Shape Optimisation of NACA4412 In-Ground Effect- Selection of a Turbulence Model

Abstract

Shape optimisation of a wing-in-ground airfoil would be required to improve its aerodynamic characteristics under various flight conditions. Identification of an optimised shape at various heights above ground (h/c) and angles of attack (α) could be helpful in developing morphing wing capabilities for such airfoil. Prior to conducting shape optimisation a suitable turbulence model have to be selected for such studies. We have performed In-ground-effect (IGE) simulations using four turbulence models, viz., Spalart Allmaras, SST k-ω, Standard k-ε and Transition SST model, to compare their advantages and disadvantages during such analysis. For an unaltered NACA4412 airfoil, while all the models predicted coefficient of lift (Cl) in close agreement with experimental results, Transition SST model was able to predict fine details like laminar separation bubble formation. There was a generic discrepancy in predicting drag coefficients (Cd) with all these turbulence models. However results from Transition SST were the closest to experiments. Spalart Allmaras and SST k-ω were better in the prediction of Cd when compared to standard k-ε model. We consider such studies would be helpful to generate a database of optimised airfoils for a variety of flight conditions near to ground.