Simulation of Flow around a Thick Airfoil with a Vortex Trapping Cavity

This paper presents a numerical study of a low Reynolds number flow around a thick airfoil (Eppler's E863 airfoil) with and without an upper-surface vortex-trapping cavity. The numerical model of flow is constructed using an O-grid computational domain around the airfoil and analyzed using four different turbulence models: namely standard k-epsilon, RNG k-epsilon, SST k-omega and the one-equation Spallart-Almaras (SA). Enhance wall treatment is employed for the two-equation turbulence models with the non-dimensional first cell height y(+) at the wall region kept close to 1. The Reynolds number is kept constant at 354000. Results of lift & drag coefficient as well as velocity profiles are presented for four different angles of attack from 0 to 15 deg. The RNG k-epsilon model is found to better predict the flow field and airfoil lift and drag characteristics as compared to the other turbulence models taken into consideration in this paper.. The presence of the vortex-trapping cavity midway on the upper-surface of the airfoil is found to yield higher lift coefficients as well as prevent flow separation but at the cost of increase the drag coefficient.