Turbulent two-dimensional flow around a flexible membrane airfoil

The two-dimensional, incompressible flow at Reynolds number Re = (Uinfinity.c)/(v) = 1.3(.)10(6) around an inextensible, flexible membrane airfoil (sail) with varying excess length epsilon is examined solving the Reynolds-Averaged Navier-Stokes (RANS) equations on grids deforming according to the sail movement within fixed outer boundaries. Results are presented for fully turbulent conditions employing closure models of different degree of complexity in comparison to experimental and analytical results. Good agreement can be found for low angle of attack. However, for higher angle of attack, approaching onset of separation and beyond, the predictive accuracy varies significantly with the representation of turbulence in the presence of strong unsteady phenomena.