Cruise performance / trim analysis

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Olivia Stodieck

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Mar 14, 2023, 12:43:38 PM3/14/23
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Dear all, 

I recently picked-up OpenVSP and am really enjoying it - thank you for the great online tutorials!

I just wanted to share a few notes and python code snippets about doing a cruise performance analysis with VSPAERO, since I recently went through the exercise.

In the study, I cycle through a range of velocities and calculate the trim AoA and HTP angles for the simple Cessna 210 model from the example files (note - I swapped to SI units, as I am more familiar with those). I use the python API to update the model and run the VSPAERO analysis. 

I also use OpenMDAO to automate the convergence of the trim variables and the cycling through the different cruise conditions (and changes of wing aspect ratio). 

All the details and files are summarised in this dapta tutorial (disclaimer: I am the main developer) : https://daptadocs.com/Tutorials/Using%20OpenVSP%20for%20aircraft%20performance%20analysis.html 
I am using the dapta app in the tutorial to run the coupled code components in the cloud, but it can be run locally too with a few python edits.

Note: I  do seem to get very high L/D values for a Cessna (~20) - I think I might have forgotten to set the Reynolds number...  

Of course, if there is a better way to do this - please let me know! 

Regards, 
Olivia

Rob McDonald

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Mar 14, 2023, 3:43:43 PM3/14/23
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Thanks for sharing that, I will have to check out this tool and your platform.

I wouldn't be too shocked that your L/D is high -- you are only modeling the wing and tail.  So you're getting all the lift -- while leaving out the drag of the fuselage, landing gear, antenna, and all excrescences.

Rob


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