Interactive Boundary-Layer Method for Unsteady Airfoil Flows: Quasi-Steady Model

An interactive boundary-layer method previously developed and tested for steady flows is used here in a quasisteady manner to examine the evolution of the flow behavior of airfoils subject to harmonic oscillation and ramp-type motions. The calculations encompass the airfoil and wake flows at angles of attack that lead to separation. The results quantify the effects of the viscous boundary layer and wake on the variation of lift coefficient with angle of attack and reduced frequency. These effects are shown to be large at angles of attack that involve boundary-layer separation. I