root gap and lifting line

[charlythewind]

Does anyone has got any idea of how to account for the root (and/or tip) gap when designing a foil using the lifting line?...

thanks

[Karsten]

I assume you have a "vortex" on the lifting line at 1/4 of the chord and one control point at 3/4 of the chord.
To accurately calculate the strength of the vortex if you have a 3D foil you have to use multiple horse shoe shaped lifting lines and multiple control points.

[charlythewind]

Thanks for your answer karsten,
However, i don't see in what you said how to introduce a gap in the lifting line...
could you be a little more precise?...

thanks

[Tim B]

Depending on the precision required, there are three ways...

1) Look in Larsson's book and take an estimate

2) Lots of nasty lifting line theory that won't fully answer the question. So go to a 3D panel method instead (which will answer it)

3) Go to CFD and get the answer for the whole flow field.

And finally, get round the problem by removing the gap (which is, of course, the best answer)

Tim B.

[tspeer]

Originally Posted by charlythewind

Does anyone has got any idea of how to account for the root (and/or tip) gap when designing a foil using the lifting line?...

http://www.tspeer.com/DesignTools/vortex95.xls
http://www.tspeer.com/Planforms/Planar.htm