Marco La Mantia¹, Peter Dabnichki^1,2

CMES-Computer Modeling in Engineering & Sciences, Vol.33, No.2, pp. 131-154, 2008, DOI:10.3970/cmes.2008.033.131

Abstract A potential flow based boundary element method was devised to obtain the hydrodynamic forces acting on oscillating wings. A new formulation of the unsteady Kutta condition, postulating a finite pressure difference at the trailing edge of the flapping wing and proposed earlier by the authors, is implemented in the numerical procedure. A comparison with published experimental data (Read et al., 2003) is carried out and the three-dimensional computational results showed good agreement, especially if compared with a similar two-dimensional numerical approach (La Mantia and Dabnichki, 2008) and the potential analytical model of Garrick (1936). The More >

Hossein M. Shodja^1,2,3, Alireza Hashemian^1,4

CMES-Computer Modeling in Engineering & Sciences, Vol.32, No.1, pp. 17-34, 2008, DOI:10.3970/cmes.2008.032.017

Abstract Gradient reproducing kernel particle method (GRKPM) is a meshless technique which incorporates the first gradients of the function into the reproducing equation of RKPM. Therefore, in two-dimensional space GRKPM introduces three types of shape functions rather than one. The robustness of GRKPM's shape functions is established by reconstruction of a third-order polynomial. To enforce the essential boundary conditions (EBCs), GRKPM's shape functions are modified by transformation technique. By utilizing the modified shape functions, the weak form of the nonlinear evolutionary Buckley-Leverett (BL) equation is discretized in space, rendering a system of nonlinear ordinary differential equations More >

Shih-Kai Chien¹, Tzu-Hsiang Yen¹, Yue-Tzu Yang¹, Chao-Kuang Chen^1,2

CMES-Computer Modeling in Engineering & Sciences, Vol.29, No.3, pp. 163-174, 2008, DOI:10.3970/cmes.2008.029.163

Abstract Conventional proton exchange membrane fuel cells (PEMFCs) have a straight gas flow serpentine channel, and hence the reactant gases are transferred to the catalyst layers as a result of diffusion alone. Since the diffusion process is inherently slow, the electrical performance of such PEMFCs is inevitably limited. In an attempt to improve the PEMFC performance, this study replaces the straight channel with containing different type of obstacles and conducts a series of lattice Boltzmann method simulations to investigate the flow field phenomena induced in a viscous liquid as it flows along the serpentine channel at… More >

M. Haji Mohammadi¹

CMES-Computer Modeling in Engineering & Sciences, Vol.29, No.2, pp. 75-94, 2008, DOI:10.3970/cmes.2008.029.075

Abstract In this paper, the truly Meshless Local Petrov-Galerkin (MLPG) method is extended for computation of steady incompressible flows, governed by the Navier--Stokes equations (NSE), in vorticity-stream function formulation. The present method is a truly meshless method based on only a number of randomly located nodes. The formulation is based on two equations including stream function Poisson equation and vorticity advection-dispersion-reaction equation (ADRE). The meshless method is based on a local weighted residual method with the Heaviside step function and quartic spline as the test functions respectively over a local subdomain. Radial basis functions (RBF) interpolation… More >

Sanjay Mittal¹

CMES-Computer Modeling in Engineering & Sciences, Vol.27, No.1&2, pp. 63-78, 2008, DOI:10.3970/cmes.2008.027.063

Abstract Flow past a circular cylinder looses stability at a Reynolds number,Re~47. It has been shown, in the past, that the linear stability analysis (LSA) of the steady state solution can predict not only the critical Re, but also the non-dimensional frequency, St, of the associated instability. For larger Re the non-linear effects become important and the LSA of the steady-state flow does not predict the correct St. It is shown that, in general, the LSA applied to the time-averaged flow can result in useful information regarding its stability. This idea is applied to the Re = 100 flow past More >

G. Kosec¹, B. Šarler¹

CMES-Computer Modeling in Engineering & Sciences, Vol.25, No.3, pp. 197-208, 2008, DOI:10.3970/cmes.2008.025.197

Abstract This paper explores the application of the mesh-free Local Radial Basis Function Collocation Method (LRBFCM) in solution of coupled heat transfer and fluid flow problems in Darcy porous media. The involved temperature, velocity and pressure fields are represented on overlapping 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 energy and momentum equations are solved through explicit time stepping. The pressure-velocity coupling is calculated iteratively, with pressure correction, predicted from the local continuity equation violation.… More >

A. Sellier¹

CMES-Computer Modeling in Engineering & Sciences, Vol.25, No.3, pp. 165-180, 2008, DOI:10.3970/cmes.2008.025.165

Abstract The slow viscous and either imposed or gravity-driven migration of a solid arbitrarily-shaped particle suspended in a Newtonian liquid bounded by a spherical cavity is calculated using two different boundary element approaches. Each advocated method appeals to a few boundary-integral equations and, by contrast with previous works, also holds for non-spherical particles. The first procedure puts usual free-space Stokeslets on both the cavity and particle surfaces whilst the second one solely spreads specific Stokeslets obtained elsewhere in Oseen (1927) on the particle's boundary. Each approach receives a numerical implementation which is found to be in More >

Wenzhong Tang¹, Suresh G. Advani¹

CMES-Computer Modeling in Engineering & Sciences, Vol.25, No.3, pp. 149-164, 2008, DOI:10.3970/cmes.2008.025.149

Abstract In this paper, a method for studying nanotube dynamics in simple shear flow was developed. A nanotube was described as a flexible fiber with a sphere-chain model. The forces on the nanotube were obtained by molecular dynamics simulations. The motion of the nanotube in simple shear flow was tracked by the flexible fiber dynamics method [Tang and Advani (2005)]. The viscosity of dilute nanotube suspensions was calculated based on the nanotube dynamics, and the effects of the aspect ratio and initial curvature of the nanotube on suspension viscosity are explored and discussed. More >

C. Moulinec¹, R. Issa², J.-C. Marongiu³, D. Violeau⁴

CMES-Computer Modeling in Engineering & Sciences, Vol.25, No.3, pp. 133-148, 2008, DOI:10.3970/cmes.2008.025.133

Abstract The gridless Smoothed Particle Hydrodynamics (SPH) numerical method is preferably used in Computational Fluid Dynamics (CFD) to simulate complex flows with one or several convoluted free surfaces. This type of flows requires distorted meshes with classical Eulerian mesh-based methods or very fine meshes with Volume of Fluid method. Few 3-D SPH simulations have been carried out to our knowlegde so far, mainly due to prohibitive computational investment since the number of particles required in 3-D is usually too large to be handled by a single processor. In this paper, a parallel 3-D SPH code is More >

Y.Y. Shan¹, C. Shu^1,2, Z.L. Lu³

CMES-Computer Modeling in Engineering & Sciences, Vol.25, No.2, pp. 99-114, 2008, DOI:10.3970/cmes.2008.025.099

Abstract The local multiquadric-based differential quadrature (MQ-DQ) method proposed by [Shu, Ding, and Yeo (2003)] is a natural mesh-free approach for derivative approximation, which is easy to be implemented to solve problems with curved boundary. Previously, it has been well tested for the two-dimensional (2D) case. In this work, this mesh-free method was extended to simulate fluid flow problems with curved boundary in three-dimensional (3D) space. The main concern of this work is to numerically study the performance of the 3D local MQ-DQ method and demonstrate its capability and flexibility for simulation of 3D incompressible fluid More >