An in-vitro study of the flow past a transcatheter aortic valve using time-resolved 3D particle tracking

The performance of a prosthetic heart valve can be evaluated by analyzing the complex flow structures downstream of it. Particle residence time, a measure of flow stasis, can be used to determine the potential risk of thrombosis. In our past studies, such information was obtained by pseudo particle tracking schemes applied to 2D PIV data. However, since the flow past a heart valve is predominantly 3D, 2D methods could not capture the whole picture. In this work, time-resolved 3D particle tracking velocimetry (Shake-The-Box 3D-PTV) was used to study the flow past a transcatheter aortic valve in an idealized aortic root model under physiological flow conditions. The acquired flow structures and 3D time-resolved Lagrangian particle tracks allowed direct assessments of the particle residence time in the aorta and sinuses of Valsalva. Vorticity distributions and turbulence statistics were obtained by projecting the particle tracks onto a Cartesian grid. During the systolic phase, the flow was dominated by the aortic jet and a shear layer between this fast-moving jet and the ambient fluid. At the end of systole, as large amounts of fluid reentered the flow field during valve closure, a circumferential flow pattern was observed in the sinuses, enhancing the particle washout there.