pictsidhe
Well-Known Member
I was doing my mindless factory job last night, It leaves about 99% of my brain capacity spare. I was pondering drag reduction and hit upon the idea of hot surfaces to decrease boundary layer density and therefore drag. A breaktime google turned up an interesting paper:
http://www.rollinghillsresearch.com/Aero_Research/Files/AIAA-1999-0134_BLHeat.pdf
While they used electric heating, that is probably of dubious overall benefit. Piston planes do have an abundance of waste heat that can be used. only about 30% of fuel energy spins the prop, the rest is dumped into cooling air and hot exhaust. Considering the above paper, it would seem a good idea to dump said hot air and gas over as much surface as possible. Broad, skinny vents would be preferable to narrow ones by blanketing more surface in warm air. The ultimate would be heating the skin as they did, but that's getting awkward with coolant or exhaust pipes running through the wing skins.
I suspect that at higher Reynolds numbers, a larger proportion of surface needs heating in order to get good drag reductions. Low Re parts are just crying out to be heated, though. The tin can enthusiasts will have a much easier time integrating this idea.
http://www.rollinghillsresearch.com/Aero_Research/Files/AIAA-1999-0134_BLHeat.pdf
While they used electric heating, that is probably of dubious overall benefit. Piston planes do have an abundance of waste heat that can be used. only about 30% of fuel energy spins the prop, the rest is dumped into cooling air and hot exhaust. Considering the above paper, it would seem a good idea to dump said hot air and gas over as much surface as possible. Broad, skinny vents would be preferable to narrow ones by blanketing more surface in warm air. The ultimate would be heating the skin as they did, but that's getting awkward with coolant or exhaust pipes running through the wing skins.
I suspect that at higher Reynolds numbers, a larger proportion of surface needs heating in order to get good drag reductions. Low Re parts are just crying out to be heated, though. The tin can enthusiasts will have a much easier time integrating this idea.
