For all of the particle tracing physics interfaces, the particle trajectories must be computed using a Time-Dependent Solver. For single-physics particle tracing, this can be set up by using the
Time Dependent study.
If the particles do significantly perturb the fields in the surrounding domains, it is necessary to create a bidirectional coupling. The most straightforward way to set up a bidirectional coupling is by using one of the Multiphysics Couplings. Alternatively, if the necessary physics interfaces are already present, it is possible to manually add the contributions from the particles to the surrounding fields. For example, if instances of the Charged Particle Tracing and Electrostatics interfaces are present, the contribution of the charged particles to the space charge density can be included by adding the
Electric Particle Field Interaction Multiphysics node.
If the fields are stationary, it is possible to significantly reduce the computational cost of the model by using an iterative solver loop in which the particle trajectories are computed using a Time-Dependent solver and the fields are computed using a
Stationary solver. To obtain a self-consistent solution, it is necessary to ensure that the result from each of these solvers is used to set the value of variables not solved for by the other solver. The
For and
End For nodes, when added to a solver sequence, can be used to set up an iterative loop that does the following:
The Bidirectionally Coupled Particle Tracing study step automatically sets up an iterative solver loop, and can be used in place of a
Time Dependent study to facilitate the calculation of bidirectionally coupled particle trajectories and fields.
When solving for the fields using a Stationary study, it is possible to considerably reduce the number of particles in the simulation by selecting
Specify current or
Specify mass flow rate from the
Particle release specification list in the physics interface
Particle Release and Propagation section. This causes each model particle to represent a number of real particles per unit time, all moving along the same path, and therefore it is only necessary to release particles during the first time step.