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This study was focused on how the height of the sewing ring of
bileaflet artificial heart valves and exit angle of the tallest
sewing ring affect the downstream flow field with a peak
discharge of 30 l/min . The models used in the experiments had
sewing rings ranging from 12.4 mm to 29.6 mm in height, which is
about twice the size of the St. Jude Medical (SJM) and On-X
valves , respectively, and exit angles ranging from 78° To
98°. Each model was tested with and without leaflets, which
opened at a 90° angle.Flow visualization technique and a laser
Doppler anemometer (LDA) were used to obtain qualitative and
quantitative data ,respectively, of the flow field. Shear
stresses were also measured to evaluate the amount of damage
inflicted on red blood cells and platelets.Results show that
there is recirculation in the sinus area of the aorta. When the
models have leaflets, the central orifice flow is greater than
the side orifice flow. The contraction and expansion of the
sewing ring causes the flow velocity to obviously increase and
decrease, respectively. From the axial-velocity distribution, we
can recognize the difference in velocity gradient, the growth of
the shear layer in wake and sinus wall , and the recovery
condition of the flow field .When without leaflets , the axial
and lateral Reynold normal stress and shear stress values
decrease as the height of the sewing rings increases .The
maximum values appear when the exit angle of the sewing rings
is 98°. When there are leaflets, the positions of the maximum
axial and lateral Reynold normal stress values vary according to
the different flow conditions. The Reynold shear stress is
asymmetrically distributed at the wake and weakens further
downstream. Its maximum values appear closer to valve as the
height of the sewing ring increases.
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