SA一方程湍流模型参数影响分析与辨识

SA(Spalart-Allmaras)一方程湍流模型是目前工程湍流计算中主要采用的湍流模型之一。首先,针对某典型战斗机的小攻角、中等攻角、大攻角流动工况,利用均匀试验设计方法分析SA一方程模型中8个参数取值对上述工况下飞机升力和阻力系数计算结果的影响规律;然后,建立工程湍流模型参数的辨识方法,并将其用于该战斗机大攻角工况下湍流模型参数cb1值的辨识调整。结果表明:不同工况下,湍流模型参数对计算结果的影响规律不同;在附着流状态下,对升力和阻力影响较大的参数是cv1和cb1;在中等攻角和较大攻角下,对升力和阻力影响较大的参数是cb1;适当减小参数cb1的取值后,升力和阻力系数的计算结果有较明显的改善,这可能与飞机大攻角分离流场中涡粘系数和剪切应力的发展与自由剪切流存在一定差异有关。

Influence analysis and estimation of SA one-equation turbulence model parameter

Spalart-Allmaras(SA) one-equation turbulence model has been prevailing used in the numerical simulation of engineering turbulence flows. In this paper, the flow situations of small incidence, middle incidence, large incidence of a typical fighter are concerned. And the influences of eight model parameters in SA turbulence model on the calculated turbulent flow fields are analyzed by using the uniform design of experiments. The results show that under different flow situations do the model parameters exhibit different influences on calculated results of lift and drag coefficients. For attached flow of small incidence, the influences of the parameters cv1 and cb1 are much greater than other parameters, and for middle incidence and large incidence, the parameter of largest influence is cb1. Then the turbulence model parameter estimation method is developed and utilized for the estimation of cb1 value for large incidence case. It is found that when the parameter value of cb1 decrease moderately, the calculated lift and drag coefficients agree with the experimental results much better. This could be attributed to that the conventional value of the model parameters are calibrated from free shear flow but there exists some difference in the development of eddy-vicosity and shear stress between the large incidence separated flow and the free shear flow.