K. Abe¹, H. Fujii¹, S. Yoshimura¹

CMES-Computer Modeling in Engineering & Sciences, Vol.113, No.1, pp. 71-87, 2017, DOI:10.3970/cmes.2017.113.068

Abstract Microscopic traffic simulations are useful for solving various traffic- related problems, e.g. traffic jams and accidents, local and global environmental and energy problems, maintaining mobility in aging societies, and evacuation plan- ning for natural as well as man-made disasters. The origin-destination (OD) matrix is often used as the input to represent traffic demands into traffic simulators. In this study, we propose an indirect method for estimating the OD matrix using a traffic simulator as an internal model. The proposed method is designed to output results that are consistent with the input of the simulator. The method consists of the following… More >

Mohammad Ilati¹, Mehdi Dehghan²

CMES-Computer Modeling in Engineering & Sciences, Vol.109-110, No.4, pp. 325-360, 2015, DOI:10.3970/cmes.2015.109.325

Abstract In this paper, at first, a new combined shape function is proposed. Then, based on this shape function, the meshless local weak form method is applied to find the numerical solution of time-dependent non-linear Brusselator and Gierer- Meinhardt systems. The combined shape function inherits the properties of radial point interpolation (RPI), moving least squares (MLS) and moving Kriging (MK) shape functions and is controlled by control parameters, which take different values in the domain [0;1]. The combined shape function provides synchronic use of different shape functions and this leads to more flexibility in the used method. The main aim of… More >

Ridha Djebali^1,2, Bernard Pateyron², Mohamed El Ganaoui³

CMES-Computer Modeling in Engineering & Sciences, Vol.88, No.4, pp. 293-308, 2012, DOI:10.3970/cmes.2012.088.293

Abstract We present in this study a numerical investigation of unsteady two-dimensional natural convection of an electrically conducting fluid in a square cavity under an externally imposed magnetic field. A temperature gradient is applied between the two opposing side walls parallel to y-direction, while the floor and ceiling parallel to x-direction are adiabatic. The flow is characterized by the Rayleigh number Ra raged in 103-106, the Prandtl number Pr ranged in 0.01-10, the Hartman number Ha determined by the strength of the imposed magnetic field ranged in 0-100 and its tilting angle from x-axis ranging from 0 to 90 . The… More >

R. Martin¹, D. Komatitsch^1,2, S. D. Gedney³, E. Bruthiaux^1,4

CMES-Computer Modeling in Engineering & Sciences, Vol.56, No.1, pp. 17-42, 2010, DOI:10.3970/cmes.2010.056.017

Abstract Unsplit convolutional perfectly matched layers (CPML) for the velocity and stress formulation of the seismic wave equation are classically computed based on a second-order finite-difference time scheme. However it is often of interest to increase the order of the time-stepping scheme in order to increase the accuracy of the algorithm. This is important for instance in the case of very long simulations. We study how to define and implement a new unsplit non-convolutional PML called the Auxiliary Differential Equation PML (ADE-PML), based on a high-order Runge-Kutta time-stepping scheme and optimized at grazing incidence. We demonstrate that when a second-order time-stepping… More >

Yufeng Nie¹, Ying Liu², Yuantong Gu³, Xiangkuo Fan¹

CMES-Computer Modeling in Engineering & Sciences, Vol.45, No.1, pp. 31-56, 2009, DOI:10.3970/cmes.2009.045.031

Abstract The Node-based Local Mesh Generation (NLMG) algorithm, which is free of mesh inconsistency, is one of core algorithms in the Node-based Local Finite Element Method (NLFEM) to achieve the seamless link between mesh generation and stiffness matrix calculation, and the seamless link helps to improve the parallel efficiency of FEM. Furthermore, the key to ensure the efficiency and reliability of NLMG is to determine the candidate satellite-node set of a central node quickly and accurately. This paper develops a Fast Local Search Method based on Uniform Bucket (FLSMUB) and a Fast Local Search Method based on Multilayer Bucket (FLSMMB), and… More >

Sirajul Haq¹, Siraj-ul-Islam², Arshed Ali³

CMES-Computer Modeling in Engineering & Sciences, Vol.38, No.1, pp. 1-24, 2008, DOI:10.3970/cmes.2008.038.001

Abstract In this paper we propose a meshfree technique for the numerical solution of the modified equal width wave (MEW) equation. Combination of collocation method using the radial basis functions (RBFs) with first order accurate forward difference approximation is employed for obtaining meshfree solution of the problem. Different types of RBFs are used for this purpose. Performance of the proposed method is successfully tested in terms of various error norms. In the case of non-availability of exact solution, performance of the new method is compared with the results obtained from the existing methods. Propagation of a solitary wave, interaction of two… More >

Vadiraja D. N.¹, A. D. Sahasrabudhe²

CMES-Computer Modeling in Engineering & Sciences, Vol.27, No.1&2, pp. 49-62, 2008, DOI:10.3970/cmes.2008.027.049

Abstract Rotating beams are flexible structures, which are often idealized as cantilever beams. Structural modelling of rotating thin-walled composite beam with embedded MFC actuators and sensors using higher shear deformation theory (HSDT) is presented. A non-Cartesian deformation variable (which represents arc length stretch) is used along with two Cartesian deformation variables. The governing system of equations is derived from Hamilton's principle and solution is obtained by extended Galerkin's method. Optimal control problem is solved using LQG control algorithm. Vibration characteristics and optimal control for a box beam configuration are discussed in numerical examples. Gyroscopic coupling between lagging-extension motions is found to… More >

Chein-Shan Liu¹

CMES-Computer Modeling in Engineering & Sciences, Vol.21, No.1, pp. 53-66, 2007, DOI:10.3970/cmes.2007.021.053

Abstract A newly modified Trefftz method is developed to solve the exterior and interior Dirichlet problems for two-dimensional Laplace equation, which takes the characteristic length of problem domain into account. After introducing a circular artificial boundary which is uniquely determined by the physical problem domain, we can derive a Dirichlet to Dirichlet mapping equation, which is an exact boundary condition. By truncating the Fourier series expansion one can match the physical boundary condition as accurate as one desired. Then, we use the collocation method and the Galerkin method to derive linear equations system to determine the Fourier coefficients. Here, the factor… More >

Chein-Shan Liu ¹

CMES-Computer Modeling in Engineering & Sciences, Vol.20, No.2, pp. 111-122, 2007, DOI:10.3970/cmes.2007.020.111

Abstract A highly accurate new solver is developed to deal with interior and exterior mixed-boundary value problems for two-dimensional Laplace equation, including the singular ones. To promote the present study, we introduce a circular artificial boundary which is uniquely determined by the physical problem domain, and derive a Dirichlet to Robin mapping on that artificial circle, which is an exact boundary condition described by the first kind Fredholm integral equation. As a consequence, we obtain a modified Trefftz method equipped with a characteristic length factor, ensuring that the new solver is stable because the condition number can be greatly reduced. Then,… More >

Igor Patlashenko¹, Dan Givoli²

CMES-Computer Modeling in Engineering & Sciences, Vol.1, No.2, pp. 61-70, 2000, DOI:10.3970/cmes.2000.001.221

Abstract The method of Absorbing Boundary Conditions (ABCs) is considered for the numerical solution of a class of nonlinear exterior wave scattering problems. Recently, a scheme based on the exact nonlocal Dirichlet-to-Neumann (DtN) ABC has been proposed for such problems. Although this method is very accurate, it is also highly expensive computationally. In this paper, the nonlocal ABC is replaced by a low-order local ABC, which is obtained by localizing the DtN condition in a certain "optimal'' way. The performance of the new local scheme is compared to that of the nonlocal scheme via numerical experiments in two dimensions. More >