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  • Open Access

    ARTICLE

    Numerical Solution of Non-steady Flows, Around Surfaces in Spatially and Temporally Arbitrary Motions, by using the MLPG method

    R. Avila1, S. N. Atluri2

    CMES-Computer Modeling in Engineering & Sciences, Vol.54, No.1, pp. 15-64, 2009, DOI:10.3970/cmes.2009.054.015

    Abstract The Meshless Local Petrov Galerkin (MLPG) method is used to solve the non-steady two dimensional Navier-Stokes equations. Transient laminar flow field calculations have been carried out in domains wherein certain surfaces have: (i) a sliding motion, (ii) a harmonic motion, (iii) an undulatory movement, and (iv) a contraction-expansion movement. The weak form of the governing equations has been formulated in a Cartesian coordinate system and taking into account the primitive variables of the flow field. A fully implicit pressure correction approach, which requires at each time step an iterative process to solve in a sequential… More >

  • Open Access

    ARTICLE

    Stable Manifolds of Saddles in Piecewise Smooth Systems

    A. Colombo1, U. Galvanetto2

    CMES-Computer Modeling in Engineering & Sciences, Vol.53, No.3, pp. 235-254, 2009, DOI:10.3970/cmes.2009.053.235

    Abstract The paper addresses the problem of computing the stable manifolds of equilibria and limit cycles of saddle type in piecewise smooth dynamical systems. All singular points that are generically present along one-dimensional or two-dimensional manifolds are classified and such a classification is then used to define a method for the numerical computation of the stable manifolds. Finally the proposed method is applied to the case of a stick-slip oscillator. More >

  • Open Access

    ARTICLE

    A Scalar Homotopy Method for Solving an Over/Under-Determined System of Non-Linear Algebraic Equations

    Chein-Shan Liu1, Weichung Yeih2, Chung-Lun Kuo3, Satya N. Atluri4

    CMES-Computer Modeling in Engineering & Sciences, Vol.53, No.1, pp. 47-72, 2009, DOI:10.3970/cmes.2009.053.047

    Abstract Iterative algorithms for solving a system of nonlinear algebraic equations (NAEs): Fi(xj) = 0, i, j = 1,... ,n date back to the seminal work of Issac Newton. Nowadays a Newton-like algorithm is still the most popular one to solve the NAEs, due to the ease of its numerical implementation. However, this type of algorithm is sensitive to the initial guess of solution, and is expensive in terms of the computations of the Jacobian matrix ∂Fi/∂xj and its inverse at each iterative step. In addition, the Newton-like methods restrict one to construct an iteration procedure for n-variables… More >

  • Open Access

    ARTICLE

    Solution Methods for Nonsymmetric Linear Systems with Large off-Diagonal Elements and Discontinuous Coefficients

    Dan Gordon1, Rachel Gordon2

    CMES-Computer Modeling in Engineering & Sciences, Vol.53, No.1, pp. 23-46, 2009, DOI:10.3970/cmes.2009.053.023

    Abstract Linear systems with very large off-diagonal elements and discontinuous coefficients (LODC systems) arise in some modeling cases, such as those involving heterogeneous media. Such problems are usually solved by domain decomposition methods, but these can be difficult to implement on unstructured grids or when the boundaries between subdomains have a complicated geometry. Gordon and Gordon have shown that Björck and Elfving's (sequential) CGMN algorithm and their own block-parallel CARP-CG are very robust and efficient on strongly convection dominated cases (but without discontinuous coefficients). They have also shown that scaling the equations by dividing each equation… More >

  • Open Access

    ARTICLE

    Numerical Simulation and Natural Computing applied to a Real World Traffic Optimization Case under Stress Conditions:

    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 More >

  • Open Access

    ARTICLE

    The Temperature-Quantum-Correction Effect on the MD-Calculated Thermal Conductivity of Silicon Thin Films

    Tai-Ming Chang1, Chien-Chou Weng1, Mei-Jiau Huang1,2, Chun-KaiLiu2, Chih-Kuang Yu2

    CMES-Computer Modeling in Engineering & Sciences, Vol.50, No.1, pp. 47-66, 2009, DOI:10.3970/cmes.2009.050.047

    Abstract We employ the non-equilibrium molecular dynamics (NEMD) simulation to calculate the in-plane thermal conductivity of silicon thin films of thickness 2.2nm and 11nm. To eliminate the finite-size effect, samples of various lengths are simulated and an extrapolation technique is applied. To perform the quantum correction which is necessary as the MD simulation temperature is lower than Debye temperature, the confined phonon spectra are obtained in advance via the EMD simulations. The investigation shows the thermal conductivities corrected based on the bulk and thin-film phonon densities of states are very close and they agree excellently with More >

  • Open Access

    ARTICLE

    Dynamical Response of Two Axially Pre-Strained System Comprising of a Covering Layer and a Half Space to Rectangular Time-Harmonic Forces

    I. Emiroglu1, F. Tasci1, S. D. Akbarov2

    CMES-Computer Modeling in Engineering & Sciences, Vol.49, No.1, pp. 47-68, 2009, DOI:10.3970/cmes.2009.049.047

    Abstract The time-harmonic dynamical stress field in the system comprising two axially pre-stressed covering layer and two axially pre-stressed half space was studied under the action of uniformly distributed forces on free face plane of the covering layer. It is assumed that the forces are distributed within the rectangular area. The study was conducted within the scope of the piecewise homogeneous body model with the use of three-dimensional theory of elastic waves in an initially stressed bodies. The materials of the layer and half-space were assumed to be isotropic and homogeneous. The corresponding three-dimensional boundary-value-contact problem… More >

  • Open Access

    ARTICLE

    In virtuo Experiments Based on the Multi-Interaction System Framework: the RéISCOP Meta-Model.

    G. Desmeulles, S. Bonneaud, P. Redou>, V. Rodin, J. Tisseau

    CMES-Computer Modeling in Engineering & Sciences, Vol.47, No.3, pp. 299-330, 2009, DOI:10.3970/cmes.2009.047.299

    Abstract Virtual reality can enable computer scientists and domain experts to perform in virtuo experiments of numerical models of complex systems. Such dynamical and interactive experiments are indeed needed when it comes to complex systems with complex dynamics and structures. In this context, the question of the modeling tool to study such models is crucial. Such tool, called a virtuoscope, must enable the virtual experimentation of models inside a conceptual and experimental framework for imagining, modeling and experimenting the complexity of the studied systems. This article describes a conceptual framework and a meta model, called RéISCOP, that enable More >

  • Open Access

    ARTICLE

    Three Dimensional Nonlinear Temperature and Structural Analysis of Roller compacted Concrete Dam

    J. Noorzaei1, K.H. Bayagoob2, A.A. Abdulrazeg1, M.S. Jaafar1,1, T.A. Mohammed1

    CMES-Computer Modeling in Engineering & Sciences, Vol.47, No.1, pp. 43-60, 2009, DOI:10.3970/cmes.2009.047.043

    Abstract This paper focuses on the development, verification and application of a three-dimensional finite element code for coupled thermal and structural analysis of roller compacted concrete dams. The Kinta RCC gravity dam, which is the first roller compacted concrete dam in Malaysia, has been taken for the purpose of verification of the finite element code. The actual climatic conditions and thermal properties of the materials were considered in the analysis. The structural stress analysis was performed using the elasto-plastic stress analysis. The Mohr yield criterion which is widely used for concrete plasticity modeling was adopted in More >

  • Open Access

    ARTICLE

    An Improved Petrov-Galerkin Spectral Collocation Solution for Linear Stability of Circular Jet

    Xie Ming-Liang1,2, Zhou Huai-Chun1, Chan Tat-Leung3

    CMES-Computer Modeling in Engineering & Sciences, Vol.46, No.3, pp. 271-290, 2009, DOI:10.3970/cmes.2009.046.271

    Abstract A Fourier-Chebyshev Petrov-Galerkin spectral method is described for computation of temporal linear stability in a circular jet. Basis functions presented here are exponentially mapped Chebyshev functions. They satisfy the pole condition exactly at the origin, and can be used to expand vector functions efficiently by using the solenoidal condition. The mathematical formulation is presented in detail focusing on the analyticity of solenoidal vector field used for the approximation of the flow. The scheme provides spectral accuracy in the present cases studied and the numerical results are in agreement with former works. More >

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