NCFMF Video: How to Reduce Drag - Fuel Economy, Hypermiling, EcoModding News and Forum

darcane · 03-27-2013, 04:18 PM

I found this very interesting video on another forum, but it is very applicable here so I thought I'd share:

http://www.youtube.com/watch?v=ftq8jTQ8ANE

There is a whole collection of these National Committee for Fluid Mechanics Films (NCFMF) videos. More here: National Committee for Fluid Mechanics Films

kach22i · 03-27-2013, 04:41 PM

An excellent contribution darcane, I feel like I learned something today.

Shortie771 · 03-27-2013, 04:54 PM

Wow, I knew streamlining was important, but I didn't realize how much of an impact the little things can have on drag. When I saw the wire compared to the foil, I couldn't help but think, car antenna. Every little bit can make a big difference.

Thanks for the video. Good find.

RedDevil · 03-27-2013, 06:20 PM

Mental note to self: Wing-shape that antenna stalk

NachtRitter · 03-27-2013, 10:19 PM

cool video; thank you for posting!

RedDevil · 05-22-2013, 06:26 PM

Quote:

Originally Posted by RedDevil

Mental note to self: Wing-shape that antenna stalk

So I just did!

Cut a sheet from some hard plastic bagel box and glued the opposing edges together, nudging the fold into a rounded edge for that more or less wing shape.
Might do something more permanent later.

Too early for A-B-A testing results yet

Honestly, if it would reduce the drag by 1N at highway speeds that would be great, but I'd have to drive for thousands of miles to save just 1 liter of fuel by that. But even at a drop at a time any improvement still is, well, an improvement

...

mf70 · 05-23-2013, 01:04 PM

That was fun to watch & think about.

Three points: 1) the rectangle didn't have the same cross section as the foil and the original rod, so the drag value really can't be compared.
2) the data about round vs airfoil was implicit in the drag value of the rod, even before the wire was tested.
3) I didn't calculate Reynolds number of this test - if I think of it, I'll check with Hoerner to see how close this test data matches.

elhigh · 05-23-2013, 01:58 PM

Quote:

Originally Posted by mf70

That was fun to watch & think about.

1) the rectangle didn't have the same cross section as the foil and the original rod, so the drag value really can't be compared.

No, but it certainly is telling - it had a much reduced frontal area, and yet displayed much greater drag.

An equally telling display, I think, would be to build this same rig and test three shapes: a square, add a rounded nose to the square for a bullet shape, then add a proper tail to the bullet to create an airfoil. That would keep the frontal area constant.

aerohead · 05-24-2013, 05:59 PM

Quote:

Originally Posted by elhigh

No, but it certainly is telling - it had a much reduced frontal area, and yet displayed much greater drag.

An equally telling display, I think, would be to build this same rig and test three shapes: a square, add a rounded nose to the square for a bullet shape, then add a proper tail to the bullet to create an airfoil. That would keep the frontal area constant.

If you can find a copy of Hoerner's 'Aerodynamic Drag' you'll find all those numbers.

freebeard · 05-26-2013, 02:37 AM

I looked at some of the neighboring videos. Here's some interesting stuff:

http://www.youtube.com/user/yshsuzuka/videos
9 videos. Desktop/office-sized (1/7th-1/24th scale) moving belt wind tunnel. "Reynolds number is no problem." Since 1974.

http://wwwDOTyoutubeDOTcom/watch?v=gHFFZ1ru0Pk
Scale models submerged in water. It works about as well as desktop CFD software. Some obvious areas for improvement: The tunnel is too narrow and should be closed on top. Needs immiscible 'smoke' and a steerable nozzle.

I could see a tank divided in thirds with walls/baffles that have four wind/waterwheels, one at each end of both walls. Do you think it would minimize turbulence that way?