Can't apply loads on Aero Structural Coupled Analysis tool

[Andrea Spinelli]

Hello.

I've been playing around with the new functionality for Aero Structural analysis.

However, the application seems unable to generate the loads on the .inp file for calculix.

I've ran both VSPAERO with and without cp_slicer, Write 2D FEM flag and both VLM/Panel.

But when I press the Apply Loads, the generated inp files only have this as load cases:

**Analysis
*STEP
*STATIC,DIRECT

*DLOAD

*NODE FILE
U
*EL FILE,OUTPUT=3D
S
*NODE PRINT, NSET=NALL
U,RF
*END STEP

Could you please explain where the program is extracting the loads?

Do I have to use any specific settings in VSPAERO? Is there any naming convention to be respected? Are loads extracted from CP_slices? 

I have to say I was able to get the loads applied once, when the geometry file was created new. So I am not sure if this is a bug of openvsp or a problem from a setting.

Thank you very much for your help.
Kind regards,

Andrea

[Andrea Spinelli]

Dear All,

I actually looked into the source code and identified the source of the issue.

Loads are applied using the vsploads.exe tool. The Aerostructural module in OpenVSP just generates the command line required to run it: vsploads.exe -interp [name of calculix .inp file] [name of vspaero .adb file] -dynp [dynamic pressure value]

The vsploads tool looks into the calculix input file for a set of elements labeled as "ESkin", on which the aerodynamic loads shall be applied. This is the default name of the Skin structural element in the FEM window of OpenVSP.

In other words, do not change the default name for the skin in FEA Structure window.

Rob you may be interested in this as future troubleshooting reference or when you will create a tutorial for the Aerostructural tool.

Kind regards,
Andrea

[Andrea Spinelli]

*edit: the generated command line is vsploads.exe -interp [name of vspaero .adb file]  [name of calculix .inp file] -dynp [dynamic pressure value]

[Cean]

Do you have a demo model file? Thanks.

[skyc...@gmail.com]

I've run into similar issues and agree, anything not labeled Skin does not get pressures applied (You can see this in my 2023 workshop presentation on structures).  For example, if you create rectangles to represented cored regions on the structure, those rectangles will not get pressure applied.  As it's not very easy to rename everything skin, this is something that we hopefully will fix here in future work on this tool.

Thanks,

Bryan

[Gustavo Jorge Resende]

Hey guys,

Thanks for the insights on this matter, I was running into similar problems.

However, after applying the Loads, the 'Solver Structure' continues to be gray out...

Do I need to have CalculiX installed to continue? (not sure if its a dumb question, but I assumed that it would some how be embedded in the .exe files).

Thanks,

Gustavo J.

[cean wang]

Yes. you need CalculiX's ccx file to solve the genearated case.

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发件人: ope...@googlegroups.com <ope...@googlegroups.com> 代表 Gustavo Jorge Resende <gustavo...@gmail.com>
发送时间: 2023年11月2日 7:29
收件人: OpenVSP <ope...@googlegroups.com>
主题: Re: [OpenVSP] Re: Can't apply loads on Aero Structural Coupled Analysis tool

 

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[skyc...@gmail.com]

And it needs to be in your PATH if you're on Windows.  Same with cgx I think?

[cean wang]

Yes, cgx for visualize.

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发件人: ope...@googlegroups.com <ope...@googlegroups.com> 代表 skyc...@gmail.com <skyc...@gmail.com>
发送时间: 2023年11月3日 10:23

To view this discussion on the web visit https://groups.google.com/d/msgid/openvsp/d1b29e8e-3f5e-41c0-a17b-abefee6a4380n%40googlegroups.com.

[Peter Hauschild]

This might be a dumb question but i have the same problem. By "be in your path" you mean Calculix and OpenVSP had to be installed in the same folder?

[Andrea Spinelli]

In my case I had ccx.exe and cgx.exe with their .dll files in the same folder as vsp.exe 
But if you don't want that, you have to have these two files inside the windows environment variable PATH. This environment variable allows you to run any program in the cmd or powershell without referring to its destination.

Also apologies to Cean, but I don't have the files I used to work this out... I mainly went through the code to find the answer.

Hope this clarifies.

Andrea

[Andrea Spinelli]

Dear Bryan,

Do you perhaps know how to use vspviewer.exe for visualising calculix input and result files?

Trying to load the .frd/.inp file either via the Aerostructural menu or from the command line doesn't work.

Kind regards,

Andrea

[cean wang]

I am using Windows 10. 

Why I get this error when try to click on 'Solve structure':

ccx D:\openvsp\vsp3Model\A330\A330_main_wing_Struct0_calculix.static
 *ERROR in openfile: could not open file D:\openvsp\vsp3Model\A330\A330_main_wing_Struct0_calculix.static.dat

The generated case file is A330_main_wing_Struct0_calculix.static.inp. But it asks for a dat file. 

I have tried to make a dat file which is a copy of that inp file.  But still get this error. 

No problem to run ccx in a DOS terminal to solve this generated case file.

 

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发件人: ope...@googlegroups.com <ope...@googlegroups.com> 代表 Andrea Spinelli <cranfi...@gmail.com>
发送时间: 2023年11月3日 21:51
收件人: OpenVSP <ope...@googlegroups.com>
主题: Re: [OpenVSP] Re: Can't apply loads on Aero Structural Coupled Analysis tool

 

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[cean wang]

After applying load and getting the case file, I open a DOS terminal and solve it there. 
vspviewer.exe only support triangle element.