surface model convexhull/manifold

Purpose

Modelling surface of convex/concave particles. The command is not required by the Aspherix® natural language style.

Syntax

surface convexhull/manifold

Description

This model is used in the framework of convex/concave particle simulations; for more information see also the CONVEX guide. The command is not required by the Aspherix® natural language style, as it is invoked automatically by the commands particle_shape convex or concave.

The convexhull/manifold algorithm works by constructing an incremental manifold of at most four contact points. Each step one contact point (as above) is added using the MPR algorithm. Previous contact points will remain as long as they are still in the intersection. Using contact point reduction at most four of those points are chosen to represent the manifold. These four points are then averaged to determine the “real” contact point. This ensures additional stability when two flat faces are in contact.

This surface model looks for a global scalar with name wall_extrusion_percentage which allows to determine the wall thickness. Normally a wall is extruded in each normal direction by 2% of the bounding radius of a convex particle in order to give it a volume. The wall_extrusion_percentage scalar can be used to set a different value. If you change this value make sure it is large enough that the polyhedral particles do not pass through the wall as then the contact detection can fail.

Restrictions

Requires particle_shape convex or concave.

These surface models do not allow the use of primitive walls.

Coarse-graining information:

Using coarsegraining in combination with this command might lead to statistically different dynamics and system state. To the best knowledge of the developers, the cross-influence between this command and coarse-graining is unknown.

Default: none