The Aerodynamic Interaction Effects between the Rotor and Fuselage on the Drag Performance of a Civil Helicopter in Forward Flight

The aerodynamic interaction between the rotor and fuselage is an important consideration in relation to the drag performance prediction of helicopters. In this paper, based on dynamic patched-grid technology coupled with a three-dimensional N-S equation solver, a numerical study of the aerodynamic interaction effects between the rotor and fuselage on the aerodynamic performance and flow field of the fuselage of a light civil helicopter is carried out under the forward flight condition. The deterioration of the drag performance and the evolution of the flow field structure caused by the rotation of the blades are illustrated. Due to the aerodynamic interaction, the drag of the fuselage is increased by 124.1% while the cycle of drag fluctuation is observed in one full revolution of the rotor with a change in amplitude of & PLUSMN;20%. The comparative results between the rotor-off and rotor-on cases show that the aerodynamic interaction effects between the rotor and fuselage on the drag performance are mainly reflected in the influence of the backward-developing rotor wake on the flow field of the rear part of the fuselage. An additional afterbody vortices system is induced, leading to a large reverse pressure gradient on the rear surface of the helicopter, which contributes to an increase in the pressure drag.