Effect of surface gas condensation on the velocity of a reflected shock wave

The time-dependent one-dimensional problem of the normal reflection of a shock wave propagating at constant velocity in a gas (vapor) at rest from the plane surface of its condensed phase under steady-state condensation-evaporation conditions on the interphase plane is considered within the framework of the kinetic equation for a monatomic gas with a model collision operator (S-model). The solution is obtained using a conservative second-order finite-difference method. Attention is concentrated on the steady-state regime of the condensation process. The effect of the condensation (evaporation) coefficient on the velocity of the reflected shock wave is studied.     

Theoretical and experimental investigation of condensation in a centered rarefaction wave

The analysis of the process of spontaneous condensation in one-dimensional formulation is dealt with adequately in many papers. However, in reality supersonic flows are not one-dimensional. The most striking effect of two-dimensionality is manifested in two-phase flows, for example in nozzles, inclined sections of jet turbine grills and rarefaction waves. The investigation of these flows, both in the experimental and theoretical aspect, is a complex problem for which a solution has been found only recently. The results are given in this paper of a theoretical and experimental investigation of spontaneous condensation of water vapor in a centered rarefaction wave formed by flow around a protuberant angle by a hypersonic stream.Translated from Prikladnaya Mekhanika i Tekhnicheskii Fiziki, No. 5, pp. 117–122, September–October, 1971.     

The effect of an unsteady drag force on the structure of a non-equilibrium region behind a shock wave in a gas-particle mixture

For numerical analysis of shock wave propagation in gas-particle mixtures, drag coefficients of a sphere in steady flows are generally used. However, it is shown both experimentally and numerically that a shock loaded solid sphere experiences unsteady drag forces. The paper describes a model of unsteady drag force and its effect on the structure of the non-equilibrium region behind a shock front traveling in a dusty gas. The results are compared with those obtained by using a steady drag coefficient and are discussed. It is demonstrated that the large drag force at the early stage of the interaction between shock-wave induced flow and a solid particle affects the flow structure that is obtained with a steady drag force.      

侧向稀疏波对非均质凝聚炸药冲击波起爆过程的影响

以压装TNT为例,开展二维拉氏实验,利用二维锰铜-康铜组合拉氏量计测量了轴对称位置和径向位置的压力时程曲线和径向位移曲线.同时利用二维拉格朗日分析计算程序RFLA对压装TNT的冲击波起爆过程进行了计算,分别得到了在2个不同径向位置上各个Lagrange位置上的质点速度、相对比容、比内能等时程曲线.研究结果展现了侧向稀疏...     

Instability theory of shock wave in a shock tube

The instability theory of shock wave in a shock tube including the effects of tube wall and contact surface is studied. The experimental data of unstable shock wave coincide with one of instability criteria derived in the present paper.     

An investigation of electromagnetic wave propagation in plasma by shock tube

This paper presents the electromagnetic wave propagation characteristics in plasma and the attenuation coefficients of the microwave in terms of the parameters he, v, w, L, wb. The φ800 mm high temperature shock tube has been used to produce a uniform plasma. In order to get the attenuation of the electromagnetic wave through the plasma behind a shock wave, the microwave transmission has been used to measure the relative change of the wave power. The working frequency is f = (2-35)GHz (ω=2πf, wave length A =15cm-8mm). The electron density in the plasma is ne = (3×10^10-1×10^14) cm^-3. The collision frequency v = (1×10^8-6×10^10) Hz. The thickness of the plasma layer L = (2-80)cm. The electron circular frequency ωb=eBo/me, magnetic flux density B0 = (0-0.84)T. The experimental results show that when the plasma layer is thick (such as L/λ≥10), the correlation between the attenuation coefficients of the electromagnetic waves and the parameters ne,v,ω, L determined from the measurements are in good agreement with the theoretical predictions of electromagnetic wave propagations in the uniform infinite plasma. When the plasma layer is thin (such as when both L and A are of the same order), the theoretical results are only in a qualitative agreement with the experimental observations in the present parameter range, but the formula of the electromagnetic wave propagation theory in an uniform infinite plasma can not be used for quantitative computations of the correlation between the attenuation coefficients and the parameters ne,v,ω, L. In fact, if ω<ωp, v^2<<ω^2, the power attenuations K of the electromagnetic waves obtained from the measurements in the thin-layer plasma are much smaller than those of the theoretical predictions. On the other hand, if ω>ωp, v^2<<ω^2 (just v≈f), the measurements are much larger than the theoretical results. Also, we have measured the electromagnetic wave power attenuation value under the magnetic field and without a magnetic field. The result indicates that the value measured under the magnetic field shows a distinct improvement.     

Numerical simulation of 1-D unsteady two-phase flows with shocks

In the present paper, random-choice method (RCM) and second-order GRP difference method, which are high resolution methods used for pure gas flows with shocks, are extended and employed to study the problem of one-dimensional unsteady two-phase flows. The two-phase shock wave and the flow field behind it in a dusty gas shock tube are calculated and the time-dependent change of the fiow parameters for the gas antiparticle phase are obtained. The numerical results indicate that both the two methods can give the relaxation structure of the two-phase shocks with a sharp discontinuous front and that the GRP method has the advantages of less time-consuming and higher accuracy over the RCM method.     

基于主-次激波在变截面管中传播的数值模拟

采用二阶精度的单调迎风中心格式(MUSCL)和非结构自适应网格技术与有限体积形式,对轴对称变截面管道中基于主-次的爆轰波传播过程进行了数值模拟。结果表明,基于主-次的爆轰波传播至目标区时,冲击波流场均匀、稳定,波形良好;适当提高驱动段的爆炸能量,目标区能够获得预想的冲击波超压值和作用时间。     

声振耦合分析在冲击波测量中的应用

为了高精度地测量空气冲击波形,采用声振耦合分析对该测量系统的频响特性进行了理论计算,并在激波管中进行了动态响应实验。通过上述研究,得出了探头在3个不同量程时的适宜阻尼孔径。结果表明,探头的阻尼孔直径和波形上升时间的计算值与实验值都是基本符合的,并且该测量系统在强爆炸中测得的冲击波压力波形也具有良好的频响特性。     

高压氢气泄漏自燃形成喷射火的实验研究

为了探究高压氢气泄漏发生自燃时所需的临界初始释放压力随管道长度的变化规律,了解管内自燃火焰向管外喷射火焰转变的发展过程,本文利用压力、光电以及高速摄像等测试系统展开实验研究。实验结果表明：当管道长度相同,初始释放压力较低时,氢气泄漏不容易发生自燃;随着管道长度的增加,氢气发生自燃时的临界初始释放压力先缓慢减小后迅速增大;当管道长度一定时,初始释放压力越大,激波传播速度越快,氢气管内自燃的位置距离爆破片越近;气流通过激波马赫盘后,火焰燃烧加剧;随着时间的增加,火焰长度呈现先增大后逐渐减小的变化趋势,喷射火焰尖端的平均传播速度逐渐减小;火焰宽度呈现先增大后迅速减小至稳定值的变化规律。

     

Characteristics of an annular vertical diaphragmless shock tube

Abstract. This paper reports on the characteristics of a compact vertical diaphragmless shock tube, which was constructed and tested in the Shock Wave Research Center to study experimentally the behavior of toroidal shock waves. It is 1.15 m in height and has a self-sustained co-axial vertical structure consisting of a 100 mm i.d. outer tube and an 80 mm o.d. inner tube. To create a ring shaped shock wave between the inner and outer tubes, a rubber sheet is inserted to separate a high pressure driver gas from a test gas, which is bulged with auxiliary high pressure helium from the behind. When the rubber membrane is contracted by the sudden release of the auxiliary gas so as to break the seal, shock waves are formed. Special design features of the shock tube are described and their role in producing repeatable shock waves is discussed. Its special opening characteristics make possible the production of annular shaped shock waves that are unlikely met with a conventional tube that uses rupturing diaphragms. Performance of the shock tube is evaluated in terms of the shock wave Mach numbers and the measured flow properties. It eventually showed a higher degree of repeatability and the scatter in the shock wave Mach numbers Ms was found to be 0.2% for Ms ranging from 1.1 to 1.8. The shock wave Mach number so far measured agreed very well with the simple shock tube theory. Received 3 February 1999 / Accepted 6 April 2000     

激波在平板上诱导的旋涡强度的测量

运动激波通过两个等攻角平板后诱导出两个同向旋转的旋涡，这两个旋涡在随当地气流向下游运动的同时，绕涡核连线中心旋转。本文通过测量涡对的转动角度速度，获得了每个旋涡的强度。实验结果表明，由此测得的旋涡强度不同用于小攻角平板起动涡公式计算了起动涡强度。     

Mathematical model and numerical method for spontaneous potential log in heterogeneous formations

This paper introduces a new spontaneous potential log model for the case in which formation resistivity is not piecewise constant. The spontaneous potential satisfies an elliptic boundary value problem with jump conditions on the interfaces. It has beer/ shown that the elliptic interface problem has a unique weak solution. Furthermore, a jump condition capturing finite difference scheme is proposed and applied to solve such elliptic problems. Numerical results show validity and effectiveness of the proposed method.     

激波在带扩容室的变截面管中传播和消波效果的数值分析

在利用实验结果验证程序的基础上,对激波在具有复杂结构管道内的传播特性进行了数值模拟,比较了不同入射激波条件和特征尺寸对扩容室消波效应的影响,并考虑了二维(轴对称、平面)模型和三维模型的影响。计算结果表明,同一尺寸的扩容室对不同马赫数入射激波的消波效果是相近的,扩容室特征尺寸不同则消波效果差别很大。     

Focusing of Strong Shocks in an Annular Shock Tube

Focusing of strong shock waves in a gas-filled thin convergence chamber with various forms of the reflector boundary is investigated experimentally and numerically. The convergence chamber is mounted at the end of the horizontal co-axial shock tube. The construction of the convergence chamber allows the assembly of the outer chamber boundaries of various shapes. Boundaries with three different shapes have been used in the present investigation—a circle, an octagon and a smooth pentagon. The shock tube in the current study was able to produce annular shocks with the initial Mach number in the range M _s = 2.3 − 3.6. The influence of the shape of the boundary on the shape and properties of the converging and reflected shock waves in the chamber has then been investigated both experimentally and numerically. It was found that the form of the converging shock is initially governed by the shape of the reflector and the nonlinear interaction between the shape of the shock and velocity of shock propagation. Very close to the center of convergence the shock obtains a square-like form in case of a circular and octagonal reflector boundary. This is believed to stem from the instability of the converging shock front triggered by the disturbances in the flow field. The outgoing, reflected shocks were also observed to be influenced by the shape of the boundary through the flow ahead as created by the converging shocks.     

The reflection of a shock wave over a cone

An investigation was made of the reflection of planar shock waves from cones. 86 cones, the half apex angle of which varied from 10° to 52° at every 0.5°, were installed in a 60 mm×150 mm diaphragmless shock tube equipped with holographic interferometry. The diaphragmless shock tube had a high degree of reproducibility with which the scatter of shock wave Mach number was within ±0.25% for shock wave Mach number ranging from 1.16 to approximately 2.0. The reflection of shock waves over cones was visualized using double exposure holographic interferometry. Whitham's geometrical shock wave dynamics was used to analyse the motion of Mach stems over cones. It is found that for relatively smaller apex angles of cones trajectory angles of resulting irregular reflections coincide with the so-called glancing incidence angles and their Mach stems appear to be continuously curved from its intersection point with the incident shock wave, which shows the chractericstic of von Neumann reflection. The domain of the existence of the von Neumann reflection was analytically obtained and was found to be broadened much more widely than that of two-dimensional reflections of shock waves over wedges.     

Specific features of propagation of unsteady waves in a rotating spherical layer of an ideal incompressible stratified electroconducting fluid in the equatorial latitude belt

Three-dimensional large-scale motions of a rotating inviscid incompressible stratified ideal electroconducting fluid in a spherical equatorial latitude belt are studied. The mathematical model of this physical process is a closed system of partial differential equations consisting of hydrodynamic equations, which take into account the Earth rotation and the Lorentz force, and corresponding equations of magnetic dynamics with appropriate boundary conditions. An analytical solution of the system is constructed in the approximation of an equatorial β-plane, which describes propagation of lowamplitude waves.     

金属壳体装药水下爆炸的冲击波特性

为了研究装药壳体厚度对水下爆炸冲击波特性的影响,对1kg柱形含铝炸药分别在厚6mm 的钢壳或硬铝壳装药下进行了水下爆炸实验与数值模拟研究。实验结果表明,相对硬铝壳,钢壳装药的冲击波冲量、衰减时间常数以及冲击波能都偏大,而冲击波峰值相差不大。针对不同厚度钢壳装药的数值模拟表明,随着壳体厚度的增加,冲击波参数明显增强,当壳体厚度超过最优值时这种效应减弱;金属壳的存在导致冲击波峰值爬升产生滞后效应;对一定质量的炸药,存在可有效提高冲击波压力峰值的最优壳厚,填装比可以作为衡量效果的重要指标。