Vortex dynamics in compliant stenotic aortic models using ultrasonic particle imaging velocimetry

Abstract

In this work we used ultrasonic particle imaging velocimetry (US-PIV) to study vortex formation and shedding in aortic models with different degrees of stenosis as flow increases. CT-images were used to create a mold of the descending aorta. A Polyvinyl Alcohol solution with a reinforcing cotton mesh was used to generate models with 0%, 35% and 50% occlusion degree. Each model was connected to a circuit with a pulsatile programmable pump which mimics flow and the pressure wave from the heart. The pulsatile frequency was 0.9 Hz and the upstream peak Reynolds number (R) was modified from 600 to 2100. The fluid velocity field was measured via US-PIV. Flow in the unobstructed model showed a laminar parabolic velocity profile. However, in the occluded models, flow transitioned from laminar to vortex formation and shedding as R increased. For a 35% occlusion, at R=2100 a very small vortex without shedding appeared behind the occlusion. For a 50% occlusion vortex propagation velocity increases from 1.9 cm/s to 6.2 cm/s as R increases from 1000 to 2100. Moreover, high shear stress concentration is placed behind the stenosis where vortices form and shed. Therefore, this kind of study may help understanding plaque evolution and rupture.In this work we used ultrasonic particle imaging velocimetry (US-PIV) to study vortex formation and shedding in aortic models with different degrees of stenosis as flow increases. CT-images were used to create a mold of the descending aorta. A Polyvinyl Alcohol solution with a reinforcing cotton mesh was used to generate models with 0%, 35% and 50% occlusion degree. Each model was connected to a circuit with a pulsatile programmable pump which mimics flow and the pressure wave from the heart. The pulsatile frequency was 0.9 Hz and the upstream peak Reynolds number (R) was modified from 600 to 2100. The fluid velocity field was measured via US-PIV. Flow in the unobstructed model showed a laminar parabolic velocity profile. However, in the occluded models, flow transitioned from laminar to vortex formation and shedding as R increased. For a 35% occlusion, at R=2100 a very small vortex without shedding appeared behind the occlusion. For a 50% occlusion vortex propagation velocity increases from 1.9 cm/s to 6...