Creating obstructions and complex geometry for indoor Butterfly scenes

[Mathiassn]

Give the inner walls some thickness. Ideally around 6-9 cells around the edge of wall (the thickness). Or isolate to the one room in focus.
Make the stair like a ramp or make sure to have 6-9 cells in each step.

In general never model details smaller than 3 cells or you may have meshing issues. (And smaller than 15 cells may not show correct results)

Try running checkMesh and see if it passes the check. Never run a simulation on a failed mesh as it can cause explosions (unless you use some work arounds) Never. Instead export the skewed faces to vtk file and visualize bad areas in Paraview, fix them (by removing the detail or refining cells) and try again. A good mesh is an iterative process.

Also take a look at the answers here

Snappyhex mesh not running properly

Yes if the gap is so small you don’t need the wind to move though it, then align the buildings to remove it. Same goes for setbacks in facades etc. Rule of thumb meshing rules (I’m open for alternatives!) My general rule of thumb is that a setback needs at least 2-3 cells in order to “work” meshwise and 5-10 in order to be reliable simulationwise. For corridors etc at least 10-20 cells for it to be sort of reliable. At 3-5 cells it can “run” but it will slow the wind and your results look too…