wall function tutorial,doc,v&v missing

[bigfooted]

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This is a reminder for me that there is still no tutorial, documentation and V&V for wall functions.

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1. Add the Stanford diffuser case with wall functions as a tutorial to the website
2. Add a wall function solution to the V&V for the flat plate
3. Update documentation for wall functions

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[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. If this is still a relevant issue please comment on it to restart the discussion. Thank you for your contributions.

[bigfooted]

tutorial for the 90 degree pipe bend is almost finished

[bigfooted]

tutorial for the pipe is finished