"Tim Taylor" wrote

I still think a reversed NACA duct will work better than the Butler
and much better than the Mandl. The Mandl throws the low speed air
out into the faster air stream. The JS design accelerates half the
air over the airfoil but what happens to the air under the airfoil?

Reversed NACA ducts are poor at exhaust, from studies I have read. If you use
one like that, a small raised bump upwind of the vent helps greatly.
--
Jim in NC