Particle-Based Boundary Conditions

Introduction

Particle-based boundary conditions are used to apply conditions directly to particles for loads, tractions, heat fluxes, and concentration fluxes. Particle-based boundary conditions are typically applied to particles on the boundary of the object. Some particle-based boundary conditions instead set initial some particle properties (e.g., damage). Besides particle conditions, simulations can set Grid-Based Boundary Conditions.

Particle-Based Boundary Condition Commands

In scripted files, all particle-based boundary conditions are created by a series of ParticleBC command blocks that select particles:

ParticleBC
  (one 2D or 3D shape command, which can be nested)
  (one or more load, traction, heat flux, or concentration flux condition)
    ...
EndParticleBC

In XML files, particle-based boundary conditions are created with a <BCShape> block

<BCShape>
  (one 2D or 3D shape command, which can be nested)
  (one or more load, traction, heat flux, or concentration flux condition)
    ...
</BCShape>

which must be within the main <ParticleBC> block.

The particles that will get boundary conditions are selected by defining one 2D shape (for 2D simulations) or one 3D shape (for 3D simulations). The shape can be a nested shape.

All particles within the one shape will be set to all provided conditions (load, traction, heat, concentration, pore pressure flux, and/or initial damage or phase field).

Deprecated Commands

Prior to the particle-based boundary condition commands in the previous section, the boundary conditions used to be set with boundary condition shape commands. The deprecated commands are:

• LoadLine and <BCLine>
• LoadArc and <BCArc>
• LoadRect and <LdRect>
• LoadBox and <BCBox>

See documentation for conversion of old commands to the new method.

Explicit Particle-Based Boundary Condition in XML Files

An option in XML files is to explicitly set boundary conditions on particles without using shape functions. The format is

<GridBCs>
   (one or more <BCShape> blocks)
   ...
   <LoadBCs>
      (one or more explicit boundary conditions)
   </LoadBCs>
</GridBCs>

The <BCShape> blocks set boundary conditions as explained above. The <LoadBCs> block lets you explicitly list each particle. The explicit method is limited to load conditions, and is usually generated with other software. You can use both <BCShape> blocks and a <LoadBCs> block in the same input file.