Mutual Interaction Between Turbulent/Laminar Separation Vortex and Cavitation Bubble

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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.