Replicating Karoo's non-planar geometry paper

[Edward Pickens]

I am trying to replicate Karoo's results wing on nonplanar wing geometry.  I have not began optimizing the wing yet, but I have noticed an odd result.  The lift goes to zero at the center of the wing as if there was a fuselage in the center causing the reduction in lift.  This is not the case as can be seen below.

What is causing this?  Is this a result of how i ran VSPaeroor or  designed the boxwing?

How can I fix this?

I have stepped away from OpenVSP for some year and am new to 3.50.  This project has a few goals, one is to get me back into it.  Any help woul be much appreciated.

[Rob McDonald]

OpenVSP is detecting the wake as a single wake line -- which should be good.  I'll have to look into how VSPAERO handles this downstream.

You can see from the prepared geometry (after clicking Prepare Solver, or after Launching) that the highlighted trailing edge wake is a single color (Red).

If you perturb the top wing up slightly (creating a tiny gap at the wingtips), you will instead see separate wakes created (two colors).  In this case, there is no dip at the centerline -- but it will mean a dip in circulation at the tips.  Since they are vertical, you should see it in sideforce distribution, not lift distribution.

If that works for you, try that.  Otherwise, I'll see if I can figure something out.

Rob

[Edward Pickens]

I am not certain if I will be able to replicate the results from the paper with that dip.  I am new to this version and have not been successful getting panel method, or thick, to run yet.  Will the dip still appear?  Thank you  -Ed

[Zach Hazen]

I was interested b/c I've attempted to do closed wings in VSP as well.  Kroo's publication makes a good validation.  I wonder if it has something to do with the wake indexing behavior I've noticed before.  This is in fixed-wake mode.  Maybe some indexing error going on?  Draw colored wakes -> wingID makes the end-to-start wake line go away graphically in the viewer.  

[Zach Hazen]

X-Z Symmetry seems to clear up the circulation discrepancy at the root.  The trailing vortex still shows up as connected from the 2nd to last wake element of the Bottom Wing to the 1st wake element of the top wing.  The shared element - the top wing and bottom wing, is not shedding a trailing vortex.  

Hope that helps shine a light on what might be going on?

[Edward Pickens]

I was able to run the data with Thick panel mode.  It crashed a few times but I got there.  The results are basically the same as you can see below.  I don't know if I can perform the analysis without solving the dip issue.  My gut feeling is that the dip or separating the wings vertically to remove the dip will change my results enough to invalidate them.  

Instead of a closed wing maybe I use the Moulthrop theory and separate the top and bottom wings not by a vertical gap but a horizontal one.  I think that may be closest to my desired results if the dip cant be solved.  Thoughts?  -Ed

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[Edward Pickens]

How did you run this?  The file was constructed with symmetry turned on but it runs the entire aircraft.  I was looking to run half the aircraft reflected about the axis, but was unable to find that function.  Thank you for helping me through this.  -Ed 

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[Zach Hazen]

I turned X-Z symmetry on in the VSPAERO menu.  I deleted the slice at Y = 0 (not sure if this matters).

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