energy from a high energy fluid to a low energy fluid, increasing both the temperature and the pressure of the low energy fluid. Used initially as a high pressure stage for a gas turbine locomotive engine, the wave rotor was commercialized only as a supercharging device for internal combustion engines, but recently there is a stronger research effort on implementing wave rotors as topping units or pressure gain combustors for gas turbines. At the same time, Ultra Micro Gas Turbines (UmuGT) are expected to be a next generation of power source for applications from propulsion to power generation, from aerospace industry to electronic industry. Starting in 1995, with the MIT "Micro Gas Turbine" project, the mechanical engineering research world has explored more and more the idea of "Power MEMS". Microfabricated turbomachinery like turbines, compressors, pumps, but also electric generators, heat exchangers, internal combustion engines and rocket engines have been on the focus list of researchers for the past 10 years. The reason is simple: the output power is proportional to the mass flow rate of the working fluid through the engine, or the cross-sectional area while the mass or volume of the engine is proportional to the cube of the characteristic length, thus the power density tends to increase at small scales (Power/Mass=L -1). This is the so-called "cube square law". This work investigates the possibilities of incorporating a wave rotor to an UmuGT and discusses the advantages of wave rotor as topping units for gas turbines, especially at microscale. Based on documented wave rotor efficiencies at larger scale and subsidized by both, a gasdynamic model that includes wall friction, and a CFD model, the wave rotor compression efficiency at microfabrication scale could be estimated at about 70%, which is much higher than the obtained efficiency obtained for centrifugal compressors in a microfabricated gas turbine. This dissertation also proposes several designs of ultra-micro wave rotors, including the novel concept of a radial-flow configuration. It describes a new and simplified design procedure as well as numerical simulations of these wave rotors. Results are obtained using FLUENT, a Computational Fluid Dynamics (CFD) commercial code. The vast information about the unsteady processes occurring during simulation is visualized. Last, two designs for experimental tests have been created, one for a micro shock tube and one for the ultra-micro wave rotor. Theoretical and numerical results encourage the idea that at microscale, compression by shock waves may be more efficient than by conventional centrifugal compressors, thus making the ultra-micro wave rotor (UmuWR) a feasible idea for enhancing (upgrading) UmuGT.

Studies of Shock Wave Interactions with Homogeneous and Isotropic Turbulence

NASA Technical Reports Server (NTRS)

Briassulis, G.; Agui, J.; Watkins, C. B.; Andreopoulos, Y.

1998-01-01

A nearly homogeneous nearly isotropic compressible turbulent flow interacting with a normal shock wave has been studied experimentally in a large shock tube facility. Spatial resolution of the order of 8 Kolmogorov viscous length scales was achieved in the measurements of turbulence. A variety of turbulence generating grids provide a wide range of turbulence scales. Integral length scales were found to substantially decrease through the interaction with the shock wave in all investigated cases with flow Mach numbers ranging from 0.3 to 0.7 and shock Mach numbers from 1.2 to 1.6. The outcome of the interaction depends strongly on the state of compressibility of the incoming turbulence. The length scales in the lateral direction are amplified at small Mach numbers and attenuated at large Mach numbers. Even at large Mach numbers amplification of lateral length scales has been observed in the case of fine grids. In addition to the interaction with the shock the present work has documented substantial compressibility effects in the incoming homogeneous and isotropic turbulent flow. The decay of Mach number fluctuations was found to follow a power law similar to that describing the decay of incompressible isotropic turbulence. It was found that the decay coefficient and the decay exponent decrease with increasing Mach number while the virtual origin increases with increasing Mach number. A mechanism possibly responsible for these effects appears to be the inherently low growth rate of compressible shear layers emanating from the cylindrical rods of the grid.

Velocity measurement using frequency domain interferometer and chirped pulse laser

NASA Astrophysics Data System (ADS)

Ishii, K.; Nishimura, Y.; Mori, Y.; Hanayama, R.; Kitagawa, Y.; Sekine, T.; Sato, N.; Kurita, T.; Kawashima, T.; Sunahara, A.; Sentoku, Y.; Miura, E.; Iwamoto, A.; Sakagami, H.

2017-02-01

An ultra-intense short pulse laser induces a shock wave in material. The pressure of shock compression is stronger than a few tens GPa. To characterize shock waves, time-resolved velocity measurement in nano- or pico-second time scale is needed. Frequency domain interferometer and chirped pulse laser provide single-shot time-resolved measurement. We have developed a laser-driven shock compression system and frequency domain interferometer with CPA laser. In this paper, we show the principle of velocity measurement using a frequency domain interferometer and a chirped pulse laser. Next, we numerically calculated spectral interferograms and show the time-resolved velocity measurement can be done from the phase analysis of spectral interferograms. Moreover we conduct the laser driven shock generation and shock velocity measurement. From the spectral fringes, we analyze the velocities of the sample and shockwaves.

Shock wave treatment improves nerve regeneration in the rat.

PubMed

Mense, Siegfried; Hoheisel, Ulrich

2013-05-01

The aims of the experiments were to: (1) determine whether low-energy shock wave treatment accelerates the recovery of muscle sensitivity and functionality after a nerve lesion; and (2) assess the effect of shock waves on the regeneration of injured nerve fibers. After compression of a muscle nerve in rats the effects of shock wave treatment on the sequelae of the lesion were tested. In non-anesthetized animals, pressure pain thresholds and exploratory activity were determined. The influence of the treatment on the distance of nerve regeneration was studied in immunohistochemical experiments. Both behavioral and immunohistochemical data show that shock wave treatment accelerates the recovery of muscle sensitivity and functionality and promotes regeneration of injured nerve fibers. Treatment with focused shock waves induces an improvement of nerve regeneration in a rodent model of nerve compression. Copyright © 2012 Wiley Periodicals, Inc.

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

Existence and Stability of Compressible Current-Vortex Sheets in Three-Dimensional Magnetohydrodynamics

NASA Astrophysics Data System (ADS)

Chen, Gui-Qiang; Wang, Ya-Guang

2008-03-01

Compressible vortex sheets are fundamental waves, along with shocks and rarefaction waves, in entropy solutions to multidimensional hyperbolic systems of conservation laws. Understanding the behavior of compressible vortex sheets is an important step towards our full understanding of fluid motions and the behavior of entropy solutions. For the Euler equations in two-dimensional gas dynamics, the classical linearized stability analysis on compressible vortex sheets predicts stability when the Mach number M > sqrt{2} and instability when M < sqrt{2} ; and Artola and Majda’s analysis reveals that the nonlinear instability may occur if planar vortex sheets are perturbed by highly oscillatory waves even when M > sqrt{2} . For the Euler equations in three dimensions, every compressible vortex sheet is violently unstable and this instability is the analogue of the Kelvin Helmholtz instability for incompressible fluids. The purpose of this paper is to understand whether compressible vortex sheets in three dimensions, which are unstable in the regime of pure gas dynamics, become stable under the magnetic effect in three-dimensional magnetohydrodynamics (MHD). One of the main features is that the stability problem is equivalent to a free-boundary problem whose free boundary is a characteristic surface, which is more delicate than noncharacteristic free-boundary problems. Another feature is that the linearized problem for current-vortex sheets in MHD does not meet the uniform Kreiss Lopatinskii condition. These features cause additional analytical difficulties and especially prevent a direct use of the standard Picard iteration to the nonlinear problem. In this paper, we develop a nonlinear approach to deal with these difficulties in three-dimensional MHD. We first carefully formulate the linearized problem for the current-vortex sheets to show rigorously that the magnetic effect makes the problem weakly stable and establish energy estimates, especially high-order energy estimates, in terms of the nonhomogeneous terms and variable coefficients. Then we exploit these results to develop a suitable iteration scheme of the Nash Moser Hörmander type to deal with the loss of the order of derivative in the nonlinear level and establish its convergence, which leads to the existence and stability of compressible current-vortex sheets, locally in time, in three-dimensional MHD.

Process and application of shock compression by nanosecond pulses of frequency-doubled Nd:YAG laser

NASA Astrophysics Data System (ADS)

Sano, Yuji; Kimura, Motohiko; Mukai, Naruhiko; Yoda, Masaki; Obata, Minoru; Ogisu, Tatsuki

2000-02-01

The authors have developed a new process of laser-induced shock compression to introduce a residual compressive stress on material surface, which is effective for prevention of stress corrosion cracking (SCC) and enhancement of fatigue strength of metal materials. The process developed is unique and beneficial. It requires no pre-conditioning for the surface, whereas the conventional process requires that the so-called sacrificial layer is made to protect the surface from damage. The new process can be freely applied to water- immersed components, since it uses water-penetrable green light of a frequency-doubled Nd:YAG laser. The process developed has the potential to open up new high-power laser applications in manufacturing and maintenance technologies. The laser-induced shock compression process (LSP) can be used to improve a residual stress field from tensile to compressive. In order to understand the physics and optimize the process, the propagation of a shock wave generated by the impulse of laser irradiation and the dynamic response of the material were analyzed by time-dependent elasto-plastic calculations with a finite element program using laser-induced plasma pressure as an external load. The analysis shows that a permanent strain and a residual compressive stress remain after the passage of the shock wave with amplitude exceeding the yield strength of the material. A practical system materializing the LSP was designed, manufactured, and tested to confirm the applicability to core components of light water reactors (LWRs). The system accesses the target component and remotely irradiates laser pulses to the heat affected zone (HAZ) along weld lines. Various functional tests were conducted using a full-scale mockup facility, in which remote maintenance work in a reactor vessel could be simulated. The results showed that the system remotely accessed the target weld lines and successfully introduced a residual compressive stress. After sufficient training for operational personnel, the system was applied to the core shroud of an existing nuclear power plant.

Observation of Dispersive Shock Waves, Solitons, and Their Interactions in Viscous Fluid Conduits.

PubMed

Maiden, Michelle D; Lowman, Nicholas K; Anderson, Dalton V; Schubert, Marika E; Hoefer, Mark A

2016-04-29

Dispersive shock waves and solitons are fundamental nonlinear excitations in dispersive media, but dispersive shock wave studies to date have been severely constrained. Here, we report on a novel dispersive hydrodynamic test bed: the effectively frictionless dynamics of interfacial waves between two high viscosity contrast, miscible, low Reynolds number Stokes fluids. This scenario is realized by injecting from below a lighter, viscous fluid into a column filled with high viscosity fluid. The injected fluid forms a deformable pipe whose diameter is proportional to the injection rate, enabling precise control over the generation of symmetric interfacial waves. Buoyancy drives nonlinear interfacial self-steepening, while normal stresses give rise to the dispersion of interfacial waves. Extremely slow mass diffusion and mass conservation imply that the interfacial waves are effectively dissipationless. This enables high fidelity observations of large amplitude dispersive shock waves in this spatially extended system, found to agree quantitatively with a nonlinear wave averaging theory. Furthermore, several highly coherent phenomena are investigated including dispersive shock wave backflow, the refraction or absorption of solitons by dispersive shock waves, and the multiphase merging of two dispersive shock waves. The complex, coherent, nonlinear mixing of dispersive shock waves and solitons observed here are universal features of dissipationless, dispersive hydrodynamic flows.

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.

Pre-strain effect on frequency-based impact energy dissipation through a silicone foam pad for shock mitigation [Pre-strain effect on the frequency response of shock mitigation through a silicone foam pad

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

Sanborn, Brett; Song, Bo; Smith, Scott

Silicone foams have been used in a variety of applications from gaskets to cushioning pads over a wide range of environments. Particularly, silicone foams are used as a shock mitigation material for shock and vibration applications. Understanding the shock mitigation response, particularly in the frequency domain, is critical for optimal designs to protect internal devices and components more effectively and efficiently. The silicone foams may be subjected to pre-strains during the assembly process which may consequently influence the frequency response with respect to shock mitigation performance. A Kolsky compression bar was modified with pre-compression capabilities to characterize the shock mitigationmore » response of silicone foam in the frequency domain to determine the effect of pre-strain. Lastly, a silicone sample was also intentionally subjected to repeated pre-strain and dynamic loadings to explore the effect of repeated loading on the frequency response of shock mitigation.« less

Pre-strain effect on frequency-based impact energy dissipation through a silicone foam pad for shock mitigation [Pre-strain effect on the frequency response of shock mitigation through a silicone foam pad

DOE PAGES

Sanborn, Brett; Song, Bo; Smith, Scott

2015-12-29

Silicone foams have been used in a variety of applications from gaskets to cushioning pads over a wide range of environments. Particularly, silicone foams are used as a shock mitigation material for shock and vibration applications. Understanding the shock mitigation response, particularly in the frequency domain, is critical for optimal designs to protect internal devices and components more effectively and efficiently. The silicone foams may be subjected to pre-strains during the assembly process which may consequently influence the frequency response with respect to shock mitigation performance. A Kolsky compression bar was modified with pre-compression capabilities to characterize the shock mitigationmore » response of silicone foam in the frequency domain to determine the effect of pre-strain. Lastly, a silicone sample was also intentionally subjected to repeated pre-strain and dynamic loadings to explore the effect of repeated loading on the frequency response of shock mitigation.« less

Shock compression and flash-heating of molecular adsorbates on the picosecond time scale

NASA Astrophysics Data System (ADS)

Berg, Christopher Michael

An ultrafast nonlinear coherent laser spectroscopy termed broadband multiplex vibrational sum-frequency generation (SFG) with nonresonant suppression was employed to monitor vibrational transitions of molecular adsorbates on metallic substrates during laser-driven shock compression and flash-heating. Adsorbates were in the form of well-ordered self-assembled monolayers (SAMs) and included molecular explosive simulants, such as nitroaromatics, and long chain-length alkanethiols. Based on reflectance measurements of the metallic substrates, femtosecond flash-heating pulses were capable of producing large-amplitude temperature jumps with DeltaT = 500 K. Laser-driven shock compression of SAMs produced pressures up to 2 GPa, where 1 GPa ≈ 1 x 104 atm. Shock pressures were estimated via comparison with frequency shifts observed in the monolayer vibrational transitions during hydrostatic pressure measurements in a SiC anvil cell. Molecular dynamics during flash-heating and shock loading were probed with vibrational SFG spectroscopy with picosecond temporal resolution and sub-nanometer spatial resolution. Flash-heating studies of 4-nitrobenzenethiolate (NBT) on Au provided insight into effects from hot-electron excitation of the molecular adsorbates at early pump-probe delay times. At longer delay times, effects from the excitation of SAM lattice modes and lower-energy NBT vibrations were shown. In addition, flash-heating studies of alkanethiolates demonstrated chain disordering behaviors as well as interface thermal conductances across the Au-SAM junction, which was of specific interest within the context of molecular electronics. Shock compression studies of molecular explosive simulants, such as 4-nitrobenzoate (NBA), demonstrated the proficiency of this technique to observe shock-induced molecular dynamics, in this case orientational dynamics, on the picosecond time scale. Results validated the utilization of these refined shock loading techniques to probe the shock initiation or first bond-breaking reactions in molecular explosives such as delta-HMX: a necessary study for the development of safer and more effective energetic materials.

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

DOE PAGES

Mikaelian, Karnig O.

2016-07-13

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

Density Effects on Post-shock Turbulence Structure

NASA Astrophysics Data System (ADS)

Tian, Yifeng; Jaberi, Farhad; Livescu, Daniel; Li, Zhaorui; Michigan State University Collaboration; Los Alamos National Laboratory Collaboration; Texas A&M University-Corpus Christi Collaboration

2017-11-01

The effects of density variations due to mixture composition on post-shock turbulence structure are studied using turbulence-resolving shock-capturing simulations. This work extends the canonical Shock-Turbulence Interaction (STI) problem to involve significant variable density effects. The numerical method has been verified using a series of grid and LIA convergence tests, and is used to generate accurate post-shock turbulence data for a detailed flow study. Density effects on post-shock turbulent statistics are shown to be significant, leading to an increased amplification of turbulent kinetic energy (TKE). Eulerian and Lagrangian analyses show that the increase in the post-shock correlation between rotation and strain is weakened in the case with significant density variations (referred to as the ``multi-fluid'' case). Similar to previous single-fluid results and LIA predictions, the shock wave significantly changes the topology of the turbulent structures, exhibiting a symmetrization of the joint PDF of second and third invariant of the deviatoric part of velocity gradient tensor. In the multi-fluid case, this trend is more significant and mainly manifested in the heavy fluid regions. Lagrangian data are also used to study the evolution of turbulence structure away from the shock wave and assess the accuracy of Lagrangian dynamical models.

Heat shock protein-containing exosomes in mid-trimester amniotic fluids.

PubMed

Asea, Alexzander; Jean-Pierre, Claudel; Kaur, Punit; Rao, Preethi; Linhares, Iara M; Skupski, Daniel; Witkin, Steven S

2008-10-01

Exosomes are multivesicular bodies formed by inverse membrane budding into the lumen of an endocytic compartment. Fusion with the plasma membrane leads to their release into the external milieu. The incorporation of heat shock proteins into exosomes has been associated with immune regulatory activity. We have examined whether heat shock protein-containing exosomes are present in mid-trimester amniotic fluid. Exosomes were isolated from mid-trimester amniotic fluids by sequential low-speed and high-speed centrifugation followed by sucrose density gradient centrifugation. Biochemical characterization included floatation pattern in sucrose gradients, acetylcholinesterase (AChE) activity and Western blot analysis for exosome-containing proteins. Exosomes were present in each of 23 amniotic fluids tested. They banded at a density of 1.17g/ml in sucrose gradients, were positive for AChE activity and contained tubulin, the inducible 72kDa heat shock protein, Hsp72 and the constitutively expressed heat shock protein, Hsc73; they were negative for calnexin. Exosome concentrations correlated positively with the number of pregnancies. Heat shock protein-containing exosomes are constituents of mid-trimester amniotic fluids and may contribute to immune regulation within the amniotic cavity.

Shock wave compression of iron-silicate garnet.

NASA Technical Reports Server (NTRS)

Graham, E. K.; Ahrens, T. J.

1973-01-01

Shock wave compression data to over 650 kb are presented for single-crystal almandine garnet. The data indicate the initiation of a phase transformation near 200 kb. Total transition to the high-pressure polymorph occurs at approximately 300 kb. The elastic properties of the high-pressure phase are calculated from the metastable Hugoniot data by using the linear shock velocity-particle velocity relationships. The overall results obtained strongly suggest that upper mantle minerals are likely to occur in the ilmenite structure over a substantial part of the lower mantle.

THE EFFECT OF LASER SHOCK PEENING ON THE LIFE AND FAILURE MODE OF A COLD PILGER DIE

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

Lavender, Curt A.; Hong, Sung-tae; Smith, Mark T.

2008-08-11

The laser shock peening process was used to increase fatigue life of pilger dies made of A2 tool steel by imparting compressive residual stresses to fatigue prone areas of the dies. The result of X-Ray diffraction analysis indicated that deep, high- magnitude compressive residual stresses were generated by the laser shock peening process, and the peened dies exhibited a significant increase of in-service life. Fractography of the failed dies indicates that the fracture mechanism was altered by the peening process.

X-ray diffraction from shock-loaded polycrystals.

PubMed

Swift, Damian C

2008-01-01

X-ray diffraction was demonstrated from shock-compressed polycrystalline metals on nanosecond time scales. Laser ablation was used to induce shock waves in polycrystalline foils of Be, 25-125 microm thick. A second laser pulse was used to generate a plasma x-ray source by irradiation of a Ti foil. The x-ray source was collimated to produce a beam of controllable diameter, which was directed at the Be sample. X-rays were diffracted from the sample, and detected using films and x-ray streak cameras. The diffraction angle was observed to change with shock pressure. The diffraction angles were consistent with the uniaxial (elastic) and isotropic (plastic) compressions expected for the loading conditions used. Polycrystalline diffraction will be used to measure the response of the crystal lattice to high shock pressures and through phase changes.

Head-on collision of normal shock waves with rigid porous materials

NASA Astrophysics Data System (ADS)

Levy, A.; Ben-Dor, G.; Skews, B. W.; Sorek, S.

1993-08-01

The head-on collision of a planar shock wave with a rigid porous material has been investigated experimentally in a 75 mm × 75 mm shock tube. The experimental study indicated that unlike the reflection from a flexible porous material (e.g., polyurethane foam) where the transmitted compression waves do not converge to a sharp shock wave, in the case of a rigid porous material (e.g., alumina) the transmitted compression waves do converge to a sharp shock wave, which decays as it propagates along the porous material. In addition to this major difference, many other differences were observed. They are outlined in the following sections. Based on these observations a suggestion modifying the phenomenology of the reflection/interaction process in the case a porous material with large permeability is proposed.

Directional amorphization of boron carbide subjected to laser shock compression.

PubMed

Zhao, Shiteng; Kad, Bimal; Remington, Bruce A; LaSalvia, Jerry C; Wehrenberg, Christopher E; Behler, Kristopher D; Meyers, Marc A

2016-10-25

Solid-state shock-wave propagation is strongly nonequilibrium in nature and hence rate dependent. Using high-power pulsed-laser-driven shock compression, unprecedented high strain rates can be achieved; here we report the directional amorphization in boron carbide polycrystals. At a shock pressure of 45∼50 GPa, multiple planar faults, slightly deviated from maximum shear direction, occur a few hundred nanometers below the shock surface. High-resolution transmission electron microscopy reveals that these planar faults are precursors of directional amorphization. It is proposed that the shear stresses cause the amorphization and that pressure assists the process by ensuring the integrity of the specimen. Thermal energy conversion calculations including heat transfer suggest that amorphization is a solid-state process. Such a phenomenon has significant effect on the ballistic performance of B 4 C.

Hugoniot temperatures and melting of tantalum under shock compression determined by optical pyrometry

NASA Astrophysics Data System (ADS)

Dai, Chengda; Hu, Jianbo; Tan, Hua

2009-08-01

LiF single crystal was used as transparent window (anvil) to tamp the shock-induced free surface expansion of Ta specimen, and the Ta/LiF interface temperature was measured under shock compression using optical pyrometry technique. The shock temperatures and/or melting temperatures of Ta up to ˜400 GPa were extracted from the observed interface temperatures based on the Tan-Ahrens' model for one-dimensional heat conduction across metal/window ideal interface in which initial melting and subsequent solidification were considered under shock loading. The obtained data within the experimental uncertainties are consistent with the results from high-pressure sound velocity measurements. The temperature of the partial melting on Ta Hugoniot is estimated to be ˜9700 K at 300 GPa, supported by available results from theoretical calculations.

Universal penetration test apparatus with fluid penetration sensor

DOEpatents

Johnson, Phillip W.; Stampfer, Joseph F.; Bradley, Orvil D.

1999-01-01

A universal penetration test apparatus for measuring resistance of a material to a challenge fluid. The apparatus includes a pad saturated with the challenge fluid. The apparatus includes a compression assembly for compressing the material between the pad and a compression member. The apparatus also includes a sensor mechanism for automatically detecting when the challenge fluid penetrates the material.

Electrical conductivity of aluminum hydride AlH3 at high pressure and temperature

NASA Astrophysics Data System (ADS)

Shakhray, Denis; Molodets, Alexander; Fortov, Vladimir; Khrapak, Aleksei

2009-06-01

A study of electrophysical and thermodynamic properties of alane AlH3 under multi shock compression has been carried out. The increase in specific electroconductivity of alane at shock compression up to pressure 100 GPa have been measured. High pressures and temperatures were obtained with explosive device, which accelerates the stainless impactor up to 3 km/sec. The impact shock is split into a shock wave reverberating in alane between two stiff metal anvils. The conductivity of shocked alane increases in the range up to 60-75 GPa and is about 30 1/Ohm*cm. In this region the semiconductor regime is true for shocked alane. The conductivity of alane achieves approximately 500 1/Ohm*cm at 80-90 GPa. In this region conductivity is interpreted in frames of the conception of the ``dielectric catastrophe'', taking into consideration significant difference between electronic states of isolated AlH3 molecule and condensed alane.

An experimental investigation of compressible three-dimensional boundary layer flow in annular diffusers

NASA Technical Reports Server (NTRS)

Om, Deepak; Childs, Morris E.

1987-01-01

An experimental study is described in which detailed wall pressure measurements have been obtained for compressible three-dimensional unseparated boundary layer flow in annular diffusers with and without normal shock waves. Detailed mean flow-field data were also obtained for the diffuser flow without a shock wave. Two diffuser flows with shock waves were investigated. In one case, the normal shock existed over the complete annulus whereas in the second case, the shock existed over a part of the annulus. The data obtained can be used to validate computational codes for predicting such flow fields. The details of the flow field without the shock wave show flow reversal in the circumferential direction on both inner and outer surfaces. However, there is a lag in the flow reversal between the inner nad the outer surfaces. This is an interesting feature of this flow and should be a good test for the computational codes.

Frequency shift measurement in shock-compressed materials

DOEpatents

Moore, D.S.; Schmidt, S.C.

1984-02-21

A method is disclosed for determining molecular vibrational frequencies in shock-compressed transparent materials. A single laser beam pulse is directed into a sample material while the material is shock-compressed from a direction opposite that of the incident laser beam. A Stokes beam produced by stimulated Raman scattering is emitted back along the path of the incident laser beam, that is, in the opposite direction to that of the incident laser beam. The Stokes beam is separated from the incident beam and its frequency measured. The difference in frequency between the Stokes beam and the incident beam is representative of the characteristic frequency of the Raman active mode of the sample. Both the incident beam and the Stokes beam pass perpendicularly through the stock front advancing through the sample, thereby minimizing adverse effects of refraction.

Enhanced densification under shock compression in porous silicon

NASA Astrophysics Data System (ADS)

Lane, J. Matthew D.; Thompson, Aidan P.; Vogler, Tracy J.

2014-10-01

Under shock compression, most porous materials exhibit lower densities for a given pressure than that of a full-dense sample of the same material. However, some porous materials exhibit an anomalous, or enhanced, densification under shock compression. We demonstrate a molecular mechanism that drives this behavior. We also present evidence from atomistic simulation that silicon belongs to this anomalous class of materials. Atomistic simulations indicate that local shear strain in the neighborhood of collapsing pores nucleates a local solid-solid phase transformation even when bulk pressures are below the thermodynamic phase transformation pressure. This metastable, local, and partial, solid-solid phase transformation, which accounts for the enhanced densification in silicon, is driven by the local stress state near the void, not equilibrium thermodynamics. This mechanism may also explain the phenomenon in other covalently bonded materials.

An oscillation free shock-capturing method for compressible van der Waals supercritical fluid flows

DOE PAGES

Pantano, C.; Saurel, R.; Schmitt, T.

2017-02-01

Numerical solutions of the Euler equations using real gas equations of state (EOS) often exhibit serious inaccuracies. The focus here is the van der Waals EOS and its variants (often used in supercritical fluid computations). The problems are not related to a lack of convexity of the EOS since the EOS are considered in their domain of convexity at any mesh point and at any time. The difficulties appear as soon as a density discontinuity is present with the rest of the fluid in mechanical equilibrium and typically result in spurious pressure and velocity oscillations. This is reminiscent of well-knownmore » pressure oscillations occurring with ideal gas mixtures when a mass fraction discontinuity is present, which can be interpreted as a discontinuity in the EOS parameters. We are concerned with pressure oscillations that appear just for a single fluid each time a density discontinuity is present. As a result, the combination of density in a nonlinear fashion in the EOS with diffusion by the numerical method results in violation of mechanical equilibrium conditions which are not easy to eliminate, even under grid refinement.« less

An oscillation free shock-capturing method for compressible van der Waals supercritical fluid flows

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

Pantano, C.; Saurel, R.; Schmitt, T.

Numerical solutions of the Euler equations using real gas equations of state (EOS) often exhibit serious inaccuracies. The focus here is the van der Waals EOS and its variants (often used in supercritical fluid computations). The problems are not related to a lack of convexity of the EOS since the EOS are considered in their domain of convexity at any mesh point and at any time. The difficulties appear as soon as a density discontinuity is present with the rest of the fluid in mechanical equilibrium and typically result in spurious pressure and velocity oscillations. This is reminiscent of well-knownmore » pressure oscillations occurring with ideal gas mixtures when a mass fraction discontinuity is present, which can be interpreted as a discontinuity in the EOS parameters. We are concerned with pressure oscillations that appear just for a single fluid each time a density discontinuity is present. As a result, the combination of density in a nonlinear fashion in the EOS with diffusion by the numerical method results in violation of mechanical equilibrium conditions which are not easy to eliminate, even under grid refinement.« less

Shock compression and release of a-axis magnesium single crystals: Anisotropy and time dependent inelastic response

DOE PAGES

Renganathan, P.; Winey, J. M.; Gupta, Y. M.

2017-01-19

Here, to gain insight into inelastic deformation mechanisms for shocked hexagonal close-packed (hcp) metals, particularly the role of crystal anisotropy, magnesium (Mg) single crystals were subjected to shock compression and release along the a-axis to 3.0 and 4.8 GPa elastic impact stresses. Wave profiles measured at several thicknesses, using laser interferometry, show a sharply peaked elastic wave followed by the plastic wave. Additionally, a smooth and featureless release wave is observed following peak compression. When compared to wave profiles measured previously for c-axis Mg, the elastic wave amplitudes for a-axis Mg are lower for the same propagation distance, and less attenuation of elastic wave amplitude is observed for a given peak stress. The featureless release wave for a-axis Mg is in marked contrast to the structured features observed for c-axis unloading. Numerical simulations, using a time-dependent anisotropic modeling framework, showed that the wave profiles calculated using prismatic slip or (10more » $$\\bar{1}$$2) twinning, individually, do not match the measured compression profiles for a-axis Mg. However, a combination of slip and twinning provides a good overall match to the measured compression profiles. In contrast to compression,prismatic slip alone provides a reasonable match to the measured release wave profiles; (10$$\\bar{1}$$2) twinning due to its uni-directionality is not activated during release. The experimental results and wave profile simulations for a-axis Mg presented here are quite different from the previously published c-axis results, demonstrating the important role of crystal anisotropy on the time-dependent inelastic deformation of Mg single crystals under shock compression and release.« less

Shock compression and release of a-axis magnesium single crystals: Anisotropy and time dependent inelastic response

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

Renganathan, P.; Winey, J. M.; Gupta, Y. M.

Here, to gain insight into inelastic deformation mechanisms for shocked hexagonal close-packed (hcp) metals, particularly the role of crystal anisotropy, magnesium (Mg) single crystals were subjected to shock compression and release along the a-axis to 3.0 and 4.8 GPa elastic impact stresses. Wave profiles measured at several thicknesses, using laser interferometry, show a sharply peaked elastic wave followed by the plastic wave. Additionally, a smooth and featureless release wave is observed following peak compression. When compared to wave profiles measured previously for c-axis Mg, the elastic wave amplitudes for a-axis Mg are lower for the same propagation distance, and less attenuation of elastic wave amplitude is observed for a given peak stress. The featureless release wave for a-axis Mg is in marked contrast to the structured features observed for c-axis unloading. Numerical simulations, using a time-dependent anisotropic modeling framework, showed that the wave profiles calculated using prismatic slip or (10more » $$\\bar{1}$$2) twinning, individually, do not match the measured compression profiles for a-axis Mg. However, a combination of slip and twinning provides a good overall match to the measured compression profiles. In contrast to compression,prismatic slip alone provides a reasonable match to the measured release wave profiles; (10$$\\bar{1}$$2) twinning due to its uni-directionality is not activated during release. The experimental results and wave profile simulations for a-axis Mg presented here are quite different from the previously published c-axis results, demonstrating the important role of crystal anisotropy on the time-dependent inelastic deformation of Mg single crystals under shock compression and release.« less

Fluid overload and kidney failure in children with severe sepsis and septic shock: A cohort study.

PubMed

Naveda Romero, Omar E; Naveda Meléndez, Andrea F

2017-04-01

In children with sepsis, fluid overload as a result of an aggressive fluid replacement or excessive fluid administration may result in kidney impairment and increased mortality. Objective. To determine the association between fluid overload and the rate of kidney failure in a group of children with severe sepsis and septic shock. This was a prospective cohort study conducted in the intensive care unit of Hospital Universitario de Pediatría “Dr. Agustín Zubillaga” (Barquisimeto, Lara State, Venezuela), between March 2013 and May 2016, in children with severe sepsis or septic shock. One hundred and forty-nine patients were included in the analysis. Sepsis predominated in 59.7% of cases; patients' average age was 6.4 ± 3.3 years old, their average weight was 17.8 ± 3.6 kg, 30.2% had fluid overload, and overall mortality was 25.5%. Kidney failure occurred in 16.1% of cases. A binary logistic regression model was used to identify fluid overload (odds ratio [OR]: 1.5; 95% confidence interval [CI]: 1.2-4.9, p = 0.028) and shock for more than 2 days (OR: 1.7; 95% CI: 1.3-6.3, p = 0.039) as independent predictors of kidney failure. In addition, a significant increase in the risk of mortality among children with kidney failure and fluid overload was observed as per the Kaplan-Meier method (p= 0.019). Fluid overload and shock for more than 2 days increase the risk for kidney failure in critically ill children with severe sepsis and septic shock.

The Pneumatic Actuators As Vertical Dynamic Load Simulators On Medium Weighted Wheel Suspension Mechanism

NASA Astrophysics Data System (ADS)

Ka'ka, Simon; Himran, Syukri; Renreng, Ilyas; Sutresman, Onny

2018-02-01

Almost all of road damage can be caused by dynamic loads of vehicles that fluctuate according to the type of vehicle that passes through. This study aims to calculate the vertical dynamic load of the vehicle actually occurs on road construction by the mechanism of vehicle wheel suspension. Pneumatic cylinders driven by pressurized air directly load the spring and shock absorber installed on the wheels of the vehicle. The load fluctuations of the medium weight categorized vehicles are determined by the regulation of the amount of pressurized air that enters into the pneumatic cylinder chamber, pushing the piston and connecting rods. The displacement that occurs during compression on the spring and shock absorber, is substituted into the equation of vehicle dynamic load while taking into account the spring stiffness constant, and the fluid or damper gas coefficient. The results show that the magnitude of the displacement when the compression force works has significant influences to the amount of vertical dynamic load of the vehicle that overlies the road construction. The presence of dynamic load of vehicles that fluctuates and repeats, also affects on the reduction of road ability to receive the load. Experimental results using pneumatic actuators instead of real dynamic vehicle loads illustrate the characteristics of the relationship between work pressure and dynamic load. If the working pressure of P2 (bar) is greater, the vertical dynamic load Ft (N) that overloads the road structure is also greater. The associate graphs show that the shock absorber has a greater ability to reduce dynamic load vertically that burden the road structure when compared with the ability of screw spring.

A magnetic particle time-of-flight (MagPTOF) diagnostic for measurements of shock- and compression-bang time at the NIF (invited)

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

Rinderknecht, H. G., E-mail: hgr@mit.edu; Sio, H.; Frenje, J. A.

A magnetic particle time-of-flight (MagPTOF) diagnostic has been designed to measure shock- and compression-bang time using D{sup 3}He-fusion protons and DD-fusion neutrons, respectively, at the National Ignition Facility (NIF). This capability, in combination with shock-burn weighted areal density measurements, will significantly constrain the modeling of the implosion dynamics. This design is an upgrade to the existing particle time-of-flight (pTOF) diagnostic, which records bang times using DD or DT neutrons with an accuracy better than ±70 ps [H. G. Rinderknecht et al., Rev. Sci. Instrum. 83, 10D902 (2012)]. The inclusion of a deflecting magnet will increase D{sup 3}He-proton signal-to-background by amore » factor of 1000, allowing for the first time simultaneous measurements of shock- and compression-bang times in D{sup 3}He-filled surrogate implosions at the NIF.« less

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

Experimental evidence for superionic water ice using shock compression

NASA Astrophysics Data System (ADS)

Millot, Marius; Hamel, Sebastien; Rygg, J. Ryan; Celliers, Peter M.; Collins, Gilbert W.; Coppari, Federica; Fratanduono, Dayne E.; Jeanloz, Raymond; Swift, Damian C.; Eggert, Jon H.

2018-03-01

In stark contrast to common ice, Ih, water ice at planetary interior conditions has been predicted to become superionic with fast-diffusing (that is, liquid-like) hydrogen ions moving within a solid lattice of oxygen. Likely to constitute a large fraction of icy giant planets, this extraordinary phase has not been observed in the laboratory. Here, we report laser-driven shock-compression experiments on water ice VII. Using time-resolved optical pyrometry and laser velocimetry measurements as well as supporting density functional theory-molecular dynamics (DFT-MD) simulations, we document the shock equation of state of H2O to unprecedented extreme conditions and unravel thermodynamic signatures showing that ice melts near 5,000 K at 190 GPa. Optical reflectivity and absorption measurements also demonstrate the low electronic conductivity of ice, which, combined with previous measurements of the total electrical conductivity under reverberating shock compression, provides experimental evidence for superionic conduction in water ice at planetary interior conditions, verifying a 30-year-old prediction.

Universal penetration test apparatus with fluid penetration sensor

DOEpatents

Johnson, P.W.; Stampfer, J.F.; Bradley, O.D.

1999-02-02

A universal penetration test apparatus is described for measuring resistance of a material to a challenge fluid. The apparatus includes a pad saturated with the challenge fluid. The apparatus includes a compression assembly for compressing the material between the pad and a compression member. The apparatus also includes a sensor mechanism for automatically detecting when the challenge fluid penetrates the material. 23 figs.

Experimental Study of Shock Generated Compressible Vortex Ring

NASA Astrophysics Data System (ADS)

Das, Debopam; Arakeri, Jaywant H.; Krothapalli, Anjaneyulu

2000-11-01

Formation of a compressible vortex ring and generation of sound associated with it is studied experimentally. Impulse of a shock wave is used to generate a vortex ring from the open end of a shock-tube. Vortex ring formation process has been studied in details using particle image Velocimetry (PIV). As the shock wave exits the tube it diffracts and expands. A circular vortex sheet forms at the edge and rolls up into a vortex ring. Far field microphone measurement shows that the acoustic pressure consists of a spike due to shock wave followed by a low frequency pressure wave of decaying nature, superimposed with high frequency pressure wave. Acoustic waves consist of waves due to expansion, waves formed in the tube during diaphragm breakage and waves associated with the vortex ring and shear-layer vortices. Unsteady evolution of the vortex ring and shear-layer vortices in the jet behind the ring is studied by measuring the velocity field using PIV. Corresponding vorticity field, circulation around the vortex core and growth rate of the vortex core is calculated from the measured velocity field. The velocity field in a compressible vortex ring differs from that of an incompressible ring due to the contribution from both shock and vortex ring.

Laser-excited optical emission response of CdTe quantum dot/polymer nanocomposite under shock compression

NASA Astrophysics Data System (ADS)

Xiao, Pan; Kang, Zhitao; Bansihev, Alexandr A.; Breidenich, Jennifer; Scripka, David A.; Christensen, James M.; Summers, Christopher J.; Dlott, Dana D.; Thadhani, Naresh N.; Zhou, Min

2016-01-01

Laser-driven shock compression experiments and corresponding finite element method simulations are carried out to investigate the blueshift in the optical emission spectra under continuous laser excitation of a dilute composite consisting of 0.15% CdTe quantum dots by weight embedded in polyvinyl alcohol polymer. This material is a potential candidate for use as internal stress sensors. The analyses focus on the time histories of the wavelength blue-shift for shock loading with pressures up to 7.3 GPa. The combined measurements and calculations allow a relation between the wavelength blueshift and pressure for the loading conditions to be extracted. It is found that the blueshift first increases with pressure to a maximum and subsequently decreases with pressure. This trend is different from the monotonic increase of blueshift with pressure observed under conditions of quasistatic hydrostatic compression. Additionally, the blueshift in the shock experiments is much smaller than that in hydrostatic experiments at the same pressure levels. The differences in responses are attributed to the different stress states achieved in the shock and hydrostatic experiments and the time dependence of the mechanical response of the polymer in the composite. The findings offer a potential guide for the design and development of materials for internal stress sensors for shock conditions.

An added-mass partition algorithm for fluid–structure interactions of compressible fluids and nonlinear solids

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

Banks, J.W., E-mail: banksj3@rpi.edu; Henshaw, W.D., E-mail: henshw@rpi.edu; Kapila, A.K., E-mail: kapila@rpi.edu

We describe an added-mass partitioned (AMP) algorithm for solving fluid–structure interaction (FSI) problems involving inviscid compressible fluids interacting with nonlinear solids that undergo large rotations and displacements. The computational approach is a mixed Eulerian–Lagrangian scheme that makes use of deforming composite grids (DCG) to treat large changes in the geometry in an accurate, flexible, and robust manner. The current work extends the AMP algorithm developed in Banks et al. [1] for linearly elasticity to the case of nonlinear solids. To ensure stability for the case of light solids, the new AMP algorithm embeds an approximate solution of a nonlinear fluid–solidmore » Riemann (FSR) problem into the interface treatment. The solution to the FSR problem is derived and shown to be of a similar form to that derived for linear solids: the state on the interface being fundamentally an impedance-weighted average of the fluid and solid states. Numerical simulations demonstrate that the AMP algorithm is stable even for light solids when added-mass effects are large. The accuracy and stability of the AMP scheme is verified by comparison to an exact solution using the method of analytical solutions and to a semi-analytical solution that is obtained for a rotating solid disk immersed in a fluid. The scheme is applied to the simulation of a planar shock impacting a light elliptical-shaped solid, and comparisons are made between solutions of the FSI problem for a neo-Hookean solid, a linearly elastic solid, and a rigid solid. The ability of the approach to handle large deformations is demonstrated for a problem of a high-speed flow past a light, thin, and flexible solid beam.« less

Two-fluid dusty shocks: simple benchmarking problems and applications to protoplanetary discs

NASA Astrophysics Data System (ADS)

Lehmann, Andrew; Wardle, Mark

2018-05-01

The key role that dust plays in the interstellar medium has motivated the development of numerical codes designed to study the coupled evolution of dust and gas in systems such as turbulent molecular clouds and protoplanetary discs. Drift between dust and gas has proven to be important as well as numerically challenging. We provide simple benchmarking problems for dusty gas codes by numerically solving the two-fluid dust-gas equations for steady, plane-parallel shock waves. The two distinct shock solutions to these equations allow a numerical code to test different forms of drag between the two fluids, the strength of that drag and the dust to gas ratio. We also provide an astrophysical application of J-type dust-gas shocks to studying the structure of accretion shocks on to protoplanetary discs. We find that two-fluid effects are most important for grains larger than 1 μm, and that the peak dust temperature within an accretion shock provides a signature of the dust-to-gas ratio of the infalling material.

New experimental platform to study high density laser-compressed matter

DOE PAGES

Doppner, T.; LePape, S.; Ma, T.; ...

2014-09-26

We have developed a new experimental platform at the Linac Coherent Light Source (LCLS) which combines simultaneous angularly and spectrally resolved x-ray scatteringmeasurements. This technique offers a new insights on the structural and thermodynamic properties of warm dense matter. The < 50 fs temporal duration of the x-ray pulse provides near instantaneous snapshots of the dynamics of the compression. We present a proof of principle experiment for this platform to characterize a shock-compressed plastic foil. We observe the disappearance of the plastic semi-crystal structure and the formation of a compressed liquid ion-ion correlation peak. As a result, the plasma parametersmore » of shock-compressed plastic can be measured as well, but requires an averaging over a few tens of shots.« less

Shock-wave propagation and reflection in semicrystalline polyethylene: A molecular-level investigation

NASA Astrophysics Data System (ADS)

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

2017-09-01

Semicrystalline polyethylene (PE) is attractive for a variety of mechanically demanding applications, where shock compression can occur. Although often highly crystalline, PE invariably contains nanoscale amorphous domains that influence shock propagation. Our objective in this work is to study the effects of such domains. To this end, we adopt a novel approach wherein we parametrize a simple continuum-level theory based on the shock impedance from molecular dynamics (MD) simulations. Using this theory, we predict how crystalline/amorphous interfaces attenuate shocks via energy reflection due to the impedance mismatch between the phases. The theory predicts that these interfaces attenuate weak shocks more effectively than strong shocks. We compare the theory to explicit nonequilibrium MD simulations of compressive shocks in semicrystalline PE containing nanometer-scale amorphous regions of varying size, where we analyze the pressure response and reflection of energy. The theory and simulations show good agreement for strong shocks (≥1.0 km /s ), but for weak shocks (<1.0 km /s ) the simulations show enhanced energy reflection relative to the continuum predictions. Furthermore, the simulations show an effect not captured by the continuum theory: the size of amorphous regions is important. The theory assumes a sharp (discontinuous) interface between two bulk phases and a sharp change in thermodynamic and hydrodynamic quantities at the shock front. However, the simulations show that when amorphous domains are narrow—with widths comparable to the shock front—reflection is reduced compared to the predictions. We identify several nanoscale mechanisms that reduce the impedance mismatch, and thus reduce reflection, at thin amorphous domains. First, the two-wave elastic-plastic structure of shocks in crystalline PE allows the faster-moving elastic precursor wave to compress small amorphous domains before the plastic wave arrives. Second, confinement between stiff, ordered crystalline domains increases the stiffness and chain ordering in small amorphous regions. Moreover, in terms of stiffness the interfaces are similar in width to the shock front, which may contribute to the underprediction of the theory for weak shocks, where the shock front is widest. We conclude by discussing the significance of these results, namely, how they can be applied to tune shock attenuation for particular applications.

Internal computational fluid mechanics on supercomputers for aerospace propulsion systems

NASA Technical Reports Server (NTRS)

Andersen, Bernhard H.; Benson, Thomas J.

1987-01-01

The accurate calculation of three-dimensional internal flowfields for application towards aerospace propulsion systems requires computational resources available only on supercomputers. A survey is presented of three-dimensional calculations of hypersonic, transonic, and subsonic internal flowfields conducted at the Lewis Research Center. A steady state Parabolized Navier-Stokes (PNS) solution of flow in a Mach 5.0, mixed compression inlet, a Navier-Stokes solution of flow in the vicinity of a terminal shock, and a PNS solution of flow in a diffusing S-bend with vortex generators are presented and discussed. All of these calculations were performed on either the NAS Cray-2 or the Lewis Research Center Cray XMP.

Factorizable Schemes for the Equations of Fluid Flow

NASA Technical Reports Server (NTRS)

Sidilkover, David

1999-01-01

We present an upwind high-resolution factorizable (UHF) discrete scheme for the compressible Euler equations that allows to distinguish between full-potential and advection factors at the discrete level. The scheme approximates equations in their general conservative form and is related to the family of genuinely multidimensional upwind schemes developed previously and demonstrated to have good shock-capturing capabilities. A unique property of this scheme is that in addition to the aforementioned features it is also factorizable, i.e., it allows to distinguish between full-potential and advection factors at the discrete level. The latter property facilitates the construction of optimally efficient multigrid solvers. This is done through a relaxation procedure that utilizes the factorizability property.

Shock-induced bubble collapse in a vessel: Implications for vascular injury in shockwave lithotripsy

NASA Astrophysics Data System (ADS)

Coralic, Vedran; Colonius, Tim

2014-11-01

In shockwave lithotripsy, shocks are repeatedly focused on kidney stones so to break them. The process leads to cavitation in tissue, which leads to hemorrhage. We hypothesize that shock-induced collapse (SIC) of preexisting bubbles is a potential mechanism for vascular injury. We study it numerically with an idealized problem consisting of the three-dimensional SIC of an air bubble immersed in a cylindrical water column embedded in gelatin. The gelatin is a tissue simulant and can be treated as a fluid due to fast time scales and small spatial scales of collapse. We thus model the problem as a compressible multicomponent flow and simulate it with a shock- and interface-capturing numerical method. The method is high-order, conservative and non-oscillatory. Fifth-order WENO is used for spatial reconstruction and an HLLC Riemann solver upwinds the fluxes. A third-order TVD-RK scheme evolves the solution. We evaluate the potential for injury in SIC for a range of pressures, bubble and vessel sizes, and tissue properties. We assess the potential for injury by comparing the finite strains in tissue, obtained by particle tracking, to ultimate strains from experiments. We conclude that SIC may contribute to vascular rupture and discuss the smallest bubble sizes needed for injury. This research was supported by NIH Grant No. 2PO1DK043881 and utilized XSEDE, which is supported by NSF Grant No. OCI-1053575.

Shock Dynamics for particle-laden thin film

NASA Astrophysics Data System (ADS)

Wang, Li; Bertozzi, Andrea

2013-11-01

We study the shock dynamics for a recently proposed system of conservation laws (Murisic et al. [J. Fluid Mech. 2013]) describing gravity-driven thin film flow of a suspension of particles down an incline. When the particle concentration is above a critical value, singular shock solutions can occur. We analyze the Hugoniot topology associated with the Riemann problem for this system, describing in detail how the transition from a double shock to a singular shock happen. We also derive the singular shock speed based on a key observation that the particles pilling up at the maximum packing fraction near the contact line. These results are further applied to constant volume case to generate a rarefaction-singular shock solution. The particle/fluid front are shown to move linearly to the leading order with time to the one-third power as predicted by the Huppert solution for clear fluid.

Directional amorphization of boron carbide subjected to laser shock compression

PubMed Central

Zhao, Shiteng; Kad, Bimal; Remington, Bruce A.; LaSalvia, Jerry C.; Wehrenberg, Christopher E.; Behler, Kristopher D.; Meyers, Marc A.

2016-01-01

Solid-state shock-wave propagation is strongly nonequilibrium in nature and hence rate dependent. Using high-power pulsed-laser-driven shock compression, unprecedented high strain rates can be achieved; here we report the directional amorphization in boron carbide polycrystals. At a shock pressure of 45∼50 GPa, multiple planar faults, slightly deviated from maximum shear direction, occur a few hundred nanometers below the shock surface. High-resolution transmission electron microscopy reveals that these planar faults are precursors of directional amorphization. It is proposed that the shear stresses cause the amorphization and that pressure assists the process by ensuring the integrity of the specimen. Thermal energy conversion calculations including heat transfer suggest that amorphization is a solid-state process. Such a phenomenon has significant effect on the ballistic performance of B4C. PMID:27733513

Structures and properties of materials recovered from high shock pressures

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

Nellis, W.J.

1994-03-01

Shock compression produces high dynamic pressures, densities, temperatures, and their quench rates. Because of these extreme conditions, shock compression produces materials with novel crystal structures, microstructures, and physical properties. Using a 6.5-m-long two-stage gun, we perform experiments with specimens up to 10 mm in diameter and 0.001--1 mm thick. For example, oriented disks of melt-textured superconducting YBa{sub 2}Cu{sub 3}O{sub 7} were shocked to 7 GPa without macroscopic fracture. Lattice defects are deposited in the crystal, which improve magnetic hysteresis at {approximately}1 kOe. A computer code has been developed to simulate shock compaction of 100 powder particles. Computations will be comparedmore » with experiments with 15--20 {mu}m Cu powders. The method is applicable to other powders and dynamic conditions.« less

Directional amorphization of boron carbide subjected to laser shock compression

DOE PAGES

Zhao, Shiteng; Kad, Bimal; Remington, Bruce A.; ...

2016-10-12

Solid-state shock-wave propagation is strongly nonequilibrium in nature and hence rate dependent. When using high-power pulsed-laser-driven shock compression, an unprecedented high strain rates can be achieved; we report the directional amorphization in boron carbide polycrystals. At a shock pressure of 45~50 GPa, multiple planar faults, slightly deviated from maximum shear direction, occur a few hundred nanometers below the shock surface. High-resolution transmission electron microscopy reveals that these planar faults are precursors of directional amorphization. We also propose that the shear stresses cause the amorphization and that pressure assists the process by ensuring the integrity of the specimen. Thermal energy conversionmore » calculations including heat transfer suggest that amorphization is a solid-state process. Such a phenomenon has significant effect on the ballistic performance of B 4C.« less

Experiments on a Miniature Hypervelocity Shock Tube

NASA Astrophysics Data System (ADS)

Tasker, Douglas; Johnson, Carl; Murphy, Michael; Lieber, Mark; MIMS Team

2013-06-01

A miniature explosively-driven shock tube, based on the Voitenko compressor design, has been designed to produce shock speeds in light gases in excess of 80 km/s. Voitenko compressors over 1 meter in diameter have been reported but here experiments on miniature shock tubes with ~1-mm bore diameters are described. In this design a 12-mm diameter explosive pellet drives a metal plate into a hemispherical gas compression chamber. Downstream from the piston a mica diaphragm separates the gas from an evacuated shock tube which is confined by a massive polymethylmethacrylate (PMMA) block. The diaphragm eventually ruptures under the applied pressure loading and the compressed gases escape into the evacuated shock tube at hyper velocities. The progress of gas shocks in the tube and bow shocks in the PMMA are monitored with an ultra-high-speed imaging system, the Shock Wave Image Framing Technique (SWIFT). The resulting time-resolved images yield two-dimensional visualizations of shock geometry and progression. By measuring both the gas and bow shocks, accurate and unequivocal measurements of shock position history are obtained. The experimental results were compared with those of hydrocode modeling to optimize the design. The first experiments were suboptimum in that the velocities were ~16 km/s. Progress with these experiments will be reported.

Smoothed Particle Hydrodynamics Simulations of Ultrarelativistic Shocks with Artificial Viscosity

NASA Astrophysics Data System (ADS)

Siegler, S.; Riffert, H.

2000-03-01

We present a fully Lagrangian conservation form of the general relativistic hydrodynamic equations for perfect fluids with artificial viscosity in a given arbitrary background spacetime. This conservation formulation is achieved by choosing suitable Lagrangian time evolution variables, from which the generic fluid variables of rest-mass density, 3-velocity, and thermodynamic pressure have to be determined. We present the corresponding equations for an ideal gas and show the existence and uniqueness of the solution. On the basis of the Lagrangian formulation we have developed a three-dimensional general relativistic smoothed particle hydrodynamics (SPH) code using the standard SPH formalism as known from nonrelativistic fluid dynamics. One-dimensional simulations of a shock tube and a wall shock are presented together with a two-dimensional test calculation of an inclined shock tube. With our method we can model ultrarelativistic fluid flows including shocks with Lorentz factors of even 1000.

Molecular systems under shock compression into the dense plasma regime: carbon dioxide and hydrocarbon polymers

NASA Astrophysics Data System (ADS)

Mattsson, Thomas R.; Cochrane, Kyle R.; Root, Seth; Carpenter, John H.

2013-10-01

Density Functional Theory (DFT) has proven remarkably accurate in predicting properties of matter under shock compression into the dense plasma regime. Materials where chemistry plays a role are of interest for many applications, including planetary science and inertial confinement fusion (ICF). As examples of systems where chemical reactions are important, and demonstration of the high fidelity possible for these both structurally and chemically complex systems, we will discuss shock- and re-shock of liquid carbon dioxide (CO2) in the range 100 to 800 GPa and shock compression of hydrocarbon polymers, including GDP (glow discharge polymer) which is used as an ablator in laser ICF experiments. Experimental results from Sandia's Z machine validate the DFT simulations at extreme conditions and the combination of experiment and DFT provide reliable data for evaluating existing and constructing future wide-range equations of state models for molecular compounds. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Company, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

Factors affecting the thermal shock behavior of yttria stabilized hafnia based graphite and tungsten composites.

NASA Technical Reports Server (NTRS)

Lineback, L. D.; Manning, C. R.

1971-01-01

Hafnia-based composites containing either graphite or tungsten were investigated as rocket nozzle throat inserts in solid propellant rocket engines. The thermal shock resistance of these materials is considered in terms of macroscopic thermal conductivity, thermal expansion, modulus of elasticity, and compressive fracture stress. The effect of degree of hafnia stabilization, density, and graphite or tungsten content upon these parameters is discussed. The variation of the ratio of elastic modulus to compressive fracture stress with density and its effect upon thermal shock resistance of these materials are discussed in detail.

The size effects upon shock plastic compression of nanocrystals

NASA Astrophysics Data System (ADS)

Malygin, G. A.; Klyavin, O. V.

2017-10-01

For the first time a theoretical analysis of scale effects upon the shock plastic compression of nanocrystals is implemented in the context of a dislocation kinetic approach based on the equations and relationships of dislocation kinetics. The yield point of crystals τy is established as a quantitative function of their cross-section size D and the rate of shock deformation as τy ɛ2/3 D. This dependence is valid in the case of elastic stress relaxation on account of emission of dislocations from single-pole Frank-Read sources near the crystal surface.

Professor Thomas J. Ahrens and Shock Wave Physics in Russia

NASA Astrophysics Data System (ADS)

Fortov, Vladimir E.; Kanel, Gennady I.

2011-06-01

Since his earlier works on the equations of state and dynamic mechanical properties of rocks and other materials Prof. T.J. Ahrens furnished large influence on development of the shock wave physics in Russia. He always demonstrates a choice of excellent problems and a level of productivity in the field of shock compression science which is unparalleled. In recognition of his great contribution into science and international scientific collaboration Prof. Ahrens has been elected in Russian Academy of Sciences as its foreign member. In the presentation, emphasis will be done on the Comet Shoemaker-Levy project in which we had fruitful informal collaboration, on the problem of wide-range equations of state, and on stress relaxation at shock compression of solids.

First results of radiation-driven, layered deuterium-tritium implosions with a 3-shock adiabat-shaped drive at the National Ignition Facility

DOE PAGES

Smalyuk, V. A.; Robey, H. F.; Döppner, T.; ...

2015-08-27

Radiation-driven, layered deuterium-tritium plastic capsule implosions were carried out using a new, 3-shock “adiabat-shaped” drive on the National Ignition Facility. The purpose of adiabat shaping is to use a stronger first shock, reducing hydrodynamic instability growth in the ablator. The shock can decay before reaching the deuterium-tritium fuel leaving it on a low adiabat and allowing higher fuel compression. The fuel areal density was improved by ~25% with this new drive compared to similar “high-foot” implosions, while neutron yield was improved by more than 4 times, compared to “low-foot” implosions driven at the same compression and implosion velocity.

Physics of Shock Compression and Release: NEMD Simulations of Tantalum and Silicon

NASA Astrophysics Data System (ADS)

Hahn, Eric; Meyers, Marc; Zhao, Shiteng; Remington, Bruce; Bringa, Eduardo; Germann, Tim; Ravelo, Ramon; Hammerberg, James

2015-06-01

Shock compression and release allow us to evaluate physical deformation and damage mechanisms occurring in extreme environments. SPaSM and LAMMPS molecular dynamics codes were employed to simulate single and polycrystalline tantalum and silicon at strain rates above 108 s-1. Visualization and analysis was accomplished using OVITO, Crystal Analysis Tool, and a redesigned orientation imaging function implemented into SPaSM. A comparison between interatomic potentials for both Si and Ta (as pertaining to shock conditions) is conducted and the influence on phase transformation and plastic relaxation is discussed. Partial dislocations, shear induced disordering, and metastable phase changes are observed in compressed silicon. For tantalum, the role of grain boundary and twin intersections are evaluated for their role in ductile spallation. Finally, the temperature dependent response of both Ta and Si is investigated.

Floating shock fitting via Lagrangian adaptive meshes

NASA Technical Reports Server (NTRS)

Vanrosendale, John

1995-01-01

In recent work we have formulated a new approach to compressible flow simulation, combining the advantages of shock-fitting and shock-capturing. Using a cell-centered on Roe scheme discretization on unstructured meshes, we warp the mesh while marching to steady state, so that mesh edges align with shocks and other discontinuities. This new algorithm, the Shock-fitting Lagrangian Adaptive Method (SLAM), is, in effect, a reliable shock-capturing algorithm which yields shock-fitted accuracy at convergence.

Measurements of ionic structure in shock compressed lithium hydride from ultrafast x-ray Thomson scattering.

PubMed

Kritcher, A L; Neumayer, P; Brown, C R D; Davis, P; Döppner, T; Falcone, R W; Gericke, D O; Gregori, G; Holst, B; Landen, O L; Lee, H J; Morse, E C; Pelka, A; Redmer, R; Roth, M; Vorberger, J; Wünsch, K; Glenzer, S H

2009-12-11

We present the first ultrafast temporally, spectrally, and angularly resolved x-ray scattering measurements from shock-compressed matter. The experimental spectra yield the absolute elastic and inelastic scattering intensities from the measured density of free electrons. Laser-compressed lithium-hydride samples are well characterized by inelastic Compton and plasmon scattering of a K-alpha x-ray probe providing independent measurements of temperature and density. The data show excellent agreement with the total intensity and structure when using the two-species form factor and accounting for the screening of ion-ion interactions.

Experimental observation of the shift and width of the aluminium K absorption edge in laser shock-compressed plasmas

NASA Astrophysics Data System (ADS)

Hall, T. A.; Al-Kuzee, J.; Benuzzi, A.; Koenig, M.; Krishnan, J.; Grandjouan, N.; Batani, D.; Bossi, S.; Nicolella, S.

1998-03-01

Experimental measurements of the shift and width of the aluminium K-absorption edge in laser shock-compressed plasma is presented. The spectrometer used in these experiments allows an accurate wavelength calibration and fiduciary and hence provides precise measurements of both the shift and the width of the absorption edge. Results have been obtained for compressions up to approximately ×2 and temperatures up to about 1.5 eV. The values of shift and width are compared with a new model with which there is very good agreement.

Statistical modeling of compressible turbulence - Shock-wave/turbulence interactions and buoyancy effects

NASA Astrophysics Data System (ADS)

Yoshizawa, Akira

1991-12-01

A mass-weighted mean compressible turbulence model is presented with the aid of the results from a two-scale DIA. This model aims at dealing with two typical aspects in compressible flows: the interaction of a shock wave with turbulence in high-speed flows and strong buoyancy effects in thermally-driven flows as in stellar convection and conflagration. The former is taken into account through the effect of turbulent dilatation that is related to the density fluctuation and leads to the enhanced kinetic-energy dissipation. The latter is incorporated through the interaction between the gravitational and density-fluctuation effects.

Fluid therapy for septic shock resuscitation: which fluid should be used?

PubMed

Corrêa, Thiago Domingos; Rocha, Leonardo Lima; Pessoa, Camila Menezes Souza; Silva, Eliézer; de Assuncao, Murillo Santucci Cesar

2015-01-01

Early resuscitation of septic shock patients reduces the sepsis-related morbidity and mortality. The main goals of septic shock resuscitation include volemic expansion, maintenance of adequate tissue perfusion and oxygen delivery, guided by central venous pressure, mean arterial pressure, mixed or central venous oxygen saturation and arterial lactate levels. An aggressive fluid resuscitation, possibly in association with vasopressors, inotropes and red blood cell concentrate transfusion may be necessary to achieve those hemodynamic goals. Nonetheless, even though fluid administration is one of the most common interventions offered to critically ill patients, the most appropriate type of fluid to be used remains controversial. According to recently published clinical trials, crystalloid solutions seem to be the most appropriate type of fluids for initial resuscitation of septic shock patients. Balanced crystalloids have theoretical advantages over the classic solutions, but there is not enough evidence to indicate it as first-line treatment. Additionally, when large amounts of fluids are necessary to restore the hemodynamic stability, albumin solutions may be a safe and effective alternative. Hydroxyethyl starches solutions must be avoided in septic patients due to the increased risk of acute renal failure, increased need for renal replacement therapy and increased mortality. Our objective was to present a narrative review of the literature regarding the major types of fluids and their main drawbacks in the initial resuscitation of the septic shock patients.

Adiabatic Compression Sensitivity of Liquid Fuels and Monopropellants

NASA Technical Reports Server (NTRS)

Ismail, Ismail M. K.; Hawkins, Tom W.

2000-01-01

Liquid rocket propellants can be sensitive to rapid compression. Such liquids may undergo decomposition and their handling may be accompanied with risk. Decomposition produces small gas bubbles in the liquid, which upon rapid compression may cause catastrophic explosions. The rapid compression can result from mechanical shocks applied on the tank containing the liquid or from rapid closure of the valves installed on the lines. It is desirable to determine the conditions that may promote explosive reactions. At Air Force Research Laboratory (AFRL), we constructed an apparatus and established a safe procedure for estimating the sensitivity of propellant materials towards mechanical shocks (Adiabatic Compression Tester). A sample is placed on a stainless steel U-tube, held isothermally at a temperature between 20 and 150 C then exposed to an abrupt mechanical shock of nitrogen gas at a pressure between 6.9 and 20.7 MPa (1000 to 3000 psi). The apparatus is computer interfaced and is driven with LABTECH NOTEBOOK-pro (registered) Software. In this presentation, the design of the apparatus is shown, the operating procedure is outlined, and the safety issues are addressed. The results obtained on different energetic materials are presented.

Laser Shock Compression Studies of Phase Changes in Ce3 Al Metallic Glass

NASA Astrophysics Data System (ADS)

Bryant, Alex; Wehrenberg, Christopher; Alamgir, Faisal; Remington, Bruce; Thadhani, Naresh

2017-06-01

Laser shock-compression of Ce3 Al metallic glass (MG) was performed to probe pressure-induced phase transitions. Ce3 Al MG has been previously shown to crystallize into a single crystal FCC phase during static compression at 25 GPa. In the present work, experiments were performed using the 3J Nd:YAG pulse laser at Georgia Tech and the high energy laser at the OMEGA facility. Characterization of shock compressed samples recovered from the OMEGA laser experiments were performed using XRD and PDF measurements at the NSLS-2 synchrotron at Brookhaven National Lab. The results showed evidence of a permanent polyamorphous phase change at pressures > 10 GPa and crystallization at pressures > 75 GPa. Particle velocities were measured using VISAR in experiments performed at Georgia Tech and simulated using Hyades and Abaqus to create an empirical equation of state and correlate with results obtained from XRD and PDF characterization. The results attained to-date in terms of the evolution of the high pressure amorphous and crystalline phases and their correlations with the shock conditions will be presented. This work is supported in part by ARO Grant No. W9HNF-09-1-0403 and the National Science Foundation Graduate Research Fellowship Program awarded to Alex Bryant under Grant No. 0946809.

Shock wave-induced phase transition in RDX single crystals.

PubMed

Patterson, James E; Dreger, Zbigniew A; Gupta, Yogendra M

2007-09-20

The real-time, molecular-level response of oriented single crystals of hexahydro-1,3,5-trinitro-s-triazine (RDX) to shock compression was examined using Raman spectroscopy. Single crystals of [111], [210], or [100] orientation were shocked under stepwise loading to peak stresses from 3.0 to 5.5 GPa. Two types of measurements were performed: (i) high-resolution Raman spectroscopy to probe the material at peak stress and (ii) time-resolved Raman spectroscopy to monitor the evolution of molecular changes as the shock wave reverberated through the material. The frequency shift of the CH stretching modes under shock loading appeared to be similar for all three crystal orientations below 3.5 GPa. Significant spectral changes were observed in crystals shocked above 4.5 GPa. These changes were similar to those observed in static pressure measurements, indicating the occurrence of the alpha-gamma phase transition in shocked RDX crystals. No apparent orientation dependence in the molecular response of RDX to shock compression up to 5.5 GPa was observed. The phase transition had an incubation time of approximately 100 ns when RDX was shocked to 5.5 GPa peak stress. The observation of the alpha-gamma phase transition under shock wave loading is briefly discussed in connection with the onset of chemical decomposition in shocked RDX.

Relation Between Pore Size and the Compressibility of a Confined Fluid

PubMed Central

Gor, Gennady Y.; Siderius, Daniel W.; Rasmussen, Christopher J.; Krekelberg, William P.; Shen, Vincent K.; Bernstein, Noam

2015-01-01

When a fluid is confined to a nanopore, its thermodynamic properties differ from the properties of a bulk fluid, so measuring such properties of the confined fluid can provide information about the pore sizes. Here we report a simple relation between the pore size and isothermal compressibility of argon confined in these pores. Compressibility is calculated from the fluctuations of the number of particles in the grand canonical ensemble using two different simulation techniques: conventional grand-canonical Monte Carlo and grand-canonical ensemble transition-matrix Monte Carlo. Our results provide a theoretical framework for extracting the information on the pore sizes of fluid-saturated samples by measuring the compressibility from ultrasonic experiments. PMID:26590541

Investigating Vaporization of Silica through Laser Driven Shock Wave Experiments

NASA Astrophysics Data System (ADS)

Kraus, R. G.; Swift, D. C.; Stewart, S. T.; Smith, R.; Bolme, C. A.; Spaulding, D. K.; Hicks, D.; Eggert, J.; Collins, G.

2010-12-01

Giant impacts melt and vaporize a significant amount of the bolide and target body. However, our ability to determine how much melt or vapor a given impact creates depends strongly on our understanding of the liquid-vapor phase boundary of geologic materials. Our current knowledge of the liquid-vapor equilibrium for one of the most important minerals, SiO2, is rather limited due to the difficulty of performing experiments in this area of phase space. In this study, we investigate the liquid-vapor coexistence region by shocking quartz into a supercritical fluid state and allowing it to adiabatically expand to a state on the liquid-vapor phase boundary. Although shock compression and release has been used to study the liquid-vapor equilibrium of metals [1], few attempts have been made at studying geologic materials by this method [2]. Shock waves were produced by direct ablation of the quartz sample using the Jupiter Laser Facility of Lawrence Livermore National Laboratory. Steady shock pressures of 120-360 GPa were produced in the quartz samples: high enough to force the quartz into a supercritical fluid state. As the shock wave propagates through the sample, we measure the shock velocity using a line imaging velocity interferometer system for any reflector (VISAR) and shock temperature using a streaked optical pyrometer (SOP). When the shock wave reaches the free surface of the sample, the material adiabatically expands. Upon breakout of the shock at the free surface, the SOP records a distinct drop in radiance due to the lower temperature of the expanded material. For a subset of experiments, a LiF window is positioned downrange of the expanding silica. When the expanding silica impacts the LiF window, the velocity at the interface between the expanding silica and LiF window is measured using the VISAR. From the shock velocity measurements, we accurately determine the shocked state in the quartz. The post-shock radiance measurements are used to constrain the temperature on the liquid-vapor phase boundary (e.g., [3]) at much higher pressures than previously possible using a 2 stage gas gun [4, 5]. The density on the liquid-vapor phase boundary is constrained by comparing the velocity at the silica-LiF interface to numerical simulations that use equations of state with systematically varied liquid-vapor phase boundaries. We present the results within the context of understanding vaporization during giant impact events. [1] Brannon, R.M. and L.C. Chhabildas (1995) Int. J. Impact Engng. 17, 109-120. [2] Kurosawa, K. and S. Sugita (2010) J. Geophys. Res. in press. [3] Stewart, S.T., A. Seifter, and A.W. Obst (2008) Geophys. Res. Lett., 35, (23). [4] Lyzenga, G.A., T.J. Ahrens, and A.C. Mitchell (1983) J. Geophys. Res. , 88, (NB3), 2431-2444. [5] Boslough, M.B. (1988) J. Geophys. Res., 93, (B6), 6477-6484.

Fluid displacement from intraluminal thrombus of abdominal aortic aneurysm as a result of uniform compression.

PubMed

van Noort, Kim; Schuurmann, Richte Cl; Wermelink, Bryan; Slump, Cornelis H; Kuijpers, Karel C; de Vries, Jean-Paul Pm

2017-10-01

Objectives The results after aneurysm repair with an endovascular aneurysm sealing (EVAS) system are dependent on the stability of the aneurysm sac and particularly the intraluminal abdominal aortic thrombus (ILT). The postprocedural ILT volume is decreased compared with preprocedural ILT volume in aortic aneurysm patients treated with EVAS. We hypothesize that ILT is not stable in all patients and pressurization of the ILT may result in displacement of fluids from the ILT, no differently than serum is displaced from whole blood when it settles. To date, the mechanism and quantification of fluid displacement from ILT are unknown. Methods The study included 21 patients who underwent elective open abdominal aortic aneurysm repair. The ILT was harvested as a routine procedure during the operation. After excision of a histologic sample of the ILT specimen in four patients, ILT volume was measured and the ILT was compressed in a dedicated compression setup designed to apply uniform compression of 200 mmHg for 5 min. After compression, the volumes of the remaining thrombus and the displaced fluid were measured. Results The median (interquartile-range) of ILT volume before compression was 60 (66) mL, and a median of 5.7 (8.4) mL of fluid was displaced from the ILT after compression, resulting in a median thrombus volume decrease of 11% (10%). Fluid components can be up to 31% of the entire ILT volume. Histologic examination of four ILT specimens showed a reduction of the medial layer of the ILT after compression, which was the result of compression of fluid-containing canaliculi. Conclusions Applying pressure of 200 mmHg to abdominal aortic aneurysm ILT resulted in the displacement of fluid, with a large variation among patients. Fluid displacement may result in decrease of ILT volume during and after EVAS, which might have implications on pre-EVAS volume planning and on stability of the endobags during follow-up which may lead to migration, endoleak or both.

Neurofilaments Function as Shock Absorbers: Compression Response Arising from Disordered Proteins.

PubMed

Kornreich, Micha; Malka-Gibor, Eti; Zuker, Ben; Laser-Azogui, Adi; Beck, Roy

2016-09-30

What can cells gain by using disordered, rather than folded, proteins in the architecture of their skeleton? Disordered proteins take multiple coexisting conformations, and often contain segments which act as random-walk-shaped polymers. Using x-ray scattering we measure the compression response of disordered protein hydrogels, which are the main stress-responsive component of neuron cells. We find that at high compression their mechanics are dominated by gaslike steric and ionic repulsions. At low compression, specific attractive interactions dominate. This is demonstrated by the considerable hydrogel expansion induced by the truncation of critical short protein segments. Accordingly, the floppy disordered proteins form a weakly cross-bridged hydrogel, and act as shock absorbers that sustain large deformations without failure.

Neurofilaments Function as Shock Absorbers: Compression Response Arising from Disordered Proteins

NASA Astrophysics Data System (ADS)

Kornreich, Micha; Malka-Gibor, Eti; Zuker, Ben; Laser-Azogui, Adi; Beck, Roy

2016-09-01

What can cells gain by using disordered, rather than folded, proteins in the architecture of their skeleton? Disordered proteins take multiple coexisting conformations, and often contain segments which act as random-walk-shaped polymers. Using x-ray scattering we measure the compression response of disordered protein hydrogels, which are the main stress-responsive component of neuron cells. We find that at high compression their mechanics are dominated by gaslike steric and ionic repulsions. At low compression, specific attractive interactions dominate. This is demonstrated by the considerable hydrogel expansion induced by the truncation of critical short protein segments. Accordingly, the floppy disordered proteins form a weakly cross-bridged hydrogel, and act as shock absorbers that sustain large deformations without failure.

Laboratory studies of volcanic jets

NASA Astrophysics Data System (ADS)

Kieffer, Susan Werner; Sturtevant, Bradford

1984-09-01

The study of the fluid dynamics of violent volcanic eruptions by laboratory experiment is described, and the important fluid-dynamic processes that can be examined in laboratory models are discussed in detail. In preliminary experiments, pure gases are erupted from small reservoirs. The gases used are Freon 12 and Freon 22, two gases of high molecular weight and high density that are good analogs of heavy and particulate-laden volcanic gases; nitrogen, a moderate molecular weight, moderate density gas for which the thermodynamic properties are well known; and helium, a low molecular weight, lowdensity gas that is used as a basis for comparison with the behavior of the heavier gases and as an analog of steam, the gas that dominates many volcanic eruptions. Transient jets erupt from the reservoir into the laboratory upon rupture of a thin diaphragm at the exit of a convergent nozzle. The gas accelerates from rest in the reservoir to high velocity in the jet. Reservoir pressures and geometries are such that the fluid velocity in the jets is initially supersonic and later decays to subsonic. The measured reservoir pressure decreases as the fluid expands through repetitively reflecting rarefaction waves, but for the conditions of these experiments, a simple steady-discharge model is sufficient to explain the pressure decay and to predict the duration of the flow. Density variations in the flow field have been visualized with schlieren and shadowgraph photography. The observed structure of the jet is correlated with the measured pressure history. The starting vortex generated when the diaphragm ruptures becomes the head of the jet. Though the exit velocity is sonic, the flow head in the helium jet decelerates to about one-third of sonic velocity in the first few nozzle diameters, the nitrogen head decelerates to about three-fourths of sonic velocity, while Freon maintains nearly sonic velocity. The impulsive acceleration of reservoir fluid into the surrounding atmosphere produces a compression wave. The strength of this wave depends primarily on the sound speed of the fluid in the reservoir but also, secondarily with opposite effect, on the density: helium produces a relatively strong atmospheric shock while the Freons do not produce any optically observable wave front. Well-formed N waves are detected with a microphone far from the reservoir. Barrel shocks, Mach disks, and other familiar features of steady underexpanded supersonic jets form inside the jet almost immediately after passage of the flow head. These features are maintained until the pressure in the reservoir decays to sonic conditions. At low pressures the jets are relatively structureless. Gas-particle jets from volcanic eruptions may behave as pseudogases if particle concentrations and mass and momentum exchange between the components are sufficiently small. The sound speed of volcanic pseudogases can be as large as 1000 m s-1 or as small as a few tens of meters per second depending on the mass loading and initial temperature. Fluids of high sound speed produce stronger atmospheric shock waves than do those of low sound speed. Therefore eruption of a hot gas lightly laden with particulates should produce a stronger shock than eruption of a cooler or heavily laden fluid. An empirical expression suggests that the initial velocity of the head of supersonic volcanic jets is controlled by the sound speed and the ratio of the density of the erupting fluid to that of the atmosphere. The duration of gas or pseudogas eruptions is controlled by the sound speed of the fluid and the ratio of reservoir volume to vent area.

Incorporation of additives into polymers

DOEpatents

McCleskey, T. Mark; Yates, Matthew Z.

2003-07-29

There has been invented a method for incorporating additives into polymers comprising: (a) forming an aqueous or alcohol-based colloidal system of the polymer; (b) emulsifying the colloidal system with a compressed fluid; and (c) contacting the colloidal polymer with the additive in the presence of the compressed fluid. The colloidal polymer can be contacted with the additive by having the additive in the compressed fluid used for emulsification or by adding the additive to the colloidal system before or after emulsification with the compressed fluid. The invention process can be carried out either as a batch process or as a continuous on-line process.

Modeling the Plasma Flow in the Inner Heliosheath with a Spatially Varying Compression Ratio

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

Nicolaou, G.; Livadiotis, G.

2017-03-20

We examine a semi-analytical non-magnetic model of the termination shock location previously developed by Exarhos and Moussas. In their study, the plasma flow beyond the shock is considered incompressible and irrotational, thus the flow potential is analytically derived from the Laplace equation. Here we examine the characteristics of the downstream flow in the heliosheath in order to resolve several inconsistencies existing in the Exarhos and Moussas model. In particular, the model is modified in order to be consistent with the Rankine–Hugoniot jump conditions and the geometry of the termination shock. It is shown that a shock compression ratio varying alongmore » the latitude can lead to physically correct results. We describe the new model and present several simplified examples for a nearly spherical, strong termination shock. Under those simplifications, the upstream plasma is nearly adiabatic for large (∼100 AU) heliosheath thickness.« less

Lattice-level observation of the elastic-to-plastic relaxation process with subnanosecond resolution in shock-compressed Ta using time-resolved in situ Laue diffraction

DOE PAGES

Wehrenberg, C. E.; Comley, A. J.; Barton, N. R.; ...

2015-09-29

We report direct lattice level measurements of plastic relaxation kinetics through time-resolved, in-situ Laue diffraction of shock-compressed single-crystal [001] Ta at pressures of 27-210 GPa. For a 50 GPa shock, a range of shear strains is observed extending up to the uniaxial limit for early data points (<0.6 ns) and the average shear strain relaxes to a near steady state over ~1 ns. For 80 and 125 GPa shocks, the measured shear strains are fully relaxed already at 200 ps, consistent with rapid relaxation associated with the predicted threshold for homogeneous nucleation of dislocations occurring at shock pressure ~65 GPa.more » The relaxation rate and shear stresses are used to estimate the dislocation density and these quantities are compared to the Livermore Multiscale Strength model as well as various molecular dynamics simulations.« less

Sound velocities in shocked liquid D2 to 28 GPa

NASA Astrophysics Data System (ADS)

Holmes, N. C.; Ross, M.; Nellis, W. J.

1999-06-01

Recent measurements of shock temperatures(N. C. Holmes, W. J. Nellis, and M. Ross, Phys. Rev.) B52, 15835 (1995). and laser-driven Hugoniot measurements(L. B. Da Silva, et al.), Phys. Rev. Lett. 78, 483 (1997). of shocked liquid deuterium strongly indicate that molecular dissociation is important above 20 GPa. Since the amount of expected dissociation is small on the Hugoniot at the 30 GPa limit of conventional impact experiments, other methods must be used to test our understanding of the physics of highly compressed deuterium in this regime. We have recently performed experiments to measure the sound velocity of deuterium which test the isentropic compressibility, c^2 = (partial P/partial ρ)_S. We used the shock overtake method to measure sound velocities at several shock pressures between 10--28 GPa. These data provide support for recently developed molecular dissociation models.

Control of shock wave-boundary layer interactions by bleed in supersonic mixed compression inlets

NASA Technical Reports Server (NTRS)

Fukuda, M. K.; Hingst, W. G.; Reshotko, E.

1975-01-01

An experimental investigation was conducted to determine the effect of bleed on a shock wave-boundary layer interaction in an axisymmetric mixed-compression supersonic inlet. The inlet was designed for a free-stream Mach number of 2.50 with 60-percent supersonic internal area contraction. The experiment was conducted in the NASA Lewis Research Center 10-Foot Supersonic Wind Tunnel. The effects of bleed amount and bleed geometry on the boundary layer after a shock wave-boundary layer interaction were studied. The effect of bleed on the transformed form factor is such that the full realizable reduction is obtained by bleeding of a mass flow equal to about one-half of the incident boundary layer mass flow. More bleeding does not yield further reduction. Bleeding upstream or downstream of the shock-induced pressure rise is preferable to bleeding across the shock-induced pressure rise.

Shock-absorbing caster wheel is simple and compact

NASA Technical Reports Server (NTRS)

Kindley, R. J.

1968-01-01

Compact shock-absorbing caster wheel mitigates or absorbs shock by a compressible tire which deforms into a cavity between its inner edge and the wheel hub. A tee-shaped annular ring embedded in the tire distributes loads more uniformly throughout both wheel and tire.

Hugoniot equation of state of rock materials under shock compression

PubMed Central

Braithwaite, C. H.; Zhao, J.

2017-01-01

Two sets of shock compression tests (i.e. conventional and reverse impact) were conducted to determine the shock response of two rock materials using a plate impact facility. Embedded manganin stress gauges were used for the measurements of longitudinal stress and shock velocity. Photon Doppler velocimetry was used to capture the free surface velocity of the target. Experimental data were obtained on a fine-grained marble and a coarse-grained gabbro over a shock pressure range of approximately 1.5–12 GPa. Gabbro exhibited a linear Hugoniot equation of state (EOS) in the pressure–particle velocity (P–up) plane, while for marble a nonlinear response was observed. The EOS relations between shock velocity (US) and particle velocity (up) are linearly fitted as US = 2.62 + 3.319up and US = 5.4 85 + 1.038up for marble and gabbro, respectively. This article is part of the themed issue ‘Experimental testing and modelling of brittle materials at high strain rates’. PMID:27956506

Shocks in fragile matter

NASA Astrophysics Data System (ADS)

Vitelli, Vincenzo

2012-02-01

Non-linear sound is an extreme phenomenon typically observed in solids after violent explosions. But granular media are different. Right when they unjam, these fragile and disordered solids exhibit vanishing elastic moduli and sound speed, so that even tiny mechanical perturbations form supersonic shocks. Here, we perform simulations in which two-dimensional jammed granular packings are continuously compressed, and demonstrate that the resulting excitations are strongly nonlinear shocks, rather than linear waves. We capture the full dependence of the shock speed on pressure and compression speed by a surprisingly simple analytical model. We also treat shear shocks within a simplified viscoelastic model of nearly-isostatic random networks comprised of harmonic springs. In this case, anharmonicity does not originate locally from nonlinear interactions between particles, as in granular media; instead, it emerges from the global architecture of the network. As a result, the diverging width of the shear shocks bears a nonlinear signature of the diverging isostatic length associated with the loss of rigidity in these floppy networks.

Study of the effects of Shockwaves on Nano fluids

NASA Astrophysics Data System (ADS)

Shreekhar; Akhil, Mohan; Ram, Sai; Gopaiah, Venkata; Koundinya, Sandeep; Nagaraja, S. R.

2018-02-01

Nanofluids are fluids with nanoparticles dispersed in them. Due to the presence of Nano particles, these fluids exhibit unique properties that can used in various applications such as heat exchangers and in medical fields. However, due to agglomeration, the size of these particle increases, reducing their efficiency. In order to break the agglomeration, we are passing shockwaves in the fluid. Shockwaves theoretically carry energy which can be used to break the agglomerating particles. In this paper, silver nanoparticles were synthesized using silver nitrate. Tri sodium citrate was used as the reducing agent. Shock waves were passed to the fluid containing silver Nano particles. The changes in the Nano fluid was measured by a UV-Vis Spectrophotometer. With each shock passed, the fluid’s absorbance and wavelength peak was measured and compared with Nano fluid without shock.

National Training Course. Emergency Medical Technician. Paramedic. Instructor's Lesson Plans. Module III. Shock and Fluid Therapy.

ERIC Educational Resources Information Center

National Highway Traffic Safety Administration (DOT), Washington, DC.

This instructor's lesson plan guide on shock and fluid therapy is one of fifteen modules designed for use in the training of emergency medical technicians (paramedics). Six units of study are presented: (1) body fluids, electrolytes and their effect on the body, and the general principles of fluid and acid base balances; (2) characteristics of…

Ultrahigh Pressure Dynamic Compression

NASA Astrophysics Data System (ADS)

Duffy, T. S.

2017-12-01

Laser-based dynamic compression provides a new opportunity to study the lattice structure and other properties of geological materials to ultrahigh pressure conditions ranging from 100 - 1000 GPa (1 TPa) and beyond. Such studies have fundamental applications to understanding the Earth's core as well as the interior structure of super-Earths and giant planets. This talk will review recent dynamic compression experiments using high-powered lasers on materials including Fe-Si, MgO, and SiC. Experiments were conducted at the Omega laser (University of Rochester) and the Linac Coherent Light Source (LCLS, Stanford). At Omega, laser drives as large as 2 kJ are applied over 10 ns to samples that are 50 microns thick. At peak compression, the sample is probed with quasi-monochromatic X-rays from a laser-plasma source and diffraction is recorded on image plates. At LCLS, shock waves are driven into the sample using a 40-J laser with a 10-ns pulse. The sample is probed with X-rays form the LCLS free electron laser providing 1012 photons in a monochromatic pulse near 10 keV energy. Diffraction is recorded using pixel array detectors. By varying the delay between the laser and the x-ray beam, the sample can be probed at various times relative to the shock wave transiting the sample. By controlling the shape and duration of the incident laser pulse, either shock or ramp (shockless) loading can be produced. Ramp compression produces less heating than shock compression, allowing samples to be probed to ultrahigh pressures without melting. Results for iron alloys, oxides, and carbides provide new constraints on equations of state and phase transitions that are relevant to the interior structure of large, extrasolar terrestrial-type planets.

Mechanical Characterization of the Human Lumbar Intervertebral Disc Subjected to Impact Loading Conditions

NASA Astrophysics Data System (ADS)

Jamison, David, IV

Low back pain is a large and costly problem in the United States. Several working populations, such as miners, construction workers, forklift operators, and military personnel, have an increased risk and prevalence of low back pain compared to the general population. This is due to exposure to repeated, transient impact shocks, particularly while operating vehicles or other machinery. These shocks typically do not cause acute injury, but rather lead to pain and injury over time. The major focus in low back pain is often the intervertebral disc, due to its role as the major primary load-bearing component along the spinal column. The formation of a reliable standard for human lumbar disc exposure to repeated transient shock could potentially reduce injury risk for these working populations. The objective of this project, therefore, is to characterize the mechanical response of the lumbar intervertebral disc subjected to sub-traumatic impact loading conditions using both cadaveric and computational models, and to investigate the possible implications of this type of loading environment for low back pain. Axial, compressive impact loading events on Naval high speed boats were simulated in the laboratory and applied to human cadaveric specimen. Disc stiffness was higher and hysteresis was lower than quasi-static loading conditions. This indicates a shift in mechanical response when the disc is under impact loads and this behavior could be contributing to long-term back pain. Interstitial fluid loss and disc height changes were shown to affect disc impact mechanics in a creep study. Neutral zone increased, while energy dissipation and low-strain region stiffness decreased. This suggests that the disc has greater clinical instability during impact loading with progressive creep and fluid loss, indicating that time of day should be considered for working populations subjected to impact loads. A finite element model was developed and validated against cadaver specimen subjected to impacts in the laboratory. Analysis showed greater total von Mises stress and pore pressure in the components of the disc under transient shocks compared to static or quasi-static loading. These findings support the idea that impact shocks cause a change in mechanical response and are potentially damaging to the disc in the long term.

Compression in Working Memory and Its Relationship with Fluid Intelligence

ERIC Educational Resources Information Center

Chekaf, Mustapha; Gauvrit, Nicolas; Guida, Alessandro; Mathy, Fabien

2018-01-01

Working memory has been shown to be strongly related to fluid intelligence; however, our goal is to shed further light on the process of information compression in working memory as a determining factor of fluid intelligence. Our main hypothesis was that compression in working memory is an excellent indicator for studying the relationship between…

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.

Enhanced densification, strength and molecular mechanisms in shock compressed porous silicon

NASA Astrophysics Data System (ADS)

Lane, J. Matthew D.; Vogler, Tracy J.

2015-06-01

In most porous materials, void collapse during shock compression couples mechanical energy to thermal energy. Increased temperature drives up pressures and lowers densities in the final Hugoniot states as compared to full-density samples. Some materials, however, exhibit an anomalous enhanced densification in their Hugoniot states when porosity is introduced. We have recently shown that silicon is such a material, and demonstrated a molecular mechanism for the effect using molecular simulation. We will review results from large-scale non-equilibrium molecular dynamics (NEMD) and Hugoniotstat simulations of shock compressed porous silicon, highlighting the mechanism by which porosity produces local shear which nucleate partial phase transition and localized melting at shock pressures below typical thresholds in these materials. Further, we will characterize the stress states and strength of the material as a function of porosity from 5 to 50 percent and with various porosity microstructures. Sandia National Laboratories is a multi program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

The Absence of Fever Is Associated With Higher Mortality and Decreased Antibiotic and IV Fluid Administration in Emergency Department Patients With Suspected Septic Shock.

PubMed

Henning, Daniel J; Carey, Jeremy R; Oedorf, Kimie; Day, Danielle E; Redfield, Colby S; Huguenel, Colin J; Roberts, Jonathan C; Sanchez, Leon D; Wolfe, Richard E; Shapiro, Nathan I

2017-06-01

This study evaluates whether emergency department septic shock patients without a fever (reported or measured) receive less IV fluids, have decreased antibiotic administration, and suffer increased in-hospital mortality. This was a secondary analysis of a prospective, observational study of patients with shock. The study was conducted in an urban, academic emergency department. The original study enrolled consecutive adult (aged 18 yr or older) emergency department patients from November 11, 2012, to September 23, 2013, who met one of the following shock criteria: 1) systolic blood pressure less than 90 mm Hg after at least 1L IV fluids, 2) new vasopressor requirement, or 3) systolic blood pressure less than 90 mm Hg and IV fluids held for concern of fluid overload. The current study is limited to patients with septic shock. Patients were grouped as febrile if they had a subjective fever or a measured temperature >100.4°F documented in the emergency department; afebrile patients lacked both. Among 378 patients with septic shock, 207 of 378 (55%; 50-60%) were febrile by history or measurement. Afebrile patients had lower rates of antibiotic administration in the emergency department (81% vs 94%; p < 0.01), lower mean volumes of IV fluids (2,607 vs 3,013 mL; p < 0.01), and higher in-hospital mortality rates (33% vs 11%; p < 0.01). After adjusting for bicarbonate less than 20 mEq/L, lactate concentration, respiratory rate greater than or equal to 24 breaths/min, emergency department antibiotics, and emergency department IV fluids volume, being afebrile remained a significant predictor of in-hospital mortality (odds ratio, 4.3; 95% CI, 2.2-8.2; area under the curve = 0.83). In emergency department patients with septic shock, afebrile patients received lower rates of emergency department antibiotic administration, lower mean IV fluids volume, and suffered higher in-hospital mortality.

On the formation of Friedlander waves in a compressed-gas-driven shock tube

PubMed Central

Tasissa, Abiy F.; Hautefeuille, Martin; Fitek, John H.; Radovitzky, Raúl A.

2016-01-01

Compressed-gas-driven shock tubes have become popular as a laboratory-scale replacement for field blast tests. The well-known initial structure of the Riemann problem eventually evolves into a shock structure thought to resemble a Friedlander wave, although this remains to be demonstrated theoretically. In this paper, we develop a semi-analytical model to predict the key characteristics of pseudo blast waves forming in a shock tube: location where the wave first forms, peak over-pressure, decay time and impulse. The approach is based on combining the solutions of the two different types of wave interactions that arise in the shock tube after the family of rarefaction waves in the Riemann solution interacts with the closed end of the tube. The results of the analytical model are verified against numerical simulations obtained with a finite volume method. The model furnishes a rational approach to relate shock tube parameters to desired blast wave characteristics, and thus constitutes a useful tool for the design of shock tubes for blast testing. PMID:27118888

VizieR Online Data Catalog: Effects of preionization in radiative shocks (Sutherland+, 2017)

NASA Astrophysics Data System (ADS)

Sutherland, R. S.; Dopita, M. A.

2017-06-01

In this paper we treat the preionization problem in shocks over the velocity range 10

Sound velocities in highly oriented pyrolytic graphite shocked to 18 GPa: Orientational order dependence and elastic instability

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

Lucas, Marcel; Winey, J. M.; Gupta, Y. M.

Previous reports of rapid phase transformation above 18 GPa [Erskine and Nellis, Nature 349, 317 (1991)] and large elastic waves below 18 GPa [Lucas et al., J. Appl. Phys. 114, 093515 (2013)] for shock-compressed ZYB-grade highly-oriented pyrolytic graphite (HOPG), but not for less oriented ZYH-grade HOPG, indicated a link between the orientational order dependence of the HOPG response above and below the phase transformation stress. To gain insight into this link and into the mechanical response of HOPG shocked to peak stresses approaching the phase transformation onset, the compressibility of ZYB- and ZYH-grade HOPG in the shocked state was examinedmore » using front surface impact experiments. Particle velocity histories and sound velocities were measured for peak stresses reaching 18 GPa. Although the locus of the measured peak stress-particle velocity states is indistinguishable for the two grades of HOPG, the measured sound velocities in the peak state reveal significant differences between the two grades. Specifically, 1) The measured sound velocities are somewhat higher for ZYH-grade HOPG, compared to ZYB-grade HOPG. 2) The measured sound velocities for ZYH-grade HOPG increase smoothly with compression, whereas those for ZYB-2 grade HOPG exhibit a significant reduction in the compression dependence from 12 GPa to 17 GPa and an abrupt increase from 17 GPa to 18 GPa. 3) The longitudinal moduli, determined from the measured sound velocities, are smaller than the calculated bulk moduli for ZYB-grade HOPG shocked to peak stresses above 15 GPa, indicating the onset of an elastic instability. The present findings demonstrate that the softening of the longitudinal modulus (or elastic instability) presented here is linked to the large elastic waves and the rapid phase transformation reported previously – all observed only for shocked ZYB-grade HOPG. The elastic instability in shocked ZYB-grade HOPG is likely a precursor to the rapid phase transformation observed above 18 GPa for this HOPG grade.« less

Sound velocities in highly oriented pyrolytic graphite shocked to 18 GPa: Orientational order dependence and elastic instability

DOE PAGES

Lucas, Marcel; Winey, J. M.; Gupta, Y. M.

2015-12-28

Previous reports of rapid phase transformation above 18 GPa [Erskine and Nellis, Nature 349, 317 (1991)] and large elastic waves below 18 GPa [Lucas et al., J. Appl. Phys. 114, 093515 (2013)] for shock-compressed ZYB-grade highly-oriented pyrolytic graphite (HOPG), but not for less oriented ZYH-grade HOPG, indicated a link between the orientational order dependence of the HOPG response above and below the phase transformation stress. To gain insight into this link and into the mechanical response of HOPG shocked to peak stresses approaching the phase transformation onset, the compressibility of ZYB- and ZYH-grade HOPG in the shocked state was examinedmore » using front surface impact experiments. Particle velocity histories and sound velocities were measured for peak stresses reaching 18 GPa. Although the locus of the measured peak stress-particle velocity states is indistinguishable for the two grades of HOPG, the measured sound velocities in the peak state reveal significant differences between the two grades. Specifically, 1) The measured sound velocities are somewhat higher for ZYH-grade HOPG, compared to ZYB-grade HOPG. 2) The measured sound velocities for ZYH-grade HOPG increase smoothly with compression, whereas those for ZYB-2 grade HOPG exhibit a significant reduction in the compression dependence from 12 GPa to 17 GPa and an abrupt increase from 17 GPa to 18 GPa. 3) The longitudinal moduli, determined from the measured sound velocities, are smaller than the calculated bulk moduli for ZYB-grade HOPG shocked to peak stresses above 15 GPa, indicating the onset of an elastic instability. The present findings demonstrate that the softening of the longitudinal modulus (or elastic instability) presented here is linked to the large elastic waves and the rapid phase transformation reported previously – all observed only for shocked ZYB-grade HOPG. The elastic instability in shocked ZYB-grade HOPG is likely a precursor to the rapid phase transformation observed above 18 GPa for this HOPG grade.« less

Implications for paediatric shock management in resource-limited settings: a perspective from the FEAST trial.

PubMed

Houston, Kirsty Anne; George, Elizabeth C; Maitland, Kathryn

2018-05-04

Although the African "Fluid Expansion as Supportive therapy" (FEAST) trial showed fluid resuscitation was harmful in children with severe febrile illness managed in resource-limited hospitals, the most recent evidence reviewed World Health Organization (WHO) guidelines continue to recommend fluid boluses in children with shock according to WHO criteria "WHO shock", arguing that the numbers included in the FEAST trial were too small to provide reasonable certainty. We re-analysed the FEAST trial results for all international definitions for paediatric shock including hypotensive (or decompensated shock) and the WHO criteria. In addition, we examined the clinical relevance of the WHO criteria to published and unpublished observational studies reporting shock in resource-limited settings. We established that hypotension was rare in children with severe febrile illness complicating only 29/3170 trial participants (0.9%). We confirmed that fluid boluses were harmful irrespective of the definitions of shock including the very small number with WHO shock (n = 65). In this subgroup 48% of bolus recipients died at 48 h compared to 20% of the non-bolus control group, an increased absolute risk of 28%, but translating to an increased relative risk of 240% (p = 0.07 (two-sided Fisher's exact test)). Examining studies describing the prevalence of the stringent WHO shock criteria in children presenting to hospital we found this was rare (~ 0.1%) and in these children mortality was very high (41.5-100%). The updated WHO guidelines continue to recommend boluses for a very limited number of children presenting at hospital with the strict definition of WHO shock. Nevertheless, the 3% increased mortality from boluses seen across FEAST trial participants would also include this subgroup of children receiving boluses. Recommendations aiming to differentiate WHO shock from other definitions will invariably lead to "slippage" at the bedside, with the potential of exposing a wider group of children to the harm of fluid-bolus therapy.

Shock-induced transformations in crystalline RDX: a uniaxial constant-stress Hugoniostat molecular dynamics simulation study.

PubMed

Bedrov, Dmitry; Hooper, Justin B; Smith, Grant D; Sewell, Thomas D

2009-07-21

Molecular dynamics (MD) simulations of uniaxial shock compression along the [100] and [001] directions in the alpha polymorph of hexahydro-1,3,5-trinitro-1,3,5-triazine (alpha-RDX) have been conducted over a wide range of shock pressures using the uniaxial constant stress Hugoniostat method [Ravelo et al., Phys. Rev. B 70, 014103 (2004)]. We demonstrate that the Hugoniostat method is suitable for studying shock compression in atomic-scale models of energetic materials without the necessity to consider the extremely large simulation cells required for an explicit shock wave simulation. Specifically, direct comparison of results obtained using the Hugoniostat approach to those reported by Thompson and co-workers [Phys. Rev. B 78, 014107 (2008)] based on large-scale MD simulations of shocks using the shock front absorbing boundary condition (SFABC) approach indicates that Hugoniostat simulations of systems containing several thousand molecules reproduced the salient features observed in the SFABC simulations involving roughly a quarter-million molecules, namely, nucleation and growth of nanoscale shear bands for shocks propagating along the [100] direction and the polymorphic alpha-gamma phase transition for shocks directed along the [001] direction. The Hugoniostat simulations yielded predictions of the Hugoniot elastic limit for the [100] shock direction consistent with SFABC simulation results.

Existence regimes for shocks in inhomogeneous magneto-plasmas having entropy

NASA Astrophysics Data System (ADS)

Iqbal, Javed; Yaqub Khan, M.

2018-04-01

The finding of connection of plasma density and temperature with entropy gives an incitement to study different plasma models with respect to entropy. Nonlinear dissipative one- and two-dimensional structures (shocks) are investigated in nonuniform magnetized plasma with respect to entropy. The dissipation comes in the medium through ion-neutral collisions. The linear dispersion relation is derived. The Korteweg-deVries-Burgers and Kadomtsev-Petviashvili-Burgers equations are derived for nonlinear drift waves in 1-D and 2-D by employing the drift approximation. It is found that vd/u ( vd is the diamagnetic drift velocity and u is the velocity of nonlinear structure) plays a significant role in the shock formation. It is also found that entropy has a significant effect on the strength of shocks. It is noticed that v d/u determines the rarefactive and compressive nature of the shocks. It is observed that upper and lower bounds exist for the shock velocity. It is also observed that the existing regimes for both one- and two-dimensional shocks for kappa distributed electrons are different from shocks with Cairns distributed electrons. Both rarefactive and compressive shocks are found for the 1-D drift waves with kappa distributed electrons. Interestingly, it is noticed that entropy enhances the strength of one- and two-dimensional shocks.

Electrical Conductivity of ɛ-Iron under Shock Compression up to 208G Pa

NASA Astrophysics Data System (ADS)

Bi, Yan; Tan, Hua; Jing, Fu-Qian

2002-02-01

The electrical conductivity of shock-compressed iron was measured up to 208 GPa by using an improved design in experiment assembly in which the iron sample was encapsulated in a single-crystal sapphire cell. High-pressure shock compressions were generated by the plate impact technique with the two-stage light-gas gun. The measured conductivity of iron varies from 1.45×104 Ω-1 cm-1 at 101 GPa and 2010 K to 7.65×103 Ω-1 cm-1 at 208 GPa and 5220 K. After examining these data together with those reported, we found that the Bloch-Grüneisen expression is still valid at high pressures and temperatures, even up to 208 GPa and 5220 K, at least for ɛ-iron, which is significant in the field of condensed matter physics and deep interior earth science.

Enhanced densification under shock compression in porous silicon

DOE PAGES

Lane, J. Matthew; Thompson, Aidan Patrick; Vogler, Tracy

2014-10-27

Under shock compression, most porous materials exhibit lower densities for a given pressure than that of a full-dense sample of the same material. However, some porous materials exhibit an anomalous, or enhanced, densification under shock compression. The mechanism driving this behavior was not completely determined. We present evidence from atomistic simulation that pure silicon belongs to this anomalous class of materials and demonstrate the associated mechanisms responsible for the effect in porous silicon. Atomistic response indicates that local shear strain in the neighborhood of collapsing pores catalyzes a local solid-solid phase transformation even when bulk pressures are below the thermodynamicmore » phase transformation pressure. This metastable, local, and partial, solid-solid phase transformation, which accounts for the enhanced densification in silicon, is driven by the local stress state near the void, not equilibrium thermodynamics. This mechanism may also explain the phenomenon in other covalently bonded materials.« less

Staged Z-pinch for the production of high-flux neutrons and net energy

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

Wessel, Frank J.; Rahman, Hafiz Ur; Rostoker, Norman

A fusible target is embedded in a high Z liner, ohmically heated and then shock wave heated by implosion of an enveloping high Z liner. The target is adiabatically heated by compression, fusibly ignited and charged-particle heated as it is being ignited. A shock front forms as the liner implodes which shock front detaches from the more slowly moving liner, collides with the outer surface of the target, accelerates inward, rapidly heating the target, adiabatically compressing the target and liner and amplifying the current to converge the liner mass toward a central axis thereby compressing the target to a fusionmore » condition when it begins to ignite and produce charged particles. The charged particles are trapped in a large magnetic field surrounding the target. The energy of the charged particles is deposited into the target to further heat the target to produce an energy gain.« less

Birefringence and incipient plastic deformation in elastically overdriven [100] CaF2 under shock compression

NASA Astrophysics Data System (ADS)

Li, Y.; Zhou, X. M.; Cai, Y.; Liu, C. L.; Luo, S. N.

2018-04-01

[100] CaF2 single crystals are shock-compressed via symmetric planar impact, and the flyer plate-target interface velocity histories are measured with a laser displacement interferometry. The shock loading is slightly above the Hugoniot elastic limit to investigate incipient plasticity and its kinetics, and its effects on optical properties and deformation inhomogeneity. Fringe patterns demonstrate different features in modulation of fringe amplitude, including birefringence and complicated modulations. The birefringence is attributed to local lattice rotation accompanying incipient plasticity. Spatially resolved measurements show inhomogeneity in deformation, birefringence, and fringe pattern evolutions, most likely caused by the inhomogeneity associated with lattice rotation and dislocation slip. Transiently overdriven elastic states are observed, and the incubation time for incipient plasticity decreases inversely with increasing overdrive by the elastic shock.

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.

Effects of the Kv7 voltage-activated potassium channel inhibitor linopirdine in rat models of haemorrhagic shock.

PubMed

Nassoiy, Sean P; Babu, Favin S; LaPorte, Heather M; Byron, Kenneth L; Majetschak, Matthias

2018-04-27

Recently, we demonstrated that Kv7 voltage-activated potassium channel inhibitors reduce fluid resuscitation requirements in short-term rat models of haemorrhagic shock. The aim of the present study was to further delineate the therapeutic potential and side effect profile of the Kv7 channel blocker linopirdine in various rat models of severe haemorrhagic shock over clinically relevant time periods. Intravenous administration of linopirdine, either before (1 or 3 mg/kg) or after (3 mg/kg) a 40% blood volume haemorrhage, did not affect blood pressure and survival in lethal haemorrhage models without fluid resuscitation. A single bolus of linopirdine (3 mg/kg) at the beginning of fluid resuscitation after haemorrhagic shock transiently reduced early fluid requirements in spontaneously breathing animals that were resuscitated for 3.5 hours. When mechanically ventilated rats were resuscitated after haemorrhagic shock with normal saline (NS) or with linopirdine-supplemented (10, 25 or 50 μg/mL) NS for 4.5 hours, linopirdine significantly and dose-dependently reduced fluid requirements by 14%, 45% and 55%, respectively. Lung and colon wet/dry weight ratios were reduced with linopirdine (25/50 μg/mL). There was no evidence for toxicity or adverse effects based on measurements of routine laboratory parameters and inflammation markers in plasma and tissue homogenates. Our findings support the concept that linopirdine-supplementation of resuscitation fluids is a safe and effective approach to reduce fluid requirements and tissue oedema formation during resuscitation from haemorrhagic shock. © 2018 John Wiley & Sons Australia, Ltd.

Main drive optimization of a high-foot pulse shape in inertial confinement fusion implosions

NASA Astrophysics Data System (ADS)

Wang, L. F.; Ye, W. H.; Wu, J. F.; Liu, Jie; Zhang, W. Y.; He, X. T.

2016-12-01

While progress towards hot-spot ignition has been made achieving an alpha-heating dominated state in high-foot implosion experiments [Hurricane et al., Nat. Phys. 12, 800 (2016)] on the National Ignition Facility, improvements are needed to increase the fuel compression for the enhancement of the neutron yield. A strategy is proposed to improve the fuel compression through the recompression of a shock/compression wave generated by the end of the main drive portion of a high-foot pulse shape. Two methods for the peak pulse recompression, namely, the decompression-and-recompression (DR) and simple recompression schemes, are investigated and compared. Radiation hydrodynamic simulations confirm that the peak pulse recompression can clearly improve fuel compression without significantly compromising the implosion stability. In particular, when the convergent DR shock is tuned to encounter the divergent shock from the capsule center at a suitable position, not only the neutron yield but also the stability of stagnating hot-spot can be noticeably improved, compared to the conventional high-foot implosions [Hurricane et al., Phys. Plasmas 21, 056314 (2014)].

Extended x-ray absorption fine structure measurements of quasi-isentropically compressed vanadium targets on the OMEGA laser

NASA Astrophysics Data System (ADS)

Yaakobi, B.; Boehly, T. R.; Sangster, T. C.; Meyerhofer, D. D.; Remington, B. A.; Allen, P. G.; Pollaine, S. M.; Lorenzana, H. E.; Lorenz, K. T.; Hawreliak, J. A.

2008-06-01

The use of in situ extended x-ray absorption fine structure (EXAFS) for characterizing nanosecond laser-shocked vanadium, titanium, and iron has recently been demonstrated. These measurements are extended to laser-driven, quasi-isentropic compression experiments (ICE). The radiation source (backlighter) for EXAFS in all of these experiments is obtained by imploding a spherical target on the OMEGA laser [T. R. Boehly et al., Rev. Sci. Instrum. 66, 508 (1995)]. Isentropic compression (where the entropy is kept constant) enables to reach high compressions at relatively low temperatures. The absorption spectra are used to determine the temperature and compression in a vanadium sample quasi-isentropically compressed to pressures of up to ˜0.75Mbar. The ability to measure the temperature and compression directly is unique to EXAFS. The drive pressure is calibrated by substituting aluminum for the vanadium and interferometrically measuring the velocity of the back target surface by the velocity interferometer system for any reflector (VISAR). The experimental results obtained by EXAFS and VISAR agree with each other and with the simulations of a hydrodynamic code. The role of a shield to protect the sample from impact heating is studied. It is shown that the shield produces an initial weak shock that is followed by a quasi-isentropic compression at a relatively low temperature. The role of radiation heating from the imploding target as well as from the laser-absorption region is studied. The results show that in laser-driven ICE, as compared with laser-driven shocks, comparable compressions can be achieved at lower temperatures. The EXAFS results show important details not seen in the VISAR results.

Laboratory Studies of Survival Limits of Bacteria During Shock Compression: Application to Impacts on the Early Earth

NASA Astrophysics Data System (ADS)

Willis, M. J.; Ahrens, T. J.; Bertani, L. E.; Nash, C. Z.

2004-12-01

Shock recovery experiments on suspensions of 106 mm-3 E. coli bacteria contained in water-based medium, within stainless steel containers, are used to simulate the impact environment of bacteria residing in water-filled cracks in rocks. Early Earth life is likely to have existed in such environments. Some 10-2 to 10-4 of the bacteria population survived initial (800 ns duration) shock pressures in water of 219 and 260 MPa. TEM images of shock recovered bacteria indicate cell wall indentations and rupture, possibly induced by inward invasion of medium into the cell wall. Notably cell wall rupture occurs dynamically at ˜0.1 times the static pressures E.coli have been demonstrated (Sharma et al., 2002) to survive and may be caused by Rayleigh-Taylor instabilities. We infer the invading fluid pressure may exceed the tensile strength of the cell wall. We assume the overpressures are limited to the initial shock pressure in water. Parameters for the Grady & Lipkin (1980) model of tensile failure versus time-scale (strain rate) are fit to present data, assuming that at low strain rates, overpressures exceeding cell Turgor pressure require ˜103 sec. This model, if validated by experiments at other timescales, may permit using short loading duration laboratory data to infer response of organisms to lower shock overpressures for the longer times (100 to 103 s) of planetary impacts. An Ahrens & O'Keefe (1987) shock attenuation model is then applied for Earth impactors. This model suggests that Earth impactors of radius 1.5 km induce shocks within water-filled cracks in rock to dynamic pressure such that stresses exceeding the survivability threshold of E. coli bacteria, to radii of 1.7-2.6×102 km. In contrast, a giant (1500 km radius) impactor produces a non survival zone for E. coli that encompasses the entire Earth.

Explicit and implicit compact high-resolution shock-capturing methods for multidimensional Euler equations 1: Formulation

NASA Technical Reports Server (NTRS)

Yee, H. C.

1995-01-01

Two classes of explicit compact high-resolution shock-capturing methods for the multidimensional compressible Euler equations for fluid dynamics are constructed. Some of these schemes can be fourth-order accurate away from discontinuities. For the semi-discrete case their shock-capturing properties are of the total variation diminishing (TVD), total variation bounded (TVB), total variation diminishing in the mean (TVDM), essentially nonoscillatory (ENO), or positive type of scheme for 1-D scalar hyperbolic conservation laws and are positive schemes in more than one dimension. These fourth-order schemes require the same grid stencil as their second-order non-compact cousins. One class does not require the standard matrix inversion or a special numerical boundary condition treatment associated with typical compact schemes. Due to the construction, these schemes can be viewed as approximations to genuinely multidimensional schemes in the sense that they might produce less distortion in spherical type shocks and are more accurate in vortex type flows than schemes based purely on one-dimensional extensions. However, one class has a more desirable high-resolution shock-capturing property and a smaller operation count in 3-D than the other class. The extension of these schemes to coupled nonlinear systems can be accomplished using the Roe approximate Riemann solver, the generalized Steger and Warming flux-vector splitting or the van Leer type flux-vector splitting. Modification to existing high-resolution second- or third-order non-compact shock-capturing computer codes is minimal. High-resolution shock-capturing properties can also be achieved via a variant of the second-order Lax-Friedrichs numerical flux without the use of Riemann solvers for coupled nonlinear systems with comparable operations count to their classical shock-capturing counterparts. The simplest extension to viscous flows can be achieved by using the standard fourth-order compact or non-compact formula for the viscous terms.

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

Vignati, F.; Guardone, A., E-mail: alberto.guardone@polimi.it

Cylindrical converging shock waves interacting with an array of aerodynamic obstacles are investigated numerically for diverse shock strengths and for different obstacle configurations in air in standard conditions. The considered number of obstacles N is 4, 6, 8, 16, and 24. Obstacles are lenticular airfoils with thickness-to-chord ratios t/c of 0.07, 0.14, and 0.21. The distances of the airfoil leading edge from the shock focus point (r{sub LE})/(r{sub LE}{sup ref}) are 1, 2, and 2.5, where r{sub LE}{sup ref}=7 is the dimensionless reference distance from the origin. Considered impinging shock Mach numbers M{sub s} are 2.2, 2.7, and 3.2 atmore » the reference distance from the origin. The reference experimental configuration (N=8,t/c =0.14,r{sub LE}=7,M{sub s}=2.7) was proposed by Kjellander et al. [“Thermal radiation from a converging shock implosion,” Phys. Fluids 22, 046102 (2010)]. Numerical results compare fairly well to available one-dimensional models for shock propagation and to available experimental results in the reference configuration. Local reflection types are in good agreement with the classical criteria for planar shock waves. The main shock reshaping patterns are identified and their dependence on the shock strength and obstacle configuration is exposed. In particular, different shock patterns are observed after the leading edge reflection, which results in polygonal shock wave with N, 2N, 3N, and 4N sides. The largest temperature peak at the origin is obtained for the 8- and the 16-obstacle configurations and for the smallest thickness to length ratio, 0.07, located at distance from the origin of 2r{sub LE}{sup ref}. In terms of compression efficiency at the origin, the 16-obstacle configuration is found to perform slightly better than the reference 8-obstacle configuration—with an efficiency increase of about 2%-3%, which is well within the model accuracy—thus confirming the goodness of the obstacle arrangement proposed by Kjellander and collaborators.« less

Detailed computational procedure for design of cascade blades with prescribed velocity distributions in compressible potential flows

NASA Technical Reports Server (NTRS)

Costello, George R; Cummings, Robert L; Sinnette, John T , Jr

1952-01-01

A detailed step-by-step computational outline is presented for the design of two-dimensional cascade blades having a prescribed velocity distribution on the blade in a potential flow of the usual compressible fluid. The outline is based on the assumption that the magnitude of the velocity in the flow of the usual compressible nonviscous fluid is proportional to the magnitude of the velocity in the flow of a compressible nonviscous fluid with linear pressure-volume relation.

Enhancing Impact Speed with Shock Interactions in a Restricting Die

NASA Astrophysics Data System (ADS)

Anderson, William; Jensen, Brian; Cherne, Frank; Owens, Charles; Ramos, Kyle; Lieber, Mark

2013-06-01

There is a need to increase the impact velocities that can be achieved with gun systems used for impact and shock compression studies. Two-stage guns normally required for high-velocity studies are expensive and relatively rare, while most single-stage guns have modest performance (0.2-2 km/s) that limits their utility for high-pressure and high-velocity studies. In this work, we are developing a technique that uses a low-strength sabot, coupled with a restricting die, to increase the impact velocity without modifying the gun itself. Impact of the projectile with the die, which is typically attached to the muzzle of the gun, generates shock waves in the sabot that interact to accelerate the front of the projectile, while decelerating the rear portion. The performance achieved by this technique is greater than would be expected from a simple nozzle working on a fluid with the properties of the sabot. Preliminary experiments using this technique have observed a velocity enhancement of close to a factor of two. The performance that can be achieved is critically dependent on the stress field geometry and we are currently developing a set of models and calculations to optimize this system. Work performed under DOE Contract DE-AC52-06NA25396.

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.

Shock compression dynamics under a microscope.

NASA Astrophysics Data System (ADS)

Dlott, Dana

2015-06-01

We have developed a tabletop laser flyer launch system1 that solves many of the problems that plagued previous efforts. Using a novel mechanism where a spatially-uniform laser pulse creates a shock in a glass substrate just underneath a metal foil, we can launch tiny (0.7 mm diameter x 100 μm thick) flyers at speeds ranging from 0-5 km/s and the foils are flat, cold and intact. This tabletop launch system, where we often launch 100 flyers per day, provides a platform for a wide variety of time-resolved spectroscopies. The shocked material is viewed by a microscope objective that transmits near-infrared light from a photon Doppler velocimeter to monitor the flyer, and collects the light for spectroscopic and video images. Fluorescent probes, which have been highly developed for the biomedical sciences, have proven especially useful for these experiments. Using emission measurements, we have investigated the fundamental mechanisms of many shock wave effects including: viscoelastic compression of high molecular weight polymers, visualization of shocks in porous media such as sand, where we can observe the behavior of individual grains of sand, shock attenuation by passing the shock through reactive materials that undergo endothermic chemical reactions, and shock initiation of nanoenergetic materials.

X-ray Scattering Measurement of the Heat Capacity Ratio in Shock Compressed Matter

NASA Astrophysics Data System (ADS)

Fortmann, C.; Lee, H. J.; Doeppner, Tilo; Kritcher, A. L.; Landen, O. L.; Falcone, R. W.; Glenzer, S. H.

2011-10-01

We developed accurate x-ray scattering techniques to measure properties of matter under extreme conditions of density and temperature in intense laser-solid interaction experiments. We report on novel applications of x-ray scattering to measure the heat-capacity ratio γ =cp /cv of a Be plasma which determines the equation of state of the system. Ultraintense laser radiation is focussed onto both sides of a Be foil, creating two counterpropagating planar shock waves that collide in the target center. A second set of lasers produces Zn He- α radiation of 8.9 keV energy that scatters from the shock-compressed matter. We observe temperatures of 10eV and 15eV and mass densities of 5g/cm3 and 11g/cm3 before and after the shock collision. Applying the Rankine-Hugoniot relations for counterpropagating shocks we then infer γ as a function of density using only the measured mass compression ratios. Our results agree with equation of state models and DFT simulations. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. We acknowledge support from the Alexander von Humboldt-Foundation.

Equation of state and shock compression of warm dense sodium—A first-principles study

DOE PAGES

Zhang, Shuai; Driver, Kevin P.; Soubiran, Francois; ...

2017-02-21

As one of the simple alkali metals, sodium has been of fundamental interest for shock physics experiments, but knowledge of its equation of state (EOS) in hot, dense regimes is not well known. By combining path integral Monte Carlo (PIMC) results for partially ionized states at high temperatures and density functional theory molecular dynamics (DFT-MD) results at lower temperatures, we have constructed a coherent equation of state for sodium over a wide density-temperature range of 1.93-11.60 g/cm 3 and 10 3–1.29×10 8 K. We find that a localized, Hartree-Fock nodal structure in PIMC yields pressures and internal energies that aremore » consistent with DFT-MD at intermediate temperatures of 2×10 6 K. Since PIMC and DFT-MD provide a first-principles treatment of electron shell and excitation effects, we are able to identify two compression maxima in the shock Hugoniot curve corresponding to K-shell and L-shell ionization. Our Hugoniot curves provide a benchmark for widely used EOS models: SESAME, LEOS, and Purgatorio. Due to the low ambient density, sodium has an unusually high first compression maximum along the shock Hugoniot curve. At beyond 10 7 K, we show that the radiation effect leads to very high compression along the Hugoniot curve, surpassing relativistic corrections, and observe an increasing deviation of the shock and particle velocities from a linear relation. Here, we also compute the temperature-density dependence of thermal and pressure ionization processes.« less

Test Operations Procedure (TOP) 10-2-400 Open End Compressed Gas Driven Shock Tube

DTIC Science & Technology

gas-driven shock tube. Procedures are provided for instrumentation, test item positioning, estimation of key test parameters, operation of the shock...tube, data collection, and reporting. The procedures in this document are based on the use of helium gas and Mylar film diaphragms.

Physical Intrepretation of Mathematically Invariant K(r,P) Type Equations of State for Hydrodynamically Driven Flow

NASA Astrophysics Data System (ADS)

Hrbek, George

2001-06-01

At SCCM Shock 99, Lie Group Theory was applied to the problem of temperature independent, hydrodynamic shock in a Birch-Murnaghan continuum. (1) Ratios of the group parameters were shown to be linked to the physical parameters specified in the second, third, and fourth order BM-EOS approximations. This effort has subsequently been extended to provide a general formalism for a wide class of mathematical forms (i.e., K(r,P)) of the equation of state. Variations in material expansion and resistance (i.e., counter pressure) are shown to be functions of compression and material variation ahead of the expanding front. Specific examples included the Birch-Murnaghan, Vinet, Brennan-Stacey, Shanker, Tait, Poirier, and Jones-Wilkins-Lee (JWL) forms. (2) With these ratios defined, the next step is to predict the behavior of these K(r,P) type solids. To do this, one must introduce the group ratios into a numerical simulation for the flow and generate the density, pressure, and particle velocity profiles as the shock moves through the material. This will allow the various equations of state, and their respective fitting coefficients, to be compared with experiments, and additionally, allow the empirical coefficients for these EOS forms to be adjusted accordingly. (1) Hrbek, G. M., Invariant Functional Forms For The Second, Third, And Fourth Order Birch-Murnaghan Equation of State For Materials Subject to Hydrodynamic Shock, Proceedings of the 11th American Physical Society Topical Group Meeting on Shock Compression of Condensed Matter (SCCM Shock 99), Snowbird, Utah (2) Hrbek, G. M., Invariant Functional Forms For K(r,P) Type Equations Of State For Hydrodynamically Driven Flows, Submitted to the 12th American Physical Society Topical Group Meeting on Shock Compression of Condensed Matter (SCCM Shock 01), Atlanta, Georgia

Compressible Flow Toolbox

NASA Technical Reports Server (NTRS)

Melcher, Kevin J.

2006-01-01

The Compressible Flow Toolbox is primarily a MATLAB-language implementation of a set of algorithms that solve approximately 280 linear and nonlinear classical equations for compressible flow. The toolbox is useful for analysis of one-dimensional steady flow with either constant entropy, friction, heat transfer, or Mach number greater than 1. The toolbox also contains algorithms for comparing and validating the equation-solving algorithms against solutions previously published in open literature. The classical equations solved by the Compressible Flow Toolbox are as follows: The isentropic-flow equations, The Fanno flow equations (pertaining to flow of an ideal gas in a pipe with friction), The Rayleigh flow equations (pertaining to frictionless flow of an ideal gas, with heat transfer, in a pipe of constant cross section), The normal-shock equations, The oblique-shock equations, and The expansion equations.

Improved ALE mesh velocities for complex flows

DOE PAGES

Bakosi, Jozsef; Waltz, Jacob I.; Morgan, Nathaniel Ray

2017-05-31

A key choice in the development of arbitrary Lagrangian-Eulerian solution algorithms is how to move the computational mesh. The most common approaches are smoothing and relaxation techniques, or to compute a mesh velocity field that produces smooth mesh displacements. We present a method in which the mesh velocity is specified by the irrotational component of the fluid velocity as computed from a Helmholtz decomposition, and excess compression of mesh cells is treated through a noniterative, local spring-force model. This approach allows distinct and separate control over rotational and translational modes. In conclusion, the utility of the new mesh motion algorithmmore » is demonstrated on a number of 3D test problems, including problems that involve both shocks and significant amounts of vorticity.« less

Dynamic response and residual stress fields of Ti6Al4V alloy under shock wave induced by laser shock peening

NASA Astrophysics Data System (ADS)

Sun, Rujian; Li, Liuhe; Zhu, Ying; Zhang, Lixin; Guo, Wei; Peng, Peng; Li, Bo; Guo, Chao; Liu, Lei; Che, Zhigang; Li, Weidong; Sun, Jianfei; Qiao, Hongchao

2017-09-01

Laser shock peening (LSP), an innovative surface treatment technique, generates compressive residual stress on the surface of metallic components to improve their fatigue performance, wear resistance and corrosion resistance. To illustrate the dynamic response during LSP and residual stress fields after LSP, this study conducted FEM simulations of LSP in a Ti6Al4V alloy. Results showed that when power density was 7 GW cm-2, a plastic deformation occurred at 10 ns during LSP and increased until the shock pressure decayed below the dynamic yield strength of Ti6Al4V after 60 ns. A maximum tensile region appeared beneath the surface at around 240 ns, forming a compressive-tensile-compressive stress sandwich structure with a thickness of 98, 1020 and 606 μm for each layer. After the model became stabilized, the value of the surface residual compressive stress was 564 MPa at the laser spot center. Higher value of residual stress across the surface and thicker compressive residual stress layers were achieved by increasing laser power density, impact times and spot sizes during LSP. A ‘Residual stress hole’ occurred with a high laser power density of 9 GW cm-2 when laser pulse duration was 10 ns, or with a long laser pulse duration of 20 ns when laser power density was 7 GW cm-2 for Ti6Al4V. This phenomenon occurred because of the permanent reverse plastic deformation generated at laser spot center.

Equation of state of Mo from shock compression experiments on preheated samples

NASA Astrophysics Data System (ADS)

Fat'yanov, O. V.; Asimow, P. D.

2017-03-01

We present a reanalysis of reported Hugoniot data for Mo, including both experiments shocked from ambient temperature (T) and those preheated to 1673 K, using the most general methods of least-squares fitting to constrain the Grüneisen model. This updated Mie-Grüneisen equation of state (EOS) is used to construct a family of maximum likelihood Hugoniots of Mo from initial temperatures of 298 to 2350 K and a parameterization valid over this range. We adopted a single linear function at each initial temperature over the entire range of particle velocities considered. Total uncertainties of all the EOS parameters and correlation coefficients for these uncertainties are given. The improved predictive capabilities of our EOS for Mo are confirmed by (1) better agreement between calculated bulk sound speeds and published measurements along the principal Hugoniot, (2) good agreement between our Grüneisen data and three reported high-pressure γ ( V ) functions obtained from shock-compression of porous samples, and (3) very good agreement between our 1 bar Grüneisen values and γ ( T ) at ambient pressure recalculated from reported experimental data on the adiabatic bulk modulus K s ( T ) . Our analysis shows that an EOS constructed from shock compression data allows a much more accurate prediction of γ ( T ) values at 1 bar than those based on static compression measurements or first-principles calculations. Published calibrations of the Mie-Grüneisen EOS for Mo using static compression measurements only do not reproduce even low-pressure asymptotic values of γ ( T ) at 1 bar, where the most accurate experimental data are available.

Simulations of in situ x-ray diffraction from uniaxially compressed highly textured polycrystalline targets

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

McGonegle, David, E-mail: d.mcgonegle1@physics.ox.ac.uk; Wark, Justin S.; Higginbotham, Andrew

2015-08-14

A growing number of shock compression experiments, especially those involving laser compression, are taking advantage of in situ x-ray diffraction as a tool to interrogate structure and microstructure evolution. Although these experiments are becoming increasingly sophisticated, there has been little work on exploiting the textured nature of polycrystalline targets to gain information on sample response. Here, we describe how to generate simulated x-ray diffraction patterns from materials with an arbitrary texture function subject to a general deformation gradient. We will present simulations of Debye-Scherrer x-ray diffraction from highly textured polycrystalline targets that have been subjected to uniaxial compression, as maymore » occur under planar shock conditions. In particular, we study samples with a fibre texture, and find that the azimuthal dependence of the diffraction patterns contains information that, in principle, affords discrimination between a number of similar shock-deformation mechanisms. For certain cases, we compare our method with results obtained by taking the Fourier transform of the atomic positions calculated by classical molecular dynamics simulations. Illustrative results are presented for the shock-induced α–ϵ phase transition in iron, the α–ω transition in titanium and deformation due to twinning in tantalum that is initially preferentially textured along [001] and [011]. The simulations are relevant to experiments that can now be performed using 4th generation light sources, where single-shot x-ray diffraction patterns from crystals compressed via laser-ablation can be obtained on timescales shorter than a phonon period.« less

Simulations of in situ x-ray diffraction from uniaxially compressed highly textured polycrystalline targets

DOE PAGES

McGonegle, David; Milathianaki, Despina; Remington, Bruce A.; ...

2015-08-11

A growing number of shock compression experiments, especially those involving laser compression, are taking advantage of in situ x-ray diffraction as a tool to interrogate structure and microstructure evolution. Although these experiments are becoming increasingly sophisticated, there has been little work on exploiting the textured nature of polycrystalline targets to gain information on sample response. Here, we describe how to generate simulated x-ray diffraction patterns from materials with an arbitrary texture function subject to a general deformation gradient. We will present simulations of Debye-Scherrer x-ray diffraction from highly textured polycrystalline targets that have been subjected to uniaxial compression, as maymore » occur under planar shock conditions. In particular, we study samples with a fibre texture, and find that the azimuthal dependence of the diffraction patterns contains information that, in principle, affords discrimination between a number of similar shock-deformation mechanisms. For certain cases, we compare our method with results obtained by taking the Fourier transform of the atomic positions calculated by classical molecular dynamics simulations. Illustrative results are presented for the shock-induced α–ϵ phase transition in iron, the α–ω transition in titanium and deformation due to twinning in tantalum that is initially preferentially textured along [001] and [011]. In conclusion, the simulations are relevant to experiments that can now be performed using 4th generation light sources, where single-shot x-ray diffraction patterns from crystals compressed via laser-ablation can be obtained on timescales shorter than a phonon period.« less

Vascular leakage in dengue--clinical spectrum and influence of parenteral fluid therapy.

PubMed

Rosenberger, Kerstin D; Lum, Lucy; Alexander, Neal; Junghanss, Thomas; Wills, Bridget; Jaenisch, Thomas

2016-03-01

Clinical management of dengue relies on careful monitoring of fluid balance combined with judicious intravenous (IV) fluid therapy. However, in patients with significant vascular leakage, IV fluids may aggravate serosal fluid accumulation and result in respiratory distress. Trained physicians followed suspected dengue cases prospectively at seven hospitals across Asia and Latin America, using a comprehensive case report form that included daily clinical assessment and detailed documentation of parenteral fluid therapy. Applying Cox regression, we evaluated risk factors for the development of shock or respiratory distress with fluid accumulation. Most confirmed dengue patients (1524/1734, 88%) never experienced dengue shock syndrome (DSS). Among those with DSS, 176/210 (84%) had fluid accumulation, and in the majority (83%), this was detectable clinically. Among all cases with clinically detectable fluid accumulation, 179/447 (40%) were diagnosed with shock or respiratory distress. The risk for respiratory distress with fluid accumulation increased significantly as the infused volume over the preceding 24 h increased (hazard ratio 1.18 per 10 ml/kg increase; P < 0.001). Longer duration of IV therapy, use of a fluid bolus in the preceding 24 h, female gender and poor nutrition also constituted independent risk factors. Shock and respiratory distress are relatively rare manifestations of dengue, but some evidence of fluid accumulation is seen in around 50% of cases. IV fluids play a crucial role in management, but they must be administered with caution. Clinically and/or radiologically detectable fluid accumulations have potential as intermediate severity endpoints for therapeutic intervention trials and/or pathogenesis studies. © 2016 John Wiley & Sons Ltd.

Effect of seven different additives on the properties of MR fluids

NASA Astrophysics Data System (ADS)

Zhang, J. Q.; Zhang, J.; Jing, Q.

2009-02-01

Magnetorheological (MR) fluids have been developed for application in semi-active magnetorheological fluid dampers and other magnetorheological fluid devices. In order to prepare special MR fluids to satisfy the demands of tracked vehicle, two different carrier fluids were chose to prepare MR fluids. Preparation of MR fluids, which are based on carriers such as special shock absorption fluid and 45# transformer oil, was finished. And characteristics of these samples were tested and analyzed. Results indicate, Tween-80 and Span-80 can improve sedimentary stability. Using 45# transformer oil instead of special shock absorption fluid as a carrier, the shear yield stress remains nearly invariable but the viscosity and the sedimentary stability are reduced. MR fluids with diameter of 2.73μm show better sedimentary stability than that of the MR fluids with diameter of 2.3μm, or 4.02μm. Stearic acid obviously improves sedimentary stability and off-state viscosity, but don't perform an obvious function on shear yield stress. In magnetic field of 237KA/m, the shear yield stress of MR fluid based on special shock absorption fluid and 45# transformer oil is 18.34KPa, 14.26KPa, respectively.

Numerical study of compressible magnetoconvection with an open transitional boundary

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

Hanami, H.; Tajima, T.

1990-08-01

We study by computer simulation nonlinear evolution of magnetoconvection in a system with a dynamical open boundary between the convection region and corona of the sun. We study a model in which the fluid is subject to the vertical gravitation, magnetohydrodynamics (MHD), and high stratification, through an MHD code with the MacCormack-Donner cell hybrid scheme in order to well represent convective phenomena. Initially the vertical fluid flux penetrates from the convectively unstable zone at the bottom into the upper diffuse atmosphere. As the instability develops, the magnetic fields are twisted by the convection motion and the folding magnetic fields ismore » observed. When the magnetic pressure is comparable to the thermal pressure in the upper layer of convective zone, strong flux expulsion from the convective cell interior toward the cell boundary appears. Under appropriate conditions our simulation exhibits no shock formation incurred by the fluid convected to the photosphere, in contrast to earlier works with box boundaries. The magnetic field patterns observed are those of concentrated magnetic flux tubes, accumulation of dynamo flux near the bottom boundary, pinched flux near the downdraft region, and the surface movement of magnetic flux toward the downdraft region. Many of these computationally observed features are reminiscent of solar observations of the fluid and magnetic structures of their motions.« less

Drift-based scrape-off particle width in X-point geometry

NASA Astrophysics Data System (ADS)

Reiser, D.; Eich, T.

2017-04-01

The Goldston heuristic estimate of the scrape-off layer width (Goldston 2012 Nucl. Fusion 52 013009) is reconsidered using a fluid description for the plasma dynamics. The basic ingredient is the inclusion of a compressible diamagnetic drift for the particle cross field transport. Instead of testing the heuristic model in a sophisticated numerical simulation including several physical mechanisms working together, the purpose of this work is to point out basic consequences for a drift-dominated cross field transport using a reduced fluid model. To evaluate the model equations and prepare them for subsequent numerical solution a specific analytical model for 2D magnetic field configurations with X-points is employed. In a first step parameter scans in high-resolution grids for isothermal plasmas are done to assess the basic formulas of the heuristic model with respect to the functional dependence of the scrape-off width on the poloidal magnetic field and plasma temperature. Particular features in the 2D-fluid calculations—especially the appearance of supersonic parallel flows and shock wave like bifurcational jumps—are discussed and can be understood partly in the framework of a reduced 1D model. The resulting semi-analytical findings might give hints for experimental proof and implementation in more elaborated fluid simulations.

Evolutions of elastic-plastic shock compression waves in different materials

NASA Astrophysics Data System (ADS)

Kanel, G. I.; Zaretsky, E. B.; Razorenov, S. V.; Savinykh, A. S.; Garkushin, G. V.

2017-01-01

In the paper, we discuss such unexpected features in the wave evolution in solids as a departure from self-similar development of the wave process which is accompanied with apparent sub-sonic wave propagation, changes of shape of elastic precursor wave as a result of variations in the material structure and the temperature, unexpected peculiarities of reflection of elastic-plastic waves from free surface, effects of internal friction at shock compression of glasses and some other effects.

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.

Time irreversibility of the statistics of a single particle in compressible turbulence

NASA Astrophysics Data System (ADS)

Grafke, Tobias; Frishman, Anna; Falkovich, Gregory

2015-04-01

We investigate time irreversibility from the point of view of a single particle in Burgers turbulence. Inspired by the recent work for incompressible flows [Xu et al., Proc. Natl. Acad. Sci. USA 111, 7558 (2014), 10.1073/pnas.1321682111], we analyze the evolution of the kinetic energy for fluid markers and use the fluctuations of the instantaneous power as a measure of time irreversibility. For short times, starting from a uniform distribution of markers, we find the scaling <[E(t ) -E (0 ) ] n>∝t and ∝Ren -1 for the power as a function of the Reynolds number. Both observations can be explained using the "flight-crash" model, suggested by Xu et al. Furthermore, we use a simple model for shocks that reproduces the moments of the energy difference, including the pre-factor for . To complete the single-particle picture for Burgers we compute the moments of the Lagrangian velocity difference and show that they are bifractal. This arises in a similar manner to the bifractality of Eulerian velocity differences. In the above setting, time irreversibility is directly manifest as particles eventually end up in shocks. We additionally investigate time irreversibility in the long-time limit when all particles are located inside shocks and the Lagrangian velocity statistics are stationary. We find the same scalings for the power and energy differences as at short times and argue that this is also a consequence of rare "flight-crash" events related to shock collisions.

The resolved layer of a collisionless, high beta, supercritical, quasi-perpendicular shock wave. II - Dissipative fluid electrodynamics

NASA Technical Reports Server (NTRS)

Scudder, J. D.; Aggson, T. L.; Mangeney, A.; Lacombe, C.; Harvey, C. C.

1986-01-01

Using the results of Scudder et al. (1986) on the bow shock wave observed by ISEE satellites, a quantitative description is presented of the electrodynamics of ion and electron fluids, and phase-standing wave interaction which manifests itself as a supercritical MHD shock. The cross-shock electrical profile was determined in both the normal incidence frame and in the deHoffman-Teller frame by two different methods, and the results were compared with dc electric field measurements.

Effect of rock rheology on fluid leak- off during hydraulic fracturing

NASA Astrophysics Data System (ADS)

Yarushina, V. M.; Bercovici, D.; Oristaglio, M. L.

2012-04-01

In this communication, we evaluate the effect of rock rheology on fluid leak­off during hydraulic fracturing of reservoirs. Fluid leak-off in hydraulic fracturing is often nonlinear. The simple linear model developed by Carter (1957) for flow of fracturing fluid into a reservoir has three different regions in the fractured zone: a filter cake on the fracture face, formed by solid additives from the fracturing fluid; a filtrate zone affected by invasion of the fracturing fluid; and a reservoir zone with the original formation fluid. The width of each zone, as well as its permeability and pressure drop, is assumed to remain constant. Physical intuition suggests some straightforward corrections to this classical theory to take into account the pressure dependence of permeability, the compressibility or non-Newtonian rheology of fracturing fluid, and the radial (versus linear) geometry of fluid leak­off from the borehole. All of these refinements, however, still assume that the reservoir rock adjacent to the fracture face is non­deformable. Although the effect of poroelastic stress changes on leak-off is usually thought to be negligible, at the very high fluid pressures used in hydraulic fracturing, where the stresses exceed the rock strength, elastic rheology may not be the best choice. For example, calculations show that perfectly elastic rock formations do not undergo the degree of compaction typically seen in sedimentary basins. Therefore, pseudo-elastic or elastoplastic models are used to fit observed porosity profiles with depth. Starting from balance equations for mass and momentum for fluid and rock, we derive a hydraulic flow equation coupled with a porosity equation describing rock compaction. The result resembles a pressure diffusion equation with the total compressibility being a sum of fluid, rock and pore-space compressibilities. With linear elastic rheology, the bulk formation compressibility is dominated by fluid compressibility. But the possibility of permanent, time-independent (plastic) rock deformation significantly increases the pore space compressibility (compaction), which becomes a leading term in the total compressibility. Inclusion of rock and fluid compressibilities in the model can explain both linear and nonlinear leak­off. In particular, inclusion of rock compaction and decompaction may be important for description of naturally fractured and tight gas reservoirs for which very strong dependence of permeability on porosity has been reported. Carter R.D. Derivation of the general equation for estimating the extent of the fractured area. Appendix I of "Optimum fluid characteristics for fracture extension", Drilling and Production Practice, G.C. Howard and C.R.Fast, New York, New York, USA, American Petroleum Institute (1957), 261-269.

Shock and Static Compression of Nitrobenzene

NASA Astrophysics Data System (ADS)

Kozu, Naoshi; Arai, Mitsuru; Tamura, Masamitsu; Fujihisa, Hiroshi; Aoki, Katsutoshi; Yoshida, Masatake

2000-08-01

The Hugoniot and static compression curve (isotherm) were investigated using explosive plane wave generators and diamond anvil cells, respectively. The obtained Hugoniot from the shock experiments is represented by two linear lines: Us=2.52+1.23 up (0.8

The α-γ-ɛ triple point and phase boundaries of iron under shock compression

NASA Astrophysics Data System (ADS)

Li, Jun; Wu, Qiang; Xue, Tao; Geng, Huayun; Yu, Jidong; Jin, Ke; Li, Jiabo; Tan, Ye; Xi, Feng

2017-07-01

The phase transition of iron under shock compression has attracted much attention in recent decades because of its importance in fields such as condensed matter physics, geophysics, and metallurgy. At room temperature, the transition of iron from the α-phase (bcc) to the ɛ-phase (hpc) occurs at a stress of 13 GPa. At high temperature, a triple point followed by transformation to the γ-phase (fcc) is expected. However, the details of the high-temperature phase transitions of iron are still under debate. Here, we investigate the phase-transition behavior of polycrystalline iron under compression from room temperature to 820 K. The results show that the shock-induced phase transition is determined unequivocally from the measured three-wave-structure profiles, which clearly consist of an elastic wave, a plastic wave, and a phase-transition wave. The phase transition is temperature-dependent, with an average rate Δσtr/ΔT of -6.91 MPa/K below 700 K and -34.7 MPa/K at higher temperatures. The shock α-ɛ and α-γ phase boundaries intersect at 10.6 ± 0.53 GPa and 763 K, which agrees with the α-ɛ-γ triple point from early shock wave experiments and recent laser-heated diamond-anvil cell resistivity and in situ X-ray diffraction data but disagrees with the shock pressure-temperature phase diagram reported in 2009 by Zaretsky [J. Appl. Phys. 106, 023510 (2009)].

Investigating the ability of solar coronal shocks to accelerate solar energetic particles

NASA Astrophysics Data System (ADS)

Kwon, R. Y.; Vourlidas, A.

2017-12-01

We estimate the density compression ratio of shocks associated with coronal mass ejections (CMEs) and investigate whether they can accelerate solar energetic particles (SEPs). Using remote-sensing, multi-viewpoint coronagraphic observations, we have developed a method to extract the sheath electron density profiles along the shock normal and estimate the density compression ratio. Our method uses the ellipsoid model to derive the 3D geometry of the sheaths, including the line-of-sight (LOS) depth. The sheath density profiles along the shock normal are modeled with double-Gaussian functions, and the modeled densities are integrated along the LOSs to be compared with the observed brightness in STEREO COR2-Ahead. The upstream densities are derived from either the pB-inversion of the brightness in a pre-event image or an empirical model. We analyze two fast halo CMEs observed on 2011 March 7 and 2014 February 25 that are associated with SEP events detected by multiple spacecraft located over a broad range of heliolongitudes. We find that the density compression peaks around the CME nose and decreases at larger position angles. Interestingly, we find that the supercritical region extends over a large area of the shock and lasts longer (several tens of minutes) than past reports. This finding implies that CME shocks may be capable of accelerating energetic particles in the corona over extended spatial and temporal scales and may, therefore, be responsible for the wide longitudinal distribution of these particles in the inner heliosphere.

Fluid mechanics in fluids at rest.

PubMed

Brenner, Howard

2012-07-01

Using readily available experimental thermophoretic particle-velocity data it is shown, contrary to current teachings, that for the case of compressible flows independent dye- and particle-tracer velocity measurements of the local fluid velocity at a point in a flowing fluid do not generally result in the same fluid velocity measure. Rather, tracer-velocity equality holds only for incompressible flows. For compressible fluids, each type of tracer is shown to monitor a fundamentally different fluid velocity, with (i) a dye (or any other such molecular-tagging scheme) measuring the fluid's mass velocity v appearing in the continuity equation and (ii) a small, physicochemically and thermally inert, macroscopic (i.e., non-Brownian), solid particle measuring the fluid's volume velocity v(v). The term "compressibility" as used here includes not only pressure effects on density, but also temperature effects thereon. (For example, owing to a liquid's generally nonzero isobaric coefficient of thermal expansion, nonisothermal liquid flows are to be regarded as compressible despite the general perception of liquids as being incompressible.) Recognition of the fact that two independent fluid velocities, mass- and volume-based, are formally required to model continuum fluid behavior impacts on the foundations of contemporary (monovelocity) fluid mechanics. Included therein are the Navier-Stokes-Fourier equations, which are now seen to apply only to incompressible fluids (a fact well-known, empirically, to experimental gas kineticists). The findings of a difference in tracer velocities heralds the introduction into fluid mechanics of a general bipartite theory of fluid mechanics, bivelocity hydrodynamics [Brenner, Int. J. Eng. Sci. 54, 67 (2012)], differing from conventional hydrodynamics in situations entailing compressible flows and reducing to conventional hydrodynamics when the flow is incompressible, while being applicable to both liquids and gases.

A Multi-Mode Shock Tube for Investigation of Blast-Induced Traumatic Brain Injury

PubMed Central

Reneer, Dexter V.; Hisel, Richard D.; Hoffman, Joshua M.; Kryscio, Richard J.; Lusk, Braden T.

2011-01-01

Abstract Blast-induced mild traumatic brain injury (bTBI) has become increasingly common in recent military conflicts. The mechanisms by which non-impact blast exposure results in bTBI are incompletely understood. Current small animal bTBI models predominantly utilize compressed air-driven membrane rupture as their blast wave source, while large animal models use chemical explosives. The pressure-time signature of each blast mode is unique, making it difficult to evaluate the contributions of the different components of the blast wave to bTBI when using a single blast source. We utilized a multi-mode shock tube, the McMillan blast device, capable of utilizing compressed air- and compressed helium-driven membrane rupture, and the explosives oxyhydrogen and cyclotrimethylenetrinitramine (RDX, the primary component of C-4 plastic explosives) as the driving source. At similar maximal blast overpressures, the positive pressure phase of compressed air-driven blasts was longer, and the positive impulse was greater, than those observed for shockwaves produced by other driving sources. Helium-driven shockwaves more closely resembled RDX blasts, but by displacing air created a hypoxic environment within the shock tube. Pressure-time traces from oxyhydrogen-driven shockwaves were very similar those produced by RDX, although they resulted in elevated carbon monoxide levels due to combustion of the polyethylene bag used to contain the gases within the shock tube prior to detonation. Rats exposed to compressed air-driven blasts had more pronounced vascular damage than those exposed to oxyhydrogen-driven blasts of the same peak overpressure, indicating that differences in blast wave characteristics other than peak overpressure may influence the extent of bTBI. Use of this multi-mode shock tube in small animal models will enable comparison of the extent of brain injury with the pressure-time signature produced using each blast mode, facilitating evaluation of the blast wave components contributing to bTBI. PMID:21083431

A multi-mode shock tube for investigation of blast-induced traumatic brain injury.

PubMed

Reneer, Dexter V; Hisel, Richard D; Hoffman, Joshua M; Kryscio, Richard J; Lusk, Braden T; Geddes, James W

2011-01-01

Blast-induced mild traumatic brain injury (bTBI) has become increasingly common in recent military conflicts. The mechanisms by which non-impact blast exposure results in bTBI are incompletely understood. Current small animal bTBI models predominantly utilize compressed air-driven membrane rupture as their blast wave source, while large animal models use chemical explosives. The pressure-time signature of each blast mode is unique, making it difficult to evaluate the contributions of the different components of the blast wave to bTBI when using a single blast source. We utilized a multi-mode shock tube, the McMillan blast device, capable of utilizing compressed air- and compressed helium-driven membrane rupture, and the explosives oxyhydrogen and cyclotrimethylenetrinitramine (RDX, the primary component of C-4 plastic explosives) as the driving source. At similar maximal blast overpressures, the positive pressure phase of compressed air-driven blasts was longer, and the positive impulse was greater, than those observed for shockwaves produced by other driving sources. Helium-driven shockwaves more closely resembled RDX blasts, but by displacing air created a hypoxic environment within the shock tube. Pressure-time traces from oxyhydrogen-driven shockwaves were very similar those produced by RDX, although they resulted in elevated carbon monoxide levels due to combustion of the polyethylene bag used to contain the gases within the shock tube prior to detonation. Rats exposed to compressed air-driven blasts had more pronounced vascular damage than those exposed to oxyhydrogen-driven blasts of the same peak overpressure, indicating that differences in blast wave characteristics other than peak overpressure may influence the extent of bTBI. Use of this multi-mode shock tube in small animal models will enable comparison of the extent of brain injury with the pressure-time signature produced using each blast mode, facilitating evaluation of the blast wave components contributing to bTBI.

The Principal Hugoniot of Forsterite to 950 GPa

NASA Astrophysics Data System (ADS)

Root, Seth; Townsend, Joshua P.; Davies, Erik; Lemke, Raymond W.; Bliss, David E.; Fratanduono, Dayne E.; Kraus, Richard G.; Millot, Marius; Spaulding, Dylan K.; Shulenburger, Luke; Stewart, Sarah T.; Jacobsen, Stein B.

2018-05-01

Forsterite (Mg2SiO4) single crystals were shock compressed to pressures between 200 and 950 GPa using independent plate-impact steady shocks and laser-driven decaying shock compression experiments. Additionally, we performed density functional theory-based molecular dynamics to aid interpretation of the experimental data and to investigate possible phase transformations and phase separations along the Hugoniot. We show that the experimentally obtained Hugoniot cannot distinguish between a pure liquid Mg2SiO4 and an assemblage of solid MgO plus liquid magnesium silicate. The measured reflectivity is nonzero and increases with pressure, which implies that the liquid is a poor electrical conductor at low pressures and that the conductivity increases with pressure.

Shock formation and the ideal shape of ramp compression waves

NASA Astrophysics Data System (ADS)

Swift, Damian C.; Kraus, Richard G.; Loomis, Eric N.; Hicks, Damien G.; McNaney, James M.; Johnson, Randall P.

2008-12-01

We derive expressions for shock formation based on the local curvature of the flow characteristics during dynamic compression. Given a specific ramp adiabat, calculated for instance from the equation of state for a substance, the ideal nonlinear shape for an applied ramp loading history can be determined. We discuss the region affected by lateral release, which can be presented in compact form for the ideal loading history. Example calculations are given for representative metals and plastic ablators. Continuum dynamics (hydrocode) simulations were in good agreement with the algebraic forms. Example applications are presented for several classes of laser-loading experiment, identifying conditions where shocks are desired but not formed, and where long-duration ramps are desired.

Digital-computer normal shock position and restart control of a Mach 2.5 axisymmetric mixed-compression inlet

NASA Technical Reports Server (NTRS)

Neiner, G. H.; Cole, G. L.; Arpasi, D. J.

1972-01-01

Digital computer control of a mixed-compression inlet is discussed. The inlet was terminated with a choked orifice at the compressor face station to dynamically simulate a turbojet engine. Inlet diffuser exit airflow disturbances were used. A digital version of a previously tested analog control system was used for both normal shock and restart control. Digital computer algorithms were derived using z-transform and finite difference methods. Using a sample rate of 1000 samples per second, the digital normal shock and restart controls essentially duplicated the inlet analog computer control results. At a sample rate of 100 samples per second, the control system performed adequately but was less stable.

Introduction to Shock Waves and Shock Wave Research

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

Anderson, William Wyatt

2017-02-02

M-9 and a number of other organizations at LANL and elsewhere study materials in dynamic processes. Often, this is described as “shock wave research,” but in reality is broader than is implied by that term. Most of our work is focused on dynamic compression and associated phenomena, but you will find a wide variety of things we do that, while related, are not simple compression of materials, but involve a much richer variety of phenomena. This tutorial will introduce some of the underlying physics involved in this work, some of the more common types of phenomena we study, and commonmore » techniques. However, the list will not be exhaustive by any means.« less

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.

Assessment of the effects of azimuthal mode number perturbations upon the implosion processes of fluids in cylinders

NASA Astrophysics Data System (ADS)

Lindstrom, Michael

2017-06-01

Fluid instabilities arise in a variety of contexts and are often unwanted results of engineering imperfections. In one particular model for a magnetized target fusion reactor, a pressure wave is propagated in a cylindrical annulus comprised of a dense fluid before impinging upon a plasma and imploding it. Part of the success of the apparatus is a function of how axially-symmetric the final pressure pulse is upon impacting the plasma. We study a simple model for the implosion of the system to study how imperfections in the pressure imparted on the outer circumference grow due to geometric focusing. Our methodology entails linearizing the compressible Euler equations for mass and momentum conservation about a cylindrically symmetric problem and analysing the perturbed profiles at different mode numbers. The linearized system gives rise to singular shocks and through analysing the perturbation profiles at various times, we infer that high mode numbers are dampened through the propagation. We also study the Linear Klein-Gordon equation in the context of stability of linear cylindrical wave formation whereby highly oscillatory, bounded behaviour is observed in a far field solution.

Compressibility Effects on Particle-Fluid Interaction Force for Eulerian-Eulerian Simulations

NASA Astrophysics Data System (ADS)

Akiki, Georges; Francois, Marianne; Zhang, Duan

2017-11-01

Particle-fluid interaction forces are essential in modeling multiphase flows. Several models can be found in the literature based on empirical, numerical, and experimental results from various simplified flow conditions. Some of these models also account for finite Mach number effects. Using these models is relatively straightforward with Eulerian-Lagrangian calculations if the model for the total force on particles is used. In Eulerian-Eulerian simulations, however, there is the pressure gradient terms in the momentum equation for particles. For low Mach number flows, the pressure gradient force is negligible if the particle density is much greater than that of the fluid. For supersonic flows where a standing shock is present, even for a steady and uniform flow, it is unclear whether the significant pressure-gradient force should to be separated out from the particle force model. To answer this conceptual question, we perform single-sphere fully-resolved DNS simulations for a wide range of Mach numbers. We then examine whether the total force obtained from the DNS can be categorized into well-established models, such as the quasi-steady, added-mass, pressure-gradient, and history forces. Work sponsored by Advanced Simulation and Computing (ASC) program of NNSA and LDRD-CNLS of LANL.

An Approach Toward Synthesis of Bridgmanite in Dynamic Compression Experiments

NASA Astrophysics Data System (ADS)

Reppart, J. J.

2015-12-01

Bridgmanite occurs in heavily shocked meteorites and provides a useful constraint on pressure-temperature conditions during shock-metamorphism. Its occurrence also provides constraints on the shock release path. Shock-release and shock duration are important parameters in estimating the size of impactors that generate the observed shock metamorphic record. Thus, it is timely to examine if bridgmanite can be synthesized in dynamic compression experiments with the goal of establishing a correlation between shock duration and grainsize. Up to now only one high pressure polymorph of an Mg-silicate has been synthesized AND recovered in a shock experiment (wadsleyite). Therefore, it is not given that shock synthesis of bridgmanite is possible. This project started recently, so we present an outline of shock experiment designs and potentially results from the first experiments. FUNDING ACKNOWLEDGMENT UNLV HiPSEC: This research was sponsored (or sponsored in part) by the National Nuclear Security Administration under the Stewardship Science Academic Alliances program through DOE Cooperative Agreement #DE-NA0001982. HPCAT: "[Portions of this work were]/[This work was] performed at HPCAT (Sector 16), Advanced Photon Source (APS), Argonne National Laboratory. HPCAT operations are supported by DOE-NNSA under Award No. DE-NA0001974 and DOE-BES under Award No. DE-FG02-99ER45775, with partial instrumentation funding by NSF. APS is supported by DOE-BES, under Contract No. DE-AC02-06CH11357."

Modeling Compressibility Effects in High-Speed Turbulent Flows

NASA Technical Reports Server (NTRS)

Sarkar, S.

2004-01-01

Man has strived to make objects fly faster, first from subsonic to supersonic and then to hypersonic speeds. Spacecraft and high-speed missiles routinely fly at hypersonic Mach numbers, M greater than 5. In defense applications, aircraft reach hypersonic speeds at high altitude and so may civilian aircraft in the future. Hypersonic flight, while presenting opportunities, has formidable challenges that have spurred vigorous research and development, mainly by NASA and the Air Force in the USA. Although NASP, the premier hypersonic concept of the eighties and early nineties, did not lead to flight demonstration, much basic research and technology development was possible. There is renewed interest in supersonic and hypersonic flight with the HyTech program of the Air Force and the Hyper-X program at NASA being examples of current thrusts in the field. At high-subsonic to supersonic speeds, fluid compressibility becomes increasingly important in the turbulent boundary layers and shear layers associated with the flow around aerospace vehicles. Changes in thermodynamic variables: density, temperature and pressure, interact strongly with the underlying vortical, turbulent flow. The ensuing changes to the flow may be qualitative such as shocks which have no incompressible counterpart, or quantitative such as the reduction of skin friction with Mach number, large heat transfer rates due to viscous heating, and the dramatic reduction of fuel/oxidant mixing at high convective Mach number. The peculiarities of compressible turbulence, so-called compressibility effects, have been reviewed by Fernholz and Finley. Predictions of aerodynamic performance in high-speed applications require accurate computational modeling of these "compressibility effects" on turbulence. During the course of the project we have made fundamental advances in modeling the pressure-strain correlation and developed a code to evaluate alternate turbulence models in the compressible shear layer.

Onset of turbulence in accelerated high-Reynolds-number flow

NASA Astrophysics Data System (ADS)

Zhou, Ye; Robey, Harry F.; Buckingham, Alfred C.

2003-05-01

A new criterion, flow drive time, is identified here as a necessary condition for transition to turbulence in accelerated, unsteady flows. Compressible, high-Reynolds-number flows initiated, for example, in shock tubes, supersonic wind tunnels with practical limitations on dimensions or reservoir capacity, and high energy density pulsed laser target vaporization experimental facilities may not provide flow duration adequate for turbulence development. In addition, for critical periods of the overall flow development, the driving background flow is often unsteady in the experiments as well as in the physical flow situations they are designed to mimic. In these situations transition to fully developed turbulence may not be realized despite achievement of flow Reynolds numbers associated with or exceeding stationary flow transitional criteria. Basically our transitional criterion and prediction procedure extends to accelerated, unsteady background flow situations the remarkably universal mixing transition criterion proposed by Dimotakis [P. E. Dimotakis, J. Fluid Mech. 409, 69 (2000)] for stationary flows. This provides a basis for the requisite space and time scaling. The emphasis here is placed on variable density flow instabilities initiated by constant acceleration Rayleigh-Taylor instability (RTI) or impulsive (shock) acceleration Richtmyer-Meshkov instability (RMI) or combinations of both. The significant influences of compressibility on these developing transitional flows are discussed with their implications on the procedural model development. A fresh perspective for predictive modeling and design of experiments for the instability growth and turbulent mixing transitional interval is provided using an analogy between the well-established buoyancy-drag model with applications of a hierarchy of single point turbulent transport closure models. Experimental comparisons with the procedural results are presented where use is made of three distinctly different types of acceleration driven instability experiments: (1) classical, relatively low speed, constant acceleration RTI experiments; (2) shock tube, shockwave driven RMI flow mixing experiments; (3) laser target vaporization RTI and RMI mixing experiments driven at very high energy density. These last named experiments are of special interest as they provide scaleable flow conditions simulating those of astrophysical magnitude such as shock-driven hydrodynamic mixing in supernova evolution research.

Iterative spectral methods and spectral solutions to compressible flows

NASA Technical Reports Server (NTRS)

Hussaini, M. Y.; Zang, T. A.

1982-01-01

A spectral multigrid scheme is described which can solve pseudospectral discretizations of self-adjoint elliptic problems in O(N log N) operations. An iterative technique for efficiently implementing semi-implicit time-stepping for pseudospectral discretizations of Navier-Stokes equations is discussed. This approach can handle variable coefficient terms in an effective manner. Pseudospectral solutions of compressible flow problems are presented. These include one dimensional problems and two dimensional Euler solutions. Results are given both for shock-capturing approaches and for shock-fitting ones.

TOWN HALL MEETING-SCCM 2009

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

Eggert, J.; Ryan, S. J.; Ramesh, K. T.

2009-12-28

The following article contains the summary of the discussion held at the Shock Compression of Condensed Matter Town Hall Meeting. This was held on Tuesday afternoon of the meeting and attracted 100+ attendees. This meeting, chaired by John Eggert, was planned to introduce challenges in selected topics relevant to shock wave science. The three subjects and speakers were: space research introduced by Shannon Ryan, nanotechnology presented by Kaliat T. Ramesh, and compression tools delivered by Dave Funk. After each presentation there were a number of questions.

Shock-induced bubble jetting into a viscous fluid with application to tissue injury in shock-wave lithotripsy.

PubMed

Freund, J B; Shukla, R K; Evan, A P

2009-11-01

Shock waves in liquids are known to cause spherical gas bubbles to rapidly collapse and form strong re-entrant jets in the direction of the propagating shock. The interaction of these jets with an adjacent viscous liquid is investigated using finite-volume simulation methods. This configuration serves as a model for tissue injury during shock-wave lithotripsy, a medical procedure to remove kidney stones. In this case, the viscous fluid provides a crude model for the tissue. It is found that for viscosities comparable to what might be expected in tissue, the jet that forms upon collapse of a small bubble fails to penetrate deeply into the viscous fluid "tissue." A simple model reproduces the penetration distance versus viscosity observed in the simulations and leads to a phenomenological model for the spreading of injury with multiple shocks. For a reasonable selection of a single efficiency parameter, this model is able to reproduce in vivo observations of an apparent 1000-shock threshold before wide-spread tissue injury occurs in targeted kidneys and the approximate extent of this injury after a typical clinical dose of 2000 shock waves.

Shock-induced bubble jetting into a viscous fluid with application to tissue injury in shock-wave lithotripsy

PubMed Central

Freund, J. B.; Shukla, R. K.; Evan, A. P.

2009-01-01

Shock waves in liquids are known to cause spherical gas bubbles to rapidly collapse and form strong re-entrant jets in the direction of the propagating shock. The interaction of these jets with an adjacent viscous liquid is investigated using finite-volume simulation methods. This configuration serves as a model for tissue injury during shock-wave lithotripsy, a medical procedure to remove kidney stones. In this case, the viscous fluid provides a crude model for the tissue. It is found that for viscosities comparable to what might be expected in tissue, the jet that forms upon collapse of a small bubble fails to penetrate deeply into the viscous fluid “tissue.” A simple model reproduces the penetration distance versus viscosity observed in the simulations and leads to a phenomenological model for the spreading of injury with multiple shocks. For a reasonable selection of a single efficiency parameter, this model is able to reproduce in vivo observations of an apparent 1000-shock threshold before wide-spread tissue injury occurs in targeted kidneys and the approximate extent of this injury after a typical clinical dose of 2000 shock waves. PMID:19894850

Compressible Vortex Ring

NASA Astrophysics Data System (ADS)

Elavarasan, Ramasamy; Arakeri, Jayawant; Krothapalli, Anjaneyulu

1999-11-01

The interaction of a high-speed vortex ring with a shock wave is one of the fundamental issues as it is a source of sound in supersonic jets. The complex flow field induced by the vortex alters the propagation of the shock wave greatly. In order to understand the process, a compressible vortex ring is studied in detail using Particle Image Velocimetry (PIV) and shadowgraphic techniques. The high-speed vortex ring is generated from a shock tube and the shock wave, which precedes the vortex, is reflected back by a plate and made to interact with the vortex. The shadowgraph images indicate that the reflected shock front is influenced by the non-uniform flow induced by the vortex and is decelerated while passing through the vortex. It appears that after the interaction the shock is "split" into two. The PIV measurements provided clear picture about the evolution of the vortex at different time interval. The centerline velocity traces show the maximum velocity to be around 350 m/s. The velocity field, unlike in incompressible rings, contains contributions from both the shock and the vortex ring. The velocity distribution across the vortex core, core diameter and circulation are also calculated from the PIV data.

Nanosecond formation of diamond and lonsdaleite by shock compression of graphite.

PubMed

Kraus, D; Ravasio, A; Gauthier, M; Gericke, D O; Vorberger, J; Frydrych, S; Helfrich, J; Fletcher, L B; Schaumann, G; Nagler, B; Barbrel, B; Bachmann, B; Gamboa, E J; Göde, S; Granados, E; Gregori, G; Lee, H J; Neumayer, P; Schumaker, W; Döppner, T; Falcone, R W; Glenzer, S H; Roth, M

2016-03-14

The shock-induced transition from graphite to diamond has been of great scientific and technological interest since the discovery of microscopic diamonds in remnants of explosively driven graphite. Furthermore, shock synthesis of diamond and lonsdaleite, a speculative hexagonal carbon polymorph with unique hardness, is expected to happen during violent meteor impacts. Here, we show unprecedented in situ X-ray diffraction measurements of diamond formation on nanosecond timescales by shock compression of pyrolytic as well as polycrystalline graphite to pressures from 19 GPa up to 228 GPa. While we observe the transition to diamond starting at 50 GPa for both pyrolytic and polycrystalline graphite, we also record the direct formation of lonsdaleite above 170 GPa for pyrolytic samples only. Our experiment provides new insights into the processes of the shock-induced transition from graphite to diamond and uniquely resolves the dynamics that explain the main natural occurrence of the lonsdaleite crystal structure being close to meteor impact sites.

Nanosecond formation of diamond and lonsdaleite by shock compression of graphite

DOE PAGES

Kraus, D.; Ravasio, A.; Gauthier, M.; ...

2016-03-14

The shock-induced transition from graphite to diamond has been of great scientific and technological interest since the discovery of microscopic diamonds in remnants of explosively driven graphite. Furthermore, shock synthesis of diamond and lonsdaleite, a speculative hexagonal carbon polymorph with unique hardness, is expected to happen during violent meteor impacts. Here, we show unprecedented in situ X-ray diffraction measurements of diamond formation on nanosecond timescales by shock compression of pyrolytic as well as polycrystalline graphite to pressures from 19 GPa up to 228 GPa. While we observe the transition to diamond starting at 50 GPa for both pyrolytic and polycrystallinemore » graphite, we also record the direct formation of lonsdaleite above 170 GPa for pyrolytic samples only. In conclusion, our experiment provides new insights into the processes of the shock-induced transition from graphite to diamond and uniquely resolves the dynamics that explain the main natural occurrence of the lonsdaleite crystal structure being close to meteor impact sites.« less

Investigation of Inlet Control Parameters for an External-internal-compression Inlet from Mach 2.1 to 3.0

NASA Technical Reports Server (NTRS)

Anderson, B. H.; Bowditch, D. N.

1958-01-01

Investigation of the control parameters of an external-internal compression inlet indicates that the cowl-lip shock provides a signal to position the spike and to start the inlet over a Mach number range from 2.1 to 3.0. Use of a single fixed probe position to control the spike over the range of conditions resulted in a 3.7-count loss in total-pressure recovery at Mach 3.0 and 0 deg angle of attack. Three separate shock-sensing-probe positions were required to set the spike for peak recovery from Mach 2.1 to 3.0 and angles of attack from 0 deg to 6 deg. When the inlet was unstarted, an erroneous signal was obtained from the normal-shock control through most of the starting cycle that prevented the inlet from starting. Therefore, it was necessary to over-ride the normal-shock control signal and not allow the control to position the terminal shock until the spike was positioned.

Imaging shock waves in diamond with both high temporal and spatial resolution at an XFEL

DOE PAGES

Schropp, Andreas; Hoppe, Robert; Meier, Vivienne; ...

2015-06-18

The advent of hard x-ray free-electron lasers (XFELs) has opened up a variety of scientific opportunities in areas as diverse as atomic physics, plasma physics, nonlinear optics in the x-ray range, and protein crystallography. In this article, we access a new field of science by measuring quantitatively the local bulk properties and dynamics of matter under extreme conditions, in this case by using the short XFEL pulse to image an elastic compression wave in diamond. The elastic wave was initiated by an intense optical laser pulse and was imaged at different delay times after the optical pump pulse using magnifiedmore » x-ray phase-contrast imaging. The temporal evolution of the shock wave can be monitored, yielding detailed information on shock dynamics, such as the shock velocity, the shock front width, and the local compression of the material. The method provides a quantitative perspective on the state of matter in extreme conditions.« less

Imaging Shock Waves in Diamond with Both High Temporal and Spatial Resolution at an XFEL.

PubMed

Schropp, Andreas; Hoppe, Robert; Meier, Vivienne; Patommel, Jens; Seiboth, Frank; Ping, Yuan; Hicks, Damien G; Beckwith, Martha A; Collins, Gilbert W; Higginbotham, Andrew; Wark, Justin S; Lee, Hae Ja; Nagler, Bob; Galtier, Eric C; Arnold, Brice; Zastrau, Ulf; Hastings, Jerome B; Schroer, Christian G

2015-06-18

The advent of hard x-ray free-electron lasers (XFELs) has opened up a variety of scientific opportunities in areas as diverse as atomic physics, plasma physics, nonlinear optics in the x-ray range, and protein crystallography. In this article, we access a new field of science by measuring quantitatively the local bulk properties and dynamics of matter under extreme conditions, in this case by using the short XFEL pulse to image an elastic compression wave in diamond. The elastic wave was initiated by an intense optical laser pulse and was imaged at different delay times after the optical pump pulse using magnified x-ray phase-contrast imaging. The temporal evolution of the shock wave can be monitored, yielding detailed information on shock dynamics, such as the shock velocity, the shock front width, and the local compression of the material. The method provides a quantitative perspective on the state of matter in extreme conditions.

The Simultaneous Combination of Phase Contrast Imaging with In Situ X-ray diffraction from Shock Compressed Matter

NASA Astrophysics Data System (ADS)

McBride, Emma Elizabeth; Seiboth, Frank; Cooper, Leora; Frost, Mungo; Goede, Sebastian; Harmand, Marion; Levitan, Abe; McGonegle, David; Miyanishi, Kohei; Ozaki, Norimasa; Roedel, Melanie; Sun, Peihao; Wark, Justin; Hastings, Jerry; Glenzer, Siegfried; Fletcher, Luke

2017-10-01

Here, we present the simultaneous combination of phase contrast imaging (PCI) techniques with in situ X-ray diffraction to investigate multiple-wave features in laser-driven shock-compressed germanium. Experiments were conducted at the Matter at Extreme Conditions end station at the LCLS, and measurements were made perpendicular to the shock propagation direction. PCI allows one to take femtosecond snapshots of magnified real-space images of shock waves as they progress though matter. X-ray diffraction perpendicular to the shock propagation direction provides the opportunity to isolate and identify different waves and determine the crystal structure unambiguously. Here, we combine these two powerful techniques simultaneously, by using the same Be lens setup to focus the fundamental beam at 8.2 keV to a size of 1.5 mm on target for PCI and the 3rd harmonic at 24.6 keV to a spot size of 2 um on target for diffraction.

Dynamic loads on human and animal surrogates at different test locations in compressed-gas-driven shock tubes

NASA Astrophysics Data System (ADS)

Alay, E.; Skotak, M.; Misistia, A.; Chandra, N.

2018-01-01

Dynamic loads on specimens in live-fire conditions as well as at different locations within and outside compressed-gas-driven shock tubes are determined by both static and total blast overpressure-time pressure pulses. The biomechanical loading on the specimen is determined by surface pressures that combine the effects of static, dynamic, and reflected pressures and specimen geometry. Surface pressure is both space and time dependent; it varies as a function of size, shape, and external contour of the specimens. In this work, we used two sets of specimens: (1) anthropometric dummy head and (2) a surrogate rodent headform instrumented with pressure sensors and subjected them to blast waves in the interior and at the exit of the shock tube. We demonstrate in this work that while inside the shock tube the biomechanical loading as determined by various pressure measures closely aligns with live-fire data and shock wave theory, significant deviations are found when tests are performed outside.

Shock induced reaction of Ni/Al nanopowder mixture.

PubMed

Meng, C M; Wei, J J; Chen, Q Y

2012-11-01

Nanopowder Ni/Al mixture (mixed in Al:Ni = 2:1 stoichiometry) was shock compressed by employing single and two-stage light gas gun. The particle size of Al and Ni are 100-200 nm and 50-70 nm respectively, morphologies of Al and Ni are sphere like either. Recovered product was characterized by scanning electron microscope (SEM) and X-ray diffraction (XRD) analysis. According to the XRD spectrum, the mixed powder undergo complete reaction under shock compression, reaction product consist of Ni2Al3, NiAl and corundum structure Al2O3 compound. Grain size of Ni-Al compound is less than 100 nm. With the shock pressure increasing, the ratio of Ni2Al3 decreased obviously. The corundum crystal size is 400-500 nm according to the SEM observation. The results of shock recovery experiments and analysis show that the threshold pressure for reaction of nano size powder Ni/Al mixture is much less than that of micro size powder.

Nanosecond formation of diamond and lonsdaleite by shock compression of graphite

PubMed Central

Kraus, D.; Ravasio, A.; Gauthier, M.; Gericke, D. O.; Vorberger, J.; Frydrych, S.; Helfrich, J.; Fletcher, L. B.; Schaumann, G.; Nagler, B.; Barbrel, B.; Bachmann, B.; Gamboa, E. J.; Göde, S.; Granados, E.; Gregori, G.; Lee, H. J.; Neumayer, P.; Schumaker, W.; Döppner, T.; Falcone, R. W.; Glenzer, S. H.; Roth, M.

2016-01-01

The shock-induced transition from graphite to diamond has been of great scientific and technological interest since the discovery of microscopic diamonds in remnants of explosively driven graphite. Furthermore, shock synthesis of diamond and lonsdaleite, a speculative hexagonal carbon polymorph with unique hardness, is expected to happen during violent meteor impacts. Here, we show unprecedented in situ X-ray diffraction measurements of diamond formation on nanosecond timescales by shock compression of pyrolytic as well as polycrystalline graphite to pressures from 19 GPa up to 228 GPa. While we observe the transition to diamond starting at 50 GPa for both pyrolytic and polycrystalline graphite, we also record the direct formation of lonsdaleite above 170 GPa for pyrolytic samples only. Our experiment provides new insights into the processes of the shock-induced transition from graphite to diamond and uniquely resolves the dynamics that explain the main natural occurrence of the lonsdaleite crystal structure being close to meteor impact sites. PMID:26972122

Computational analysis of hypersonic flows past elliptic-cone waveriders

NASA Technical Reports Server (NTRS)

Yoon, Bok-Hyun; Rasmussen, Maurice L.

1991-01-01

A comprehensive study for the inviscid numerical calculation of the hypersonic flow past a class of elliptic-cone derived waveriders is presented. The theoretical background associated with hypersonic small-disturbance theory (HSDT) is reviewed. Several approximation formulas for the waverider compression surface are established. A CFD algorithm is used to calculate flow fields for the on-design case and a variety of off-design cases. The results are compared with HSDT, experiment, and other available CFD results. For the waverider shape used in previous investigations, the bow shock for the on-design condition stands off from the leading-edge tip of the waverider. It was found that this occurs because the tip was too thick according to the approximating shape formula that was used to describe the compression surface. When this was corrected, the bow shock became closer to attached as it should be. At Mach numbers greater than the design condition, a lambda-shock configuration develops near the tip of the compression surface. At negative angles of attack, other complicated shock patterns occur near the leading-edge tip. These heretofore unknown flow patterns show the power and utility of CFD for investigating novel hypersonic configurations such as waveriders.

Plasma ion stratification by weak planar shocks

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

Simakov, Andrei N.; Keenan, Brett D.; Taitano, William T.

We derive fluid equations for describing steady-state planar shocks of a moderate strength (0 < M - 1 ≲ 1 with M the shock Mach number) propagating through an unmagnetized quasineutral collisional plasma comprising two separate ion species. In addition to the standard fluid shock quantities, such as the total mass density, mass-flow velocity, and electron and average ion temperatures, the equations describe shock stratification in terms of variations in the relative concentrations and temperatures of the two ion species along the shock propagation direction. We have solved these equations analytically for weak shocks (0 < M - 1 <

Plasma ion stratification by weak planar shocks

NASA Astrophysics Data System (ADS)

Simakov, Andrei N.; Keenan, Brett D.; Taitano, William T.; Chacón, Luis

2017-09-01

We derive fluid equations for describing steady-state planar shocks of a moderate strength ( 0

Plasma ion stratification by weak planar shocks

DOE PAGES

Simakov, Andrei N.; Keenan, Brett D.; Taitano, William T.; ...

2017-08-01

We derive fluid equations for describing steady-state planar shocks of a moderate strength (0 < M - 1 ≲ 1 with M the shock Mach number) propagating through an unmagnetized quasineutral collisional plasma comprising two separate ion species. In addition to the standard fluid shock quantities, such as the total mass density, mass-flow velocity, and electron and average ion temperatures, the equations describe shock stratification in terms of variations in the relative concentrations and temperatures of the two ion species along the shock propagation direction. We have solved these equations analytically for weak shocks (0 < M - 1 <

Comparison of cell centered and cell vertex scheme in the calculation of high speed compressible flows

NASA Astrophysics Data System (ADS)

Rahman, Syazila; Yusoff, Mohd. Zamri; Hasini, Hasril

2012-06-01

This paper describes the comparison between the cell centered scheme and cell vertex scheme in the calculation of high speed compressible flow properties. The calculation is carried out using Computational Fluid Dynamic (CFD) in which the mass, momentum and energy equations are solved simultaneously over the flow domain. The geometry under investigation consists of a Binnie and Green convergent-divergent nozzle and structured mesh scheme is implemented throughout the flow domain. The finite volume CFD solver employs second-order accurate central differencing scheme for spatial discretization. In addition, the second-order accurate cell-vertex finite volume spatial discretization is also introduced in this case for comparison. The multi-stage Runge-Kutta time integration is implemented for solving a set of non-linear governing equations with variables stored at the vertices. Artificial dissipations used second and fourth order terms with pressure switch to detect changes in pressure gradient. This is important to control the solution stability and capture shock discontinuity. The result is compared with experimental measurement and good agreement is obtained for both cases.

On a Heat Exchange Problem under Sharply Changing External Conditions

NASA Astrophysics Data System (ADS)

Khishchenko, K. V.; Charakhch'yan, A. A.; Shurshalov, L. V.

2018-02-01

The heat exchange problem between carbon particles and an external environment (water) is stated and investigated based on the equations of heat conducting compressible fluid. The environment parameters are supposed to undergo large and fast variations. In the time of about 100 μs, the temperature of the environment first increases from the normal one to 2400 K, is preserved at this level for about 60 μs, and then decreases to 300 K during approximately 50 μs. At the same periods of time, the pressure of the external environment increases from the normal one to 67 GPa, is preserved at this level, and then decreases to zero. Under such external conditions, the heating of graphite particles of various sizes, their phase transition to the diamond phase, and the subsequent unloading and cooling almost to the initial values of the pressure and temperature without the reverse transition from the diamond to the graphite phase are investigated. Conclusions about the maximal size of diamond particles that can be obtained in experiments on the shock compression of the mixture of graphite with water are drawn.

Association of day 4 cumulative fluid balance with mortality in critically ill patients with influenza: A multicenter retrospective cohort study in Taiwan.

PubMed

Chao, Wen-Cheng; Tseng, Chien-Hua; Chien, Ying-Chun; Sheu, Chau-Chyun; Tsai, Ming-Ju; Fang, Wen-Feng; Chen, Yu-Mu; Kao, Kuo-Chin; Hu, Han-Chung; Perng, Wann-Cherng; Yang, Kuang-Yao; Chen, Wei-Chih; Liang, Shinn-Jye; Wu, Chieh-Liang; Wang, Hao-Chien; Chan, Ming-Cheng

2018-01-01

Fluid balance is a fundamental management of patients with sepsis, and this study aimed to investigate the impact of cumulative fluid balance on critically ill patients with influenza admitted to an intensive care unit (ICU). This multicenter retrospective cohort study was conducted by the Taiwan Severe Influenza Research Consortium (TSIRC) which includes eight medical centers. Patients with virology-proven influenza infection admitted to ICUs between October 2015 and March 2016 were included for analysis. A total of 296 patients were enrolled (mean age: 61.4±15.6 years; 62.8% men), and 92.2% (273/296) of them required mechanical ventilation. In the survivors, the daily fluid balance was positive from day 1 to day 3, and then gradually became negative from day 4 to day 7, whereas daily fluid balance was continuously positive in the non-survivors. Using the cumulative fluid balance from day 1-4 as a cut-off point, we found that a negative cumulative day 1-4 fluid balance was associated with a lower 30-day mortality rate (log-rank test, P = 0.003). To evaluate the impact of shock on this association, we divided the patients into shock and non-shock groups. The positive correlation between negative day 1-4 fluid balance and mortality was significant in the non-shock group (log-rank test, P = 0.008), but not in the shock group (log-rank test, P = 0.396). In a multivariate Cox proportional hazard regression model adjusted for age, sex, cerebrovascular disease, and PaO2/FiO2, day 1-4 fluid balance was independently associated with a higher 30-day mortality rate (aHR 1.088, 95% CI: 1.007-1.174). A negative day 1-4 cumulative fluid balance was associated with a lower mortality rate in critically ill patients with influenza. Our findings indicate the critical role of conservative fluid strategy in the management of patients with complicated influenza.

Heat transfer head for a Stirling cycle machine

NASA Technical Reports Server (NTRS)

Emigh, Stuart G. (Inventor); Noble, Jack E. (Inventor); Lehmann, Gregory A. (Inventor)

1991-01-01

A common heat acceptor is provided between opposed displacers in a Stirling cycle machine. It includes two sets of open channels in separate fluid communications with the expansion spaces of the receptive cyclinders. The channels confine movement of working fluid in separate paths that extend between the expansion space of one cylinder and the compression space of the other. The method for operating the machine involves alternatively directing working fluid from the expansion space of each cylinder in a fluid path leading to the compression space of the other cylinder and from the compression space of each cylinder in a fluid path leading to the expansion space of the other cylinder.

Modeling of High-Velocity Flows in ITAM Impulse Facilities

DTIC Science & Technology

2010-04-01

up to 150 ms; Adiabatic compression wind tunnels up to 100 ms; Shock tubes... shock tubes. Basic and applied aerodynamic research has been performed in these wind tunnels in the range of Mach numbers М = 6 20 for many years...passage of a shock wave propagating over a cold rarefied gas filling the wind tunnel . When the gas heated in the shock wave (plug) passes around the

Time-resolved light emission of a, c, and r-cut sapphires shock-compressed to 65 GPa

NASA Astrophysics Data System (ADS)

Liu, Q. C.; Zhou, X. M.

2018-04-01

To investigate light emission and dynamic deformation behaviors, sapphire (single crystal Al2O3) samples with three crystallographic orientations (a, c, and r-cut) were shock-compressed by the planar impact method, with final stress ranges from 47 to 65 GPa. Emission radiance and velocity versus time profiles were simultaneously measured with a fast pyrometer and a Doppler pin system in each experiment. Wave profile results show anisotropic elastic-plastic transitions, which confirm the literature observations. Under final shock stress of about 52 GPa, lower emission intensity is observed in the r-cut sample, in agreement with the previous report in the literature. When final shock stress increases to 57 GPa and 65 GPa, spectral radiance histories of the r-cut show two stages of distinct features. In the first stage, the emission intensity of r-cut is lower than those of the other two, which agrees with the previous report in the literature. In the second stage, spectral radiance of r-cut increases with time at much higher rate and it finally peaks over those of the a and c-cut. These observations (conversion of intensified emission in the r-cut) may indicate activation of a second slip system and formation of shear bands which are discussed with the resolved shear stress calculations for the slip systems in each of the three cuts under shock compression.

Micro-Ramps for External Compression Low-Boom Inlets

NASA Technical Reports Server (NTRS)

Rybalko, Michael; Loth, Eric; Chima, Rodrick V.; Hirt, Stefanie M.; DeBonis, James R.

2010-01-01

The application of vortex generators for flow control in an external compression, axisymmetric, low-boom concept inlet was investigated using RANS simulations with three-dimensional (3-D), structured, chimera (overset) grids and the WIND-US code. The low-boom inlet design is based on previous scale model 1- by 1-ft wind tunnel tests and features a zero-angle cowl and relaxed isentropic compression centerbody spike, resulting in defocused oblique shocks and a weak terminating normal shock. Validation of the methodology was first performed for micro-ramps in supersonic flow on a flat plate with and without oblique shocks. For the inlet configuration, simulations with several types of vortex generators were conducted for positions both upstream and downstream of the terminating normal shock. The performance parameters included incompressible axisymmetric shape factor, separation area, inlet pressure recovery, and massflow ratio. The design of experiments (DOE) methodology was used to select device size and location, analyze the resulting data, and determine the optimal choice of device geometry. The optimum upstream configuration was found to substantially reduce the post-shock separation area but did not significantly impact recovery at the aerodynamic interface plane (AIP). Downstream device placement allowed for fuller boundary layer velocity profiles and reduced distortion. This resulted in an improved pressure recovery and massflow ratio at the AIP compared to the baseline solid-wall configuration.

Shock Compression of Liquid Noble Gases to Multi-Mbar Pressures

NASA Astrophysics Data System (ADS)

Root, Seth

2011-10-01

The high pressure - high temperature behavior of noble gases is of considerable interest because of their use in z-pinch liners for fusion studies and for understanding astrophysical and planetary evolution. However, our understanding of the equation of state (EOS) of the noble gases at extreme conditions is limited. A prime example of this is the liquid xenon Hugoniot. Previous EOS models rapidly diverged on the Hugoniot above 1 Mbar because of differences in the treatment of the electronic contribution to the free energy. Similar divergences are observed for krypton EOS. Combining shock compression experiments and density functional theory (DFT) simulations, we can determine the thermo-physical behavior of matter under extreme conditions. The experimental and DFT results have been instrumental to recent developments in planetary astrophysics and inertial confinement fusion. Shock compression experiments are performed using Sandia's Z-Accelerator to determine the Hugoniot of liquid xenon and krypton in the Mbar regime. Under strong pressure, krypton and xenon undergo an insulator to metal transition. In the metallic state, the shock front becomes reflective allowing for a direct measurement of the sample's shock velocity using laser interferometry. The Hugoniot state is determined using a Monte Carlo analysis method that accounts for systematic error in the standards and for correlations. DFT simulations at these extreme conditions show good agreement with the experimental data - demonstrating the attention to detail required for dealing with elements with relativistic core states and d-state electrons. The results from shock compression experiments and DFT simulations are presented for liquid xenon to 840 GPa and for liquid krypton to 800 GPa, decidedly increasing the range of known behavior of both gases. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Company, for the U. S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

Fluid administration in severe sepsis and septic shock, patterns and outcomes: an analysis of a large national database.

PubMed

Marik, Paul E; Linde-Zwirble, Walter T; Bittner, Edward A; Sahatjian, Jennifer; Hansell, Douglas

2017-05-01

The optimal strategy of fluid resuscitation in the early hours of severe sepsis and septic shock is controversial, with both an aggressive and conservative approach being recommended. We used the 2013 Premier Hospital Discharge database to analyse the administration of fluids on the first ICU day, in 23,513 patients with severe sepsis and septic shock, who were admitted to an ICU from the emergency department. Day 1 fluid was grouped into categories 1 L wide, starting with 1-1.99 L up to ≥9 L, to examine the effect of day 1 fluids on patient mortality. We built binary response models for hospital mortality and the propensity for receiving more than 5 L of fluids on day 1, using patient age and acute conditions present on admission. Patients were grouped by the requirement for mechanical ventilation and the presence or absence of shock. We assessed trends in the difference between actual and expected mortality, in the low fluid range (1-5 L day 1 fluids) and the high fluid range (5 to ≥9 L day 1 fluids) categories, using weighted linear regression controlling for the effects of sample size and variation within the day 1 fluid category. Day 1 fluid administration averaged 4.4 L being lowest in the group with no mechanical ventilation and no shock (3.6 L) and highest (5.4 L) in the group receiving mechanical ventilation and in shock. The administration of day 1 fluids was remarkably consistent on the basis of hospital size, teaching status, rural/urban location, and region of the country. The hospital mortality in the entire cohort was 25.8%, with a mean ICU and hospital length of stay of 5.1 and 9.1 days, respectively. In the entire cohort, low volume resuscitation (1-4.99 L) was associated with a small but significant reduction in mortality, of -0.7% per litre (95% CI -1.0%, -0.4%; p = 0.02). However, in patients receiving high volume resuscitation (5 to ≥9 L), the mortality increased by 2.3% (95% CI 2.0, 2.5%; p = 0.0003) for each additional litre above 5 L. Total hospital cost increased by $999 for each litre of fluid above 5 L (adjusted R 2  = 92.7%, p = 0.005). The mean amount of fluid administered to patients with severe sepsis and septic shock in the USA during the first ICU day is less than that recommended by the Surviving Sepsis Campaign guidelines. The administration of more than 5 L of fluid during the first ICU day is associated with a significantly increased risk of death and significantly higher hospital costs.

Improvement of pump tubes for gas guns and shock tube drivers

NASA Technical Reports Server (NTRS)

Bogdanoff, D. W.

1990-01-01

In a pump tube, a gas is mechanically compressed, producing very high pressures and sound speeds. The intensely heated gas produced in such a tube can be used to drive light gas guns and shock tubes. Three concepts are presented that have the potential to allow substantial reductions in the size and mass of the pump tube to be achieved. The first concept involves the use of one or more diaphragms in the pump tube, thus replacing a single compression process by multiple, successive compressions. The second concept involves a radical reduction in the length-to-diameter ratio of the pump tube and the pump tube piston. The third concept involves shock heating of the working gas by high explosives in a cyclindrical geometry reusable device. Preliminary design analyses are performed on all three concepts and they appear to be quite feasible. Reductions in the length and mass of the pump tube by factors up to about 11 and about 7, respectively, are predicted, relative to a benchmark conventional pump tube.

Flow speed of the ablation vapors generated during laser drilling of CFRP with a continuous-wave laser beam

NASA Astrophysics Data System (ADS)

Faas, S.; Freitag, C.; Boley, S.; Berger, P.; Weber, R.; Graf, T.

2017-03-01

The hot plume of ablation products generated during the laser drilling process of carbon fiber reinforced plastics (CFRP) with a continuous-wave laser beam was analyzed by means of high-speed imaging. The formation of compression shocks was observed within the flow of the evaporated material, which is an indication of flow speeds well above the local speed of sound. The flow speed of the hot ablation products can be estimated by analyzing the position of these compression shocks. We investigated the temporal evolution of the flow speed during the drilling process and the influence of the average laser power on the flow speed. The flow speed increases with increasing average laser powers. The moment of drilling through the material changes the conditions for the drilling process and was confirmed to influence the flow speed of the ablated material. Compression shocks can also be observed during laser cutting of CFRP with a moving laser beam.

Hydrocode and Molecular Dynamics modelling of uniaxial shock wave experiments on Silicon

NASA Astrophysics Data System (ADS)

Stubley, Paul; McGonegle, David; Patel, Shamim; Suggit, Matthew; Wark, Justin; Higginbotham, Andrew; Comley, Andrew; Foster, John; Rothman, Steve; Eggert, Jon; Kalantar, Dan; Smith, Ray

2015-06-01

Recent experiments have provided further evidence that the response of silicon to shock compression has anomalous properties, not described by the usual two-wave elastic-plastic response. A recent experimental campaign on the Orion laser in particular has indicated a complex multi-wave response. While Molecular Dynamics (MD) simulations can offer a detailed insight into the response of crystals to uniaxial compression, they are extremely computationally expensive. For this reason, we are adapting a simple quasi-2D hydrodynamics code to capture phase change under uniaxial compression, and the intervening mixed phase region, keeping track of the stresses and strains in each of the phases. This strain information is of such importance because a large number of shock experiments use diffraction as a key diagnostic, and these diffraction patterns depend solely on the elastic strains in the sample. We present here a comparison of the new hydrodynamics code with MD simulations, and show that the simulated diffraction taken from the code agrees qualitatively with measured diffraction from our recent Orion campaign.

Compressible Flow in Front of an Axisymmetric Blunt Object: Analytic Approximation and Astrophysical Implications

NASA Astrophysics Data System (ADS)

Keshet, Uri; Naor, Yossi

2016-10-01

Compressible flows around blunt objects have diverse applications, but current analytic treatments are inaccurate and limited to narrow parameter regimes. We show that the gas-dynamic flow in front of an axisymmetric blunt body is accurately derived analytically using a low order expansion of the perpendicular gradients in terms of the parallel velocity. This reproduces both subsonic and supersonic flows measured and simulated for a sphere, including the transonic regime and the bow shock properties. Some astrophysical implications are outlined, in particular for planets in the solar wind and for clumps and bubbles in the intergalactic medium. The bow shock standoff distance normalized by the obstacle curvature is ∼ 2/(3g) in the strong shock limit, where g is the compression ratio. For a subsonic Mach number M approaching unity, the thickness δ of an initially weak, draped magnetic layer is a few times larger than in the incompressible limit, with amplification ∼ (1+1.3{M}2.6)/(3δ ).

The density compression ratio of shock fronts associated with coronal mass ejections

NASA Astrophysics Data System (ADS)

Kwon, Ryun-Young; Vourlidas, Angelos

2018-02-01

We present a new method to extract the three-dimensional electron density profile and density compression ratio of shock fronts associated with coronal mass ejections (CMEs) observed in white light coronagraph images. We demonstrate the method with two examples of fast halo CMEs (˜2000 km s-1) observed on 2011 March 7 and 2014 February 25. Our method uses the ellipsoid model to derive the three-dimensional geometry and kinematics of the fronts. The density profiles of the sheaths are modeled with double-Gaussian functions with four free parameters, and the electrons are distributed within thin shells behind the front. The modeled densities are integrated along the lines of sight to be compared with the observed brightness in COR2-A, and a χ2 approach is used to obtain the optimal parameters for the Gaussian profiles. The upstream densities are obtained from both the inversion of the brightness in a pre-event image and an empirical model. Then the density ratio and Alfvénic Mach number are derived. We find that the density compression peaks around the CME nose, and decreases at larger position angles. The behavior is consistent with a driven shock at the nose and a freely propagating shock wave at the CME flanks. Interestingly, we find that the supercritical region extends over a large area of the shock and lasts longer (several tens of minutes) than past reports. It follows that CME shocks are capable of accelerating energetic particles in the corona over extended spatial and temporal scales and are likely responsible for the wide longitudinal distribution of these particles in the inner heliosphere. Our results also demonstrate the power of multi-viewpoint coronagraphic observations and forward modeling in remotely deriving key shock properties in an otherwise inaccessible regime.

Computational and Experimental Analysis of Mach 5 Air Flow over a Cylinder with a Nanosecond Pulse Discharge

DTIC Science & Technology

2012-01-01

wind tunnel t = 4:1 s after a discharge event. The compression wave pushes the bow - shock outward, as seen in the red region. Consistent with the two... wind tunnel , which was able to computationally replicate the bow - shock structure seen in the schlieren photography, predict the width of the tunnel’s...from the pulse source. As the shock wave travels upstream, it interacts with the standing bow - shock and momentarily increases the bow - shock

Investigation of shock waves in the relativistic Riemann problem: A comparison of viscous fluid dynamics to kinetic theory

NASA Astrophysics Data System (ADS)

Bouras, I.; Molnár, E.; Niemi, H.; Xu, Z.; El, A.; Fochler, O.; Greiner, C.; Rischke, D. H.

2010-08-01

We solve the relativistic Riemann problem in viscous matter using the relativistic Boltzmann equation and the relativistic causal dissipative fluid-dynamical approach of Israel and Stewart. Comparisons between these two approaches clarify and point out the regime of validity of second-order fluid dynamics in relativistic shock phenomena. The transition from ideal to viscous shocks is demonstrated by varying the shear viscosity to entropy density ratio η/s. We also find that a good agreement between these two approaches requires a Knudsen number Kn<1/2.

Investigation of shock waves in the relativistic Riemann problem: A comparison of viscous fluid dynamics to kinetic theory

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

Bouras, I.; El, A.; Fochler, O.

2010-08-15

We solve the relativistic Riemann problem in viscous matter using the relativistic Boltzmann equation and the relativistic causal dissipative fluid-dynamical approach of Israel and Stewart. Comparisons between these two approaches clarify and point out the regime of validity of second-order fluid dynamics in relativistic shock phenomena. The transition from ideal to viscous shocks is demonstrated by varying the shear viscosity to entropy density ratio {eta}/s. We also find that a good agreement between these two approaches requires a Knudsen number Kn<1/2.

Equation of state of molten fayalite (Fe2SiO4)

NASA Astrophysics Data System (ADS)

Waller, C.; Liu, Q.; Agee, C. B.; Asimow, P. D.; Lange, R. A.

2010-12-01

We have conducted new equation of state measurements on liquid fayalite (Fe2SiO4) in a collaborative, multi-technique study. Using a shared bulk starting material, we have measured the liquid density, the bulk modulus (K), and its pressure derivative (K’) from 1 atm to 163 GPa using 1-atm double-bob Archimedean and ultrasonic, sink/float, and shock wave techniques to form a coherent, internally consistent equation of state. Previous shock studies of liquid fayalite were conducted up to pressures of 40 GPa1; we extended this data set with two additional pre-heated, molten (1573 K) fayalite shock compression experiments at 121 and 163 GPa. Linear fitting of this data in shock velocity (US)-particle velocity (up) space defines a Hugoniot with an unconstrained zero-pressure intercept that crosses within error at the bulk sound speed (Co) determined by ultrasonic techniques. Fixing the intercept at this ultrasonic value reduces the error on the linear fit and yields the relation: US =1.65(0.02)up+ 2.4377(0.006) km/s. This relationship indicates that the behavior of the liquid is relaxed during shock compression and demonstrates consistency across experimental methods. Likewise, results from new static compression sink/float experiments conducted in piston-cylinder and multi-anvil devices are in agreement with shock wave and ultrasonic data, consistent with an isothermal K=19.4 and K’=5.57 at 1500°C. In solid materials, the Grüneisen parameter (γ) generally decreases upon compression. However, preliminary calculations for γ of this liquid using additional initially solid shock data from Chen et al.(2002) indicate that γ increases upon compression. Using the functional form γ = γo(ρo/ρ)q at a density of 7.65 Mg/m3 yields a q value of -1.77 (γo = 0.41 is known from low-pressure data), which is similar to the reported q values of forsterite2, enstatite3, and anorthite-diopside liquids4. This result shows that iron-bearing mafic to ultramafic silicate liquids follow the same general behavior as iron-free liquids such that -2.0 ≤ q ≤ -1.5 for the compression range 1 ≥ ρo/ρ ≥ 0.50. We will be performing an additional shock wave experiment on initially solid (300 K) fayalite to confirm this result. We will be continuing collaborative equation of state measurements on additional iron-bearing silicate liquids, working to further clarify the properties of melts and their importance to understanding the dynamics of the early magma ocean and of melt migration within the mantle. In particular, understanding the properties of iron-rich silicates and their melts will constrain hypotheses of melting and of iron enrichment for explaining the occurrence and characteristics of ultra-low velocity zones near the CMB.

Liberal Versus Restrictive Intravenous Fluid Therapy for Early Septic Shock: Rationale for a Randomized Trial.

PubMed

Self, Wesley H; Semler, Matthew W; Bellomo, Rinaldo; Brown, Samuel M; deBoisblanc, Bennett P; Exline, Matthew C; Ginde, Adit A; Grissom, Colin K; Janz, David R; Jones, Alan E; Liu, Kathleen D; Macdonald, Stephen P J; Miller, Chadwick D; Park, Pauline K; Reineck, Lora A; Rice, Todd W; Steingrub, Jay S; Talmor, Daniel; Yealy, Donald M; Douglas, Ivor S; Shapiro, Nathan I

2018-05-09

Prompt intravenous fluid therapy is a fundamental treatment for patients with septic shock. However, the optimal approach for administering intravenous fluid in septic shock resuscitation is unknown. Two competing strategies are emerging: a liberal fluids approach, consisting of a larger volume of initial fluid (50 to 75 mL/kg [4 to 6 L in an 80-kg adult] during the first 6 hours) and later use of vasopressors, versus a restrictive fluids approach, consisting of a smaller volume of initial fluid (≤30 mL/kg [≤2 to 3 L]), with earlier reliance on vasopressor infusions to maintain blood pressure and perfusion. Early fluid therapy may enhance or maintain tissue perfusion by increasing venous return and cardiac output. However, fluid administration may also have deleterious effects by causing edema within vital organs, leading to organ dysfunction and impairment of oxygen delivery. Conversely, a restrictive fluids approach primarily relies on vasopressors to reverse hypotension and maintain perfusion while limiting the administration of fluid. Both strategies have some evidence to support their use but lack robust data to confirm the benefit of one strategy over the other, creating clinical and scientific equipoise. As part of the National Heart, Lung, and Blood Institute Prevention and Early Treatment of Acute Lung Injury Network, we designed a randomized clinical trial to compare the liberal and restrictive fluids strategies, the Crystalloid Liberal or Vasopressor Early Resuscitation in Sepsis trial. The purpose of this article is to review the current literature on approaches to early fluid resuscitation in adults with septic shock and outline the rationale for the upcoming trial. Copyright © 2018 American College of Emergency Physicians. Published by Elsevier Inc. All rights reserved.

A computer program for the calculation of the flow field including boundary layer effects for mixed-compression inlets at angle of attack

NASA Technical Reports Server (NTRS)

Vadyak, J.; Hoffman, J. D.

1982-01-01

A computer program was developed which is capable of calculating the flow field in the supersonic portion of a mixed compression aircraft inlet operating at angle of attack. The supersonic core flow is computed using a second-order three dimensional method-of-characteristics algorithm. The bow shock and the internal shock train are treated discretely using a three dimensional shock fitting procedure. The boundary layer flows are computed using a second-order implicit finite difference method. The shock wave-boundary layer interaction is computed using an integral formulation. The general structure of the computer program is discussed, and a brief description of each subroutine is given. All program input parameters are defined, and a brief discussion on interpretation of the output is provided. A number of sample cases, complete with data listings, are provided.

Effect of Shock Precompression on the Critical Diameter of Liquid Explosives

NASA Astrophysics Data System (ADS)

Petel, Oren E.; Higgins, Andrew J.; Yoshinaka, Akio C.; Zhang, Fan

2006-07-01

The critical diameter of both ambient and shock-precompressed liquid nitromethane confined in PVC tubing are measured experimentally. The experiment was conducted for both amine sensitized and neat NM. In the precompression experiments, the explosive is compressed by a strong shock wave generated by a donor explosive and reflected from a high impedance anvil prior to being detonated by a secondary event. The pressures reached in the test sections prior to detonation propagation was approximately 7 and 8 GPa for amine sensitized and neat NM respectively. The results demonstrated a 30% - 65% decrease in the critical diameter for the shock-compressed explosives. This critical diameter decrease is observed despite a significant decrease in the predicted Von Neumann temperature of the detonation in the precompressed explosive. The results are discussed in the context of theoretical predictions based on thermal ignition theory and previous critical diameter measurements.

Kinetic Alfvén waves and particle response associated with a shock-induced, global ULF perturbation of the terrestrial magnetosphere

DOE PAGES

Malaspina, David M.; Claudepierre, Seth G.; Takahashi, Kazue; ...

2015-11-14

On 2 October 2013, the arrival of an interplanetary shock compressed the Earth's magnetosphere and triggered a global ULF (ultra low frequency) oscillation. Furthermore, the Van Allen Probe B spacecraft observed this large-amplitude ULF wave in situ with both magnetic and electric field data. Broadband waves up to approximately 100 Hz were observed in conjunction with, and modulated by, this ULF wave. Detailed analysis of fields and particle data reveals that these broadband waves are Doppler-shifted kinetic Alfvén waves. This event then suggests that magnetospheric compression by interplanetary shocks can induce abrupt generation of kinetic Alfvén waves over large portionsmore » of the inner magnetosphere, potentially driving previously unconsidered wave-particle interactions throughout the inner magnetosphere during the initial response of the magnetosphere to shock impacts.« less

Self-charging metering and dispensing device for fluids

NASA Technical Reports Server (NTRS)

Hooper, S. L.; Setzer, D. (Inventor)

1984-01-01

A self-metering and dispensing device for fluids obtained from a pressurized fluid supply is discussed. Tubing and valving means permit the introduction of fluid into and discharge from a closed cylindrical reservoir. The reservoir contains a slideably disposed piston co-acting with a coil compression spring, with piston travel determining the amount of fluid in the reservoir. Once the determined amount of fluid is introduced into the reservoir, the fluid is discharged by the force of the coil compression spring acting upon the piston.

Shock-activated reaction synthesis and high pressure response of titanium-based ternary carbide and nitride ceramics

NASA Astrophysics Data System (ADS)

Jordan, Jennifer Lynn

The objectives of this study were to (a) investigate the effect of shock activation of precursor powders for solid-state reaction synthesis of Ti-based ternary ceramics and (b) to determine the high pressure phase stability and Hugoniot properties of Ti3SiC2. Dynamically densified compacts of Ti, SiC, and graphite precursor powders and Ti and AlN precursor powders were used to study the shock-activated formation of Ti 3SiC2 and Ti2AlN ternary compounds, respectively, which are considered to be novel ceramics having high stiffness but low hardness. Gas gun and explosive loading techniques were used to obtain a range of loading conditions resulting in densification and activation. Measurements of fraction reacted as a function of time and temperature and activation energies obtained from DTA experiments were used to determine the degree of activation caused by shock compression and its subsequent effect on the reaction mechanisms and kinetics. In both systems, shock activation led to an accelerated rate of reaction at temperatures less than 1600°C and, above that temperature, it promoted the formation of almost 100% of the ternary compound. A kinetics-based mathematical model based on mass and thermal transport was developed to predict the effect of shock activation and reaction synthesis conditions that ensure formation of the ternary compounds. Model predictions revealed a transition temperature above which the reaction is taken over by the "run-away" combustion-type mode. The high pressure phase stability of pre-alloyed Ti 3SiC2 compound was investigated by performing Hugoniot shock and particle velocity measurements using the facilities at the National Institute for Materials Science (Tsukuba, Japan). Experiments performed at pressures of 95--120 GPa showed that the compressibility of Ti3SiC 2 at these pressures deviates from the previously reported compressibility of the material under static high pressure loading. The deviation in compressibility behavior is indicative of the transformation of the Ti3 SiC2 ceramic to a high pressure, high density phase.

Uncertainty Assessments of 2D and Axisymmetric Hypersonic Shock Wave - Turbulent Boundary Layer Interaction Simulations at Compression Corners

NASA Technical Reports Server (NTRS)

Gnoffo, Peter A.; Berry, Scott A.; VanNorman, John W.

2011-01-01

This paper is one of a series of five papers in a special session organized by the NASA Fundamental Aeronautics Program that addresses uncertainty assessments for CFD simulations in hypersonic flow. Simulations of a shock emanating from a compression corner and interacting with a fully developed turbulent boundary layer are evaluated herein. Mission relevant conditions at Mach 7 and Mach 14 are defined for a pre-compression ramp of a scramjet powered vehicle. Three compression angles are defined, the smallest to avoid separation losses and the largest to force a separated flow engaging more complicated flow physics. The Baldwin-Lomax and the Cebeci-Smith algebraic models, the one-equation Spalart-Allmaras model with the Catrix-Aupoix compressibility modification and two-equation models including Menter SST, Wilcox k-omega 98, and Wilcox k-omega 06 turbulence models are evaluated. Each model is fully defined herein to preclude any ambiguity regarding model implementation. Comparisons are made to existing experimental data and Van Driest theory to provide preliminary assessment of model form uncertainty. A set of coarse grained uncertainty metrics are defined to capture essential differences among turbulence models. Except for the inability of algebraic models to converge for some separated flows there is no clearly superior model as judged by these metrics. A preliminary metric for the numerical component of uncertainty in shock-turbulent-boundary-layer interactions at compression corners sufficiently steep to cause separation is defined as 55%. This value is a median of differences with experimental data averaged for peak pressure and heating and for extent of separation captured in new, grid-converged solutions presented here. This value is consistent with existing results in a literature review of hypersonic shock-turbulent-boundary-layer interactions by Roy and Blottner and with more recent computations of MacLean.

Practicality of magnetic compression for plasma density control

DOE PAGES

Gueroult, Renaud; Fisch, Nathaniel J.

2016-03-16

Here, plasma densification through magnetic compression has been suggested for time-resolved control of the wave properties in plasma-based accelerators [P. F. Schmit and N. J. Fisch, Phys. Rev. Lett. 109, 255003 (2012)]. Using particle in cell simulations with real mass ratio, the practicality of large magnetic compression on timescales shorter than the ion gyro-period is investigated. For compression times shorter than the transit time of a compressional Alfven wave across the plasma slab, results show the formation of two counter-propagating shock waves, leading to a highly non-uniform plasma density profile. Furthermore, the plasma slab displays large hydromagnetic like oscillations aftermore » the driving field has reached steady state. Peak compression is obtained when the two shocks collide in the mid-plane. At this instant, very large plasma heating is observed, and the plasmaβ is estimated to be about 1. Although these results point out a densification mechanism quite different and more complex than initially envisioned, these features still might be advantageous in particle accelerators.« less

LES of Temporally Evolving Mixing Layers by an Eighth-Order Filter Scheme

NASA Technical Reports Server (NTRS)

Hadjadj, A; Yee, H. C.; Sjogreen, B.

2011-01-01

An eighth-order filter method for a wide range of compressible flow speeds (H.C. Yee and B. Sjogreen, Proceedings of ICOSAHOM09, June 22-26, 2009, Trondheim, Norway) are employed for large eddy simulations (LES) of temporally evolving mixing layers (TML) for different convective Mach numbers (Mc) and Reynolds numbers. The high order filter method is designed for accurate and efficient simulations of shock-free compressible turbulence, turbulence with shocklets and turbulence with strong shocks with minimum tuning of scheme parameters. The value of Mc considered is for the TML range from the quasi-incompressible regime to the highly compressible supersonic regime. The three main characteristics of compressible TML (the self similarity property, compressibility effects and the presence of large-scale structure with shocklets for high Mc) are considered for the LES study. The LES results using the same scheme parameters for all studied cases agree well with experimental results of Barone et al. (2006), and published direct numerical simulations (DNS) work of Rogers & Moser (1994) and Pantano & Sarkar (2002).

Compressible Heating in the Condense Phase due to Pore Collapse in HMX

NASA Astrophysics Data System (ADS)

Zhang, Ju; Jackson, Thomas

Axisymmetric pore collapse in HMX is studied numerically by solving multi-phase reactive Euler equations. The generation of hot spots in the condense phase due to compressible heating is examined. The motivation is to improve the understanding of the role of embedded cavities in the initiation of reaction in explosives, and to investigate the effect of hot spots in the condense phase due to compressible heating alone, complementing previous study on hot spots due to the reaction in the gas phase and at the interface. It is found that the shock-cavity interaction results in pressures and thus temperatures that are substantially higher than the post-shock values in the condense phase. However, these hot spots in the condense phase due to compressible heating alone do not seem to be sufficiently hot to lead to ignition at shock pressures of 1-3 GPa. Thus, compressible heating in the condense phase may be excluded as a mechanism for initiation of explosives. It should be pointed out that the ignition threshold for the temperature, the so-called ``switch-on'' temperature, of hot spots depend on chemistry kinetics parameters. Switch-on temperature is lower for faster reaction rate. The current chemistry kinetics parameters are based on previous experimental work. This work was supported in part by the Defense Threat Reduction Agency and by the U.S. Department of Energy.

Verification assessment of piston boundary conditions for Lagrangian simulation of compressible flow similarity solutions

DOE PAGES

Ramsey, Scott D.; Ivancic, Philip R.; Lilieholm, Jennifer F.

2015-12-10

This work is concerned with the use of similarity solutions of the compressible flow equations as benchmarks or verification test problems for finite-volume compressible flow simulation software. In practice, this effort can be complicated by the infinite spatial/temporal extent of many candidate solutions or “test problems.” Methods can be devised with the intention of ameliorating this inconsistency with the finite nature of computational simulation; the exact strategy will depend on the code and problem archetypes under investigation. For example, self-similar shock wave propagation can be represented in Lagrangian compressible flow simulations as rigid boundary-driven flow, even if no such “piston”more » is present in the counterpart mathematical similarity solution. The purpose of this work is to investigate in detail the methodology of representing self-similar shock wave propagation as a piston-driven flow in the context of various test problems featuring simple closed-form solutions of infinite spatial/temporal extent. The closed-form solutions allow for the derivation of similarly closed-form piston boundary conditions (BCs) for use in Lagrangian compressible flow solvers. Finally, the consequences of utilizing these BCs (as opposed to directly initializing the self-similar solution in a computational spatial grid) are investigated in terms of common code verification analysis metrics (e.g., shock strength/position errors and global convergence rates).« less

Verification assessment of piston boundary conditions for Lagrangian simulation of compressible flow similarity solutions

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

Ramsey, Scott D.; Ivancic, Philip R.; Lilieholm, Jennifer F.

This work is concerned with the use of similarity solutions of the compressible flow equations as benchmarks or verification test problems for finite-volume compressible flow simulation software. In practice, this effort can be complicated by the infinite spatial/temporal extent of many candidate solutions or “test problems.” Methods can be devised with the intention of ameliorating this inconsistency with the finite nature of computational simulation; the exact strategy will depend on the code and problem archetypes under investigation. For example, self-similar shock wave propagation can be represented in Lagrangian compressible flow simulations as rigid boundary-driven flow, even if no such “piston”more » is present in the counterpart mathematical similarity solution. The purpose of this work is to investigate in detail the methodology of representing self-similar shock wave propagation as a piston-driven flow in the context of various test problems featuring simple closed-form solutions of infinite spatial/temporal extent. The closed-form solutions allow for the derivation of similarly closed-form piston boundary conditions (BCs) for use in Lagrangian compressible flow solvers. Finally, the consequences of utilizing these BCs (as opposed to directly initializing the self-similar solution in a computational spatial grid) are investigated in terms of common code verification analysis metrics (e.g., shock strength/position errors and global convergence rates).« less

Principles of fluid management and stewardship in septic shock: it is time to consider the four D's and the four phases of fluid therapy.

PubMed

Malbrain, Manu L N G; Van Regenmortel, Niels; Saugel, Bernd; De Tavernier, Brecht; Van Gaal, Pieter-Jan; Joannes-Boyau, Olivier; Teboul, Jean-Louis; Rice, Todd W; Mythen, Monty; Monnet, Xavier

2018-05-22

In patients with septic shock, the administration of fluids during initial hemodynamic resuscitation remains a major therapeutic challenge. We are faced with many open questions regarding the type, dose and timing of intravenous fluid administration. There are only four major indications for intravenous fluid administration: aside from resuscitation, intravenous fluids have many other uses including maintenance and replacement of total body water and electrolytes, as carriers for medications and for parenteral nutrition. In this paradigm-shifting review, we discuss different fluid management strategies including early adequate goal-directed fluid management, late conservative fluid management and late goal-directed fluid removal. In addition, we expand on the concept of the "four D's" of fluid therapy, namely drug, dosing, duration and de-escalation. During the treatment of patients with septic shock, four phases of fluid therapy should be considered in order to provide answers to four basic questions. These four phases are the resuscitation phase, the optimization phase, the stabilization phase and the evacuation phase. The four questions are "When to start intravenous fluids?", "When to stop intravenous fluids?", "When to start de-resuscitation or active fluid removal?" and finally "When to stop de-resuscitation?" In analogy to the way we handle antibiotics in critically ill patients, it is time for fluid stewardship.

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.