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2012年 第33卷 第4期    刊出日期：2012-04-15

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论文

Time-dependent MHD Couette flow of rotating fluid with Hall and ion-slip currents

B. K. JHA;C. A. APERE

2012, 33(4):  399-410.  doi:10.1007/s10483-012-1559-9

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The unsteady magnehydrodynamics (MHD) Couette flow of an electrically conducting fluid in a rotating system is investigated by taking the Hall and ion-slip currents into consideration. The derived fundamental equations on the assumption of a small magnetic Reynolds number are solved analytically with the well-known Laplace transform technique. The unified closed-form expressions are obtained for the velocity and the skin friction in the two different cases of the magnetic field being fixed to either the fluid or the moving plate. The effects of various parameters on the velocity and the skin friction are discussed by graphs. The results reveal that the primary and secondary velocities increase with the Hall current. An increase in the ion-slip parameter also leads to an increase in the primary velocity but a decrease in the secondary velocity. It is also shown that the combined effect of the rotation, Hall, and ion-slip parameters determines the contribution of the secondary motion in the fluid flow.

Exact solutions in generalized Oldroyd-B fluid

T. HAYAT;S. ZAIB;S. ASGHAR;A. A. HENDI

2012, 33(4):  411-426.  doi:10.1007/s10483-012-1560-7

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This investigation deals with the influence of slip condition on the magnetohydrodynamic (MHD) and rotating flow of a generalized Oldroyd-B (G. Oldroyd-B) fluid occupying a porous space. Fractional calculus approach is used in the mathematical modeling. Three illustrative examples induced by plate oscillations and periodic pressure gradient are considered, and the exact solutions in each case are derived. Comparison is provided between the results of slip and no-slip conditions. The influence of slip is highlighted on the velocity profile by displaying graphs.

Convective heat transfer from two rotating circular cylinders in tandem arrangement by using lattice Boltzmann method

H. NEMATI;M. FARHADI;K. SEDIGHI;M. M. PIROUZ;N. N. ABATARI

2012, 33(4):  427-444.  doi:10.1007/s10483-012-1561-6

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The numerical investigation of the two-dimensional laminar flow past two rotating circular cylinders in the tandem arrangement is conducted by the lattice Boltzmann method. The numerical strategy is used for dealing with curved and moving boundaries of the second-order accuracy for velocity and temperature fields. The effects of various rotational speed ratios and gap spacing are studied with the Reynolds number of 100 and the Prandtl number of 0.71. A varied range of rotational speed ratios are investigated for four different gap spacing, i.e., 3.0, 1.5, 0.7, and 0.2. The results show that, for the first cylinder, the lift and drag coefficients for large gap spacing are similar to those for a single cylinder; for the second cylinder, the lift coefficient descends with the increase in the angular velocity for all gap spacing, while the drag coefficient ascends except for the gap spacing of 3.0. The results of the averaged periodic Nusselt number on the surface of the cylinders show that, for small distances between the cylinders and low angular velocities, conduction is a dominant mechanism of heat transfer, but for large distances and high angular velocities, convection is the main mechanism of heat transfer.

Flow and heat transfer over hyperbolic stretching sheets

A. AHMAD;S. ASGHAR

2012, 33(4):  445-454.  doi:10.1007/s10483-012-1562-6

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The boundary layer flow and heat transfer analysis of an incompressible viscous fluid for a hyperbolically stretching sheet is presented. The analytical and numerical results are obtained by a series expansion method and a local non-similarity (LNS) method, respectively. The analytical and numerical results for the skin friction and the Nusselt number are calculated and compared with each other. The significant observation is that the momentum and the thermal boundary layer thickness decrease as the distance from the leading edge increases. The well-known solution of linear stretching is found as the leading order solution for the hyperbolic stretching.

Investigation of tensile deformation behavior of PC, ABS, and PC/ABS blends from low to high strain rates

尹征南;王铁军

2012, 33(4):  455-464.  doi:10.1007/s10483-012-1563-x

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This paper experimentally studies the tensile deformation behavior of polycarbonate (PC), acrylonitrile-butadiene-styrene (ABS), and PC/ABS blends (with the blending ratios of PC to ABS being 80:20, 60:40, 50:50, and 40:60) from low to high strain rates. Using the universal MTS-810 machine and the split Hopkinson tension bar (SHTB) testing system, the quasi-static and impact tension tests are carried out at the room temperature. The curves of the true stress and the true strain are obtained. The deformation behaviors of PC, ABS, and PC/ABS blends are characterized in detail. The linear relationship between the strain rate and the yielding stress is given.

Coupled thermo-hygro-mechanical damage model for concrete subjected to high temperatures

李忠友;刘元雪

2012, 33(4):  465-482.  doi:10.1007/s10483-012-1564-x

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Based on the theory of mixtures, a coupled thermo-hygro-mechanical (THM) damage model for concrete subjected to high temperatures is presented in this paper. Concrete is considered as a mixture composed of solid skeletons, liquid water, water vapor, dry air, and dissolved air. The macroscopic balance equations of the model consist of the mass conservation equations of each component and the momentum and energy conservation equations of the whole medium mixture. The state equations and the constitutive model used in the model are given. Four final governing equations are given in terms of four primary variables, i.e., the displacement components of soil skeletons, the gas pressure, the capillary pressure, and the temperature. The processes involved in the coupled model include evaporation, dehydration, heat and mass transfer, etc. Through the process of deformation failure and the energy properties, the mechanics damage evolution equations are established based on the principle of conversation of energy and the Lemaitre equivalent strain assumption. Then, the influence of thermal damage on the mechanical property is considered.

Effects of three-phase-lag on two-temperature generalized thermoelasticity for infinite medium with spherical cavity

S. BANIK;M. KANORIA

2012, 33(4):  483-498.  doi:10.1007/s10483-012-1565-8

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The thermoelastic interaction for the three-phase-lag (TPL) heat equation in an isotropic infinite elastic body with a spherical cavity is studied by two-temperature generalized thermoelasticity theory (2TT). The heat conduction equation in the theory of TPL is a hyperbolic partial differential equation with a fourth-order derivative with respect to time. The medium is assumed to be initially quiescent. By the Laplace transformation, the fundamental equations are expressed in the form of a vector-matrix differential equation, which is solved by a state-space approach. The general solution obtained is applied to a specific problem, when the boundary of the cavity is subjected to the thermal loading (the thermal shock and the ramp-type heating) and the mechanical loading. The inversion of the Laplace transform is carried out by the Fourier series expansion techniques. The numerical values of the physical quantity are computed for the copper like material. Significant dissimilarities between two models (the two-temperature Green-Naghdi theory with energy dissipation (2TGN-III) and two-temperature TPL model (2T3phase)) are shown graphically. The effects of two-temperature and ramping parameters are also studied.

Research on 1:2 subharmonic resonance and bifurcation of nonlinear rotor-seal system

李忠刚;陈予恕

2012, 33(4):  499-510.  doi:10.1007/s10483-012-1566-7

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The 1:2 subharmonic resonance of the labyrinth seals-rotor system is investigated, where the low-frequency vibration of steam turbines can be caused by the gas exciting force. The empirical parameters of gas exciting force of the Muszynska model are obtained by using the results of computational fluid dynamics (CFD). Based on the multiple scale method, the 1:2 subharmonic resonance response of the dynamic system is gained by truncating the system with three orders. The transition sets and the local bifurcations diagrams of the dynamics system are presented by employing the singular theory analysis. Meanwhile, the existence conditions of subharmonic resonance non-zero solutions of the dynamic system are obtained, which provides a new theoretical basis in recognizing and protecting the rotor from the subharmonic resonant failure in the turbine machinery.

Asymptotic behaviors of solutions for dissipative quantum Zakharov equations

郭艳凤;郭柏灵;李栋龙

2012, 33(4):  511-524.  doi:10.1007/s10483-012-1567-8

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The dissipative quantum Zakharov equations are mainly studied. The existence and uniqueness of the solutions for the dissipative quantum Zakharov equations are proved by the standard Galerkin approximation method on the basis of a priori estimate. Meanwhile, the asymptotic behavior of solutions and the global attractor which is constructed in the energy space equipped with the weak topology are also investigated.

Degenerate scale problem in antiplane elasticity or Laplace equation for contour shapes of triangles or quadrilaterals

陈宜周

2012, 33(4):  525-538.  doi:10.1007/s10483-012-1568-9

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This paper provides several solutions to the degenerate scale for the shapes of triangles or quadrilaterals in an exterior boundary value problem (BVP) of the antiplane elasticity or the Laplace equation. The Schwarz-Christoffel mapping is used throughout. It is found that a complex potential with a simple form in the mapping plane satisfies the vanishing displacement condition (or w=0) along the boundary of the unit circle when the dimension R reaches its critical value 1. This means that the degenerate size in the physical plane is also achieved. The degenerate scales can be evaluated from the particular integrals depending on certain parameters in the mapping function. The numerical results of degenerate sizes for the shapes of triangles or quadrilaterals are provided.