涡流发生器对动态失速影响的模拟研究

Simulation Study on the Effect of Vortex Generators on Dynamic Stall

基于风力机专用翼型DU91-W2-250直叶片段,采用延迟分离涡模拟(Delayed detached-eddy simulation, DDES)与k-ω SST两种CFD模拟方法,研究了涡流发生器(Vortex generators,VGs)对动态失速的影响,并对两种模拟方法的表现进行了比较。结果表明:动态失速下,光滑叶片段的分离与重新附着均出现延迟;加VGs后,上仰阶段叶片段的气动分离更加延迟,下俯阶段叶片段上表面附着流动重建的更早,气动力的迟滞现象得到明显改善。VGs对DU91-W2-250叶片段增升减阻的效果明显,其中最大升力系数增加10%,周期平均升力系数增加17.9%,最大阻力系数减少56.3%,周期平均阻力系数减少40.3%。DDES模型能更细致地反映VGs对动态失速抑制作用下叶片段表面复杂流动分离现象,k-ωSST模型则难以捕捉小尺度涡结构,模拟得到的涡结构展向呈二维分布。

The effects of vortex generators(VGs) on dynamic stall are investigated based on a blade segment using the airfoil of DU91-W2-250. The investigation is numerically performed by two simulation approaches, i.e. Delayed detached-eddy simulation(DDES) and k-ω SST, and their results are compared. The results show that of airflow separation and reattachment within the dynamic stall process are delayed on the smooth blade surface. After adding VGs, the airflow separation is delayed at the pitch up stage, the reattachment of air flow on the up surface becomes earlier when the blade is pitching down, and the aerodynamic hysteresis is obviously improved. The magnitudes of lift increased and the drag reduced by VGs of are substantial. In detail, the maximum lift coefficient of DU91-W2-250 blade segment is increased by 10%, the average value is increased by 17.9%;the maximum drag coefficient is decreased by 56.3%, and the average value is decreased by 40.3%. DDES model can demonstrate clearly the complex flow separation occurred in dynamic stall as it is under the effect of VGs, while the k-ω SST model hardly provides a deep insight into the small-scale vortices structure and which furthermore shows two-dimensional characteristics.