力学学报

MECHANISM OF BIFURCAIION FOR THERMAL CONVECTION IN FLOW OF POROUS MEDIA AND NUMERICAL SIMULATION

The mechanism of bifurcations for the thermal convection flow of porousmedia is studied by analytical method.It is pointed out that the Rayleigh number Ra in thenonlinear flow equations is an important parameter to determine the fiow characteristics。If Ra is less than the critical Rayleigh number Ra_c,the fluid in the porous medium is instatic state,which is stable.If Ra>Ra_c,the solution of the flow equations in the porousmedia will bifurcate.There are a lot of criticaI Rayleigh numbers,and we can write th...

1994, 26(2): 129-138. doi: 10.6052/0459-1879-1994-2-1995-530

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APPLICATIONS OF A SECOND-ORDER UPWIND TVD SCHEME TO NONEQUILIBRIUM HYPERSONIC FLOWS AROUND BLUNT-BODY

An explicit second-order upwind TVD scheme by H.C.Yee is first suc-cessfully extended to solve the viscous,diffussive,nonequilibrium,ionizing,hypersonic flowfields over a hemi-sphere.The governing gas-dynamic and species-continuity equations forlaminar flow are presented.The gas-dynamics/species continuity equations fully couplingprocedure is described in detail.Before this only the firstorder scheme and loosely coupledmethod was successfully used in this research field.The gais model for chemically relaxin...

1994, 26(2): 139-148. doi: 10.6052/0459-1879-1994-2-1995-531

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A FLUID DYNAMICS MODEL FOR THE LOW SPEED TRAFFIC SYSTEMS

This paper presents a new mathematical model for traffic flow.The modelis more general than any one,which is widely used in traffic engineering,especially forthe city traffic cases in our country,in which vehicles run at low speed and together withbicvcles,We discussed both differential and difference formulations of the model.the initialand boundary conditions,model parameter identification method and the stabilities of thenumerical solutions.Several practical and difficult examples showed its good numeric...

1994, 26(2): 149-157. doi: 10.6052/0459-1879-1994-2-1995-532

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EFFECTS OF SURFACE-TENSION,VISCOSITY AND DRIVING ON THE NON -PROPAGATING SOLITARY SURFACE WAVES

The effects of the surfacetension,viscosity and driving on the non-propagating solitary surface waves are investigated theoretically.It is shown that the heightof the soliton increases while the width decreases under the surface tension. The equal-wave-response-curves are made theoretically,which are compared with the experiment.

1994, 26(2): 158-164. doi: 10.6052/0459-1879-1994-2-1995-533

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NUMERICAL SIMULATION OF NArURAL RIVER FLOW BY THE PRECONDITIONING METHOD

A preconditioning method is presented for solving 2-Dturbulent floWmodel.By using this method,numerical simulations of driven square cavity flow and naturalriver flow are performed.The numerical results show that the method has good stabilityand fast convergence.

1994, 26(2): 165-175. doi: 10.6052/0459-1879-1994-2-1995-534

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INVESTIGATION TO THE BUCKLING AND POSTBUCKLING BEHAVIOUR OF SHEAR-FLEXIBLE PLAIES OF COMPOSITE CON5TRUCTION

The generalized Karman equations governing large defiection of shear-flexible plates of composite construction are developed and discussed. Progress hajs thusbeen made in extension of soine theoretical modelings to include more complicated materialproperties based upon the shear deformable plate theory of Reissner type.An asymp-totic expansion is constructed by the perturbation technique proposed for the postbucklingbehaviour of simply supported rectangular plates of composite construction.This approxi-mati...

1994, 26(2): 176-185. doi: 10.6052/0459-1879-1994-2-1995-535

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DISPLACEMENT METHOD OF ELASTICITY PROBLEMS IN SPHERICALLY ISOTROPIC MEDIA

Three displacement functions w,Gand ψare introduced in this paper tosimplify motion equations of elasticity problenis in spherically isotropic media to an indepen-dent partial differential equation concerning one displacement function ψand simultaneous equations concerning two other displacement functions w and G.For static elasticity,thesimultaneous equations can be further simplified through another function F,which is gov-erned by a four-order partial differential equation,In free vibration problems of s...

1994, 26(2): 186-197. doi: 10.6052/0459-1879-1994-2-1995-536

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NONLINEAR THERMAL INSTABILITY IN AN IDEALIZED DYNAMICAL SYSTEM OF FISOPM PLASMAS

The nonlinear thermal instabilitv in an idealizeddvnamical svstem ofdeuterium-tritium fusion plasma is discussed in the present paper.There are mass andenergy exchanges between the system and its surroundings.The evolution equations ofzero-dimension approximation are adopted.Firstly,the nonlinear thermal stability criteriaare obtained for the autonomous svstem and five different confinement laws.Then,thenonlinear evolution equations for the disturbances of unstable solution are solveJd for theconstant conf...

1994, 26(2): 198-206. doi: 10.6052/0459-1879-1994-2-1995-537

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MIE-GRUNEISEN EQUATION OF STATE OF EPOXY-SiO_2MICROBALLOONS COMPOSITE MAIERIALS

Hugoniots of epoxy-SiO_2 microballoons composite materials with three different densities are presented in this paper.In view of the fact that the results obtained by application of Mie-Gruneisen equation of state with Hugoniot reference to the materials mentioned above are in agreement with that of uqing P-αmodel,Mie-Gruneisen EOS can directly apply to epoxy-SiO_2 microballoons composite materials in the range of experimental pressure

1994, 26(2): 207-213. doi: 10.6052/0459-1879-1994-2-1995-538

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THE STRICT COMPLEMENTARY EXTREMUM-SADDLE POINT THEOREM IN NONLINEAR PROBLEMS

The strict complementary extremum-saddle point theorem for two prob-lems of new nonlinear form are obtained,and the generality and effectiveness for secondvariation-convex analysis method suggested are demonstrated in this paper.The first prob-lem is rotating tubro impeller,and by introducing the periodic free surface variable we obtainall complementary variational principles.The second problem is non K-L shell with rotaryvaridfble having specific nonlinear geometrical property,and we establish the comple...

1994, 26(2): 214-221. doi: 10.6052/0459-1879-1994-2-1995-539

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PARTICULAR SOLUTIONS METHOD TO ADJUST SINGULARITY FOR THE CALCULATION OF STRESS AND DISPLACEMENT AT ARBITRARY POINT

In this paper,super singularity boundary iutegral is transformed into Cauchy principal value integral in boundary stress integral equation,The existance of theprincipal value integral is demenstrated and the explicit formula of its scale extra term in thesubstitution of variables is given out.Then the main submatrix of supersingularity and thematrix of stress singularity parameters are expressed as a linear combination of non-diagonalsubmatrices in the same row by using rigidbody movement method and unit st...

1994, 26(2): 222-232. doi: 10.6052/0459-1879-1994-2-1995-540

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NUMERICAL STUDY OF VISCOUS FLOW PAST A ROTATING CIRCULAR CYLINDER IN A UNIFORM STREAM

A viscous flow past a rotating oscillating circular cylinder in a uniformstream is numerically investigated using the Navier-Stokes equations.The emphasis of thisstudy is on the influence of frequency,amplitude and Reynolds number upon the flowfieldstructures and their evolution.A parameter map is designed in the frequency-amplitudeplane,indicating the classification of vortex structures in the near wake.

1994, 26(2): 233-238. doi: 10.6052/0459-1879-1994-2-1995-541

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TO THE COMPUTATION OF NONLINEAR CONTROL SYSTEMS APPLlCATION OF THE MULTI-LEVEL SUBSTRUCTURAL METHOD

The multi-level substructural method is one of the most extensively usedmethods in the program system of computational structural mechanics.Bajsed on similaritiesbetween computational structure mechanics and optimal contro1,the problem in nonIinearcontrol system is computed by using the same method,and the corresponding program isgiven.The work in this paper further shows the close similarity betWeen computationalstructure mechanics and optimaJ control.

1994, 26(2): 239-246. doi: 10.6052/0459-1879-1994-2-1995-542

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SOME KINEMATIC RELATIONS IN FINITE DEFORMATIONS

The present paper provMes some further kinematic relations in the theoryof finite deformations for the case when the current configurations are simultaneously taken as the reference configuration.

1994, 26(2): 247-250. doi: 10.6052/0459-1879-1994-2-1995-543

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DYNAMIC RESPONSE OF SATURATED SANDS TO EARTHQUAKE

The dynamic response of sat urated sand deposits to earthquake loading isinvestigated through an“Engi neering Approach”.Considering the mechanism of dynamicresp onse of s at urated sands to cyclic loading,a simplified model is constructed,and theequation for describing the response and the diffusinn equatfon for describing generationand dissipation of porewater pressure are given.These equations are solived numerically by the Newmark’s method and finit edifferences method,The dynamic response of a satnrat...

1994, 26(2): 251-256. doi: 10.6052/0459-1879-1994-2-1995-544

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1994 Vol. 26, No. 2

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