Résumé:
Numerical simulations were performed to analyze the possibility of damping abrupt incoming free stream disturbances upon a porous airfoil using an unsteady Reynolds-averaged Navier-Stokes(URANS) model. To mimic the turbulence disturbance levels that are typically encountered in the atmosphere, two flow configurations were considered. In the first configuration, the unsteadiness of the flow was created with vortices shed from a circular cylinder installed ahead of a WTEA-TE1aerofoil. The continuous Von Karman shedding vortices contained within the cylinder wake were convected downstream and projected upon the airfoil. In the second configuration, an instantaneous pair of discrete vortices was created by a rotational snapping of a flat plate, installed upstream of the airfoil. Solid and porous airfoil configurations, with porosity settings of 11 and 22%, were applied on 50% of the chord of the airfoil starting from the leading edge. Both steady and unsteady flow simulations were performed to assess the performance of the porosity under steady and unsteady effects. The steady state flow simulations revealed a noticeable reduction in the airfoil lift coefficient for the porous airfoil. For unsteady solutions with a continuous or distinct series of vortices interacting with the airfoil, the porosity showed insignificant damping of the lift coefficient amplitude. The porosity values investigated in the current exercise had indiscernible effect upon the unsteady lift-load alleviations caused by free stream disturbances.
