Coherent structures and entropy generation in highly pulsed flow in a stenotic vessel: A time-resolved PIV-POD analysis

Stenosis in large arteries induces hemodynamic instabilities that can promote thrombus formation and ischemic complications. This study characterizes transitional pulsatile flow (Reynolds number Re = 115–347, Womersley number α = 12) through a silicone phantom with 50% concentric stenosis using time-resolved Particle Image Velocimetry (PIV) to obtain planar velocity fields. Proper Orthogonal Decomposition (POD) shows that the first six modes capture nearly 99% of the fluctuating kinetic energy and represent a dominant post-stenotic jet, recirculation zones, and convecting vortices that govern flow organization. . The Reynolds normal stress, Reynolds shear stress, and entropy generation associated with each POD mode are analysed. The first two modes account for approximately 80% of the total entropy production, whereas the first six modes capture about 95%, indicating that irreversible losses are dominated by a small set of energetic coherent structures rather than by small‑scale turbulence. Low‑order POD reconstructions based on these leading modes accurately reproduce the pathological flow dynamics and provide a compact reduced‑order representation suitable for hemodynamic assessment in stenotic arteries.