CMES-Vol. 6, No. 5, 2004

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Geometry of Flow Pattern from Single Source
C. K. Au¹
CMES-Computer Modeling in Engineering & Sciences, Vol.6, No.5, pp. 409-420, 2004, DOI:10.3970/cmes.2004.006.409
Abstract Tracking the flow fronts arising from a primary source in a bounded space with obstacles is a problem which often requires intensive computation. As the flow propagates through the obstacles, the flow pattern is complicated. This phenomenon is mainly due to the existence of the secondary sources which can be identified in the flow field by visibility. Comparing the flow fronts propagation and the wave equation reveals that the complexity is caused by the propagation phenomena: reflection, refraction, diffraction and interference. This paper investigates a geometric technique to combine these phenomena for computing flow fronts. More >

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Direct and Indirect Approach of a Desingularized Boundary Element Formulation for Acoustical Problems
S. Callsen¹, O. von Estorff¹, O. Zaleski²
CMES-Computer Modeling in Engineering & Sciences, Vol.6, No.5, pp. 421-430, 2004, DOI:10.3970/cmes.2004.006.421
Abstract In standard boundary element formulations, singular integrals need to be solved as soon as the considered sources coincide with the collocation points at the boundary. Using a desingularized boundary element approach, the sources are distributed on a surface outside the acoustic domain which means that they are never located at the boundary. Consequently, all the resulting kernels are nonsingular which reduces the complexity of the numerical treatment of the boundary integral equations considerably. In the current contribution a desingularized formulation is given for both, the direct and the indirect boundary element method used to solve More >

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A General Tangent Operator Procedure for Implicit Elastoplastic BEM Analysis
L.S. Miers, J.C.F. Telles¹
CMES-Computer Modeling in Engineering & Sciences, Vol.6, No.5, pp. 431-440, 2004, DOI:10.3970/cmes.2004.006.431
Abstract Most formulations involving the use of the so-called consistent elastoplastic tangent operator procedure, in boundary element analysis, have been presented taking in consideration only a J₂-type yield criterion, like von Mises. The present paper aims at bringing a general consistency concept to tangent operators obtained without yield criterion particularization, ready to be used in implicit schemes for elastoplastic BEM analysis. The ideas follows much of the second author's physically nonlinear implicit BEM solution procedures introduced in the 80's and is based on a Taylor series expansion of the true effective stress around an equivalent stress corresponding More >

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2D Incompressible Viscous Flows at Moderate and High Reynolds Numbers
Alfredo Nicolás¹, Blanca Bermúdez²
CMES-Computer Modeling in Engineering & Sciences, Vol.6, No.5, pp. 441-452, 2004, DOI:10.3970/cmes.2004.006.441
Abstract 2D incompressible vicous flows from the unsteady Navier-Stokes equations in stream function-vorticity variables are presented. The results are obtained using a simple numerical procedure based on a fixed point iterative process to solve the nonlinear elliptic system that results once a second order time discretization is performed. Flows on the unregularized unit driven cavity are reported up to Reynolds numbers Re=5000 to compare them with those reported by other authors and supposed to be correct. Various long time computations are presented for Re=10000 to see its evolution as time-dependent flow. Moreover, results are reported for Re=10000, Re=15000 More >

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A Cell Method (CM) Code for Modeling the Pullout Test Step-wise
E. Ferretti ¹
CMES-Computer Modeling in Engineering & Sciences, Vol.6, No.5, pp. 453-476, 2004, DOI:10.3970/cmes.2004.006.453
Abstract The Cell Method (CM) code with automatic remeshing for crack propagation analysis [Ferretti (2003)] is here used for modeling the pullout test. Particular emphasis is given to the analysis in the Mohr-Coulomb plane, since previous numerical models were not decisive in describing failure mechanism in pullout tests. The interpretations of experimental and analytical studies vary widely, and none of the existing explanations offer a complete description of the progressive failure of the concrete medium [Yener (1994)]. Nor do most existing interpretations appear to be totally compatible with the experimental evidence. Analysis of the failure mechanism… More >

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Meshless Local Petrov-Galerkin Method in Anisotropic Elasticity
J. Sladek¹, V. Sladek¹, S.N. Atluri²
CMES-Computer Modeling in Engineering & Sciences, Vol.6, No.5, pp. 477-490, 2004, DOI:10.3970/cmes.2004.006.477
Abstract A meshless method based on the local Petrov-Galerkin approach is proposed for solution of static and elastodynamic problems in a homogeneous anisotropic medium. The Heaviside step function is used as the test functions in the local weak form. It is leading to derive local boundary integral equations (LBIEs). For transient elastodynamic problems the Laplace transfor technique is applied and the LBIEs are given in the Laplace transform domain. The analyzed domain is covered by small subdomains with a simple geometry such as circles in 2-d problems. The final form of local integral equations has a More >

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