VSP_aero Supersonic Secondary Development

[Limo]

Howdy! I'm about to use VSP_aero to conduct aerodynamic analysis and calculations for aircraft. However, there is something I want to figure out. Hope you nice guys can help me on that.

My confusion is:

1. It seems that the latest version of OpenVSP  can calculate supersonic conditions for aircraft, but if  I want to check its calculation formulas, where should I go for check?

2. If I want to modify the calculation formulas, where should I go and how should I modify them?

(I'm wondering if there is any manual that introduce  the overall computing architecture.)

By the way, I'm a freshman in this group, your answer and advice would be a huge help on my learning progress. 

Thanks again! 

[Brandon Litherland]

VSPAERO has been able to solve supersonic flow for thin surface or vortex lattice modes for many years. That's not a new development. Dr. Kinney has been developing the supersonic thick/panel mode for a while, however.

Just from a quick look at the OpenVSP code on GitHub, you might start in VSP_Solver.C about here: https://github.com/OpenVSP/OpenVSP/blob/e9775712fd542fe9f4b5163595a8999eab407d93/src/vsp_aero/Solver/VSP_Solver.C#L1859

There isn't any documentation of how all this ties together so I strongly recommend running a Doxygen map of the VSPAERO code. You will do this in the OpenVSP Git Clone / src / vsp_aero / Documentation directory.  Of course, if you modify any of this, you'll have to rebuild VSPAERO on your own.  

What are you trying to accomplish that would require changing VSPAERO's solver code?

[Limo]

I sincerely thank you for your response, Brandon.  

I'm trying to iterate and optimize the aerodynamic shape of an aircraft. At the same time, I need to write a report which can clearly explain the logic of supersonic aerodynamic calculations in VSPAERO. If the calculation formula meets our needs, then I don't need to make any changes. That's why I  care so much about the formulas and logic of VSPAERO for aerodynamic calculations of aircraft under supersonic conditions. 

I have run a Doxygen map of the VSPAERO code as you suggested. It would be a great help. However, the specific content still need time to read.

Thanks again for your help!

[Brandon Litherland]

The only other source of theory documentation for VSPAERO is the OpenVSP Workshop Slides by Dave Kinney.

2020: https://youtu.be/-zQEmmrb6ck

2023: https://openvsp.org/wiki/lib/exe/fetch.php?media=workshop23:2023_workshop_-_theory.pdf

2025: https://openvsp.org/wiki/lib/exe/fetch.php?media=workshop25:2025_openvsp_workshop_vspaero.pdf and https://openvsp.org/wiki/lib/exe/fetch.php?tok=2fd127&media=https%3A%2F%2Fyoutu.be%2FCBj5KL-YpaM

[Rob McDonald]

Brandon is correct, the OpenVSP Workshop slides are the only source of theory documentation for VSPAERO.  The treatment in that format is pretty top-level, many of the details are omitted.

I have seen many efforts by students to write about VSPAERO.  Most of those efforts include a theory section.  Since there is no official theory document for VSPAERO, the students end up using information from standard textbooks.

Unfortunately, those writeups end up way off track.  Personally, I feel that those writeups are a waste of effort.  I understand why you think you need to write up the theory of VSPAERO -- and I understand why your advisor may direct you to do so.  However, it isn't something that can be done in a quality manner with the information available.

Someday Dave will write an authoritative theory paper for VSPAERO.  After that time, students will be able to plagiarize an accurate description of the theory and methods of the code.  Until then, they will continue to make up a fantasy theory document.

Whatever the case, when you find one of these documents out there (that claims to be a writeup of the VSPAERO theory -- that is not written by Dave Kinney) -- know that it is wrong and you shouldn't believe anything it says.

Rob

[Limo]

Thank you Rob and Brandon, you guys are really nice! I have read the materials that Brandon provided. At the same time, I also carefully read your answer, Rob.

For now, my confusion is:

When conducting aerodynamic calculations for supersonic aircraft in VSP_aero, which method should actually be used? VLM or Panel Method? Thin set or Thick set? Does supersonic calculation take the effect of the Mach cone into account?

As Brandon said, Dr. Kinney has been developing the supersonic thick/panel mode for a while. Is that means I can use thick/panel to calculate supersonic conditions?

Your help prevented me from taking the wrong path. Thanks again for your early reply. 

[Rob McDonald]

To use supersonic at this time, all components must be in the Thin set.

Only very early work has been done on thick surface supersonics.  Some time ago, the developer had an idea about how to make it work.  He spent a short time doing some very crude experiments.  Those showed promise, but were not appropriate for production use or release.  Since that time, a lot of development has occurred without the thick supersonics work.  So, if that work is ever prioritized, the same kinds of ideas would need to be re-implemented and made production ready in the updated code.  That work is not on the current roadmap, so we have no idea if or when it will happen.

Rob