F. Wang¹, J.L. Li¹, B.X. Yang¹, N.A. Hill²

CMES-Computer Modeling in Engineering & Sciences, Vol.95, No.1, pp. 59-85, 2013, DOI:10.3970/cmes.2013.095.059

Abstract A gas-liquid two-phase model for the simulation of a power-law fluid mold filling process with the consideration of phase change is proposed, in which the governing equations for the melt and air in the cavity, including the mass conservation, momentum conservation and energy conservation equations, are unified into one system of equation. A revised Enthalpy method, which can be used for both the melt and air in the mold cavity, is proposed to describe the phase change during the mold filling. Finite volume method on non-staggered grid is used to solve the system. The level More >

K. Luo¹, Y. L. Pi¹, W. Gao¹, M. A. Bradford¹

CMES-Computer Modeling in Engineering & Sciences, Vol.95, No.1, pp. 31-58, 2013, DOI:10.3970/cmes.2013.095.031

Abstract This paper presents a theoretical analysis for the time-dependent nonlinear behaviour and buckling of shallow concrete-filled steel tubular (CFST) arches under a sustained central concentrated load. The virtual work method is used to establish the differential equations of equilibrium for the time-dependent behaviour and buckling analyses of shallow CFST arches, and the age-adjusted effective modulus method is adopted to model the creep behaviour of the concrete core. Analytical solutions of time-dependent displacements and internal forces of shallow CFST arches are derived. It has been found that under a sustained central concentrated load, the deformations and… More >

Seyed Mahmoud Hosseini ¹

CMES-Computer Modeling in Engineering & Sciences, Vol.95, No.1, pp. 1-29, 2013, DOI:10.3970/cmes.2013.095.001

Abstract In this article, the effects of carbon nanotubes distributions on natural frequency are studied for a functionally graded nanocomposite thick hollow cylinder reinforced by single-walled carbon nanotubes using a hybrid mesh-free method. The FG nanocomposite cylinder is excited by a shock loading, which is applied on the inner surface of cylinder. The first natural frequency is obtained for various nonlinear grading patterns of distributions of the aligned carbon nanotubes. The effects of various nonlinear grading patterns on natural frequency are obtained and discussed in details. The presented hybrid mesh-free method is based on the generalized More >

H. Yoshikawa¹, R. Matsuura², N. Nishimura¹

CMES-Computer Modeling in Engineering & Sciences, Vol.94, No.6, pp. 553-565, 2013, DOI:10.3970/cmes.2013.094.553

Abstract The convolution integrals with respect to time in the time domain boundary integral equation method (TD-BIEM) are calculated approximately using the Lubich convolution quadrature method (CQM). The influence matrices in the discretized boundary integral equation are computed with the Laplace transform of the fundamental solution in TD-BIEM with the Lubich CQM. These matrices, however, are dense, and both the computational cost and memory requirements are high. In this paper, we apply Adaptive Cross Approximation (ACA) to the influence matrices to achieve a fast solver of TD-BIEM with the Lubich CQM. Moreover, we reduce the computational More >

Hongtao Wang^1,2, Haitao Wang², Lie Jin², Zhenhan Yao³

CMES-Computer Modeling in Engineering & Sciences, Vol.94, No.6, pp. 529-552, 2013, DOI:10.3970/cmes.2013.094.529

Abstract Since only the boundary of the analyzed domain needs to be discretized, the boundary element method (BEM) inherently has the advantages of solving crack problems. In this paper, a micromechanics BEM scheme is applied to determine the effective elastic moduli of three-dimensional (3-D) solids containing a large number of parallel or randomly oriented microcracks. The 3-D analyses accelerated by the fast multipole method were carried out to investigate the relations between the effective elastic moduli and the microcrack density parameter. Numerical examples show that the results agree well with the available analytical solution and known More >

Haitao Wang^1,2, Zhenhan Yao³

CMES-Computer Modeling in Engineering & Sciences, Vol.94, No.6, pp. 507-527, 2013, DOI:10.3970/cmes.2013.094.507

Abstract This paper presents the use of a three-dimensional time domain boundary element method (BEM) in conjunction with adaptive cross approximation method (ACA) for dynamic analyses of the HTR-PM nuclear island foundation. The advantage of this approach is that only foundation of the HTR-PM nuclear island and limited surfaces of the supporting half-space soil medium are modeled and analyzed in a direct time stepping scheme. In addition, the ACA can compress the BEM coefficient matrices at each time step efficiently, therefore allowing larger models to be analyzed compared with conventional BEMs. In order to discretize the More >

J. Lin¹, W. Chen^1,2, C. S. Chen³, X. R. Jiang⁴

CMES-Computer Modeling in Engineering & Sciences, Vol.94, No.6, pp. 485-505, 2013, DOI:10.3970/cmes.2013.094.485

Abstract To alleviate the difficulty of dense matrices resulting from the boundary knot method, the concept of the circulant matrix has been introduced to solve axi-symmetric Helmholtz problems. By placing the collocation points in a circular form on the surface of the boundary, the resulting matrix of the BKM has the block structure of a circulant matrix, which can be decomposed into a series of smaller matrices and solved efficiently. In particular, for the Helmholtz equation with high wave number, a large number of collocation points is required to achieve desired accuracy. In this paper, we More >

L.L. Chen¹, H.B. Chen², C.J. Zheng³

CMES-Computer Modeling in Engineering & Sciences, Vol.94, No.6, pp. 459-483, 2013, DOI:10.3970/cmes.2013.094.459

Abstract A coupling algorithm based on the finite element method and the wideband fast multipole boundary element method (FEM/wideband FMBEM) is proposed for the simulation of fluid-structure interaction and structural-acoustic sensitivity analysis using the direct differentiation method. The wideband fast multipole method (FMM) formed by combining the original FMM and the diagonal form FMM is used to accelerate the matrix-vector products in the boundary element analysis. The iterative solver GMRES is applied to accelerate the solution of the linear system of equations. The FEM/Wideband FMBEM algorithm makes it possible to predict the effects of arbitrarily shaped More >

E. Viola¹, F. Tornabene¹, E. Ferretti¹, N. Fantuzzi¹

CMES-Computer Modeling in Engineering & Sciences, Vol.94, No.5, pp. 421-458, 2013, DOI:10.3970/cmes.2013.094.421

Abstract In this paper, an advanced version of the classic GDQ method, called the Generalized Differential Quadrature Finite Element Method (GDQFEM) is formulated to solve plate elastic problems with inclusions. The GDQFEM is compared with Cell Method (CM) and Finite Element Method (FEM). In particular, stress and strain results at fiber/matrix interface of dissimilar materials are provided. The GDQFEM is based on the classic Generalized Differential Quadrature (GDQ) technique that is applied upon each sub-domain, or element, into which the problem domain is divided. When the physical domain is not regular, the mapping technique is used… More >

C. Delprete¹, F. Freschi², M. Repetto², C. Rosso¹

CMES-Computer Modeling in Engineering & Sciences, Vol.94, No.5, pp. 397-420, 2013, DOI:10.3970/cmes.2013.094.397

Abstract The growing necessity of accuracy in analyzing engineering problems requires more detailed and sophisticated models. Those models can include multiphysics interactions, that, sometimes, are highly nonlinear and the application of the superposition principle is then not possible. The cell method can be suitably used to study nonlinear multiphysics problems, because its theoretical framework for the physical laws is intrinsically multiphysics. In this way it is possible to take into account the mutual effects between different physics. Within the cell method framework, the coupling terms can be directly formulated in terms of the global variables used More >