Engineering Computations: International Journal for Computer-Aided Engineering and Software

S.T. Lie; G. Yu

2002 Engineering Computations: International Journal for Computer-Aided Engineering and Software

doi: 10.1108/02644400210413630

The time domain BEM/FEM coupling procedure is applied to 2‐D multi‐domain fluid–structure interaction problems. The fluid domain is acoustic and modeled by taking advantage of the BEM scheme that is suitable to either finite or infinite domains. The structure is modeled by elastodynamic finite elements that can be either linear or nonlinear. The input impact, which can be either plane waves or non‐plane waves, can either be forces acting directly on the fluid–structure system or be explosion sources in the fluid. The far field or near field explosion sources, which are difficult to be simulated for finite element analysis, are very easy to be simulated here by boundary element modeling as internal sources. The stability problem is solved by using the linear &thetas; method, which makes the BEM scheme stable. The numerical results are compared with analytical solutions for two examples.

Mun‐Bo Shim; Myung‐Won Suh; Tomonari Furukawa; Genki Yagawa; Shinobu Yoshimura

2002 Engineering Computations: International Journal for Computer-Aided Engineering and Software

doi: 10.1108/02644400210413649

In an attempt to solve multiobjective optimization problems, many traditional methods scalarize an objective vector into a single objective by a weight vector. In these cases, the obtained solution is highly sensitive to the weight vector used in the scalarization process and demands a user to have knowledge about the underlying problem. Moreover, in solving multiobjective problems, designers may be interested in a set of Pareto‐optimal points, instead of a single point. In this paper, Pareto‐based Continuous Evolutionary Algorithms for Multiobjective Optimization problems having continuous search space are introduced. These algorithms are based on Continuous Evolutionary Algorithms, which were developed by the authors to solve single‐objective optimization problems with a continuous function and continuous search space efficiently. For multiobjective optimization, a progressive reproduction operator and a niche‐formation method for fitness sharing and a storing process for elitism are implemented in the algorithm. The operator and the niche formulation allow the solution set to be distributed widely over the Pareto‐optimal tradeoff surface. Finally, the validity of this method has been demonstrated through some numerical examples.

M. Naïmi; M. Hasnaoui; J.K. Platten

2002 Engineering Computations: International Journal for Computer-Aided Engineering and Software

doi: 10.1108/02644400210413658

Analytical and numerical studies are conducted for two‐dimensional steady‐state coupled Marangoni and buoyancy convection of a non‐Newtonian power law fluid confined in a rectangular horizontal shallow cavity subjected to a horizontal temperature gradient between the two short vertical rigid sides, while the upper free surface and the lower rigid one are insulated. The results obtained by combining the two basic mechanisms (thermocapillarity and buoyancy) depend on whether their effects are aiding or opposite. The effect of the non‐Newtonian behavior on the fluid flow, the temperature field, and the heat transfer is studied. The parallel flow is obtained in some particular situations for which a good agreement is observed between the analytical results based on the parallel flow assumption and those corresponding to the numerical simulations.

K. Han; D.R.J. Owen; D. Peric

2002 Engineering Computations: International Journal for Computer-Aided Engineering and Software

doi: 10.1108/02644400210413667

Because of the unrealistic demand of computer resources in terms of memory and CPU times for the direct numerical simulation of practical peen forming processes, a two‐stage combined finite/discrete element and explicit/implicit solution strategy is proposed in this paper. The procedure involves, at the first stage, the identification of the residual stress/strain profile under particular peening conditions by employing the combined finite/discrete approach on a small scale sample problem, and then at the second stage, the application of this profile to the entire workpiece to obtain the final deformation and stress distribution using an implicit static analysis. The motivation behind the simulation strategy and the relevant computational and implementation issues are discussed. The numerical example demonstrates the ability of the proposed scheme to simulate a peen forming process.

W.K. Chan; S.L. Lee; C.Y. Liu

2002 Engineering Computations: International Journal for Computer-Aided Engineering and Software

doi: 10.1108/02644400210413676

This paper presents studies on low Reynolds number pulsating flow in a circular pipe. The Navier‐Stokes equations expressed in terms of primitive variables on a clustered staggered grid were solved. A block tridiagonal algorithm coupled with cyclic reduction techniques was used to reduce computation effort. The effects of frequency on the amplitude of the fluctuating axial velocity are confined mainly to the wall region. The effects due to changes in frequency parameter are insignificant near the inlet region. The amplitude of pulsating axial velocity changes from inlet to the fully developed region by about 10% whereas for the time mean velocity, the amplitude almost doubles. It was observed that flow reversal begins at the pipe inlet section when the amplitude of oscillation is equal or greater than 1.0 and in the developing region, flow reversal would occur when the amplitude factor is greater than the critical amplitude factor.