Defining a Particle Boundary

You can describe how an inlet or outlet behaves in a Lagrangian particle flow simulation.

You can specify that a boundary is a location where particles leave the simulation, a location where they are reflected, or a mixed location where some particles leave and some are reflected.

This task shows you how to:

Before you begin: Enable particle modeling in the fluid physics.
See Also
About Lagrangian Particle Boundaries

Define a Reflection Boundary for Particles

You can specify that an inlet or an outlet is also a location where particles reflect back into the fluid region.

  1. Edit the boundary for which you want to define Lagrangian particle behavior.
  2. From the Particle boundary options, select Reflection .
  3. Specify the Coefficient of restitution, which is the ratio of the velocity before a particle impacts the boundary to its velocity after impact. A value of 1 describes a completely elastic reflection. You define the coefficient of restitution in the normal and tangential directions.

Define a Termination Boundary for Particles

You can define a termination behavior for a boundary, which means that particles leave the fluid region through the boundary.

  1. Edit the boundary for which you want to define Lagrangian particle behavior.
  2. From the Particle boundary options, select Termination.

Define a Boundary with Mixed Particle Behavior

You can define mixed particle behavior for a boundary, which means that some particles leave the fluid region through the boundary and others reflect off the boundary. The proportion of reflection and termination at mixed boundaries depends on the adhesion model you specify.

  1. Edit the boundary for which you want to define Lagrangian particle behavior.
  2. From the Particle boundary options, select Mixed.
  3. From the Mixed options, specify how you want to define the fraction of particles that the boundary reflects back to the fluid region:
    OptionDescription
    Constant Defines a fraction of particles reflected that is constant throughout the simulation.
    Deposition Defines reflection based on the properties of the surface and the particles.
  4. If you are defining a constant fraction of reflected particles, enter a value between 0 and 1 in the Fraction of reflection field.
  5. If you are defining a fraction of reflected particles that depends on surface properties, enter the Young's modulus and Poisson's ratio for the material of the boundary.

    If the particles have mass, their Young's modulus and Poisson's ratio is specified in the fluid physics.

  6. Specify the Coefficient of restitution for the reflected particles, which is the ratio of the velocity before a particle impacts the boundary to its velocity after impact. A value of 1 describes a completely elastic reflection. You define the coefficient of restitution in the normal and tangential directions.