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    Title: Role of vortices in cavitation formation in the flow at the closure of a bileaflet mitral mechanical heart valve
    Authors: Li, Chi-pei;Chen, Sheng-fu;Lo, Chi-wen;Lu, Po-chien
    Contributors: 淡江大學水資源及環境工程學系
    Keywords: Mechanical heart valve;Vortex cavitation;Particle image velocimetry;Rankine vortex
    Date: 2012-03
    Issue Date: 2012-05-03 17:07:49 (UTC+8)
    Publisher: Tokyo: Springer Japan KK
    Abstract: Bubble cavitation occurs in the flow field when local pressure drops below vapor pressure. One hypothesis states that low-pressure regions in vortices created by instantaneous valve closure and occluder rebound promote bubble formation. To quantitatively analyze the role of vortices in cavitation, we applied particle image velocimetry (PIV) to reduce the instantaneous fields into plane flow that contains information about vortex core radius, maximum tangential velocity, circulation strength, and pressure drop. Assuming symmetrical flow along the center of the St. Jude Medical 25-mm valve, flow fields downstream of the closing valve were measured using PIV in the mitral position of a circulatory mock loop. Flow measurements were made during successive time phases immediately following the impact of the occluder with the housing (O/H impact) at valve closing. The velocity profile near the vortex core clearly shows a typical Rankine vortex. The vortex strength reaches maximum immediately after closure and rapidly decreases at about 10 ms, indicating viscous dissipation; vortex strength also intensifies with rising pulse rate. The maximum pressure drop at the vortex center is approximately 20 mmHg, an insignificant drop relative to atmospheric vapor pressures, which implies vortices play a minor role in cavitation formation.
    Relation: Journal of Artificial Organs 15(1), pp.57–64
    DOI: 10.1007/s10047-011-0612-6
    Appears in Collections:[水資源及環境工程學系暨研究所] 期刊論文

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