Impact Of Shock Wave Research Articles

Shock wave impact simulation of a vehicle occupant using fluid/structure/dynamics interactions

Ground vehicles subjected to blast can result in vehicle movements and occupant injuries. The engineering mechanisms involved in such blasts include fluid dynamics, solid dynamics, and multi-body dynamics. This paper describes a parallel computer simulation methodology that can be applied to couple the structural deformation prediction of a ground vehicle system and the associated occupant kinematics during a blast event. Generic box and dummy models were used in the demonstration of this newly-developed methodology. The generic system structure consists of an outer cube representing a vehicle armor structure, and a dummy representing a crew member in a ground vehicle. Simulation results for different cases include free air blast wave propagation, blast on a metal plate and over a hemispherical dome, and blast wave interaction with a vehicle and its occupant inside.

Behavior of Metallic Foam under Shock Wave Loading

In this manuscript, the behavior of metallic foam under impact loading and shock wave propagation has been observed. The goal of this research was to investigate the material and structural properties of submerged open-cell aluminum foam under impact loading conditions with particular interest in shock wave propagation and its effects on cellular material deformation. For this purpose experimental tests and dynamic computational simulations of aluminum foam specimens inside a water tank subjected to explosive charge have been performed. Comparison of the results shows a good correlation between the experimental and simulation results.

Surface nanostructure of a directionally solidified Ni-based superalloy DZ4 induced by high intensity pulsed ion beam irradiation

A high intensity pulsed ion beam (HIPIB) was used to irradiate directionally solidified nickel-based superalloy DZ4 with the following parameters: ion content consisting of Cn+ (30at.%) and H+(70at.%), an accelerating voltage of 250kV, a pulse duration of 70ns, a beam current density of 100A/cm2, irradiation times of 15. As revealed by SEM and TEM, the thermal effect was confined in a ∼1.3μm thick surface zone, in which rapid melting and cooling occurred. A two-phase nanostructured layer of ∼10nm thick was formed on the outmost surface. The component phases are the γ phase and the carbide with a particle size of ∼5–10nm. The presence of dense dislocation networks was observed in depth in the substrate metal, for instance ∼20μm away from the sample surface, which is caused by shock wave impact.

Influence Analysis of Roadway Friction on Shock Wave Attenuation

Friction is the extremely important factor when considering the interaction between the shock wave and the tunnel wall. But so far, the impact of wall friction on the shock wave is mainly measured by experimental methods. This paper mainly discusses the effect of wall friction on the shock wave attenuation, without considering roughness, roughness elements, the viscosity of air, and the complex relationship between them; the numerical simulation calculation model is established with DYNA calculation software; the influence law of friction coefficient on tunnel shock wave propagation and attenuation is given based on friction coefficient between air medium and tunnel wall, so as to provide guidance to mining, reduce the impact of tunnel explosion shock wave on personnel and equipment and provide a design basis for shaft safety works.

Numerical simulation of interaction of deformable gas-permeable packets of grids with shock waves

A mathematical model that describes a one-dimensional approximation of interrelated processes of unsteady deformation of plane, cylindrical, and spherical packets of metallic woven grids and wave processes in the gas contained in pores is presented. Nonlinear equations of dynamics of two interpenetrating continua are solved numerically with the use of a modified Godunov scheme. Solutions of problems of the shock wave impact on plane and cylindrical packets of grids are obtained. Numerical results are found to agree with available experimental data. The character of explosive waves passing through a cylindrical packet of grids is studied.

Experimental Study of the Impact of a Strong Underwater Shock Wave on a Concrete Dam

To study the effect of a strong underwater shock wave on a concrete dam, in this research the hammers impact were applied to simulate the underwater shock in a model test. The model scale was 200 according to the gravity-elasticity similitude law. Five acceleration sensors were imbedded along the downstream surface of the dam. The maximum input pressure was evaluated based on the recorded accelerations. The explosive charge and the distance between the explosion center and the dam were determined corresponding to the maximum impact pressure. After the hammers impacted, the upstream face of the dam was fractured and downstream was scabbed; some cracks extended from the upstream face to the downstream face; the head of dam was projected; and the dam appeared entirely displacement. Although the damage similarity of the model and prototype is not verified, this method may be used to verify the quality of a protection project and offered evidence to define a protection project.

Impact of shock wave on a body moving at Supersonic speed

Abstract: Determining how much force will an aircraft or any forward moving body have to face when it travels at a velocity of more than the velocity of sound. The core of this research is to find out how much pressure air can exert after the formation of the shock wave, subsequently calculating force.

OS1-1-2 超音波作用下での脂質膜構造変化 : 分子動力学シミュレーション(OS1 マルチスケ-ル現象のシミュレーション技術(1))

Combined use of ultrasound and micro- or nano-sized bubbles can deliver macro molecules into biological cells. Here, we introduce molecular dynamics studies that we have conducted for past years to understand the molecular mechanisms about the molecular delivery into the cells. In the studies, we have used the lipid bilayer structure model, the common structure of all biological cell membranes, with unsteady and nonequilibrium molecular dynamics simulation techniques. The studies have revealed the structural changes of the bilayer and the water penetration to the bilayer induced by the impact of shockwave on the bilayer, and the formation of pore structure penetrating the bilayer after the loading of water molecules into the bilayer. Moreover, we present resent results about responses of the intact or pore-containing bilayers to stretch.

Poration of Lipid Bilayers by Shock-Induced Nanobubble Collapse

Sonoporation is a promising noninvasive drug- and gene-delivery approach, in which cavitation bubbles generated by ultrasound are used to enhance the cell membrane permeability. We have performed multimillion-atom molecular dynamics (MD) simulations to study the impact of shock waves on nanobubbles in the vicinity of a dipalmitoylphosphatidylcholine (DPPC) bilayer. The MD simulations reveal that the nanojet impact generates shear flow of water on bilayer leaflets and pressure gradients across them, which transiently enhance the bilayer permeability by creating nanopores and water molecules translocation across the bilayer. Effects of nanobubble size and temperature on the porosity of lipid bilayers will be discussed.Fig.: Nanojet (blue, green and red are velocity streamlines) impact deforming the lipid membrane (yellow). The nanopore created in the membrane (blue) is shown in the bottom inset. The top inset shows the time evolution of lateral flow on the lipid membrane surface.View Large Image | View Hi-Res Image | Download PowerPoint Slide

The counter-jet formation in an air bubble induced by the impact of shock waves

The interaction of an air bubble (isolated in water or attached to a boundary) with shock waves induced by electric sparks is investigated by high-speed photography. The interaction is closely related to the counter-jet induced by the impact of shock waves. The formation of a counter-jet in an air bubble is related to the liquid jet formed in the same air bubble, but the mechanism is different with that of the counter-jet formation in a collapsing cavitation bubble. The formation of a counter-jet in an air bubble is related to discharge energy, air bubble size and radius of shock wave. With a given energy of the spark discharge, the formation of a counter-jet in an air bubble is related to δ/ ɛ (the ratio of the dimensionless bubble-bubble distance to the dimensionless air bubble radius). The counter-jet will only be produced when δ/ ɛ is in the range of 1.2–2.2. The counter-jet in an air bubble is of an important nuclei-generating mechanism.

Three dimensional shock wave/boundary layer interactions

An investigation into a three-dimensional, curved shock wave interacting with a three-dimensional, curved boundary layer on a slender body is presented. Three different nose profiles mounted on a cylindrical body were tested in a supersonic wind tunnel and numerically simulated by solving the Navier–Stokes equations. The conical and hemispherical nose profiles tested were found to generate shock waves of sufficient strength to separate the boundary layer on the cylinder, while the shock wave generated by the ogival profile did not separate the boundary layer. For the separated flow, separation was found to occur predominantly on the windward side of the cylinder with the lee-side remaining shielded from the direct impact of the incident shock wave. A thickening of the boundary layer on the lee-side of all the profiles was observed, and in the conical and hemispherical cases this leads to the re-formation of the incident shock wave some distance away from the surface of the cylinder. A complex reflection pattern off the shock wave/boundary layer interaction (SWBLI) was also identified for the separated flow cases. For comparative purposes, an inviscid simulation was performed using the hemispherical profile. Significant differences between the viscous and inviscid results were noted including the absence of a boundary layer leading to a simplified shock wave reflection pattern forming. The behaviour of the incident shock wave on the lee-side of the cylinder was also affected with the shock wave amalgamating on the surface of the cylinder instead of away from the surface as per the viscous case. Test data from the wind tunnel identified two separation lines present on the cylindrical surface of the hemispherical SWBLI generator. The pair of lines were not explicitly evident in the original CFD simulations run, but were later identified in a high-resolution simulation.

The comeback of shock waves in inertial fusion energy

AbstractThe shock waves in laser plasma interaction have played an important role in the study of inertial fusion energy (IFE) since the 1970's and perhaps earlier. The interaction of laser, or any other high power beam, induced shock waves with matter was one of the foundations of the target design in IFE. Even the importance of shock wave collision was studied and its importance forgotten. In due course, the shock waves were taken as granted and became “second fiddle” in IFE scenario. The analysis of the shock wave in the context of IFE is revived in this paper. At the forefront of the past decade the concept of fast ignition was introduced. The different ideas of fast ignition are summarized with special emphasis on shock wave fast ignition. The ignition is achieved by launching a shock wave during the final stages of the implosion. In this paper, a possible instability in the propagation of the igniting shock wave is analyzed. The idea of combining the fast ignition fusion with an impact shock wave is suggested and analyzed. This is achieved by launching a shock wave by an accelerated foil during the final stage of the implosion in order to ignite the compressed fuel. In this scheme, like other fast ignition schemes, a significant reduction of the driver energy in comparison with standard IFE scenarios is required for the same high gain fusion.

Thomas J. Ahrens (1936–2010)

Thomas J. Ahrens, a leader in the study of high‐pressure shock wave and planetary impact phenomena, died at his home in Pasadena, Calif., on 24 November 2010 at the age of 74. He was the California Institute of Technology's Fletcher Jones Professor of Geophysics, emeritus since 2005 but professionally active to the end. He had been president of AGU's Tectonophysics section, editor of Journal of Geophysical Research, founding member of both the Mineral and Rock Physics and Study of the Earth's Deep Interior focus groups, and editor—more like key driving force—for AGU's Handbook of Physical Constants. Tom was a pioneer in experimental and numerical studies of the effects of projectiles hitting a target at velocities exceeding the speed of sound (hypervelocity impact), arguably the most important geophysical process in the formation, growth, and, in many cases, surface evolution of planets. As a professor at Caltech, he established the foremost university laboratory for shock wave experiments, where students and research associates from around the world pursued basic research in geophysics, planetary science, and other disciplines. Previously, high‐pressure shock experiments were conducted primarily in national laboratories, where they were initially associated with the development of nuclear weapons.

ANALYSIS OF THREAT TO CREW POSED BY EXPLOSION OF CHARGE PLACED UNDER WHEELED ARMOURED VEHICLE

Provision of proper protection against landmines is a major aim of modern military vehicle designs. The point of developing the methods and means of countermine protection is to identify the shock wave impact on a vehicle construction and its crew. Information on overload coming from landmine explosions on a person are strictly confidential or not detailed enough. The basis to obtain them is to carry out experimental and numerical tests. This article presents basic issues and threats to crews as a result of landmine, IED or EFP explosions carried out by terrorists. The literature published has helped the authors to identify the main parts of body prone to the impulse load of a shock wave explosion on a wheeled military vehicle. The methodology and sample results of experimental tests identifying the shock wave load on a vehicle and its crew in a characteristic anthropometrics points of body are presented as well. Injury criteria and crew threat levels resulting from explosive load under a vehicle and its close area are outlined. The aim of such a complex analysis of shock wave load over wheeled military vehicles and their crews is the development of modern and effective protection devices.

Shock-wave induced damage in lipid bilayers: a dissipative particle dynamics simulation study

The effects of shock-wave impact on the damage of lipid bilayer membranes are investigated with dissipative particle simulations at constant energy (DPDE). A coarse-grained model for the phospholipid bilayer in aqueous environment is employed, which models single lipids as short chains consisting of a hydrophilic head and two hydrophobic tail beads. Water is modeled by mapping four H2O molecules to one water bead. Using the DPDE method enables us to faithfully simulate the non-equilibrium shock-wave process with a coarse-grained model as the correct heat capacity can be recovered. At equilibrium, we obtain self-stabilizing bilayer structures that exhibit bending stiffness and compression modulus comparable to experimental measurements under physiological conditions. We study in detail the damage behavior of the coarse-grained lipid bilayer upon high-speed shock-wave impact as a function of shock impact velocity and bilayer stability. A single damage parameter based on an orientation dependent correlation function is introduced. We observe that mechanical bilayer stability has only small influence on the resulting damage after shock-wave impact, and inertial effects play almost no role. At shock-front velocities below ≲ 3000 ms−1, we observe reversible damage, whereas for speeds ≳ 3900 ms−1 no such recovery, or self-repair of the bilayer, could be observed.

Experimental investigation of door dynamic opening caused by impinging shock wave

To prevent damage caused by accidental overpressure inside a closed duct (e.g. jet engine) safety valves are introduced. The present study experimentally investigates the dynamic opening of such valves by employing a door at the end of a shock tube driven section. The door is hung on an axis and is free to rotate, thereby opening the tube. The evolved flow and wave pattern due to a collision of an incident shock wave with the door, causing the door opening, is studied by employing a high speed schlieren system and recording pressures at different places inside the tube as well as on the rotating door. Analyzing this data sheds light on the air flow evolution and the behavior of the opening door. In the present work, emphasis is given to understanding the complex, unsteady flow developed behind the transmitted shock wave as it diffracts over the opening door. It is shown that both the door inertia and the shock wave strength influence the opening dynamic evolution, but not in the proportions that might be expected.

A Computational Study of the External Shock-Wave Impact on the Combustion Regime

A problem concerning shock-flame interaction within a semiopened channel filled with premixed hydrogen-oxygen or hydrogen-air gas mixtures is solved numerically. Such an interaction induces combustion regime changing. A classification of probable new regimes is obtained by the example of two mixtures. The basic scenario of regime changing is local energy release intensification. Maximum pressures generated while slow combustion transits to a faster energy release regime and then to overdriven detonation depend on the transient process generation conditions. The generated pressures considerably exceed the pressures in the initial incident shock. The case of transition to overdriven detonation taking place as a result of the initially accelerated flame interaction with the shock reflected from channel closed-end wall appear to be the most interesting. Maximum pressures in this case can achieve hundreds of that in the initial incident shock.

Generation of flexural waves in plates by laser-initiated airborne shock waves

Results of the semi-analytical modelling of the interaction of laser-initiated airborne shock waves with an infinite horizontally positioned elastic plate are presented. The impact of the airborne shock waves on the plate is approximated by a cylindrically diverging surface force resulting from the pressure of the incident and reflected shock waves. This force is then represented in the wavenumber–frequency domain by means of Hankel and Fourier transforms that are carried out numerically so that the interaction problem can be solved using the Green’s function method. The resulting frequency spectra and time histories of generated flexural wave pulses are calculated for different values of laser pulse energy and for different heights of the laser beam focusing above the plate surface. The theoretical results obtained are compared with the results of laboratory measurements of the interaction of laser-generated acoustic shocks with a large plastic plate. The comparison shows reasonably good agreement between the semi-analytical predictions and data.

Numerical Simulations of Shock Focusing over Concave Surfaces

This paper describes the numerical study of a shock focusing, that is, a planar shock wave impacting a concave surface. Cylindrical and parabolic reflectors are studied for different curvatures, depths and incident Mach numbers. Computations are carried out using a high-order low-dissipation bandwidth-optimized weighted essentially nonoscillatory method and both inviscid and viscous two-dimensional flow models are considered. The obtained results agree well with the experimental observations made by Skews et al. (Skews, B. W., Kleine, H., Barber, T., and Iannuccelli, M., Flow Features in a Cavity During Shock Wave Impact, 16th Australian Fluid Mechanics Conference, Univ. of Queensland, Brisbane, Australia, 2007) and Izumi et al. (Izumi, K., Aso, S., and Nishida, M., Experimental and Computational Studies Focusing Processes of Shock Waves Reflected from Parabolic Reflectors, Shock Waves, Vol. 3, No. 3,1994, pp. 213-222) for the parabolic one. In the case of cylindrical reflectors, shocks interaction and fine structures as Kelvin-Helmholtz instabilities are recovered, and the computed angles of the transition from an inverse Mach reflection to a transitional regular reflection compare favorably with the analytical model of Ben-Dor (Ben-Dor, G., Shock Wave Reflection Phenomena, Springer-Verlag, New York, 1992) for relatively weak incident shock waves (M s ≤ 2). In the case of parabolic reflectors, the three types of focalization process are addressed and their own structure analyzed.

Investigation of High-Speed Ramjet Engines

This paper gives a brief overview of investigations and developments of combustion chambers of high-speed ramjet engines performed at Moscow Aviation Institute (MAI). Shadow photographs are given which show changes in the structure of regular shocks versus heat input to the flow during hydrogen combustion. The impact of oblique shock waves on combustion is studied by visualizing OH radical luminescence. Because of the significant dependence of the combustion effectiveness on the flow parameters and structure, it is relevant to study ramjet engine designs with a variable air flow duct of the combustion chamber, which allows adjustment of the working section to obtain the required parameters and characteristics over a wide range of flight conditions. A large series of tests of such combustion chambers have been performed under a joint French—Russian program. Measurement results corresponding to flight Mach numbers 2–7 are given. Mixtures of chemically pure methane and hydrogen was used as fuel. Characteristics of a three-stage heater of model flow developed at MAI for testing wide-range combustion chambers are presented.