Trailing-edge region of airfoils

Abstract

Measured and calculated results obtained in a set of trailing-edge flows are examined to consolidate understanding of the requirements and implications for airfoil calculation methods. The experiments investigated sharp, round, and blunt trailing edges, attached and separated turbulent boundary layers, and boundary-layer interaction with the wake of an airfoil on the suction side. Emphasis is placed on higher angles of attack and on the consequences of flow separation. A combination of inviscid-flow calculations, interactive boundary-layer calculations with equations in integral and differential form, and Reynolds-averaged Navier-Stokes calculations have been used to confirm conclusions based on these experiments and to assess implications for approximations. The measurements suggest, and calculations confirm, that streamwise and normal momentum equations need to be solved in calculations of trailing-edge flows and that, in particular, normal pressure gradients and turbulence normal stresses need to be represented. Turbulence production from Reynolds normal stresses can exceed turbulence shear stress production in a separated flow, and this has implications for turbulence models. The ability to calculate contributions to lift and drag is considered within the trailing-edge region, and the experimental and computational uncertainties incurred in the results are examined.