力学学报

A STUDY OF THE FLOW STRUCTURE AROUND A CONSTANT-RATE PITCHING AIRFOIL

This paper presents a flow visualization study of the flow structure arounda constant-rate pitching airfoil using hydrogen bubble technique. It is shown that there exist three types of separated flow structure for different pitching rate. The time evolution of the dymamic stall vortex, shear layer vortices and trailing edge vortex is visualized, and their mutual interaction is studied. The flow visualization results, combining with theoretical analysis in literature, qualitatively explains the mechanism of ...

1992, 24(5): 517-521. doi: 10.6052/0459-1879-1992-5-1995-770

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PRESSURE DISTRIBUTIONS ON TWO CIRCULAR CYLINDERS OF SIDE-BY-SIDE ARRANGEMENTS IN HIGH-TURBULENCE FLOW AT HIGH REYNOLDS NUMBER

This paper presents time-mean as well as fluctuating pressure distributions on single and two identical circular cylinders of side-by-side arrangements under various gap ratios N/d, which were tested in high-turbulence flow (1u=10%) at two high Reynolds numbers Re of 1.95×105 and 6.5 × 10" respectively.The results show that due to the high-turbulence in oncoming flow, the flow around single cylinder at Re = 1.95×105 becomes turbulent separated. The spectrum-analysis shows, that the vortex shedding from the ...

1992, 24(5): 522-528. doi: 10.6052/0459-1879-1992-5-1995-771

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串列双方柱体流体动力载荷研究

The characteristics of the flow past two square-section cylinders in a tandem arrangement were studied experimentally. The vortex-shedding frequencies, time-mean drag forces, time-varying lift and drag forces were obtained for various spacing ratios S/D(S, spacing; D, width of the cylinder). The Reynolds number of the experiment was 6×103, the spacing ratios were in the range 0.5 to 10. It was found .that the critical spacing ratios were in the range 2.5 to 3.0, and the flow can be divided into two regimes ...

1992, 24(5): 529-534. doi: 10.6052/0459-1879-1992-5-1995-772

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VISCOUS FLOW IN HELICAL PIPES WITH NARROW ANNULAR CROSS SECTION

The Navier-Stokes equations are established for a nonorthognal coordinate-system based on tensor analysis. The zeroth-, the first- and the second-order (t = 0) analytic solutions are obtained for fully developed flow in helical pipes with narrow annular cross section using a perturbation method. It is found that there is a secondary flow on the annular cross section.

1992, 24(5): 535-545. doi: 10.6052/0459-1879-1992-5-1995-773

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THE TWO-FLUID MODEL OF TURBULENT BUOYANT RECI RCULATING OIL-WATER TWO-PHASE FLOW

In the natural world and many fields of engineering, there often exist one kind of two-phase flow with recirculation and buoyancy in which the physical properties of two phases differ greatly with each other, in certain conditions, the field of one parameter may have a sudden decrease or jump. This give much difficulties to the mathematical simulation and the numerical computation. This paper takes refined forecasting model of oil pollution as basic target, widely deals with the theory and method of refined...

1992, 24(5): 546-555. doi: 10.6052/0459-1879-1992-5-1995-774

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THE RELAXATION STRUCTURE OF TWO-PHASE DETONATIONS

The relaxation structure of two-phase detonations, as distinguished from homogeneous one obviousely, depends on not only the effect of chemical reaction but also the effect of two-phase flow. It has been shown from the theoretical analysis that the influences of two kinds of factors on the flow parameters in the relaxation zone are sometimes contradictory. It makes the profiles of flow variables quite complicated, which are no longer monotonic as those in homogeneous one. The tendencies of profiles obtained...

1992, 24(5): 556-566. doi: 10.6052/0459-1879-1992-5-1995-775

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THE EFFECT OF LOADING HISTORY ON CYCLIC HARDENING

In this paper, the cyclic hardening behavior of 45 # steel and LY-12CZ aluminum alloy under proportional and non-proportional combined loadings of tension and torsion at normal room temperature has been investigated.The experimental results show that the cyclic hardening levels are different for different loading paths. The least is for the pure torsion, while the highest is for the circular path. The authors have especially investigated the effect of different cyclic history on the amplitudes of stabilized...

1992, 24(5): 567-573. doi: 10.6052/0459-1879-1992-5-1995-776

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EXACT SOLUTION FOR THICK LAMINATE WITH CLAMPED EDGES

Giving up any assumptions about displacement models and stress distribution, based on the Refs. [1] and [2] and introducing 6-function, the state equation is established for thick laminate with clamped edges under any given loads. The exact solutions are presented for the statics, dynamics and buckling. All equations of elasticity can be satisfied, and all elastic constants can be taken into account.

1992, 24(5): 574-583. doi: 10.6052/0459-1879-1992-5-1995-777

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IMPULSIVE RESPONSE PROBLEMS FOR A CLASS OF NON-CIRCULAR CAVITY

本文用扰动形式的映射函数对非圆空腔在冲击载荷作用下的动态响应问题进行了摄动求解,给出了“0”级及“1”级摄动解的具体算式及阶跃脉冲载荷作用下椭圆腔的数值算例。

1992, 24(5): 584-592. doi: 10.6052/0459-1879-1992-5-1995-778

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REFLECTION OF SIMPLE WAVES IN ELASTIC HALF SPACE

In this paper the generalized characteristic of centered simple wave in elastic body is studied. Then characteristic method is employd to solve the wave reflection at boundary of half space. Reflection coefficients and amplifications of velocity components of P-wave and S-wave are expressed in close form and their three-dimensional diagrams are also given.

1992, 24(5): 593-603. doi: 10.6052/0459-1879-1992-5-1995-779

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DYNAMIC ANALYSIS OF THE WALKING SUPPORTED BY THREE FEET OF A QUADRUPED WALKING MACHINE WITH PANTOGRAPH LEGS

The walking supported by three feet of a quadruped walking machine with-pantograph legs is discussed in this paper. The semi-inverse solution is supplied for the kinematic analysis. The kinematic supplementary conditions are determined in advance. D'Alembert's principle and Jourdain's principle are supplied for the dynamic analysis. The difficulty of statical indeterminateness is overcome by introducing the optimum conditions. The dynamic problems of an actual quadruped walking machine are calculated.

1992, 24(5): 604-613. doi: 10.6052/0459-1879-1992-5-1995-780

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THEORETICAL SOLUTION ON HEAT TRANSFER IN OSCILLATORY PIPE FLOW

Starting from the equations of motion of the oscillatory pipe flow, together with the energy equations of the fluid and of the pipe wall, by solving the set of ordinary differentia] equations using variable transformation and taking pipe wall effect into account, a general analytical solution of the axial heat transfer of oscillatory flow is obtained. Based upon this analytical solution, formulae for heat transfer in various special cases can be derived, some of which reduce to known analytical results. The...

1992, 24(5): 614-619. doi: 10.6052/0459-1879-1992-5-1995-781

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THE NONLINEAR STABILITY OF DOUBLE LAYER COATING FLOWS

This paper considers the nonlinear stability of double layer coating flows. The nonlinear subcritical threshold and all order evolutional coefficient are obtained for double layer coating flows.

1992, 24(5): 620-624. doi: 10.6052/0459-1879-1992-5-1995-782

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SHOCK WAVE INDUCED UNSTEADY DRAG OVER TWO-DIMENSIONAL CIRCULAR CYLINDER IN AIR

A shock tube can be used as a convenient aerodynamic testing facility. Thus it was extensively applied to experimental research of transonic and hypersonic flow. However, due to its very short working time quantitative flow measurement such as pressure distribution around a model installed in the shock tube is very difficult. This paper reports the results of unsteady pressure distribution and unsteady drag measurement over circular cylinder installed in a 50mm × 200mm shock tube equipped with Mach-Zehnder ...

1992, 24(5): 625-628. doi: 10.6052/0459-1879-1992-5-1995-783

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THE VARIATIONAL PRINCIPLE FOR ELASTIC CREEP-DAMAGE PROBLEM

The parametric vanational principle (PVP) is powerful to solve the nonlinear unspecified boundary problems in continuum mechanics. By the PVP, this paper studies the elastic-creep-damage problem. The proposed principle, a development of optimum control theory, is to minimize a constructed potential energy functional under the constrained conditions which are converted from the creep-damage equations. The mathematical proof of principle is given. Also, the paper quotes the results of creep experiments of 2.2...

1992, 24(5): 629-634. doi: 10.6052/0459-1879-1992-5-1995-784

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GENERALIZED CONFORMING THIN PLATE TRIANGULAR ELEMENT BY USING SEMILOOF CONSTRAINTS

In this paper, the merits of both generalized conforming element and Semi-Loof element are utilized to establish a nine-DOF triangular thin plate element..By using the concept of generalized conforming element, the present element can pass Irons' patch test. By using semiLoof constraints, only discrete (point) compatibility conditions ate used. This new element is the best nine-DOF triangular thin plate bending element currently available.

1992, 24(5): 635-638. doi: 10.6052/0459-1879-1992-5-1995-785

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INVARIANT MANIFOLD OF STATIONARY MOTION FOR CHAPLYGIN'S NONHOLONOMIC SYSTEMS

In this paper, we study the invariant manifold of stationary motion and the invariant manifold of stationary motion with respect to partial variabiis for the Chaplygin's non-stolonomic systems, and give an example to illustrate the application of the result.

1992, 24(5): 639-644. doi: 10.6052/0459-1879-1992-5-1995-786

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