Publications (3)3.59 Total impact
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Article: The effect of tip angle on cavitation potential during closure of a bileaflet prosthesis model.
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ABSTRACT: 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. 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. 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. 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.The Journal of heart valve disease 08/2007; 16(4):430-9. · 0.81 Impact Factor -
Article: Shear stress investigation across mechanical heart valve.
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ABSTRACT: The particle image velocimetry technique was used to study the shear field across a transparent mechanical heart valve model in one cardiac cycle. Shear stress was continuously increased until peak systole and high turbulent stress was observed at the orifice of the central channel and also around the occluder trailing tips. The peak Reynolds shear stress was up to 500 N/m at peak systole, which was higher than the normal threshold for hemolysis.ASAIO journal (American Society for Artificial Internal Organs: 1992) 53(5):530-6. · 1.39 Impact Factor -
Article: Development of squeeze flow in mechanical heart valve: a particle image velocimetry investigation.
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ABSTRACT: Fluid between the reducing flow channel of the valve occluder and the orifice wall tends to be squeezed out of the flow channel, causing a high-speed flow. The squeeze flow is accompanied by a sharp local pressure drop, which may result in potential cavitation phenomenon in a mechanical heart valve (MHV). Limited experimental investigation has been conducted into the flow physics of this squeeze flow phenomenon, which is likely to be the origin of MHV cavitation. We used a pulsatile test loop simulating physiologic flow conditions and an actual-size transparent MHV model for flow visualization. A digital particle image velocimetry (DPIV) system incorporated with a microscope was applied to observe flow within a narrowing channel. A triggering mechanism was designed so that the DPIV system could be timed to capture images when the valve occluder was near its closing position. A series of images within the channel from 1.4 to 0.1 mm were captured. As the gap between the tip of the valve occluder and orifice wall becomes narrower, evidence of high-speed jet flow becomes more apparent. When the flow channel is reduced to around 0.1 mm, flow velocity of up to 2 m/s was noted. A sudden increase in high-speed jet flow causes a corresponding reduction in local pressure, and is a likely source for potential cavitation.ASAIO Journal 52(4):391-7. · 1.39 Impact Factor
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2007
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Shanghai Institute of Technology
Shanghai, Shanghai Shi, China
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