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kuffel(at)cyberport.net
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 Posted: Sun Dec 14, 2008 2:01 pm Post subject: VG research |
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The NASA research on VGs which I read over 30 years ago concluded the best
spanwise spacing occurred when the vortices generated just met at the
training edge of the wing. The vortices spread from each generator at an
included angle of 15 degrees. Thus, the farther forward the generators, the
farther apart they can be and still be fully effective.
Don't remember the details about chordwise location but they ended up at
10% - 15% of local chord.
Whenever I get my FireStar flying I'll use these numbers as a starting point
for my VG experimenting.
Tom Kuffel
Whitefish, MT
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icrashrc
Joined: 16 Mar 2006
Posts: 247
Location: Mishawaka, In
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| Posted: Mon Dec 15, 2008 12:43 am Post subject: Re: VG research |
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Tom,
If the best location chordwise is when the vortices meet at the trailing edge then couldn't you calculate backwards from the TE to find the sweet spot for mounting the VG's?
| kuffel(at)cyberport.net wrote: | The NASA research on VGs which I read over 30 years ago concluded the best
spanwise spacing occurred when the vortices generated just met at the
training edge of the wing. The vortices spread from each generator at an
included angle of 15 degrees. Thus, the farther forward the generators, the
farther apart they can be and still be fully effective.
Don't remember the details about chordwise location but they ended up at
10% - 15% of local chord.
Whenever I get my FireStar flying I'll use these numbers as a starting point
for my VG experimenting.
Tom Kuffel
Whitefish, MT |
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Scott
www.ill-EagleAviation.com
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kuffel(at)cyberport.net
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| Posted: Tue Dec 16, 2008 12:26 am Post subject: VG research |
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Scott,
<< If the best location chordwise is when the vortices meet at the trailing
edge then couldn't you calculate backwards from the TE to find the sweet
spot for mounting the VG's? >>
kuffel(at)cyberport.net wrote:
<< best spanwise spacing occurred when the vortices generated just met at
the training edge of the wing. The vortices spread from each generator at
an included angle of 15 degrees. >>
Not really. There are two independent variables, spanwise spacing and chord
location. Once you decide on a given chord location then geometry does tell
you the minimum useful spanwise spacing. Any more generators than this
minimum spacing will not improve matters and might make things worse. Don't
remember how NASA (actually it might have been a NACA report) decided on
10% - 15% of chord for subsonic wings but that range seems to be what is
used by all the VG vendors, both experimental and certified.
Tom Kuffel
Whitefish, MT
Building Original FireStar
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