Mutual Interaction Between Turbulent/Laminar Separation Vortex and Cavitation Bubble

对于空化现象，流动中由于空化气泡的出现对流动特性的影响是一个尚未解决的问题。本文从典型涡形成结构之一的钝体流动的角度出发，通过实验明确了空化气泡与流动特性之间的干涉机理。此外，还讨论了随着流场特性的变化，流体动力特性与冲力之间的关系。1995年，制作了各种尺寸的圆形和三角形圆柱体，以及带有分裂板的圆形圆柱体。为了检验端板的影响，还制作了试验筒。在不同空气含量、流速和试验段压力下，测量了气泡发生点、气泡类型和空化冲击脉冲。结果表明，由于气泡的产生和空化的影响，在很大程度上改变了圆柱周围的流动。1994年，为了将流型可视化，采用了基于在流动中注入染料的流动可视化技术，使双峰空化过程的流动特性由层流分离过渡到湍流分离。从圆柱底压的测量来看，空化引起的流动分离型的转变引起了涡强度的变化，从而抑制了空化本身的发生。其次，指出了劈裂板效应减弱了涡的干涉，从而减少了空化现象的发生。第三，针对涡旋空化问题，成功建立了气泡出现与冲力之间的瞬时测量系统，明确了涡旋空化问题的特征。

For cavitation phenomena one of unsolved problems in the effect of flow characteristics due to occurrence of cavitation bubbles in the flow. In the present research the interference mechanism between cavitation bubbles and the flow characteristics was experimentally made clear from the viewpoints of flows about a bluff body which is one of typical vortex formation structures. In addition, the relation between hydrodynamic characteristics and impulsive force are discussed with the change of the flow field characteristics.In 1995, circular and triangular cylinders of various sizes were made as well as a circular cylinder with a splitter plate. The test cylinder was also made for examining the effect of the end plate. Bubble occurrence points, bubble types and cavitation shock pulses were measured under various air contents, flow velocities and test-section pressure. From the results, the flowabout a circular cylinder was qualitatively changed to a large extent due to the effect of the bubble occurrence with cavitation.In 1994, the flow visualization technique based on the dye injection into the flow was used in order to visualize the flow pattern, so that the flow characteristics of the double-peak cavitation process was caused by the transition from the laminar separation to the turbulent separation pattern. From the measurement of the base pressure of a circular cylinder, the transition of flow separation pattern due to cavitation creates the change of vortex strength and so repress the occurrence of cavitation itself. Next it was made clear that the splitter-plate effect weakens the interference of vortices and so reduces the occurrence of cavitation. Third, for the vortex cavitation the instantaneous measurement system between the bubble appearance and the impulsive force was successfully made to make clear the characteristics of these problems.