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    Title: Cavitation Phenomena in Mechanical Heart Valves: Studied by Using a Physical Impinging Rod System
    Authors: Lo, Chi-Wen;Chen, Sheng-Fu;Li, Chi-Pei;Lu, Po-Chien
    Contributors: 淡江大學水資源及環境工程學系
    Keywords: Cavitation;Mechanical heart valve;Physical model;Squeeze flow;Water hammer;Vortex
    Date: 2010-10
    Issue Date: 2011-10-23 02:04:53 (UTC+8)
    Publisher: New York: Springer New York LLC
    Abstract: When studying mechanical heart valve cavitation, a physical model allows direct flow field and pressure measurements that are difficult to perform with actual valves, as well as separate testing of water hammer and squeeze flow effects. Movable rods of 5 and 10 mm diameter impinged same-sized stationary rods to simulate squeeze flow. A 24 mm piston within a tube simulated water hammer. Adding a 5 mm stationary rod within the tube generated both effects simultaneously. Charged-coupled device (CCD) laser displacement sensors, strobe lighting technique, laser Doppler velocimetry (LDV), particle image velocimetry (PIV) and high fidelity piezoelectric pressure transducers measured impact velocities, cavitation images, squeeze flow velocities, vortices, and pressure changes at impact, respectively. The movable rods created cavitation at critical impact velocities of 1.6 and 1.2 m/s; squeeze flow velocities were 2.8 and 4.64 m/s. The isolated water hammer created cavitation at 1.3 m/s piston speed. The combined piston and stationary rod created cavitation at an impact speed of 0.9 m/s and squeeze flow of 3.2 m/s. These results show squeeze flow alone caused cavitation, notably at lower impact velocity as contact area increased. Water hammer alone also caused cavitation with faster displacement. Both effects together were additive. The pressure change at the vortex center was only 150 mmHg, which cannot generate the magnitude of pressure drop required for cavitation bubble formation. Cavitation occurred at 3–5 m/s squeeze flow, significantly different from the 14 m/s derived by Bernoulli’s equation; the temporal acceleration of unsteady flow requires further study.
    Relation: Annals of Biomedical Engineering 38(10), pp.3162-3172
    DOI: 10.1007/s10439-010-0070-y
    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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