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Mutual Interaction Between Turbulent/Laminar Separation Vortex and Cavitation Bubble

湍流/层流分离涡与空化气泡之间的相互作用

基本信息

批准号：
05650182
负责人：
SATO Keiichi
金额：
$ 1.47万
依托单位：
KANAZAWA INSTITUTE OF TECHNOLOGY
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1993
资助国家：
日本
起止时间：
1993 至 1994
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-05650182/
关键词：
Cavitation Separated Flow Vortex Interference Problem Bubbly Flow Critical Regime Turbulent Transition Bluff Body

项目摘要

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.

针对空化现象，由于空化气泡在流动中的出现，对流动特性的影响是一个尚未解决的问题。本文从海崖体这一典型旋涡形成结构的绕流角度出发，通过实验研究了空化泡对流动特性的干扰机理。1995年，我们制作了各种尺寸的圆柱体和三角形圆柱体，以及带分流板的圆柱体。还制作了试验圆柱体，以考察端板的作用。在不同的含气量、流速和试验段压力下，测量了空泡发生点、空泡类型和空泡冲击脉冲。从结果来看，由于气穴现象产生的气泡的影响，圆柱周围的流动在很大程度上发生了质的变化。1994年，采用了基于向流动中注入染料的流动可视化技术来可视化流动模式，这样，双-峰值空化过程是由层流分离模式向湍流分离模式转变引起的。从圆柱体底压的测量来看，气穴引起的流动分离模式的转变会引起旋涡强度的变化，从而抑制气穴本身的发生。其次，明确了隔板效应减弱了旋涡的干扰，从而减少了空化的发生。第三，针对旋涡空化现象，成功地研制了气泡出现与冲击力之间的瞬时测量系统，明确了这些问题的特点。