Ying Liu¹, Yufeng Nie², Weiwei Zhang², Lei Wang²

CMES-Computer Modeling in Engineering & Sciences, Vol.55, No.1, pp. 89-110, 2010, DOI:10.3970/cmes.2010.055.089

Abstract In the light of the ideas and treatment technologies about molecular dynamics simulation and bubble meshing, a new approach of node placement for the meshless method called node placement method by bubble simulation (NPBS method), is proposed. Nodes are seen as the centers of the bubbles which can be moved by their interacting forces. Through dynamic simulation, bubbles are placed into a near-optimal configuration, and the centers of bubbles will form a good-quality node distribution in the domain. This process doesn't need updating the mesh connection constantly, i.e., is totally meshfree. Some example results show that the uniform point sets… More >

Z. T. Ma¹, X. Zhang^1,2, P. Huang¹

CMES-Computer Modeling in Engineering & Sciences, Vol.55, No.1, pp. 61-88, 2010, DOI:10.3970/cmes.2010.055.061

Abstract The Material Point Method (MPM) is more expensive in terms of storage than other methods, as MPM makes use of both mesh and particle data. Therefore, it is critical to develop an efficient MPM framework for engineering applications, such as impact and explosive simulations. This paper presents a new architecture for MPM computer code, developed using object-oriented design, which enables MPM analysis of a mass of grains, large deformation, high strain rates and complex material behavior. It is flexible, extendible, and easily modified for a variety of MPM analysis procedures. An MPM scheme combining contact algorithm with USF, USL and… More >

G.S. Li¹, D. Yao², Y.Z. Wang³, H.Y. Jiang²

CMES-Computer Modeling in Engineering & Sciences, Vol.51, No.1, pp. 53-72, 2009, DOI:10.3970/cmes.2009.051.053

Abstract In this paper, an undisturbed soil-column infiltrating experiment is investigated, and a mathematical model describing multi-components solutes transport behaviors in the column is put forward by combing hydro-chemical analysis with advection dispersion mechanisms, which is a group of advection-dispersion-reaction partial differential equations. Since the model involving six reaction coefficients which can not be obtained directly, an optimal perturbation regularization algorithm of determining these parameters is performed, and numerical simulations under different conditions are carried out. Furthermore, the inversion algorithm is applied to solve the real inverse problem by utilizing the measured breakthrough data. The reconstruction data basically coincide with the… More >

Tae-Hyuk Ahn¹, Layne T. Watson^1,2, Yang Cao^1,1, Clifford A. Shaffer¹, William T. Baumann³

CMES-Computer Modeling in Engineering & Sciences, Vol.51, No.1, pp. 27-52, 2009, DOI:10.3970/cmes.2009.051.027

Abstract For biochemical systems, where some chemical species are represented by small numbers of molecules, discrete and stochastic approaches are more appropriate than continuous and deterministic approaches. The continuous deterministic approach using ordinary differential equations is adequate for understanding the average behavior of cells, while the discrete stochastic approach accurately captures noisy events in the growth-division cycle. Since the emergence of the stochastic simulation algorithm (SSA) by Gillespie, alternative algorithms have been developed whose goal is to improve the computational efficiency of the SSA. This paper explains and empirically compares the performance of some of these SSA alternatives on a realistic… More >

A.R. da Silva¹, A. Silveira-Neto^2,3, D.A. Rade^2,4, R.Francis⁴, E.A. Santos⁴

CMES-Computer Modeling in Engineering & Sciences, Vol.50, No.3, pp. 285-304, 2009, DOI:10.3970/cmes.2009.050.285

Abstract In the context of computational fluid dynamics a numerical investigation of incompressible flow around fixed pairs of rigid circular cylinders was carried out. The two-dimensional filtered Navier-Stokes equations with the Smagorinsky sub-grid scale model were solved using a Cartesian non-uniform grid. The immersed Boundary Method with the Virtual Physical Model was used in order to model the presence of two circular cylinders embedded in the flow. The fractional time step method was used to couple pressure and velocity fields. The simulations were carried out for Reynolds number equal to 72,000 for pitch ratio equal to 2 and different arrangements regarding… More >

Chun-Lang Yeh ¹

CMES-Computer Modeling in Engineering & Sciences, Vol.50, No.3, pp. 253-284, 2009, DOI:10.3970/cmes.2009.050.253

Abstract This paper investigates the instability of a liquid thread by molecular dynamics (MD) simulation. The influences of liquid thread radius, fundamental cell length, and temperature are discussed. Snapshots of molecules, number of liquid particles formed, and density field are analyzed. Two linear stability criteria, namely Rayleigh's stability criterion and Kim's stability criterion, are accessed for their validity in molecular scale. It is found that a liquid thread is more unstable and produces more liquid particles in the fundamental cell when it is thinner or at a higher temperature. In addition, a liquid thread with a longer fundamental cell length is… More >

Zone-Ching Lin¹, Jia-Rong Ye²

CMES-Computer Modeling in Engineering & Sciences, Vol.50, No.3, pp. 227-252, 2009, DOI:10.3970/cmes.2009.050.227

Abstract The paper develops a quasi-steady molecular statics model to analyze nanoscale cutting of copper materials by diamond cutters with different shapes. Cutting action, cutting force, equivalent strain and equivalent stress are discussed and compared. The quasi-steady molecular statics nanocutting model first assumes the trajectory of each atom of the copper workpiece being cut whenever the diamond cutter goes forward one step. It then uses the optimization search method to solve the force equilibrium equation of the Morse force in the X and Y directions when each atom moves a small distance, so as to find the new movement position of… More >

M.J. Galán Moreno, J.J. Sánchez Medina, L. Álvarez Álvarez E. Rubio Royo¹

CMES-Computer Modeling in Engineering & Sciences, Vol.50, No.3, pp. 191-226, 2009, DOI:10.3970/cmes.2009.050.191

Abstract Urban traffic is a key factor for the development of a city. There exist many different approaches facing traffic optimization. In our case we have focused on traffic lights optimization. We have designed and tested a new architecture to optimize traffic light cycle times. The purpose of this research is to demonstrate the good performance of our architecture in a congested scenario. We have simulated several congestion situations for a very large real world traffic network - "La Almozara" in Zaragoza, Spain. Our results seem encouraging in this extreme situation. As we increase the load in the network we get… More >

J.C.Campbell¹, R.Vignjevic¹, M.Patel¹, S.Milisavljevic¹

CMES-Computer Modeling in Engineering & Sciences, Vol.49, No.1, pp. 1-22, 2009, DOI:10.3970/cmes.2009.049.001

Abstract This paper presents research towards the development of an analysis technique for predicting the interaction of large ocean waves with ships and offshore structures specifically with respect to the extent of deck submersion, impact loads and the level of structural damage caused. The coupled SPH - Finite Element approach is used, where the water is modeled with SPH and the structure with shell or continuum finite elements. Details of the approach are presented, including the SPH-FE contact and the fluid boundary conditions. Simulation results show that the method can correctly represent the behavior of a floating structure and the structural… 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 >