共查询到20条相似文献,搜索用时 140 毫秒
1.
S. G. Chefranov 《Journal of Experimental and Theoretical Physics》2020,130(4):633-642
A new condition is obtained for the linear instability of a plane front of an intense shock wave in an arbitrary medium, which is determined by the finiteness of the viscosity. It is shown that the shock front instability occurs due to dissipative instability of the flow behind the front, which is analogous to the flow instability in the boundary layer. It is found that in the low-viscosity limit, one-dimensional longitudinal perturbations increase much faster than two-dimensional (corrugation) perturbations. The results are compared with the available data of experimental observation and numerical simulation of instability of shock waves. The comparison shows a better agreement between the new absolute shock instability as compared to the condition of such instability in the classical D’yakov theory disregarding viscosity. 相似文献
2.
3.
Based on experimental research in shock loading of solid-state materials it is shown that among the important dynamic characteristics of the process, like spatial-temporal mass velocity profiles of shock waves, are the mass velocity variation, velocity defect, and structural instability threshold recorded in real time. Analysis of these characteristics depending on the strain rate, target thickness, and structural state of material demonstrates that conventional approaches of continuum mechanics fail to provide their adequate interpretation and simulation of shock wave processes. A new concept of shock wave processes in condensed media is proposed. The concept, being based on nonlocal nonequilibrium transport theory, allows describing the transition from elastic to hydrodynamic response of a medium depending on the loading rate and time. A nonstationary elastoplastic wave model is proposed for describing the relaxation of an elastic precursor and formation of a retarded plastic front during the wave propagation in a medium with regard to structural evolution. Analysis of the experimental data shows that the division of stresses and strains into elastic and plastic components is incorrect for shock loading. 相似文献
4.
在二级轻气炮上,用高速电子相机扫描照相技术和改进的Mallory实验装置,对z切LiF,Al2O3(蓝宝石)和LiTaO3单晶材料的冲击透光性进行了对比测量,并用黑密度计提取出动态图像定量化的光强对比度变化曲线.结果表明,LiF单晶在102GPa压强下能够保持长时间的初始透光性不变,与公认的LiF具有优良的高压下透明性的认识一致.LiTaO3单晶在实验压力(139GPa)下变成基本不透明.而Al2O3单晶在131GPa冲击压力下则表现为透明性逐渐下降直至完全不透明. 相似文献
5.
6.
7.
A mechanism of action of a shock wave on an active medium, which leads to an additional energy release source, is considered.
This source moves together with the shock wave front and depends on the magnitude and direction of the electric field applied
to the plasma and on the current density in the plasma. The study is a continuation of an earlier publication devoted to the
propagation of weak shock waves. Here, we consider shock waves of an arbitrary intensity with an arbitrary mechanism of formation
of an additional energy contribution due to variation of the parameters of the medium as a result of passage of the shock
wave. Special cases of this effect are the propagation of a shock wave in a plasma and detonation burning. 相似文献
8.
在二级轻气炮上,用高速电子相机扫描照相技术和改进的Mallory实验装置,对z切LiF,Al2O3(蓝宝石)和LiTaO3单晶材料的冲击透光性进行了对比测量,并用黑密度计提取出动态图像定量化的光强对比度变化曲线.结果表明,LiF单晶在102 GPa压强下能够保持长时间的初始透光性不变,与公认的LiF具有优良的高压下透明性的认识一致.LiTaO3单晶在实验压力(139GPa)下变成基本不透明.而Al关键词:
2O3')" href="#">Al2O3
LiF
3')" href="#">LiTaO3
光学透明性 相似文献
9.
10.
The propagation of a step-shaped shock wave in a liquid is investigated experimentally. The liquid contains spherical three-phase
clusters (liquid, solid balls, gas bubbles). A comparison of the experimental data on the velocity and wave structure with
calculations with the use of the Boussinesq equation for a three-phase cluster medium is made. It is shown that the sound
speed in a three-phase medium of cluster structure is higher than in a homogeneous three-phase medium. 相似文献
11.
A new multiscale simulation method is formulated for the study of shocked materials. The method combines molecular dynamics and the Euler equations for compressible flow. Treatment of the difficult problem of the spontaneous formation of multiple shock waves due to material instabilities is enabled with this approach. The method allows the molecular dynamics simulation of the system under dynamical shock conditions for orders of magnitude longer time periods than is possible using the popular nonequilibrium molecular dynamics approach. An example calculation is given for a model potential for silicon in which a computational speedup of 10(5) is demonstrated. Results of these simulations are consistent with the recent experimental observation of an anomalously large elastic precursor on the nanosecond time scale. 相似文献
12.
The potential of using the Euler equations to numerically simulate the evolution of localized energy deposition zones interacting with a normal shock in quiescent air and in a supersonic channel flow is demonstrated. Simulation results are compared with available experimental data for an optical discharge in quiescent air and with results calculated for a supersonic flow using the Navier-Stokes equations with allowance for real gas effects. The possibility of predicting gasdynamic effects using the T- and q-models of energy deposition for perfect gas is justified. The variation of the gasdynamic structure and flow parameters near an energy deposition zone developing in a quiescent medium and interacting with a normal shock is analyzed in detail for different energy deposition powers. 相似文献
13.
采用Matsui和Anderson提出的Morse型有效原子对势及导带电子热激发能贡献,通过分子动力学方法(MD)对多孔铁的冲击温度进行了数值模拟。计算时,采用了在一定冲击压力下多孔铁样品已转变为均匀介质的近似。多孔铁冲击温度的模拟结果与经合理修正后的热力学计算结果相一致。这个结果表明:在一定的冲击压力下,多孔材料样品确实存在一个热力学平衡状态下的温度值。以上结论可能也适用于更高孔隙率的样品,当然这一观点还需要更多的实验结果给予证实。 相似文献
14.
15.
Freedman B Carmon T Carvalho MI Segev M Christodoulides DN 《Physical review letters》2003,91(13):133902
We report the first experimental observation of optical spatial shock-wave pairs. The shock waves consist of two coupled kink and antikink beams that remain locked to each other throughout propagation in a nonlinear diffusion-driven photorefractive crystal. These coupled shock-wave pairs move undistorted at angles that fall outside their original angular sector of propagation. 相似文献
16.
17.
Neshev DN Alexander TJ Ostrovskaya EA Kivshar YS Martin H Makasyuk I Chen Z 《Physical review letters》2004,92(12):123903
We report on the first experimental observation of discrete vortex solitons in two-dimensional optically induced photonic lattices. We demonstrate strong stabilization of an optical vortex by the lattice in a self-focusing nonlinear medium and study the generation of the discrete vortices from a broad class of singular beams. 相似文献
18.
A. V. Konyukhov A. P. Likhachev A. M. Oparin S. I. Anisimov V. E. Fortov 《Journal of Experimental and Theoretical Physics》2004,98(4):811-819
A numerical analysis of the nonlinear instability of shock waves is presented for solid deuterium and for a model medium described by a properly constructed equation of state. The splitting of an unstable shock wave into an absolutely stable shock and a shock that emits acoustic waves is simulated for the first time. 相似文献
19.
Sapozhnikov OA Maxwell AD MacConaghy B Bailey MR 《The Journal of the Acoustical Society of America》2007,121(2):1190-1202
In vitro experiments and an elastic wave model were used to analyze how stress is induced in kidney stones by lithotripsy and to test the roles of individual mechanisms-spallation, squeezing, and cavitation. Cylindrical U30 cement stones were treated in an HM-3-style lithotripter. Baffles were used to block specific waves responsible for spallation or squeezing. Stones with and without surface cracks added to simulate cavitation damage were tested in glycerol (a cavitation suppressive medium). Each case was simulated using the elasticity equations for an isotropic medium. The calculated location of maximum stress compared well with the experimental observations of where stones fractured in two pieces. Higher calculated maximum tensile stress correlated with fewer shock waves required for fracture. The highest calculated tensile stresses resulted from shear waves initiated at the proximal corners and strengthened along the side surfaces of the stone by the liquid-borne lithotripter shock wave. Peak tensile stress was in the distal end of the stone where fracture occurred. Reflection of the longitudinal wave from the distal face of the stone--spallation-produced lower stresses. Surface cracks accelerated fragmentation when created near the location where the maximum stress was predicted. 相似文献
20.
Noginov MA Zhu G Bahoura M Adegoke J Small CE Ritzo BA Drachev VP Shalaev VM 《Optics letters》2006,31(20):3022-3024
We have observed the compensation of loss in a metal by a gain in a dielectric medium in the mixture of an Ag aggregate and a Rhodamine 6G dye. The demonstrated sixfold enhancement of the Rayleigh scattering is the evidence of the enhancement of the surface-plasmon resonance. The reported experimental observation facilitates many applications of nanoplasmonics. 相似文献