VSP Aero Runtime Issue

[Patrick Hammer]

Hello,

I have a rectangular wing geometry with a NACA 2412 geometry that I built using the OpenVSP Gui. It is comprised of 15 segments on either side to give me more control over the twist (which is currently set to zero at each section). I'm currently doing Panel Method at AoA = 10deg.

When I set Num U at each segment to 2 (except at the wing-tip where I have refinement), the solution runs fine and the lift distribution is elliptical (see the first image).

When I set Num U to 3 just even in the root section, the centerline lift distribution is very wonky (see second image).

I wanted to increase the span-wise resolution to verify convergence but keep getting this artifact in the central portion no matter what I do (besides making Num U =

 2).

I'd be welcome to hear any suggestions.

Thanks,

Patrick

[Brandon Litherland]

VSPAERO now has the capability to compute loads from panel mode but still has some bugs.  Check the Viewer result to see if it looks even.  Why not use VLM?

[Rob McDonald]

Also, the load distribution for panel mode has some issues with the standard file format.

If you go to the Advanced tab and click 'Experimental File Format' when using panel method, you should get better spanwise load distributions.

The solution is not affected by all this-- all the solutions and total loads are fine.  The difference is in the post-processing integration that results in these load distribution diagrams.

Rob

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[Patrick Hammer]

Rob,

I did notice that it did improve things (how does the experimental format work?). And I didn't see this issue arise when I increased refinement in the other segments, only the root one. And I didn't notice issues with the pressure contours on the surface (jagged areas near the root), so I was quite confused why this occurred.

Patrick

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[Rob McDonald]

Calculating the load distribution plot is a post-processing step -- the solutions (between the two file formats) should be identical (unless the wake was detected differently.

The experimental file format contains not only x,y,z information about each point, but also U,V information about where the point is located on the surface of a component.

The spanwise load integration algorithm uses that U,V information to do the spanwise load stuff.  If it does not have it, it does the best it can with just X,Y,Z.

All that said, load distributions on thick-surface models are a very new feature that was added in the most recent version.  It looks like there are still some improvements to be made - particularly in the version that relies on only X,Y,Z.

Specifically -- I don't know why it influenced your results (with the center line only change), but I'm also not super surprised.

Rob

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