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  • Open Access


    CFD and Experimental Investigations of Drag Force on Spherical Leak Detector in Pipe Flows at High Reynolds Number

    ShiXu Guo1, Shili Chen1, Xinjing Huang1, Yu Zhang1, Shijiu Jin1

    CMES-Computer Modeling in Engineering & Sciences, Vol.101, No.1, pp. 59-80, 2014, DOI:10.3970/cmes.2014.101.059

    Abstract Spherical leak detectors can detect very tiny leakage in pipelines and have low risk of blockage. In this paper the passing ability of the detector in the vertical segment of a pipe was studied using CFD simulations and experiments. The Reynolds number for the sphere exceeds 104 at the economical velocity range for oil pipelines, and there were few researches related to the hydrodynamic force on the sphere by the pipe flow at high Reynolds number. For sphere with different sizes and density, and at different flow rates, more than 100 3-D steady numerical simulations were carried out. The simulation… More >

  • Open Access


    Numerical Solution of System of N–Coupled Nonlinear Schrödinger Equations via Two Variants of the Meshless Local Petrov–Galerkin (MLPG) Method

    M. Dehghan1, M. Abbaszadeh2, A. Mohebbi3

    CMES-Computer Modeling in Engineering & Sciences, Vol.100, No.5, pp. 399-444, 2014, DOI:10.3970/cmes.2014.100.399

    Abstract In this paper three numerical techniques are proposed for solving the system of N-coupled nonlinear Schrödinger (CNLS) equations. Firstly, we obtain a time discrete scheme by approximating the first-order time derivative via the forward finite difference formula, then for obtaining a full discretization scheme, we use the Kansa’s approach to approximate the spatial derivatives via radial basis functions (RBFs) collocation methodology. We introduce the moving least squares (MLS) approximation and radial point interpolation method (RPIM) with their shape functions, separately. It should be noted that the shape functions of RPIM unlike the shape functions of the MLS approximation have kronecker… More >

  • Open Access


    Algebraic Multigrid Methods Based on Generic Approximate Banded Inverse Matrix Techniques

    George A. Gravvanis1, Christos K. Filelis-Papadopoulos1, Paschalis I.Matskanidis1

    CMES-Computer Modeling in Engineering & Sciences, Vol.100, No.4, pp. 323-345, 2014, DOI:10.3970/cmes.2014.100.323

    Abstract Since the introduction of the Algebraic MultiGrid algorithm (AMG) over twenty years ago, significant progress has been made in improving the coarsening and the convergence behavior of the method. In this paper, an AMG method is introduced that utilizes a new generic approximate inverse algorithm as a smoother in conjunction with common coarsening techniques, such as classical Ruge-Stüben coarsening, CLJP and PMIS coarsening. The proposed approximate inverse scheme, namely Generic Approximate Banded Inverse (GenAbI), is a banded approximate inverse based on Incomplete LU factorization with zero fill–in (ILU(0)). The new class of Generic Approximate Banded Inverse can be computed for… More >

  • Open Access


    A Self-regularization Technique in Boundary Element Method for 3-D Stress Analysis

    M. G. He1, C.L. Tan1

    CMES-Computer Modeling in Engineering & Sciences, Vol.95, No.4, pp. 317-349, 2013, DOI:10.3970/cmes.2013.095.315

    Abstract The self-regularization technique in the Boundary Element Method (BEM) originally proposed by Cruse and Richardson (1996, 1999) in their work for two-dimensional (2-D) stress analysis is extended to three-dimensional (3-D) elastostatics in this paper. The regularization scheme addresses the issue of accurate numerical evaluation of the integrals due to the singularity of the kernel functions of the integral equations. It is first implemented for the determination of displacements and stresses at interior points of the solution domain, and very accurate results are obtained even when these points are very close to the surface of the domain. A self-regularized traction-BIE is… More >

  • Open Access


    A Coupled BEM-MLPG Technique for the Thermal Analysis of Non-Homogeneous Media

    A. Tadeu1, P. Stanak2, J. Sladek2, V. Sladek2, J. Prata1, N. Simões1

    CMES-Computer Modeling in Engineering & Sciences, Vol.93, No.6, pp. 489-516, 2013, DOI:10.3970/cmes.2013.093.489

    Abstract This paper presents a technique that couples the boundary element method (BEM) with the meshless local Petrov-Galerkin (MLPG) method, formulated in the frequency domain. It is then used to study the transient heat diffusion through a two-dimensional unbounded medium containing confined subdomains where the material properties vary from point to point. To exploit the advantages of each method, the BEM is used for the homogeneous unbounded domain and the MLPG method is used for the non-homogeneous confined subdomains. The nodal points placed at the interface between the confined subdomains and the unbounded homogenous medium are used to couple the BEM… More >

  • Open Access


    A Simple Proper Orthogonal Decomposition Method for von Karman Plate undergoing Supersonic Flow

    Dan Xie1, Min Xu2

    CMES-Computer Modeling in Engineering & Sciences, Vol.93, No.5, pp. 377-409, 2013, DOI:10.3970/cmes.2013.093.377

    Abstract We apply a simple proper orthogonal decomposition (POD) method to compute the nonlinear oscillations of a degenerate two-dimensional fluttering plate undergoing supersonic flow. First, the von Karman’s large deflection theory and quasi-steady aerodynamic theory are employed in constructing the governing equations of the simply supported plate. Then, the governing equations are solved by both the Galerkin method and the POD method. The Galerkin method is accurate but sometimes computationally expensive, since the number of degrees of freedom (dofs) required is relatively large provided that nonlinearity is strong. The POD method can be used to capture the complex dynamics of a… More >

  • Open Access


    A comparative study of three domain-integral evaluation techniques in the boundary-domain integral equation method for transient thermoelastic crack analysis in FGMs

    A.V. Ekhlakov1,2, O.M. Khay1,3, Ch. Zhang1, X.W. Gao4, J. Sladek5, V. Sladek5

    CMES-Computer Modeling in Engineering & Sciences, Vol.92, No.6, pp. 595-614, 2013, DOI:10.3970/cmes.2013.092.595

    Abstract A boundary-domain integral equation method is applied to the transient thermoelastic crack analysis in functionally graded materials. Fundamental solutions for homogeneous, isotropic and linear elastic materials are used to derive the boundary-domain integral equations. The radial integration method, the Cartesian transformation method and the cell-integration method are applied for the evaluation of the arising domain-integrals. Numerical results for dynamic stress intensity factors obtained by the three approaches are presented, compared and discussed to show the accuracy and the efficiency of the domain-integral evaluation techniques. More >

  • Open Access


    Multiobjective Optimization for Ship Hull Form Design Using SBD Technique

    Shengzhong Li1, Feng Zhao1, Qi-Jun Ni1

    CMES-Computer Modeling in Engineering & Sciences, Vol.92, No.2, pp. 123-149, 2013, DOI:10.3970/cmes.2013.092.123

    Abstract With the rapid development of computer technology and the continuous improvement of optimization theory, optimization techniques have been introduced into the field of ship design. Optimization algorithms and advanced CFD techniques are successfully integrated together into what is known as Simulation- Based Design (SBD) techniques, which opens a new situation for hull-form optimization design and configuration innovation. In this paper, fundamental elements of the SBD techniques are described and crucial components are analyzed profoundly. Focus is on breaking through key technologies as hull geometry modification and reconstruction, global optimization algorithms, and codes integration. Combined with high-fidelity CFD codes (on RANS),… More >

  • Open Access


    Compact Local IRBF and Domain Decomposition Method for solving PDEs using a Distributed termination detection based parallel algorithm

    N. Pham-Sy1, C.-D. Tran1, T.-T. Hoang-Trieu1, N. Mai-Duy1, T. Tran-Cong1

    CMES-Computer Modeling in Engineering & Sciences, Vol.92, No.1, pp. 1-31, 2013, DOI:10.3970/cmes.2013.092.001

    Abstract Compact Local Integrated Radial Basis Function (CLIRBF) methods based on Cartesian grids can be effective numerical methods for solving partial differential equations (PDEs) for fluid flow problems. The combination of the domain decomposition method and function approximation using CLIRBF methods yields an effective coarse-grained parallel processing approach. This approach has enabled not only each sub-domain in the original analysis domain to be discretised by a separate CLIRBF network but also compact local stencils to be independently treated. The present algorithm, namely parallel CLIRBF, achieves higher throughput in solving large scale problems by, firstly, parallel processing of sub-regions which constitute the… More >

  • Open Access


    Characterization and modeling of the multiscale pore structures for porous materials

    X.F. Guan1, X. Liu2, J.Z. Cui3

    CMES-Computer Modeling in Engineering & Sciences, Vol.91, No.6, pp. 425-444, 2013, DOI:10.3970/cmes.2013.091.425

    Abstract In this paper, a stochastic geometrical modeling method for reconstructing three dimensional multiscale pore structures of porous materials is presented. In this method, the pore structure in porous materials is represented by a random but spatially correlated pore-network, in which the results of the Mercury Intrusion Porosimetry (MIP) experiment are used as the basic input information. Beside that, based on the Monte Carlo techniques, an effective computer generation algorithm is developed, and the quantities to evaluate the properties of porous materials are defined and described. Furthermore, numerical implementations are conducted based on experimental data afterwards. This method can be used… More >

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