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NUMERICAL SIMULATION OF HYPERSONIC LAMINAR WAKE FLOW

The hypersonic laminar wake flow behind spherically blunted cone is studied by solving Navier-Stokes equations with NND schemes (Non oscillatory, containing no free parameters and dissipative scheme). The bow shock, corner expansion fan, wake shock and free layer in the wake region are captured successfully. The calculated pressure, temperature and velocity distributions along the wake centerline agree with experimental date satisfactorily. Especially, the history of vortex in the recirculation region start...

1992, 24(4): 389-399. doi: 10.6052/0459-1879-1992-4-1995-753

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SCALAR VARIANCE SPECTRUM IN ENSTROPHY CASCADE RANGE OF 2-D TURBULENCE

The nonequilibrium statistical-mechanics theory of a passive scalar field convected by turbulence is applied to study the variance spectrum G(k) of a 2-D (two-dimensional) turbulent passive scalar field in the convective range, while the velocity spectrum E(k)= cX2/3k-3 in the enstrophy cascade range, here X is the enstrophy dissipation rate, C is a dimensionless coefficient. The closure equations in this case are divergent due to the nonlocalness of the cascade process in 2-D turbulence. In order to overco...

1992, 24(4): 400-403. doi: 10.6052/0459-1879-1992-4-1995-754

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THE INFLUENCE OF PERIODIC LOADS ON NON-NEWTONIAN THERMAL ELASTOHYDRODYNAMIC LUBRICATION

The influence of periodic loads on the thermal elastohydrodynamic lubrication (TEHL) in line contacts was investigated numerically in this paper. The Ree-Eyring's theological model was employed to describe the non-Newtonian behavior of the lubricant. The results show that the periodic loads can dampen the changes of TEHL films and increase to some extent the film thicknesses. The dynamic loads with very high frequency can alter significantly the rules of pressure and temperature distributions, the non-Newto...

1992, 24(4): 404-410. doi: 10.6052/0459-1879-1992-4-1995-755

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THE LIQUID BRIDGE CONFIGURATION AND EFFECTS OF BUOYANCY IN THERMOCAPILLARY CONVECTION

The effects of gravity and thermocapillary convection in the liquid bridge with different aspect ratio L/D are studied in the present paper. Two flow cells appear in the liquid bridge. If L/D is longer, however, the flow pattern is not necessarily associated with the thermocapillary oscillatory convection. In order to simulate the space microgravity situation on the ground laboratory, the height of the liquid bridge must be smaller than, for example, 1.5mm. The convection and thermal transportation in a liq...

1992, 24(4): 411-417. doi: 10.6052/0459-1879-1992-4-1995-756

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ONE-DIMENSIONAL FLOW MODEL FOR COAL-GAS OUTBURSTS AND INITIATION CRITERION

To analyse the mechanism of coal-gas outbursts, a one-dimensional flow model is established. A break-start criterion of coal, as a basic criterion of outbursts, is given. In this ideal model, the tectonic pressure before excavation, as a load on coal mass, affects break-start and then the flow field. The flow field is decoupled with the stress field of coal, so that the gas seepage, the break-start of coal and the consequent two-phase flow, and pure gas flow, can be analysed independently of the stress fiel...

1992, 24(4): 418-431. doi: 10.6052/0459-1879-1992-4-1995-757

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ON THE RECIPROCAL THEOREM AND ADJOINT SIMPLETIC ORTHOGONAL RELATION

The paper indicates that the simpletic orthogonal relation among eigenvectors of a Hamiltonian matrix can be derived by the reciprocal theorem of structural mechanics. It also presents the transformation which makes a Jordan-type matrix preserve the structure of a Hamiltonian matrix and proves that suitable arrangement of secondary eigenvectors keeps simpletic orthogonality among them.

1992, 24(4): 432-437. doi: 10.6052/0459-1879-1992-4-1995-758

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EXTENSION OF THE INERTIAL MANIFOLD CONCEPT AS SUGGESTED BY A SPECIAL CASE

The concept of inertial manifold[5] requires exponential convergence of all trajectories to a unique attractor, which can hardly be satisfied in many physical problems, e.g. the sine-Gordon equation[4]. Properties of an artifical example in the paper suggest a generalized form of inertial manifold, which cancels the prerequisite that the global attractor is unique. This generalized concept is used to the sine-Gordon equation.

1992, 24(4): 438-445. doi: 10.6052/0459-1879-1992-4-1995-759

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SINGULAR SOLUTIONS OF AXISYMMETRIC ELASTODYNAMIC PROBLEM FOR MULTILAYERED HALFSPACE

In the paper, the singular solutions of axisymmetric elastodynamic problem for the multilayered halfspace due to unit dynamic load acting within layered media are derived in time domain with the aid of Laplace-Hankel mixed transforms and transfer matrix method. A numerical computation of these solurions is also proposed using a fast Hankel transform algorithm. Two examples show that the solutions can be readily evaluated and the numerical results have considerably high precision. The presented solutions can...

1992, 24(4): 446-457. doi: 10.6052/0459-1879-1992-4-1995-760

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HYDROMECHANICAL ANALYSIS OF LUNATE-TAIL SWIMMING PROPULSION

This paper uses the three-dimensional waving plate model and optimummotion theory to analyse lunate-tail swimming propulsion, and so a comparatively systmatic study of the three classes of fish propulsive modes has been carried out. Theoretical results show that lunate-tail, with high-aspect-ratio, spanwise tapering tip and moderate sweepback angle, of many fast-swimming ocean animals, may gain the nearly best propulsive characteristics. Estimation of a porpoise swimming performance gives satisfactory resul...

1992, 24(4): 458-465. doi: 10.6052/0459-1879-1992-4-1995-761

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AN APPROACH LINKING TEST AND B. E. M. ANALYSIS TO IDENTIFY MODAL SHAPE PARAMETERS

In experimental modal analysis, it is necessary to measure the response data in directions of all degrees of freedom to obtain the complete mode shape information. In order to decrease the number of measurement points and, especially, to complement the data of those degrees of freedom which are unable to be detected, this paper suggests an approach utilising the analytical relations derived by B.E.M. to extend the dynamic measurement data. By use of this method, in experimental modal analysis, we can take l...

1992, 24(4): 466-472. doi: 10.6052/0459-1879-1992-4-1995-762

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DISCRETE ANALYSIS METHOD OF RANDOM VIBRATION

Discrete Analysis Method of Random Vibration is proposed in this paper. Anew recurrence formula which can be used to calculate the stationary and non-stationary mean and mean square responses is given, and its unconditional stability is proved. By using of this formula, the accurate mean and mean square responses of a linear or an equivalent linearized nonlinear vibration problem can be obtained.

1992, 24(4): 473-479. doi: 10.6052/0459-1879-1992-4-1995-763

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APPLICATION OF THE TRANSVERSALITY THEORY ON THE PROBLEMS OF STRUCTURAL STABILITY OF IMPACT VIBRATION SYSTEMS

This paper discusses the structural stability of impact vibration systemsby means of the transversality theory. Relationships among structural stability stability, loss of stability and bifurcation are also discussed.

1992, 24(4): 480-487. doi: 10.6052/0459-1879-1992-4-1995-764

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LIF QUANTITATIVE CONCENTRATION FIELD MEASURE-MENT FOR THE MIXING FLOWS OF FREE JETS

The instantaneous quantitative measurements of the concentration field using Laser Induced Fluoresence (LIF) technique with a Digital Image (CCD) capture & processing system and the simplified calibration for the free jet mixing flows are presented. Also some digital image process method used for better displaying the flow structures and some preliminary results are discussed.

1992, 24(4): 488-492. doi: 10.6052/0459-1879-1992-4-1995-765

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REFLECTION AND DIFFRACTION OF THE 2-D DAM BREAK WAVE

The propagation, reflection and diffraction of 2-dimensional dam break wave are studied by solving the shallow water equations with a Godunov's scheme which is derived in detail. The compact expressions of Hc,d and Vo,d2, the contact discontinuity of water surface elevation and velocity at the boundaries of general cells are also given to complete the calculation. The numerical results are quite satisfactory compared with the measurements and the 1-dimensional analysis, so they are useful for the dam design...

1992, 24(4): 493-499. doi: 10.6052/0459-1879-1992-4-1995-766

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SHAKEDOWN ANALYSIS OF KINEMATIC-HARDENING STRUCTRURES

It is pointed and proved that it is impossible for a kinematic-hardening structure to involve incremental collapase, and it can only fail by alternating plasticity. Time-inde pendent equilibriant forces have no influence on shakedown of kinematichardening structures.

1992, 24(4): 500-503. doi: 10.6052/0459-1879-1992-4-1995-767

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EXPERIMENTAL INVESTIGATION OF FIELD OF THE MODE III CRACK TIP BETWEEN DISSIMILAR MATERIAL

In this paper, the displacement field for the mode III interface crack between two materials is obtained by using the laser holographic interferometry. Through experimental data processing control parameters KIII, J of stress field intensity around crack tip are obtaied, and the applicable region of local solution is given. The continuity condition across the interface between two materials is studied. Rationality of the results is analysed. For contrast, specimen of homogeneous material was testedd and dat...

1992, 24(4): 504-510. doi: 10.6052/0459-1879-1992-4-1995-768

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A CURVED STIFFENER BEAM ELEMENT FOR LARGE DEFLECTION ANALYSIS OF COMPOSITE SHELLS

The paper studies nonlinear F. E. analysis of stiffened shells, presenting beam element to simulate the stiffeners. The beam element has curved axis, thin-walled cross section with arbitrary shape and arbitrary layup, and is fully compatible with the shell element. Eccentricity is also accounted for. The material may be isotropic or composites.

1992, 24(4): 511-516. doi: 10.6052/0459-1879-1992-4-1995-769

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1992 Vol. 24, No. 4

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