Create: Particles

Particles are discrete objects with individual trajectories governed by Newton’s second law. Each particle is characterized by a set of kinematic properties (position, velocity, acceleration, etc.) and physical properties (density, size, composition, etc.). Particle motion follows a Lagrangian specification (unlike fluid motion which uses the Eulerian concept of a field/lattice). As such, particles can assume arbitrary positions and velocities across the simulation domain as they evolve through space and time.

Particles are organized into particle families using a parent-child relationship. The parent defines the shared physical and modeling properties of the family, such as particle density, forces, breakup and coalescence behavior, and scalar coupling. Child objects within the family then specify additional functionality, such as particle injections for introducing particles into the system, particle scalars for tracking particle-specific quantities, and particle reactions for modeling intraparticle transformations.

In addition to scalar coupling, particle variables are defined on individual particles rather than on lattice sites. Unlike voxel variables, they move with each particle and are updated along its trajectory. Particles can also exchange mass with surrounding scalar fields, enabling processes such as dissolution and gas transfer.

Particle Types

  • Massless Tracers: Massless tracer particles have no inertia, follow the fluid streamlines, and are one-way coupled to the fluid. They are useful for visualizing flow and predicting residence times.

  • Inertial Particles: Inertial particles have a specified density and diameter. They are useful for modeling solid particle suspension, particle settling, liquid-liquid dispersions, and liquid-particle reactions.

  • DEM Particles: DEM or discrete element particles extend the functionality of inertial particles to include particle-particle contact mechanics. They are useful for modeling slurries, granular flows, and particle packing problems.

  • Liquid Droplets: Liquid droplets are used to model immiscible two fluid–dispersion processes. These droplets can be two-way coupled to the fluid and support particle-particle interactions.

  • Gas Bubbles: Gas bubbles are low-density inertial particles which support breakup, coalescense, and interfacial gas-liquid mass transfer. They are used to model sparged gas systems and air lift reactors; they also predict gas holdup and gas drawdown processes via Lagrangian-Eularian coupling.

Adding Particles

Particle Dynamics

Particle Variables and Reactions

  • Particle Variables: User-defined quantities assigned to individual particles, allowing you to track properties that move and evolve with each particle rather than being fixed to the grid.

  • Particle Scalars: Particle scalars represent species concentrations contained within individual particles, moving with each particle as it travels through the domain. They evolve through intra-particle reactions

  • Particle Reactions: Particle reactions define intra-particle reaction kinetics, allowing species concentrations and other particle properties to evolve over time based on local conditions and particle state.

Particle Output

  • Particle Output Data: Particle Output Data provides comprehensive outputs for analyzing particle behavior, statistics, spatial fields, and exit dynamics throughout a simulation.

Particle Theory