.. _legacy_volume_mesher_user_guide:

********************
Legacy Volume Mesher
********************

The legacy volume mesher is the original volume meshing algorithm in Flow360. In the Python API it still runs by default for projects that start from geometry, unless ``use_beta_mesher=True`` or ``use_geometry_AI=True`` is passed. The :ref:`Volume Mesher <new_volume_mesher_user_guide>` is recommended instead. See :ref:`meshing` for details.

Main characteristics:

- uses an unstructured tetrahedral mesh in the farfield region,
- supports spherical and half-spherical farfield configurations,
- allows for the generation of quasi-3D meshes for 2D simulations.

Available features:

- Boundary layers:

  - first layer thickness specification,
  - growth rate control,
  - automatic layer count calculation based on target wall spacing.

- Refinements:

  - uniform volumetric refinements specified using cylinders or boxes,
  - axisymmetric volumetric refinements specified using cylinders.

- Zones:

  - rotating volume zones for simulating rotating machinery,
  - automatic farfield zone generation.

- Farfield:

  - spherical farfield generation with configurable radius,
  - half-sphere farfield for symmetric configurations.

- Quasi-3D meshing:

  - automatic handling of quasi-3D geometries,
  - boundary condition setup for quasi-3D simulations.

Examples
========

Examples of mesh generation can be found in the :ref:`Python API Example Library <python_api_example_library>`:

- :doc:`2D CRM airfoil example <../../python_api/example_library/notebooks/2D_CRM_airfoil>`,
- :doc:`DARPA AD example <../../python_api/example_library/notebooks/DARPA_SUBOFF_AD>`.

And in the `WebUI Example Library <https://flow360.simulation.cloud/examples>`_.:

- `Simple airplane example <https://flow360.simulation.cloud/workbench/prj-261fdfa7-025e-40d7-9c5d-52c0f206f782>`_,
- `eVTOL with BET line example <https://flow360.simulation.cloud/workbench/prj-207be482-26c0-4211-9834-753ae5ff3149>`_,
- `Isolated propeller example <https://flow360.simulation.cloud/workbench/prj-a0dd6591-7f9e-4436-a676-a9b80d68d103>`_.


.. _fig_legacy_volume_mesher_example:
.. figure:: Figures/legacy_vm_example.png
    :align: center
    :width: 70%

    Clip of an example mesh generated using the **Legacy Volume Mesher**.