TED-AJ03-388 CONVERGENCE ACCELERATION BY RELAXATION FACTOR DETERMINATION FOR TURBULENT PIPE FLOW COMPUTATION

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概要

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• Although the applications of higher-order turbulent models for complex turbulent flow computation have been widely recognized and becomes popular, slow convergence (or divergence) of the turbulent computations still hinders the use of advanced turbulence models. In most works, the governing equations with turbulent property equations are discretized by finite difference method and the use of SIMPLE or PISO algorithm is very popular. The under relaxation factor plays an important role in the convergence of these problems. The decreasing of the under relaxation factors cause the slow convergence for the flow field, the increasing of the under relaxation factors indeed accelerate the obtaining of the flow field in some case, but always cause divergence for the computation. In the present study, we propose a method to determine the values of the under relaxation factors so that faster convergence can be achieved. The new method adopts the concept from the iteration method of Bi-CGSTAB algorithm. The scheme updates the solution vectors such that the 2-norm minimized residuals of the governing equations can be obtained. In the present work, we will derive an expression according to Bi-CGSTAB method for steady state flow so that the under relaxation factors of the computation cell at a specific iteration step can be obtained to enforce the residual of the conservative properties of the computational cell to a minimum value, say zero. The turbulent pipe flow and the heat transfer characteristics are computed to demonstrate the effectiveness of the present method and different degrees of difficulty on convergence behavior should be demonstrated for different turbulence models (1) Chien's low Reynolds number form (2) Launder-Sharma's model (3) Lin's model and (4) Durbin's κ-ε-ν^2 model. The numerical results indicate that the relaxation factors determined by the Bi-CGSTAB method indeed accelerate the convergence rate for the computation of turbulent pipe flow.

• 一般社団法人日本機械学会の論文

著者

• Tsai Wen

  Department Of Management Information System Far East College

• LIN W.

  Department of Electrical Engineering, National Cheng Kung University

• Chieng C.

  Department of Engineering and System Science, National Tsing-Hua University

• Chieng C.

  Department Of Engineering And System Science National Tsing-hua University

• Tsai Wen

  Department Of Electronics Engineering And Institute Of Electronics National Chiao-tung University

• Lin W.

  Department Of Electrical And Computer Engineering National University Of Singapore

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