When using the Intel message passing interface (MPI) on Windows (which is the default when using less than 64 logical cores) with shared memory on a local machine, the ability to dynamically spawn additional processes when switching from meshing mode to solution mode is supported as a beta feature if you have launched Fluent from the command line, as long as you provide a host file through the -cnf=<x> option that contains just the local machine's host name (for example, fluent 3d -meshing -tm3 -t5 -cnf=hosts.txt). Note that this will degrade performance.

This partially resolves an issue that was noted in the Ansys, Inc. Known Issues and Limitations for Release 2020 R2 (236195 / 257722). Note that dynamic spawning is not possible using Fluent Launcher or the /parallel/spawn-solver-process text command in meshing mode.