REFLECTOR: Vortilions and/or VG's?

[Al Gietzen]

VGs energize the boundary layer and keep it attached longer and so delay 

the onset of stall. I've never heard of them doing anything measurable 

to inhibit spanwise flow. Vortilons OTOH were put there specifically to 

inhibit spanwise flow and are most active on the lower (high pressure) 

wing surface. I don't know how they delay boundary layer separation 

except as an incidental benefit of reduced spanwise flow.

 

IIRC vortilons and VGs pretty much address different issues ... Jim S.

 

I'll respectfully disagree on this one.  Tuft testing by the guys here in
the San Diego EZ-squadron (on both Vari-EZ and Long-EZ) found that the ONLY
span-wise flow that showed up was on the upper surface of the wing, under
where the flow had separated at high AOA.  It would begin inboard near the
fuselage, and spread outward (and thicken) as AOA increased.  

 

I also recall reading (I don't know where) that the reason Rutan added the
vortilons was to create vortices OVER the wing at high AOA to provide better
aileron authority (presumable because it inhibited span-wise flow near the
trailing edge which 'masked' the ailerons).

 

I think it reasonable to extrapolate that behavior to the Velocity wing.

 

Al

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