Study of Wall-Effect on Two-Dimensional Airfoils in an Unsteady Flow

Abstract

A numerical method is presented for calculating the pressure, forces and moments on arbitrary-shaped airfoils in an unsteady potential flow between two parallel walls. Airfoils and walls are represented by vorticity distributions and mirror images respectively. Vortex movements are determined by discrete vortex method. Our method does not have the restrictions on the height of walls and the location of airfoils between walls. The calculations are carried out for two cases of starting flow and accelerating flow. It is found that when walls come closer, the steady lifts, moments and apparent mass become greater, and the unsteady lifts and moments reach the steady values faster, and that the pressure center of airfoils moves notably under the influence of the flow acceleration.