绕水翼空化流场旋涡特性分析

Vortex Characteristics in Cavitating Flows Around a Hydrofoil

为了深入了解绕水翼空化流动机理,利用数字式粒子图像测速(DPIV)系统,并辅以高速摄像机,对绕水翼流动进行了观测.观测结果表明:空化的发展对整个流场的涡量变化起决定作用.无论在空化还是无空化流场中,涡量主要集中在自水翼前后缘开始的剪切层所在区域,并形成涡带,且上下涡旋向相反;随着空化数的降低,空化区域的流场混合得更为均匀,从而使涡量的峰值逐渐减小;上下涡带逐渐靠拢,并向后延伸、拉直,同时下涡带的起始位置向后推移.

To explore the development of vorticity distribution in cavitating flow field, the cavitating flow fields around a hydronautics foil were measured by means of a digital particle image velocimetry （DPIV） system and a high-speed video camera. The results show that the changes of vorticity distributions in the flow fields depend on the development of cavitation structures. Most vortices can be seen near the shear-layer area in all cases, and behave as vorticity bands. With the decreasing of cavitation numbers, the vorticity value lowers since there is no large grad of the velocity in the cavitation area. The upper and lower vorticity bands approach each other and extend downstream, while the inceptive position of the lower one moves downstream.