On Jul 25, 8:54*pm, 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?

The NACA duct was designed such that the edges create vortices
which force the air into the duct. Reversing the flow through a NACA
duct is an inefficient way to exit fluid from a body.