Helicopter Fuselage Drag Reduction Using Active Flow Control: A Comprehensive Experimental Investigation

A comprehensive experimental investigation of helicopter blunt fuselage drag reduction using active flow control is being carried out within the CleanSky project. The objective is to demonstrate the capability of several active technologies to decrease fuselage drag by alleviating the flow separation occurring in the backdoor area of some helicopters (with pronounced ramp for backdoor loading). The work is performed on a simplified blunt fuselage at model-scale. Several active flow control actuators are considered for evaluation: steady blowing, unsteady blowing (or pulsed jets), zero-net-mass-flux blowing (or synthetic jets). For the first two actuations, additional air supply is required to bring the mass-flow through the actuators while synthetic jets are based on alternate blowing/suction phases and do not require additional air supply. Laboratory tests of each individual actuator are first performed to assess their performance and properties. The fuselage model is then equipped with these actuators distributed in 8 slots forming a U-shape on the fuselage backdoor. This paper addresses the promising results obtained during the wind-tunnel campaign, since significant drag reductions are achieved for a wide range of fuselage angles of attack. Moreover, a flow control strategy depending on the fuselage attitude is proposed. The link between the best actuation scheme for this attitude and the corresponding flow topology of the backdoor separation is also discussed.