COMPUTATION OF OSCILLATING AIRFOIL FLOWS WITH ONE-EQUATION AND 2-EQUATION TURBULENCE MODELS

The ability of one- and two-equation turbulence models to predict unst eady separated flows over airfoils is evaluated. An implicit, factoriz ed, upwind-biased numerical scheme is used for the integration of the compressible, Reynolds-averaged Navier-Stokes equations. The turbulent eddy viscosity is obtained from the computed mean flowfield by integr ation of the turbulent field equations. One- and two-equation turbulen ce models are first tested for a separated airfoil flow at fixed angle of incidence. The same models are then applied to compute the unstead y flowfields about airfoils undergoing oscillatory motion at low subso nic Mach numbers. Experimental cases where the flow has been tripped a t the leading-edge and where natural transition was allowed to occur n aturally are considered. The more recently developed turbulence models capture the physics of unsteady separated flow significantly better t han the standard k-epsilon and k-omega models. However, certain differ ences in the hysteresis effects are observed. For an untripped high-Re ynolds-number flow, it was found necessary to take into account the le ading-edge transitional flow region to capture the correct physical me chanism that leads to dynamic stall.