The stagnation point at the leading edge contains slow-moving, slightly compressed air. This sounds ideal for laminar flow control. This slow air will create little losses in ducts, and it's pressure allows it to be blown out of slots to reenergize the boundary layer, while at the same time removing contamination - a MAJOR issue for laminar flow today. Is this true?

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    $\begingroup$ Don't accept an answer immediatey. Better to wait until more answers have collected and errors have been pointed out and corrected. $\endgroup$ – Peter Kämpf Jun 14 '20 at 10:01


Slow-moving also means low mass flow. In order to re-energize the boundary layer, the air has to move fast, meaning high mass flow. Also, speed means reduced pressure, so the stagnation pressure is not sufficient to produce that desired high-energy flow.

Also, contamination (bugs, ice) accretes close to the stagnation point. Ideally, in order to remove contamination, blowing would have to happen across the stagnation point. For that, blowing pressure needs to be higher than stagnation pressure.

The only use of stagnation pressure for boundary layer control is for tripping by blowing perpendicularly to the surface into the boundary layer. This works with low mass flows already.


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