I forgot to copy that URL-- sorry.
http://amber.aae.uiuc.edu/~m-selig/ads.html
Regards, Neil Tucson, AZ
-----Original Message-----
From: Albaugh, Neil
Sent: Wednesday, January 23, 2002 10:46 AM
To: 'Waldron, James'; 'land-speed@autox.team.net'
Subject: RE: Reynolds numbers
Jim;
You might look at this site for aerodynamic info. It has links to other
sites with data on airfoils and aerodynamic analysis software.
Regards, Neil Tucson, AZ
-----Original Message-----
From: Waldron, James [mailto:James.Waldron@CWUSA.COM]
Sent: Monday, January 21, 2002 2:31 PM
To: 'land-speed@autox.team.net'
Subject: Reynolds numbers
So, longer than I'd like to admit ago, when I studied this sort of thing in
college, I remember that there were two components to determining how fast
something would go on a certain amount of power. One was the sum of the
'frictions' that had to be overcome (bearings, rolling resistance, etc.),
and the other was the air resistance. When you were going slowly, the first
friction was the biggest, but as you started going faster and faster air
resistance became the dominant player. Air resistance was cubic, related to
speed, and was determined by a 'Reynolds' number that related (it starts
getting fuzzy here) the resistance of the shape of the object to an
equivalent flat plate. Then something about a 1 foot square flat plate
being some sort of standard. ANYWAY, I remember asking how Reynolds
numbers could be determined and being told that it was way too complex to
calculate and that most were determined experimentally by using scale models
in wind tunnels (and for cars, further complicated by the fact that the body
under investigation was close to the ground - not up in the sky - and the
model ground had to move at speed to get real information, and after
thinking about using my belt sander to simulate moving ground in the college
aerospace model wind tunnel, and the look I got from the dean when I told
him I wanted to put a running belt sander with 80 grit sandpaper in the wind
tunnel and 'didn't think it could get loose'..... You get the picture.)
So, what I want to know is, in this day of lots of computing horsepower on
my desktop, are there any programs that can be fed a 3 dimensional object,
can simulate air flow, and determine Reynolds numbers? And, of course, I'd
like to play with the design on-the-fly to see what needs to be done to
minimize the drag. Or, are we still in the days of 'take it to the salt and
see what it will do?', record the speed and calculate to determine my own
Reynolds number (if I still care at that point)? I know that the Americas
Cup Yacht guys do lots of computer simulation, but also still use a scale
model moving through a tank of water (water is a lot thicker than air, but
except for compressibility, fluid dynamics should still apply?). Anyone
have any sources of information?
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