Starting Vortex, Separation Bubble and Stall - A Numerical Study of Laminar Unsteady Flow Around an Airfoil

摘要

The stalling characteristics of an airfoil in laminar viscous incompressible fluid are investigated. The governing equations in terms of vorticity and stream function are solved utilizing an implicit finite difference scheme and point successive relaxation procedure. The development of the impulsively started flow, the initial generation of circulation and the behavior of the forces at large time are studied with emphasis on the formation region. Following incipient separation, the lift increases due to enlargement of a separation bubble and intensification of the flow rotation in it. The extension of this bubble and beyond the trailing edge causes its rupture and brings about the stalling characteristics of the airfoil. The lift increases when attached clockwise bubbles grow and anti-clockwise bubbles are swept away and vice versa. (Author Modified Abstract)