力学学报

RZSEARCH ON THE THREE-DIMENSIONAL MIXING LAYER DEVELOPING WITH TIME

A model of computation for three-dimensional mixing layers described by discrete vortex filaments is built. Based on this model, the three--dimensional mixing layers are computed numerically. The vortex structure, distribution of mean velocity, momentum thickness and mean square values of velocities at different times are given. The effects of shear rate, intensity of disturbance on flows are analysed. Some computed results are compared with related experimental ones, showing a good agreement. The results g...

1996, 28(1): 1-7. doi: 10.6052/0459-1879-1996-1-1995-296

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NUMERICAL SIMULATION FOR HYPERSONIC FLOW OF NONEQUILIBRIUM GASES AROUND THE APOLLO COMMAND MODULE

A hybrid flux splitting method is used to develop an implicit NND scheme which possesses good stability characteristics and high converging velocity. The hypersonic flows of the perfect gas and nonequilibrium gas around the Apollo Command Module are simulated with the method by solving the N-S equations. The numerical results agree with the experimental data satisfactorily. The flow structure in the leeside and wake is studied with the topological method.

1996, 28(1): 8-22. doi: 10.6052/0459-1879-1996-1-1995-297

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INFLUENCE OF SMALL CHANGES OF SUPPORT LOCATION ON VIBRATION MODE SHAPES

It is of importance to study the influence of small changes of support location on vibration mode shapes because of its necessary role in structural optimization and model correction using the generalized variational principle, the first-order purturbation equations of vibration eigenproblem are derived. In order to solve these equations two difficulties are dealt with, one is associated with the incompleteness of the unperturbed eigenfunctions, the other the truncation of the higher modes. A hybrid expansi...

1996, 28(1): 23-32. doi: 10.6052/0459-1879-1996-1-1995-298

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BISTABLE STATES OF THERMAL CONVECTIONAL FLOW IN POROUS MEDIA

The behaviour of bifurcations for thermal convectional flow in porous media, with respect to two parameters: bifurcational Rayleigh number and auxiliary aspect ratio of rectangular porous media, is studied. Attention is focused on those values of the aspect ratio at which, the two lowest critical Rayleigh numbers are near each other. We found the secondary bifurcation of the thermal convectional flow by means of the Liapunov-Schmidt reduction, and give the asymptotical expansions of the primary and secondar...

1996, 28(1): 33-39. doi: 10.6052/0459-1879-1996-1-1995-299

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BRAKING EFFECT OF A STATIC MAGNETIC FIELD ON LIQUID METAL FLOW IN A SLAB MOLD

Mathematical model on two-dimensional liquid metal flow in a casting slab mold under a static magnetic field is presented, and the effect of the static magnetic field on the liquid metal flow is studied by means of numerical analysis. Computational results show that the velocity of the strand of liquid metal flow and the strength of the reverse flow to the meniscus are reduced by the static magnetic field, and that the braking effect of the magnetic field on the strand of liquid metal flow becomes stronger ...

1996, 28(1): 40-45. doi: 10.6052/0459-1879-1996-1-1995-300

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NUMERICAL SIMULATION OF FLAME SPREADING IN AN ENCLOSED CHAMBER UNDER MICROGRMITY

A computational model of flame spread down a thermally thin solid combustible in microgravity environment has been proposed in this paper. Based on the solid fuel heat transfer and pyrolysis processes, the gas-phase combustion kinetics processes have been studied, and the mathematical treatment of interfacial coupling has been given here. The three--dimensional ullsteady processes of flame spreading in an enclosed chamber have been studied with numercial methods for the first time. The gravitional accelerat...

1996, 28(1): 46-54. doi: 10.6052/0459-1879-1996-1-1995-301

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有孔隙的耦合热弹性体动力学的一些基本原理

According to the basic idea of dual-complementarity, in a simple and unified new way proposed by the author￣[1] , some basic principles in dynamic theory of thermoelastic materials with voids can be established systematically. In this paper, an important integral relation in terms of convolutions is given, which can be considered as the generalized principle of virtual work in mechanics. Based on this relation, it is possible not only to obtain the principle of virtual work and the reciprocal theorem in dyn...

1996, 28(1): 55-65. doi: 10.6052/0459-1879-1996-1-1995-302

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THE EXPANDED ORDER SYSTEM METHOD OF COMBINED RANDOM VIBRATION ANALYSIS

A new approach is developed for combined vibration analysis of stochastic structural system with random excitations. it is based on the idea of subspace orthogonal decomposition of response of stochastic structural system. By applying orthogonal expand approach about field domain random variables in random space, a set of expanded system equations about original structural system is presented. This then supplies the possibility of solving the dynamic equations using various traditional random vibration meth...

1996, 28(1): 66-75. doi: 10.6052/0459-1879-1996-1-1995-303

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DYNAMIC STUDY OF A VIRTUALLY ROLLING DISC

On the basis of the virtual motion of a rolling disc, we present a virtual dynamical model according to the mechanical conditions of some constraints, and test the theoretical solutions by means of numerical simulation. Meanwhile we have also solved the "singular" problem when the disc falls down to the ground.

1996, 28(1): 76-82. doi: 10.6052/0459-1879-1996-1-1995-304

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EXPERIMENTAL STUDY OF THE INTERACTION BETWEEN SHOCK WAVES AND VORTEX PAIR

Experiments on two:dimensional interactions of plane moving shocks with counter- and co-rotating vortex pairs were conducted in a shock tube with a square crosssection. The unsteady procedure of the interaction between shocks and vortex pairs was studied. The distortion of shock surface, forming of secondary shock and tri-point and interaction of shocks were discussed. The results show that the shock wave is distorted very much, strength of vortex is increased and shape of vortex core is changed, during the...

1996, 28(1): 83-89. doi: 10.6052/0459-1879-1996-1-1995-305

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NUMERICAL SOLUTION OF NAVIER-STOKES EQUATIONS FOR 3-D HYPERSONIC FLOWS IN CHEMICAL NON-EQUILIBRIUM

We described a numerical method for the simulation of a complete 3-D hypersonic viscous flowfield (forbody and near wake) with ionization and in chemical nonequilibrium, The viscous and chemically reacting flow computations are based on a conservation form of the Navier-Stokes equations with the chemical source terms. The golbal colltinuity equation is replaced by the individual species conservation equations. For high temperature ionized air there are seven primary constituents which may be ordered as foll...

1996, 28(1): 90-98. doi: 10.6052/0459-1879-1996-1-1995-306

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ANALYTICAL SOLUTION OF POINT ELASTIC IMPACT BETWEEN STRVCTURES

The impactor and target are considered an integrated system of vibration, so the elastic impact problem can be dealt with as a problem of conventiollal dynamic response analysis of the system under the initial condition that a and only a part of the integrated system (impactor) is subjected to a given velocity distribution. The results of clajssical illustrative examples obtained by the suggested strategy agree with those obtained by the wave theory very well and uniform convergence can be achieved if more ...

1996, 28(1): 99-103. doi: 10.6052/0459-1879-1996-1-1995-307

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NONSTIONARY RESPONSE OF LINEAR SYSTEM UNDER NONUNIFORMLY MODULATED RANDOM EXCITION

Based on the time domain complex modal analysis, an analytical method for finding m.s. response of a time-invariant system under nonuniformly modulated random excitation is suggested. The method is illustrated by an example of a nonstationary response problem subjected to Niigata earthquake excitation. The numerical results obtained coincide very well with simulation results.

1996, 28(1): 104-108. doi: 10.6052/0459-1879-1996-1-1995-308

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NONLINEAR VIBRATION OF THE HIGH DIMENSIONAL SYSTEMS WITH PARAMETERS

This paper proproses an improved averaging method suitable for the general parameterized high dimensional systems and gives approximate formula of the nonlinear vibration in the systems under the autonomous, nonautonomous conditions respectively. By the method it investigates the nonlinear vibration in the active megnetic bearing(AMB)-rotor systems acted on by the PD controller, and by the PID controller.

1996, 28(1): 109-113. doi: 10.6052/0459-1879-1996-1-1995-309

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APPROXIMATE ANALYTICAL METHOD OF CURVILINEAR SEARCH FOR STRUCTURAL SYNTHESIS

in this paper the approximate analytical method is applied to structural optimizations for the first time. Adopting an approximate problem of the separable variables' programming to approach the primal problem of structural optimizations, we establish ordinary differential equations describing the curve of ascending the dual objective function. Based on the second order Taylor's expansion, the approximate curve of dual variables is obtained analyticallyt in which the one dimensional search is performed. Num...

1996, 28(1): 114-118. doi: 10.6052/0459-1879-1996-1-1995-310

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THE CANONICAL HAMILTONIAN REPRESENTATIONS IN SOLID MECHANICS

Some canonical Hamiltonian representations are given for a series of partial differelltial equations in solid mechanics. It includes the 2, 4 and 6 order linear symmetric partial differential equations, equations of cylindrical shells and the mixed equations of elastodynamics.

1996, 28(1): 119-125. doi: 10.6052/0459-1879-1996-1-1995-311

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1996 Vol. 28, No. 1

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