Paper presented at the 9th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Malta, 16-18 July, 2012.
The interactions of wake of an elongated bluff body and the
periodic flow emanating from a pair of synthetic jets placed
symmetrically at the trailing edge, spanning the width of the
plate, were experimentally studied for the purpose of
quantifying the flow physics that led to wake drag reduction.
The experiments were carried out in a low turbulence wind
tunnel at Reynolds number, Reh based on the flat plate
thickness h, of about 7200. The synthetic jet actuators,
providing a global momentum addition of Cμ=24%, were
positioned symmetrically at the model base at a distance of ±
0.27 h from the base centerline to introduce perturbations at
early stages of the shear layers’ development. The synthetic jet
actuation frequency was selected to be about 75% the vortex
shedding frequency of the natural wake. Two-component
velocity measurements were acquired using Particle Image
Velocimetry (PIV) and reported for natural wake and controlled
wake using symmetric synchronous actuation and out-of-phase
actuation. In this work, mean velocity profiles, Reynolds
stresses and coherent structures and their dynamics in the wake
of a bluff body were evaluated as the initial conditions
(injection configurations) were changed. Furthermore, phaseaveraged
velocity fields through the vorticity contours were
determined to provide insights into the actuation mechanisms
namely, the role of the synthetic jet vortex structures on the
flow dynamics.
