Control of Flow Separation Using Adaptive Airfoils

Abstract

A novel way of controlling compressible flow separation, using a dynamically deforming leading edge airfoil whose nose curvature can be changed by 400% to keep the flow attached at post-stall angles of attack is reported. The strong fluid acceleration around the airfoil nose and the resulting steep adverse pressure gradient were reduced by progressively rounding the airfoil leading edge. Steady flow studies at M — 0.3 showed that the flow separating at about 14 degrees angle of attack over a NAG A 0012 airfoil could be kept attached up to about 18 degrees by increasing the nose radius. Also, a fully separated flow at high angles could be made to reattach by rounding the leading edge. Interestingly, the flow over an airfoil having a nearly semicircular nose was separated even at low angles. The research showed that a "window" of angles of attack and airfoil profiles exists in which it appears possible to keep the flow attached through a maneuver. The shape change also modified the multiple shocks that form over the NAG A 0012 airfoil at M = 0.45. Significant effects of shape change were observed on the vorticity flux in the flow.