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-   -   Induded Drag using Fluent (http://www.cfd-online.com/Forums/fluent/42689-induded-drag-using-fluent.html)

Tim Lammering October 29, 2006 15:18

Induded Drag using Fluent
 
Hi,

can anybody tell me the easiest way, to calculate the induduced drag from a inviscid solution of a subsonic flow over a simple wing.

Thanks, Tim

Vincent October 30, 2006 03:15

Re: Induded Drag using Fluent
 
It's not possible in Fluent to distinguish between induced drag, parasite drag etc. Fluent can only calculate the contribution of the shear stresses and the pressure forces.

Tim Lammering October 30, 2006 03:46

Re: Induded Drag using Fluent
 
Hi Vincent,

thanks, that what I though.

Nevertheless, when calculating the forces in inviscid flow on the wing, fluent should give me a drag coefficient thats includes drag due to pressure forces and the induced drag. Is that correct?

One possibility that I though of would be to calculate the spanwise circulation distribution. Does anyone has experience with that?

Thanks, Tim

Vincent October 30, 2006 09:24

Re: Induded Drag using Fluent
 
The drag coefficient calculated by Fluent in inviscid flow is due to pressure forces. Induced drag is part of that. Note that you cannot split drag into pressure drag and induced drag! You can split into either induced drag and parasite drag, or in pressure (normal forces) drag and friction (tangential forces) drag.

Calculating the spanwise distribution of lift or circulation is pretty difficult in fluent. One way to do this is by dividing the wing in several parts and calculate the lift on each part.

Charles October 30, 2006 12:11

Re: Induded Drag using Fluent
 
As long as the wing is simple, a good approach is to get the pressure drag at your angle of attack of interest, and subtract from that the pressure drag at zero lift. The remainder is the induced drag, and is pretty accurate, provided that there is no stall or separation. This is trivial to do with a symmetric wing, but once you have a fuselage and cambered wing it is not so easy any more. Also, for subsonic flow, don't try to do it with an inviscid calculation.


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