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lammps/examples/USER/sph/water_collapse/water_collapse.lmp
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water_collapse.lmp
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processors * 1 1 # manually assign processors to spatial regions
atom_style meso
dimension 2
newton on
boundary f f p
units lj
read_data data.initial
variable h equal 0.03
variable c equal 10.0 # soundspeed for Tait's EOS
variable dt equal 0.1*${h}/${c} # upper limit of timestep based on CFL-like criterion
variable nrun equal 15.0/${dt} # roughly estimate number of timesteps needed for 7.5 seconds
group bc type 2 # assign group name "bc" to boundary particles (type 2)
group water type 1 # assign group name "water" to water particles (type 1)
# use hybrid pairstyle which does density summation with cutoff ${h} every timestep (1)
pair_style hybrid/overlay sph/rhosum 1 sph/taitwater
pair_coeff * * sph/taitwater 1000.0 ${c} 1.0 ${h} # use target density of 1000, soundspeed ${c} for Tait's EOS
pair_coeff 1 1 sph/rhosum ${h}
fix gfix water gravity -9.81 vector 0 1 0 # add gravity. This fix also computes potential energy of mass in gravity field.
fix 2d_fix all enforce2d
compute rho_peratom all meso/rho/atom
compute e_peratom all meso/e/atom
compute esph all reduce sum c_e_peratom
compute ke all ke
variable etot equal c_esph+c_ke+f_gfix
# adjust nevery | min. allowed dt | max. allowed dt | max. travel distance per dt # // ${dt} ~= CFL criterion 0.1*h/c
fix dtfix all dt/reset 1 NULL ${dt} 0.0005 units box # use a variable timestep
# time-integrate position, velocities, internal energy and density of water particles
fix integrate_water_fix water meso
# time-integrate only internal energy and density of boundary particles
fix integrate_bc_fix bc meso/stationary
dump dump_id all custom 100 dump.lammpstrj id type xs ys zs c_rho_peratom c_e_peratom fx fy
dump_modify dump_id first yes
thermo 10
thermo_style custom step ke c_esph v_etot f_gfix press time f_dtfix
thermo_modify norm no
neigh_modify every 5 delay 0 check no
variable skin equal 0.3*${h}
neighbor ${skin} bin # set Verlet list skin distance
run ${nrun}
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