REFLECTOR: VG's

[Lawrence Epstein]

The fact is, (on even the best designed wing) laminar flow is only present
for a part of the wing. at some point, the flow separates and becomes
turbulent anyway. When this happens, there is no (much less) airflow over
that part of the wing that is downwind. If it happens to be the part that
includes the aileron or elevator, you lose effectiveness of that control
surface.
Properly placed VG's don't decrease (by much) the wing area that "sees"
laminar flow (in fact, may increase), they cause a local turbulence"just
ahead" of where the flow would have separated anyway. That turbulence
causes a local low pressure which "pulls" the airflow back down to the
surface of the wing (where you may get a return to laminar flow) and
thereby increases the efficacy of the control surface (or the net lift of
the wing).

Some VG's can actually *decrease *the induced drag of the wing.



On Thu, Jun 7, 2012 at 4:41 PM, Mark Magee <edjonesbrady at gmail.com> wrote:

> All,
> I think David frames the problem properly from the original thread
> (italics added):
>
> -------------------------------------------------------------------------------------------------------------
> On 6/6/2012 11:06 PM, David Ullman wrote:
> I now have about 27 hours on 444DX.  Getting things sorted out.  I have
> been
> to 10,500 ft and over 200kts (in a dive).  I have done both low and
> power-on
> mushes.  I cant call them stalls as it doesn't.  Around 50 kts it just
> mushes.  I still have roll and yaw control all the way down.  Overall the
> plane is very easy to handle at any speed.  I hate the thought that this
> may
> be due to the vortex generators. * I just cant intellectually get past the
> fact that I have put vortex generators on a laminar flow surface.*
>
>
> --------------------------------------------------------------------------------------------------------------
>
> I can't either. A laminar flow surface and wings are designed to -avoid-
> turbulent flow of all types, particularly vortexes.
> One reason they go so fast.
> In my mind applying VG's to a Velo is like the old F-4's flying around
> full throttle with the drag chute deployed in flight.
>
> Mark
>
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