I am trying to carry out simulations of water compression in cylindrical tubes using SPH Module of LAMMPS.
To understand the writing the input file for my problem I am referring to “Shear Cavity Flow” Example given in LAMMPS-SPH Documentation.
When I run the simulation for the “Example Shear Cavity Flow” The temperatures are coming to be very high (~10^8 K).
I could not understand ,Why the temperatures are so huge?(Log file Attached)
Any suggestion or comments would be helpful.
The same problem occurs in my actual simulation of Water Compression under normal conditions as well where the temperatures are reaching in the order of ~10^16- 10^22 K instead of . because of it the atoms flyoff and get lost.
%%%%%%%%%Please find the input file of Shear Cavity-Flow example :%%%%%%%
create simulation box
region box block -0.050e-3 1.044e-3 -0.05e-3 1.044e-3 -1.0e-6 1.0e-6 units box
create_box 3 box
create fluid particles
region fluid block 0.0001e-3 0.999e-3 0.0001e-3 0.999e-3 EDGE EDGE side in units box
lattice sq 0.025e-3
create_atoms 1 region fluid
create bottom, left, and right wall
region walls block 0.0001e-3 0.999e-3 0.0001e-3 EDGE EDGE EDGE side out units box
lattice sq2 0.025e-3
create_atoms 2 region walls
create a driver strip of particles, which exerts shear forces on the fluid
region driver block EDGE EDGE 0.999e-3 EDGE EDGE EDGE side in units box
create_atoms 3 region driver
group fluid type 1
group walls type 2
group driver type 3
group integrate_full union fluid driver
mass 3 2.0e-7
mass 2 2.0e-7
mass 1 4.0e-7
set group all meso/rho 1000.0
use Tait’s EOS in combination with Morris’ laminar viscosity.
We set rho_0 = 1000 kg/m^3, c = 0.1 m/s, h = 6.5e-5 m.
The dynamic viscosity is set to 1.0e-3 Pa s, corresponding to a kinematic viscosity of 1.0e-6 m^2/s
pair_style hybrid sph/taitwater/morris
pair_coeff * * sph/taitwater/morris 1000 0.1 1.0e-3 6.5e-5
pair_coeff 2 3 none # exclude interaction between walls and shear driver
compute rho_peratom all meso/rho/atom
compute e_peratom all meso/e/atom
compute ke_peratom all ke/atom
compute esph all reduce sum c_e_peratom
compute ke all ke
variable etot equal c_ke+c_esph
assign a constant velocity to shear driver
velocity driver set 0.001 0.0 0.0 units box
fix freeze_fix driver setforce 0.0 0.0 0.0
do full time integration for shear driver and fluid, but keep walls stationary
fix integrate_fix_full integrate_full meso
fix integrate_fix_stationary walls meso/stationary
dump dump_id all custom 100 dump.lammpstrj id type xs ys zs vx vy c_rho_peratom c_e_peratom
dump_modify dump_id first yes
thermo_style custom step c_esph v_etot temp
thermo_modify norm no
neighbor 3.0e-6 bin
log.lammps (20 KB)