Unsteady Aerodynamics of High Lift Systems using Overset Mesh

High lift devices facilitate the achievement of higher Cl on take-off and landing. But the motion of the high lift devices causes unsteady effects that have a significant influence on the resulting lift and drag forces. Hence a 2D unsteady numerical simulation during the retraction of a slat of HL-CRM is conducted to understand the unsteady effects produced during slat motion. Overset grid technique was employed to facilitate flexible motion of the slat. The simulation was carried out using OpenFOAM. It is observed that the value of lift coefficient decreases and drag coefficient increases in steady-state cases, because of the wake region created behind the slat at deployed position and airfoil. As in the transient case, there are huge fluctuations at the beginning of the motion and the fluctuations stabilize at the end emphasizing that the position of the slat during motion affects the entire flow field.