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The main purpose of this study was to carry out a detailed
study of the flowfields between the leaflets of widely used
bileaflet heart valves. In conventionalresearch, the sewing ring
of the valve acts as an obstacle for measurement. In addition,
the small space in between the leaflets limits the amount of
detailed measurement, which can be done. Therefore, in this
study two enlarged semicircular plates were used to mimic the
actual fully-opened leaflets during peak systole and the flow
field was measured according to dynamic similarity. Flow
visualization technique and Laser Doppler anemometer (LDA) were
used toobtain qualitative and quantitative data, respectively of
the various turbulence characteristics of the flow between the
plates and downstream near the wake. The spacings and angles of
the plates were changed to study their interactions. Shear
stresses in the flow and along the walls of the plates were also
measured to evaluate the damage inflicted on red blood cells and
platelets. According to experimental result of the
visualization flow fields, the deflection of the central flow
field is more obvious as the angle of bileaflets becomes larger
because of the Coanda effect. However, the direction of
deflection is not specific and is especially obvious when the
plates' angle is 12° and the interval is 7.5 mm. As the
interval increases, the Coanda effect tends to decrease. The LDA
measurements show that the maximum shear stress is smallest when
the plate are fully open and the angle between a single leaflet
and streamwise flow is 0°~6°, thus lowering the possibility of
thrombosis.
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