Investigation of viscosity effects in Womersley flows with Newtonian blood analog fluids

The goal is to understand the effect of kinematic viscosity in the Newtonian blood analog solutions that are commonly used in experimental cardiovascular flows. The blood analog solutions considered were (i) deionized water with Glycerol and (ii) Potassium thiocyanate-DI (both approx., 60-40% by weight) The kinematic viscosity was measured using a Ubbelhode viscometer and the infinite shear viscosity was measured using a rheometer. The degree of pulsatility in the blood flows is commonly described by the Womersley number defined as the ratio of transient inertia forces and viscous forces and is function of kinematic viscosity and time period of the flow waveform. When the Womersley parameter is low, viscous forces dominate, velocity profiles are parabolic, and the centerline velocity oscillates in phase with the driving pressure gradient. In this study the change in kinematic viscosity and corresponding change in phase lag of velocity from that of pressure gradient are examined in straight, cylindrical vessels under physiological flow forcing conditions. Real-time flow conditions were monitored using catheterized blood pressure transducers and an ultrasonic flow rate sensor. These data provide insights into the role of blood viscosity which varies greatly in the circulatory system.