平面压气机叶栅通道分离流动高精度直接数值模拟

采用高精度有限差分格式直接求解二维Navier-Stokes方程组，数值模拟V103平面压气机叶栅分离流动,数值结果表明:在瞬时流场中,吸力面后部发生流动分离,在分离区前端存在大尺度分离涡,分离涡下游是由二次涡和脱落涡交替形成的涡串,直至叶片尾缘,形成以脱落涡为主结构的尾迹;在时均流场中,吸力面后部存在短分离泡,分离区压力分布存在明显压力平台。与逆压力梯度下平板边界层分离流动相比,瞬时和时均流场结构相似;叶栅通道内无量纲涡脱落频率是前者的两倍。与文献计算结果对比表明:叶片表面压力分布除分离区外吻合很好;非定常计算所得分离区轴向长度比定常计算大41%。在分离区内三个二阶统计量均达到最大值,表明流场强非定常性集中在分离区。

High order direct numerical simulation of compressor cascade ,channel separated flow

Separated flow of V103 compressor cascade was numerically simulated by directly solving the two-dimensional Navier-Stokes equations using high order finite difference schemes.The numerical results showed that in the transient flowfield, there existed an obviously separated flow at the rear of the suction side with a large-scale separated vortex followed by alternative second vortex and shedding-vortex forming the wake. In the time-averaged flowfield, a short separated bubble was formed and identified by the pressure platform of the pressure distribution on the suction side of the blade. Compared with two-dimensional flat separated flow, both the transient and time-averaged flowfields were similar with the same vortex structure. However, the non-dimensional vortex-shedding frequency of cascade was twice times of the flat flow. The time-averaged pressure distribution on the blade surfaces coincided with the numerical results in the references except the separation area. Compared with the reference results, the present separated flow axial length was 41% bigger than the former. At last, second order statistics of pulse velocity in the separation area were bigger than those in the wake, indicating the unsteadiness of the separated flow.