Wakes from the wing tip cap

[Tobias Sugandi]

Hi everyone,

Would it be possible to also shed wakes from wing tip cap? maybe if the cap type is edge or sharp? 

If I need to modify the source code, would you mind giving me some hints or pointing me to the right direction? I would really appreciate the help.

 

Thank you very much in advance!

Tobias

[Rob McDonald]

Are you using thin-surface, VLM, or thick-surface Panel mode?

There are four scenarios...

1) VLM uses the DegenGeom file format to transfer the geometry to VSPAERO.  VSPAERO uses the structure of the file to determine where the wake is attached.  I would say no, there is no reasonable way to accomplish this.

2) If you change VLM to use the 'Alternate File Format', then it will use the *.vspgeom file format to transfer geometry to VSPAERO.  The *.vspgeom file format includes a list of nodes that comprise the edges to attach wakes to at the bottom of the file.

3) Panel now uses the *.vspgeom file format by default, with the same kind of trailing edge node list.

4) If you change Panel to use the 'Alternate File Format', then it uses a *.tri file to transfer geometry to VSPAERO.  In that situation, VSPAERO searches for aft-facing sharp edges to define as trailing edges.

1) Is the hardest to make your change.  It is also being phased out, so this approach might not work in six months.

4) Requires modifying VSPAERO source code to define / change the rules for identifying TE edges.  What calculation would you do to identify your new edges?  How would you know?  This mode is also being phased out, so while it is easier than 1), it has the same long-term support problem.

2, 3) are the file format that will be long-term supported.  Right now, the edge wake list is identified by OpenVSP because we 'know' the topology of the geometry and where the wing TE's are.  However, we also 'know' where the wing tips are, or could apply other criteria.  So, things could be changed.

However, you could also write a stand-alone code to modify the *.vspgeom file to add your desired wake edges.  You could then run the VSPAERO solver from the command line.  This would give you the best opportunity to test the effect of changing the wake attach lines without investing a lot of time in the code.  If your results are strongly positive and of general interest, I might be able to help make the changes to OpenVSP -- or if you still want to do it on your own, then it may be more worth you investing the time in the change.

In the OpenVSP *.zip file, there is a file -- matlab/readvspgeom.m  That will read and visualize a *.vspgeom file.  readvspgeom('airplane.vspgeom',true);  If you don't use Matlab, it should be easy to replicate Python or anything else.  You could probably use the 'text' command to label every node, then go in and manually write down the nodes (in order) you need to extend your wakes.  Save the file, re-visualize it to confirm the desired result, etc.

Hope this helps,

Rob

[Tobias Sugandi]

Hi Rob,

Thank you very much for the kind explanation. I really appreciate it!

I will try your suggestion to modify the *.vspgeom file and will let you know if it yields positive result.

Best regards,

Tobias