Info custom VSPAERO settings

[Federico Feraiorni]

Hi everyone,

I apologize if this has been addressed before, but I haven't been able to find specific information on it.

I need to analyze a model across a range of Angles of Attack (Alpha from -1 to 25, for a total of 27 values) and multiple Mach numbers (1.70, 2.16, 2.36, and 2.86).

Is there a way to set up a single execution in the solver to run all these parameters automatically and generate a consolidated polar file containing all the results?

Thanks in advance for your help!

[Brandon Litherland]

A Google search of "VSPAERO" would have given you a link to the Ground School tutorials as a start. There are also multiple OpenVSP Workshop slides and recordings describing how to set your sweeps.  There are also other posts in this very forum that ask this same question with provided responses.

I'm not sure how you "haven't been able to find specific information on it" but I'll personally note that we typically expect a bit more effort out of our users, even new ones, before posting to the group.

[Federico Feraiorni]

Hi Brandon,

Thank you for the response. To be honest, I hadn't seen those previous posts; I only reached out after my own initial search didn't yield the specific answers I needed for my setup.

For instance, the Ground School tutorials I reviewed show how to set 'Alpha Start', 'Alpha End', and 'Mach Start/End' with a fixed number of points in the GUI. However, they don't seem to cover how to input specific Mach values (like 1.70, 2.16, 2.36, and 2.86) in a single run, rather than just a uniform range. The fact that this topic has been discussed before only confirms that the solution is not easily found in the standard documentation.

As a new user, it’s not always easy to know which keywords or specific workshop recordings to look for when the standard tutorials don't address a particular need. I believe a quick 'check this specific tutorial' would have been a more collaborative way to help me get on the right track.

Could you suggest any specific keywords to help me find the posts you mentioned?

Thanks for your attention.

[Brandon Litherland]

Hang on.  I think I misunderstood your question.  I was responding to your question about alpha which implies uniform spacing and wrongly assumed that you meant to also sweep Mach uniformly over that range. Is there a reason running single point Mach sweeps won't give you the information that you want?  Typically, I'd recommend only sweeping one parameter at a time to keep the results more meaningful.  If you are pulling the results from the output files, then having the entire sweep of parameters in a single file isn't really going to help you.  I don't recommend using the Results Manager GUI to try and compare data to publications. It's better to recreate the plots yourself.  For whatever reason, if you absolutely must run specific alpha, beta, Mach, etc. rather than a distribution, you'll have to define the list in the *.vspaero input file manually and run VSPAERO from the command line or terminal.  The first line of the VSPAERO echo in the GUI when you execute is the command you would enter. For example, "vspaero.exe -omp 4 filename"

The set of Mach values in the *.vspaero input file from 0 to 3 with 6 points looks like this: Mach = 0, 0.6, 1.2, 1.8, 2.4, 3

From NASA Tech Paper 1316, each Mach case is plotted in isolation. There is no comparison at fixed alpha showing the effects of sweeping a range of Mach number. Why would you need all of the data in a single polar file?

[Federico Feraiorni]

My goal is to compare VSPAERO results directly with experimental data from all the Mach cases. Instead of running the solver separately for each of the four Mach numbers, I am looking for a way to generate a single, consolidated polar file.

Given that the Alpha range remains constant across all cases, having all the results in one place would significantly streamline my post-processing and ensure a more efficient analysis. I would like to avoid redundant manual setups if a batch run or a combined output option is available.

[Brandon Litherland]

The command line also has an option to add points to the run with "vspaero -omp 4 -fs 0.5 1.6 3.3 END END END filename"

This tells the solver to also run Mach 0.5, 1.6, and 3.3 in addition to what's in the input file, no additional alpha, and no additional beta.

This is from the VSPAERO help echo in the command prompt:

Usage: vspaero [options] <FileName>


Options:
 -omp <N>                           Use 'N' processes.
 -stab                              Calculate stability derivatives.

 -pstab                             Calculate unsteady roll  rate stability derivative analysis.
 -qstab                             Calculate unsteady pitch rate stability derivative analysis.
 -rstab                             Calculate unsteady yaw   rate stability derivative analysis.

 -fs <M> END <A> END <B> END        Set/Override freestream Mach, Alpha, and Beta. note: M, A, and B are space delimited lists.
 -save                              Save restart file.
 -restart                           Restart analysis.
 -geom                              Process and write geometry without solving.
 -fem                               Load in FEM deformation file.
 -write2dfem                        Write out 2D FEM load file.
 -groundheight <H>                  Do ground effects analysis with cg set to <H> height above the ground.
 -rotor <RPM>                       Do a rotor analysis, with specified rotor RPM.
 -unsteady                          Run an unsteady analysis, assumes .groups file is setup!



 -interrogate                       Reload an existing solution, and interrogate the data using survey points list.
 -interrogate -unsteady             Reload an existing unsteady solution, and interrogate the data using survey points list.

[Federico Feraiorni]

Brandon, thank you very much for your attention.

For anyone having this exact question, I also suggest to take a look at this demo: https://www.youtube.com/watch?v=5e_crTyH-uM

I was so focused on the GUI settings that i didn't explore the command line capability. Everything is much clearer now.