VLM and surface flows

André

As a hobby, I design and fly model sailplanes, and for design purposes I have developed and implemented my own VLM, based on Katz and Plotkin's methods. However, begin a non specialist of cfd, I have been struggling with a few issues that somebody more familiar with VLM could hopefully help me with.

My problem right now is that the flows on the surface resulting from the calculation are tangential to the surface at the panel's control point, which is OK, but tend to go thru the panel at other points. See for instance

http://www.geocities.com/xflr5/Surf_Flows.gif

The control point is located at 3/4th of the panel's chordwise length.

Would somebody know of this is something wrong with my implementation, or is it a general thing with VLMs ? The rest of the results, lift, drag, streamlines looks OK.

The executable code can be found at http://www.geocities.com/xflr5

If this is the wrong forum to ask this question please advise where it should be posted

Thanks

André