P.R. Venkatesh¹, B.Chandrasekhar² , M.M.Benal³

CMES-Computer Modeling in Engineering & Sciences, Vol.52, No.1, pp. 83-104, 2009, DOI:10.3970/cmes.2009.052.083

Abstract In this work, node based basis functions are used to solve the acoustic scattering from plain thin bodies like plates, discs; and intersecting thin bodies like fins on a cylinder. Node based basis functions are defined on the vertices of triangles generated by triangular patch modeling, and these functions are used to define the unknown source distribution. Also the same functions are used as testing functions in the method of moment's solution. Three kinds of nodes were treated for defining the basis functions, namely, boundary node, non-boundary node and non boundary intersecting node. Also, three kinds of bodies were considered… More >

Chan T.L.^1,2, Xie M.L.^1,3, Cheung C.S.¹

CMES-Computer Modeling in Engineering & Sciences, Vol.51, No.3, pp. 191-212, 2009, DOI:10.3970/cmes.2009.051.191

Abstract An efficient Petrov-Galerkin Chebyshev spectral method coupled with the Taylor-series expansion method of moments (TEMOM) was developed to simulate the effect of coherent structures on particle coagulation in the exhaust pipe. The Petrov-Galerkin Chebyshev spectral method was presented in detail focusing on the analyticity of solenoidal vector field used for the approximation of the flow. It satisfies the pole condition exactly at the origin, and can be used to expand the vector functions efficiently by using the solenoidal condition. This developed TEMOM method has no prior requirement for the particle size distribution (PSD). It is much simpler than the method… More >

J.-M. Battini¹

CMES-Computer Modeling in Engineering & Sciences, Vol.33, No.1, pp. 1-16, 2008, DOI:10.3970/cmes.2008.033.001

Abstract This paper deals with the parameterisation of large rotations in corotational beam and shell elements. Several alternatives, presented in previous articles, are summarised, completed and compared to each other. The implementation of applied external moments and eccentric forces, consistent with the different parameterisations, is also considered. More >

Raj Mittra¹, V.V.S. Prakash¹

CMES-Computer Modeling in Engineering & Sciences, Vol.5, No.5, pp. 435-442, 2004, DOI:10.3970/cmes.2004.005.435

Abstract In this paper, we introduce a novel approach for the efficient solution of electromagnetic scattering problems from objects that can be represented in terms of facets. The approach is based on the use of the Characteristic Basis Functions (CBFs), which are high-level basis functions of special types, and whose domains are not bound by the conventional Rao, Wilton and Glisson (RWG) discretization using triangular patches that are typically$\lambda$/10 to$\lambda$/20 in size. In contrast, the CBFs are defined over much larger-size domains, even tens of wavelengths in size, with no limit placed on the dimensions of the facets. The use of… More >

B. Chandrasekhar¹

CMES-Computer Modeling in Engineering & Sciences, Vol.56, No.3, pp. 211-230, 2010, DOI:10.3970/cmes.2010.056.211

Abstract In this work, various basis functions used in the Method of Moments or Boundary Element (MoM/BEM) solution of acoustic scattering problems are compared with each other for their performance. Single layer formulation of the rigid bodies is considered in comparison of the solutions. Geometry of a scatterer is descritized using triangular patch modeling and basis functions are defined on triangular patches, edges and nodes for three different solutions. Far field scattering cross sections for different frequencies of incident acoustic wave are compared with the closed form solutions. Also, the errors of the solutions using these three types of basis functions… More >

T.N. Killian¹, S.M. Rao¹ and M.E. Baginski¹

CMES-Computer Modeling in Engineering & Sciences, Vol.46, No.3, pp. 255-270, 2009, DOI:10.3970/cmes.2009.046.255

Abstract In this work, we present a new method of moments solution procedure for calculating acoustic/electromagnetic scattering and radiation by a metallic body whose physical dimension is very large with respect to wavelength. The specially computed basis functions and the testing procedure results in a block-diagonally-dominant moment matrix where each block along the diagonal corresponds to a portion of the structure. The new solution procedure results in considerable savings in terms of computer storage and processing times. Although the procedure is outlined in general mathematical terms, the numerical results are presented only for electromagnetic scattering from two-dimensional bodies and compared with… More >

B. Chandrasekhar¹

CMES-Computer Modeling in Engineering & Sciences, Vol.33, No.3, pp. 243-268, 2008, DOI:10.3970/cmes.2008.033.243

Abstract In this work, a novel numerical technique, based on method of moments solution, is presented to solve the Combined layer formulation (CLF) to insure unique solution to the exterior acoustic scattering problem at all frequencies. A new set of basis functions, namely, Node based basis functions are used to represent the source distribution on the surface of rigid body and the same functions are used as testing functions as well. Combined layer formulation (CLF) is defined by linearly combining the Single layer formulation (SLF) and Double layer formulation (DLF) with complex coupling parameter. The matrix equations for the SLF and… More >

B. Chrasekhar¹, Sadasiva. M. Rao²

CMES-Computer Modeling in Engineering & Sciences, Vol.33, No.2, pp. 199-214, 2008, DOI:10.3970/cmes.2008.033.199

Abstract In this work, the acoustic scattering problem based on double layer formulation is solved with a novel numerical technique using method of moment's solution. A new set of basis functions, namely, Edge based Adaptive Basis Functions (EABF) are defined in the method of moment's solution procedure. The geometry of the body is divided into triangular patches and basis functions are defined on the edges. Since the double layer formulation involves the evaluation of the hyper-singular integral, the edge based adaptive basis functions are used to make the solution faster. The matrix equations are derived for the double layer formulation. The… More >

B. Chrasekhar¹, S. M. Rao²

CMES-Computer Modeling in Engineering & Sciences, Vol.8, No.2, pp. 105-118, 2005, DOI:10.3970/cmes.2005.008.105

Abstract In this work, a simple, robust, and an efficient numerical algorithm to calculate the scattered acoustic fields from complex shaped objects such as aircrafts and missiles, subjected to a plane wave incidence is presented. The work is based on the recently proposed method of moments (MoM) and the potential theory, unlike the standard Helmholtz integral equation (HIE) solution method. For the numerical solution, the scattering structure is approximated by planar triangular patches. For the MoM solution of complex bodies involving open/closed/intersecting surfaces, a unified set of basis functions to approximate the source distribution is defined. These basis functions along with… More >