Assessment of the CFD capabilities to predict aerodynamic flows in presence of VG arrays

Abstract

Modelling of aerodynamic flows in the presence of vortex generators constitutes a big challenge for CFD due to the different scales involved. The present paper addresses this issue in terms of accuracy and cost. In the simple case of a VG pair placed on a flat plate with no streamwise pressure gradient, the option of fully resolving the VG and that of using the jBAY model are compared with measurements and other CFD simulations. Then the case of 3D separation control on a rectangular wing is considered and comparisons to measurements are performed. Although full resolution of the VGs improves accuracy, the vorticity production is still significantly underestimated, a fact linked with the incapacity of eddy viscosity models to predict vortex flows. It is found that the simulation of one VG pair with periodic side conditions gives fair predictions as long as the VGs keep the flow attached. At angles of attack where 3D separation occurs, this cost effective modelling approach is no longer valid and simulations should include the complete array of VGs. Stereo PIV data showed that close to the VGs (up to 37.2 VG heights downstream of the VGs) turbulent transport between the vortices is strong while further downstream (up to 47.2 heights) diffusion becomes dominant. The normal Reynolds stress distributions also indicate significant vortex wandering in both the normal and spanwise directions. © Published under licence by IOP Publishing Ltd.