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

Reply  Post New Thread
 
Submit Tools LinkBack Thread Tools
Old 07-08-2020, 02:06 PM   #71 (permalink)
Master EcoModder
 
aerohead's Avatar
 
Join Date: Jan 2008
Location: Sanger,Texas,U.S.A.
Posts: 11,282
Thanks: 18,142
Thanked 5,996 Times in 3,650 Posts
Rocketail Wing testing

The EPA granted a conditional SmartWay designation to Rocketail based upon 1/8th-scale wind tunnel testing submitted by Rocketail, and on-road fuel economy testing by Messilla Valley Transportation in New Mexico.
The EPA did not conduct nor solicit any 3rd-party, independent evaluations to corroborate results and conclusions.
Messilla claims an improvement from, 9.20971 mpg, to 9.5238 mpg, 3.58-gallons saved per 1,000 miles, a 3.36% improvement.
According to the NHTSA, a 10% drag reduction will net a 4.8% improvement in mpg for a Class-8 tractor trailer.
A 3.36% mpg improvement implies a 7% drag reduction via forward lift and wake modification according to an 'all-star team of industry professionals, engineers, and testing partners.'

__________________
Photobucket album: http://s1271.photobucket.com/albums/jj622/aerohead2/
  Reply With Quote
Alt Today
Popular topics

Other popular topics in this forum...

   
Old 07-10-2020, 01:53 PM   #72 (permalink)
Master EcoModder
 
aerohead's Avatar
 
Join Date: Jan 2008
Location: Sanger,Texas,U.S.A.
Posts: 11,282
Thanks: 18,142
Thanked 5,996 Times in 3,650 Posts
More for Rocketail to explain

I've looked at the wind tunnel testing report by ARC, posted at Rocketail.com.
Some observations.
1) while actual Reynolds number for tractor trailers exceeds 5-million, ARC is limited to 1.1-million.
2) 'wing' performance is very Reynolds number dependent.
3) 'wing' performance is predicated upon free-flight conditions.
3-B) from a simple, turbulent boundary layer thickness calculation, the boundary layer at the rear of the 2016, Wabash, 53-foot trailer is 9.24-inches in depth, up to the 99% inviscid flow at infinity velocity.
4) ARC's baseline Cd for the tractor trailer drifts around a bit at zero-yaw.
5) At supercritical Reynolds number the drag coefficient would be constant up to transonic flow.
6) the testing was conducted with a top-mounted, nearly-full-span ' TOP A ( No Flex) wing mounted to the trailer van.
7) this 'TOP A ( No Flex) wing is never mentioned by Rocketail.
8) although the 'TOP A and side wings clearly add frontal area to that of the trailer van, there is no accounting for it in the drag summary tables.
9) ARC suggests a 2.20% improvement in mpg at 65-mph. A high of 2.7% at 75- mph.
10) Diesel fuel has a thermal expansion coefficient of 0.02093.
11) the average winter-to-summer temperature variability in the USA is 45-degrees F.
12) At a delta-45-degrees, a 100-gallon saddle tank could experience a natural volumetric variation to 'FULL', of 2.093-gallons at the pump, depending upon ambient temperature, above-ground fuel storage/ below-ground storage, fuel turnover rates, and how recently fuel was received from the refinery.
13) If 'volume' is the metric used to gauge mpg, mass equivalency would be required to ascertain actual energy consumed.
14) 22-separate on-road tests of Rocketail open up a virtual Pandora's Box of uncertainties with respect to all quanta.
15) If Messilla Valley truckers aren't disciplined enough to even operate their 'Trailer Tails' one would wonder as to their discipline during the Rocketail investigation.
__________________
Photobucket album: http://s1271.photobucket.com/albums/jj622/aerohead2/
  Reply With Quote
Old 07-15-2020, 12:09 PM   #73 (permalink)
Master EcoModder
 
aerohead's Avatar
 
Join Date: Jan 2008
Location: Sanger,Texas,U.S.A.
Posts: 11,282
Thanks: 18,142
Thanked 5,996 Times in 3,650 Posts
More holes in Rocketail Wing data

Working with ARC's test data, published at Rocketail.com's website, revealed that the added projected frontal area of the 3-wings never made it into the calculations. It appears that ARC simply used the gross frontal area of the Wabash, 53-foot dry van for the 'rig', with no consideration of mirrors, under-airdam clearance, actual wheel exposure, mudflaps, tire gaps, etc., for all the test data, with and without the wings.

__________________
Photobucket album: http://s1271.photobucket.com/albums/jj622/aerohead2/
  Reply With Quote
Reply  Post New Thread


Tags
box truck, vortex generator

Thread Tools




Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2020, vBulletin Solutions Inc.
Content Relevant URLs by vBSEO 3.5.2
All content copyright EcoModder.com