Symmetry boundary conditions

Hi dear LAMMPS users,

I’m going to study a system including a poiseuille flow between two parallel walls and in order to reduce the number of simulated particles; I want to simulate just half of the mentioned geometry. To achieve this aim I need to define a symmetry boundary condition on the plane of symmetry. I tried fix wall/reflect to put back my atoms inside the simulated half of my geometry. The problem is that the reflecting wall imposes a momentum to the fluid that repels the fluid particles and reduces the flow velocity. Even using a Langevin thermostat in the directions orthogonal to the flow direction didn’t help me to damp this unwelcome momentum.

Is there any other solution to define a symmetry boundary in LAMMPS?

Thanks for your advisement

You would need to define more precisely what

you mean by a “symmetry” boundary. How is

it different than a reflecting wall?