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  • Open Access

    ARTICLE

    Investigation of the Effect of Frictional Contact in III-Mode Crack under Action of the SH-Wave Harmonic Load

    A.N. Guz1, V.V. Zozulya2

    CMES-Computer Modeling in Engineering & Sciences, Vol.22, No.2, pp. 119-128, 2007, DOI:10.3970/cmes.2007.022.119

    Abstract The frictional contact interaction of the edges of a finite plane crack is studied for the case of normal incidence of a harmonic SH-shear wave which produces antiplane deformation. The forces of contact interaction and displacement discontinuity are analyzed. Influence of the wave frequency on the stress intensity factor for different coefficients of friction is studied here. More >

  • Open Access

    ARTICLE

    A Comparative Study of Non-separable Wavelet and Tensor-product Wavelet in Image Compression

    Jun Zhang1

    CMES-Computer Modeling in Engineering & Sciences, Vol.22, No.2, pp. 91-96, 2007, DOI:10.3970/cmes.2007.022.091

    Abstract The most commonly used wavelets for image processing are the tensor-product of univariate wavelets, which have a disadvantage of giving a particular importance to the horizontal and vertical directions. In this paper, a new class of wavelet, non-separable wavelet, is investigated for image compression applications. The comparative results of image compression preprocessed with two different kinds of wavelet transform are presented: (1) non-separable wavelet transform; (2) tensor-product wavelet transform. The results of our experiments show that in the same vanishing moment, the non-separable wavelets perform better than the tensor-product wavelets in dealing with still images. More >

  • Open Access

    ARTICLE

    Modeling of Degraded Composite Beam Due to Moisture Absorption For Wave Based Detection.

    Shamsh Tabrez, Mira Mitra, S. Gopalakrishnan1

    CMES-Computer Modeling in Engineering & Sciences, Vol.22, No.1, pp. 77-90, 2007, DOI:10.3970/cmes.2007.022.077

    Abstract In this paper, wave propagation is studied in degraded composite beam due to moisture absorption. The obtained wave responses are then used for diagnosis of the degraded zone. Moisture absorption causes an irreversible hygrothermal deterioration of the material. The change in temperature and moisture absorption changes the mechanical properties. Thus this affects the structure in dimensional stability as well as material degradation due to reduction in mechanical properties. Here, the composite beam is modeled as Timoshenko beam using wavelet based spectral finite element (WSFE) method. The WSFE technique is especially tailored for simulation of wave More >

  • Open Access

    ARTICLE

    Asymptotic Analysis for the Coupled Wavenumbers in an Infinite Fluid-Filled Flexible Cylindrical Shell: The Axisymmetric Mode

    Abhijit Sarkar1, Venkata R. Sonti1

    CMES-Computer Modeling in Engineering & Sciences, Vol.21, No.3, pp. 193-208, 2007, DOI:10.3970/cmes.2007.021.193

    Abstract The coupled wavenumbers of a fluid-filled flexible cylindrical shell vibrating in the axisymmetric mode are studied. The coupled dispersion equation of the system is rewritten in the form of the uncoupled dispersion equation of the structure and the acoustic fluid, with an added fluid-loading term involving a parameter$\epsilon$ due to the coupling. Using the smallness of Poisson's ratio$(\nu )$, a double-asymptotic expansion involving$\epsilon$ and$\nu ^2$ is substituted in this equation. Analytical expressions are derived for the coupled wavenumbers (for large and small values of$\epsilon$). Different asymptotic expansions are used for different frequency ranges with continuous More >

  • Open Access

    ARTICLE

    Wind Set-down Relaxation

    Baran Aydın1,2, Utku Kânoğlu3

    CMES-Computer Modeling in Engineering & Sciences, Vol.21, No.2, pp. 149-156, 2007, DOI:10.3970/cmes.2007.021.149

    Abstract We developed analytical solutions to the wind set-down and the wind set-down relaxation problems. The response of the ocean to the wind blowing over a long-narrow and linearly sloping shallow basin is referred to as wind set-down. The shoreline exhibits oscillatory behavior when the wind calms down and the resulting problem is referred to as wind set-down relaxation. We use an existing hodograph-type transformation that was introduced to solve the nonlinear shallow-water wave equations analytically for long wave propagation and obtain an explicit-transform analytical solution for wind set-down. For the wind set-down relaxation, the nonlinear More >

  • Open Access

    ARTICLE

    An Investigation of Wave Propagation with High Wave Numbers via the Regularized LBIEM

    H.B. Chen1, D.J. Fu1, P.Q. Zhang1

    CMES-Computer Modeling in Engineering & Sciences, Vol.20, No.2, pp. 85-98, 2007, DOI:10.3970/cmes.2007.020.085

    Abstract Researches today show that, both approximation and dispersion errors are encountered by classical Galerkin FEM solutions for Helmholtz equation governing the harmonic wave propagation, which leads to numerical inaccuracies especially for high wave number cases. In this paper, Local Boundary Integral Equation Method (LBIEM) is firstly implemented to solve the boundary value problem of Helmholtz equation. Then the regularized LBIE is proposed to overcome the singularities of the boundary integrals in the LBIEM. Owing to the advantages of the Moving Least Square Approximation (MLSA), the frequency-dependent basis functions modified by the harmonic wave propagation solutions More >

  • Open Access

    ARTICLE

    Numerical Generation of Freak Waves Using MLPG_R and QALE-FEM Methods

    Q.W. Ma1

    CMES-Computer Modeling in Engineering & Sciences, Vol.18, No.3, pp. 223-234, 2007, DOI:10.3970/cmes.2007.018.223

    Abstract Two methods have been recently developed by the author and his group: one called MLPG_R (Meshless Local Petrov-Galerkin method based on Rankine source solution) and the other called QALE-FEM (Quasi Arbitrary Lagrangian-Eulerian Finite Element Method). The former is a meshless method developed from a general MLPG (Meshless Local Petrov-Galerkin) method and is more computationally efficient than the general one when applied to modelling nonlinear water waves. The later is a mesh-based method similar to a conventional finite element method (FEM) when discretizing the governing equations but different from the conventional one in managing the mesh. More >

  • Open Access

    ARTICLE

    Contact Problem for the Flat Elliptical Crack under Normally Incident Shear Wave

    A.N. Guz1, O.V. Menshykov1,2, V.V. Zozulya3, I.A. Guz2

    CMES-Computer Modeling in Engineering & Sciences, Vol.17, No.3, pp. 205-214, 2007, DOI:10.3970/cmes.2007.017.205

    Abstract The contact interaction of opposite faces of an elliptical crack is studied for the case of a normal time-harmonic shear wave loading. The distribution of stress intensity factors (shear modes II and III) as functions of the wave number and the friction coefficient is investigated. The results are compared with those obtained for an elliptical crack without allowance for the contact interaction. More >

  • Open Access

    ARTICLE

    Cumulative Nonlinear Effects in Acoustic Wave Propagation

    Ivan Christov1, C.I. Christov2, P.M. Jordan3

    CMES-Computer Modeling in Engineering & Sciences, Vol.17, No.1, pp. 47-54, 2007, DOI:10.3970/cmes.2007.017.047

    Abstract Two widely-used weakly-nonlinear models of acoustic wave propagation --- the inviscid Kuznetsov equation (IKE) and the Lighthill--Westervelt equation (LWE) --- are investigated numerically using a Godunov-type finite-difference scheme. A reformulation of the models as conservation laws is proposed, making it possible to use the numerical tools developed for the Euler equations to study the IKE and LWE, even after the time of shock-formation. It is shown that while the IKE is, without qualification, in very good agreement with the Euler equations, even near the time of shock formation, the same cannot generally be said for More >

  • Open Access

    ARTICLE

    An Explicit Multi-Level Time-Step Algorithm to Model the Propagation of Interacting Acoustic-Elastic Waves Using Finite Element/Finite Difference Coupled Procedures

    D. Soares Jr.1,2, W.J. Mansur1, D.L. Lima3

    CMES-Computer Modeling in Engineering & Sciences, Vol.17, No.1, pp. 19-34, 2007, DOI:10.3970/cmes.2007.017.019

    Abstract The present paper discussion is concerned with the development of robust and efficient algorithms to model propagation of interacting acoustic and elastic waves. The paper considers acoustic-elastic, acoustic-acoustic and elastic-elastic partitioned analyses of coupled systems; however, the focus here is the acoustic-elastic coupling considering finite elements and the acoustic-acoustic coupling considering finite elements and finite differences (other coupling procedures can be implemented analogously). One important feature of the algorithms presented is that they allow considering different time-steps for different sub-domains; so it is possible to substantially improve efficiency, accuracy and stability of the central difference More >

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