二維夾縫產生之脈衝渦流特性探討

淡江大學機構典藏 > 工學院 > 水資源及環境工程學系暨研究所 > 學位論文 > Item 987654321/102728

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题名:	二維夾縫產生之脈衝渦流特性探討
其它题名:	The characteristics of impulsive vortex formation from a 2-D gap
作者:	陳方璞;Chen, Fang-Pu
贡献者:	淡江大學水資源及環境工程學系碩士班盧博堅;Lu, Po-Chien
关键词:	回流;渦流;穴蝕;retrograde flow;vortex;cavitation
日期:	2014
上传时间:	2015-05-04 10:02:53 (UTC+8)
摘要:	許多的研究表示，心臟疾病是現代人死亡原因前幾名。穴蝕氣泡當機械心瓣關閉時瞬間形成，這會破壞血球細胞與心瓣完整性，是一個眾所周知被廣泛研究的現象。在MHV關閉期間，擠壓流通過狹縫生產噴射流並在下游捲起渦旋。同樣的，高速滲漏間隙流可能捲起渦旋。向前的流場與尾流相互作用，在擋水板後面回彈也可能會導致渦流的形成。利用固定葉片間的夾縫模擬血液回流時通過夾縫產生出高速的噴射流。此研究我們使用PIV仔細測量在MHV中迴流流場的渦流結構。我們測量渦流半徑，最大切向速度，循環強度和計算壓降，這使我們能夠量化評估渦流在MHV穴蝕中的形式。若渦流中心壓低低於飽和蒸汽壓(-740mmHg)即能發生穴蝕現象，本實驗所量測出來的最大壓降為172.042mmHg，並不會有穴蝕現象產生。 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.
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