Instability theory of shock wave in a channel

The instability theory of shock wave was extended from the case with an infinitefront to the case of a channel with a rectangular cross section.First,themathematical formulation of the problem was given which included a system ofdisturbed equations and three kinds of boundary conditions.Then,the general solutionsof the equations upstream and downstream were given and each contained fiveconstants to be determined.Thirdly,under one boundary condition and oneassumption,it was proved that all of the disturbances in front of the shock front andone of the two acoustic disturbances behind the shock front should be zero.Theboundary condition was that all of the disturbed physical quantities should approach tozero at infinity.The assumption was that only the unstable shock wave was concernedhere.So it was reasonable to assumeω=iγ,γwas the instability growth rate andwas a positive real number.Another kind of boundary conditions was that the normaldisturbed velocities should be zero at the solid wall of the cha     

电磁加速等离子体喷涂技术的原理分析

对自行研制的电磁加速等离子体喷涂技术（Electromagnetically accelerated plasma spraying,EMAPS）从原理上进行了分析,建立了等离子体的运动方程,得到了脉冲电流作用下等离子体上任一点的磁感应强度的计算公式和等离子体及它所压缩周围空气的速度表达式;并分析了粉末粒子与冲击波的相互作用,得到了粉末粒子的喷涂速度与喷枪长度、粉末粒子直径以及电流强度之间的关系;同时还对喷枪的长度进行了设计。     

一种新的运动激波--非定常边界层相互干扰现象

本文探讨了一种新的激波－非定常边界层相互干扰现象，这种激波－边界层干扰现象既不同于定常激波－边界层干扰现象，又不同于激波在端面反射后与该激波所诱导的边界层之间的干扰现象，而是运动激波与稀疏波和第一激波所诱导的非这常边界层之间的干扰现象，本文对这种现象用微波动力学理论进行分析，并把这种干扰现象看成激波的绕射现象，同时在稀疏波破膜的双驱动激波管中进行实验观察，最后把理论分析与实验观察进行了比较。     

静水压力对岩石在等离子体冲击下压裂效果的影响

为了了解与掌握深井下水中放电冲击波对岩石的破碎作用规律,建立了静水压力高达35 MPa的电脉冲压裂装置,可模拟深井近3 000 m下的围压,并进行了不同静水压下等离子体冲击压裂实验。电脉冲压裂装置最高工作电压20 kV,最大储能40 kJ。在0~25 MPa的静水压力条件下,对6块砂岩岩样进行了冲击压裂实验。实验结果表明,随着静水压力的升高,相同放电条件下压裂产生的裂缝长度和宽度明显降低。所以静水压力的升高将使得岩样损伤范围减小,孔隙度以及渗透率提升幅度下降。静水压力对冲击压裂后裂缝的形成、分布、生长具有明显的影响。与常压下形成的裂缝相比,施加围压后裂缝多集中在电极处,数量多,但是长度较短,存在不同程度的弯曲,甚至局部区域出现了环形裂缝。

     

Lifting of Disperse Particles from a Cavity Behind the Front of an Unsteady Shock Wave with a Triangular Velocity Profile

The gas flow in plane shock waves slipping along an impermeable surface with a rectangular cavity where solid disperse particles are suspended is considered numerically. The motion of the gas and particles (gas suspension) is modeled by equations of mechanics of multiphase media. Some laws of the behavior of the dusty cloud in the cavity are established for the case of wave interaction with the cavity.     

Gas-dynamic approach in the nonlinear theory of ion acoustic waves in a plasma: An exact solution

An exact solution of the problem of the acoustic wave structure in a plasma is obtained. Both plasma component are treated as gases with specified initial temperatures and adiabatic exponents. The system of equations describing the wave profile is solved using an original method consisting of reducing the system to the Bernoulli equation. A numerical example of the obtained general solution of the problem of the wave profile for arbitrary parameters is given. Curves are constructed that bound the region of existence of a stationary solitary ion acoustic wave in the parameter space. __________ Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 48, No. 5, pp. 3–11, September–October, 2007.     

Charge transfer by high-energy electrons onto the leeward surfaces of a solid in a supersonic rarefied plasma flow

Numerical and experimental dependence of equilibrium potentials of the leeward surfaces on the ratio of concentrations of high-energy electrons and positive ions in a supersonic rarefied plasma flow around a solid are obtained. __________ Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 49, No. 1, pp. 13–23, January–February, 2008.     

动高压加载下锆基金属玻璃强度测量

为了研究Zr₅₁Ti₅Ni₁₀Cu₂₅Al₉金属玻璃的高压强度特性,进行了平靶冲击实验。采用反向碰撞方式,运用DISAR技术测量金属玻璃样品/LiF窗口界面粒子速度剖面,分析粒子速度剖面获得了37~66GPa压力范围锆基金属玻璃的屈服强度和剪切模量。实验结果表明,在上述压力范围金属玻璃的屈服强度和剪切模量均显示出一定程度的压力硬化效应,分析表明金属玻璃冲击加载波阵面剪应力衰减并非由损伤/破坏或温度软化等因素导致。

     

Theory of unsteady separation in supersonic flow around a convex corner

A theory of unsteady separation in inviscid supersonic flow around a convex corner is developed. Within the framework of the hypothesis suggested the mechanism of separationless-to-separated flow transition is explained and the forces leading to flow separation are determined as functions of the angle θ and the oncoming flow velocity. The values of the angle θ _k at which the flow is separated from the corner vertex and the stall angle θ _s determining the separated flow direction obtained previously in experiments and by numerical simulation are confirmed.     

Unsteady interaction of shock wave diffracting around a circular cylinder in air

The reflection and diffraction of a planar shock wave around a circular cylinder are a typical problem of the complex nonlinear shock wave phenomena in literature. It has long been studied experimentally, analytically as well as numerically. Takayama in 1987 obtained clear experimental pictures of isopycnics in shock tube under the condition that the impinging shock wave propagates as far as 3 diameters away from the cylinder. To know more completely the whole unsteady process, it is desirable to get experimental results in a region which is more than 10 diameters away from the cylinder. This is what has been done in this paper by using the pulsed laser holographic interferometry for several shock Mach numbers of the impinging shock. Results for several moments are shown, giving more knowledge about the whole unsteady flow field. This is useful for a reliable and complete understanding of the changing force acting on the cylinder, and provides interesting data to check the performance of many recently developed high resolution numerical methods for unsteady shock wave calculation. The project suported partially by National Natural Science Foundation of China     

The problem of radiation transport in the channels of a polysectional thermodynamic system

The problem of radiation energy transfer in ballistic radiative-gas compression facilities is considered. For constructing mathematical models of these facilities, an algorithm for splitting the thermodynamic system into sections (with consideration of the interconnections of the polysectional system) is used. The conditions of applicability of the thermodynamic approach to describing the processes in a ballistic plasmotron are established. It is shown that, in most practical problems, the losses in the intersectional channels are insignificant as compared with the losses in the sections and can be neglected.