Applications of FSI for Cardiovascular Haemodynamics - Computational Hemodynamics: Theory, Modelling and Applications - page 303

Fig. 8.71 Initial grid and velocity vectors at seven different times during diastole, the velocity
scale to the right is given in ( m/s ). (Image from Dahl et al. 2010)
higher angular velocities throughout the simulation. However, despite some varia-
tions, the simulated leaflets follow the same main pattern as in the measurements.
In the ultrasound recordings, the opening velocities of the posterior and anterior
leaflets do not deviate much from each other. In the simulation, the two leaflets have
significantly different velocities.
Figure 8.71 shows the initial grid and seven sequential velocity-vector plots at
time intervals of 60 ms. When the ventricular pressure falls below the atrial pres-
sure, the rapidly changing atrium-ventricle pressure gradient leads to an opening
of the valve. In the first filling phase, ( t = 60 ms, and 120 ms), the transmitral flow
is almost uniform. No vortices are observed in the ventricle, whereas a vortex has
started to develop at each pulmonary valve orifice in the atrium.
As the blood flows into the ventricle, the atrio-ventricular pressure gradient
decreases and reaches a minimum value in mid-diastole/diastasis ( t = 180 ms to
300 ms). This causes a deceleration of the transmitral flow and the leaflets now drift
back towards the annulus. This is called partial closure. Two large vortices develop