Fuel Economy, Hypermiling, EcoModding News and Forum - EcoModder.com - View Single Post - Experiment: tuft testing the underside of a variable-angle tail extension

aerohead · 05-13-2010, 06:05 PM

Robert,I couldn't get the video to play,but I'll try again.
Having not seen the footage,but reading your remarks ( and being well into my ignorance zone ) my guess is that without the side and top flow adjacent to the extended 'bottom',that all this is influencing your results.
From Hucho's book,the diffusers are effective for 2.5-degrees,and 4-degrees,depending on where the up-sweep originates.
The underside of the Insight should dictate how far you can 'cheat',after which you'll just have to live with the difference unless you can make the diffuser to move up and down.
As to the difference in drag,I believe that that will be a function of how much turbulence there is compared to the lack of turbulence with the 'ideal' form of same length.

05-13-2010, 06:05 PM	#3 (permalink)
aerohead Master EcoModder Join Date: Jan 2008 Location: Sanger,Texas,U.S.A. Posts: 15,895 Thanks: 23,972 Thanked 7,223 Times in 4,650 Posts	guessing Robert,I couldn't get the video to play,but I'll try again. Having not seen the footage,but reading your remarks ( and being well into my ignorance zone ) my guess is that without the side and top flow adjacent to the extended 'bottom',that all this is influencing your results. From Hucho's book,the diffusers are effective for 2.5-degrees,and 4-degrees,depending on where the up-sweep originates. The underside of the Insight should dictate how far you can 'cheat',after which you'll just have to live with the difference unless you can make the diffuser to move up and down. As to the difference in drag,I believe that that will be a function of how much turbulence there is compared to the lack of turbulence with the 'ideal' form of same length.