大攻角下仿生水翼非一致流场及空化数值分析

Numerical analysis of non-uniform flow field and cavitation of bionic hydrofoil at high angle of attack

基于座头鲸鳍肢造型的仿生水翼在大攻角下具有优越的流动控制和空化性能,为研究大攻角下仿生水翼绕流机理,该文基于LES和ZGB模型对18°攻角下4L仿生水翼的空化流场进行了数值模拟,结果表明:大攻角下,仿生水翼表面存在非一致流场,其产生于分离涡的展向扩展及凸峰附着流的分割作用,根据分离涡状态将水翼表面流场分为扩张区和收缩区。收缩区内空泡形态较稳定,脱落频率小,存在由附着流汇合引起的小范围回射流;扩张区内存在“U”形空泡及涡结构,其产生于流向涡与回射流的共同作用;非一致流场下水翼表面呈现一定的压力脉动特征,水翼后部压力脉动较小而分区边界处压力脉动较大。

Based on the shape of humpback whale fin,the bionic hydrofoil has superior flow control and cavitation performance at high angle of attack.In order to study the flow mechanism of bionic hydrofoil at high angle of attack,the cavitating flow field of 4L bionic hydrofoil at 18°angle of attack is numerically simulated based on LES and ZGB model.The results show that there is a non-uniform flow field on the surface of bionic hydrofoil at high angle of attack,which is caused by the spanwise expansion of separated vortex and the division function of the attached flow.According to the state of separated vortex,the flow field on the hydrofoil surface is divided into expansion region and contraction region.The cavitation shape in the contraction region is relatively stable,the shedding frequency is small,and there is a small range of return jet caused by the convergence of attached flow.There are U-shaped cavitation and vortex structures in the expansion region,which are generated by the interaction of the streamwise vortex and the return jet.In the non-uniform flow field,the pressure fluctuation is small at the rear of hydrofoil and large at the boundary of partition.