利用二次渦旋粘滯紊流模式之非結構性網格計算

Abstract

在本論文中引用SIMPLE壓力修正法，用有限容積法來離散統御方程式﹐並採用非交錯式之非結構性網格。 紊流模式採用Speziale與Rubinstein的二次非線性紊流模式求解(1)完全發展流(2)背階流場(3)軸對稱管道流場﹐並將結果與線性k-ε模式和實驗值比較。由結果可以發現對於平均速度、剪應力與紊流動能﹐二次模式與線性k-ε模式有相近的結果﹐而二次模式對於紊流正向應力與接觸長度﹐能得到比線性模式更好的結果。與實驗值相比﹐兩種模式對於迴流區附近的平均速度與接觸長度預測的結果都比較差。

In this thesis, SIMPLE algorithm were applied to numerical simulation with Unstructured grid. Numerical simulations were applied to several turbulent flows, including:(1)Fully developed channel flow﹐(2)flow through a back-step, (3)flow through a expansion pipe with various expansion angle, using (I)standard linear k-εmodel(II)second order nonlinear models, Including Speziale’s model and Rubinstein’s model. The predicted mean and turbulent results were compared with experimental results. Predictions of mean velocity, shear stress, and turbulent kinetic energy by Linear model and Nonlinear models are comparable. Nonlinear models predict better results in turbulence intensity and reattachment length. Compared with experimental results, all model performing poorly in the separated regions.