Help needed with Unsteady analysis: store dropped

[Jaime García]

Good morning,

First of all, thanks again for this great software.

We are trying to simulate a store drop with the geometry of the paper AEDC-TSR-91-P4 ""CFD Wing/Pylon/Finned Store Mutual Interference. Wind Tunnel Experiment" and compare OpenVSP results to the ones shown in the paper "A Validation of FlightStream for Store-Separation Modeling".

We thought it was possible because we have seen the following video from the 2021 Workshop:
https://youtu.be/5e_crTyH-uM?si=S7yFtkQQBhYLqLZ5

As there was not to much information on how to do it, we checked the threads of this group and found the following, of arround the same time of the workshop, that has a little more information:

https://groups.google.com/g/openvsp/c/3iE6Dk69P4o/m/bwGyJk_NAQAJ

We have manage to get the unsteady analysis working through the command line in OpenVSP 3.49.0 in a windows platform. You can find the .vsp3, .vspgeom, .groups and -vspaero files attached. This files were created following the information mentioned above.

As it was anticipated in the other conversation of the google group, it doesn't seem possible to access the store cg displacement and velocity data, that is probably stored in the .adb file. Nonetheless, looking at the calculation steps, as it can be seen in the left side view video also attached, the store doesn't seem to move afterward, it moves only down, and also it does not change its rotation in time. This was a little surprising for us, as in the reference video it seems to rotate.

We think something is not properly set-up but we haven't been able to find more information so we can correct it. We have try to set a velocity in the fixed component but that does not change anything. Changing the speed of the store group (a positive velocity), moves the store afterwards but at a constant rate, not taking into account drag or changes of drag with speed.

Any help to make the analysis more realistic is really welcome.

Kind regards,

Jaime