So, if the geometry contains considerable volume underneath the area of interest, you have to take that away. Otherwise, the terrain will be understood as part of the model and will affect the wind behavior in a non-desirable way.
If you wish to include topography, the model must be a single solid volume. Read more about how Ingrd Cloud handles topography here.
Ingrid Cloud supports 11 different file formats. The best file format to use is STL, because there’s virtually no limit for file size. For all the other supported formats, a maximum of 50 megabytes is recommended.