Friday, April 17, 2009

CFD - Revisited

Keeping boundary conditions and air properties the same, but this time going with a much less aggressive airfoil pattern. NACA3409.


Pressure field looks a lot better...


As does velocity. Flow does start to separate toward the end there, which we can fix... by adding a Gurney flap. If you're not familiar, Google it.

Does pretty much exactly what you'd expect. Extra low pressure zone directly aft of the flap helps suck the air flow back to the foil and moves the separation point further back.


Also, as one would suppose, builds up some stagnation pressure ahead of the flap on the top side of the foil. All in all you still have drag, but should be more downforce.



Pretty bad ass.

Next up will be to try to do some validation work on something simple like a NACA0009 profile to see if it at least captures trends for cD and cL at varying AoA. From there I can look through some airfoil catalogs, pick a handful that look promising and start playing around with increasing their operating envelope and performance level through slats, flaps, and all that good stuff.

1 comment:

Unknown said...

Hey Tom,

Another trick I have learned to do to keep flow attached to the surface is to put a small strip of something like tape near the MAC of the airfoil on the side that is separating. This causes a small amount of turbulence along the surface that keeps the boundary layer following the curve.

Nolan Viljoen