P. Le¹, N. Mai-Duy², T. Tran-Cong³, G. Baker⁴

CMES-Computer Modeling in Engineering & Sciences, Vol.25, No.1, pp. 43-68, 2008, DOI:10.3970/cmes.2008.025.043

Abstract This paper describes an integrated radial basis function network (IRBFN) method for the numerical modelling of the dynamics of strain localization due to strain softening in quasi-brittle materials. The IRBFN method is a truly meshless method that is based on an unstructured point collocation procedure. We introduce a new and effective regularization method to enhance the performance of the IRBFN method and alleviate the numerical oscillations associated with weak discontinuity at the elastic wave front. The dynamic response of a one dimensional bar is investigated using both local and non-local continuum models. Numerical results, which compare favourably with those obtained… More >

D. Soares Jr.¹, M. P. Vinagre²

CMES-Computer Modeling in Engineering & Sciences, Vol.25, No.1, pp. 1-8, 2008, DOI:10.3970/cmes.2008.025.001

Abstract This work presents an alternative procedure to compute time-domain electromagnetic fields. The Boundary Element Method is here adopted to numerically analyze wave propagation problems, computing just a so-called primary field (either the electric or the magnetic field can be selected as primary field; the complementary field is here named secondary field). The secondary field is obtained following Maxwell's equations, i.e., considering space derivatives of the primary field (computed by the Complex Variable Method) and time integration procedures. This methodology is more efficient and flexible since fewer systems of equations must be solved at each time-step. At the end of the… More >

Q.W. Ma¹

CMES-Computer Modeling in Engineering & Sciences, Vol.23, No.2, pp. 75-90, 2008, DOI:10.3970/cmes.2008.023.075

Abstract In the MLPG_R (Meshless Local Petrove-Galerkin based on Rankine source solution) method, one needs a meshless interpolation scheme for an unknown function to discretise the governing equation. The MLS (moving least square) method has been used for this purpose so far. The MLS method requires inverse of matrix or solution of a linear algebraic system and so is quite time-consuming. In this paper, a new scheme, called simplified finite difference interpolation (SFDI), is devised. This scheme is generally as accurate as the MLS method but does not need matrix inverse and consume less CPU time to evaluate. Although this scheme… More >

Xiang Jiawei¹, Chen Xuefeng², Yang Lianfa³, He Zhengjia⁴

CMES-Computer Modeling in Engineering & Sciences, Vol.23, No.1, pp. 1-12, 2008, DOI:10.3970/cmes.2008.023.001

Abstract A class of flat shell elements is constructed by using the scaling functions of two-dimensional tensor product B-spline wavelet on the interval (BSWI). Unlike the process of direct wavelets adding in the wavelet Galerkin method, the element displacement field represented by the coefficients of wavelets expansions was transformed from wavelet space into physical space via the constructed two-dimensional transformation matrix. Then, the BSWI flat shell element is constructed by the assembly of BSWI plane elastomechanics and Mindlin plate elements. Because of the good character of BSWI scaling functions, the BSWI flat shell element combine the accuracy of B-spline functions approximation… More >

Ya Yan Lu¹, Jianxin Zhu²

CMES-Computer Modeling in Engineering & Sciences, Vol.22, No.3, pp. 235-248, 2007, DOI:10.3970/cmes.2007.022.235

Abstract The perfectly matched layer (PML) is a widely used technique for truncating unbounded domains in numerical simulations of wave propagation problems. In this paper, the PML technique is used with a standard one-way model to solve a benchmark problem for underwater acoustics modeling. Accurate solutions are obtained with a PML layer with a thickness of only a quarter of the wavelength. The effect of a PML is analyzed in a perturbation analysis for waveguides. More >

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 >

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 >

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 propagation. It involves Daubechies scaling… More >

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 transitions occurring between them. The… More >

Baran Aydın^1,2, 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 shallow-water wave equations are solved… More >