Run a simulation - Step by step

With interactive execution, OpenGeoSys provides a Python interface that lets you advance a simulation one step at a time, inspect intermediate results, and react before continuing. This mechanism underlies what we mean by Co-simulation: the simulation can exchange information with external analyses or tools during runtime—for example, by dynamically adjusting boundary conditions. In this guide, we will show how to:

• Step-by-step simulation control

• Inspect simulation status and intermediate results

• Prepare for mesh manipulation examples - Interactive Mesh manipulation (OGSTools - Integrated). - Interactive Mesh manipulation (Native interface).

Imports and definitions

from pathlib import Path
from tempfile import mkdtemp

from ogs import OGSMesh
from ogs.OGSSimulator import OGSSimulation

from ogstools.examples import load_model_liquid_flow_simple

Select a Project

We will start with a simple liquid flow example.

working_dir = Path(mkdtemp())
prj, meshes = load_model_liquid_flow_simple()
prj.write_input(working_dir / "LiquidFlowSimple.prj")
_ = meshes.save(working_dir)

Initialize the simulation and first step

Use the same arguments as when calling OGS from command line, a list of possible argument are documented under https://www.opengeosys.org/docs/userguide/basics/cli-arguments/

sim1_result_dir = working_dir / "sim1"
sim1_result_dir.mkdir(exist_ok=True)
arguments = [
    "",
    str(working_dir / "LiquidFlowSimple.prj"),
    "-o",
    str(sim1_result_dir),
]
# extend like this: ,"-m", str(mesh_dir), "-l debug", -o", str(output_dir)]

By constructing a OGSSimulation object we start OpenGeoSys and it runs time step 0

sim1 = OGSSimulation(arguments)

print(f"The current simulation time is: {sim1.current_time()} s.")
print(f"The end time defined is: {sim1.end_time()} s.")

The current simulation time is: 0.0 s.
The end time defined is: 100.0 s.

Advance the simulation by a one step

status = sim1.execute_time_step()
print(f"The current simulation time is: {sim1.current_time()} s.")

The current simulation time is: 10.0 s.

Basic simulation loop

The simulation runs step-by-step until a user specified condition is met. This further allows you to manipulate data arrays associated with the mesh or adapt the logic inside the loop.

while (
    # Here, the condition is when simulation reaches the end time:
    sim1.current_time()
    < sim1.end_time()
):

    # Add here your specific code with mesh manipulation:
    my_mesh: OGSMesh = sim1.mesh("domain")
    sim1.execute_time_step()

# Alternatively, run the entire simulation without interaction:
sim1.execute_simulation()
# Necessary to close, otherwise you can not reinitialize simulation with same prj-file (arguments):
sim1.close()

Advance examples with mesh manipulation

Manipulate the mesh with either

• Interactive Mesh manipulation (OGSTools - Integrated).

• Interactive Mesh manipulation (Native interface).