绕空化器回转体通气空泡流态特征实验研究

Experimental investigation of the ventilated cavitating flow around the axisymmetric body of a disk cavitator

为了研究通气空泡流态的转变机制,本文采用高速摄影技术对绕空化器回转体通气空泡的流场结构进行了观测,分析了通气率和空化器尺寸对通气空泡流态的影响。结果表明:随通气率的增大,空泡的发展过程整体可分为3个特征阶段,即快速增长阶段、缓慢增长阶段和相对稳定阶段。通气率的增大引起空泡不对称性加剧,空泡尾部泄气方式由回射流泄气逐渐转变为双涡管泄气,空泡的形态由泡沫状逐渐发展为完全透明的稳定超空泡。相比于小尺度空化器模型,相同傅汝德数条件下,大尺度空化器模型下形成连续透明空泡的最小通气量增大,各空泡形态分布区域和空泡发展趋势也发生改变。

To investigate the transition mechanism of a ventilated cavitating flow pattern,high-speed flow visualization technology was used to observe the process and structure of the ventilated cavitating flow around the axisymmetric body of a disk cavitator.The effects of the air entrainment coefficient and the cavitator diameter on the ventilated cavitating flow pattern were studied.The results show that with the increase of the air entrainment coefficient,the cavity development process can be divided into three stages:the rapid growth stage,the slow growth stage,and the relatively stable stage.The increase of the air entrainment coefficient intensifies the asymmetry of the cavity,and the air leakage mode at the cavity tail gradually changes from re-entrant jet flow mode to twin-vortex tube mode.Meanwhile,a ventilated flow pattern gradually develops from a foamy cavity to a completely transparent and stable supercavity.Compared with the small-scale cavitator model at the same Froude number,the minimum air entrainment rate for forming a continuous transparent cavity increases in the large-scale cavitator model.Thus,the distribution area of the ventilated cavitating flow pattern and the growing trend of the cavity also change.