5. Modify the physical model and grid
=====================================

Goal
----

Explore geometry, resolution, transport, or solver settings.

Configuration
-------------

The systems in this tutorial were generated using ``meshSize = 8e-6`` m,
``borderTol = 0``, and ``grainsTol = 0``. The inlet boundary was placed at the
top using ``inletLocation = "top"``.

Change one parameter at a time to evaluate its effect. For example, decrease
``meshSize`` for a finer mesh, adjust ``borderTol`` and ``grainsTol`` to
change the level of detail retained during border and grain extraction, or
change ``inletLocation`` to select another injection side.

The configuration reference includes images showing the effect of different
:ref:`meshSize values <mesh-size>` on the generated grid and different
:ref:`borderTol and grainsTol values <border-grains-tol>` on the extracted
borders and grain contours. Consult these examples before selecting values for
a new image.

Command
-------

.. code-block:: console

   pymm -i microsystem.png -p parameters.toml -t mesh_flow

How it works
------------

``mesh_flow`` rebuilds the image-derived mesh and then recomputes the steady
flow field. See the :doc:`configuration reference <../configuration_file>` for
accepted values, units, and illustrated parameter examples.

Result
------

Compare the new mesh and VTK data with the previous output directory. Use
``meshSize = 8e-6`` m, ``borderTol = 0``, and ``grainsTol = 0`` as the
baseline values. Inspect the generated mesh when changing ``meshSize`` and the
extracted border and grain contours when changing ``borderTol`` or
``grainsTol``.

Next
----

Continue with :doc:`combined`.