二维喷管分离流线性/非线性湍流模式的研究

Study of separated flow in a diffuser using linear and nonlinear eddy-viscosity turbulence models

采用三个线性和七个非线性涡粘性湍流模式,对二维非对称喷管中的不可压缩分离流进行了研究。通过将数值计算结果和实验结果进行比较,对有关的湍流模式进行了评估和分析。计算结果表明,非线性模式的模化系数与平均流动应变不变量以及旋转不变量有关,反映了湍流的各向异性,比线性模式优越得多。另外,所有线性/非线性涡粘性湍流模式不能够捕捉流动的非定常分离过程。

An investigation into the predictive performance of linear and nonlinear eddy-viscosity turbulence models for the incompressible separated flow in a two-dimensional asymmetric diffuser is presented. Three linear models are: k-ε model of Launder & Sharma (1974), k-ω model of Wilcox (1988), and SST model of Menter (1994). Seven nonlinear models under low-Re k-ε framework are: the quadratic models (Wilcox & Rubesin (1980), Shih, Zhu & Lumley (1993), Shih, Zhu & Lumley (1995)) and the cubic models ( Craft, Launder & Suga (1996), Lien & Leschziner (1996), Apsley & Leschziner (1998), Shih et al. (1997) ). Comparisons are made with experimental data in term of profiles of mean velocity and components of the Reynolds stress tensor, as well as surface pressure and skin friction. The computational results show that turbulence models with strain/vorticity-dependent coefficients offer tangible improvements. The poor performance of all models near the inclined wall at the first corner reflects the inability of eddy viscosity models to capture the unsteady separation process.