Unsteady separation flows on a flat-plate are studied when an airfoil is placed above the plate. The Hybrid Random Vortex Method(HRVM) is employed to calculate the viscous flow near the plate, which consists of Random Vortex Method(RVM) and Vortex Sheet Method(VSM). The accuracy of the HRVM is verified here for the Blasius flow by choosing appropriate numerical parameters.
The effect of the airfoil on the flow near the plate can obtained by using an vortex-panel method to represent the airfoil surface. Unlike the inviscid solution, formation and disappearing of small or large separation bubbles are observed and significient fluctuations of the flow field occurs in the viscous solution.
However, a periodic motion is not found out. The strength and size of the separated regions depends on the vertical position of the airfoil relative to the plate, the angle of attack and the Reynolds number.
