WindowsError during SnappyHexMesh


Hi mostaphaRoudsari, thanks for your help, I successfully installed the latest Butterfly, but I meet a problem when I run the indoor airflow 2d file

Do you know how to solve this problem?
PS: the indoor airflow file and outdoor airflow file can successfully operate on my computer

Butterfly installation problem

@hc2011301539 Are you running rhino grasshopper in administrator mode?


yep, in administrator mode


WindowsError most of the time happens when you can’t delete a file because it is in still in use. Can you share the full error report? Also trying to run the study in a new folder should solve this problem.


hi @hc2011301539

Try to turn on the snap to true in the snappyHexMeshdict component.

Let us know



I got the same issue. The error file is Also I tried snap to True in snappyHexMeshDict, but no luck.



hi @hc2011301539

I think its a meshing issue and you’ll need more cells in your domain.

You could do so by reducing the cellsize or increasing by 1 or 2 the refinement level of your geometry.

Have a go and let us know


Hi Olivier,

Thanks for helping but it seems not about meshing. It is the snappyHexMesh component. The error message I got is:

Updating global refinement level to (3, 3).
saving the new snappyHexMeshDict.
Runtime error (Win32Exception): WindowsError
line 444, in is_polyMesh_snappyHexMesh, “C:\Users\test\AppData\Roaming\McNeel\Rhinoceros\5.0\scripts\butterfly\”
line 117, in script

Seems that is snappyHexMeshDict cannot be access.




could you share your definition?


Thanks for your reply, but it’s still not working (428.9 KB)


Hi mostaphaRoudsari, I meet a new problem in indoor ventilation analysis, I want to test the ventilation effect of my ventilation blocks, but the results are weird, even after I delete these extra ventilation blocks, the result is still wrong.

wind (827.4 KB) This is the GH file
by the way, sometimes when I run the CFD simulation in butterfly, the values of wind velocity and pressure will appear some very large numbers


For new questions you should open a new topic! You can reference this post in your question if that will be helpful. Thanks.


Sure. Here it is. (425.8 KB)

However, there is no changes at all from the example file.



Just an update of this case. Olivier help to solve the issue but responded on another post.

It seems that the mesh is the main issue. For this case, the _cell_count in BlockMesh was set as {0.2, 0.2, 0.2} in the example file, which is the main cause of the error. After changing it to {70, 1, 60}, the case runs well.

Thanks for helping Olivier.