AxialGeoMultiscale Tutorial

partitioned-pipe-multiscale/README.md

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+---
+title: Partitioned Pipe Multiscale
+permalink: tutorials-partitioned-pipe-multiscale.html
+keywords: OpenFOAM, python
+summary: The 1D-3D Partitioned Pipe is a simple geometric multiscale case, coupling two pipes with different dimensions. 
+---
+
+{% note %}
+Get the [case files of this tutorial](https://github.com/precice/tutorials/tree/master/partitioned-pipe-multiscale). Read how in the [tutorials introduction](https://www.precice.org/tutorials.html).
+{% endnote %}
+
+## Setup
+
+We exchange velocity data from the upstream 1D to the downstream 3D participant and for the pressure data vice versa. The config looks as follows:
+
+![Config visualization](images/tutorials-partitioned-pipe-multiscale-config.png)
+
+## How to run
+
+In two different terminals execute
+
+```bash
+cd fluid1d-python && ./run.sh
+```
+
+```bash
+cd fluid3d-openfoam && ./run.sh
+```
+
+## Results
+
+Visualizing the results in ParaView, we see an established laminar profile at the inlet of the 3D participant.
+
+![Expected result](images/tutorials-partitioned-pipe-multiscale-profile.png)

partitioned-pipe-multiscale/clean-tutorial.sh

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+#!/usr/bin/env sh
+set -e -u
+
+# shellcheck disable=SC1091
+. ../tools/cleaning-tools.sh
+
+clean_tutorial .
+clean_precice_logs .
+rm -fv ./*.log
+rm -fv ./*.vtu
+

partitioned-pipe-multiscale/fluid1d-python/Fluid1D.py

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+#!/usr/bin/env python3
+
+from nutils import mesh, function, solver, cli
+from nutils.expression_v2 import Namespace
+import numpy
+import treelog
+import matplotlib.pyplot as plt
+import precice
+
+
+def main(nelems: int, etype: str, degree: int, reynolds: float):
+    '''
+    1D channel flow problem.
+    .. arguments::
+       nelems [12]
+         Number of elements along edge.
+       etype [square]
+         Element type (square/triangle/mixed).
+       degree [2]
+         Polynomial degree for velocity; the pressure space is one degree less.
+       reynolds [1000]
+         Reynolds number, taking the domain size as characteristic length.
+    '''
+    # preCICE setup
+    participant_name = "Fluid1D"
+    config_file_name = "../precice-config.xml"
+    solver_process_index = 0
+    solver_process_size = 1
+    participant = precice.Participant(participant_name, config_file_name, solver_process_index, solver_process_size)
+    mesh_name = "Fluid1D-Mesh"
+    velocity_name = "Velocity"
+    pressure_name = "Pressure"
+    positions = numpy.zeros((1, 3))  # one vertex of three dimensions
+    vertex_ids = participant.set_mesh_vertices(mesh_name, positions)
+    participant.initialize()
+    precice_dt = participant.get_max_time_step_size()
+
+    # problem definition
+    domain, geom = mesh.rectilinear([numpy.linspace(0, 1, nelems + 1)])
+    ns = Namespace()
+    ns.δ = function.eye(domain.ndims)
+    ns.Σ = function.ones([domain.ndims])
+    ns.Re = reynolds
+    ns.x = geom
+    ns.define_for('x', gradient='∇', normal='n', jacobians=('dV', 'dS'))
+    ns.ubasis = domain.basis('std', degree=2).vector(domain.ndims)
+    ns.pbasis = domain.basis('std', degree=1)
+    ns.u = function.dotarg('u', ns.ubasis)
+    ns.p = function.dotarg('p', ns.pbasis)
+    ns.stress_ij = '(∇_j(u_i) + ∇_i(u_j)) / Re - p δ_ij'
+    ures = domain.integral('∇_j(ubasis_ni) stress_ij dV' @ ns, degree=4)
+    pres = domain.integral('pbasis_n ∇_k(u_k) dV' @ ns, degree=4)
+
+    while participant.is_coupling_ongoing():
+        # get dirichlet pressure outlet value from 3D solver
+        p_read = participant.read_data(mesh_name, pressure_name, vertex_ids, precice_dt)
+        # filter out unphysical negative pressure values
+        p_read = numpy.maximum(0, p_read)
+
+        usqr = domain.boundary['left'].integral('(u_0 - 1)^2 dS' @ ns, degree=2)
+        diricons = solver.optimize('u', usqr, droptol=1e-15)
+        ucons = diricons
+        stringintegral = '(p - ' + str(numpy.rint(p_read)) + ')^2 dS'
+        psqr = domain.boundary['right'].integral(stringintegral @ ns, degree=2)
+        pcons = solver.optimize('p', psqr, droptol=1e-15)
+        cons = dict(u=ucons, p=pcons)
+        with treelog.context('stokes'):
+            state0 = solver.solve_linear(('u', 'p'), (ures, pres), constrain=cons)
+            x, u, p = postprocess(domain, ns, precice_dt, **state0)
+
+        if participant.requires_writing_checkpoint():
+            u_iter = u
+            p_iter = p
+
+        write_vel = [[0, 0, u[-1][0]]]
+        # write new velocities to 3D solver
+        participant.write_data(mesh_name, velocity_name, vertex_ids, write_vel)
+        participant.advance(precice_dt)
+        precice_dt = participant.get_max_time_step_size()
+
+        if participant.requires_reading_checkpoint():
+            u = u_iter
+            p = p_iter
+
+    participant.finalize()
+    return state0
+
+
+def postprocess(domain, ns, dt, **arguments):
+
+    bezier = domain.sample('bezier', 9)
+    x, u, p = bezier.eval(['x_i', 'u_i', 'p'] @ ns, **arguments)
+
+    ax1 = plt.subplot(211)
+    ax1.plot(x, u)
+    ax1.set_title("velocity u")
+    ax2 = plt.subplot(212)
+    ax2.plot(x, p)
+    ax2.set_title("pressure p")
+    plt.savefig("./results/Fluid1D_" + str(dt) + ".png")
+    return x, u, p
+
+
+if __name__ == '__main__':
+    cli.run(main)

partitioned-pipe-multiscale/fluid1d-python/clean.sh

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+#!/usr/bin/env sh
+set -e -u
+
+. ../../tools/cleaning-tools.sh
+
+rm -f ./results/Fluid1D_*
+clean_precice_logs .
+clean_case_logs .

partitioned-pipe-multiscale/fluid1d-python/requirements.txt

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+setuptools # required by nutils
+nutils==7
+numpy >1, <2
+pyprecice~=3.0
+matplotlib

partitioned-pipe-multiscale/fluid1d-python/results/.gitignore

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+# Keep this directory, but ignore all files
+*

partitioned-pipe-multiscale/fluid1d-python/run.sh

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+#!/usr/bin/env bash
+set -e -u
+
+. ../../tools/log.sh
+exec > >(tee --append "$LOGFILE") 2>&1
+
+python3 -m venv .venv
+. .venv/bin/activate
+pip install -r requirements.txt && pip freeze > pip-installed-packages.log
+
+NUTILS_RICHOUTPUT=no python3 Fluid1D.py
+
+close_log

partitioned-pipe-multiscale/fluid3d-openfoam/0/U

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+FoamFile
+{
+    version     2.0;
+    format      ascii;
+    class       volVectorField;
+    location    "0";
+    object      U;
+}
+
+dimensions      [0 1 -1 0 0 0 0];
+
+internalField   uniform (0 0 0);
+
+boundaryField
+{
+    inlet
+    {
+        type            fixedValue;
+        value           $internalField;
+    }
+    outlet
+    {
+        type            fixedGradient;
+        gradient        uniform (0 0 0);
+    }
+    fixedWalls
+    {
+        type            noSlip;
+    }
+}

partitioned-pipe-multiscale/fluid3d-openfoam/0/p

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+FoamFile
+{
+    version     2.0;
+    format      ascii;
+    class       volScalarField;
+    object      p;
+}
+
+dimensions      [0 2 -2 0 0 0 0];
+
+internalField   uniform 0;
+
+boundaryField
+{
+    inlet
+    {
+        type            fixedGradient;
+        gradient        uniform 0;
+    }
+
+    outlet
+    {
+        type            fixedValue;
+        value           uniform 0;
+    }
+
+    fixedWalls
+    {
+        type            zeroGradient;
+    }
+}

partitioned-pipe-multiscale/fluid3d-openfoam/clean.sh

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+#!/usr/bin/env sh
+set -e -u
+
+. ../../tools/cleaning-tools.sh
+
+clean_openfoam .

partitioned-pipe-multiscale/fluid3d-openfoam/constant/transportProperties

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+FoamFile
+{
+    version     2.0;
+    format      ascii;
+    class       dictionary;
+    location    "constant";
+    object      transportProperties;
+}
+
+transportModel  Newtonian;
+
+nu              nu [ 0 2 -1 0 0 0 0 ] 10;

partitioned-pipe-multiscale/fluid3d-openfoam/constant/turbulenceProperties

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+FoamFile
+{
+    version     2.0;
+    format      ascii;
+    class       dictionary;
+    location    "constant";
+    object      turbulenceProperties;
+}
+
+simulationType laminar;

partitioned-pipe-multiscale/fluid3d-openfoam/run.sh

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+#!/usr/bin/env bash
+set -e -u
+
+. ../../tools/log.sh
+exec > >(tee --append "$LOGFILE") 2>&1
+
+blockMesh
+
+../../tools/run-openfoam.sh "$@"
+. ../../tools/openfoam-remove-empty-dirs.sh && openfoam_remove_empty_dirs
+
+close_log