力学学报

A ZONAL VORTEX METHOD AND IMPUL SIVELY STARTED FLOW AROUND A CIRCULAR CYLINDER

In this paper, a zonal vortex method and its application to simulatingthe impulsively started flow of a circular cylinder are presented. This method treats the attached viscous flow region and the separated flow region separately- These two regions have length scales of O(Re-1/2) and O(1) respectively. The attached flow region is computed through solving boundary layer equations by finite difference method, which is fast and does not take large computer storage. Only the separated flow is computed by vortex...

1992, 24(3): 259-264. doi: 10.6052/0459-1879-1992-3-1995-737

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UPWIND FLUX DIFFERENCE SPLITTING METHOD FOR SIMULATING BOUNDARY LAYER CHARACTER

As a robust and efficient numerical method, the upwind flux differencesplitting method has been used to simulate complex viscous flow However, when the simulated supersonic viscous flow contains shear or boundary layers, the flux difference split must be conservative. If not, either an abnormally large numerical diffusion occurs within the boundary layer, or a fictitious pressure gradient is created that causes an unrealistic convection within the layer and misrepresents the boundary layer character. For th...

1992, 24(3): 265-273. doi: 10.6052/0459-1879-1992-3-1995-738

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NUMERICAL ANALYSIS OF FLOW STRUCTURE AROUND A CIRCULAR CYLINDER IN OSCILLATORY FLOW AT LOW Kc NUMBERS

This paper presents an improved algorithm which combines the advantages of Chorin's vortex method, Vortex-in-Cell method and rapid elliptic algorithm. In the present method, the numbers and positions of the discrete vortices are fixed on meshes, and the vor-ticities of the discrete vortices are adjusted with the time advances. Numerical simulations of flow structure around a circular cylinder in oscillatory flow, ranging in Kc from 1 to 5 and β from 10 to 1665, are presented in the paper. The comparison of ...

1992, 24(3): 274-282. doi: 10.6052/0459-1879-1992-3-1995-739

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NONLINEAR MODEL COUPLING OF BUBBLE OSCILLATIONS

We extend a second order theory of Longuer-Higgins on the excitation of isotropic bubble oscillations by an anisotropic mode. Our attention is focused on the resonant interaction where the energy exchange between two modes is strong enough so that both can attain comparable amplitudes. We show that the modecoupling equations resemble those known in other physics. Two special solutions are discussed. The fixed points and their stabilities are considered.

1992, 24(3): 283-291. doi: 10.6052/0459-1879-1992-3-1995-740

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WELL TEST ANALYSIS OF HIGH COMPRESSIBLE FLUIDS

In this paper, a method to compute the arbitrary changing wellborestorage coefficient and sandface flow rate from wellbore pressure data alone. The method is also applicable for gas well test analysis, and makes a contribution to the study of multiphase flow well test analysis. Example analysis results show that the method is practical.

1992, 24(3): 292-302. doi: 10.6052/0459-1879-1992-3-1995-741

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AN INFLUENCE-MATRIX METHOD FOR HIGH PRESSURE COMPRESSOR BLADE DESIGNS

An implicit method for sub-critical compressor blade design was developed based on the surface vortex distribution model. The method utilizes implicit residual correction to construct an influence matrix which relates the variation of pressure coefficient distribution on blade surface with that of blade coordinates, and the problem is solved with a two-dimensional finite element potential flow field solver. The main purpose of developing this method is to provide a high accuracy numerical correction to a bl...

1992, 24(3): 303-311. doi: 10.6052/0459-1879-1992-3-1995-742

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TWO-DIMENSIONAL TWO-PHASE FLOW NUMERICAL SIMULATION OF IGNITION AND FLAMESPREADING PROCESS IN DENSE PARTICLES BED

An unsteady two-dimensional two-phase axial-symmetrical flow modelfor dense particles with chemical reaction and an unsteady one-dimensional two-phase flow model for igniter are established to analyze the interior ballistics of gun. In the model, the coupling effect of the igniter on the main charge bed is considered. The two-step MacCor-mack difference method is employed to compute the flame spreading process and the variation of physical parameters along the axial and radial directions. A part of the resu...

1992, 24(3): 312-319. doi: 10.6052/0459-1879-1992-3-1995-743

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THE FINITE ELEMENT ANALYSIS OF PULSATILE FLOW PATTERNS ASSOCIATED WITH AN ARTERIAL STENOSIS

Pulsatile flow patterns in rigid arterial models with stenosis (area constrictions) of 50% and 80% have been studied using the Finite Element Methods. Flow patterns of the constricted region have been investigated for a simulated physiological condition with an average Reynolds number of 561.8 and a Womersley number of 7.16. Velocity waveforms, axial pressure drop and wall shear stress distributions have been computed for each model and presented at several time steps. Flow separation zone near the stenosis...

1992, 24(3): 320-328. doi: 10.6052/0459-1879-1992-3-1995-744

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NONLOCAL THEORY OF BRITTLE FRACTURE

In this paper, a nonlocal theory of fracture for brittle materials has beenproposed. It contains the nonlocal elastic stress fields of mode-I, II, III Griffith cracks, the asymptotic forms of the stress fields at the neighborhood of the crack tips, and the maximum tensile stress criterion of brittle fracture. As an application of the theory, the fracture criteria of cracks of mode-I, II, III and mixed mode I-II, I-III are given in detail and compared with some experimental data and the theoretical results o...

1992, 24(3): 329-338. doi: 10.6052/0459-1879-1992-3-1995-745

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STRUCTURE INTEGRITY ASSESSMENT BASED ON NON-J-CONTROLLED GROWTH

In the present paper, a j1-integral is investigated for a material characterized by an incremental plasticity model under the non-J-conirolled crack growth situation. Based on the Gao-Hwang solution of the near-tip fieid and the concept of ji-integral, an analytical relation linking CTOA and j1 is established. A detailed numerical simulation and the experimental program for CT specimen with the large size are performed A structure integrity assessment approach based on elastic-plastic fracture under the non...

1992, 24(3): 339-349. doi: 10.6052/0459-1879-1992-3-1995-746

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TORSION OF COMPOSITE CYLINDER WITH CRACK AND INCLUSION

According to the theory of Saint-Venant's torsion, a fundamental solutionof a linear inclusion model proposed in this paper is obtained, which will be useful to the torsion problem. Using the obtained solution together with the Muskhelishvili's potential solution of single layer and the fundamental solution of a single crack, the torsion problem of a composite-cylinder with crack and inclusion is studied. Finally, the problem is reduced to solving a set of mixed-type integral equations and at the same time ...

1992, 24(3): 350-360. doi: 10.6052/0459-1879-1992-3-1995-747

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DETERMINATION OF DYNAMIC RESPONSE OF STEEL SHELL USING PHOTO-MECHANICS AND FINITE ELEMENTMETHODS

本文提出了壳体在冲击载荷作用下三维位移分布的光力学方法的实验解和有限元数值解。采用一种新型的电磁脉冲加载装置,实现了对试件施加重复性很好的冲击载荷,利用测得的力一时间关系曲线作为外力边界条件,用逐步积分法对壳体在冲击载荷下的动态响应作了分析。光力学方法的实验解和有限元数值解吻合较好。

1992, 24(3): 361-367. doi: 10.6052/0459-1879-1992-3-1995-748

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THE SPINNING STABILITY OF A HEAVY RIGID BODY WITH LIQUID-FILLED CAVITIES

The spinning stability of a heavy rigid body with an arbitrary number ofliquid-filled cavities is discussed in present paper. The average vortex is used as a discretized variable of the liquid. A stability criterion in analytic form is derived and used to discuss the spinning projectile containing liquid charge. The effectiveness of the diaphragm on increasing the spinning stability is evaluated.

1992, 24(3): 368-371. doi: 10.6052/0459-1879-1992-3-1995-749

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MOLECULAR DYNAMIC SIMULATION FOR INTERFACE PHENOMENA AND SURFACE TENSION OF LIQUID

In this paper, the interface phenomenon including solidliquid, liquid-gas and gas-solid of krypton is studied by means of the molecular dynamic computer simulation method. It is shown that the zero radial distribution of liquid is arranged in order, atoms at the side of the liquid near the interface of solid-liquid have similar-crystal structure, and at the surface of solid there is an absorptive layer with gases. The result of surface tension obtained is in agreement with the experimental data. This fact s...

1992, 24(3): 372-375. doi: 10.6052/0459-1879-1992-3-1995-750

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SOLUTION OF STRESS INTENSITY FACTORS BY WEIGHT FUNCTION FOR SMALL CORNER CRACKS IN PLATES

The three-dimensional weight function method developed in [2,3] is usedto determine stress intensity factors for small corner cracks in plates subjected to remote tension and bending. The geometry parameters considered are c/b=0.1;a/c = 0.2,0.4,0.6, l,2;a/t = 0.01,0.05,0.1 and 0.2, which cover the range of small surface crack problems commonly encountered in fatigue and fracture studies and applications. The results are compared with the finite element solutions in [1] . Very good agreement is observed. The...

1992, 24(3): 376-380. doi: 10.6052/0459-1879-1992-3-1995-751

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SOLUTION TO ASYMMETRIC BENDING OF CIRCULAR PLATES UNDER SINGLE LOAD BY USING POINT-SOURCEFUNCTION

In the present paper, the point-load normal to the middle surface,located at a arbitrary place on a plate, is taken as a point source and expressed as the 6-fun-ction. In the paper is derived the non-homogeneous solution in closed form and homogeneous solution in series form of the differential equation for the bending of the circular plate under single load, thus obtaining the uniform displacement expression valid for the whole plate.

1992, 24(3): 381-387. doi: 10.6052/0459-1879-1992-3-1995-752

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1992 Vol. 24, No. 3

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