Couette flow simulation

Dear all,

I’m working on simulation of couette flow of liquid argon. I defined 3 types of atoms, two types have mass equals 4 and one type has mass of 1. Then I defined 3 regions: two regions as the walls of channel and one region as the fluid. My objective is to simulate the wall with density=2.73 σ3 and fluid with density=0.8 σ3. Based on my understanding, the scale arguments of lattice is the density for lj units.

When I use 0.8 for both lattice arguments in my input file (two walls and liquid), my results seem correct. However, if I chose 2.73 for lattice argument of two walls and 0.8 for lattice argument of liquid, I get very large numbers for energy, pressure and volume in output file and an “ERROR:Lost atoms: original 4479 current 4443”.

I was wondering if you have any idea that how can I modify my input file and please let me know if it has any problem in creation of geometry and region. I attached my input file and velocity distribution (when I use the same lattice arguments for liquid and wall (0.8)).

I really appreciate your help.

Regards,

Hamed.

Velocity distribution.JPG

in.flow.couette (2.09 KB)

Dear Hamed,

2.73 sigma^-3 is a very large density. You can check that a fcc
crystal of LJ atoms at mechanical equilibrium [i.e., with an
inter-atomic distance r_eq = 2^(1/6) sigma] has a density of 1
sigma^-3. With a density of 2.73 sigma^-3, there will be large
repulsive forces between the atoms, which could make the simulation
unstable.

Best regards,
Laurent

2016-01-10 22:04 GMT+01:00 EsmailzadehKhosravieh, Hamed
<[email protected]>:

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