adiabatic wall

Dear Lammps users,

I am trying to simulate a liquid flow between two parallel fixed walls. The walls are fixed by “fix setforce 0.0 0.0 0.0” and “velocity set 0.0 0.0 0.0”. I was wondering when the walls are fixed, can I consider them as adiabatic walls or they are heat sinks with the constant temperature of zero?

Thank you in advance for your help.

Best,
Santiago

Collide a particle with your wall of particles (not a fix) and you should be able to find out. Do you expect it to stop or be reflected?

Everything should be able to be deduced from this sentence in the doc. “This command can be used to freeze certain atoms in the simulation by zeroing their force, either for running dynamics or performing an energy minimization.”

Might have put some confusing emphasis there. Do not confuse freeze with frozen. Your model wall acts just like any other model wall, it has infinite mass.

Thank you so much Eric for your reply!

Might have put some confusing emphasis there. Do not confuse freeze with frozen. Your model wall acts just like any other model wall, it has infinite mass.

Regards,
Eric Murphy
Graduate Research Assistant, Mechanical Engineering
Operations Coordinator, CoMFRE: Multiphase Flow Research and Education
Iowa State University

LinkedIn | ResearchGate | Google Scholar

Dear Lammps users,

I am trying to simulate a liquid flow between two parallel fixed walls.
The walls are fixed by "fix setforce 0.0 0.0 0.0" and "velocity set 0.0 0.0
0.0". I was wondering when the walls are fixed, can I consider them as
adiabatic walls or they are heat sinks with the constant temperature of
zero?

​neither is correct. your wall particles *are* at 0K, but because they are
immobilized, they are not a heat sink, i.e. they do not "consume" kinetic
energy.
yet, they are still different from wall particles that are only restrained
and thus can exchange energy with your fluid.
instead they will induce a more ordered environment ​near the wall. how
much, however, depends on the details of your setup.

axel.

Dear Axel: Many thanks for your reply!

Dear Lammps users,

I am trying to simulate a liquid flow between two parallel fixed walls. The walls are fixed by “fix setforce 0.0 0.0 0.0” and “velocity set 0.0 0.0 0.0”. I was wondering when the walls are fixed, can I consider them as adiabatic walls or they are heat sinks with the constant temperature of zero?

​neither is correct. your wall particles are at 0K, but because they are immobilized, they are not a heat sink, i.e. they do not “consume” kinetic energy.
yet, they are still different from wall particles that are only restrained and thus can exchange energy with your fluid.
instead they will induce a more ordered environment ​near the wall. how much, however, depends on the details of your setup.

axel.