Effects of Unsteady Coanda Blowing on the Wake and Drag of a Simplified Blunt Vehicle
The impact of periodic forcing on the wake past a square back bluff body is experimentally studied. By the use of pulsed jets in combination with a Coanda effect, shear layer forcing allows to recover over 30 % of the model’s base pressure. The actuation frequency is an order of magnitude higher than the natural flow instabilities. Velocity measurements indicate that this direct wake control modifies the vorticity development along the shear layers and shrinks the width of the recirculating flow region down. At the same time, the velocity fluctuations in the near wake decrease, without measurable impact on the oscillatory vortex shedding. With this control strategy, both the flow deviation and the base pressure recovery are dependent on the upstream Reynolds number. Particle image velocimetry data and pressure measurements are used to discuss the origin of these observations.
KeywordsParticle Image Velocimetry Shear Layer Strouhal Number Bluff Body Rear Surface
The thesis of D.B is supported financially by PSA—Peugeot Citroën and ANRT in the context of the OpenLab Fluidics between PSA - Peugeot Citroën and Institut Pprime (fluidics@poitiers). The authors acknowledge the funding of the Chair of Excellence - Closed-loop control of turbulent shear flows using reduced-order models (TUCOROM)- supported by the French Agence Nationale de la Recherche (ANR). We warmly thank the support during the experiments by J.M. Breux.
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