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  • Open Access


    The Accuracy of Mathematical Models in Simulator Distributed Computing

    I. Kvasnica1, P. Kvasnica2

    CMES-Computer Modeling in Engineering & Sciences, Vol.107, No.6, pp. 447-462, 2015, DOI:10.3970/cmes.2015.107.447

    Abstract The issue of simulation of decentralized mathematical models is discussed in the paper. The authors’ knowledge is based on a theory of design of decentralized computer control systems. Their knowledge is gained in the process of designing mathematical models that are simulated. A decomposed control system is required to meet the conditions of observation and control. The methodology of a multi-model design is based on main principles of object orientation such as abstraction, hierarchy, and modularity. Modelling on a parallel architecture has an impact on a simulator system. The system is defined by the equations shown below. An important part… More >

  • Open Access


    A High-Order Accurate Wavelet Method for Solving Three-Dimensional Poisson Problems

    Xiaojing Liu1,2, Jizeng Wang1, Youhe Zhou1

    CMES-Computer Modeling in Engineering & Sciences, Vol.107, No.6, pp. 433-446, 2015, DOI:10.3970/cmes.2015.107.433

    Abstract Based on the approximation scheme for a L2-function defined on a three-dimensional bounded space by combining techniques of boundary extension and Coiflet-type wavelet expansion, a modified wavelet Galerkin method is proposed for solving three-dimensional Poisson problems with various boundary conditions. Such a wavelet-based solution procedure has been justified by solving five test examples. Numerical results demonstrate that the present wavelet method has an excellent numerical accuracy, a fast convergence rate, and a very good capability in handling complex boundary conditions. More >

  • Open Access


    Method for Detecting Macroscopic Irregularities in Gears Based on Template Matching and the Nonequivalence Operation

    W.C. Wang1, F.L. Chang2, Y.L. Liu1, X. J. Wu1

    CMES-Computer Modeling in Engineering & Sciences, Vol.107, No.5, pp. 411-431, 2015, DOI:10.3970/cmes.2015.107.411

    Abstract The detection of macroscopic irregularities is an essential procedure during the production of gears, and it helps to guarantee the quality of electromechanical transmission equipment. The working principles of template matching and the image nonequivalence operation are described in detail in this paper. Gray-level transformation, edge-preserving filtering, image segmentation, feature extraction, and pattern recognition were analyzed, leading to the design of a defect detection system based on template matching and the nonequivalence operation, followed by the development of a hardware platform and application software for the system. The experimental results indicate that the proposed detection system could perform fast detection… More >

  • Open Access


    A Finite Wavelet Domain Method for the Rapid Analysis of Transient Dynamic Response in Rods and Beams

    C.V. Nastos, T.C. Theodosiou, C.S. Rekatsinas, D.A. Saravanos1

    CMES-Computer Modeling in Engineering & Sciences, Vol.107, No.5, pp. 379-409, 2015, DOI:10.3970/cmes.2015.107.379

    Abstract A computationally efficient numerical method is developed for the prediction of transient response in orthotropic rod and beam structures. The method takes advantage of the outstanding properties of compactly supported Daubechies wavelet scaling functions for the spatial approximation of displacements in a finite domain of the structure, hence is termed Finite Wavelet Domain (FWD) method. The basic principles and advantages of the method are presented and the discretization of the equations of motion is formulated for one-dimensional structures. Numerical results for the simulation of propagating guided waves in rods and strips are presented and compared against traditional finite elements. More >

  • Open Access


    The Influence of Non-Homogeneous Material Properties on ElasticWave Propagation in Fluid-Filled Boreholes

    A. Tadeu1, P. Stanak2, J. Antonio1, J. Sladek2, V. Sladek2

    CMES-Computer Modeling in Engineering & Sciences, Vol.107, No.5, pp. 345-378, 2015, DOI:10.3970/cmes.2015.107.345

    Abstract This paper implements a numerical method based on the mutual coupling of the boundary element method (BEM) and the meshless local Petrov-Galerkin (MLPG) method to simulate elastic wave propagation in fluid-filled boreholes. The fluid-solid interaction is solved in the frequency domain assuming longitudinally invariant geometry in the axial direction (2.5D formulation).
    This model is used to assess the influence of the non-homogeneous material properties of a borehole wall that can be caused by a damaged zone, construction process or the ageing of material. The BEM is used to model propagation within the unbounded homogeneous domain and the fluid domain… More >

  • Open Access


    An Advanced ACA/BEM for Solving 2D Large-Scale Elastic Problems with Multi-Connected Domains

    T. Gortsas1, S.V. Tsinopoulos2, D. Polyzos1,3

    CMES-Computer Modeling in Engineering & Sciences, Vol.107, No.4, pp. 321-343, 2015, DOI:10.3970/cmes.2015.107.321

    Abstract An advanced Boundary Element method (BEM) accelerated via Adaptive Cross Approximation (ACA) and Hierarchical Matrices (HM) techniques is presented for the solution of large-scale elastostatic problems with multi-connected domains like in fiber reinforced composite materials. Although the proposed ACA/ BEM is demonstrated for two-dimensional (2D) problems, it is quite general and it can be used for 3D problems. Different forms of ACA technique are employed for exploring their efficiency when they combined with a BEM code. More precisely, the fully and partially pivoted ACA with and without recompression are utilized, while the solution of the final linear system of equations… More >

  • Open Access


    Large Eddy Simulation Combined with Characteristic-Based Operator-Splitting Finite Element Method

    Da-guo Wang1,2, Bin Hu1, Qing-xiang Shui1

    CMES-Computer Modeling in Engineering & Sciences, Vol.107, No.4, pp. 297-320, 2015, DOI:10.3970/cmes.2015.107.297

    Abstract A numerical large eddy simulation (LES) method combined with the characteristic-based operator-splitting finite element method is proposed. The subgrid eddy viscosity model is used to calculate sub-grid stress in LES. In each time step, the governing equations are split into diffusive and convective parts. The convective part is first discretized by using the characteristic Galerkin method and then solved explicitly. The backward-facing step flow and the flow past a single cylinder are adopted to validate the model. Results agree with existing numerical results or experimental data. The flow past two cylinders in tandem arrangement is also studied at Re =… More >

  • Open Access


    Elastodynamic Analysis of Thick Multilayer Composite Plates by The Boundary Element Method

    J. Useche1, H. Alvarez1

    CMES-Computer Modeling in Engineering & Sciences, Vol.107, No.4, pp. 277-296, 2015, DOI:10.3970/cmes.2015.107.277

    Abstract Dynamic stress analysis of laminated composites plates represents a relevant task in designing of aerospace, shipbuilding and automotive components where impulsive loads can lead to sudden structural failure. The mechanical complexity inherent to these kind of components makes the numerical modeling an essential engineering analysis tool. This work deals with dynamic analysis of stresses and deformations in laminated composites thick plates using a new Boundary Element Method formulation. Composite laminated plates were modeled using the Reissner’s plate theory. We propose a direct time-domain formulation based on elastostatic fundamental solution for symmetrical laminated thick plates. Formulation takes into account the rotational… More >

  • Open Access


    Structural-Acoustic Design Sensitivity Analysis based on Direct Differentiation Method with Different Element Types

    L.L. Chen1, H.B. Chen1,2

    CMES-Computer Modeling in Engineering & Sciences, Vol.107, No.3, pp. 249-276, 2015, DOI:10.3970/cmes.2015.107.249

    Abstract Engineers have started to develop ways to decrease noise radiation. Structural-acoustic design sensitivity analysis can provide information on how changes in design variable affect the radiated acoustic performance. As such, it is an important step in the structural-acoustic design and in optimization processes. For thin structures immersed in water, a full interaction between the structural domain and the fluid domain needs to be taken into account. In this work, the finite element method is used to model the structure parts and the boundary element method is applied to the exterior acoustic problem. The formula of the sound pressure sensitivity based… More >

  • Open Access


    An Explicit Time Marching Technique With Solution-Adaptive Time Integration Parameters

    Delfim Soares Jr.1

    CMES-Computer Modeling in Engineering & Sciences, Vol.107, No.3, pp. 223-247, 2015, DOI:10.3970/cmes.2015.107.223

    Abstract In this work, an explicit time marching procedure, with solution-adaptive time integration parameters, is introduced for the analysis of hyperbolic models. The proposed technique is conditionally-stable, second-order accurate and it has controllable algorithm dissipation, which locally adapts at each time step, according to the computed solution. Thus, spurious modes can be more effectively dissipated and accuracy is improved. Since this is an explicit time integration technique, the new procedure is very efficient, requiring no system of equations to be dealt with at each time-step. Moreover, the technique is simple and easy to implement, being based just on displacement-velocity relations, requiring… More >

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