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2015年 第36卷 第1期    刊出日期：2015-01-01

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论文

Scale effects on nonlocal buckling analysis of bilayer composite plates under non-uniform uniaxial loads

Xiang-wu PENG;Xing-ming GUO;Liang LIU;Bing-jie WU

2015, 36(1):  1-10.  doi:10.1007/s10483-015-1900-7

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Scale effects are studied on the buckling behavior of bilayer composite plates under non-uniform uniaxial compression via the nonlocal theory. Each isotropic plate is composed of a material that is different from others, and the adhesive between the plates is modeled as the Winkler elastic medium. According to the symmetry, effects of the Winkler non-dimensional parameter, the thickness ratio, the ratio of Young's moduli, and the aspect ratio are also considered on the buckling problem of bilayer plates, where only the top plate is under the uniaxial compression. Numerical examples show that the Winkler elastic coefficient, the thickness ratio, and the ratio of Young's moduli play decisive roles in the buckling behavior. Nonlocal effect is significant when the high-order buckling mode occurs or the aspect ratio is small.



Reflection and transmission of plane waves from fluid-piezothermoelastic solid interface

A. K. VASHISHTH;H. SUKHIJA

2015, 36(1):  11-36.  doi:10.1007/s10483-015-1892-9

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The reflection and transmission of plane waves from a fluid-piezothermoelastic solid interface are studied. The expressions for amplitude ratios and energy ratios corresponding to reflected waves and transmitted waves are derived analytically. The piezo-thermoelastic solid half-space is assumed to have 6mm type symmetry and assumed to be loaded with water. The effects of angle of the incidence, the frequency, the specific heat, the relaxation time, and the thermal conductivity on the reflected and transmitted energy ratios are studied numerically for a particular model of cadmium selenide (CdSe) and water. Some special cases are also studied.

Effects of microstructure on uniaxial strength asymmetry of open-cell foams

Zi-xing LU;Ji-xiang HUANG;Ze-shuai YUAN

2015, 36(1):  37-46.  doi:10.1007/s10483-015-1893-9

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Based on the elongated Kelvin model, the effect of microstructure on the uniaxial strength asymmetry of open-cell foams is investigated. The results indicate that this asymmetry depends on the relative density, the solid material, the cell morphology, and the strut geometry of open-cell foams. Even though the solid material has the same tensile and compressive strength, the tensile and compressive strength of open-cell foams with asymmetrical sectional struts are still different. In addition, with the increasing degree of anisotropy, the uniaxial strength as well as the strength asymmetry increases in the rise direction but reduces in the transverse direction. Moreover, the plastic collapse ratio between two directions is verified to depend mainly on the cell morphology. The predicted results are compared with Gibson and Ashby's theoretical results as well as the experimental data reported in the literature, which validates that the elongated Kelvin model is accurate in explaining the strength asymmetry presented in realistic open-cell foams.

Three-dimensional mixed convection squeezing flow

T. HAYAT;A. QAYYUM;A. ALSAEDI

2015, 36(1):  47-60.  doi:10.1007/s10483-015-1894-9

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The unsteady mixed convection squeezing flow of an incompressible Newtonian fluid between two vertical parallel planes is discussed. The fluid is electrically conducting. The governing equations are transformed into ordinary differential equations (ODEs) by appropriate transformations. The transformed equations are solved successfully by a modern and powerful technique. The effects of the emerging parameters on the flow and heat transfer characteristics are studied and examined. The values of the skin friction coefficient and the local Nusselt number are tabulated and analyzed.

Newtonian heating in stagnation point flow of Burgers fluid

T. HAYAT;S. ALI;M. AWAIS;M. S. ALHUTHALI

2015, 36(1):  61-68.  doi:10.1007/s10483-015-1895-9

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The Newtonian heating effects in the stagnation point flow of a Burgers fluid are addressed in this paper. The boundary layer flow problems are stated in the spatial domain from zero to infinity. The solution expressions for the velocity and the temperature are obtained and examined for the influential variables. The tabulated values show comparison with the previous results. It is observed that the obtained results are in good agreement with the existing results in limiting sense.

Flow of Oldroyd-B fluid with nanoparticles and thermal radiation

T. HAYAT;T. HUSSAIN;S. A. SHEHZAD;A. ALSAEDI

2015, 36(1):  69-80.  doi:10.1007/s10483-015-1896-9

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The two-dimensional boundary layer flow of an Oldroyd-B fluid in the presence of nanoparticles is investigated. Convective heat and mass conditions are considered in the presence of thermal radiation and heat generation. The Brownian motion and thermophoresis effects are retained. The nonlinear partial differential equations are reduced into the ordinary differential equation (ODE) systems. The resulting ODE systems are solved for the series solutions. The results are analyzed for various physical parameters of interest. Numerical values of the local Nusselt and Sherwood numbers are also computed and analyzed.

Flow pattern analysis of linear gradient flow distribution

Da-ming LI;Xiao-yu LI;Yan-qing LI;R. J. FARAHANI

2015, 36(1):  81-106.  doi:10.1007/s10483-015-1920-9

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This paper uses the Oseen transformation to solve the differential equations governing motion of the vertical linear gradient flow distribution close to a wall surface. The Navier-Stokes equations are used to consider the inertia term along the flow direction. A novel contour integral method is used to solve the complex Airy function. The boundary conditions of linear gradient flow distribution for finite problems are determined. The vorticity function, the pressure function, and the turbulent velocity profiles are provided, and the stability of particle trajectories is studied. An L_x-function form of the third derivative circulation is used to to simplify the solution. Theoretical results are compared with the experimental measurements with satisfactory agreement.

Analytical solution of velocity distribution for flow through submerged large deflection flexible vegetation

Wei-jie WANG;Wen-xin HUAI;Yu-hong ZENG;Ji-fu ZHOU

2015, 36(1):  107-120.  doi:10.1007/s10483-015-1897-9

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An analytical solution for predicting the vertical distribution of streamwise mean velocity in an open channel flow with submerged flexible vegetation is proposed when large bending occurs. The flow regime is separated into two horizontal layers: a vegetation layer and a free water layer. In the vegetation layer, a mechanical analysis for the flexible vegetation is conducted, and an approximately linear relationship between the drag force of bending vegetation and the streamwise mean flow velocity is observed in the case of large deflection, which differes significantly from the case of rigid upright vegetation. Based on the theoretical analysis, a linear streamwise drag force-mean flow velocity expression in the momentum equation is derived, and an analytical solution is obtained. For the free water layer, a new expression is presented, replacing the traditional logarithmic velocity distribution, to obtain a zero velocity gradient at the water surface. Finally, the analytical predictions are compared with published experimental data, and the good agreement demonstrates that this model is effective for the open channel flow through the large deflection flexible vegetation.

Applications of scale-adaptive simulation technique based on one-equation turbulence model

Chang-yue XU;Tao ZHOU;Cong-lei WANG;Jian-hong SUN

2015, 36(1):  121-130.  doi:10.1007/s10483-015-1898-9

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A modified scale-adaptive simulation (SAS) technique based on the Spalart-Allmaras (SA) model is proposed. To clarify its capability in prediction of the complex turbulent flow, two typical cases are carried out, i.e., the subcritical flow past a circular cylinder and the transonic flow over a hemisphere cylinder. For comparison, the same cases are calculated by the detached-eddy simulation (DES), the delayed-detached eddy simulation (DDES), and the XY-SAS approaches. Some typical results including the mean pressure coefficient, velocity, and Reynolds stress profiles are obtained and compared with the experiments. Extensive calculations show that the proposed SAS technique can give better prediction of the massively separated flow and shock/turbulent-boundary-layer interaction than the DES and DDES methods. Furthermore, by the comparison of the XY-SAS model with the present SAS model, some improvements can be obtained.

Recent advances of computational aeroacoustics

Xiao-dong LI;Min JIANG;Jun-hui GAO;Da-kai LIN;Li LIU;Xiao-yan LI

2015, 36(1):  131-140.  doi:10.1007/s10483-015-1899-9

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Computational aeroacoustics (CAA) is an interdiscipline of aeroacoustics and computational fluid dynamics (CFD) for the investigation of sound generation and propagation from various aeroacoustics problems. In this review, the foundation and research scope of CAA are introduced firstly. A review of the early advances and applications of CAA is then briefly surveyed, focusing on two key issues, namely, high order finite difference scheme and non-reflecting boundary condition. Furthermore, the advances of CAA during the past five years are highlighted. Finally, the future prospective of CAA is briefly discussed.