Drag and wake modification of axisymmetric bluff bodies using Coanda blowing

This work investigates the ability of Coanda jet blowing to modify the base pressure of a cylindrical body aligned axially in a flow, and thereby, produce overall drag reduction. It is found that blowing through one or two slot jets concentric to the outer body circumference can significantly influence the entire base flow region. The recirculating wake is eliminated and is replaced by freestream fluid entrained by the Coanda blowing. Base pressure rises significantly and leads to drag reduction of up to 30% beyond the thrusting action of the Coanda jet. A comparison between the power savings through drag reduction and the power requirement of the Coanda jet demonstrates that net benefits are attainable at certain body geometries and flow conditions. By judiciously selecting the jet blowing velocity, it is possible to produce a nearly flat wake velocity profile requiring little net power.