A Computational Framework for Helicopter Fuselage Drag Reduction Using Vortex Generators

A computational framework has been developed for the CFD computation of a blunt helicopter fuselage equipped with vortex generators (VG). The VG are explicitly discretized in the CFD mesh, within the use of the overset grid method. A dedicated mesh generator developed at ONERA has been improved together with an all-in-one computational set-up, allowing parametric investigations for VG arrangement, shape, position, and size effects. The methodology has been applied to a down-scaled GOAHEAD-like wind-tunnel model, for drag reduction by passive flow control on the backdoor surface at cruise-flight conditions. A test-matrix has been completed and a reference VG configuration was identified as promising for an array of 2x8 counter-rotating VG with zero-thickness vane-type like planform. The VG were sized according to the approximated boundary-layer thickness following classical integral formulation for a longitudinal flow. At cruise conditions, the VG configuration achieves about 5% total drag reduction by strongly reducing the extension of the separated flow at the backdoor/tail boom junction. The proposed reference VG configuration will be tested during a wind-tunnel test campaign for the same GOAHEAD-like downscaled model.