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

Reply  Post New Thread
 
Submit Tools LinkBack Thread Tools
Old 02-28-2013, 01:28 PM   #491 (permalink)
Master EcoModder
 
3-Wheeler's Avatar
 
Join Date: Dec 2008
Location: Southern WI
Posts: 827

AlienMobile - '00 Honda Insight
Team Honda
90 day: 80.05 mpg (US)
Thanks: 101
Thanked 560 Times in 191 Posts
Quote:
Originally Posted by aerohead View Post
.....I've ignored the 'noses' per se,as they are always discounted in Fluid Mechanics,and rather place the greater emphasis on the aft-body portion......
Phil,

Well, at first thought this statement makes sense. The exact shape of the "nose" may not be especially critical, since it's on the leading edge of our "aero" shape.

However when you look at the dimensions for length/width in the streamlining template, the "length" of the nose becomes part of the 2.5:1 length/width definition.

http://ecomodder.com/forum/358696-post490.html

So it seems that the nose shape is "critical" at least when it comes to understanding the ideal "wing shape" that you have proposed many times here.

Jim.

  Reply With Quote
Alt Today
Popular topics

Other popular topics in this forum...

   
Old 03-01-2013, 06:23 PM   #492 (permalink)
Master EcoModder
 
aerohead's Avatar
 
Join Date: Jan 2008
Location: Sanger,Texas,U.S.A.
Posts: 15,861
Thanks: 23,922
Thanked 7,207 Times in 4,640 Posts
dashed lines

Quote:
Originally Posted by sgtlethargic View Post
Aerohead,
Will you please take a few minutes and explain the dashed lines, especially the one I marked? I think I understand the other dashed lines to represent the top (plan) view.
The outer-most dashed lines define the forebody of the original 'donar' 2.5:1 streamline body of revolution in its entirety.
I 'reduced' the nose section to more of a 1/2 convex hemisphere,rather than the prolate ellipsoid original,as every reference I have for automotive streamlining effectively discounts the entire forebody.The 1/2-hemi 'bulbous'-nose has demonstrated lowest drag for crosswind conditions,so it became the 'default' forebody.
--------------------------------------------------------------------------
The premise for the 'Template' was the extremely careful handling of the airflow over the aft-body which prevents separation,which is what all aerodynamicists agree is THE target for streamlining.In this respect,the nose is of little import to us.
__________________
Photobucket album: http://s1271.photobucket.com/albums/jj622/aerohead2/
  Reply With Quote
The Following 2 Users Say Thank You to aerohead For This Useful Post:
COcyclist (03-04-2013), sgtlethargic (03-02-2013)
Old 03-01-2013, 06:27 PM   #493 (permalink)
Master EcoModder
 
aerohead's Avatar
 
Join Date: Jan 2008
Location: Sanger,Texas,U.S.A.
Posts: 15,861
Thanks: 23,922
Thanked 7,207 Times in 4,640 Posts
"nose"

Quote:
Originally Posted by 3-Wheeler View Post
Phil,

Well, at first thought this statement makes sense. The exact shape of the "nose" may not be especially critical, since it's on the leading edge of our "aero" shape.

However when you look at the dimensions for length/width in the streamlining template, the "length" of the nose becomes part of the 2.5:1 length/width definition.

http://ecomodder.com/forum/358696-post490.html

So it seems that the nose shape is "critical" at least when it comes to understanding the ideal "wing shape" that you have proposed many times here.

Jim.
Absolutely!
If we were doing a body in white,we'd need to consider the 'whole' vehicle.
The 'Template' was to be only an aid for aft-body streamlining,as I've no idea how we could modify existing production cars to mimic the 2.5:1 full nose.
__________________
Photobucket album: http://s1271.photobucket.com/albums/jj622/aerohead2/
  Reply With Quote
The Following User Says Thank You to aerohead For This Useful Post:
sgtlethargic (03-02-2013)
Old 03-01-2013, 10:46 PM   #494 (permalink)
Master EcoModder
 
freebeard's Avatar
 
Join Date: Aug 2012
Location: northwest of normal
Posts: 27,561
Thanks: 7,736
Thanked 8,554 Times in 7,041 Posts
Quote:
If we were doing a body in white,we'd need to consider the 'whole' vehicle.
The 'Template' was to be only an aid for aft-body streamlining,as I've no idea how we could modify existing production cars to mimic the 2.5:1 full nose.
...existing production cars...

There's your problem.
  Reply With Quote
Old 03-02-2013, 12:45 AM   #495 (permalink)
Master EcoModder
 
freebeard's Avatar
 
Join Date: Aug 2012
Location: northwest of normal
Posts: 27,561
Thanks: 7,736
Thanked 8,554 Times in 7,041 Posts
I couldn't resist putting that in Photoshop. Here it is with the rear track reduced 6-8" and the body pie cut.


I couldn't do a lot more with that view. It needs some curve to the drip rail and beltline. But here's a teardrop body on a COE.


The Type II doors have a separable window frame. So you could take that off and add a curve to the opening. In fact, you could bring the rebody right to the windshield header and eliminate the overhang, like a Barndoor bus.
  Reply With Quote
Old 03-02-2013, 02:55 PM   #496 (permalink)
Master EcoModder
 
aerohead's Avatar
 
Join Date: Jan 2008
Location: Sanger,Texas,U.S.A.
Posts: 15,861
Thanks: 23,922
Thanked 7,207 Times in 4,640 Posts
Aerodynamic Streamlining Template Gen-II

This Generation-II 'Template' was 'built' from a different L/D= 2.5 streamline body of revolution.I've identified it's source within the image.
*As a 'free-air' body,it would have Cd 0.04
*As a half-body in mirror-image ground proximity it would have Cd 0.08.
*Adding wheels would bump it up to around Cd 0.13
*Adding wheel fairings would lower the Cd.
---------------------------------------------------------------------------
*I'll show it as a full half-body with 'full' nose.
*And as a 'Template' with shortened nose.I added an extra side window to help distinguish it from the Gen-I 'Template.'
--------------------------------------------------------------------------
*As a 'Template' it is intended as an aid for separation-free aft-body streamlining only.
*From Hucho,"...the shape of a body in front of the largest cross-section has only minor influence on the total drag.The main contributions to the drag force originate from the rear part of the body.It is not important to find a proper shape to divide the oncoming flow but it is very important to design a rear body surface which brings the divided streamlines smoothly together.
...low drag can only be achieved when the separation at the rear is eliminated.
Shapes of this kind are aerofoils and 'streamlined' bodies."

__________________
Photobucket album: http://s1271.photobucket.com/albums/jj622/aerohead2/
  Reply With Quote
The Following 3 Users Say Thank You to aerohead For This Useful Post:
freebeard (03-02-2013), KamperBob (03-03-2013), sgtlethargic (03-02-2013)
Old 03-02-2013, 04:00 PM   #497 (permalink)
Master EcoModder
 
freebeard's Avatar
 
Join Date: Aug 2012
Location: northwest of normal
Posts: 27,561
Thanks: 7,736
Thanked 8,554 Times in 7,041 Posts
Thanks, I saved it as '-->Scan12' so I can find it again.

One would think the only caveat on the forebody would be that it not set up adverse streamlines. I need a word that means 'rotational around the axis in the direction of travel'. Or would those smooth out under the soothing effect of the afterbody?

Wasn't it Tesla that was trying to find a mathematical description of that curve?
  Reply With Quote
Old 03-02-2013, 04:35 PM   #498 (permalink)
Master EcoModder
 
aerohead's Avatar
 
Join Date: Jan 2008
Location: Sanger,Texas,U.S.A.
Posts: 15,861
Thanks: 23,922
Thanked 7,207 Times in 4,640 Posts
forebody

Quote:
Originally Posted by freebeard View Post
Thanks, I saved it as '-->Scan12' so I can find it again.

One would think the only caveat on the forebody would be that it not set up adverse streamlines. I need a word that means 'rotational around the axis in the direction of travel'. Or would those smooth out under the soothing effect of the afterbody?

Wasn't it Tesla that was trying to find a mathematical description of that curve?
*It's funny about the forebody.Hucho beat up on M'o'ller for giving the original VW van so much radius up front.
*He cites F.W.Palowski of 1930,who demonstrated that once the radius was enough to maintain flow attachment,that any further rounding returns zero drag improvement.
*He applauds the Vanagon and it's 'optimised' radius,which worked out at 0.045 X body width.He shows a drag curve which he probably created himself,which clearly shows no additional improvement in drag with larger radii.
------------------------------------------------------------------------
Their does appear to be a CAVEAT back in the commercial vehicle chapter,showing the bulbous nose to have the lowest drag in crosswind.
*GM published the same findings in the early 1960s.(there's a pictorial drag table of that work at the 'full-boat-tail trailer' thread)
------------------------------------------------------------------------
There would be a mathematical formula for these profiles.A visit to the Math Dept. at the local university might fill in that blank.Volunteers?
-----------------------------------------------------------------------
The streamlined bodies are a profile which is revolved around the longitudinal axis.
The noses are described as ellipsoid,and the tail is referred to as a prolate ellipsoid (NFL Regulation footballs are 'prolate-ellipsoids',Cd 0.055 average, while spinning in a perfect spiral pass)
__________________
Photobucket album: http://s1271.photobucket.com/albums/jj622/aerohead2/
  Reply With Quote
Old 03-02-2013, 04:41 PM   #499 (permalink)
Master EcoModder
 
aerohead's Avatar
 
Join Date: Jan 2008
Location: Sanger,Texas,U.S.A.
Posts: 15,861
Thanks: 23,922
Thanked 7,207 Times in 4,640 Posts
Photoshop

Quote:
Originally Posted by freebeard View Post
I couldn't resist putting that in Photoshop. Here it is with the rear track reduced 6-8" and the body pie cut.


I couldn't do a lot more with that view. It needs some curve to the drip rail and beltline. But here's a teardrop body on a COE.


The Type II doors have a separable window frame. So you could take that off and add a curve to the opening. In fact, you could bring the rebody right to the windshield header and eliminate the overhang, like a Barndoor bus.
I envy your command of the graphics software! I struggled here at Copy-Pro over a month of spare time on a single image,going pixel by pixel.
My hat is off to all you masters of the virtual french curve!
__________________
Photobucket album: http://s1271.photobucket.com/albums/jj622/aerohead2/
  Reply With Quote
Old 03-02-2013, 08:23 PM   #500 (permalink)
Master EcoModder
 
kach22i's Avatar
 
Join Date: Jul 2011
Location: Ann Arbor, Michigan
Posts: 4,158
Thanks: 120
Thanked 2,790 Times in 1,959 Posts
I saw this picture below a few days ago, and did not know where to post it.

Random TRANSPORTATION pictures - Page 931 - Pelican Parts Technical BBS


With some glazing and flush wheel flares it could be a low Cd, right?

Needs a tail cone or something.

__________________
George
Architect, Artist and Designer of Objects

1977 Porsche 911s Targa
1998 Chevy S-10 Pick-Up truck
1989 Scat II HP Hovercraft

Chin Spoiler:
http://forums.pelicanparts.com/off-t...effective.html

Rear Spoiler Pick Up Truck
http://forums.pelicanparts.com/off-t...xperiment.html

Roof Wing
http://ecomodder.com/forum/showthrea...1-a-19525.html
  Reply With Quote
Reply  Post New Thread


Thread Tools


Similar Threads
Thread Thread Starter Forum Replies Last Post
Maximum angle for boat tail? abcdpeterson Aerodynamics 80 11-03-2021 12:55 PM
Aerodynamic Streamlining Template Part-B aerohead Aerodynamics 8 05-31-2013 12:23 PM
LED Headlight captainslug DIY / How-to 82 11-15-2011 01:32 AM
Aerodynamic Streamlining Template: Part-A aerohead Aerodynamics 0 07-18-2009 02:37 PM
All items I scanned in the new product showcase dremd The Lounge 0 11-08-2008 04:14 PM



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