forked from lijiext/lammps
81 lines
4.3 KiB
Plaintext
Executable File
81 lines
4.3 KiB
Plaintext
Executable File
#===========================================================================#
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# Drag force on a single sphere. #
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# #
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# Here, gamma (used in the calculation of the particle-fluid interaction #
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# force) is calculated by default. The resulting equilibrium drag force #
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# should correspond to the Stokes drag force on a sphere with a slightly #
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# larger "hydrodynamic" radius, than that given by the placement of the #
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# particle nodes. #
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# #
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# Sample output from this run can be found in the file: #
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# 'defaultgamma_drag.out' #
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#===========================================================================#
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units micro
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dimension 3
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boundary p p f
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atom_style atomic
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#----------------------------------------------------------------------------
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# Need a neighbor bin size smaller than the lattice-Boltzmann grid spacing
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# to ensure that the particles belonging to a given processor remain inside
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# that processors lattice-Boltzmann grid.
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# The arguments for neigh_modify have been set to "delay 0 every 1", again
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# to ensure that the particles belonging to a given processor remain inside
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# that processors lattice-Boltzmann grid. However, these values can likely
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# be somewhat increased without issue. If a problem does arise (a particle
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# is outside of its processors LB grid) an error message is printed and
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# the simulation is terminated.
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#----------------------------------------------------------------------------
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neighbor 1.0 bin
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neigh_modify delay 0 every 1
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read_data data.one_radius16d2
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#----------------------------------------------------------------------------
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# None of the particles comprising the spherical colloidal object should
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# interact with one another.
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#----------------------------------------------------------------------------
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pair_style lj/cut 2.45
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pair_coeff * * 0.0 0.0 2.45
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neigh_modify exclude type 1 1
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#----------------------------------------------------------------------------
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# Need to use a large particle mass in order to approximate an infintely
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# massive particle, moving at constant velocity through the fluid.
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#----------------------------------------------------------------------------
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mass * 10000.0
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timestep 3.0
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velocity all set 0.0 0.0001 0.0 units box
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#---------------------------------------------------------------------------
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# Create a lattice-Boltzmann fluid covering the simulation domain.
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# All of the particles in the simulation apply a force to the fluid.
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# Use the standard LB integration scheme, a fluid density = 1.0,
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# fluid viscosity = 1.0, lattice spacing dx=4.0, and mass unit, dm=10.0.
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# Use the default method to calculate the interaction force between the
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# particles and the fluid. This calculation requires the surface area
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# of the composite object represented by each particle node. By default
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# this area is assumed equal to dx*dx; however, since this is not the case
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# here, it is input through the setArea keyword (i.e. particles of type 1
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# correspond to a surface area of 10.3059947).
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# Use the trilinear interpolation stencil to distribute the force from
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# a given particle onto the fluid mesh (results in a smaller hydrodynamic
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# radius than if the Peskin stencil is used).
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# Print the force and torque acting on the particle to the screen at each
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# timestep.
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#----------------------------------------------------------------------------
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fix 1 all lb/fluid 1 1 1.0 1.0 setArea 1 10.3059947 dx 4.0 dm 10.0 trilinear calcforce 10 all
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#---------------------------------------------------------------------------
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# For this simulation the colloidal particle moves at a constant velocity
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# through the fluid. As such, we do not wish to apply the force from
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# the fluid back onto the object. Therefore, we do not use any of the
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# viscous_lb, rigid_pc_sphere, or pc fixes, and simply integrate the
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# particle motion using one of the built-in LAMMPS integrators.
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#---------------------------------------------------------------------------
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fix 2 all nve
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run 100000
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