Comprehensive In Vitro Study of the Flow Past Two Transcatheter Aortic Valves: Comparison with a Severe Stenotic Case

We investigate the flow past two transcatheter aortic valves (TAVs) and one severely calcified valve in an anatomically realistic aorta geometry to evaluate the ability of the TAVs to establish a healthier aortic flow compared to a diseased case. Velocity measurements of pulsatile flow are carried out using the 3D-particle tracking velocimetry technique. We present a novel approach based on the Smagorinsky model to assess the important subvoxel-scale (here smaller than 750 mu\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\mu$$\end{document}m) shear stress contribution that is usually unavailable in experiments. Both TAV models feature a small retrograde flow of about 5% of the stroke volume and a lower number of coherent vortical structures. Turbulence past the TAVs is strongly suppressed as evidenced by the lower levels of turbulent kinetic energy even though the newer generation TAV performs better than the old one. Also lysis indices are substantially reduced in both models. The new generation TAV displays a slightly higher risk for thrombogenicity due to longer exposure times. We anticipate that our new approach to include turbulence and shear stress related quantities may help to validate the design of cardiovascular devices.