力学学报

NUMERICAL STUDY ON THE INTERACTION BETWEEN A SHOCK WAVE AND A VORTEX

A numerical study of two-dimensional shock vortex interaction is discussed in this paper. A high resolution symmetric TVD scheme is used to capture the shock wave for solving the Euler equations in conservation form. In the present study, some complicated flow phenomena, such as shock deformation, shock branching, and the formation of secondary shock and triple points etc., are effectively simulated. The computed results are in good agreement with experimental work.

1993, 25(3): 257-263. doi: 10.6052/0459-1879-1993-3-1995-641

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NUMERICAL STUDY ON THE MECHANISM FOR THREE-DIMENSIONAL EVOLUTION OF VORTEX AND THE STRUCTURAL FEATURES IN THE WAKE BEHIND A CIRCULAR CYLINDER

In this paper, the mechanism and dynamic process for three-dimensional evolution of the Karman vortices and the vortex filaments in the braid regions, and the structural features in the wake behind a ciccular cylinder at moderate Reynolds number (≈103) have been studied numerically. The vortex filament in the wake field are tracked by the inviscid vortex dynamics and the localized-induction approximation (LIA) method. The time-averaged velocity field of the wake and Karman vortex street flow field are consi...

1993, 25(3): 264-275. doi: 10.6052/0459-1879-1993-3-1995-642

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SOLUTAL BOUNDARY CONDITIONS OF MARANGONI CONVECTION IN FLOATING ZONE

There may exist two kinds of solutal boundary conditions, that is, given value of concentration or given flux of concentration at the melting interface for thermal and solutal capillary convection in the floating zone. The solutions of the two kinds of problems are obviously different. In the present paper, the physical processes and their influence associated with these problems of two kinds of boundary conditions have been analyzed.

1993, 25(3): 276-282. doi: 10.6052/0459-1879-1993-3-1995-643

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GENERALIZED STROH FORMALISM FOR ANISOTROPIC ELASTICITY FOR GENERAL BOUNDARY CONDITIONS

The Stroh formalism is most elegant when the boundary conditions are simple, namely, they are prescribed in terms of traction or displacement. For mixed boundary conditions such as there for a slippery boundary, the concise matrix expressions of the Stroh formalism are destroyed. We present a generalized Stroh formalism which is applicable to a class of general boundary conditions. The general boundary conditions include the simple and slippery boundary conditions as special cases. For Green's functions for...

1993, 25(3): 283-301. doi: 10.6052/0459-1879-1993-3-1995-644

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STUDY ON ELASTOHYDRODYNAMIC LUBRICATION PROBLEMS WITH REAL ROUGH SURFACES IN LINE AND POINT CONTACTS

The multigrid numerical method is used to study elastohydrodynamic lubrication (EHL) problems with real rough surfaces in line and point contacts. After random rough surface samples are given, problems under different loads and roughnesses have been calculated. The results show that because of the function of the velocity item in Reynolds equation, the pressures induced by the corresponding roughnesses make the rough surface flattened in both line and point contacts, especially under heavy loads. The variat...

1993, 25(3): 302-308. doi: 10.6052/0459-1879-1993-3-1995-645

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ANALYTICAL MODELING OF SPHERE SYMMETRY DISPERSION IN MICRO-AGGREGATES POROUS MEDIA

This paper studies sphere symmetry dispersion problem. In the mathematical model the micro-aggregates of porous media are considered. The micro-aggregate plays a role of general adsorption, and in transportation process of solute it results in retardation of concentration wave. In this paper five kinds of micro-aggregates are concerned, i.e. local equilibrium sorption model, first-order rate-limited sorption model, parallel layer diffusion model, cylindrical diffusion model and spherical diffusion model. Th...

1993, 25(3): 309-316. doi: 10.6052/0459-1879-1993-3-1995-646

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A THICK-THIN TRIANGULAR PLATE ELEMENT

A new thick-thin triangular plate element is presented. The element emanating from the Hellinger-Reissner variational principle has independent interpolation for slope, displacement, shear strain and bending strain. It is shown that it does not suffer from any defect common to other Mindlin plate elements. Several examples are presented to illustrate the behaviour of this new element. It is pointed out that this element is also considered as the element using the reduced integration for shear energy (i.e. 1...

1993, 25(3): 317-326. doi: 10.6052/0459-1879-1993-3-1995-647

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A SINGLE DIRECTION RECURSIVE CONSTRUCTION METHOD FOR DYNAMIC EQUATIONS OF FLEXIBLE MANAPULATORS

In this paper, a new recursive technique for construction of dynamic equations of flexible manapulators is suggested based on the Jourdain's principle. The structure of the system is described through regular labelling method; The joint relative coordinates and modal coordinates are used to describe the large displacements between contiguous bodies and small deformations of bodies. At first, the recursive kinematic relations are derived, and in every step of recursion, contributions of every body to the gen...

1993, 25(3): 327-333. doi: 10.6052/0459-1879-1993-3-1995-648

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ADAPTIVE OPEN BOUNDARY CONDITION FOR DISPERSIVE WAVES

The adaptive Open Boundary Condition (OBC) designed by Chen and the author is extended to cover the cases of dispersive waves. The design was based on a kind of dispersive solutions and an "Equivalent Wave Velocity" was introduced. The latter was derived from dispersive relation ω= ω(k) by Taylor expansion locally. A couple of different kinds of OBC are obtained, which can be used to the numerical computation of dispersive waves, especially, dispersive water waves. Two examples which have exact solutions ar...

1993, 25(3): 334-342. doi: 10.6052/0459-1879-1993-3-1995-649

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EXPERIMENTAL STUDY OF PASSIVE SCALAR DIFFUSION IN GRID TURBULENCE WITH CONTRACTION

We use a contraction in the grid turbulence to get non-isotropic turbulence. We have studied the thermal mixing layer and thermal wake in the grid turbulence with a contraction. The experiment results show that the mixing layer and wake were compressed in the contraction section, then they were expanding continuously. Their profiles of the T, and have similarity in the experimental region.

1993, 25(3): 343-347. doi: 10.6052/0459-1879-1993-3-1995-650

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THE KINETIC MODEL FOR COLLISIONAL STRESSES IN RAPID GRANULAR FLOWS

Particle collisions are the main mechanism of the momentum transfer, the energy transfer and the energy dissipation for rapid granular flows. Therefore, attention is paid to the collisional stresses in the study of rapid granular flows. Based on an inelastic collisional model of uniform, smooth and spheric particles, the collisional stress tensor, the collisional energy flux and the rate of energy dissipation, which are expressed in integral forms, are all obtained in this paper by analogizing the method in...

1993, 25(3): 348-355. doi: 10.6052/0459-1879-1993-3-1995-651

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A NUMERICAL STUDY OF VORTEX SHEDDING FROM A CIRCULAR CYLINDER IN PLANE MIXING LAYERS

Numerical simulations are presented for flows about a circular cylinder which is spanwise placed at the center of plane mixing layers. A temporally and spatially third-order finite differencing scheme is used to solve the 2-D incompressible Navier-Stokes and continuity equations. The Reynolds number for computation is fixed at Re=1000. The effects of the velocity ratio Ra and the momentum thickness θ of the mixing layer on flow structures are studied by changing Ra from 0.0 to 1.0 and θ from 0.2 to 2.0.

1993, 25(3): 356-361. doi: 10.6052/0459-1879-1993-3-1995-652

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THE MONMENT EQUATION METHOD FOR MULTI DEGREE OF FREEDOM SYSTEM WITH STRONGLY NONLINEAR COUPLING AND PARAMETRIC EXCITATION

This paper applied a non-Gaussian moment equation closure method to compute random responses of a two-degree-of-system with strongly nonlinear coupling under parametric excitation. After removing the coupling of interia in the motion equations of the system by using successive elimination technique, the 69 moment equations have been derived and integrated by RK4 combined with central cumulate truncation scheme. A comparison of the results by different numerical methods in also given in this paper.

1993, 25(3): 362-368. doi: 10.6052/0459-1879-1993-3-1995-653

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EXPERIMENTAL INVESTIGATION ON LIMIT PRESSURE OF ORTHOGONALLY INTERSECTING CYLINDRICAL SHELLS WITH DIFFERENT DIAMETERS

内压下异径正交圆柱壳的极限承载能力受到普遍关注。本实验完成了ρ≈0.3,0.5,0.7,0.8四种开孔率的8个钢制模型实验研究。测量压力-应变曲线,按零曲率准则和双切线准则确定实验极限压力。结果和极限分析有限元上限格式解相当吻合。文中讨论了塑性流动大变形情况的应变测量技术问题。

1993, 25(3): 369-374. doi: 10.6052/0459-1879-1993-3-1995-654

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基于变形动力学模型的黏弹性材料本构关系

An evolution equation of internal variables which are related to viscoelastic deformation is derived from the theory of molecular motion. Based on this equation and irreversible thermodynamics, a linear viscoelastic constitutive law is found.

1993, 25(3): 375-379. doi: 10.6052/0459-1879-1993-3-1995-655

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利用对称性寻找浑沌运动

In this paper, we study a class of nonlinear oscillators with parametric and forcing excitation. On the basis of theoretical analysis and digital computer simulation, we first develop a new method of seeking the chaotic solution by symmetry. As this method is able to locate the position of the unknown chaotic point from the position of the known chaotic point on the controlled parametric plane, time of digital computer simulation is greatly reduced. It is shown from an example of this paper that if we find ...

1993, 25(3): 380-384. doi: 10.6052/0459-1879-1993-3-1995-656

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1993 Vol. 25, No. 3

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