Prediction of Aerodynamic Characteristics of an Elliptic Airfoil at Low Reynolds Number

Abstract

This study focuses on modeling the effects of transitional flow and surface curvature on aerodynamic characteristics of an elliptic airfoil. Numerical simulations have been performed on a 16% thick elliptic airfoil for a range of angle of attack (α) from 0° to 20° and flow Reynolds number (Re) of 3 × 105, using relatively new transition-sensitive and traditional fully turbulent eddy viscosity turbulence models. Test conditions were matched to experiments by Kwon and Park (2005) and numerical results were compared with available experimental data. Results indicate that the transition-sensitive models, namely k-kL-ω and Transition SST, accurately predict the laminar-to-turbulent transition locations and reproduce the laminar separation bubbles on the suction surface of the airfoil in agreement with the experimental data. Also, transition-sensitive models yield improved predictions of lift and drag performance when compared with results from fully turbulent models. The fully turbulent models; including SA and k-ω SST, and a newly developed curvature-sensitive model (SST k-ω-ν2) fail to capture the flow separation and reattachment locations near the leading edge of airfoil. However, the curvature-sensitive SST k-ω-ν2 model predicts the stall point of the airfoil close to experimental results, while all other tested RANS models failed to accurately predict the stall point. Taken as a whole, the results suggest that accurate aerodynamic predictions at both low and high angles of attack might be achieved by using a model that includes the effects of both transition and curvature.

Mechanism of unconventional aerodynamic characteristics of an elliptic airfoil

“…Many studies have been accomplished, some of which are experimental, 9,10 while the majority of which are numerical and mostly at low Reynolds numbers. [11][12][13] Unlike general airfoils, the typical characteristic of an elliptic airfoil is the blunt trailing edge, which can cause flow separation and vortex shedding to form Karman vortex street aft of the airfoil. At small angles of attack, the boundary layer is primarily laminar over the airfoil surface, but as a increases, the laminar separation bubble 14-16 may form near the leading edge on the suction surface of the airfoil, which will result in laminar-turbulent transition.…”