The Particle Tracing Module allows us to calculate the trajectory of particles in a fluid, including all interactions (particle-particle and fluid-particle). The interaction between particles and fields is bidirectional. It is possible to combine any physical interface with particle tracing to calculate the fields that drive particle motion. The motion is described by the Newtonian, Lagrangian or Hamiltonian formulations of classical mechanics, and there are multiple boundary conditions on the walls of the geometry to allow particles to freeze, stick, bounce, disappear or diffusely reflect.

We can also include the generation of secondary particles released when an incoming particle hits a wall, and add additional dependent variables to the model to calculate quantities such as particle mass, particle temperature or spin. A wide range of predefined forces are available to describe specifically how particles interact with fields, and it is possible to add arbitrary forces by their mathematical expression.

This course develops the theoretical foundations of particle tracing, always from the point of view of its implementation in the main COMSOL Multiphysics platform. We will describe in detail the physical interfaces of particle tracing and their multiphysics couplings, including all possible bidirectional interactions.