Getting started with
OpenFOAM-preCICE
for FSI simulations
Uncoupled simulation
Import preCICE
import numpy
# generate mesh
n = 20
y = numpy.linspace(0, 1, n + 1)
dt = 0.01
t = 0
while True:
print("Generating data")
u = 1 - 2 * numpy.random.rand(n)
t = t + dt
if(t > 0.1):
break
Import preCICE
import numpy
import precice
# generate mesh
n = 20
y = numpy.linspace(0, 1, n + 1)
dt = 0.01
t = 0
while True:
print("Generating data")
u = 1 - 2 * numpy.random.rand(n)
t = t + dt
if(t > 0.1):
break
Configure preCICE
import numpy
import precice
# generate mesh
n = 20
y = numpy.linspace(0, 1, n + 1)
# preCICE setup
participant_name = "Generator"
config_file_name = "../precice-config.xml"
solver_process_index = 0
solver_process_size = 1
interface =
precice.Interface(
participant_name,
config_file_name,
solver_process_index,
solver_process_size
)
dt = 0.01
t = 0
while True:
print("Generating data")
u = 1 - 2 * numpy.random.rand(n)
t = t + dt
if(t > 0.1):
break
Define the coupling mesh
import numpy
import precice
# generate mesh
n = 20
y = numpy.linspace(0, 1, n + 1)
# preCICE setup
participant_name = "Generator"
config_file_name = "../precice-config.xml"
solver_process_index = 0
solver_process_size = 1
interface =
precice.Interface(
participant_name,
config_file_name,
solver_process_index,
solver_process_size
)
# Get the preCICE mesh id
mesh_name = "Generator-Mesh"
mesh_id = interface.get_mesh_id(mesh_name)
# Define the coupling mesh
vertices = [[1, y0] for y0 in y[:-1]]
vertex_ids = interface.set_mesh_vertices(mesh_id, vertices)
dt = 0.01
t = 0
while True:
print("Generating data")
u = 1 - 2 * numpy.random.rand(n)
t = t + dt
if(t > 0.1):
break
Initialize and finalize preCICE
import numpy
import precice
# generate mesh
n = 20
y = numpy.linspace(0, 1, n + 1)
# preCICE setup
participant_name = "Generator"
config_file_name = "../precice-config.xml"
solver_process_index = 0
solver_process_size = 1
interface =
precice.Interface(
participant_name,
config_file_name,
solver_process_index,
solver_process_size
)
# Get the preCICE mesh id
mesh_name = "Generator-Mesh"
mesh_id = interface.get_mesh_id(mesh_name)
# Define the coupling mesh
vertices = [[1, y0] for y0 in y[:-1]]
vertex_ids = interface.set_mesh_vertices(mesh_id, vertices)
interface.initialize()
dt = 0.01
t = 0
while True:
print("Generating data")
u = 1 - 2 * numpy.random.rand(n)
t = t + dt
if(t > 0.1):
break
interface.finalize()
Advance the coupling
import numpy
import precice
# generate mesh
n = 20
y = numpy.linspace(0, 1, n + 1)
# preCICE setup
participant_name = "Generator"
config_file_name = "../precice-config.xml"
solver_process_index = 0
solver_process_size = 1
interface =
precice.Interface(
participant_name,
config_file_name,
solver_process_index,
solver_process_size
)
# Get the preCICE mesh id
mesh_name = "Generator-Mesh"
mesh_id = interface.get_mesh_id(mesh_name)
# Define the coupling mesh
vertices = [[1, y0] for y0 in y[:-1]]
vertex_ids = interface.set_mesh_vertices(mesh_id, vertices)
interface.initialize()
dt = 0.01
t = 0
while True:
print("Generating data")
u = 1 - 2 * numpy.random.rand(n)
t = t + dt
if(t > 0.1):
break
interface.finalize()
Advance the coupling
import numpy
import precice
# generate mesh
n = 20
y = numpy.linspace(0, 1, n + 1)
# preCICE setup
participant_name = "Generator"
config_file_name = "../precice-config.xml"
solver_process_index = 0
solver_process_size = 1
interface =
precice.Interface(
participant_name,
config_file_name,
solver_process_index,
solver_process_size
)
# Get the preCICE mesh id
mesh_name = "Generator-Mesh"
mesh_id = interface.get_mesh_id(mesh_name)
# Define the coupling mesh
vertices = [[1, y0] for y0 in y[:-1]]
vertex_ids = interface.set_mesh_vertices(mesh_id, vertices)
interface.initialize()
dt = 0.01
t = 0
while True:
print("Generating data")
u = 1 - 2 * numpy.random.rand(n)
interface.advance(dt)
t = t + dt
if(t > 0.1):
break
interface.finalize()
Advance the coupling
import numpy
import precice
# generate mesh
n = 20
y = numpy.linspace(0, 1, n + 1)
# preCICE setup
participant_name = "Generator"
config_file_name = "../precice-config.xml"
solver_process_index = 0
solver_process_size = 1
interface =
precice.Interface(
participant_name,
config_file_name,
solver_process_index,
solver_process_size
)
# Get the preCICE mesh id
mesh_name = "Generator-Mesh"
mesh_id = interface.get_mesh_id(mesh_name)
# Define the coupling mesh
vertices = [[1, y0] for y0 in y[:-1]]
vertex_ids = interface.set_mesh_vertices(mesh_id, vertices)
interface.initialize()
dt = 0.01
t = 0
while interface.is_coupling_ongoing():
print("Generating data")
u = 1 - 2 * numpy.random.rand(n)
interface.advance(dt)
t = t + dt
interface.finalize()
Advance the coupling
import numpy
import precice
# generate mesh
n = 20
y = numpy.linspace(0, 1, n + 1)
# preCICE setup
participant_name = "Generator"
config_file_name = "../precice-config.xml"
solver_process_index = 0
solver_process_size = 1
interface =
precice.Interface(
participant_name,
config_file_name,
solver_process_index,
solver_process_size
)
# Get the preCICE mesh id
mesh_name = "Generator-Mesh"
mesh_id = interface.get_mesh_id(mesh_name)
# Define the coupling mesh
vertices = [[1, y0] for y0 in y[:-1]]
vertex_ids = interface.set_mesh_vertices(mesh_id, vertices)
interface.initialize()
dt = 0.01
t = 0
while interface.is_coupling_ongoing():
print("Generating data")
u = 1 - 2 * numpy.random.rand(n)
precice_dt = interface.advance(dt)
t = t + dt
interface.finalize()
Advance the coupling
import numpy
import precice
# generate mesh
n = 20
y = numpy.linspace(0, 1, n + 1)
# preCICE setup
participant_name = "Generator"
config_file_name = "../precice-config.xml"
solver_process_index = 0
solver_process_size = 1
interface =
precice.Interface(
participant_name,
config_file_name,
solver_process_index,
solver_process_size
)
# Get the preCICE mesh id
mesh_name = "Generator-Mesh"
mesh_id = interface.get_mesh_id(mesh_name)
# Define the coupling mesh
vertices = [[1, y0] for y0 in y[:-1]]
vertex_ids = interface.set_mesh_vertices(mesh_id, vertices)
precice_dt = interface.initialize()
dt = 0.01
t = 0
while interface.is_coupling_ongoing():
dt = np.minimum(dt, precice_dt)
print("Generating data")
u = 1 - 2 * numpy.random.rand(n)
precice_dt = interface.advance(dt)
t = t + dt
interface.finalize()
(similar changes in propagator.py - try it at home)
Nothing happening?
Did we forget something?Write & read data
import numpy
import precice
# generate mesh
n = 20
y = numpy.linspace(0, 1, n + 1)
# preCICE setup
participant_name = "Generator"
config_file_name = "../precice-config.xml"
solver_process_index = 0
solver_process_size = 1
interface =
precice.Interface(
participant_name,
config_file_name,
solver_process_index,
solver_process_size
)
# Get the preCICE mesh id
mesh_name = "Generator-Mesh"
mesh_id = interface.get_mesh_id(mesh_name)
# Define the coupling mesh
vertices = [[1, y0] for y0 in y[:-1]]
vertex_ids = interface.set_mesh_vertices(mesh_id, vertices)
precice_dt = interface.initialize()
dt = 0.01
t = 0
while interface.is_coupling_ongoing():
dt = np.minimum(dt, precice_dt)
print("Generating data")
u = 1 - 2 * numpy.random.rand(n)
precice_dt = interface.advance(dt)
t = t + dt
interface.finalize()
Write & read data
import numpy
import precice
# generate mesh
n = 20
y = numpy.linspace(0, 1, n + 1)
# preCICE setup
participant_name = "Generator"
config_file_name = "../precice-config.xml"
solver_process_index = 0
solver_process_size = 1
interface =
precice.Interface(
participant_name,
config_file_name,
solver_process_index,
solver_process_size
)
# Get the preCICE mesh id
mesh_name = "Generator-Mesh"
mesh_id = interface.get_mesh_id(mesh_name)
# Define the coupling mesh
vertices = [[1, y0] for y0 in y[:-1]]
vertex_ids = interface.set_mesh_vertices(mesh_id, vertices)
# Get the exchanged data id
data_name = "Data"
data_id = interface.get_data_id(data_name, mesh_id)
precice_dt = interface.initialize()
dt = 0.01
t = 0
while interface.is_coupling_ongoing():
dt = np.minimum(dt, precice_dt)
print("Generating data")
u = 1 - 2 * numpy.random.rand(n)
interface.write_block_scalar_data(data_id, vertex_ids, u)
precice_dt = interface.advance(dt)
# interface.read_block_scalar_data(data_id, vertex_ids, u)
t = t + dt
interface.finalize()
Data is being transfered!
Most basic case: uni-directional, serial-explicit, nearest-neighbor mapping, ...preCICE configuration
Visual representation of precice-config.xml using the config visualizer.
Configure OpenFOAM
// fluid-openfoam/0/U
flap
{
type movingWallVelocity;
value uniform (0 0 0);
}
// fluid-openfoam/0/pointDisplacement
flap
{
type fixedValue;
value $internalField;
}
// fluid-openfoam/constant/dynamicMeshDict
solver displacementLaplacian;
Load the OpenFOAM adapter
// fluid-openfoam/system/controlDict
functions
{
preCICE_Adapter
{
type preciceAdapterFunctionObject;
libs ("libpreciceAdapterFunctionObject.so");
}
}
// Don't forget to build the adapter with Allwmake
Configure the OpenFOAM adapter
// fluid-openfoam/system/preciceDict
preciceConfig "../precice-config.xml";
participant Fluid;
modules (FSI);
interfaces {
Interface1 {
mesh Fluid-Mesh;
patches (flap);
locations faceCenters;
readData (Displacement);
writeData (Force);
};
};
FSI {
rho rho [1 -3 0 0 0 0 0] 1;
}
Configure the CalculiX adapter
// solid-calculix/config.yml
participants:
Solid:
interfaces:
- nodes-mesh: Solid-Mesh
patch: surface
read-data: [Force]
write-data: [Displacement]
precice-config-file: ../precice-config.xml
Configure preCICE
Configure preCICE
<solver-interface dimensions="2">
<data:vector name="Force" />
<data:vector name="Displacement" />
<mesh name="Fluid-Mesh">
<use-data name="Force" />
<use-data name="Displacement" />
</mesh>
<mesh name="Solid-Mesh">
<use-data name="Displacement" />
<use-data name="Force" />
</mesh>
<participant name="Fluid">
<export:vtk directory="results" />
<use-mesh name="Fluid-Mesh" provide="yes" />
<use-mesh name="Solid-Mesh" from="Solid" />
<write-data name="Force" mesh="Fluid-Mesh" />
<read-data name="Displacement" mesh="Fluid-Mesh" />
<mapping:rbf-thin-plate-splines
direction="write"
from="Fluid-Mesh"
to="Solid-Mesh"
constraint="conservative" />
<mapping:rbf-thin-plate-splines
direction="read"
from="Solid-Mesh"
to="Fluid-Mesh"
constraint="consistent" />
</participant>
<participant name="Solid">
<use-mesh name="Solid-Mesh" provide="yes" />
<write-data name="Displacement" mesh="Solid-Mesh" />
<read-data name="Force" mesh="Solid-Mesh" />
<watch-point mesh="Solid-Mesh" name="Flap-Tip" coordinate="0.0;1" />
</participant>
<m2n:sockets from="Fluid" to="Solid" exchange-directory=".." />
<coupling-scheme:serial-explicit>
<participants first="Fluid" second="Solid" />
<max-time value="1.5" />
<time-window-size value="0.01" />
<exchange data="Force" mesh="Solid-Mesh" from="Fluid" to="Solid" />
<exchange data="Displacement" mesh="Solid-Mesh" from="Solid" to="Fluid" />
</coupling-scheme:serial-explicit>
</solver-interface>
What we did so far: serial-explicit scheme
Let's try an implicit coupling scheme
Configure the coupling scheme
<coupling-scheme:serial-implicit>
<participants first="Fluid" second="Solid" />
<max-time value="1.5" />
<time-window-size value="0.01" />
<exchange data="Force" mesh="Solid-Mesh" from="Fluid" to="Solid" />
<exchange data="Displacement" mesh="Solid-Mesh" from="Solid" to="Fluid" />
<relative-convergence-measure limit="5e-3" data="Displacement" mesh="Solid-Mesh" />
<relative-convergence-measure limit="5e-3" data="Force" mesh="Solid-Mesh" />
<max-iterations value="50" />
<acceleration:constant>
<relaxation value="0.5" />
</acceleration:constant>
</coupling-scheme:serial-implicit>
Too slow! Can we do better?
Improvement 1: Aitken under-relaxation
<acceleration:aitken>
<data name="Displacement" mesh="Solid-Mesh" />
<initial-relaxation value="0.5" />
</acceleration:aitken>
Note: This simulation is reaching a steady-state, thus differences diffuse
Improvement 2: Anderson acceleration
<acceleration:IQN-ILS>
<data name="Displacement" mesh="Solid-Mesh" />
<initial-relaxation value="0.5" />
<preconditioner type="residual-sum" />
<filter type="QR2" limit="1e-2" />
<max-used-iterations value="100" />
<time-windows-reused value="15" />
</acceleration:IQN-ILS>
There are also parallel schemes
Improvement 3: Parallel coupling schemes
<coupling-scheme:parallel-implicit>
<time-window-size value="0.01" />
<max-time value="1.5" />
<participants first="Fluid" second="Solid" />
<exchange data="Force" mesh="Solid-Mesh" from="Fluid" to="Solid" />
<exchange data="Displacement" mesh="Solid-Mesh" from="Solid" to="Fluid" />
<max-iterations value="50" />
<relative-convergence-measure limit="5e-3" data="Displacement" mesh="Solid-Mesh" />
<relative-convergence-measure limit="5e-3" data="Force" mesh="Solid-Mesh" />
<acceleration:IQN-ILS>
<data name="Displacement" mesh="Solid-Mesh" />
<data name="Force" mesh="Solid-Mesh" />
<initial-relaxation value="0.5" />
<preconditioner type="residual-sum" />
<filter type="QR2" limit="1e-2" />
<max-used-iterations value="100" />
<time-windows-reused value="15" />
</acceleration:IQN-ILS>
</coupling-scheme:parallel-implicit>
Beware: Configuration not fine-tuned, not rigorous comparison, application context.
Rigorous comparison from the literature
Source: Dissertation of Benjamin Uekermann (2016)
Rigorous comparison from the literature
Source: Dissertation of Benjamin Uekermann (2016)