CMES-Vol. 32, No. 2, 2008

Open Access

ARTICLE

A Time-Domain FEM-BEM Iterative Coupling Algorithm to Numerically Model the Propagation of Electromagnetic Waves
Delfim Soares Jr. ¹
CMES-Computer Modeling in Engineering & Sciences, Vol.32, No.2, pp. 57-68, 2008, DOI:10.3970/cmes.2008.032.057
Abstract In this work, a time-domain finite element -- boundary element iterative coupling technique is presented in order to analyse electromagnetic scattering from two-dimensional inhomogeneous objects. In the iterative coupling algorithm, the domain of the original problem is subdivided into sub-domains and each sub-domain is analysed independently (as an uncoupled model) taking into account successive renewals of variables at common interfaces. In order to improve the effectiveness of the iterative coupling approach, the evaluation of an optimised relaxation parameter is discussed, taking into account the minimisation of a square error functional. The algorithm that arises is efficient, accurate and flexible. At… More >

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ARTICLE

Discontinuous Weighted Least-Squares Approximation on Irregular Grids
N.B.Petrovskaya ¹
CMES-Computer Modeling in Engineering & Sciences, Vol.32, No.2, pp. 69-84, 2008, DOI:10.3970/cmes.2008.032.069
Abstract Discontinuous weighted least--squares (DWLS) approximation is a modification of a standard weighted least-squares approach that nowadays is intensively exploited in computational aerodynamics. A DWLS method is often employed to approximate a solution function over an unstructured computational grid that results in an irregular local support for the approximation. While the properties of a weighted least-squares reconstruction are well known for regular geometries, the approximation over a non-uniform grid is not a well researched area so far. In our paper we demonstrate the difficulties related to the performance of a DWLS method on distorted grids and outline a new approach based… More >

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Optimization of Industrial Fluid Catalytic Cracking Unit having Five Lump Kinetic Scheme using Genetic Algorithm
Shishir Sinha¹, Praveen Ch.
CMES-Computer Modeling in Engineering & Sciences, Vol.32, No.2, pp. 85-102, 2008, DOI:10.3970/cmes.2008.032.085
Abstract Fluid catalytic cracking (FCC) unit plays most important role in the economy of a modern refinery that it is use for value addition to the refinery products. Because of the importance of FCC unit in refining, considerable effort has been done on the modeling of this unit for better understanding and improved productivity. The process is characterized by complex interactions among feed quality, catalyst properties, unit hardware parameters and process conditions. \newline The traditional and global approach of cracking kinetics is lumping. In the present paper, five lump kinetic scheme is considered, where gas oil crack to give lighter fractions… More >

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Crack Propagation in Concrete Using Meshless Method
N. Sageresan, R. Drathi
CMES-Computer Modeling in Engineering & Sciences, Vol.32, No.2, pp. 103-112, 2008, DOI:10.3970/cmes.2008.032.103
Abstract Crack propagation in concrete is computed with a simplified meshless method. The material is elastic of Neo-Hookian type until fracture. Then a discrete cohesive crack method is used. In the cohesive crack method, cohesive segments are introduced at the meshless nodes. No representation of the crack surface is needed. The method is well-suited for concrete since concrete develops many cracks. Mesh independent results are obtained due to the cohesive model that takes into account the correct energy dissipation during crack opening. We show the accuracy of our method by comparison to experimental data. More >

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