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Old 07-12-2008, 08:00 PM   #31 (permalink)
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For Reynolds number use 2,500,000. At car speeds, and since this is air, the Reynolds number is always going to be around this for what we are interested in. dt is the time step of the movie, so keep it small. Gravity doesn't play into this simulation, so your top down view will work fine (you just wont see the effect of the air moving under and over the vehicle.

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Old 07-13-2008, 02:02 AM   #32 (permalink)
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adrive7: Thanks, the VLC program worked like a charm.

here's a few vids of old Harold in action.
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Old 07-14-2008, 12:02 AM   #33 (permalink)
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Quote:
Originally Posted by cfg83 View Post
Chris -

I processed yours and put it on YouTube :



I made the Taco smaller and put a road underneath.

I'll delete it from YouTube if you want me to.

CarloSW2
right on, thanks..

how did you get it to work? I wasn't clear on the settings..

can you send it to me? PentastarTurbo@aol.com

for the record, VLC didn't play it for me already had it..
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Old 07-14-2008, 12:36 AM   #34 (permalink)
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Chris D -

The only value I changed was the time. I changed it to 40 seconds. Now I think the YouTube is wrong because, according to adrive7, the Re needs to be 2,500,000.

Quote:
Originally Posted by Chris D. View Post
right on, thanks..

how did you get it to work? I wasn't clear on the settings..

can you send it to me? PentastarTurbo@aol.com

for the record, VLC didn't play it for me already had it..
I will do the same analysis with an Re of 2500000 and send you an e-mail.

CarloSW2
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Old 07-14-2008, 12:44 AM   #35 (permalink)
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This is just too much fun!!! Totally found my new favorite toy .


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Old 07-14-2008, 02:06 AM   #36 (permalink)
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co_driver -

Quote:
Originally Posted by co_driver View Post
Numbers to use:
L* = effective diameter of your car [1990 Firebird: (72.4" (width) * 49.8" (height) )^0.5 = ~60" = 1.53 m]
v = velocity [50 mph = 22.35 m/s]
'nu' = 1.6*10^-5 m^2/s

Thus: Re = 1.53 * 22.35 / 1.6*10^-5 = ~2,100,000

(*) Note:
A better reference would be the effective diameter rather than its length, as length is used for flat plates.

Now, on to making 2-D renditions of vehicles I have once owned...
I'll plug my SW2 numbers in :

L* = effective diameter of my car
[1999 Saturn SW2: (66.7" (width) * 54.5" (height) )^0.5 = ~60.29" => 1.53 m]
======> Same as Firebird Example, so the rest of my numbers will be the same.

v50 = velocity [50 mph = 22.35 m/s]
v55 = velocity [55 mph = 24.59 m/s]
v60 = velocity [60 mph = 26.82 m/s]
v65 = velocity [65 mph = 29.06 m/s]

'nu' = 1.6*10^-5 m^2/s

Thus: Re50 = 1.53 * 22.35 / 1.6*10^-5 = ~2,140,000
Thus: Re55 = 1.53 * 24.59 / 1.6*10^-5 = ~2,350,000
Thus: Re60 = 1.53 * 26.82 / 1.6*10^-5 = ~2,560,000
Thus: Re65 = 1.53 * 29.06 / 1.6*10^-5 = ~2,780,000

I've been using 2,500,000 for my second run, so that means I've been calculating for a little under 60 MPH.

Based on the above, I have attached a super-simple Reynolds Number calculator using Microsoft Excel. Enjoy!

CarloSW2
Attached Files
File Type: xls Reynolds_Number_Calculator.xls (13.5 KB, 60 views)
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Old 07-14-2008, 04:08 AM   #37 (permalink)
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You know I was just curious :

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Old 07-14-2008, 11:09 AM   #38 (permalink)
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I'm getting some interesting movies using the high Re numbers.

I get a lot of this:


using 2,500,000. Is it supposed to look like that?
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Old 07-14-2008, 11:10 AM   #39 (permalink)
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Quote:
Originally Posted by i_am_socket View Post
I'm getting some interesting movies using the high Re numbers.

I get a lot of this:


using 2,500,000. Is it supposed to look like that?
2000 era mustang, cool

mite have some slight color differences on the background causing the turbulence..

mite have to go over the whole background in one color, try that and repost it..
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Old 07-14-2008, 11:15 AM   #40 (permalink)
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Here's the source image:


2 bit, no antialiasing. I'll try bumping it up to 8 bit.

*EDIT*

Here's the video on 8 bit. (haven't figured out the embedding thing yet)

http://www.youtube.com/v/7w_nCKP-co4

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