Guilin Sun
Ansys Employee

By default, FDTD uses auto non-uniform meshing with geometry/material. So when the material fit changes it needs to remeshing.

One way to improve this is to use fixed mesh size by override mesh. The 3 choices for the background meshing may still change since they only define the maximum mesh size, but you can try to use "uniform".

Using uniform mesh in the whole simulation volume is not optimal.

If necessary, please file a feature request to lock the mesh:

New Feature vote:   Vote new features, and file your feature request