力学学报

NUMERICAL SIMULATION OF ROTOR/STATOR INTERACTION IN TURBOMACHINERY BY USE OF A LAGRANGIAN ——DISTURBANCE VORTEX METHOD 1)

A disturbance vortex method for simulating unsteady rotor/stator interaction in turbomachinery is presented in this paper. The basic idea of the method is that the numerical steady solutions in the relative frame for rotor and absolute frame for stator are taken as input, which can give an initial description of the unsteady disturbance flow field. To calculate the unsteady response to these disturbances, the algorithm utilizes the Lagrangian vortex method (to trace the trajectories of vortices directly) t...

1998, 30(3): 257-266. doi: 10.6052/0459-1879-1998-3-1995-125

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A COUPLING MODEL OF THE LAND ATMOSPHERE INTERACTION WITH CANOPY INFLUENCE 1)

, Jiachun Li

A coupling micrometeorological model for SPAC system over maize field in Huang Huai Hai Plain is presented. The model consists of turbulent flow equation system and canopy radiation assumption regarding energy balance for a leaf. The canopy is divided into several layers, aiming at revealing the vertical profiles of mean quantities within it and providing scientific basis for parameterization of terrestrial processes. The model is shown capable of well simulating the microenvironment of maize canopy in go...

1998, 30(3): 267-276. doi: 10.6052/0459-1879-1998-3-1995-126

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TOPOLOGY OPTIMIZATION OF TRUSS STRUCTURES BASED ON RELIABILITY 1)

The problem of topology optimization of truss structures based on reliability is studied in this paper. First of all, the structural analysis under the action of random loads is carried out and the mean value and variance of all joint's displacement and bar's stress in the structure are obtained by means of three fundamental equations (equilibrium, physical and geometric) in structural mechanics, as well as the property of moment of random variable. According to this, the mathematical model of topology opt...

1998, 30(3): 277-284. doi: 10.6052/0459-1879-1998-3-1995-127

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ITERATIVE METHOD USING CONSISTENT MASS MATRIX IN AXISYMMETRICAL FINITE ELEMENTS FOR ANALYSIS OF HYPERVELOCITY IMPACT 1)

We present in this paper the iterative method using consistent mass matrix in axisymmetrical finite elements for analysis of hypervelocity impact. To retain the advantage of the integration on an element by element basis which is at the heart of the modern hydrocodes, we suggest the iterative process where the first step is to solve for accelerations at an advanced time step by using the lumped mass approach, then iterate using a consistent mass matrix to improve the estemate. Examples are given to show i...

1998, 30(3): 285-291. doi: 10.6052/0459-1879-1998-3-1995-128

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HOMOCLINIC ORBITS OF THE TRUNCATED SYSTEMS OF SINE-GORDON EQUATION 1)

In this paper the existence of the homoclinic orbits defined by Wiggins is proved, by use of ODE on the generalized asymptotic inertial manifold for the Sine Gordon equation. We give explicit conditions (in terms of the system parameters) for the model to possess a symmetric pair of homoclinic orbits to a fixed of saddle focus type, chaotic dynamics follow from a theorem of Silnikov. This provides a mechnism for chaotic dynamics geometrically similar to that observed by Bishop et al.,namely, a random...

1998, 30(3): 292-299. doi: 10.6052/0459-1879-1998-3-1995-129

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A NEW VIOLATION CORRECTION METHOD FOR CONSTRAINT MULTIBODY SYSTEMS 1)

A new method is developed to correct the violations in constraint multibody systems. Compared with any conventional methods, this method has clear physical meaning, less calculation and obvious correction effect. Besides, this method has little influence on the quality of the original dynamic equations. Using this method, the violations of constraint equations can be limited efficiently in the given accuracy. Suggest that the integration is at the step t=t k , and the generalized coordinates k do not...

1998, 30(3): 300-306. doi: 10.6052/0459-1879-1998-3-1995-130

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INFINITE DIMENSIONAL LIE ALGEBRA WITH A NEW POISSON BRACKET 1)

For the Hamiltonian formulation of the Korteweg de Vires equation (KdVequation), C.S. Gardner defined a Poisson bracket. In this paper a brand new bracket is defined. It is easily verified that the new bracket possesses three properties of the Poisson bracket, bilinearity,skew symmetry, Jacobi identity. The new Poisson bracket has a close connection with C.S. Gardner's definition. In the framework of the new Poisson bracket, all the first integrals of the KdV equation constitute an infinite dimension...

1998, 30(3): 307-313. doi: 10.6052/0459-1879-1998-3-1995-131

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MULTIFRACTAL BEHAVIORS OF FRACTURE SURFACES IN ROCKS 1)

Following fractal geometry introduced by B.B. Mandelbrot,many researchers have described quantitatively the roughness of fractured surfaces and also tried to establish the relationship between the fractal dimension and mechanical parameters. Extensive experiments and measurement show that, to some extent, fracture surfaces in rocks exhibit statistical fractal behavior in a certain range of scale. In fact, understanding of fractal behavior of fracture surfaces advances step by step. Initially, people paid at...

1998, 30(3): 314-320. doi: 10.6052/0459-1879-1998-3-1995-132

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NUMERICAL MODELLING OF POLLUTANT TRANSPORT IN UNSATURATED/SATURATED SOILS 1)

A numerical model to simulate miscible pollutant transport through unsaturated/satu-rated soils is presented. The model is composed of the two coupled phases: the hydromechanical analysis of the two immiscible fluids through the deforming porous medium to determine the velocity fields of the porous water and air flows and the saturation degrees; the pollutant transport analysis through the porous medium. The emphasis of the present paper for the numerical modelling is specially given to the second phase. T...

1998, 30(3): 321-332. doi: 10.6052/0459-1879-1998-3-1995-133

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THE FLOW OF ER FLUIDS IN A TUBE OF RECTANGULAR CROSS 1)

The main feature of flows of electrorheological (ER) fluids is the deformation of chain like structures of particles. The simplest of all structures in ER fluids is a single ER chain. There are two kinds of deformation of chains in ER devices: those produced by moving electrodes such as in ER clutches, and those produced by flow such as in ER valves.Due to the relative movement between basic fluids and ER chains, the analysis of ER chains under flow is more challenging. In this paper an analytical study o...

1998, 30(3): 333-339. doi: 10.6052/0459-1879-1998-3-1995-134

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EFFECT OF BOUNDARY ABSORPTION UPON UNSTEADY DISPERSION 1)

In the nature, mass transfer is dominated by shear dispersion when the shear effects in flow are very strong. It is G.I. Taylor (1953) who first investidated such problem and gotten a formula for laminar flow.Two exceptions to the Taylor's theory are early stage of dispersion process and shear dispersion with boundary absorption, which the Smith(1981, 1983) gave the description by a delay diffusion equation. Liu(1994) described the two dimensional contaminant dispersion with memory properties. In this pap...

1998, 30(3): 340-347. doi: 10.6052/0459-1879-1998-3-1995-135

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REAL TIME NEUROCOMPUTING THEORY AND NUMERICAL SIMULATION ON ELASTIC MECHANICS 1)

ow to reduce the time in structural analysis and design has been alwaysa remarkable problem for engineers and researchers. Because of the nonlinear and parallel processing ability, Neural Networks (NN) has been widely used. In this paper, some fundamental problems about the applications of NN in structural analysis have been studied through theoretical analysis and numerical simulation. Based on the Hopfield NN, the concept of Energy Functional and the Minimal Potential Principle, the computation of elastic...

1998, 30(3): 348-353. doi: 10.6052/0459-1879-1998-3-1995-136

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NECKING AND NECK PROPAGATION IN ORIENTED ANISOTROPY AMORPHOUSGLASSY POLYMERS 1)

Polymeric mechanics is a rising frontier science based on polymeric physics and continuum mechanics. The research on macro and micro mechanical behavior of polymers will provide the theoretic foundation and analyzing way for increasing ductility of the polymers and for improving their formability. At present, a subject on the field is to study deformation localization development and flow character of the polymers. In this paper, a 3D expression of the back stress tensor describing oriented anisotropy p...

1998, 30(3): 354-362. doi: 10.6052/0459-1879-1998-3-1995-137

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CHAOTIC ATTITUDE MOTION OF NON SPINNING 1)

The chaotic planar motion of rigid spacecraft on an elliptic orbit in the gravitational field with air drag and internal damping and its control are investigated.Research on chaotic attitude motion of spacecraft can not only provide nonlinear dynamics with engineering background, but also furnish the design of spacecraft with a new view point. Controlling chaos is a new frontier of nonlinear dynamics and control engineering. The mathematical model of attitude motion of the spacecraft with a actuator is deri...

1998, 30(3): 363-369. doi: 10.6052/0459-1879-1998-3-1995-138

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THE FINITE ELEMENT ANALYSIS OF THE SHAPE MEMORY ALLOY PIPE CONNECTOR 1)

This paper reviews the three-dimension Shape Memory Alloys constitutive relation present by Boyd and Langoudas. Since the nonlinear consitutive equation is difficult to be used in finite element method, a linear incremental consistutive equation is derived from the nonlinear one. The finite element equations in Total Lagrangian from are derived on the base of the linear increment constitutive equations and the program is also developed considering the effects of both stress and temperature. To verify the ...

1998, 30(3): 370-378. doi: 10.6052/0459-1879-1998-3-1995-139

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A HIGHER ORDER NONLINEAR FEM FOR RC PLATES

Based on the high order nonlinear membrane elements presented in Reference , the formulation of a higher order rectangular 14 noded RC Plate element is proposed for the analysis of RC panel walls. The nodal DOF of the element presented are assumed to be in plane displacements u, v; transverse deflection w and cross section rotations ψ x, ψ y , and their derivatives (with respect to x ). Of the element displacements consequently are 3rd order Hermite polynomial in the x direction and ...

1998, 30(3): 379-384. doi: 10.6052/0459-1879-1998-3-1995-140

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1998 Vol. 30, No. 3

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