T. Matsumoto¹, T. Yamada¹, T. Takahashi¹, C.J. Zheng², S. Harada¹

CMES-Computer Modeling in Engineering & Sciences, Vol.78, No.2, pp. 77-94, 2011, DOI:10.3970/cmes.2011.078.077

Abstract Shape design and topology sensitivity formulations for acoustic problems based on adjoint method and the boundary element method are presented and are applied to shape sensitivity analysis and topology optimization of acoustic field. The objective function is assumed to consist only of boundary integrals and quantities defined at certain number of discrete points. The adjoint field is defined so that the sensitivity of the objective function does not include the unknown sensitivity coefficients of the sound pressures and particle velocities on the boundary and in the domain. Since the final sensitivity expression does not have More >

P. Maghoul¹, B. Gatmiri^1,2, D. Duhamel¹

CMES-Computer Modeling in Engineering & Sciences, Vol.78, No.1, pp. 51-76, 2011, DOI:10.3970/cmes.2011.078.051

Abstract This paper aims at obtaining boundary integral formulations as well as three dimensional(3D) fundamental solutions for unsaturated soils under dynamic loadings for the first time. The boundary integral equations are derived via the use of the weighted residuals method in a way that permits an easy discretization and implementation in a Boundary Element code. Also, the associated 3D fundamental solutions for such deformable porous medium are derived in Laplace transform domain using the method of Hérmander. The derived results are verified analytically by comparison with the previously introduced corresponding fundamental solutions in elastodynamic limiting case. More >

A. Sellier, N. Ghalia

CMES-Computer Modeling in Engineering & Sciences, Vol.78, No.1, pp. 25-50, 2011, DOI:10.3970/cmes.2011.078.025

Abstract The Green tensor complying with anisotropic slip conditions at the surface of a plane, impermeable, motionless and slipping wall is theoretically obtained and an efficient numerical method is proposed to accurately compute at a very reasonable cpu time cost each of its Cartesian component. The accuracy of the advocated numerical strategy is tested against the Maple Software and the employed procedure makes it possible to calculate the Green tensor for a non-isotropic slip condition at a cpu time cost comparable with the one needed for the less complicated isotropic Navier condition. More >

A. Brancati¹, M. H. Aliabadi¹, A. Milazzo²

CMES-Computer Modeling in Engineering & Sciences, Vol.78, No.1, pp. 1-24, 2011, DOI:10.3970/cmes.2011.078.001

Abstract This paper presents an improved adaptive cross approximation (ACA) approach developed in conjunction with the Hierarchical format matrix and the GMRES solver. A novel scheme to generate the cluster tree (based upon preliminary considerations of the prescribed boundary conditions) and an improved ACA algorithm (approximating the system matrix for mixed Robin conditions) are described. The asymptotic smoothness property of a kernel generated by a linear combination of two asymptotic smooth kernels is demonstrated. Numerical results show the new approach to be up to 50% faster than the conventional ACA approach. More >

H.F.Qiang¹, F.Z.Chen¹, W.R. Gao¹

CMES-Computer Modeling in Engineering & Sciences, Vol.77, No.3&4, pp. 239-262, 2011, DOI:10.3970/cmes.2011.077.239

Abstract Based on smoothed particle hydrodynamics (SPH) method with surface tension proposed by Morris, this paper is intended to modify equations for surface tension by modifying normal and curvature with corrective smoothing particle method (CSPM). Compared with the continuum surface force (CSF) model for surface tension employed in the traditional SPH method, the accuracy in the present paper is much higher in terms of handling the problems with large deformation and surface tension. The reason is that in the traditional SPH method the deficiency of particles is near the boundary and sharp-angled areas, and it causes… More >

Y.C. Cai^1,2,3, L.G. Tian¹, S.N. Atluri³

CMES-Computer Modeling in Engineering & Sciences, Vol.77, No.3&4, pp. 221-238, 2011, DOI:10.3970/cmes.2011.077.221

Abstract A new three node triangular plate element, labeled here as DST-S6 (Discrete Shear Triangular element with 6 extra Shear degrees of freedom), is proposed for the analyses of plate/shell structures comprising of thin or thick members. The formulation is based on the DKT (Discrete Kirchhoff Technique) and an appropriate use of the independent shear DOF(Degrees Of Freedom). The shear locking is completely eliminated in the DST-S6, without any numerical expediencies such as the reduce integration, the use of assumed strains/stresses, or the need for the stabilization of the attendant zero energy modes. It is shown… More >

V. Ungvichian¹, P. Kanongchaiyos¹

CMES-Computer Modeling in Engineering & Sciences, Vol.77, No.3&4, pp. 201-220, 2011, DOI:10.3970/cmes.2011.077.201

Abstract This paper describes an enhancement to Garland and Heckbert's mesh simplification method by using the principal curvatures and directions of each vertex. We calculate the values and directions, before using them to determine the absolute normal curvature in the direction of contraction, and multiplying the curvature with the edge length, the maximum absolute cosine of the angles between the edge and the normals of faces adjacent to either endpoint, and the quadric error of the collapse. We also apply penalties based on compactness and angular and dihedral deviations of the resulting faces. We have implemented… More >

M.Souli¹, F.Erchiqui²

CMES-Computer Modeling in Engineering & Sciences, Vol.77, No.3&4, pp. 183-200, 2011, DOI:10.3970/cmes.2011.077.183

Abstract During the design process of membrane structure to resist to high pressure loading, and the characterization of hyperelastic material, a structure made up of thin rubber undergoes large deformation and rotation under high pressure loading out of high pressurized gas. Until recently, to simulate the inflation of the hyperelastic membrane, a uniform pressure based on thermodynamic model or experimental tests is applied to the structure, as boundary conditions. From a computational time point of view, this approach is very fast, since no computational fluid dynamics is involved in the simulation. However, at the late stage… More >

Minghui Wang¹, Musheng Wei², Shanrui Hu¹

CMES-Computer Modeling in Engineering & Sciences, Vol.77, No.3&4, pp. 173-182, 2011, DOI:10.3970/cmes.2011.077.173

Abstract The mapping from the symmetric solution set to its independent parameter space is studied and an iterative method is proposed for the least-squares minimum-norm symmetric solution of AXB = E. Numerical results are reported that show the efficiency of the proposed methods. More >

Hsin-Ping Chu¹, Cheng-Ying Lo²

CMES-Computer Modeling in Engineering & Sciences, Vol.77, No.3&4, pp. 161-172, 2011, DOI:10.3970/cmes.2011.077.161

Abstract This paper presents the application of the differential transform method to solve strongly nonlinear equations with cubic nonlinearities and self-excitation terms. First, the equations are transformed by the differential transform method into the algebra equations in terms of the transformed functions. Secondly, the higher-order transformed functions are calculated in terms of other lower-order transformed functions through the iterative procedure. Finally, the solutions are approximated by the n-th partial sum of the infinite series obtained by the inverse differential transform. Two strongly nonlinear equations with different coefficients and initial conditions are given as illustrative examples. More >