1
#===========================================================================#
2
# Drag force on a single sphere. #
4
# Here, gamma (used in the calculation of the particle-fluid interaction #
5
# force) is calculated by default. The resulting equilibrium drag force #
6
# should correspond to the Stokes drag force on a sphere with a slightly #
7
# larger "hydrodynamic" radius, than that given by the placement of the #
10
# Sample output from this run can be found in the file: #
11
# 'defaultgamma_drag.out' #
12
#===========================================================================#
19
#----------------------------------------------------------------------------
20
# Need a neighbor bin size smaller than the lattice-Boltzmann grid spacing
21
# to ensure that the particles belonging to a given processor remain inside
22
# that processors lattice-Boltzmann grid.
23
# The arguments for neigh_modify have been set to "delay 0 every 1", again
24
# to ensure that the particles belonging to a given processor remain inside
25
# that processors lattice-Boltzmann grid. However, these values can likely
26
# be somewhat increased without issue. If a problem does arise (a particle
27
# is outside of its processors LB grid) an error message is printed and
28
# the simulation is terminated.
29
#----------------------------------------------------------------------------
31
neigh_modify delay 0 every 1
33
read_data data.one_radius16d2
35
#----------------------------------------------------------------------------
36
# None of the particles comprising the spherical colloidal object should
37
# interact with one another.
38
#----------------------------------------------------------------------------
39
pair_style lj/cut 2.45
40
pair_coeff * * 0.0 0.0 2.45
41
neigh_modify exclude type 1 1
43
#----------------------------------------------------------------------------
44
# Need to use a large particle mass in order to approximate an infintely
45
# massive particle, moving at constant velocity through the fluid.
46
#----------------------------------------------------------------------------
50
velocity all set 0.0 0.0001 0.0 units box
52
#---------------------------------------------------------------------------
53
# Create a lattice-Boltzmann fluid covering the simulation domain.
54
# All of the particles in the simulation apply a force to the fluid.
55
# Use the standard LB integration scheme, a fluid density = 1.0,
56
# fluid viscosity = 1.0, lattice spacing dx=4.0, and mass unit, dm=10.0.
57
# Use the default method to calculate the interaction force between the
58
# particles and the fluid. This calculation requires the surface area
59
# of the composite object represented by each particle node. By default
60
# this area is assumed equal to dx*dx; however, since this is not the case
61
# here, it is input through the setArea keyword (i.e. particles of type 1
62
# correspond to a surface area of 10.3059947).
63
# Use the trilinear interpolation stencil to distribute the force from
64
# a given particle onto the fluid mesh (results in a smaller hydrodynamic
65
# radius than if the Peskin stencil is used).
66
# Print the force and torque acting on the particle to the screen at each
68
#----------------------------------------------------------------------------
69
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
71
#---------------------------------------------------------------------------
72
# For this simulation the colloidal particle moves at a constant velocity
73
# through the fluid. As such, we do not wish to apply the force from
74
# the fluid back onto the object. Therefore, we do not use any of the
75
# viscous_lb, rigid_pc_sphere, or pc fixes, and simply integrate the
76
# particle motion using one of the built-in LAMMPS integrators.
77
#---------------------------------------------------------------------------