EcoModder Forum Mirror designs, if we can't use cameras yet.

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03-25-2015, 06:04 PM   #81 (permalink)
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drag of open-faced v-section

Quote:
 Originally Posted by aerohead The open-faced strut would behave much like angle iron in the airstream.I don't have that with me,but I believe that the Cd is over 1.00. The jet created would be asymmetrical with respect to the mirrors wake and could possibly make things worse. The mirror in free flight would be Cd 0.30 - 0.25
*All I could find was a sub-critical Reynolds number Cd for an angle iron section,normal to the flow,with no slant.It is given Cd 2.2 by Hoerner.
*Cd 2.0 if a solid section.
*Turned with pointed part into the wind,Cd 1.45.
*Ditto,with solid section,Cd 1.55.
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The only structure shown with sub,and supercritcal Reynolds number was for a circular rod section.
* subcritical = Cd 1.2
*supercritical = Cd 0.35 (only 29.1% of the sub-critical Cd)
There's no telling if any of the other structures would behave the same,but for estimation purposes,it may be all we can do.
*As to the slant,you might just do a simple force diagram and use the Pythagoriun theorem to get velocity vector values angled,and use them with the Cd.

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 03-25-2015, 06:20 PM #82 (permalink) Master EcoModder     Join Date: Aug 2012 Location: northwest of normal Posts: 18,813 Thanks: 5,230 Thanked 6,206 Times in 4,972 Posts
 The Following 2 Users Say Thank You to freebeard For This Useful Post: aerohead (03-25-2015), BamZipPow (03-25-2015)
 03-26-2015, 04:17 PM #83 (permalink) Master EcoModder     Join Date: Jan 2008 Location: Sanger,Texas,U.S.A. Posts: 12,378 Thanks: 19,922 Thanked 6,203 Times in 3,826 Posts 'mirror' / mount shapes/drag here are a few structures which have been wind tunnel tested which might shed some light on mirror bodies __________________ Photobucket album: http://s1271.photobucket.com/albums/jj622/aerohead2/
03-27-2015, 09:53 AM   #84 (permalink)
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Quote:
 Originally Posted by aerohead Here is an interesting CFD and wind tunnel study of 'passive jet' mirrors. Results are a bit quirky,and some off-car testing (which is a no-no) but interesting!http://www6.miami.edu/acfdlab/public...14-01-0584.pdf
These concepts are very similar to the way I think my roof wing with leading air slot works, see (Fig 3).

Very cool.

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