REFLECTOR:Vortex Generators on XL
KeithHallsten
reflector@tvbf.org
Sat, 6 Dec 2003 22:39:33 -0800
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Alex,
It sounds like we are just mincing words here. "Mixing high energy flow =
with the boundary layer" sounds a whole lot like turbulent flow to me!! =
If there's some subtle difference, I'm afraid it's lost on me. It seems =
to me that the flow layer along the skin is energized by the turbulence =
imparted by the VGs! At any rate, I think we both have a fairly clear =
concept of what the VGs are doing.=20
Keith
----- Original Message -----=20
From: Alex Balic=20
To: reflector@tvbf.org=20
Sent: Saturday, December 06, 2003 4:45 PM
Subject: RE: REFLECTOR:Vortex Generators on XL
Keith,=20
You are correct about the way that VG's work for the most part, and I =
was hoping not to start a really big discussion about this, but I =
suppose that is the intent of this news group. The reason that laminar =
flow is lost, is because skin friction slows the airflow within about =
.01 or so the surface the surface of the wing. This flow, lacking =
kinetic energy (relative to the surface of the wing) is drawn into the =
negative pressure area above the wing, separates from the surface, and =
becomes turbulent. Vortex generators are designed to mix the air that =
still contains energy (which fortunately is close to the wing surface) =
with the low energy air at the wing surface, and thereby maintaining =
laminar flow further back into the negative pressure area than would be =
possible without this mixing. If you look at a wind tunnel test you =
will see the vortices moving wildly back across the wing, but upon close =
inspection, there is an energized layer of laminar flow against the =
skin. This extended laminar flow is what the vortices make possible, and =
what keeps the wing flying at a higher angle of attack.
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<DIV><FONT face=3DArial size=3D2>Alex,</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT> </DIV>
<DIV><FONT face=3DArial size=3D2>It sounds like we are just mincing =
words=20
here. "Mixing high energy flow with the boundary layer" sounds a =
whole lot=20
like turbulent flow to me!! If there's some subtle difference, I'm =
afraid=20
it's lost on me. It seems to me that the flow layer along the skin =
is=20
energized by the turbulence imparted by the VGs! At any rate, I =
think we=20
both have a fairly clear concept of what the VGs are doing. =
</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT> </DIV>
<DIV><FONT face=3DArial size=3D2>Keith</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT> </DIV>
<BLOCKQUOTE dir=3Dltr=20
style=3D"PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; =
BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">
<DIV style=3D"FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV=20
style=3D"BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: =
black"><B>From:</B>=20
<A title=3Dalex157@direcway.com =
href=3D"mailto:alex157@direcway.com">Alex=20
Balic</A> </DIV>
<DIV style=3D"FONT: 10pt arial"><B>To:</B> <A =
title=3Dreflector@tvbf.org=20
href=3D"mailto:reflector@tvbf.org">reflector@tvbf.org</A> </DIV>
<DIV style=3D"FONT: 10pt arial"><B>Sent:</B> Saturday, December 06, =
2003 4:45=20
PM</DIV>
<DIV style=3D"FONT: 10pt arial"><B>Subject:</B> RE: REFLECTOR:Vortex =
Generators=20
on XL</DIV>
<DIV><FONT face=3DArial size=3D2></FONT><FONT face=3DArial =
size=3D2></FONT><FONT=20
face=3DArial size=3D2></FONT><FONT face=3DArial size=3D2></FONT><FONT =
face=3DArial=20
size=3D2></FONT><FONT face=3DArial size=3D2></FONT><BR></DIV>
<DIV><SPAN class=3D243531900-07122003><FONT face=3DArial =
color=3D#0000ff=20
size=3D2>Keith, </FONT></SPAN></DIV>
<DIV><SPAN class=3D243531900-07122003><FONT face=3DArial =
color=3D#0000ff size=3D2>You=20
are correct about the way that VG's work for the most part, and I was =
hoping=20
not to start a really big discussion about this, but I suppose that is =
the=20
intent of this news group. The reason that laminar flow is lost, =
is=20
because skin friction slows the airflow within about .01 or=20
so the surface the surface of the wing. This flow, lacking =
kinetic=20
energy (relative to the surface of the wing) is drawn into the =
negative=20
pressure area above the wing, separates from the surface, and becomes=20
turbulent. Vortex generators are designed to mix the air =
that still=20
contains energy (which fortunately is close to the wing=20
surface)</FONT></SPAN><SPAN class=3D243531900-07122003><FONT =
face=3DArial=20
color=3D#0000ff size=3D2> with the low energy air at the wing surface, =
and thereby=20
maintaining laminar flow further back into the negative pressure area =
than=20
would be possible without this mixing. If you look at a wind =
tunnel test=20
you will see the vortices moving wildly back across the wing, but upon =
close=20
inspection, there is an energized layer of laminar flow against the=20
skin. This extended laminar flow is what the vortices make =
possible,=20
and what keeps the wing flying at a higher angle of=20
attack.</FONT></SPAN></DIV></BLOCKQUOTE></BODY></HTML>
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