Swirling vortices from vortex generators?

[Patrick]

Originally Posted by cfg83

Patrick -



Do you mean along the side curving up?

Yes. There's also a smaller lip running across the rear top edge of the car.

[cfg83]

Patrick -

Originally Posted by Patrick

Yes. There's also a smaller lip running across the rear top edge of the car.

I am guessing that it is for "tripping" the airflow where it separates from the car. If that's the reason, other aero-people can explain it better than me.

CarloSW2

[aerohead]

Originally Posted by AeroModder

I see. So the "Kammbacks" used in mass-produced vehicles today fall short of the ideal angle. I was thinking more along the lines of what is out there than the idealized version. My mistake.

I suspect that automakers would prefer we look at 'styling',not engineering.They may get to engineering one day.Don't know.
The most current example of a perfect Kamm-back is the 2008 Mercedes-Benz Boxfish concept.With only 32% aft-body they achieve Cd 0.19.
By comparison,The 2nd-gen VW 1-Liter car,with more aggressive ( steeper ) roof-line and diffuser,can't even get to Cd 0.19,and that's with 45% aft-body.
The air really likes the Kamm-back and occasionally the wind tunnels get a nice example for which to remind us.

[aerohead]

Originally Posted by Patrick

Why does the Mk IV have the spoiler on the rear edge (it seems rather large on the sides)?

Patrick,the 1965 car had no rear spoiler at all.My guess would be that they modified the car to race at shorter tracks,where overall speed would be reduced.By adding the spoiler they could get the cornering downforce they needed at the lower velocity.
You will see examples of this with Porsche and other marques.GM's Oldsmobile AEROTECH ran a short-tail and a long-tail car,depending on the track.

[cfg83]

Hello -

I overlayed the tear-drop and it looks pretty darn good :



CarloSW2

[Patrick]

Originally Posted by cfg83

Hello -

I overlayed the tear-drop and it looks pretty darn good :



CarloSW2

Now it looks like a Rolex Series car.

[aerohead]

Originally Posted by cfg83

Hello -

I overlayed the tear-drop and it looks pretty darn good :



CarloSW2

Carlo,I found a number of 'matches' for the Template.Some were 'dead on',others close:
1922 Jaray 'pumpkin seed' wind tunnel model
1933 Walter E.Lay 'pumpkin seed' wind tunnel model
1935 Kamm 'pumpkin seed' wind tunnel model
1957 MG EX 181 streamliner with reflex camber tail
1957 Grumman TF-1/C-1A TRACER/E-1B 'Willy Fudd' radome
1961 Mickey Thompson' 'Pumpkin Seed' streamliner
1963 Alfa Romeo TZ
1964 Ford GT 40
1967 Ferrari 330 P4
1967 Chevy Chaparral 2F
1970 Porsche 917 Lange-Heck( Long-tail )
1978 Daimler-Benz C 111 III full-tail with reflex camber Cd 0.178
1981 Volkswagen Blunt Body Cd 0.15
1981 VW Drop Shape Cd 0.16
1981 VW Flow Body Cd 0.15
1987 GM/AeroVironment Sunraycer Cd 0.089-0.12
1988 Lotus Esprit Turbo
1991 Ferrari F-40
1994 Saleen Mustang S-351
1994 Bugatti EB 110
1995 Ferrari F355 Berlinetta
1999 GM PNGV Precept Cd 0.163
2000 Honda Insight Cd 0.25
2006 AeroCivic Cd 0.17
2008 Daimer-Benz Boxfish concept Cd 0.19
2009 Toyota Prius Cd 0.26
2009 VW 2nd-gen 1-liter concept Cd 0.195
2009 Bugatti Galibier
2010 Porsche Panamera

It looks like,that when 'real' performance matters,the design team will lean towards the 'ideal' aerodynamic parameters.Curious!