.. DO NOT EDIT.
.. THIS FILE WAS AUTOMATICALLY GENERATED BY SPHINX-GALLERY.
.. TO MAKE CHANGES, EDIT THE SOURCE PYTHON FILE:
.. "auto_how_to/example_volume_integral.py"
.. LINE NUMBERS ARE GIVEN BELOW.

.. only:: html

    .. note::
        :class: sphx-glr-download-link-note

        :ref:`Go to the end <sphx_glr_download_auto_how_to_example_volume_integral.py>`
        to download the full example code.

.. rst-class:: sphx-glr-example-title

.. _sphx_glr_auto_how_to_example_volume_integral.py:


Compute a volume integral
=========================

``VolIntegrate`` is the canonical reducer for volume fields: it multiplies
by cell volume and sums. Use it whenever "how much" is the question —
total mass, total energy, integrated source term.

We compute the total water volume in the ``damBreak`` case at t=0.

.. GENERATED FROM PYTHON SOURCE LINES 13-15

Open the case
-------------

.. GENERATED FROM PYTHON SOURCE LINES 15-38

.. code-block:: Python


    import os
    import subprocess

    import pyOFTools.patch_pybfoam  # noqa: F401
    from pyOFTools import clone_example

    CASE = clone_example("damBreak")
    subprocess.run(
        ["./Allrun"],
        cwd=CASE,
        check=True,
        env={**os.environ},
        capture_output=True,
        text=True,
    )

    from pybFoam import Time, fvMesh, volScalarField

    time = Time(str(CASE.parent), CASE.name)
    mesh = fvMesh(time)
    volScalarField.read_field(mesh, "alpha.water")





.. rst-class:: sphx-glr-script-out

 .. code-block:: none


    <pybFoam.pybFoam_core.volScalarField object at 0x7f46cb50b910>



.. GENERATED FROM PYTHON SOURCE LINES 39-43

Integrate
---------
``field | VolIntegrate`` — read as "wrap the field, integrate it by
cell volumes". The result is an ``AggregatedDataSet`` with one value.

.. GENERATED FROM PYTHON SOURCE LINES 43-51

.. code-block:: Python


    from pyOFTools.aggregators import VolIntegrate
    from pyOFTools.builders import field

    result = (field(mesh, "alpha.water") | VolIntegrate()).compute()
    total_water_volume = result.values[0].value
    print(f"total water volume at t=0: {total_water_volume:.6g} m^3")





.. rst-class:: sphx-glr-script-out

 .. code-block:: none

    total water volume at t=0: 0.000840422 m^3




.. GENERATED FROM PYTHON SOURCE LINES 52-58

Write it to a CSV
-----------------
For a standalone script, the raw value is usually enough. But if you are
going to wire this into ``@postProcess.Table`` later (see
:doc:`/how-to/configure_controlDict`), it is useful to know that the CSV
row you get is exactly what ``AggregatedDataSet.grouped_values`` returns.

.. GENERATED FROM PYTHON SOURCE LINES 58-61

.. code-block:: Python


    print("headers:", result.headers)
    print("rows:   ", result.grouped_values)




.. rst-class:: sphx-glr-script-out

 .. code-block:: none

    headers: ['alpha.water_volIntegrate']
    rows:    [[0.0008404216050726664]]





.. rst-class:: sphx-glr-timing

   **Total running time of the script:** (0 minutes 10.581 seconds)


.. _sphx_glr_download_auto_how_to_example_volume_integral.py:

.. only:: html

  .. container:: sphx-glr-footer sphx-glr-footer-example

    .. container:: sphx-glr-download sphx-glr-download-jupyter

      :download:`Download Jupyter notebook: example_volume_integral.ipynb <example_volume_integral.ipynb>`

    .. container:: sphx-glr-download sphx-glr-download-python

      :download:`Download Python source code: example_volume_integral.py <example_volume_integral.py>`

    .. container:: sphx-glr-download sphx-glr-download-zip

      :download:`Download zipped: example_volume_integral.zip <example_volume_integral.zip>`


.. only:: html

 .. rst-class:: sphx-glr-signature

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