绕三维水翼云状空化现象的实验研究

Experimental study on unsteady cavitation flows around three-dimensional hydrofoil

为了研究云状空化阶段空穴发展和脱落的机理,采用实验的方法对绕三维水翼云状空化流动进行了研究。实验在高速水洞中进行,采用高速摄像技术研究了不同空化阶段的空穴形态,并测量了翼型所受的升阻力,并对上述数据进行了频谱分析。结果发现:在云状空化阶段,观测到空穴的产生-发展-脱落-溃灭的准周期性变化;并捕捉到空泡脱落时附着在翼型前端的U型空穴和翼型方向上不同强度的反向射流;空泡由翼型中前部开始呈漩涡状脱落。将升力通过FFT变换得到了对应的频谱图,得到空穴脱落的频率为24.3Hz。

In order to study the mechanism of the cavity generation,shedding in cloud cavitation regime,the characteristics of unsteady cavitating flows around a three-dimensional hydrofoil are investigated by experimental methods.Experiments on a hydrofoil are carried out in a rectangular test section of a cavitation tunnel,a high-speed video camera is used to visualize the cavitating flows,the drag and lift forces under different cavitation conditions are measured and the spectral analysis for the measured data is conducted.The results show that in unsteady cavitation a quasi-periodic process corresponding to the occurrence-development-shedding-seasing of cavity is observed and the U-shaped cloud cavity and different intensity reentrant jet in spanwise direction towards the mid-span region are captured,the cavities are broken off from the mid-span region near the leading edge of the hydrofoil and become the vortical cloud cavities with the large-scale U-shaped structure.The spectral analysis for the lift and drag forces is conducted through Choi-Williams transformation,and the shedding frequency is 24.3Hz.