Author Topic: Nice wind tunnel shot  (Read 30748 times)

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Offline Jack Gifford

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Re: Nice wind tunnel shot
« Reply #15 on: April 30, 2014, 12:48:26 AM »
I assume that drag force versus airspeed is measured during windtunnel testing. Are those numbers highly-guarded secrets for the StupidBaker?
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Offline Bob Drury

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Re: Nice wind tunnel shot
« Reply #16 on: April 30, 2014, 02:58:37 AM »
  WOW!!!
  That is beautiful to watch.  I sure hope someone gets the chance to put a stock bodied Stude in a wind tunnel in my lifetime.
  It could answer a lot of Stude Aero questions that have been argued about since 1953!                              One Run, out...................
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Offline Seldom Seen Slim

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Re: Nice wind tunnel shot
« Reply #17 on: April 30, 2014, 07:49:58 AM »
Jack:  A couple of years ago, when the A2 tunnel was just getting up and running, one of the guys at the tunnel spent quite a bit of time here on the forum.  Here told us lots of stuff about this-n-that, including that the data learned was exclusively for the team's use -- and not his to give out to anyone else.  But - if the team gave him permission to disseminate the data he would/did do so.

He hasn't been on here for quite a while, so I will guess that we'll just have to assume that he's not going to comment on your expressed desire to find out more.  Maybe the Stupidbaker's team will see this and offer something, though.  If you know who they are -- ask 'em, hey?
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Offline floydjer

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Re: Nice wind tunnel shot
« Reply #18 on: May 02, 2014, 10:59:12 AM »
Usually $5 to $10, depending on height.
Here Stan...I don`t need this any longer....www.instantrimshot.com
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Re: Nice wind tunnel shot
« Reply #19 on: May 13, 2014, 01:39:23 PM »
According to conventional wing wisdom it really should not work!  :?
But this is what happens [sometimes] when you deal with hot rodders!  :-o  :-D :cheers:
A lot of research went into this in the 80's and 90's.  If we put a Gurney flap on a wing trailing edge and then fair the upstream side we create an artifact called "trailing edge bluntness".  It was actually pioneered in the 60's by Whitcomb.  The drag of an airfoil is actually reduced by having a little of this depending on Reynolds number: the higher the Rn, the thicker the boundary layer is and the more bluntness works for us. 

Essentially, it delays the closure of the airfoil trailing edge upper and lower boundary layers until farther aft of the physical trailing edge.  So we get the benefit of an aerodynamically longer chord without the drag of longer chord, at the expense of some trim drag due to higher negative wing moment.  It also can make for a lighter structure, and weight is everything for an aircraft.  The most dramatic example currently is the G-650.

It takes pretty high end CFD to accurately model this effect and a lot tighter mesh than most people are willing to run.  It's not magic, it is well known aero for 30-40 years that is in wide use.

As for un-faired Gurney flaps, they are in use on many small aircraft to stiffen the trailing edge of control surfaces.  T shaped flaps on the rudder of many small aircraft prevent flutter and unload the control forces at minimal drag penalty.  Conversely, many composite kit aircraft use way too much trailing edge bluntness because the bondo jockey who built it got lazy.  For under 10M Rn, 0.5% chord is about right.

Offline Bratfink

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Re: Nice wind tunnel shot
« Reply #20 on: July 30, 2014, 09:20:20 AM »
According to conventional wing wisdom it really should not work!  :?
But this is what happens [sometimes] when you deal with hot rodders!  :-o  :-D :cheers:
A lot of research went into this in the 80's and 90's.  If we put a Gurney flap on a wing trailing edge and then fair the upstream side we create an artifact called "trailing edge bluntness".  It was actually pioneered in the 60's by Whitcomb.  The drag of an airfoil is actually reduced by having a little of this depending on Reynolds number: the higher the Rn, the thicker the boundary layer is and the more bluntness works for us. 

Essentially, it delays the closure of the airfoil trailing edge upper and lower boundary layers until farther aft of the physical trailing edge.  So we get the benefit of an aerodynamically longer chord without the drag of longer chord, at the expense of some trim drag due to higher negative wing moment.  It also can make for a lighter structure, and weight is everything for an aircraft.  The most dramatic example currently is the G-650.

It takes pretty high end CFD to accurately model this effect and a lot tighter mesh than most people are willing to run.  It's not magic, it is well known aero for 30-40 years that is in wide use.

As for un-faired Gurney flaps, they are in use on many small aircraft to stiffen the trailing edge of control surfaces.  T shaped flaps on the rudder of many small aircraft prevent flutter and unload the control forces at minimal drag penalty.  Conversely, many composite kit aircraft use way too much trailing edge bluntness because the bondo jockey who built it got lazy.  For under 10M Rn, 0.5% chord is about right.

What he said.

How come the guys in these tunnels never hold the smoke generator close to the floor?.

I want to see the air flow around the splitter. :-D

That's normally because they do this in fixed ground tunnels with a taller than recommended boundary layer ;-)

Offline SpeedThrills

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Re: Nice wind tunnel shot
« Reply #21 on: March 01, 2015, 08:54:31 AM »
How come the guys in these tunnels never hold the smoke generator close to the floor?.

I want to see the air flow around the splitter. :-D

That's normally because they do this in fixed ground tunnels with a taller than recommended boundary layer ;-)
[/quote]
I have no knowledge in this area, but I've always thought that it would be interesting to have a smoke wand out in front of a moving car, on the track. A car sitting still and its wheels not turning, has to be much different aerodynamically than a car moving down the track.  I suppose it would be hard to achieve this, from a mechanical standpoint.
Either that, or someone needs to design a wind tunnel with a 500 mph floor! :-o
"Sweet music, the internal combustion orchestra."

Offline manta22

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Re: Nice wind tunnel shot
« Reply #22 on: March 01, 2015, 11:35:31 AM »
It shouldn't be hard at all-- simply mount a long tube sticking out in front of the car and pump smoke through it, letting the smoke flow back over the car as it travels forward.

Regards, Neil  Tucson, AZ
Regards, Neil  Tucson, AZ

Offline Peter Jack

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Re: Nice wind tunnel shot
« Reply #23 on: March 01, 2015, 12:03:32 PM »
That's why the Formula 1 guys all use Flo Viz paint. It's out there in the real world at speed.  :-D :-D :-D

Pete

Offline SpeedThrills

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Re: Nice wind tunnel shot
« Reply #24 on: March 01, 2015, 02:22:20 PM »
It shouldn't be hard at all-- simply mount a long tube sticking out in front of the car and pump smoke through it, letting the smoke flow back over the car as it travels forward.

Regards, Neil  Tucson, AZ

There would be a lot of forces on that tube.  I wonder if it's been done?
"Sweet music, the internal combustion orchestra."

Offline jl222

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Re: Nice wind tunnel shot
« Reply #25 on: March 01, 2015, 06:45:59 PM »

  I always wondered why they don't have the smoke coming out of a manifold as wide as the vehicle?

                JL222

Offline Peter Jack

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Re: Nice wind tunnel shot
« Reply #26 on: March 01, 2015, 08:45:00 PM »
I would think that the manifold running across the front would seriously affect the air flow.

Pete

Offline floydjer

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Re: Nice wind tunnel shot
« Reply #27 on: March 06, 2015, 08:59:11 AM »
I`d never advocate drugs,alcohol,violence or insanity to anyone...But they work for me.

Offline GH

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Re: Nice wind tunnel shot
« Reply #28 on: September 25, 2015, 06:15:16 PM »
I seem to remember that there was a yellow stude back about 2006 that had about the same front end and it made too much down force and they had front tire trouble.

Offline manta22

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Re: Nice wind tunnel shot
« Reply #29 on: September 25, 2015, 07:43:09 PM »
I would think that the manifold running across the front would seriously affect the air flow.

Pete

Pete;

I think the trick is to use streamline tubing for the manifold.

Regards, Neil  Tucson, AZ
Regards, Neil  Tucson, AZ