Sarang Seyrafian¹, Behrouz Gatmiri², Asadollah Noorzad³

CMES-Computer Modeling in Engineering & Sciences, Vol.15, No.2, pp. 115-126, 2006, DOI:10.3970/cmes.2006.015.115

Abstract An analytical solution is presented for the response of a non-homogeneous saturated poroelastic half-space under the action of a time-harmonic vertical point load on its surface. The shear modulus is assumed to increase continuously with depth and also the media is considered to obey Biot's poroelastic theory. The system of governing partial differential equations, based on the mentioned assumptions, is converted to ordinary differential equations' system by means of Hankel integral transforms. Then the system of equations is solved by use of generalized power series(Frobenius method) and the expressions for displacements in the interior of the media or in the… More >

N.S.Mera¹, L. Elliott², D.B.Ingham²

CMES-Computer Modeling in Engineering & Sciences, Vol.15, No.2, pp. 107-114, 2006, DOI:10.3970/cmes.2006.015.107

Abstract The purpose of this study is to investigate the efficiency, accuracy and rate of convergence of an evolutionary algorithm for detecting inclusions parametrised by superellipses in non-destructive evaluation and testing. The inverse problem investigated consists of identifying the geometry of discontinuities in a conductive material from Cauchy data measurements taken on the boundary. Temperature and heat flux are measured on the outside boundary of the domain and the position and the size of a super-elliptical inclusion are determined by minimising an objective functional using an evolution strategy. The super-elliptical form allows the parametric model to characterise a variety of shapes… More >

Adrián P. Cisilino¹

CMES-Computer Modeling in Engineering & Sciences, Vol.15, No.2, pp. 99-106, 2006, DOI:10.3970/cmes.2006.015.099

Abstract Topological Optimization provides a powerful framework to obtain the optimal domain topology for several engineering problems. The Topological Derivative is a function which characterizes the sensitivity of a given problem to the change of its topology, like opening a small hole in a continuum or changing the connectivity of rods in a truss.
A numerical approach for the topological optimization of 2D potential problems using Boundary Elements is presented in this work. The formulation of the problem is based on recent results which allow computing the topological derivative from potential and flux results. The Boundary Element analysis is done… More >

Paola Gardano¹, Peter Dabnichki^1,2

CMES-Computer Modeling in Engineering & Sciences, Vol.15, No.2, pp. 87-98, 2006, DOI:10.3970/cmes.2006.015.087

Abstract The work presents a numerical simulation of hydrodynamic forces generated in front crawl swimming. The three dimensional Laplace's equation is used for the analysis of the flow around a moving body in an infinite domain and considers the effect of the added mass and the acceleration on the hydrodynamic forces (Drag and Lift) generated by the interaction between the flow and the body at different geometric configurations of the arm -- variable elbow angle. Boundary Element Method (BEM) was used to obtain the solution of the three dimensional equation numerically. The aim of the work was two-fold:
1) to… More >

Chein-Shan Liu¹

CMES-Computer Modeling in Engineering & Sciences, Vol.15, No.2, pp. 69-86, 2006, DOI:10.3970/cmes.2006.015.069

Abstract In this paper we will study the numerical integrations of second order boundary value problems under the imposed conditions at t=0 and t=T in a general setting. We can construct a compact space shooting method for finding the unknown initial conditions. The key point is based on the construction of a one-step Lie group element G(u₀,u_T) and the establishment of a mid-point Lie group element G(r). Then, by imposing G(u₀,u_T) = G(r) we can search the missing initial conditions through an iterative solution of the weighting factor r ∈ (0,1). Numerical examples were examined to convince that the new approach… More >

Rade Vignjevic¹, Juan R. Reveles¹, James Campbell¹

CMES-Computer Modeling in Engineering & Sciences, Vol.14, No.3, pp. 181-198, 2006, DOI:10.3970/cmes.2006.014.181

Abstract To correct some of the main shortcomings of conventional SPH, a version of this method based on the Total Lagrangian formalism, T. Rabczuk, T. Belytschko and S. Xiao (2004), is developed. The resulting scheme removes the spatial discretisation instability inherent in conventional SPH, J. Monaghan (1992).
The Total Lagrangian framework is combined with the mixed correction which ensures linear completeness and compliance with the patch test, R. Vignjevic, J. Campbell, L. Libersky (2000). The mixed correction utilizes Shepard Functions in combination with a correction to derivative approximations.
Incompleteness of the kernel support combined with the lack of consistency… More >

S. Noroozi¹, P. Sewell¹, J. Vinney¹

CMES-Computer Modeling in Engineering & Sciences, Vol.14, No.3, pp. 171-180, 2006, DOI:10.3970/cmes.2006.014.171

Abstract A method that combines a modified back propagation Artificial Neural Network (ANN) and Boundary Element Analysis (BEA) was introduced and discussed in the author's previous papers. This paper discusses the development of an automated inverse boundary element problem engine. This inverse problem engine can be applied to both potential and elastostatic problems.
In this study, BEA solutions of a two-dimensional potential problem is utilised to test the system and to train a back propagation Artificial Neural Network (ANN). Once training is completed and the transfer function is created, the solution to any subsequent or new problems can be obtained… More >

L.S. Miers¹, J.C.F. Telles²

CMES-Computer Modeling in Engineering & Sciences, Vol.14, No.3, pp. 161-170, 2006, DOI:10.3970/cmes.2006.014.161

Abstract This work aims at extending the concept of the Numerical Green's Function (NGF), well known from boundary element applications to fracture mechanics, to the Local Boundary Integral Equation (LBIE) context. As a "companion" solution, the NGF is used to remove the integrals over the crack boundary and is introduced only for source points whose support touches or contains the crack. The results obtained with the coupling of NGF-LBIE in previous potential discontinuity Laplace's equation problems and the authors' experience in NGF-BEM fracture mechanics were the motivation for this development. More >

L.A. de Lacerda¹, J. M. da Silva¹

CMES-Computer Modeling in Engineering & Sciences, Vol.14, No.3, pp. 153-160, 2006, DOI:10.3970/cmes.2006.014.153

Abstract A two-dimensional boundary element formulation is presented and coupled to a genetic algorithm to identify polarization curves of buried slender structures. The dual boundary element method is implemented to model the cathodic protection of the metallic body and the genetic algorithm is employed to deal with the inverse problem of determining the non-linear polarization curve, which describes the relation between current density and electrochemical potential at the soil metal interface. In this work, this non-linear relation resulting from anodic and cathodic reactions is represented by a classical seven parameters expression. Stratified soil resistivity is modeled with a piece-wise homogeneous domain.… More >

S. N. Atluri¹, H. T. Liu², Z. D. Han²

CMES-Computer Modeling in Engineering & Sciences, Vol.14, No.3, pp. 141-152, 2006, DOI:10.3970/cmes.2006.014.141

Abstract The Meshless Local Petrov-Galerkin (MLPG) mixed collocation method is proposed in this paper, for solving elasticity problems. In the present MLPG approach, the mixed scheme is applied to interpolate the displacements and stresses independently, as in the MLPG finite volume method. To improve the efficiency, the local weak form is established at the nodal points, for the stresses, by using the collocation method. The traction boundary conditions are also imposed into the stress equations directly. It becomes very simple and straightforward to impose various boundary conditions, especially for the high-order PDEs. Numerical examples show that the proposed MLPG mixed collocation… More >