Integrating high-frequency, time resolved TSP surface maps and wake flow Lagrangian description to investigate sub critical regime in a crossflow cylinder

Abstract

We use the combination of a fast-response underwater Temperature Sensitive Paint (TSP) and a multiframe Particle Tracking Velocimetry (PTV) to get some insight of the flow around a cylinder in sub critical and critical regimes up to Reynolds number Re < 275000, i.e. both below and above the drag crisis threshold. TSP images are able to capture some of the main features of the flow-structure interaction that concern the cylinder surface, like the evolution of the separation line position and the dynamics of the complex pattern of the coherent structures acting on the body surface. PTV velocity, vorticity and Lagrangian acceleration fields provide information about the surrounding flow. Mean field of the Lagrangian acceleration close to the cylinder surface represents a complementary information to the TSP one about the flow separation-reattachment and establish a link between the temperature trace evolution on the cylinder surface and the phenomenon from which it is generated.