非定常空化涡旋结构演化及压力波机制的研究

Investigation on transient unsteady cavitation vortex structures and the pressure wave dynamics

压力波机制是空化流动机制的一种,压力波的产生和传播是空化不稳定的重要来源。基于可压缩流体求解器和分离涡模拟(detached-eddy simulation,DES)研究了三维水翼空化流动。结果表明,压力波是由先前脱落的云空泡溃灭产生的,其传播过程会导致片状空泡的收缩和水翼表面高压力脉冲。压力波的产生会强烈扰乱涡旋的运动,水翼表面上的稳定涡旋结构被卷起,并且被小尺度涡旋结构所替代。采用动力学模态分解(dynamic mode decomposition,DMD)方法分析流场特征,压力波效应和附着片状空泡的演变占据了流场的主要能量。

The pressure wave mechanism is one of the cavitation flow mechanisms.The generation and propagation of pressure wave is an important source of cavitation instability.In the paper,three-dimensional hydrofoil cavitation flow was studied based on a compressible fluid solver and detached-eddy simulation(DES).The results show that the pressure wave is generated by the collapse of the cloud cavity which has formerly fallen off.The propagation process of the pressure wave causes the shortening of the sheet cavity and the high-pressure pulse on the surface of the hydrofoil.The generation of pressure wave strongly disturbs the motion of the vortex.The stable vortex structure on the surface of the hydrofoil is then rolled up and replaced by the small-scale vortex structure.The dynamic mode decomposition(DMD)method was used to analyze the characteristics of the flow field.The first-order mode represents the basic framework and main characteristics of the flow field.The pressure wave effect and the evolution of attached sheet cavity occupy the main energy of the flow field.