An in vitro experiment has been performed to demonstrate the presence of squeeze flow in mechanical valves with a seat stop interacting with the leaflet near the major orifice at the instant of valve closure. Using high speed video camera and strobe light at 16,000 pulses/sec, radial motion of cavitation bubbles due to the “squeeze flow” effect is observed. However, in valves with no seat stops in the major orifice region, bubbles of duration longer than the cavitation bubbles were observed. These studies further demonstrate the importance of the local flow dynamics with mechanical valves at the instant of valve closure and its importance on the flow induced stresses on the valve structures as well as on the formed elements of blood.

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