The characteristics of impulsive vortex formation from a 2-D gap

• Main Authors: Fang-Pu Chen, 陳方璞
• Other Authors: Po-Chien Lu
• Format: Others
• Language: zh-TW
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/84340292339385408419

碩士 === 淡江大學 === 水資源及環境工程學系碩士班 === 102 === A lot of studies have shown that heart disease plays an important role of death of modern people. The instantaneous formation of cavitation bubbles at mechanical heart valve closing, which subsequently damage blood cells and the valve integrity, is a well-known and widely studied phenomenon. During MHV closure, squeeze flow through the gaps can produce jet flows that roll up downstream into vortices. Similarly, high-speed leakage flow may roll up into vortices. Interactions between the forward flow and fluid trailing behind the occluder after rebound may also result in vortex formation. We use the fixed leaflets simulated blood retrograde flow through the gap to produce a high-speed jet. We have carefully measured the vortex structure in the MHV regurgitant flow field using PIV. We measured the vortex radius, maximum tangential velocity, circulation strength, and calculated pressure drop, which allows us to quantitatively evaluate the vortices in MHV cavitation formation. The maximum pressure drop in the vortex center is 172.042mmHg. Since cavitation formation requires the locale pressure to drop below vapor pressure (about -740 mmHg), Our results clearly showed that vortex formation with a pressure drop of this order of magnitude cannot provide significant contribution to mechanical heart valve cavitation.