NUMERICAL INVESTIGATION OF STALL FLUTTER

Unsteady, separated, high Reynolds number flow over an airfoil undergo ing oscillatory motion is investigated numerically. The compressible f orm of the Reynolds-averaged governing equations is solved using a hig h-order, upwind biased numerical scheme. The turbulent pow region is c omputed using a one-equation turbulence model. The computed results sh ow that the key to the accurate prediction of the unsteady loads at st all potter conditions is the modeling of the transitional pow region a t the leading edge. A simplified criterion for the transition onset is used. The transitional flow region is computed with a modified form o f the turbulence model. The computed solution, where the transitional pow region is included, shows that the small laminar/transitional sepa ration bubble forming during the pitch-rep motion has a decisive effec t on the near-wall flow and the development of the unsteady loads. Det ailed comparisons of computed fully turbulent and transitional flow so lutions with experimental data are presented.