Marc de Piolenc wrote:

Quick $.02 contribution:

1. NACA flush inlets are designed for positive-pressure areas of the
fuselage. If the fuselage contour at the intended inlet location
produces local suction and you need positive pressure to drive flow
through the duct, heat exchanger or whatever, the only remedy other than
relocating the inlet is a projecting scoop that generates a positive ram
pressure.

2. Most people, as already pointed out, don't read the original papers,
so they are not aware of  the fact that the scoop shape is much more
complex than in the usual modern implementation. In particular, there is
a lip that is intended to "fold" the local boundary layer to reduce the
effect of "approach loss" due to boundary layer growth. I have literally
never seen a lip on a NACA inlet in the field.

Best,
Marc de Piolenc

You can see it on this one.

Paul Lamar

 
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