working on documenting particles

.. role:: cpp(code)

   :language: c++

.. _sec:particle-basics:

Particle Basics

===============

In MFiXi-Exa, particles are managed by the :cpp:`MFIXParticleContainer` class.

.. role:: cpp(code)

   :language: c++

.. _sec:particle-fluid:

Particle/Fluid Interactions

===========================

A standard :cpp:`mfix_level::Evolve` step looks like this (for brevity, we are

omitting some details here):

.. highlight:: c++

::

    // Calculate particle volume fraction:

    mfix_calc_volume_fraction(lev, sum_vol)

    // Eolve fluid

    if ( use_proj_method )

        EvolveFluidProjection(lev, nstep, dt, ...)

    else

        EvolveFluidSimple(lev, nstep, dt, ...)

    // Apply fluid drag force on particles

    mfix_calc_drag_particle(lev)

    // Move particles (using forces acting on particles)

    pc -> EvolveParticles(lev, nstep, dt ...)

Here, ``lev`` represents the AMR level, and ``pc`` is a pointer to a

:cpp:`MFIXParticleContainer` instance.

Particle/Wall Interactions

==========================

Particles

=========

MFiX-Exa supports solid particles which are immersed in the fluid. In the

future particles can be implemented using the immersed-boundary method (and

hence these IBM-particles can support non-spherical shapes, and special

hydrodynamical and chemical interactions). But for now, particles are

spherical, with approximate fluid-particle interactions. The main consequence

of this approximation is that particles should not be bigger than the fluid

grid resolution.

Particles interact with container walls (implemented using AMReX's

Embedded-Boundary functionality) using a level-set constructed from the signed

closest distance function at the beginning of the simulation.

Refer to the subsequent sections for details on the implementation of the

particle-particle, particle-fluid, and particle-wall interactions.

.. toctree::

   :maxdepth: 1

   :caption: Contents:

   ParticleBasics

   ParticleFuild

   ParticleWalls