Role of vortices in cavitation formation in the flow at the closure of a bileaflet mitral mechanical heart valve

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, w...

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Bibliographic Details
Published in:Journal of artificial organs 2012-03, Vol.15 (1), p.57-64
Main Authors: Li, Chi-Pei, Chen, Sheng-Fu, Lo, Chi-Wen, Lu, Po-Chien
Format: Article
Language:English
Subjects:
Biomedical Engineering and Bioengineering
Cardiac Surgery
Heart Valve Prosthesis
Humans
Indexing in process
Medicine
Medicine & Public Health
Models, Cardiovascular
Nephrology
Original Article
Pressure
Prosthesis Design
Pulsatile Flow
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Summary: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.
ISSN:1434-7229
1619-0904
DOI:10.1007/s10047-011-0612-6