Two-Dimensional Gas-Dynamic Modeling of the Interaction of a Shock Wave with Beds of Granular Media

A two-dimensional numerical parametric study is made of the interaction of a shock wave with a system of cylinders modeling a bed of a granular medium. The mathematical model is based on the Euler equations. The integration of the defining system of equations in a multiply connected domain is taken using an original computational algorithm of the Cartesian grid method. Computational experiments are carried out with various values for bed permeability and length, the diameter of the cylinder, and channel width. The formulation of the problem imitates natural experiments. The results of all the computational experiments in terms of overpressure behind the reflected and transmitted waves are generalized using a dimensionless criterion. The calculated results are compared with the data from the natural experiments.     

Interaction of an Optical Discharge with a Shock Wave

The results of an experimental study of the impact of the focused pulsed-periodic radiation from a CO₂ laser on a gas-dynamic structure in a supersonic jet are presented. The radiation of the CO₂ laser is propagated across the stream and focused by a lens on the axis of the supersonic jet. To register the flow structure, a shadow scheme with a slit and a flat knife located along the flow is used. The image is fixed by a speed camera with an exposure time of 1.5 μs and a frame rate of 1000 1/s. In the flow, the plasma initiated by the pulsedperiodic laser is visualized in order to identify and determine the period of plasma development, as well as the motion of the initial front of the shock wave. It is shown that at the transverse input of laser radiation into the stream the periodic structure of the thermal trace is created with the formation of an unsteady shock wave from the energy release zone. At small repetition rates of laser radiation pulses, the thermal spot interacts with the flow in the pulsed mode. It is shown that elliptic nonstationary shock waves are formed only at low subsonic flow velocities and in a stationary atmosphere. The process of nonstationary ignition by an optical discharge of a methane–air mixture during a subsonic outflow into a motionless atmosphere is shown experimentally. The results of optical visualization indicate burning in the trace behind the optical discharge region.     

Modeling and Simulation of Gruneisen Parameter for a Shock Wave

Russian Physics Journal - The paper presents modeling and simulation of the Gruneisen parameter depending on the volume and temperature using the principal Hugoniot, isentropes and the Gruneisen...     

正冲击波后固壁表面颗粒的上升运动

为揭示固壁表面颗粒的冲击波夹卷本质,模拟垂直于固壁表面的正冲击波后单个颗粒的上升运动.假定颗粒初始时刻处于气载状态(因波的反射或碰撞离开壁面),受Saffman升力、气动阻力和重力作用.模型方程为波后定常气流边界层方程和颗粒运动常微分方程,分别用单参数法和四阶龙格库塔法求解.计算颗粒速度与轨迹表明:颗粒的冲击波卷扬动力...     

Modeling of a Wide Class of Static Stars Within the Framework of a Unified Approach

A class of static spherically symmetrical models of relativistic stars with a preset energy density distribution is examined. An analytical expression for an approximate solution of the Einstein equations is derived by the method of successive approximations in terms of a small parameter determining the star compactness. Equilibrium star configurations are constructed for a family of models and their stability and basic physical characteristics are investigated. The results of modeling of three different astrophysical objects (a neutron star, a white dwarf (Sirius B), and a star of the main sequence (Sun)) have been compared with the available observational data. This allows us to conclude that the suggested model approach is applicable to a wide class of stars.     

MHD Wave Interaction within a Plasma Perturbed by Alfvén Waves

The interaction between fast magnetoacoustic waves within a plasma with periodical nonhomogeneities, perturbed by Alfvén waves has been studied. It has been ascertained the appearance of phenomena of a decay instability and an instability involving an increase of the amplitude oscillations. A study of the influence of perturbed plasma parameters on these instability phenomena has been made. It has been found that the optimal perturbing frequency for giving rise to the instability phenomenon is twice the frequency of fast magnetoacoustic waves.     

利用冲击波作用光子晶体产生蓝光的研究

研究了一种利用冲击波作用光子晶体产生蓝光的新方法.通过模拟光子晶体受冲击波作用后折射率的变化,对470 nm蓝光,设定光子晶体的参量,研究了冲击波引起光子晶体带隙的变化,计算了需要冲击波的速度,分析了影响蓝光线宽和中心波长的因素.结果表明,变频后的光波线宽随冲击波和固定反射面的距离而变化,距离大时,线宽较小,距离小时,线宽较大,可以利用光子晶体的滤波作用对输出光波线宽进行控制,获得带宽稳定的或变化的输出光波.环境温度变化、光子晶体材料吸收特性影响光子晶体的带隙分布,进而影响蓝光的中心波长.研究结果对研制新的蓝光光源具有重要参考价值,同时也为其他相干光源的产生提供了一种新的技术.     

利用冲击波作用光子晶体产生蓝光的研究

研究了一种利用冲击波作用光子晶体产生蓝光的新方法.通过模拟光子晶体受冲击波作用后折射率的变化,对470nm蓝光,设定光子晶体的参量,研究了冲击波引起光子晶体带隙的变化,计算了需要冲击波的速度,分析了影响蓝光线宽和中心波长的因素.结果表明,变频后的光波线宽随冲击波和固定反射面的距离而变化,距离大时,线宽较小,距离小时,线宽较大,可以利用光子晶体的滤波作用对输出光波线宽进行控制,获得带宽稳定的或变化的输出光波.环境温度变化、光子晶体材料吸收特性影响光子晶体的带隙分布,进而影响蓝光的中心波长.研究结果对研制新的蓝光光源具有重要参考价值,同时也为其他相干光源的产生提供了一种新的技术.     

Kinetic Description of Particle Interaction with a Gravitational Wave

The interaction of charged particles, moving in a uniform magnetic field, with a plane polarized gravitational wave is considered using the Fokker-Planck-Kolmogorov (FPK) approach. By using a stochasticity criterion, we determine the exact locations in phase space, where resonance overlapping occurs. We investigate the diffusion of orbits around each primary resonance of order m by deriving general analytical expressions for an effective diffusion coefficient. A solution of the corresponding diffusion equation (Fokker-Planck equation) for the static case is found. Numerical integration of the full equations of motion and subsequent calculation of the diffusion coefficient verifies the analytical results.     

Consolidation of Bimetallic Nanosized Particles and Formation of Nanocomposites Depending on Conditions of Shock Wave Compaction

Russian Physics Journal - The authors consider and evaluate the physical parameters and regularities of the process of consolidation of Fe–Cu, Cu–Nb, Ag–Ni, Fe–Pb...     

Interaction of Wave Trains with Defects

The evolution and transition of planar wave trains propagating through defects(obstacles) in an excitable medium are studied. When the frequency of the planar wave trains is increased, three different dynamical regimes,namely fusion, "V" waves, and spiral waves, are observed in turn and the underlying mechanism is discussed. The dynamics is concerned with the shapes of the defects. Circle, triangle, and rectangle defects with different sizes are considered. The increase of pacing frequency broadens the fan-shaped broken region in the behind of a rectangle defect.The increase of width of a triangle defect leads to breakup of wave trains easier while the change of height shows opposite effect, which is presented in a phase diagram. Dynamical comparison on defects with different shapes indicates that the decrease of the defect width along the propagation of wave trains makes the fan-shaped region and the minimal frequency for breakup of spiral both increased.     

Supersonic Shock Wave with Landau Quantization in a Relativistic Degenerate Plasma

A three-dimensional(3D)BurgersJ equation adopting perturbative methodology is derived to study the evolution of a shock wave with Landau quantized magnetic field in relativistic quantum plasma.The characteristics of a shock wave in such a plasma under the influence of magnetic quantization,relativistic parameter and degenerate electron density are studied with assistance of steady state solution.The magnetic field has a noteworthy control,especially on the shock wave's amplitude in the lower range of the electron density,whereas the amplitude in the higher range of the electron density reduces remarkably.The rate of increase of shock wave potential is much higher(lower)with a magnetic Held in the lower(higher)range of electron density.With the relativistic factor,the shock wave's amplitude increases significantly and the rate of increase is higher(lower)for lower(higher)electron density.The combined effect of the increase of relativistic factor and the magnetic field on the strength of the shock wave,results in the highest value of the wave potential in the lower range of the degenerate electron density.     

Interaction of a Surface Acoustic Wave with a Two-dimensional Electron Gas

When a surface acoustic wave (SAW) propagates on the surface of a GaAs semiconductor, coupling between electrons in the two-dimensional electron gas beneath the interface and the elastic host crystal through piezoelectric interaction will attenuate the SAW. The coupling coefficient is calculated for the SAW propagating along an arbitrary direction. It is found that the coupling strength is strongly dependent on the propagating direction. When the SAW propagates along the [011] direction, the coupling becomes quite weak.     

Interaction of a Surface Acoustic Wave with a Two-dimensional Electron Gas

When a surface acoustic wave （SAW） propagates on the surface of a GaAs semiconductor, coupling between electrons in the two-dimensional electron gas beneath the interface and the elastic host crystal through piezoelectric interaction will attenuate the SAW. The coupling coemcient is ~alculated for the SAW propagating along an arbitrary direction. It is found that the coupling strength is strongly dependent on the propagating direction. When the SAW propagates along the [011] direction, the coupling becomes quite weak.     

Semi-Relativistic Two-Body States of Spinless Particles with a Scalar-Type Interaction Potential

A semi-relativistic quantum approximation for mutual scalar interaction potentials is outlined and discussed.Equations are consistent with two-body Dirac equations for bound states of zero total angular momentum. Two-body effects near the non-relativistic limit for a linear scalar potential is studied in some detail.     

Extraction of the Shock Adiabat of Metals from the Decay Characteristics of a Shock Wave in a Laser Experiment

JETP Letters - A method has been proposed to extract the shock adiabat of metals, including the thermal component of the pressure, from the measured decay characteristics of a strong shock wave...     

带电粒子与超晶格相互作用及其超高能粒子识别

讨论了非沟道粒子与晶体的相互作用及其渡越辐射, 并将渡越辐射同沟道辐射进行了比较, 结果表明, 渡越辐射对沟道辐射的贡献主要是在长波区域使沟道辐射的本底增强; 由于超晶格是由两种不同介电性能的材料交替生长而成的多层薄膜结构, 它的渡越辐射比较强. 正是这个特点, 可望利用超晶格的渡越辐射来识别超高能粒子.     

Modelling of Bound States of Dirac Particles in Singular Background in Framework of Symanzik Approach

The problem of interaction of the fields of quantum electrodynamic with material macro-object is considered by employing the Symanzik approach on modelling the interaction of quantum field with space-time inhomogeneities. Results obtained in the models with Chern–Simons interaction of photon field with 2-dimensional material are briefly reviewed. In the model of interaction of spinor field with homogeneous isotropic material plane constructed in framework of Symanzik approach, the bound states are considered. For localized near plane Dirac particle the dispersion relation and the expressions for current, charge and density are analyzed. The bound states with massless dispersion law is considered. The presented methods of modelling can find application to a wide class of phenomena emerging from the interaction of quantum fields with extended material structures.     

内聚锥形激波的非均匀强化与结构演变特征

以高超声速内转式进气道流动中的激波汇聚问题为背景,考虑工程实际中的来流和壁面几何条件这两个关键因素,分别提出了以来流攻角为研究参数的非轴向来流内锥流动模型,和以长/短轴比为研究参数的椭圆入口内锥流动模型.采用激波风洞实验观测和数值模拟相结合的方法,揭示了两类流动中激波的非均匀汇聚特征.结果表明:由来流攻角引起的激波初始...     

Self-Similar Solution of Spherical Shock Wave Propagation in a Mixture of a Gas and Small Solid Particles with Increasing Energy under the Influence of Gravitational Field and Monochromatic Radiation

Similarity solution for a spherical shock wave with or without gravitational field in a dusty gas is studied under the action of monochromatic radiation. It is supposed that dusty gas be a mixture of perfect gas and micro solid particles. Equilibrium flow condition is supposed to be maintained and energy is varying which is continuously supplied by inner expanding surface. It is found that similarity solution exists under the constant initial density. The comparison between the solutions obtained in gravitating and non-gravitating medium is done. It is found that the shock strength increases with an increase in gravitational parameter or ratio of the density of solid particles to the initial density of the gas, whereas an increase in the radiation parameter has decaying effect on the shock waves.