Helium flow

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1

Hi All,
I’m new to LAMMPS. I want to know if I can simulate the helium flow through a tube at 100 m/s fluid speed and at 4 Kelvin?
Is there a sample input file for such a simple system?
Then I will add a nano particle to the simulation.
Thanks

2

Hi All,
I'm new to LAMMPS. I want to know if I can simulate the helium flow
through a tube at 100 m/s fluid speed and at 4 Kelvin?

​new to the LAMMPS software or new to MD simulation​s in general?

yes, it is possible to set up such a simulation. you can easily compute the
necessary lateral velocity for the flow and add it to the velocity of the
(pre-equilibrated and pre-thermalized) mobile atom.

Is there a sample input file for such a simple system?

no. ​from the perspective of setting up an MD simulation, this doesn't
qualify as a "simple" system for several reasons:
- you have a non-equilibrium system
- you have a multi-component system
- you have a non-bulk system
- you have to use what is called in LAMMPS a temperature bias to apply a
thermalization to the desired 4K temperature without including the kinetic
energy due to the flow​ itself.

so, if you are new to LAMMPS *and* new to MD, you should start and gain
experience with simpler systems (bulk, equilibrium, and single component)
and reproduce published results with those and then add "complications"
one-by-one.

axel.

3

Thanks Axel,
I have experience with Gromacs and Ab-initio MD. However, it is my first time using LAMMPS and also simulating gas flow. So could you please suggest a starting point?
Thanks

Sincerely,

Muhamed Amin

Hi All,
I’m new to LAMMPS. I want to know if I can simulate the helium flow through a tube at 100 m/s fluid speed and at 4 Kelvin?

​new to the LAMMPS software or new to MD simulation​s in general?

yes, it is possible to set up such a simulation. you can easily compute the necessary lateral velocity for the flow and add it to the velocity of the (pre-equilibrated and pre-thermalized) mobile atom.

Is there a sample input file for such a simple system?

no. ​from the perspective of setting up an MD simulation, this doesn’t qualify as a “simple” system for several reasons:

  • you have a non-equilibrium system
  • you have a multi-component system
  • you have a non-bulk system
  • you have to use what is called in LAMMPS a temperature bias to apply a thermalization to the desired 4K temperature without including the kinetic energy due to the flow​ itself.

so, if you are new to LAMMPS and new to MD, you should start and gain experience with simpler systems (bulk, equilibrium, and single component) and reproduce published results with those and then add “complications” one-by-one.

axel.

4

Thanks Axel,
I have experience with Gromacs and Ab-initio MD. However, it is my first
time using LAMMPS and also simulating gas flow. So could you please suggest
a starting point?

​i would still follow the outline i've given in my previous response. since
LAMMPS inputs are processed line-by-line, it is good practice to build
complex simulations incrementally (and verify intermediate results). with
multi-component systems, it is also best practice to first simulate each
component separately and reproduce published results before combining them.
you can look through the examples provided with LAMMPS for additional
inspiration.

axel.​