Go Back   EcoModder Forum > EcoModding > Aerodynamics
Register Now
 Register Now
 

Reply  Post New Thread
 
Submit Tools LinkBack Thread Tools
Old 07-12-2008, 08:00 PM   #31 (permalink)
EcoModding Lurker
 
adrive7's Avatar
 
Join Date: May 2008
Location: DC Metro
Posts: 48

Ranger - '08 Ford Ranger XL
90 day: 20.73 mpg (US)
Thanks: 0
Thanked 0 Times in 0 Posts
Send a message via AIM to adrive7
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.

__________________
Ohio State Baja SAE
  Reply With Quote
Alt Today
Popular topics

Other popular topics in this forum...

   
Old 07-13-2008, 02:02 AM   #32 (permalink)
Awesomeness personified
 
AndrewJ's Avatar
 
Join Date: Dec 2007
Location: Columbia, MO
Posts: 642

Harold - '94 Honda Civic CX
90 day: 54.51 mpg (US)

Margot - '08 Surly Big Dummy
Thanks: 0
Thanked 28 Times in 18 Posts
Send a message via AIM to AndrewJ
adrive7: Thanks, the VLC program worked like a charm.

here's a few vids of old Harold in action.
__________________
"I got 350 heads on a 305 engine. I get 10 miles to the gallon. I ain't got no good intentions." - The Drive By Truckers.

  Reply With Quote
Old 07-14-2008, 12:02 AM   #33 (permalink)
EcoModding Minded
 
Chris D.'s Avatar
 
Join Date: Jan 2008
Location: Eagan, MN
Posts: 667

Lunar Mist - '02 Toyota Tacoma SR5
90 day: 25.31 mpg (US)

Silver Streak - '08 Toyota Corolla S
90 day: 38.25 mpg (US)
Thanks: 67
Thanked 25 Times in 12 Posts
Send a message via AIM to Chris D.
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..
__________________


  Reply With Quote
Old 07-14-2008, 12:36 AM   #34 (permalink)
Pokémoderator
 
cfg83's Avatar
 
Join Date: Dec 2007
Location: Southern California
Posts: 5,864

1999 Saturn SW2 - '99 Saturn SW2 Wagon
Team Saturn
90 day: 40.49 mpg (US)
Thanks: 439
Thanked 530 Times in 356 Posts
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
__________________

What's your EPA MPG? Go Here and find out!
American Solar Energy Society
  Reply With Quote
Old 07-14-2008, 12:44 AM   #35 (permalink)
Master EcoModder
 
Peakster's Avatar
 
Join Date: Dec 2007
Location: Regina SK Canada
Posts: 407

Red Jeep Patriot - '07 Jeep Patriot
90 day: 25.14 mpg (US)

Beige Ford Ranger - '95 Ford Ranger XLE
Thanks: 0
Thanked 2 Times in 2 Posts
This is just too much fun!!! Totally found my new favorite toy .


Last edited by Peakster; 07-14-2008 at 04:10 AM..
  Reply With Quote
Old 07-14-2008, 02:06 AM   #36 (permalink)
Pokémoderator
 
cfg83's Avatar
 
Join Date: Dec 2007
Location: Southern California
Posts: 5,864

1999 Saturn SW2 - '99 Saturn SW2 Wagon
Team Saturn
90 day: 40.49 mpg (US)
Thanks: 439
Thanked 530 Times in 356 Posts
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, 65 views)
__________________

What's your EPA MPG? Go Here and find out!
American Solar Energy Society
  Reply With Quote
Old 07-14-2008, 04:08 AM   #37 (permalink)
Master EcoModder
 
Peakster's Avatar
 
Join Date: Dec 2007
Location: Regina SK Canada
Posts: 407

Red Jeep Patriot - '07 Jeep Patriot
90 day: 25.14 mpg (US)

Beige Ford Ranger - '95 Ford Ranger XLE
Thanks: 0
Thanked 2 Times in 2 Posts
You know I was just curious :

  Reply With Quote
Old 07-14-2008, 11:09 AM   #38 (permalink)
Ex-lurker
 
i_am_socket's Avatar
 
Join Date: Apr 2008
Location: Jersey
Posts: 571

Skeeter - '05 Toyota Corolla LE
90 day: 35.55 mpg (US)
Thanks: 2
Thanked 8 Times in 6 Posts
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?
__________________
  Reply With Quote
Old 07-14-2008, 11:10 AM   #39 (permalink)
EcoModding Minded
 
Chris D.'s Avatar
 
Join Date: Jan 2008
Location: Eagan, MN
Posts: 667

Lunar Mist - '02 Toyota Tacoma SR5
90 day: 25.31 mpg (US)

Silver Streak - '08 Toyota Corolla S
90 day: 38.25 mpg (US)
Thanks: 67
Thanked 25 Times in 12 Posts
Send a message via AIM to Chris D.
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..
__________________


  Reply With Quote
Old 07-14-2008, 11:15 AM   #40 (permalink)
Ex-lurker
 
i_am_socket's Avatar
 
Join Date: Apr 2008
Location: Jersey
Posts: 571

Skeeter - '05 Toyota Corolla LE
90 day: 35.55 mpg (US)
Thanks: 2
Thanked 8 Times in 6 Posts
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

__________________

Last edited by i_am_socket; 07-14-2008 at 11:26 AM..
  Reply With Quote
Reply  Post New Thread


Tags
air dam, air flow, simulation, spoiler, wind tunnel

Thread Tools


Similar Threads
Thread Thread Starter Forum Replies Last Post
The Mechanism Behind Flow Separation LostCause Aerodynamics 46 07-15-2010 07:38 AM



Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.
Content Relevant URLs by vBSEO 3.5.2
All content copyright EcoModder.com