| Summary: | 碩士 === 國立交通大學 === 土木工程系所 === 103 === This study utilized three different diameter pipes filled with water, to generat different size single cavitation bubbles by changing the U-shape platform’s angular velocity. When angular velocity was increased, the pressure at the center of the rotation in the pipe was decreased. The single bubble was collapsed by triggering a pressure pulse under different distance between bubble and solid boundary. During the experiment, the study analyzed the zone which has low velocity and high pressure after bubble collapse.
A high speed camera (CCD) which can take 8000 images in one second was adopted to take sequential images of the bubble collapse process and calculated velocity fields with Particle Image Velocity (PIV) theory.
According to the surface tension and attraction by the solid boundary, the study observed the Rayleigh-Taylor phenomenon (caused by gravity), Kelvn-Helmholtz vortex phenomenon (caused by shock wave), Richtmyer-Helmholtz instibility phenomenon (caused by shear stress) when bubble collapsed.
Experimental results show when the distance parameter equals to 2 (which means the bubble exactly far from the solid boundary a diameter away) smallest pressure and biggest vortex value can be observed. So it would make less damage due to bubble collapse by controlling the distance between the bubble and the rigid boundary in the pipe. In addition, the complex phenomena of the collapsing flows of single cavitation bubble were presented and analyzed in this study.
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