The Study of Effective Engineering Parallel Computation for Fluid-Film Lubrication Analysis

• Main Authors: Chih Ming Tsai, 蔡智明
• Other Authors: N. Wang
• Format: Others
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/15702371816546510359

博士 === 長庚大學 === 機械工程研究所 === 97 === In the field of Tribology fluid-film lubrication analysis is usually a hard computing problem which can not be satisfactorily solved within a reasonable time when sequential computation is used. When fluid viscosity and density variation, bearing surface elasticity or/and non-Newtonianity are taken into account in lubrication analysis, the task of solving Reynolds equation for film pressure distribution is not only complicated but also time consuming. In this study of parallel computing for the lubrication analysis the models of air-lubricated and THD (Thermohydrodynamic) bearings were used. The Straightforward OpenMP paradigm for SMP (Shared-Memory Processing) parallelism and its extension to a cluster, Cluster OpenMP, were examined. And an open source software, openMosix, which is designed for automatic load balancing in a cluster was also compared for its performance in parallel computing. In this study, the sequential programs for bearing analysis are easily transformed to parallel ones by adding some OpenMP directives. Then, the programs can be compiled and executed as multithreaded applications. When the two processor cores are used for the air bearing and THD analyses the resulted speedups are 1.53 and 1.66, respectively. The corresponding parallel efficiencies are 15.9% and 41%. In the case of parallel optimization of bearings, an openMosix cluster of 16 computing nodes was used. A speedup of 2.54 (15.9%) was obtained when the lattice search was used in the air bearing optimization. While in the THD lubrication model the DIRECT (DIviding RECTangles) algorithm was used as the optimization tool, a speedup of 6.65 (41%) was obtained in the same cluster. However, the standard DIRECT algorithm can be easily modified to explore the computing resources in a parallel environment to create the so-called embarrassingly parallel DIRECT algorithm. The results of speedup of 10.54 or parallel efficiency of 65.9% were can be achieved. It is noted that the straightforward OpenMP and openMosix parallel programming models can help to minimize the computing time in solving lubrication problems and implementing optimum design for bearings. The procedure laid out in this study can be applied to other complex lubrication analyses or many computationally expensive applications in engineering.