A study of airfoil trailing-edge singularities

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A study of airfoil trailing-edge singularities

Dini, P. / Maughmer, M.D.

The strong viscous/inviscid interaction encountered by the turbulent flow over sharp airfoil trailing edges is traceable to non-uniformities generally appearing in the boundary conditions at the trailing edge. The mechanism by which these non-uniformities induce the observed strong interaction is explained in terms of a generalization of conventional boundary-layer theory, in which the potential flow, instead of determining the pressure, determines the magnitude of the viscous diffusion terms inside the boundary layer. Thus, the larger wake curvature near the trailing edge induced by trailing-edge loading leads to an adverse strong interaction as it promotes trailing-edge separation from the upper surface. On the other hand, a singularity in the curvature of the airfoil surface generally present at the trailing edge leads to a favorable strong interaction. In fact, it induces an acceleration at the beginning of the wake that enhances the ellipticity of the trailing-edge flow, thereby helping the boundary layer remain attached. The impact of these effects on airfoil design and the possible benefits on airfoil performance are discussed.