Paul;
Our goal is the same.  I have no interest in just making controversy.
Velocity made the change from armpit scoops under the strakes to the
NACA scoops on top of the fuselage because they worked better.  There
are other cases of EZ's that found what I might call a quasi--NACA
scoop
on top worked better than the prior armpit scoops.  Analysis of the
pressure distribution on a fuselage typical of the canards show
relatively high pressure; about the same as on the bottom, when you get
that far back on the fuselage.  And because the pressure is increasing,
the boundary layer is being squeezed out, flowing at an angle down the
sides of the fuselage.

So; in the case under discussion, the SQ, it is reasonable to believe
the external scoops on top, which are already there,  would work, and
may work better than armpit scoops.  Maybe not better than a P-51 style
scoop underneath, that we don't know.

My personal opinion is that the reason the Velocity armpit scoops
didn't
work as well was because of a poorly designed scoop, not because of the
placement.  I chose to put a p-51 style scoop under the strake
(armpit).
I don't know yet whether it will work well.

Al

I find it really hard to believe that the pressure is increasing
on the top of the Velocity cabin. In fact I am willing to bet lots
of money it is not. If one does not have experience measuring pressures
it is easy to make a mistake. I would like to see pictures of just how
the pressure was measured up there. Did they use porous foam for
example?
It would be real easy to use an air velocity rake to determine the
thickness
of the boundary layer and porous foam static pressure taps if someone
has
a flying Cozy or Velocity.

Pictures: Velocity rake on Tracy airplane wing and static pressure tap
using porus
foam  in left cowl opening.

Paul Lamar

Paul,
This is an old thread, but I just wanted to pass along a thought I had
for those
struggling to make the NACA inlet work.  This is just a wild guess
though.

Vortex generators placed 2-3 inches upstream of the inlet might increase
the flow
through the scoop, given favorable pressure gradients for the cooling
system
as a whole.

Chris C.
microcosman.com/aircraft

It is generally not a boundary layer problem so vortex generators are
not the answer. Forget NACA ducts for heat exchangers.

Paul Lamar
 
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