Non-conventional vortex generators calculated with CFD

Abstract

Wind turbine blades size has increased during last years due to wind turbine platform growth especially for offshore applications. The interest of wind turbine manufacturers in blade add-ons have raised to mitigate flow separation and blade loading. One type of add-ons are the vortex generators (VGs).VGs are passive flow control devices that are usually triangular or rectangular vanes inclined to the flow and are dimensioned with regard to the local boundary layer thickness. VGs are known for their capability of delaying separation and increasing lift force on the blade. Their main drawback is the drag penalty added to the blades. In this work, novel shaped VGs are computed with OpenFoam using a fully resolved approach to test if they are efficient with regard to the drag penalty. The use of non-conventional VGs reduce the separated flow zone in the leading-edge of the vane resulting in a lower residual drag and in an increase on the overall efficiency. This fact would reduce the loads associated with the vane.Three VG shapes are simulated. Two of them have a cross section based on thin airfoils and the other one is a conventional rectangular VG used as reference. The VGs are mounted on a flat plate and they are calculated for the same flow characteristics and size than the ones used in the experiments performed under the scope of the AVATAR project [1]. Relevant quantities, such as the peak vorticity, the vortex vertical and lateral paths, wall shear stress, velocity contours and drag coefficient, will be compared in order to evaluate the VGs performance.