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 >

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… More >

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 More >

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 More >

Patrícia C.T. Gonçalves^1,2, João Manuel R.S. Tavares^1,2, R.M. Natal Jorge^1,3

CMES-Computer Modeling in Engineering & Sciences, Vol.32, No.1, pp. 45-56, 2008, DOI:10.3970/cmes.2008.032.045

Abstract The main goals of the present work are to automatically extract the contour of an object and to simulate its deformation using a physical approach. In this work, to segment an object represented in an image, an initial contour is manually defined for it that will then automatically evolve until it reaches the border of the desired object. In this approach, the contour is modelled by a physical formulation using the finite element method, and its temporal evolution to the desired final contour is driven by internal and external forces. The internal forces are defined… More >

G.A. Gravvanis, K.M. Giannoutakis¹

CMES-Computer Modeling in Engineering & Sciences, Vol.32, No.1, pp. 35-44, 2008, DOI:10.3970/cmes.2008.032.035

Abstract A new parallel normalized optimized approximate inverse algorithm, based on the concept of the ``fish bone'' computational approach with cyclic distribution of the processors satisfying an antidiagonal data dependency, for computing classes of explicit approximate inverses, is introduced for symmetric multiprocessor systems. The parallel normalized explicit approximate inverses are used in conjunction with parallel normalized explicit preconditioned conjugate gradient square schemes, for the efficient solution of finite element sparse linear systems. The parallel design and implementation issues of the new proposed algorithms are discussed and the parallel performance is presented, using OpenMP. More >

Hossein M. Shodja^1,2,3, Alireza Hashemian^1,4

CMES-Computer Modeling in Engineering & Sciences, Vol.32, No.1, pp. 17-34, 2008, DOI:10.3970/cmes.2008.032.017

Abstract Gradient reproducing kernel particle method (GRKPM) is a meshless technique which incorporates the first gradients of the function into the reproducing equation of RKPM. Therefore, in two-dimensional space GRKPM introduces three types of shape functions rather than one. The robustness of GRKPM's shape functions is established by reconstruction of a third-order polynomial. To enforce the essential boundary conditions (EBCs), GRKPM's shape functions are modified by transformation technique. By utilizing the modified shape functions, the weak form of the nonlinear evolutionary Buckley-Leverett (BL) equation is discretized in space, rendering a system of nonlinear ordinary differential equations More >

Chein-Shan Liu¹, Chih-Wen Chang², Jiang-Ren Chang^2,3

CMES-Computer Modeling in Engineering & Sciences, Vol.32, No.1, pp. 1-16, 2008, DOI:10.3970/cmes.2008.032.001

Abstract In this paper, we propose a new method to tackle of two famous boundary layer equations in fluid mechanics, namely, the Falkner-Skan and the Blasius equations. We can employ this method to find unknown initial conditions. The pivotal point is based on the erection of a one-step Lie group element$\mathbf {G}(T)$ and the formation of a generalized mid-point Lie group element$\mathbf {G}(r)$. Then, by imposing$\mathbf {G}(T) = \mathbf {G}(r)$ we can seek the missing initial conditions through a minimum discrepancy from the target in terms of a weighting factor$r \in (0, 1)$. Numerical examples are More >

Y.Y Zhang, L. Chen

CMES-Computer Modeling in Engineering & Sciences, Vol.31, No.3, pp. 189-200, 2008, DOI:10.3970/cmes.2008.031.189

Abstract A simplified meshless method for dynamic crack growth is presented. The method uses an extrinsic enrichment based on a local partition of unity concept. The crack is represented by a set of crack segments. The crack segments are required to pass through the entire domain of influence of node. They are introduced when the maximum principal stress exceeds the uniaxial tensile strength. The crack segments are allowed to rotate in order to avoid too stiff system responses. The major advantage of our method is that it does not require algorithms to track the crack path. More >

L. Mai-Cao¹, T. Tran-Cong²

CMES-Computer Modeling in Engineering & Sciences, Vol.31, No.3, pp. 157-188, 2008, DOI:10.3970/cmes.2008.031.157

Abstract This paper presents a new meshless numerical approach to solving a special class of moving interface problems known as the passive transport where an ambient flow characterized by its velocity field causes the interfaces to move and deform without any influences back on the flow. In the present approach, the moving interface is captured by the level set method at all time as the zero contour of a smooth function known as the level set function whereas one of the two new meshless schemes, namely the SL-IRBFN based on the semi-Lagrangian method and the Taylor-IRBFN More >