The formation of a secondary shock wave behind a shock wave diffracting at a convex corner

This paper deals with the formation of a secondary shock wave behind the shock wave diffracting at a two-dimensional convex corner for incident shock Mach numbers ranging from 1.03 to 1.74 in air. Experiments were carried out using a 60 mm 150 mm shock tube equipped with holographic interferometry. The threshold incident shock wave Mach number () at which a secondary shock wave appeared was found to be = 1.32 at an 81° corner and = 1.33 at a 120° corner. These secondary shock waves are formed due to the existence of a locally supersonic flow behind the diffracting shock wave. Behind the diffracting shock wave, the subsonic flow is accelerated and eventually becomes locally supersonic. A simple unsteady flow analysis revealed that for gases with specific heats ratio the threshold shock wave Mach number was = 1.346. When the value of is less than this, the vortex is formed at the corner without any discontinuous waves accompanying above the slip line. The viscosity was found to be less effective on the threshold of the secondary shock wave, although it attenuated the pressure jump at the secondary shock wave. This is well understood by the consideration of the effect of the wall friction in one-dimensional duct flows. In order to interpret the experimental results a numerical simulation using a shock adaptive unstructured grid Eulerian solver was also carried out. Received 1 May 1996 / Accepted 12 September 1996     

Singular solution of boundary-layer equations on a moving surface

We consider a plane steady flow of incompressible fluid in the boundary layer which develops on a surface moving downstream. We obtain a singular solution of Prandtl's equations, continuously extendable through the simultaneous vanishing point of the friction and the longitudinal velocity vector component. Such a solution is realized, in particular, in a flow past a rotating circular cylinder.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 2, pp. 43–52, March–April, 1987.The author thanks A. I. Ruban for his great interest in the work and his useful remarks.     

Parameter formation behind the reflected wave in a shock tube with a nozzle

The reflection of a shock wave from the inlet of a nozzle of very simple geometry is analyzed on the basis of calculations carried out in the two-dimensional formulation. The nozzle throat is a sharp-edged slit in the end face of the tube leading to an expanding duct with straight generators. In this formulation the results of the investigation are quite general, since they depend on a minimum number of the determining parameters varied in the calculations.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 4, pp. 153–159, July–August, 1987.The authors wish to thank G. N. Nikolaev and I. M. Naboko for useful discussion of their results.     

Numerical solution of moving boundary problem in a finite domain

The temperature distribution in two regions and the location of moving interface during freezing in a finite domain is studied numerically. The differential equations governing the process of heat transfer in two regions are converted to initial value problem of vector matrix form. The solution of this initial value problem is utilized iteratively in the interface heat flux equation to determine interface location as well as the temperature distribution in two regions. The whole analysis is presented in a nondimensional form and the results thus obtained are discussed in detail. Received on 4 March 1998     

Asymptotic solution to the problem of drag of a fluid by a moving plate

An analogy is established between the formulations of the problem of the drag of a fluid by a moving plate [1–3] and the problem of propagation of a stationary flame [4, 5]. The theory of singular perturbations is used to a find a two-term asymptotic expression for the film thickness h₀. The expansion parameter is the Bond number Bo 1. The limited applicability of the well-known formula of [1, 2] is estimated quantitatively. Such an estimate has been obtained earlier experimentally [3]. The approach used in the present paper should also be fruitful for the solution of other problems in capillary hydrodynamics.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 6, pp. 52–56, November–December, 1980.     

Numerical solution of the problem of wave diffraction by a wedge

The systematic development of the theory of shock reflection from a solid wall started in [1]. Regular reflection and a three-shock configuration originating in Mach reflection were considered there under the assumption of homogeneity of the domains between the discontinuities and, therefore, of rectilinearity of these latter. The difficulties of the theoretical study include the essential nonlinearity of the process as well as the instability of the tangential discontinuity originating during Mach reflection. Analytic solutions of the problem in a linear formulation are known for a small wedge angle or a weak wave (see [2–4], for example). The solution in a nonlinear formulation has been carried out numerically in [5, 6] for arbitrary wedge angles and wave intensities. Since the wave was nonstationary, the internal flow configuration is difficult to clarify by means of the constant pressure and density curves presented. A formulation of the problem for the complete system of gasdynamics equations in self-similar variables is given in [7] and a method of solution is proposed but no results are presented. Difficulties with the instability of the contact discontinuity are noted. The problem formulation in this paper is analogous to that proposed in [7]. However, a method of straight-through computation without extraction of the compression shocks in the flow field is selected to compute the discontinuous flows. The shocks and contact discontinuities in such a case are domains with abrupt changes in the gasdynamics parameters. The computations were carried out for a broad range of interaction angles and shock intensities. The results obtained are in good agreement with the analytical solutions and experimental results. Information about the additional rise in reflection pressure after the Mach foot has been obtained during the solution.     

The flow structure of dilute gas-particle suspensions behind a shock wave moving along a flat surface

The asymptotic and numerical investigations of shock-induced boundary layers in gas-particle mixtures are presented.The Saffman lift force acting on a particle in a shear flow istaken into account.It is shown that particle migration across the boundary layer leads tointersections of particle trajectories.The corresponding modification of dusty gas model isproposed in this paper.The equations of two-phase sidewall boundary layer behind a shock wave moving at aconstant speed are obtained by using the method of matched asymptotic expansions.Themethod of the calculation of particle phase parameters in Lagrangian coordinates isdescribed in detail.Some numerical results for the case of small particle concentration aregiven.     

Wake formation when shock wave is shed from the edge of a plate

The formation of a laminar wake in the flow behind a shock wave when the latter is shed from the trailing edge of a semi-infinite plate is investigated in this paper. It is shown that the flow on the plate and in the wake turns out to be self-similar, dependent on two dimensionless combinations of variables, and the flow on the plate, including the trailing edge, remains steady in a coordinate system coupled to the shock wave (the fact of the flow self-similarity in the wake was first noted in [1]). An analytic solution of the problem of the wake in the neighborhood of the trailing edge is obtained, from which it follows that, in contrast to [2], there is no line of singularities in the nonstationary boundary-layer equations in the flow domain. This fact is also verified by the analysis of the flow in the neighborhood of a line of tagged particles leaving the trailing edge simultaneously with the shock wave. Hence the problem under consideration is solved by the traditional numerical methods using conditions in the initial section (which is taken to be the section in the neighborhood of the trailing edge), on the wake axis, and at an infinite distance away. Approximate formulas are obtained for the longitudinal velocity profiles in the whole range of shock-wave intensities.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 4, pp. 59–66, July–August, 1978.     

Numerical solution of the problem of an ice sheet under a moving load

A method for analyzing the bending of an ice sheet subjected to a moving load is proposed. The problem is solved in a dynamic formulation. The algorithm of solution is based on the finiteelement method and the finite-difference method. The method proposed allows one to determine the stress-strain state of an ice sheet for any law of motion of a load over ice. Two versions of initial conditions are considered. Examples of calculations are given. Komsomol’sk-on-Amur State Technical University, Komsomol’sk-on-Amur 681013. Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 40, No. 4, pp. 243–248, July–August, 1999.     

Ideal gas flow behind a finite-amplitude shock wave

The equations of one-dimensional (with a plane of symmetry) adiabatic motion of an ideal gas are transformed to a form convenient for studying flows between a moving piston and a shock wave of variable intensity. The solution is found for the equations of a motion containing a shock wave which propagates through a quiescent gas with variable initial density and constant pressure. This solution contains four arbitrary constants and, in a particular case, gives an example of adiabatic shockless compression by a piston of a gas initially at rest.     

Construction of the solution of the linear problem of shock wave stability

Within the framework of the linear theory a solution is obtained in explicit form for a solitary plane shock using Fourier and Laplace transforms and assuming only the finiteness of the small perturbations. In the case of three-dimensional flows the small deformations of the shock wave surface are represented in the form of integral functionals, with Poisson kernels, of the initial perturbations of both the shape of the shock wave and the parameters of the flow field beyond it. The solution for plane flows is then constructed by the method of descent. From the equations obtained it follows that: for the region of stability and the intermediate region the solution has a finite domain of dependence on the initial perturbations; despite the fact that the structure of the domain of dependence in these regions is different, at large times the damping of the perturbations proceeds in accordance with a single law at a rate that depends on the dimensionality of the shock front.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. A, pp. 130–138, July–August, 1988.     

Numerical solution to the buckling problem for a sandwich plate under uniaxial compression

A thin rectangular sandwich plate with isotropic linear elastic layers is considered. The plate is in a plane-strain state under uniaxial compression. An exact statement of the buckling problem is given. Its approximate solution is found by the finite-difference method. The concept of base scheme is used to formulate discrete problems in explicit and compact form. As an example, the critical parameters of the plate are calculated using a computation optimization procedure. Its efficiency is demonstrated __________ Translated from Prikladnaya Mekhanika, Vol. 42, No. 9, pp. 98–105, September 2006.     

Numerical solution of the problem of the effect of a shock pulse on an ice sheet

A mathematical formulation of the problem is given. A method is proposed to determine the initial velocities of points of an ice sheet subjected to a point shock pulse. An example of calculation of ice-sheet deflections is considered. __________ Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 49, No. 2, pp. 152–159, March–April, 2008.