Re: Vortex generators on engine nacells?

From:         David Lednicer <dave@amiwest.com>
Organization: Analytical Methods, Inc.
Date:         07 Jul 96 14:09:03 
References:   1 2
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Jop Vlaskamp wrote:
> " Sorts of strakes:
> 1) Strakes placed on the fuselage: to maintain the directional control
> during large slip-angles.

	Actually, fuselage strakes are for maintaining directional
control at high angles of attack (DC-9-50, MD80 and MD87)

> 2) Strakes mounted on the tail engine (DC-10): to create a nose-down
> pitching moment.

	The DC-10 #2 engine doesn't have strakes - I think you are
getting this confused with the MD80 and MD87, which do have strakes on
the engine nacelles.

> 3) Strakes on the wing-engines (B737): Reduce the local stall speed in this
> area at large angles of attack."
>
> I know that smaller planes, with which I am more familiar, have similar
> devices. For example the Piper PA-28-161 Warrior and the Piper Arrow have
> "stall strips". Those are strips placed on the leading edge of the wing.
> The airflow becomes a turbulent one when it passes the strip. A turbulent
> airflow has more energy than a laminar one (I know, it sounds like a
> contradiction), and therefore "sticks" to the wing better. It prevents the
> airflow from separating from the wing and thus the part where they are
> installed from stalling.

	No, stall strips do just the opposite.  They lower the angle of
attack that that part of the wing stalls at, to produce a better stall,
predictable stall pattern, compared to the unmodified wing.

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David Lednicer             | "Applied Computational Fluid Dynamics"
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