Tutorial for exchanging meshes with Kratos

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Table of Contents

• Mesh Exchange with Kratos
• Next steps

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This tutorial shows how to exchange meshes with Kratos. It is required to do this tutorial first.

Mesh Exchange with Kratos

Here we try to send the mesh (in the form of CoSimIO::ModelPart) to Kratos and get it back from it. Then we can check if both meshes are the same. The Kratos side of this tutorial can be found in the C++ tutorial.

On the other side we use first export mesh and then import it back, following what was done in this tutorial:

import CoSimIO

def cosimio_check_equal(a, b):
    assert a == b

# Connection Settings
settings = CoSimIO.Info()
settings.SetString("my_name", "my_code")
settings.SetString("connect_to", "Kratos")
settings.SetInt("echo_level", 1)
settings.SetString("version", "1.25")

# Connecting
return_info = CoSimIO.Connect(settings)
cosimio_check_equal(return_info.GetInt("connection_status"), CoSimIO.ConnectionStatus.Connected)
connection_name = return_info.GetString("connection_name")

# Creating the mesh
nodal_coords = [
    (0.0, 2.5, 1.0),
    (2.0, 0.0, 1.5),
    (2.0, 2.5, 1.5),
    (4.0, 2.5, 1.7),
    (4.0, 0.0, 1.7),
    (6.0, 0.0, 1.8)
]

element_connectivities = [
    (1, 2, 3),
    (2, 4, 3),
    (2, 5, 4),
    (4, 5, 6),
]

model_part = CoSimIO.ModelPart("mp_exchange")

for i, coords in enumerate(nodal_coords):
    model_part.CreateNewNode(i+1, *coords)

for i, conn in enumerate(element_connectivities):
    model_part.CreateNewElement(i+1, CoSimIO.ElementType.Triangle3D3, conn)

# Exporting mesh to Kratos
info = CoSimIO.Info()
info.SetString("identifier", "fluid_mesh")
info.SetString("connection_name", connection_name)
return_info = CoSimIO.ExportMesh(info, model_part)

# Importing the same mesh from Kratos
info = CoSimIO.Info()
info.SetString("identifier", "fluid_mesh")
info.SetString("connection_name", connection_name)

model_part_import = CoSimIO.ModelPart("mp_import")
return_info = CoSimIO.ImportMesh(info, model_part_import)

# Checking the imported mesh
expected_nodal_coords = [
    (0.0, 2.5, 1.0),
    (2.0, 0.0, 1.5),
    (2.0, 2.5, 1.5),
    (4.0, 2.5, 1.7),
    (4.0, 0.0, 1.7),
    (6.0, 0.0, 1.8)
]

expected_element_connectivities = [
    (1, 2, 3),
    (2, 4, 3),
    (2, 5, 4),
    (4, 5, 6),
]

cosimio_check_equal(model_part_import.NumberOfNodes(), len(expected_nodal_coords))
cosimio_check_equal(model_part_import.NumberOfElements(), len(expected_element_connectivities))

for i, (coords, node) in enumerate(zip(expected_nodal_coords, model_part_import.Nodes)):
    cosimio_check_equal(i+1, node.Id())
    cosimio_check_equal(coords[0], node.X())
    cosimio_check_equal(coords[1], node.Y())
    cosimio_check_equal(coords[2], node.Z())

for i, (conn, elem) in enumerate(zip(expected_element_connectivities, model_part_import.Elements)):
    cosimio_check_equal(i+1, elem.Id())
    cosimio_check_equal(elem.Type(), CoSimIO.ElementType.Triangle3D3)
    cosimio_check_equal(elem.NumberOfNodes(), 3)
    for j, node in enumerate(elem.Nodes):
        cosimio_check_equal(node.Id(), conn[j])

# Disconnecting
disconnect_settings = CoSimIO.Info()
disconnect_settings.SetString("connection_name", connection_name)
return_info = CoSimIO.Disconnect(disconnect_settings)
cosimio_check_equal(return_info.GetInt("connection_status"), CoSimIO.ConnectionStatus.Disconnected)

This file can be found in integration_tutorials/python/mesh_exchange.py

Then you may run your executable with python script of Kratos from your working directory:

python3 path/to/mesh_exchange.py & python3 path/to/import_export_mesh.py

Next steps

In the next tutorial, meshes are exchanged with Kratos and mapping is used.