EcoModder Forum Aerodynamic Streamlining Template: Part-C

Register Now
 Remember

 10-01-2013, 09:06 AM #601 (permalink) Master EcoModder   Join Date: Feb 2012 Location: Australia Posts: 355 The Truck - '02 Nissan GU Patrol ST Thanks: 5 Thanked 76 Times in 50 Posts Thanks for that, I still need to play with this equation a bit more. I've been reading a variety of things from Semi-Truck aero through to Belbouth design for engine air intakes, but one thing that struck a chord was rocket nozzle theory. A perfect rocket nozzle will have maximum efficiency when gass departing is at the same pressure as the surrounding atmosphere, if it is higher it is wasted energy, when it is lower pressure it creates drag. From this, in an abstract way I started to look at template theory as an inverted rocket nozzle, the ultimate goal is to leave the air behind the vehicle completely stationary, as if the vehicle had never been there. This equation with the kick in the tail may well be in the vicinity, the rate of change in angle is ever decreasing and then reverses at the end so departure angle at the tail tip is 0, this goes in line with having 0 velocity and ambient pressure at that point. Although most of us will never build a full perfect boattail, but understanding what one is will help us to build an effective Kammback or trailer canopy. We know that perfection lies in the vicinity of the paramaters aerohead has provided, 2.5:1 total ratio, 1.78:1 tail ratio, 22-23° max angle etc., this has been proven experimentally numerous times, so this is the ballpark we need to play in. I think the final equation will incorporate natural constants of growth and decay and be completly logical when we find out what it is, till then keep discussing and debating to get ourselves closer.
 The Following User Says Thank You to Tesla For This Useful Post: aerohead (10-03-2013)
 Today Popular topics Other popular topics in this forum...
10-03-2013, 04:56 PM   #602 (permalink)
Master EcoModder

Join Date: Jan 2008
Location: Sanger,Texas,U.S.A.
Posts: 12,453
Thanks: 20,018
Thanked 6,223 Times in 3,842 Posts
never been there

Quote:
 Originally Posted by Tesla Thanks for that, I still need to play with this equation a bit more. I've been reading a variety of things from Semi-Truck aero through to Belbouth design for engine air intakes, but one thing that struck a chord was rocket nozzle theory. A perfect rocket nozzle will have maximum efficiency when gass departing is at the same pressure as the surrounding atmosphere, if it is higher it is wasted energy, when it is lower pressure it creates drag. From this, in an abstract way I started to look at template theory as an inverted rocket nozzle, the ultimate goal is to leave the air behind the vehicle completely stationary, as if the vehicle had never been there.
That's it in a nutshell.
If you string-line the streamline half body you'll notice that the pathway length of the tail is twice that of the forebody.
Which suggests that the deceleration ramp necessary for attached flow must provide an aerodynamic residence time over the aft-body which is twice the dwell time as that over the nose.
It's the premise for the area rule/sectional density.
__________________

 10-14-2013, 10:20 PM #603 (permalink) Master EcoModder     Join Date: Jul 2011 Location: Ann Arbor, Michigan Posts: 3,807 Thanks: 46 Thanked 2,529 Times in 1,770 Posts __________________ 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
 10-14-2013, 10:25 PM #604 (permalink) Master EcoModder     Join Date: Jul 2011 Location: Ann Arbor, Michigan Posts: 3,807 Thanks: 46 Thanked 2,529 Times in 1,770 Posts Mathematical Modeling of Europa Aerodynamics Mathematical Modeling of Europa Aerodynamics __________________ 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
 10-14-2013, 10:38 PM #605 (permalink) Master EcoModder   Join Date: Oct 2008 Location: Mid-Atlantic Posts: 491 OurInsight - '06 Honda Insight Thanks: 170 Thanked 69 Times in 44 Posts If the "smoke" is coming from the right, are we to believe that the folks doing the test thought the "aerofoil" would be better with the pointed end into the wind?????
 The Following User Says Thank You to jime57 For This Useful Post: aerohead (10-15-2013)
 10-14-2013, 11:07 PM #606 (permalink) (:     Join Date: Jan 2008 Location: up north Posts: 12,755 Blue - '93 Ford Tempo Last 3: 27.29 mpg (US) F150 - '94 Ford F150 XLT 4x4 90 day: 18.5 mpg (US) Sport Coupe - '92 Ford Tempo GL Last 3: 69.62 mpg (US) ShWing! - '82 honda gold wing Interstate 90 day: 33.65 mpg (US) Moon Unit - '98 Mercury Sable LX Wagon 90 day: 21.24 mpg (US) Thanks: 1,582 Thanked 3,541 Times in 2,211 Posts I'm sure they put both models in both ways just to see what would happen. __________________
10-15-2013, 04:00 PM   #607 (permalink)
Master EcoModder

Join Date: Jan 2008
Location: Sanger,Texas,U.S.A.
Posts: 12,453
Thanks: 20,018
Thanked 6,223 Times in 3,842 Posts
Schl'o'rwagen backwards

Quote:
 Originally Posted by kach22i
It may be intentional,but the Schl'o'rwagen model is backwards in the tunnel.
Ooops! I should have scrolled down first.Obviously everyone sees the same thing.
__________________

Last edited by aerohead; 10-15-2013 at 04:13 PM.. Reason: add oops!

 10-15-2013, 04:15 PM #608 (permalink) Master EcoModder     Join Date: Jan 2008 Location: Sanger,Texas,U.S.A. Posts: 12,453 Thanks: 20,018 Thanked 6,223 Times in 3,842 Posts '67 Lotus Europa Did they publish a Cd for the Lotus CFD modeling? The car was originally reported at Cd 0.29. __________________ Photobucket album: http://s1271.photobucket.com/albums/jj622/aerohead2/
10-15-2013, 04:42 PM   #609 (permalink)
Master EcoModder

Join Date: Jul 2011
Location: Ann Arbor, Michigan
Posts: 3,807
Thanks: 46
Thanked 2,529 Times in 1,770 Posts
Quote:
 Originally Posted by aerohead Did they publish a Cd for the Lotus CFD modeling? The car was originally reported at Cd 0.29.
I did not see it at first glance, but it might be buried in there somewhere.

Overlay-image004_zpsd67536fb.jpg Photo by kach22i | Photobucket

One of the more interesting aero-template overlay's I've done to date.
__________________
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

10-26-2013, 04:00 PM   #610 (permalink)
Master EcoModder

Join Date: Jan 2008
Location: Sanger,Texas,U.S.A.
Posts: 12,453
Thanks: 20,018
Thanked 6,223 Times in 3,842 Posts
1967 Lotus

Quote:
 Originally Posted by kach22i I did not see it at first glance, but it might be buried in there somewhere. Overlay-image004_zpsd67536fb.jpg Photo by kach22i | Photobucket One of the more interesting aero-template overlay's I've done to date.
I believe Colin Chapman is responsible for the Europa.There are stories about him being strapped to the outside of a Lotus while it was driven so he could observe the airflow (presumably with a tuft wand) over the cars body.
He's also known for his low mass construction.

__________________