Z.H.Yao¹

CMES-Computer Modeling in Engineering & Sciences, Vol.50, No.1, pp. 21-46, 2009, DOI:10.3970/cmes.2009.050.021

Abstract The traditional time domain boundary integral equation (TDBIE) of elastodynamics is formulated based on the time dependent fundamental solution and the reciprocal theorem of elastodynamics. The time dependent fundamental solution of the elastodynamics is the response of the infinite elastic medium under a unit concentrate impulsive force subjected at a point and at an instant, including not only the pressure wave and shear wave, but also the Laplace wave with speed between that of P and S waves. In this paper, a new TDBIE is derived directly from the initial boundary value problem of the partial differential equation of elastodynamics,… More >

Yaoming Zhang¹, Yan Gu¹, Jeng-Tzong Chen²

CMES-Computer Modeling in Engineering & Sciences, Vol.50, No.1, pp. 1-20, 2009, DOI:10.3970/cmes.2009.050.001

Abstract There exist nearly singular integrals for thin walled structures in the boundary element method (BEM). In this paper, an efficient analytical method is developed to deal with the nearly singular integrals in the boundary integral equations (BIEs) for 2-D thin walled structures. The developed method is possible for problems defined in high-order geometry elements when the nearly singular integrals need to be calculated. For the analysis of nearly singular integrals with high-order geometry elements, much fewer boundary elements can be used to achieve higher accuracy. More importantly, computational models of thin walled structures or thin shapes in structures demand a… More >

S. Tangaramvong, F. Tin-Loi

CMES-Computer Modeling in Engineering & Sciences, Vol.49, No.3, pp. 269-296, 2009, DOI:10.3970/cmes.2009.049.269

Abstract We consider the optimal synthesis, namely minimum weight design, of rigid perfectly-plastic structures for which some supports involve unilateral frictional contact. This problem is of interest as it is not only encountered in practice but it also involves, in the general friction case, a nonassociative complementarity condition that makes it theoretically and numerically challenging. For simplicity of exposition, we focus on the class of bar structures for which yielding is governed by either pure bending or by combined axial and flexural forces. In view of possible multiplicity of solutions due to nonassociativity, a direct optimization formulation may lead to an… More >

Haiping Ye¹, Yongsheng Ding²

CMES-Computer Modeling in Engineering & Sciences, Vol.49, No.3, pp. 255-268, 2009, DOI:10.3970/cmes.2009.049.255

Abstract A fractional-order model for the immunological and therapeutic control of HIV is studied qualitatively. The equilibria are found and their local stability are investigated. Also the global stability of the infection-free equilibrium is established. The optimal efficacy level of anti-retroviral therapy needed to eradicate HIV from the body of an HIV-infected individual is obtained. More >

Gerardo Anguiano-Orozco^1,2, Rubén Avila³

CMES-Computer Modeling in Engineering & Sciences, Vol.49, No.3, pp. 217-254, 2009, DOI:10.3970/cmes.2009.049.217

Abstract A numerical investigation of the transient, three dimensional, laminar natural convection of a fluid confined in a spherical container is carried out. Initially the fluid is quiescent with a uniform temperature T_i equal to the temperature of the wall of the container. At time t=0, the temperature of the wall is suddenly lowered to a uniform temperature T_w=0. The natural convection, that conducts to a vortex ring formation within the sphere, is driven by a terrestrial gravity force (laboratory gravity) and by the step change in the temperature of the wall. A scaling analysis of a simplified transient, two dimensional… More >

Luca Bergamaschi^1,2, ,Ángeles Martínez², Giorgio Pini²

CMES-Computer Modeling in Engineering & Sciences, Vol.49, No.3, pp. 191-216, 2009, DOI:10.3970/cmes.2009.049.191

Abstract A meshless model, based on the Meshless Local Petrov-Galerkin (MLPG) approach, is developed and implemented in parallel for the solution of axi-symmetric poroelastic problems. The parallel code is based on a concurrent construction of the stiffness matrix by the processors and on a parallel preconditioned iterative method of Krylov type for the solution of the resulting linear system. The performance of the code is investigated on a realistic application concerning the prediction of land subsidence above a deep compacting reservoir. The overall code is shown to obtain a very high parallel efficiency (larger than 78% for the solution phase) and… More >

Ronan Madec¹, Dimitri Komatitsch^1,2, Julien Diaz³

CMES-Computer Modeling in Engineering & Sciences, Vol.49, No.2, pp. 163-190, 2009, DOI:10.3970/cmes.2009.049.163

Abstract When studying seismic wave propagation in fluid-solid models based on a numerical technique in the time domain with an explicit time scheme it is often of interest to resort to time substepping because the stability condition in the solid part of the medium can be more stringent than in the fluid. In such a case, one should enforce the conservation of energy along the fluid-solid interface in the time matching algorithm in order to ensure the accuracy and the stability of the time scheme. This is often not done in the available literature and approximate techniques that do not enforce… More >

K. Han¹, Y. T. Feng¹, D. R. J. Owen¹

CMES-Computer Modeling in Engineering & Sciences, Vol.49, No.2, pp. 143-162, 2009, DOI:10.3970/cmes.2009.049.143

Abstract Motivated by Hottel's crossed-string method, this paper presents an accurate algorithm for the evaluation of the geometric view factors in a randomly packed bed of circular particles of various sizes. The radiative heat exchange can thus be predicted accurately. The solution procedure is illustrated and the solution accuracy is assessed via a numerical example. More >

J.M.C.Pereira¹, N.A.R.Maia¹, J.C.F.Pereira¹

CMES-Computer Modeling in Engineering & Sciences, Vol.49, No.2, pp. 113-142, 2009, DOI:10.3970/cmes.2009.049.113

Abstract We present a 2D incompressible Navier-Stokes numerical simulation of a virtual model of an elliptic, or flat plate, foil in hovering flight configuration. Computations obtained with a general purpose solver were validated against reference data on forward flapping flight, normal or dragonfly hovering. The moving mesh technique allows airfoil translation and angular mesh movement accompaining the airfoil stroke motion. Close to the ground the mesh deforms to occupy the narrow computational domain formed between the airfoil and the ground. Computations have been carried out for some parameters, including the distances h between the foil center and the surface, h/c =… More >

H.Nguyen-Van¹, N.Mai-Duy¹ and T.Tran-Cong¹

CMES-Computer Modeling in Engineering & Sciences, Vol.49, No.2, pp. 81-112, 2009, DOI:10.3970/cmes.2009.049.081

Abstract This paper reports the development of a simple and efficient 4-node flat shell element with six degrees of freedom per node for the analysis of arbitrary shell structures. The element is developed by incorporating a strain smoothing technique into a flat shell finite element approach. The membrane part is formulated by applying the smoothing operation on a quadrilateral membrane element using Allman-type interpolation functions with drilling DOFs. The plate-bending component is established by a combination of the smoothed curvature and the substitute shear strain fields. As a result, the bending and a part of membrane stiffness matrices are computed on… More >