58 lines
1.9 KiB
ReStructuredText
58 lines
1.9 KiB
ReStructuredText
Granular models
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===============
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Granular system are composed of spherical particles with a diameter,
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as opposed to point particles. This means they have an angular
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velocity and torque can be imparted to them to cause them to rotate.
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To run a simulation of a granular model, you will want to use
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the following commands:
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* :doc:`atom_style sphere <atom_style>`
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* :doc:`fix nve/sphere <fix_nve_sphere>`
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* :doc:`fix gravity <fix_gravity>`
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This compute
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* :doc:`compute erotate/sphere <compute_erotate_sphere>`
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calculates rotational kinetic energy which can be :doc:`output with thermodynamic info <Howto_output>`.
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The compute
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* :doc:`compute fabric <compute_fabric>`
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calculates various versions of the fabric tensor for granular and non-granular pair styles.
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Use one of these 4 pair potentials, which compute forces and torques
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between interacting pairs of particles:
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* :doc:`pair_style gran/history <pair_gran>`
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* :doc:`pair_style gran/no_history <pair_gran>`
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* :doc:`pair_style gran/hertzian <pair_gran>`
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* :doc:`pair_style granular <pair_granular>`
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These commands implement fix options specific to granular systems:
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* :doc:`fix freeze <fix_freeze>`
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* :doc:`fix pour <fix_pour>`
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* :doc:`fix viscous <fix_viscous>`
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* :doc:`fix wall/gran <fix_wall_gran>`
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* :doc:`fix wall/gran/region <fix_wall_gran_region>`
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The fix style *freeze* zeroes both the force and torque of frozen
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atoms, and should be used for granular system instead of the fix style
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*setforce*\ .
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For computational efficiency, you can eliminate needless pairwise
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computations between frozen atoms by using this command:
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* :doc:`neigh_modify <neigh_modify>` exclude
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.. note::
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By default, for 2d systems, granular particles are still modeled
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as 3d spheres, not 2d discs (circles), meaning their moment of inertia
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will be the same as in 3d. If you wish to model granular particles in
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2d as 2d discs, see the note on this topic on the :doc:`Howto 2d <Howto_2d>`
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doc page, where 2d simulations are discussed.
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