水翼空化瞬态特征与空化冲击关系试验研究

Experimental investigation on the relation between instantaneous cavitation behavior and cavitating impact on a hydrofoil

舰船在高航速运行工况下空化非定常演化过程产生的冲击,是空化激励产生异响甚至空蚀的根源。实际空化流动是包含多尺度流动结构的复杂过程,涉及空化的脱落、破碎、合并以及溃灭等多重影响因素,目前对于空化冲击形成机制的认识及判别尚不清晰,制约了空化冲击控制措施的发展。针对上述问题,本文以扭曲水翼为对象,首先采用水翼物面蓝油涂层方法确认空化冲击的主要区域,然后利用高速相机和水听器开展空化图像与脉动信号在时域上的同步测试,分析水翼片空化脱落形成云空化过程中物面空化冲击与空化瞬态结构特征之间的关系。结果表明,对于典型片空化形成云空化的过程,高频高幅值的空化冲击是由片空化脱落后形成的云空化结构局部整体溃灭回弹现象引起,且在瞬时产生强烈的压力脉动。这一认识为工程上对空化冲击的判别和控制提供了依据。

For high speed ships,impact produced by cavitation is the source of abnormal noise and even cavi⁃tation erosion.However,cavitation is actually a complex process containing multi-scale structures coupled with many influencing factors such as cavitation shedding,cavity breaking,local merging and collapse,it is still a tough work to make clear the mechanism for the impact in full-scale cavitating flow and to control its effects.In this paper,cavitation around a twisted hydrofoil was selected to clarify the relation between the cav⁃itating impact and instantaneous cavitation behavior,using a synchronized system composed of a high speed camera and a hydrophone to make the measurements synchronously in time domain,and a soft paint layer to show the cavitation impacted region.The results indicate that for a typical sheet-to-cloud cavitating flow,the high magnitude impulse composed of high frequency component is related to the local collapse and rebound of cloud cavitation shedding from sheet cavity.The study provides the physical understanding and control of cavitation impact in the industrial field.