keep the density of the gas constant in a certain area bylammps

Dear all
In lammps, I want to keep the density of the gas in a certain area constant. Which command will do this?

It would be appreciated if you could provide any suggestions. Thanks

With Regards !

zhang

Dear all
In lammps, I want to keep the density of the gas in a certain area constant. Which command will do this?

one possible way is to set up a confinement (which means, that this gas cannot diffuse away) through suitably chosen wall fixes.

axel.