Interaction of turbulent kinetic energy and coherent motion in the near field of the cylinder wake

Abstract

The far aim of the study is to experimentally assess the exchange of turbulent kinetic energy (TKE) of a wake behind a cylinder, as a function of the upstream flow. The wake behind the obstacle is composed of coherent motion (CM) and random motion (RM). Coherent motion, reminiscent of the Von Kármán street, interacts with the random flow, thus inducing locally enhanced turbulent cascade. This energy exchange between CM and RM is reflected by the kinetic energy budget at one point, and two points in space. In the experimental setup, a cylinder is placed in a closed loop wind tunnel to create a Von Kármán vortex street. The Reynolds number, based on the cylinder diameter and the free main stream velocity, is equal to Re = 2000. Two-dimensional, two-components in-plane velocity fields are measured behind the cylinder by Particle Image Velocimetry (PIV). Two sets of measurements are explored: without and with synchronization, based on the CM. For synchronization, a microphone is used. CM is reconstructed, by filtering the flow at 9 phase shifts, for a detailed insight.