Reverse NACA duct??

[gossend]

Anyone use a reverse naca duct to provide better air exit on the sides of the cowl? Is it effective??

[deene]

Dick, here is some interesting NASCAR info on this subject:

https://www.google.com/url?sa=t&rct=...YeHgWG-1UqXy10

[Toobuilder]

Studies showed long ago that a "backwards" NACA duct is sub optimal as an exhaust. There are more effective and lower drag methods to vent air overboard.

And concerning the good ol boy on the NASCAR vid - the ducts he showed did not display the very important design elements of a NACA duct - he showed a "caracature" of a NACA duct, at best.

[gossend]

OK, thanks for that, but what "more effective and lower drag methods to vent air overboard" would you suggest?

[Toobuilder]

Essentially you are looking to align exhaust with the localized freestream speed and direction. Tons of threads on this subject. Might start with DanH and his "shrinking exit" thread.

[bjdecker]

Nothing numerical but an interesting video showing the effect of reverse NACA duct evacuating a smoke filled chamber.

https://www.youtube.com/watch?v=RzbI...=RuskiWeld****

Fast Forward to 9:20.

B