Peng Weihong¹, Cao Guohua², Dongzhengzhu¹, Li Shuncai³

CMES-Computer Modeling in Engineering & Sciences, Vol.75, No.3&4, pp. 173-188, 2011, DOI:10.3970/cmes.2011.075.173

Abstract Numerical method is applied to investigate the Darcy-Stokes equations, which is governing the steady incompressible Stokes flow past a circular cavity in a porous medium. The free fluid flow is modeled by the incompressible Stokes equations, and the flow in the porous medium is imposed by Darcy equations. Based on domain decomposition method with D-N alternating iteration algorithm, the coupling method of finite difference method and natural boundary element method is studied for the coupling Darcy-Stokes equations under a certain pressure difference. The numerical results indicate that the finite difference and natural boundary element coupling method is efficient and convenient… More >

Kazuhiko Suga^1,2, Takahiko Ito¹

CMES-Computer Modeling in Engineering & Sciences, Vol.75, No.2, pp. 141-172, 2011, DOI:10.3970/cmes.2011.075.141

Abstract The multiple-relaxation-time lattice Boltzmann method for micro-scale flows (MRT µ-flow LBM) is extensively evaluated in this study. Following the study of Chai, Shi, Guo and Lu (2010), the diffusive bounce-back wall boundary condition and the collision matrix are modeled. To determine the model parameters, the first-order, 1.5-order and second-order slip-flow models are discussed. Since the mean free path of gas molecules is considered to be influenced by the wall in micro flow systems, the effects of a correction function after Stops (1970) are also evaluated. As the increase of the Knudsen number (Kn), it is necessary to introduce the regularization… More >

L.Q. Moreira¹, F.P. Mariano², A. Silveira-Neto¹

CMES-Computer Modeling in Engineering & Sciences, Vol.75, No.2, pp. 113-140, 2011, DOI:10.3970/cmes.2011.075.113

Abstract Turbulence in fluid flow is one of the most challenging problems in classical physics. It is a very important research problem because of its numerous implications, such as industrial applications that involve processes using mixtures of components, heat transfer and lubrication and injection of fuel into the combustion chambers and propulsion systems of airplanes. Turbulence in flow presents characteristics that are fully nonlinear and that occur at high Reynolds numbers. Because of the nonlinear nature of turbulent flow, an increase in the Reynolds number implies an increase in the Kolmogorov wave numbers, and the flow spectrum becomes larger in both… More >

B.-H. Lee¹, J.-C. Park², M.-H. Kim³, S.-C. Hwang²

CMES-Computer Modeling in Engineering & Sciences, Vol.75, No.2, pp. 89-112, 2011, DOI:10.3970/cmes.2011.075.089

Abstract The violent free-surface motions and the corresponding impact loads are numerically simulated by using the refined Moving Particle Simulation (MPS) method, which was originally proposed by Koshizuka and Oka (1996) for incompressible flows. In the present method, accuracy and efficiency are significantly improved compared to the original MPS method by using optimal source term, optimal gradient and collision models, and improved solid-boundary treatment and search of free-surface particles. The refined MPS method was verified through comparisons against Kishev et al.'s (2006) sloshing experiment. It is also demonstrated that the refined MPS method is excellent in mass conservation regardless of length… More >

Mohsen Sadeghbeigi Olyaie¹, Mohammad Reza Razfar², Edward J. Kansa³

CMES-Computer Modeling in Engineering & Sciences, Vol.75, No.1, pp. 43-88, 2011, DOI:10.3970/cmes.2011.075.043

Abstract This paper presents integration of reliability analysis with topology optimization design for a linear mircroactuator, including multitude cantilever piezoelectric bimorphs. Each microbimoph in the mechanism can be actuated in both axial and flexural modes simultaneously. We consider quasi-static and linear conditions, and the smoothed finite element method (S-FEM) is employed in the analysis of piezoelectric effects. Since microfabrication methods are used for manufacturing this type of actuator, uncertainty variables become very important. Hence, these variables are considered as constraints during our topology optimization design process and reliability based topology optimization (RBTO) is conducted. To avoid the overly-stiff behavior in FEM… More >

Ali Bekir Yildiz¹

CMES-Computer Modeling in Engineering & Sciences, Vol.75, No.1, pp. 33-42, 2011, DOI:10.3970/cmes.2011.075.033

Abstract The generalized method for determination of time constants of linear circuits is introduced. Nodal and mesh analysis, conventional methods whose applications are simpler than the state-space formulation, are used in obtaining the system equations. The approach is based on the use of the relationship between transfer functions and system equations of linear circuits, obtained by the conventional methods. The examples of active and passive circuits are given to illustrate the method. More >

F. Tan^1,2, Y.L. Zhang¹, Y.H. Wang³, Y. Miao³

CMES-Computer Modeling in Engineering & Sciences, Vol.75, No.1, pp. 1-32, 2011, DOI:10.3970/cmes.2011.075.001

Abstract The meshless hybrid boundary node method (HBNM) for solving the bending problem of the Kirchhoff thin plate is presented and discussed in the present paper. In this method, the solution is divided into two parts, i.e. the complementary solution and the particular solution. The particular solution is approximated by the radial basis function (RBF) via dual reciprocity method (DRM), while the complementary one is solved by means of HBNM. The discrete equations of HBNM are obtained from a variational principle using a modified hybrid functional, in which the independent variables are the generalized displacements and generalized tractions on the boundary… More >

Francesca Cosmi¹

CMES-Computer Modeling in Engineering & Sciences, Vol.74, No.3&4, pp. 269-282, 2011, DOI:10.3970/cmes.2011.074.269

Abstract In industrial applications, microstructure inhomogeneities can derive from the manufacturing process and the final mechanical properties of the material depend on the resulting, complex, structural pattern of the constituents. In this paper, Cell Method plane models in the elastic and plastic fields are presented and applied to predict the behaviour of four sintered alloys, where the spatial arrangement of voids within the base material contributes to determine the mechanical behaviour. Unlike the Finite Elements and other methods, the Cell Method is a numerical method based on a direct discrete formulation of equilibrium equations, so that no differential formulation is needed… More >

Qiang Li, Jie Ouyang¹, Xuejuan Li², Guorong Wu², Binxin Yang²

CMES-Computer Modeling in Engineering & Sciences, Vol.74, No.3&4, pp. 247-268, 2011, DOI:10.3970/cmes.2011.074.247

Abstract A unified mathematical model is proposed to predict the short shot, primary and secondary gas penetration phenomenon in gas-assisted injection molding (GAIM) process, where the Cross-WLF model and two-domain modified Tait equation are employed to simulate the melt viscosity and density in the whole process, respectively. The governing equations of two-phase flows including gas, air and polymer melt are solved using finite volume method with SIMPLEC technology. At first, two kinds of U-shaped gas channels are modeled, where the shape corner and generous corner cases are studied. At last, as a case study, the short shot, primary and secondary gas… More >

Dan Ma^1,2, Xianbiao Mao¹, Xiexing Miao¹, Shaojie Liu¹

CMES-Computer Modeling in Engineering & Sciences, Vol.74, No.3&4, pp. 233-246, 2011, DOI:10.3970/cmes.2011.074.233

Abstract Rock surrounding the circular roadway with uniform and local support is one of the most common phenomenons in roadway support engineering, which needs to be studied thoroughly at the theoretical level. The existing literatures on stress field function of rock surrounding the roadway is largely restricted to analytical solutions of stress for roadways with a uniform support or no support at all, the corresponding stress solution under conditions of local support has not been provided. Based on the mechanical models of uniform support and local support, the methods of the complex variable function and the complex Fourier series, using the… More >