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NUMERICAL CALCULATION OF TUBULENT SEPARATED FLOWS IN 180 DEG DUCT WITH RNG K ε TUBULENCE MODEL

A two equation turbulence mode of K ε type was recently derived by Yakhot and Orszag on Renormalization Group (RNG) methods.It was applied to solve the turbulent separated flows in a 180 deg duct.The scheme has been developed for a generalized coordinate system and in based on a control volume approach with a staggered grid arragement.The physical covariant velicity components are selected as the dependent variable in the momentum equations.The detail numerical results were given and compared with th...

1996, 28(3): 257-263. doi: 10.6052/0459-1879-1996-3-1995-329

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SOLVING TWO DIMENSIONAL INCOMPRESSIBLE VISCOUS COMPLEX FLOW WITH HIGH ORDER COMPACT SCHEME

The paper presents a high accurate method for two dimensional incompressible viscous complex flow. Governing equations are used to adopt primitive variables and the formulation of Poisson equation for pressure. The Navier Stokes equation is solved by fourth order accurate compact scheme making as block tridiagonal linear equations for space and the ADI method for time advance in the general non staggered grid system, and the SOR method solves Poisson equation of pressure. A domain decomposition method is...

1996, 28(3): 264-269. doi: 10.6052/0459-1879-1996-3-1995-330

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NONLINEAR OSCILLATION OF A 3D GAS BUBBLE MOVING IN A SLOWLY VARYING FLOW

Chuanjing Lu

Cavitation phenomena and underwater noise mechanism are closely related to bubble dynamics. Under the assumption of inviscid potential flow, a multiple parameter perturbation analysis is carried out for the nonlinear volume mode oscillation of a 3D gas bubble moving in a slowly varying flow in the paper. The perturbation equations are deduced by expanding the nonlinear boundary conditions to be satisfied on the slowly varying shape. The evolution equation and some analyticalsolutions of the first order osc...

1996, 28(3): 270-280. doi: 10.6052/0459-1879-1996-3-1995-331

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APPLICATION OF CONSERVATION LAW OF WAVE ACTION FLUX TO WAVE CURRENT INTERACTION

, Jiachun Li

When surface ocean waves are intercepted by currents,the interaction between them takes place and finally a steady wave current coexisting flow is formed.Based on the principle of conservation of wave action flux,a fifth order theory to solve the problem of interaction between Stokes waves and exponential profile currents is proposed in this paper. The variation of wave parameters during the interaction process is at first studied, and the corresponding flow fields are obtained,then the results are compar...

1996, 28(3): 281-290. doi: 10.6052/0459-1879-1996-3-1995-332

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THE BEHAVIOR AND CRITERION OF TURBULENCE SUPPRESSION EFFECT OF THE PARTICLES IN A HORIZONTAL LIQUID SOLID FLOW

By using two phase measuring technique of LDV, the suppression effects of sub millimeter particles to the water turbulence in mainstream zone of a horizontal pipe flow have been experimentally studied. This includes the investigation of the dependences of turbulence reduction on the parameters of particle size, flow development length, water flow Reynolds number, etc. According to the basic conditions that the appearance of vortex shedding phenomenon should be excluded and that the particles should respon...

1996, 28(3): 291-297. doi: 10.6052/0459-1879-1996-3-1995-333

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CLASSIFICATION OF NONLINEAR NORMAL MODES AND THEIR NEW CONSTRUCTIVE METHOD

The definition of the nonlinear normal modes is given by introducing the undivided even dimensional invariant manifold, and a new kind of normal modes (i.e. coupled nonlinear mode) are proposed which may classify all the normal modes expected in physical systems. This idea of classification may form a new base of constructing the nonlinear normal mode theory. Modal oscillators obtained by the method presented here are of Normal Form type,which are simplest in expression and can represent the main dynamical...

1996, 28(3): 298-307. doi: 10.6052/0459-1879-1996-3-1995-334

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TRANSIENT SOLUTIONS OF AXISYMMETRIC DYNAMIC PROBLEM FOR INHOMOGENEOUS TWO PHASE MEDIA

The transient propagation in multi layered two phase media under axisymmetric dynamic load is considered and a set of analytic solutions are obtained in the integral form. To obtain the transient solutions,the field equations in cylindrical coordinates on the basis of the modified Biot's linear theory for two phase media are presented and the uncoupled governing equations are then established without the aid of scalar potentials. By means of Laplace Hankel mixed transforms, a set of solutions in transfo...

1996, 28(3): 308-318. doi: 10.6052/0459-1879-1996-3-1995-335

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A STUDY OF DYNAMIC MECHNICAL RESPONSE AND CONSTITUTIVE MODEL OF ENERGETIC MATERIALS

An experiment equipment of triaxial dynamic compression is used.Measurements of domestic Comp. B have been made in triaxial compression as a function of temperature and strain rate. Young's moduls, yield strenghth and Poisson's ratio have been obtained. The experiment results show that there is clear temperature and strain rate dependence in Comp. B. The Young's modulus and yield strength of Comp. B are larger than those of TNT. Based on the thermally activated theory a plastic flow constitutive model is su...

1996, 28(3): 319-327. doi: 10.6052/0459-1879-1996-3-1995-336

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AN ALGEBRAIC STRUCTURE OF CHAPLYGIN′S EQUATIONS

The present paper studies the algebraic structure of Chaplygin's equations of nonholonomic systems. First, it gives a contravariant algebraic form of the equations. Secondly, it proves that they possess a consistant algebraic structure and a Lie algebraic structure under some conditions. Finally,it gives two examples to illustrate the application of the result.

1996, 28(3): 328-335. doi: 10.6052/0459-1879-1996-3-1995-337

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ON HEMODYNAMIC MODEL OF CEREBRAL CIRCULATION A LUMPED PARAMETERS MODEL OF PULSATILE FLOW

The cerebravascular disease is very related with the abnormal hemodynamic state of cerebral circulation. There are some different characteristics between the cerebral circulation and the systemic circulation of human.In clinical application, it is necessary to set up a hemodynamics model which not only has the principal characteristics of the cerebral circulation but also can be used easily to analyse the cerebravascular dynamics index(CVDI). According to the steady flow model of Willis circulation, we set ...

1996, 28(3): 336-346. doi: 10.6052/0459-1879-1996-3-1995-338

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STUDIES OF BURNER LATERAL TURBULENT MIXING AND DIFFUSION USING GAS TRACER ANALYSIS

The characteristics of lateral turbulent mixing and diffusion between primary air(low swirl) and secondary air(no swirl) of the burner with side located secondary air were studied carefully by gas tracer analysis. The profiles of mixture concentration and mixing intensity at various cross sections along the axis were discussed. The effects of them on fuel ignition were also analyzed. The turbulent exchange coefficient is calculated from time mean equation. The results are of practical significance for ...

1996, 28(3): 347-351. doi: 10.6052/0459-1879-1996-3-1995-339

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ELASTIC PLASTIC ASYMPTOTIC ANALYSIS OF CRACKS ON BIMATERIAL INTERFACE UNDER THREE DIMENSIONAL CONSTRAINT

An investigation on the near tip fields of cracks lying on the interface of two strain hardening materials has been conducted under three dimensional(3D) stress constraint. By using the J 2deformation theory and cons idering the 3D stress constraint factor T z, an exact asymptotic solution was obtained. It is found that there is strong effect of 3D constraint on the continuities and singularities of radial stress and equivalent stress.

1996, 28(3): 352-359. doi: 10.6052/0459-1879-1996-3-1995-340

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THE APPLICATION OF IMPORTANT SAMPLING METHOD IN TUBULAR JOINT FATIGUE RELIABILITY ANALYSIS

The paper calculates the fatigue failure probability by using Monte carlo simulation method of important sampling, and compares with the direct Monte carlo method. The results show:the important sampling method can greatly imporve calculation's efficiency.

1996, 28(3): 359-362. doi: 10.6052/0459-1879-1996-3-1995-341

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BIFURCATIONS OF A CLASS OF STRONGLY NONLINEAR OSCILLATION SYSTEMS

1996, 28(3): 363-369. doi: 10.6052/0459-1879-1996-3-1995-342

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BENDING PROBLEMS OF NON UNIFORM CYLINDRICAL ORTHOTROPIC CIRCULAR PLATE

The bending problems of non uniform cylindrical orthotropic circular plate under uniformly distributed transverse load is studied.Asymptotic solutions for the bending of cylindrical orthotropic circular plate with reducing stiffness varying exponentially with radius are obtained. The asymptotic solutions of such circular plates with rigidly fixed edges and simply supported edges are given. The calculation examples show the influence of non uniformity on the maximum deflection.

1996, 28(3): 370-375. doi: 10.6052/0459-1879-1996-3-1995-343

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A METHOD FOR THE STABILITY ANALYSIS OF LOCAL ARTIFICIAL BOUNDARIES

Local artificial boundaries may induce numerical instability while being adopted in finite element or finite difference simulation of wave motion in infinite media. Starting from the step by step integral algorithm and considering the coupling between the motion of the boundarynodes and the internal nodes, the authors bring about a method which can give an approximate stability criterion of a local artificial boundary in numerical simulation of multi dimensional wave motion. The stability analysis of the...

1996, 28(3): 376-380. doi: 10.6052/0459-1879-1996-3-1995-344

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MEASUREMENTS OF EFFECT OF LONGITUDINAL VORTICES ON TURBULENT FLOW NEAR WALL ITH LDV METHOD

This paper presents the effect of longitudinal vortices(a single vortex, upwash vortex pair and dowash vortex pair) on turbulent flow near wall region with LDV methods. In downwash region, the fluid with higher streamwise velocity and lower turbulent intensity moves toward the wall; while in the upwash region,the fluid with lower streamwise velocity and higher turbulent intensity moves away from the wall.

1996, 28(3): 381-384. doi: 10.6052/0459-1879-1996-3-1995-345

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1996 Vol. 28, No. 3

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