Skewedness as a Signature of Dean Flow Measured by Echo-PIV

Studying secondary flow in the vascular system is of importance, as it is related to hemodynamic parameters such as wall shear stress. Moreover, newly designed helical stents for the superficial femoral artery could induce secondary or swirling flow inside the blood and characterizing this flow is of interest. In this study, aiming at developing techniques to enable this characterization, high-frame-rate contrast-enhanced 2D ultrasound was employed to investigate Dean flow-a well-known secondary flow-induced in Semicircle Tubes of various curvatures. Echo-PIV was used to extract the velocity vector fields from the ultrasound image sequence and skewdness in the velocity profile was studied as a signature of Dean flow. Numerical simulations were also carried out to provide a better understanding of factors affecting skewedness, and as references of comparison for the experimental results. The experimental results show that skewedness is a quantifiable measure by echo-PIV and there is a good agreement (<5 % difference in normalized skewedness) between empirical and numerical outcomes.