Core Dumped Error

Running a simulation, the attached error issued once in a while. I just resume the simulation and it happens in another simulation time. What is it about???

A NaN (“Not a Number” ) means there is a singularity in the calculation. It could be a bad setup, a bad mesh, or a bug. It is impossible to tell without more details. First verify your mesh. Feel free to post your input file(s) so someone has a chance to take a look.