Mahmoud-Sedahmed
commented
1 week ago Dear xiangWu-WW,
By looking at the set parameters in the simulation control file, it seems you set the initial condition as randomly distributing both fluids to reach a target nonwetting fluid saturation of 0.3 (initial_fluid_distribution_option = 6, target_fluid1_saturation = 0.3). But, you are also using pressure boundary conditions at both the inlet and outlet fluids (inlet_BC = 2, outlet_BC = 2) and injecting a pure wetting fluid at the inlet (saturation_injection = 0.0). Such a numerical setup will not achieve your target simulation case of a stable saturation during a steady state simulation. You must set periodic boundary conditions in the flow direction (kper = 1) instead of (kper = 0) and set a driving body force in the flow direction using the parameter (body_force_0) to reach a suitable flow rate. This should give you a steady fluid flow along the domain and keep the fluids' saturation stable around the initial set value.
Regards,
xiangWu-WW
Dear Dr.Mahmoud, In the steady-state simulation, I want to set the saturation of the non-wetting phase to 20%, and I also set this value in the control file, but the final saturation will be less. My goal is to stabilize 30%, rather than the initial saturation of 30, may I ask what parameters need to be modified?
SIMULATION CONTROL
*****
CONTROL FILE FOR MULTIPHASE FLOW SIMULATION IN MF-LBM
*****
=========================== simulation_status ====================================
value stored on job_status.txt
new_simulation - new simulation
continue_simulation - continue previous simulation
simulation_done - previous simulation is finished. stop
simulation_failed - previous simulation failed. stop
simulation_reached_max_step - previous simulation reached maximum step. stop
else - wrong status. stop
=========================== simulation setup =====================================
Initial fluid distribution option:
1 - fluid1 (nonwetting phase) at inlet: drainage
2 - fluid2 (wetting phase) at inlet: imbibition
3 - a fluid1 (nonwetting phase) drop attached to y=1: contact angle measurement
4 - a fluid2 (wetting phase) drop attached to y=1: contact angle measurement
5 - a fluid1 drop located in the center of the domain: surface tension measurement
6 - fluid1 and fluid2 raondomely distributed in the pore space with desired fluid1
saturation: steady state relative perm measurement
0 or else - error!
initial_fluid_distribution_option 6
Benchmark_cmd:
0 - regular simulation
1 - benchmarking simulation (obtain computational performance in MLUPS)
benchmark_cmd 0
Necesssary modifications for extreme large simulations:
nxglobalnyglobalnzglobal may be too large.
parallel I/O for visualization files are needed.
recommended for grid points > 1 billion.
0 - no; 1 - yes
extreme_large_sim_cmd 0
Breakthrough check option:
currently only works for drainage simulation by detecting nonwetting phase
fluid1 near outlet.
0 - do not check; 1 - check
breakthrough_check 0
Steady state option:
0 - non-steady state simulation (complete based on target injected PV or ntime_max)
1 - steady state simulation (complete based on capillary pressure)
2 - steady state simulation (complete based on phase field)
3 - steady state simulation (complete based on saturation)
steady_state_option 3
Convergence_criteria:
used in steady state simulation.
default is 1d-6, use 1d-4 or 1d-3 instead for steady-state-option 3 to reduce simulation
time and deal with fluctuation
convergence_criteria 1e-3
output field data precision (simulation is always double precision):
0 - single precision; 1 - double precision
output_fieldData_precision_cmd 0
Modify_geometry_cmd:
0 do not modify geometry; 1 modify geometry in the code (hard coding, Misc.cpp)
modify_geometry_cmd 0
Use external geometry cmd:
0 - no; 1 - yes
external_geometry_read_cmd 1
choose type size of dimension variables saved in the geometry binary file:
4 - 4 bytes (int, uint, ..etc.); 8 - 8 bytes (long long, unint64, ...etc.)
(0) would be used in relatively small geometries (nxGlobalnyGlobalnzGlobal < 384^3), while (1) would be used in relatively large geometries (nxGlobalnyGlobalnzGlobal >= 384^3)
geometry_dims_type_size 4
Geometry preprocess cmd:
0 - process the geometry boundary infor during the simulation (not recommended for
large simulations);
1 - load external pre-processed geometry boundary info data
geometry_preprocess_cmd 0
Place a porous plate along the flow direction:
0 - no; 1 - block fluid1; 2 - block fluid2
example 1: injecting fluid2 (wetting) during imbibition cycle and block fluid1 from
exiting the inlet.
example 2: injecting fluid1 (nonwetting) during drainage cycle and block fluid1 from
exiting the outlet.
This option should only be used when you fully understand how it works.
porous_plate_cmd 0
Location of the porous plate along flow direction (Z):
placing the porous plate a couple of lattices before or after rock sample is recommended.
example 1 (near outlet): Z_porous_plate = inlet_buffer_layers + nxsample + 2
example 2 (near inlet): Z_porous_plate = inlet_buffer_layers + 1 - 2
only effective when porous_plate_cmd = 1
This option should only be used when you fully understand how it works.
Z_porous_plate 0
Change inlet fluid phase for Z < initial_interface_position:
0 - do nothing
1 - 100% fluid1
2 - 100% fluid2
Use case:
After the completion of the drainage simulation, one can use current fluid distribution
as the starting point to perform imbibition simulation. To reduce the simulation time, one
can eliminate unecessary fluid displacement in buffer zone and numerical artifacts from
open boundary conditions by change the inlet fluid to pure fluid2 (wetting phase).
This option should only be used when you fully understand how it works.
change_inlet_fluid_phase_cmd 0
================================= geometry ======================================
Lattice dimensions nxGlobal, nyGlobal, nzGlobal, must be integral multiple of
npx, npy and npz, respectively
lattice_dimensions 240,240,260
nxGlobal 102 nyGlobal 102 nzGlobal 122
inlet/outlet zone excluded in the bulk properties calculation
1<=k<=n_exclude_inlet and nzglobal-n_exclude_outlet+1<=k<=nzglobal
does not affect simulation
excluded_layers 10,10
n_exclude_inlet 10 n_exclude_outlet 10
domain_wall_status at xmin and xmax, status: 1 - wall; 0 - no wall
domain_wall_status_x 1,1
domain_wall_status_x_min 1 domain_wall_status_x_max 1
domain_wall_status at ymin and ymax, status: 1 - wall; 0 - no wall
domain_wall_status_y 1,1
domain_wall_status_y_min 1 domain_wall_status_y_max 1
default flow direction, domain_wall_status at ymin and ymax, status: 1 - wall; 0 - no wall
domain_wall_status_z 0,0
domain_wall_status_z_min 0 domain_wall_status_z_max 0
periodic BC indicator, 1 periodic, 0 non-periodic
currently, x direction can not apply periodic BC
periodic_indicator 0,0,0
iper 0 jper 0 kper 0
==================================== CUDA information ========================================
Number of threads in a thread block, in each direction
Preferred to be a multiple of 32 (warp size)
block_Threads_X 128 block_Threads_Y 1 block_Threads_Z 1
===================================== MPI information ========================================
mpi process numbers along each axis: npx, npy, npz
x direction domain decomposition disabled: npx = 1
MPI_process_num 1,1,1
npx 1 npy 1 npz 1
Number of halo nodes used in overlaping computation and communication.
x direction domain decomposition disabled and must be 0
This option should only be modified when you fully understand how it works.
MPI_async_layers_num 0,4,4
ix_async 0 iy_async 4 iz_async 4
=============================== fluid property ===================================
fluid viscosity
fluid1_viscosity 0.4 fluid2_viscosity 0.04
surface tension
surface_tension 0.3
Contact angle (measured through fluid 2):
It should always be less than 90 degree due to the particular numerical scheme used in this
code to form desired contact angle. Therefore, fluid 1 is always the nonwetting phase, while
fluid 2 is always the wetting phase.
Imbibition simulation can be performed by injecting fluid 2 instead of fluid 1
theta 10
beta in RK recolor scheme - control the sharpness of the interface (from 0.9 to 0,95 is recommended)
RK_beta 0.95
============================= injection conditions ===============================
inlet_BC selection (overridden by z (flow) direction periodic BC): 1-velocity; 2-pressure
inlet_BC 2
outlet_BC selection (overridden by z (flow) direction periodic BC): 1-convective; 2-pressure
outlet_BC 2
Injecting fluid saturation:
1: pure fluid1 injection (drainage)
0: pure fluid2 injection (imbibition)
0<sa<1: mixed injection
saturation_injection 0.0
Option to stop simulation based on reaching target fluid injection:
It is enabled by modify ntime_max based on injection rate.
The value is in PV (pore-volume).
It is not very precise considering LBM compressibility error.
A negative value will disable target_inject_pore_volume – simulation continues until existing ntime_max
target_inject_pore_volume -1.0
Initial interface position along z direction or initial drop radius for drop test
initial_interface_position 8.0
Capillary number, based on viscosity of fluid1
capillary_number 100e-6
initial value of body force or pressure gradient along z direction
body_force_0 1e-4
override loading inlet density value from the checkpoint file and use a new value based on the pressure gradient
rho_in_new 1
use the BC density value for the outlet density
rho_out_BC 0
Target fluid1 saturation:
used in steady state relative permeability measurement
randomly distribute fluid1 and fluid2 with target fluid1 saturation
target_fluid1_saturation 0.30
================================== timers ========================================
timer: max iterations, will be modified if target_inject_pore_volume > 0
max_time_step 1000000
timer: max iterations for benchmarking
max_time_step_benchmark 100
timer: when to output detailed visualization data - overridden by d_vol_detail if d_vol_detail>0
ntime_visual 5000000
timer: when to output animation (phase info only) data - overridden by d_vol_animation if d_vol_animation>0
ntime_animation 2000
timer: when to output bulk property data - overridden by d_vol_monitor if d_vol_monitor>0
monitor_timer 2000
timer: when to output profile data along flow direction (Z)
monitor_profile_timer = monitor_profile_timer_ratio * monitor_timer
monitor_profile_timer_ratio 5
timer: gaps used to record computation time
it is also used to check the checkpoint data saving status
computation_time_timer 10000
timer: when to display time steps
display_steps_timer 10000
timer: interval to save checkpoint data based on wall clock time, in hours
checkpoint_save_timer 1.0
timer: time interval used to save secondary checkpoint data based on wall clock time, in hours
use a large value to reduce the storage size
checkpoint_2rd_save_timer 5.5
timer: simulation duration in hours
save checkpoint data and exit program after simulation_duration_timer
simulation_duration_timer 168
timer: when to output animation data - based on injected pore volume
only effective for constant velocity BC, disabled if it is a negative value
d_vol_animation -0.05
timer: when to output full field data - based on injected pore volume
only effective for constant velocity BC, disabled if it is a negative value
d_vol_detail -1.0
timer: when to output bulk property data - based on injected pore volume
only effective for constant velocity BC, disabled if it is a negative value
d_vol_monitor -0.01