Ed;

 

Well, ED, the more I look at this idea, the more trouble it gives me; so I will express a dissenting opinion.  I never argue against what works; but my conclusion here is that - assuming it does work better in your case than a nice entrance and a continuously expanding duct of some reasonable shape - is due to the fact that you have external diffusion (buildup of pressure in front on the cowl entrance) and turbulent flow at the entrance behind the prop.  So without doing some flow testing, I’d suggest caution in using this approach for inlet scoops in front of radiators in other locations.

 

Accelerating the air costs you dynamic pressure and increases friction losses, and (depending on entrance and frictional losses) ‘pinching’ the area by more than about 30% would cause serious choking of the flow, resulting in most of the air spilling around the entrance.  The more rapidly expanding area after the pinch and more rapid pressure increase is at least as likely to result in flow separation as a less rapidly expanding area, and a slower pressure increase.  And since you are now expanding from a smaller high velocity area, I’m gonna guess that the fractional area of turbulent flow would be larger.

 

The concepts you put together make sense in themselves, but it seems to me a little like adding apples and oranges to get more apples.  So, more proof of concept is required; well, at least to convince me.

 

Have you made any measurements of the flow distribution at the core exit?

 

Just my opinion, and, of course nothing personal.

 

Best,

 

Al (off to Baja for a few days of relaxation)