Kazuhiko Suga^1,2, Takahiko Ito¹

CMES-Computer Modeling in Engineering & Sciences, Vol.63, No.3, pp. 223-242, 2010, DOI:10.3970/cmes.2010.063.223

Abstract Flow passages in micro/nano-electro-mechanical systems (MEMS/ -NEMS) usually have complicated geometries. The present study thus discusses on the latest lattice Boltzmann methods (LBMs) for micro/nano fluidics to evaluate their applicability to micro/nano-flows in complex geometries. Since the flow regime is the continuum to the slip and transitional regime with a moderate Knudsen number (Kn), the LBMs presently focused on feature the wall boundary treatment and the relaxation-time for modeling such flow regimes. The discussed micro flow (µ-flow) LBMs are based on the Bhatnagar-Gross-Krook (BGK) model and the multiple relaxation-time (MRT) model. The presently chosen µ-flow BGK LBM (BGK-1 model) consists… More >

Y. Inoue¹, R. Kobayashi¹, S. Ogata¹, T. Gotoh¹

CMES-Computer Modeling in Engineering & Sciences, Vol.63, No.2, pp. 137-162, 2010, DOI:10.3970/cmes.2010.063.137

Abstract Vibration of a single graphene and a pair of graphenes at micro meter scale induced by air flow is numerically simulated and examined by using a hybrid computational method starting from a microscopic level of description for the graphene. In order to bridge a huge gap in spatial and time scales in their motions, the carbon atoms of the graphene are represented by a small number of coarse grained particles, the fluid motion is described by the lattice Boltzmann equation and the momentum exchange at the boundary is treated by the time averaged immersed boundary method. It is found that… More >

Hao-Chueh Mai¹, Kuen-Hau Lin¹, Cheng-Hsiu Yang¹, Chao-An Lin^1,2

CMES-Computer Modeling in Engineering & Sciences, Vol.61, No.1, pp. 45-62, 2010, DOI:10.3970/cmes.2010.061.045

Abstract A thermal BGK lattice Boltzmann model for flows with viscous heat dissipation is proposed. In this model, the temperature is solved by a separate thermal distribution function, where the equilibrium distribution function is similar to its hydrodynamic counterpart, except that the leading quantity is temperature. The viscous dissipation rate is obtained by computing the second-order moments of non-equilibrium distribution function, which avoids the discretization of the complex gradient term, and can be easily implemented. The proposed thermal lattice Boltzmann model is scrutinized by computing two-dimensional thermal Poiseuille flow, thermal Couette flow, natural convection in a square cavity, and three-dimensional thermal… More >

K. Han¹, Y. T. Feng¹, D. R. J. Owen¹

CMES-Computer Modeling in Engineering & Sciences, Vol.59, No.1, pp. 1-30, 2010, DOI:10.3970/cmes.2010.059.001

Abstract A computational framework is established for effective modelling of fluid-thermal-particle interactions. The numerical procedures comprise the Discrete Element Method for simulating particle dynamics; the Lattice Boltzmann Method for modelling the mass and velocity field of the fluid flow; and the Discrete Thermal Element Method and the Thermal Lattice Boltzmann Method for solving the temperature field. The coupling of the three fields is realised through hydrodynamic interaction force terms. Selected numerical examples are provided to illustrate the applicability of the proposed approach. More >

Hua Li¹, Shantanu S. Mulay¹, Simon See²

CMES-Computer Modeling in Engineering & Sciences, Vol.54, No.2, pp. 147-200, 2009, DOI:10.3970/cmes.2009.054.147

Abstract In this paper, the stability characteristics of a novel strong-form meshless method, called the random differential quadrature (RDQ), are studied using the location of zeros or roots of its characteristic polynomials with respect to unit circle in complex plane by discretizing the domain with the uniform or random field nodes. This is achieved by carrying out the RDQ method stability analysis for the 1st-order wave, transient heat conduction and transverse beam deflection equations using both the analytical and numerical approaches. The RDQ method extends the applicability of the differential quadrature (DQ) method over irregular domain, discretized by randomly or uniformly… More >

Sudib K. Mishra¹, J. K. Paik², S. N. Atluri¹

CMES-Computer Modeling in Engineering & Sciences, Vol.50, No.1, pp. 67-96, 2009, DOI:10.3970/cmes.2009.050.067

Abstract We present a simulation based study, by combining several models involving multiple time scales and physical processes, which govern the interfacial stress corrosion cracking (SCC) in grain boundaries, layered composites or bi-materials, and the mechanisms of inhibition using `smart' agents. The inhibiting agents described herein, automatically sense the initiation of damage, migrate to the sites and delay the corrosion kinetics involved in the process. The phenomenon of SCC is simulated using the lattice spring model (for the mechanical stresses), coupled with a finite difference model of diffusing species, causing the dissolution of the interfacial bonds. The dissolution is expressed through… More >

R. Avila¹, F.J. Solorio¹

CMES-Computer Modeling in Engineering & Sciences, Vol.44, No.2, pp. 177-202, 2009, DOI:10.3970/cmes.2009.044.177

Abstract Heat transfer processes involving phase change either, solidification or melting, appear frequently in nature and in industrial applications. In this paper the convective patterns that arise from a 2D shear driven annular flow (without and with melting), are presented. The convective annular flow with radial gravity can be considered as a simplified model of the atmospheric flow in the terrestrial equatorial plane (bounded by the warm surface of the Earth and the cold tropopause). The governing equations have been numerically solved by the Spectral Element Method. The numerical results reported in this paper, for the cases without melting (at two… More >

Chih-Fung Ho¹, Cheng Chang¹, Kuen-Hau Lin¹, Chao-An Lin^1,2

CMES-Computer Modeling in Engineering & Sciences, Vol.44, No.2, pp. 137-156, 2009, DOI:10.3970/cmes.2009.044.137

Abstract Consistent formulations of 2D and 3D pressure and velocity boundary conditions along both the stationary and non-stationary plane wall and corner for lattice Boltzmann simulations are proposed. The unknown distribution functions are made function of local known distribution functions and correctors, where the correctors at the boundary nodes are obtained directly from the definitions of density and momentum. This boundary condition can be easily implemented on the wall and corner boundary using the same formulation. Discrete macroscopic equation is also derived for steady fully developed channel flow to assess the effect of the boundary condition on the solutions, where the… More >

R. Vertnik¹, B. Šarler²

CMES-Computer Modeling in Engineering & Sciences, Vol.44, No.1, pp. 65-96, 2009, DOI:10.3970/cmes.2009.044.065

Abstract The application of the mesh-free Local Radial Basis Function Collocation Method (LRBFCM) in solution of incompressible turbulent flow is explored in this paper. The turbulent flow equations are described by the low - Re number k-emodel with Jones and Launder [Jones and Launder (1971)] closure coefficients. The involved velocity, pressure, turbulent kinetic energy and dissipation fields are represented on overlapping 5-noded sub-domains through collocation by using multiquadrics Radial Basis Functions (RBF). The involved first and second derivatives of the fields are calculated from the respective derivatives of the RBF's. The velocity, turbulent kinetic energy and dissipation equations are solved through… More >

D. S. Liu¹, C.Y. Tsai¹

CMES-Computer Modeling in Engineering & Sciences, Vol.39, No.1, pp. 29-48, 2009, DOI:10.3970/cmes.2009.039.029

Abstract Utilizing a thin copper substrate for illustration purposes, this study presents a novel numerical method for extracting the thermo-mechanical properties of a thin-film. In the proposed approach, molecular dynamics (MD) simulations are performed to establish the load-displacement response of a thin copper substrate nanoindented at temperatures ranging from 300~1400 K. The load data are then input to an artificial neural network (ANN), trained using a finite element model (FEM), in order to extract the material constants of the copper substrate. The material constants are then used to construct the corresponding stress-strain curve, from which the elastic modulus and the plastic… More >