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

[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.

[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).