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Graph
Thanks again Tauno.
The log graph should straighten out a curve if it goes assymptotic. Its starting to look straight even without the log effect. Im sure as we find out what is actually optimal, that it will make more sense. Its a start. |
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Can you please illustrate the last step of this calculation ? ie how to go from 4 pi [ Cdp / CL + CL / (pi AR) ] = 4 pi CD/CL ? if we multiply right side from CL then we will have to multiply left side as well isnt it ? Also: I saw a different form of calculation from Joe Wurts in this website http://douglasturner.tripod.com/id27.htm Seems like he has used polar coordinates to derive his equation but I dont understand how he got e^ there Can someone shed some light one this ? Thanks so much. |
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Found the answer for my second question; on Joe Wurts derivation.
http://douglasturner.tripod.com/id27.htm |
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Last edited by Buwa; Apr 12, 2018 at 06:18 AM.
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Not an Aero guy, but doesn't AR stand for aspect ratio? For high aspect ratio wings, the CL/(pi AR) will be very small, compared to the other term in the square brackets. (E.g. if CL is about 2, and your aspect ratio is about 15, then that term is about 0.042.
-David |
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You are not alone and me neither. Just trying to work out the math behind this just to understand it better and out of curiosity. If we just consider the circling flight, its obvious that the kinetic energy loss is equal to the work done by the drag. So for a given radius maximizing L/D makes perfect sence. Only problem is I dont see how 4 pi [ Cdp / CL + CL / (pi AR) ] = 4 pi CD/CL |
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I don't know what the difference between Cdp and CD is, but again, for a wing with large aspect ratio AR, the second term in the square brackets is very small. So, 4 pi [ Cdp / CL + 0-ish].
-David |
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Hi Buwa,
Induced drag coeff (Cdi) = CL^2/pi*AR so the second term in the brackets can be rewritten as Cdi/CL. Also CD = Cdp +Cdi, so everything in the brackets boils down to CD/CL |
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Can't be much flying Joe, it's all gone to theory reports rather than flying reports lol
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Latest blog entry: JW48 - Lightweight DS Build
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