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

.. only:: html

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

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

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

.. _sphx_glr_auto_examples_ftle_plot_dg_ftle.py:


Double gyre FTLE
================

Compute the FTLE field for the double gyre.

.. GENERATED FROM PYTHON SOURCE LINES 9-18

.. code-block:: Python


    # Author: ajarvis

    import numpy as np
    from math import copysign
    import matplotlib.pyplot as plt
    from numbacs.flows import get_predefined_flow
    from numbacs.integration import flowmap_grid_2D
    from numbacs.diagnostics import ftle_grid_2D







.. GENERATED FROM PYTHON SOURCE LINES 19-22

Get flow
--------------
Set the integration span and direction, retrieve the flow, and set up domain.

.. GENERATED FROM PYTHON SOURCE LINES 22-38

.. code-block:: Python


    # set initial time, integration time, and integration direction
    t0 = 0.0
    T = -10.0
    int_direction = copysign(1, T)

    # retrieve function pointer, parameters, and domain for double gyre flow.
    funcptr, params, domain = get_predefined_flow("double_gyre", int_direction=int_direction)

    # set up domain
    nx, ny = 401, 201
    x = np.linspace(domain[0][0], domain[0][1], nx)
    y = np.linspace(domain[1][0], domain[1][1], ny)
    dx = x[1] - x[0]
    dy = y[1] - y[0]








.. GENERATED FROM PYTHON SOURCE LINES 39-42

Integrate
---------
Integrate grid of particles and return final positions.

.. GENERATED FROM PYTHON SOURCE LINES 42-44

.. code-block:: Python

    flowmap = flowmap_grid_2D(funcptr, t0, T, x, y, params)








.. GENERATED FROM PYTHON SOURCE LINES 45-48

FTLE
----
Compute FTLE field from final particle positions.

.. GENERATED FROM PYTHON SOURCE LINES 48-50

.. code-block:: Python

    ftle = ftle_grid_2D(flowmap, T, dx, dy)








.. GENERATED FROM PYTHON SOURCE LINES 51-54

Plot
----
Plot the results.

.. GENERATED FROM PYTHON SOURCE LINES 54-58

.. code-block:: Python

    fig, ax = plt.subplots(dpi=200)
    ax.contourf(x, y, ftle.T, levels=80)
    ax.set_aspect("equal")
    plt.show()



.. image-sg:: /auto_examples/ftle/images/sphx_glr_plot_dg_ftle_001.png
   :alt: plot dg ftle
   :srcset: /auto_examples/ftle/images/sphx_glr_plot_dg_ftle_001.png
   :class: sphx-glr-single-img






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

   **Total running time of the script:** (0 minutes 0.745 seconds)


.. _sphx_glr_download_auto_examples_ftle_plot_dg_ftle.py:

.. only:: html

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

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

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

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

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

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

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


.. only:: html

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

    `Gallery generated by Sphinx-Gallery <https://sphinx-gallery.github.io>`_