Interaction of a Shock Wave with a Spherical Gas–Liquid Cluster

Experimental studies were performed of the interaction of a plane shock wave with a spherical gas–liquid cluster (polyurethane foam ball saturated with a bubbly liquid) in a vertical shock tunnel filled with a liquid. The cluster was shown to generate a solitary pressure wave of large amplitude.     

Interaction of a Streamwise Vortex with an Oblique Shock Wave

Interaction of a supersonic streamwise vortex with an oblique shock wave is considered. A mathematical model of the streamwise vortex is constructed. Three interaction regimes (weak, moderate, and strong) are found. It is shown numerically that vortex breakdown is possible in the case of strong interaction. The influence of the governing parameters on the interaction type is studied. It is shown that the main effect on the interaction type is exerted by the streamwise velocity and angle of the wedge forming the shock wave. The effect of splitting of the primary vortex on the shock wave in the case of moderate and strong interaction regimes is found.     

Evolution of the Diffusion Mixing Layer of Two Gases upon Interaction with Shock Waves

A mathematical model of mechanics of a twovelocity twotemperature mixture of gases is developed. Based on this model, evolution of the mixing layer of two gases with different densities under the action of shock and compression waves is considered by methods of mathematical simulation in the onedimensional unsteady approximation. In the asymptotic approximation of the full model, a solution of an initialboundary problem is obtained, which describes the formation of a diffusion layer between two gases. Problems of interaction of shock and compression waves with the diffusion layer are solved numerically in the full formulation. It is shown that the layer is compressed as the shock wave traverses it; the magnitude of compression depends on shockwave intensity. As the shock wave passes from the heavy gas to the light gas, the mixing layer becomes overcompressed and expands after shockwave transition. The wave pattern of the flow is described in detail. The calculated evolution of the mixinglayer width is in good agreement with experimental data.     

Interaction of a gasdynamic shock with small disturbances

The stability of shock wave based on the definition of Landau and Lifschitz^[1] is treated in this paper. This is tantamount to solving the problem of interaction of small disturbances with a shock wave. Small disturbances are introduced on both sides of a steady, non-dissipative, plane shock wave. Landau et al.^[1] obtained the stability criterionM ₁>1,M ₂<1 for small disturbances which are travelling in the direction perpendicular to the shock wave. In the present paper, we assume that the small disturbances may be two dimensional, i.e. they may be propagating in the direction inclined to the shock wave. The conclusions obtained are: regardless of whether the incident wave and diverging wave are defined according to the direction of the phase velocity or the group velocity, the shock wave is unstable for some frequencies and longitudinal wave lengths of the disturbances, even if the conditionsM ₁>1,M ₂<1 are fulfilled. Then several experiments are proposed, and the problem of ways to define the incident wave and diverging wave is discussed. The meaning of this problem is illustrated. The same results can be obtained for the steady shock wave in a tube.     

机动方舱核爆炸冲击波动力响应和安定性分析

本文以核爆炸当量、高度、距离为参数，采用等超压圆给出了普通方舱和防核加固方舱结构在核冲击波下的安全域。研究了限制舱体倾斜的压力条件。本文还以冲击波压力的时间函数为激励，求解了方舱的动力响应。从试验结果推论和计算模拟两方面，分析了方舱承受冲击波的能力。     

Momentum and Energy Transfer in a Shock Wave

The macroparameter profiles in a strong shock wave propagating in a single-component monatomic gas are investigated. The interaction between the molecules is described by the variable-diameter sphere model. Qualitative information concerning the shock wave parameters is obtained by direct statistical simulation (Monte-Carlo) method. Using the data obtained, simple approximate gas-velocity dependences of the stress and the heat flow are found and the linear Newton and Fourier relations are generalized.     

Propagation of the Energy of Nonlinearly Elastic Plane Waves

The propagation of the energy of nonlinearly elastic plane waves in a Murnaghan material is simulated on a computer. The velocity of energy propagation is found in an explicit form. A procedure of determining the critical values of the time and space coordinates for the given material is described. The resultant plots are discussed and analyzed     

Interaction Between a Slow Magnetohydrodynamic Shock Wave and a Tangential Discontinuity

The self-similar problem of the oblique interaction between a slow MHD shock wave and a tangential discontinuity is solved within the framework of the ideal magnetohydrodynamic model. The constraints on the initial parameters necessary for the existence of a regular solution are found. Various feasible wave flow patterns are found in the steady-state coordinate system moving with the line of intersection of the discontinuities. As distinct from the problems of interaction between fast shock waves and other discontinuities, when the incident shock wave is slow the state ahead of it cannot be given and must to be determined in the process of solving the problem. As an example, a flow in which the slow shock wave incident on the tangential discontinuity is generated by an ideally conducting wedge located in the flow is considered. The basic features of the developing flows are determined.     

Computations of Interaction of an Incident Oblique Shock Wave with a Turbulent Boundary Layer on a Flat Plate

Results of numerical simulation of interaction between an oblique shock wave and a turbulent boundary layer formed in a supersonic (Mach number M =5) flow past a flat plate are presented. The computations are performed for three cases of interaction of different intensity, which result in an attached or detached flow. Numerical results are compared with experimental data. The effect of flow turbulence and shockwave unsteadiness on flow parameters is studied.     

Formation and Amplification of Shock Waves in a Bubble “Cord”

The structure and dynamics of the wave field generated by a bubble system in the form of an axial bubble cylinder (cord) excited by a plane shock wave propagating along the axis in an axisymmetric shock tube are numerically examined. It is shown that consecutive excitation of oscillations of the bubble zone results in formation of a quasi-steady shock wave in the cord and in the ambient liquid. Results of the numerical analysis of the maximum amplitude of the resulting wave as a function of problems parameters are described.__________Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 46, No. 5, pp. 46–52, September–October, 2005.     

Collective Bow Shock Ahead of a Transverse System of Spheres in a Supersonic Flow Behind a Moving Shock Wave

The results of investigating the dynamics and physical conditions of formation of a collective bow shock ahead of a system of spheres with the line of centers normal to the supersonic flow behind a traveling shock wave are presented. Two types of shock-wave patterns that necessarily precede the formation of the collective shock wave and correspond to regular and Mach interaction of the bow shocks were detected experimentally. On the basis of a local gasdynamic-discontinuity interference theory, quantitative criteria of the existence of these regimes and of the formation of a common shock wave are determined. These criteria are confirmed in a series of experiments for the transitional regimes.     

Instability of an Interface between Steel Layers Acted upon by an Oblique Shock Wave

This paper reports results of experiments in which development of instability was observed on the interface between two identical metals in tight contact with passage of an oblique shock wave through it. Numerical modeling of experimental results was performed by a twodimensional Lagrangian procedure using an elastoplastic model with a functional dependence of the dynamic yield point on the state variables of the material. The calculations showed that perturbations develop only in the presence of a technological microgap of several tens of micrometers between the metal layers. Unloading of the material behind the oblique shock front into the gap gives rise to a considerable shortterm velocity gradient. Simultaneously, near the interface behind the wave front there is a shortterm loss of strength of the material due to thermal softening and the heterogeneous nature of the deformation.     

Dynamics of a Gas Bubble during Its Interaction with Compression and Rarefaction Waves

The problem of the passage of acoustic waves in the neighborhood of a gas bubble in a tube is formulated and solved numerically. The main parameters determining the bubble dynamics in a non-stationary field are determined. The mechanism of jet deformation of the bubble followed by jet fragmentation and formation of a secondary small-size bubble fraction is studied. A possible explanation of the nature of local sonoluminiscence is proposed.__________Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 46, No. 5, pp. 76–85, September–October, 2005.     

Problems on Nonstationary Interaction of Structural Elements with Shock Waves

Experimental investigations into the interaction of rigid and elastic structure elements with a shock wave in water and in air are reviewed. Investigation techniques are described and the nonstationary behavior of elements is analyzed     

Dynamics of a Flexible Slider-Crank Mechanism Driven by a Non-Ideal Source of Energy

The dynamic response of a slider crank mechanism with a flexible connecting rod driven by an electric DC motor is examined. After formulating the governing nonlinear boundary value problem, it is reduced by a one-term truncation to a system of nonlinear ordinary differential equations representing the complete dynamics of the electromechanical system. First, the steady-state behavior is analyzed. It turns out that a constant crank rotational speed is not possible: fluctuations appear which can be limited by an appropriate choice of the system and the engine data. Then, the transient startup or rundown is dealt with by using a digital simulation of the model equations. It exhibits a rich variety of dynamic effects till the stationary speed is reached. Attention is focused on the influence of the flexibility which in both categories of motion yields typical features.     

Investigation of the Nitrogen Shock Wave Structure on the Basis of Trajectory Calculations of the Molecular Interaction

The shock wave structure in a diatomic gas is investigated using the direct statistical simulation (Monte-Carlo) method. The energy exchange between translational and rotational degrees of freedom (TR-exchange) is calculated by solving the dynamic problem of the interaction between rigid-rotator molecules within the framework of classical mechanics. The density profiles calculated are compared with the experimental data and on this basis the nitrogen rotational relaxation time is estimated. The possibility of using simplified intermolecular interaction models, namely, the variable-diameter sphere model employed together with a phenomenological consideration of the TR-exchange, is studied. Gasdynamic parameter profiles in the shock wave are analyzed. Simple approximations of the velocity gradient and translational and rotational temperature profiles are obtained on the basis of a parametric calculation of the shock wave structure. This makes it possible approximately to describe the gasdynamic parameter profiles in terms of elementary functions.     

Self-Localization of the Energy Supply During Pulse Ionization of a Supersonic Flow

The pulse ionization of the time-dependent quasi-two-dimensional flow developed during diffraction of a shock wave on a wedge is investigated experimentally. The redistribution of the pulse volume discharge plasma subjected to preionization by ultraviolet radiation from plasma sheets is investigated when the discharge is initiated in different stages of the time-dependent gas dynamic flow. Images of the plasma flow are compared with the corresponding fields of the gas dynamic flow parameters. It is shown that the pulse discharge plasma flows can be controlled due to the phenomenon of self-localization in a given flow zone of known shape. The local energy supply to the gasdynamic flow is simulated numerically using the experimental data.__________Translated from Izvestiya Rossiiskoi Academii Nauk, Mekhanika Zhidkosti i Gaza, No. 3, 2005, pp. 144–156.Original Russian Text Copyright © 2005 by Znamenskaya, Ivanov, Kryukov, and Kuli-Zade.     

Effects of a Single-pulse Energy Deposition on Steady Shock Wave Reflection

The effects of energy deposition in the free stream on steady regular and Mach shock wave reflections are studied numerically. A short-duration laser pulse is focused upstream of the incident shock waves. It causes formation of the expanding blast wave and the residual hot-spot interacting in a complex way with the steady shock wave reflection. It was found that the laser energy addition in the free stream may force the transition from regular to Mach reflection in the dual solution domain. In contrast to previously reported numerical results, the transition from Mach to regular reflection has not been reproduced in our refined computations since the Mach reflection is restored after the flow perturbation.     

Modelling Shock/Boundary-Layer Interaction with Nonlinear Eddy-Viscosity Closures

An investigation is reported of several nonlinear eddy-viscosity models, both from a fundamental point of view and as a basis for resolving turbulence transport in transonic flows, with particular emphasis placed on shock-induced separation. The models are first analyzed by reference to a homogeneous shear flow and a plane channel flow, after which they are applied to two transonic flows with strong shock-wave/boundary-layer interaction including separation. The computational results demonstrate that nonlinear models with coefficients appropriately sensitized to strain and vorticity invariants, yield results which are superior to a standard linear low-Re k– model often claimed to give the best predictive performance among low-Re k– models which do not contain ad-hoc corrections. While this superior performance is partly associated with the functional dependence of the linear coefficient on strain and vorticity, this cannot be separated from the role of at least some nonlinear terms which interact with that coefficient, especially in complex strain fields featuring large streamline curvature and irrotational straining.