VSPAERO VLM+PANEL ERROR

[Lorenzo Naddei]

Hi, I'm having problems running VSPAERO because when I try to use "thin set" for the wing/tail of my model and "thick set" for the fuselage of my model in the same simulation, the software creates useless data (a bunch of NaN and zeros).

The only way to make it work is by moving the aerodynamic surfaces so out of the fuselage volume that their MAC is outside the fuselage.

Can somebody help me debug this please? Thank you!

[Rob McDonald]

I ran a case as you sent it and then I moved the wings and tail surfaces to intersect the fuselage.  Both were able to work without a lot of trouble.

I did notice that you are running in stability mode.  This will cause 10 runs for each flight condition -- it will perturb all the conditions (7) to find derivatives, including the control surfaces (3).

If you need that, it is fine, but you don't want to turn that on until you have a basic case working first.

When you have trouble, please post a case that is giving you problems and tell us exactly what you're doing so we can replicate exactly what you're attempting.

You're going to want more spanwise resolution on the tail.  You probably also want to select the option to 'Rotate Foils for Dihedral'.  Similarly, for a V-tail, people often use zero dihedral, but rotate the wings about the X axis.  It depends on exactly what you want.

Rob

[Lorenzo Naddei]

Hi, thank you for the response!
I corrected the model following your suggestions and now the simulation runs, I still have some issues with the lateral-directional eigenvalues:
I get a periodical spiral mode and a non-periodical "Dutch Roll" mode.
How can I modify the model to make the spiral mode non-periodical and the Dutch Roll periodical?
Thank you

Lorenzo

[Rob McDonald]

I'm afraid that is a flight dynamics / design question -- not an OpenVSP question.  I.e. go fix your airplane.

as a first cut, the angle on your V-Tail is pretty extreme.  Have you performed any simple sizing calculations for the tail?

Rob

[Lorenzo Naddei]

Plane and eigenvalues fixed, thank you for the help and the tips!!

Lorenzo