Hello
You will find a complete description of parallel command in the guide for programming and in the book of Jean Michel Hervouet.
Moreover, the largest case, as far as I know, if the Malpasset test case with 200M of nodes performed with the Daresbury clusters (See paper of
Moulinec et al.)
If you want to read more about the parallelisation of Telemac-3d, you can also read
this
I hope that this helps
Riadh ATA