Leading Edge Separation Criterion for an Oscillating Airfoil
VEHICLE RESEARCH CORP PASADENA CA
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Unsteady flow about the well-rounded nose of a subsonic airfoil is investigated from the viewpoint of leading edge separation. For an airfoil undergoing forced pitching and heaving motions in a uniform flow, fluid accelerations about the leading edge can be enormous according to inviscid flow theory. Such accelerations are limited by viscous flow and separation realities. The method of matched asymptotic expansions is used to develop a uniformly valid first order approximation to the inviscid flow about the airfoils leading edge which is driven by a history-dependent term related to the airfoils transverse motions. Applying this flow to the laminar boundary layer flow at the airfoil nose produces possibilities for a laminar boundary layer to separate. A method is proposed for predicting leading edge dynamic stall based upon relating properties of the envelope of the unsteady part of the boundary layer speed and shear stress to the steady part of the boundary layer flow.
- Fluid Mechanics