Turbulence - Friend or Foe? |Here's a lot of Aero info, not spread in several threads

[GeneW]

Have to see the actual data but do those delta wing doodads generate vortices or generate laminar flow?

Gene

[DRW]

Originally Posted by GeneW

Have to see the actual data but do those delta wing doodads generate vortices or generate laminar flow?

Gene

Those delta wing doodads are called vortex generators (VG's).

[mji988]

Thanks for the fluids review. Besides vortex generators, will adding heat help trip the boundary layer? If so, do you think exhaust heat could be used to help accomplish this?

[GasSavers_RoadWarrior]

Originally Posted by mji988

Thanks for the fluids review. Besides vortex generators, will adding heat help trip the boundary layer? If so, do you think exhaust heat could be used to help accomplish this?

You can probably use exhaust flow to do it, in a similar manner to "blown flaps".

It's interesting actually how many vehicles now have a large transverse muffler between the bumper and the gas tank, yes the oval shape probably helps fill the hole, stopping the bumper becoming a drag parachute and cleaning up underbody aerodynamics. There is however potentially a small benefit from them expanding air as it passes over it, when hot, and providing a minute amount of thrust.

By exploiting the Coanda effect, exhaust flow could be made to "drive" a Coanda surface at the underside rear of the vehicle. This would have the benefit of helping clean up rear airflow, while also "sucking" the vehicle to the road somewhat, and should also provide around 15lb of thrust at highway speed.

[green swift]

Originally Posted by CO ZX2

Tubulence - Friend or Foe?

Tubulence. Is this effect brought about by sitting down in the bathtub too fast?

When you installed your air dam did you see any increase on the scan gauge?
IF YOU DID HOW much?

green swift

[sonyhome]

I had done a mini survey on VGs in cleanmpg.com,here, which I'll recap and complement:

Vortex Generators - VGs:

Mitsubishi EVO MR $300
Air Tabs $2.50/ea (+10% MPG CR-V gen-1)
AirFlow Systems $10/25ft (I contacted them on FE and they honestly replied)
Vortekz $20/10pc
Fuel Savers AU$110/9pc (up to 11% savings)

Boundary Layer Energizers etc., not quite VGs:

UC Davis BLEs

Sinha Deturbulator tape (This claims up to 30% MPG increase, still in R&D)
Found in Bman83GL Deturbulator tape topic.

Zig-zag and dimple tape(2,3)

Spoilers
Spoilers (not wings) are used to detach the flow of air from the rear of the car to create a pocket of non-turbulent stagnant air behind the car to finish the air flow like a teardrop (makes a virtual boat tail) and reduce Cd caused by drag from poor rear aerodynamics. Used by modern wedge shaped hatchback cars.

(need references) see Citroen Cx or Toyota Prius.

Other stuff

Aerody.org articles
Wolf-Heinrich Hucho - Aerodynamics of Road Vehicles From Fluid Mechanics to Vehicle Engineering
Recumbents.com
Aerohead's post ecomodder
Car Aerodynamics


Diffuser (read for front/rear impact on underbody drag) and ground effect

Wing and Aerofoil

Maxing out tire pressure

Drag Coefficient - Cd/Cx

Wikipedia listing
Daox CdA listing from ecomodder

Not aero

Driving tips (some usefull A/T tips)
Pulse and glide explained with MPG results

Autospeed articles

As for Autospeed aero articles, I had read a few cool ones (VG experiments, wool tuft testing, airflow test):

Vortex:
http://autospeed.drive.com.au/cms/A_3061/article.html
http://autospeed.drive.com.au/A_3060/cms/article.html
http://www.autospeed.com/A_3059/cms/article.html
http://www.autospeed.com/A_3058/cms/article.html

Aero testing:
http://autospeed.drive.com.au/cms/A_108676/article.html
http://autospeed.drive.com.au/A_108675/cms/article.html
http://autospeed.drive.com.au/A_108674/cms/article.html
http://autospeed.drive.com.au/A_108656/cms/article.html

Aerodynamics:
http://autospeed.drive.com.au/cms/A_107773/article.html
http://www.recumbents.com/car_aerodynamics
http://www.edmunds.com/advice/specia...4/article.html
http://www.ibsinger.com/gallery.htm?...&galleryId=768

Under car airflow (Prius +5MPG):
http://autospeed.drive.com.au/cms/A_2456/article.html
http://autospeed.drive.com.au/cms/A_2455/article.html

Undertrays spoilers and bonnet vents
http://autospeed.drive.com.au/cms/A_2162/article.html
http://autospeed.drive.com.au/cms/A_2160/article.html
http://autospeed.drive.com.au/cms/A_2159/article.html

Wiper blade deflector for noise
http://autospeed.drive.com.au/cms/A_2445/article.html

[dosco]

Originally Posted by RoadWarrior

You can probably use exhaust flow to do it, in a similar manner to "blown flaps".

In F1 cars this method was used in the diffuser. Designers found that the change in gas flow due to changes in engine RPM created balance problems. It was eventually scrapped.

In a regular roadgoing car, I'm not sure there would be enough energy left in the flow (after the muffler) to make much of a difference. Get rid of the muffler, then maybe you might have something (in addition to a headache from the noise).

[GasSavers_RoadWarrior]

Yeah, I can see that being a problem, great downforce through a long curve at 10K rpm, but it's time to shift.... annnnnnnnd the back end goes loose.

[GasSavers_RoadWarrior]

Originally Posted by sonyhome

Sinha Deturbulator tape (This claims up to 30% MPG increase, still in R&D)
Found in Bman83GL Deturbulator tape topic.

That's interesting, I mentioned on mpgresearch a while back that it might be possible to use closed cell foam "draft insulating" tape strip to get the same effect. I knew about the effect from a 1970s aeromodeller annual article on use of turbulation strips on model sailplanes. I have 2 points I am going to apply it on Marvin when I get off my butt and get into the aero mods. i) near the back edge of the rear ventilator windows, such that when they are cracked more air will tuck in behind them, and ii) in front of the back light clusters, because modding rear shape there is difficult.

[DRW]

Dam, that's a lot of good info! I'll be reading for weeks.