View Single Post
Old Oct 09, 2012, 09:07 AM
Mitchell Covell is offline
Find More Posts by Mitchell Covell
China, Guangdong, Shenzhen
Joined Nov 2010
74 Posts
The success of the KF airfoil at low Re numbers might have nothing to do with the theory posited by Kline and Fogelman. Wind tunnel tests done with a corrugated airfoil modelled after a generic dragon fly mid-span section show the entrainment of vortices behind the corrugations at Re = 34,000. The corrugated airfoil had higher drag at low AoA, but a higher stall AoA, and higher L/D since the airfoil attained a higher coefficient of lift before stall. The step on the KF airfoil might cause the favourable attributes frequently cited for these airfoils by the entrainment of a vortex(s) in the manner observed for this corrugated airfoil.

If this is true then there is room for a lot of work to determine the Re number range for which the the effect can be used without undo drag; best leading edge shapes; cord lengths for corrugations; relative height of the corrugations; best shapes for the bottom of the airfoil etc.
It would be wonderful if somebody with a wind tunnel at their disposal could do some systematic testing - one variable at a time!
Mitchell Covell is offline Find More Posts by Mitchell Covell
Reply With Quote