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Collision Operators
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The collision operators adopted in the current solver are all based on BGK collision operator. While the original BGK collision operator lacks stability at values of :math:`\tau` close to 0.5, it is possible to compensate this weakness by following some strategies that result in the recursive regularized-BGK (RR-BGK) collision operator. First it is important to highlight that populations can be written in terms of its equilibrium and non-equilibrium portions as :math:`f_{i}=f_{i}^{\mathrm{eq}}+f_{i}^{\mathrm{neq}}`.

.. note::
    The following development brings certain complexity and might require knowledge of some specific topics to its fully understanding.

.. include:: rrbgk.rst.inc

.. include:: hrrbgk.rst.inc

.. toctree::
   :maxdepth: 1
   :hidden:

   Moments collision <collision.moments.rst>

.. footbibliography::