A Computational Framework for Helicopter Fuselage Drag Reduction Using Vortex Generators

Abstract

A computational framework is described for the computational fluid dynamics (CFD) simulation of a bluff helicopter fuselage equipped with vortex generators (VGs). The VGs are explicitly discretized in the CFD mesh, using an overset grid method. A computational setup was developed allowing parametric investigations for VG size, pitch angle, position, number, arrangement, and thickness effects. High-density meshes were generated with successive grid overlap between body-fittedmeshes with high grid resolution in the boundary layer and Cartesian grids for the near and far field. The methodology was applied to the model-scale GOAHEAD model with sponsons. This model permits drag reduction by passive flow control on the model back ramp where the pronounced upsweep is responsible for a large separated flow at the backdoor/tail-boom junction. A test matrix was completed, and a VG layout proved its effectiveness for an eight-pair array of counterrotatingzero-thickness vane-type VGs, with the device height defined according to the local boundary layer thickness. At cruise conditions, some VG configurations tested achieve up to 5% drag reduction by cumulated effects of flow reattachment, limited device drag, and static pressure recovery.