46 lines
1.9 KiB
Plaintext
46 lines
1.9 KiB
Plaintext
The input script in.GD is an example simulation using Gaussian dynamics (GD).
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The simulation is of a simple 2d Lennard-Jones fluid flowing through a pipe.
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For details see online LAMMPS documentation and
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Strong and Eaves, J. Phys. Chem. Lett. 7(10) 2016, p. 1907.
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Note that the run times and box size are chosen to allow a fast example run.
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They are not adequate for a real simulation.
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The script has the following parts:
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1) initialize variables
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These can be modified to customize the simulation. Note that if the
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pipe dimensions L or d are changed, the geometry should be checked
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by visualizing the coordinates in all.init.lammpstrj.
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2) create box
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3) set up potential
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4) create atoms
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5) set up profile-unbiased thermostat (PUT)
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see Evans and Morriss, Phys. Rev. Lett. 56(20) 1986, p. 2172
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By default, this uses boxes which contain on average 8 molecules.
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6) equilibrate without GD
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7) initialize the center-of-mass velocity and run to achieve steady-state
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The system is initialized with a uniform velocity profile, which
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relaxes over the course of the simulation.
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8) collect data
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The data is output in several files:
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GD.out contains the force that GD applies, and the flux in the x- and
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y- directions. The output Jx should be equal to the value of
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J set in section 1, which is 0.1 by default.
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x_profiles contains the velocity, density, and pressure profiles in
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the x-direction. The pressure profile is given by
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(-1/2V)*(c_spa[1] + c_spa[2]), where V is the volume of a
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slice. The pressure profile is computed with IK1, see
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Todd, Evans, and Davis, Phys. Rev. E 52(2) 1995, p. 1627.
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Note that to compare with the pump method, or to
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compute a pressure drop, you must correct this pressure
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profile as described in Strong 2016 above.
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Vy_profile is the velocity profile inside the pipe along the
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y-direction, u_x(y).
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