V. Sladek¹, J. Sladek¹, Ch. Zhang²

CMES-Computer Modeling in Engineering & Sciences, Vol.63, No.3, pp. 243-264, 2010, DOI:10.3970/cmes.2010.063.243

Abstract The paper deals with diminishing the prolongation of the computational time due to procedural evaluation of the shape functions and their derivatives in weak formulations implemented with meshless approximations. The proposed numerical techniques are applied to problems of stationary heat conduction in functionally graded media. Besides the investigation of the computational efficiency also the accuracy and convergence study are performed in numerical tests. More >

CMC-Computers, Materials & Continua, Vol.18, No.3, pp. 271-300, 2010, DOI:10.3970/cmc.2010.018.271

Abstract The processing maps are a superimposition of iso-efficiency contour map and flow instability map, which are used to design hot working processing conditions in a wide variety of materials. In order to construct the processing maps, the efficiency of power dissipation and an instability criterion taking into account the contribution of strain and microstructure evolution are proposed based on a set of microstructure-based viscoplastic constitutive equations. In viscoplastic constitutive equations, the grain size of matrix phase and the dislocation density are taken as internal state variables. And, the material constants in present equations can be… More >

Min Ki Kim¹, Seung Jo Kim²

The International Conference on Computational & Experimental Engineering and Sciences, Vol.12, No.2, pp. 52-52, 2009, DOI:10.3970/icces.2009.012.052

Abstract A new concept of hybrid iterative-multifrontal linear solution method is presented for large scale structural analysis problems. Multifrontal solution method is the best direct solution method ever known, so it is adequate for Domain decompostion types of iterative solvers. Multifrontal solver is served as an internal subdomain solver for domain decomposition iterative solver for achieving high performance of domain decomposition iterative solver. Lagrange multiplier is introduced to enforce the continuity of interface between subdomains. And corner DOF is introduced to avoid singularities of subdomains. Hybrid solution method is expected to show good parallel performance for More >

Peter Lucas¹, Alexander H. van Zuijlen¹, Hester Bijl¹

CMES-Computer Modeling in Engineering & Sciences, Vol.41, No.2, pp. 147-176, 2009, DOI:10.3970/cmes.2009.041.147

Abstract Mesh adaptation is a fairly established tool to obtain numerically accurate solutions for flow problems. Computational efficiency is, however, not always guaranteed for the adaptation strategies found in literature. Typically excessive mesh growth diminishes the potential efficiency gain. This paper, therefore, extends the strategy proposed by [Aftosmis and Berger (2002)] to compute the refinement threshold. The extended strategy computes the refinement threshold based on a user desired number of grid cells and adaptations, thereby ensuring high computational efficiency. Because our main interest is flow around wind turbines, the adaptation strategy has been optimized for flow More >

Castellanos-Pérez¹ E, AG de Soyza², GB Donart³

Phyton-International Journal of Experimental Botany, Vol.77, pp. 297-320, 2008, DOI:10.32604/phyton.2008.77.297

Abstract The study was conducted in the Chihuahuan Desert Rangeland Research Center, 32 km north of Las Cruces, NM, USA. Physiological responses of the shrub Larrea tridentata (DC) Cov. and the perennial grass Muhlenbergia porteri Scribn were determined from the summer 1997 to the winter 1998-99 when they grew together. In the summer 1997, Larrea tridentata competed for water with M. porteri, as shrubs growing alone showed higher integrated photosynthesis than shrubs in competition with M. porteri following a heavy rainfall event. Larrea tridentata had lower water use efficiency (WUE) than M. porteri plants. In the summer 1998, M. porteri had greater pre-dawn xylem… More >

A. Alexenadrescu¹, A.S. Alex,rescu¹, A.C. Alexandrescu¹

The International Conference on Computational & Experimental Engineering and Sciences, Vol.8, No.2, pp. 47-58, 2008, DOI:10.3970/icces.2008.008.047

Abstract The paper follows the analyse of the connections between the constructive, working parameters, the annual energy consumptions and the energy quantity included in fitting out; it will formulate a methodology of establishment of the optimum values of the parameters of admeasurements of the pumping stations for the setting under pressure, of pipes networks, what ensure an optimum consumption of energy during of duty of the fitting out (the operational energy and the included energy in the networks, equipment and constructions), of the conditions after that it can be obtained. It will follow the generalization of More >

M.R. Moosavi¹, A. Khelil¹

The International Conference on Computational & Experimental Engineering and Sciences, Vol.5, No.4, pp. 211-238, 2008, DOI:10.3970/icces.2008.005.211

Abstract In this paper, a combined formulation of the Finite Volume Method (FVM) and the Meshless Local Petrov-Galerkin (MLPG) is investigated to solve elasto-static problem. Accuracy and computational efficiency study between the combined formulation and the Finite Element Method (FEM) is presented. Some problems of beam under various loading and boundary conditions are analyzed by the proposed method, and the numerical results are compared with analytical solution and result of other numerical method which is obtained by well-known FEM software ABAQUS. The advantages of the FVM combined MLPG (FVMLPG) with respect to the FEM are illustrated. More >

T.Z. Desta¹, G. De Bruyne¹, J.-M. Aerts¹, M. Baelmans², D. Berckmans¹

CMES-Computer Modeling in Engineering & Sciences, Vol.31, No.2, pp. 61-70, 2008, DOI:10.3970/cmes.2008.031.061

Abstract This paper demonstrates the use of the concept of the local mean age of air (LMAA) to quantify ventilation effectiveness under bicycle rider's safety helmets. The specific objective is to study the effect of helmet openings on the resulting ventilation effectiveness. To quantify ventilation effectiveness using the concept of LMAA, dynamic tracer gas data are necessary. The data were generated using a Computational Fluid Dynamics (CFD) model. Two bicycle helmet designs were used and compared with respect to ventilation performance. The result showed that the helmet with more openings had better performance especially at the More >

F.C. Araújo¹, L.J. Gray²

The International Conference on Computational & Experimental Engineering and Sciences, Vol.2, No.2, pp. 41-46, 2007, DOI:10.3970/icces.2007.002.041

Abstract This paper is concerned with the solution of boundary-element models based on substructuring. Structured matrix-vector products and the matrix-copy option are proposed to increase the efficiency of algorithms based on Krylov solvers. The former technique was designed to avoid the excessive number of conditional tests during solver iterations, and the latter one, to avoid the repeated calculation of coefficient matrices for identical subregions. Potential applications of the algorithm to composite materials, and to develop parallel codes, are noted. More >

J. M. F. Trindade¹, J. C. F. Pereira²

CMES-Computer Modeling in Engineering & Sciences, Vol.20, No.1, pp. 1-10, 2007, DOI:10.3970/cmes.2007.020.001

Abstract In this paper, we discuss the efficiency and speed-up of parallel-in-time calculations of the unsteady incompressible Navier-Stokes equations in a PC-cluster. The parallel-in-time method is based on the alternate use of coarse global sequential solvers with fine local parallel ones in an iterative predictor-corrector fashion. Therefore, the efficiency of parallel calculations is strongly dependent on the number of iterations required for convergence. The one-dimensional scalar transport equation and the two-dimensional incompressible unsteady form of the Navier-Stokes equations were used to conduct numerical experiments to derive some conclusions concerning the accuracy and convergence of the iterative… More >