The effect of tip angle on cavitation potential during closure of a bileaflet prosthesis model.
OBJECTIVE
Mechanical heart valve (MHV) cavitation has been widely investigated by negative pressure transient (NPT) measurements. Whilst NPT is believed to be the cause of cavitation as the valve occluder approaches its fully closed position, some valves are also more prone to cavitation initiation. The study aim was to determine the effect of tip angle on the occluder trailing edge for the MHV closure flow field and cavitation potential.


METHODS
Three pairs of 1:1 transparent bileaflet models, with different tip angles (30 degrees, 60 degrees and 90 degrees), were used in a pulsatile mock loop. Particle image velocimetry (PIV) and micro-tip pressure catheters were applied respectively for the closure flow and transient pressure investigations. A mechanism was designed to enable triggering when the valve occluder approached its closing position.


RESULTS
The transient pressure showed two maximum pressure drops, the magnitudes of which differed with various angle designs. A series of flow fields with continuously narrowing gap channels was captured. Different flow features were demonstrated for the three valve models.


CONCLUSIONS
The tip angle design on the occluder trailing edge affected both the NPT magnitude and MHV closure flow field. The 60 degrees and 30 degrees valves had higher vorticity and fluid deceleration rate within the squeeze flow and occluder sudden stop respectively, which correlated with their larger pressure drops for the first and second NPT peaks.
Zhang
Pei
P
School of Mechanical & Automation Engineering, Shanghai Institute of Technology, China.
Yeo
Joon Hock
JH
Qian
Ping
P
Hwang
Ned H C
NH
D001783:Blood Flow Velocity / Q000502:physiology*; D019544:Equipment Failure Analysis; D006350:Heart Valve Prosthesis; D018056:Hemorheology; D006801:Humans; D008955:Models, Cardiovascular; D011474:Prosthesis Design; D011673:Pulsatile Flow / Q000502:physiology*; D017725:Ventricular Pressure / Q000502:physiology