引入压力梯度的针对角区分离流动的Spalart-Allmaras模型的改进

针对Spalart-Allmaras（S-A）模型在角区分离计算中的问题，将无量纲的压力梯度引入其涡黏性输运方程的生成项，得到了改进的S-A模型.通过对两套含角区分离的低速压气机叶栅进行验证计算发现:与实验结果相比，原始S-A模型所得的分离区偏大，分离区内壁面压力偏低；而改进模型得到了与实验一致的分离区尺寸以及吸力面、压力面压力系数分布等结果.针对S-A模型涡黏性生成项和耗散项的分析表明:引入的无量纲压力梯度有效的识别了角区分离，在分离区内改变了涡黏性的生成、耗散关系，增大了涡黏性，从而缩小了计算所得分离区，同时在主流区保留了原始S-A模型的计算结果，进而带来了良好的改进效果. 

Modification of Spalart-Allmaras model with pressure gradientaiming for corner separation flow

For the problem in predicting the corner separation, the Spalart-Allmaras (S-A) model was modified by introducing a normalized pressure gradient into the production term of the eddy viscosity in the model equation. Through the calibration in two series of low-speed compressor cascade cases with corner separation, it was found that compared with the experimental results, the original S-A model got a stronger corner separation and lower wall pressure in the separation zone, while the modified model''s results were closer to the experience in the size of the separation zone, the pressure coefficient on the suction and pressure sides, etc. The analysis on the production and dissipation terms of the eddy viscosity in S-A model indicates that the normalized pressure gradient introduced to the production term can recognize the separation zone effectively. It can also change the transportation of the eddy viscosity of the model and enhance the eddy viscosity in the corner separation, bringing about a smaller separation zone, while the prediction in the main flow area in the modified S-A model remains the same as the original S-A model. Thus a better prediction is got.