Investigation of the three-dimensional flow past a flatback wind turbine airfoil at high angles of attack

Abstract

Flatback airfoils are airfoils with a blunt trailing edge. They are currently commonly used in the inboard part of large wind turbine blades, as they offer a number of aerodynamic, structural, and aeroelastic benefits. However, the flow past them at high angles of attack (AoA) has received relatively little attention until now. This is important because they usually operate at high AoA at the inboard part of Wind Turbine blades. The present investigation uses Reynolds averaged Navier-Stokes (RANS) and hybrid RANS + large eddy simulation predictions to analyze the flow in question. The numerical results are validated against previously published wind tunnel experiments. The analysis reveals that to successfully simulate this flow, the spanwise extent of the computational domain is crucial, more so than the selection of the modeling approach. Additionally, a low-drag regime observed at angles of attack before stall is identified and analyzed in detail. Finally, the complex interaction between the three-dimensional separated flow beyond maximum lift (stall cells) with the vortex shedding from the blunt trailing edge is revealed.