Wall Shear Stress Measurements using Molecular Tagging Velocimetry (MTV) for Model Physiological Flows in the Cardiovasculature

Flow-induced shear stresses in the near wall regions of arteries are associated with atherosclerosis, a cardiovascular disease with one of the highest fatalities in the US. The goal of this study is to develop a technique to enable experimental wall shear stress (WSS) measurements in cylindrical tubes that are rigid, straight, artery phanta with pulsatile flow of Newtonian blood analog fluids. WSS measurements in cardiovascular flows are challenging when using tracer particle-based optical diagnostic techniques. Molecular Tagging Velocimetry (MTV) is used to determine near-wall velocity gradients under physiological flows pertinent to the cardiovasculature. Inflow conditions are scaled using kinematic viscosity and length-scale of the artery geometry. The results are benchmarked using Womersley’s analytical solution for pulsatile flow in a tube, from which an analytical expression for near-wall, pulsatile drag force was obtained. The traditional limitations of spatio-temporal resolution of MTV techniques for liquids are overcome by a novel photobleaching approach with Talbot-effect structured illumination using a pair of common neodymium-doped pulsed lasers (355 and 527 nm) opening the possibilities to address more complex arterial geometries and flow conditions in future studies.