Lagrangian Multiphase (LMP)
A wide variety of flow processes involve the transport of solid particles, liquid droplets, or gas bubbles—known as dispersed phases—by a gaseous or liquid continuous phase.
Examples include:
- Cyclone dust separators
- Vehicle soiling
- Spray coating
- Aerosol dispersion
- Spray cooling
- Liquid fuel combustion
The generic term particle is used in Simcenter STAR-CCM+ to describe solid particles, liquid droplets, gas bubbles and massless (virtual) particles. If interactions of particles with the continuous phase, rather that with each other, dominate their motion, the dispersed phases are dilute. The Lagrangian Multiphase model is designed for such flows.
The physics continuum represents the continuous phase whose governing equations are expressed in Eulerian form. The Lagrangian Multiphase model permits solving an arbitrary number of dispersed phases, each modeled in a Lagrangian framework.
In a Lagrangian framework [655], particle-like elements that are known as parcels are followed through the continuum. The state of each parcel is updated according to a selected set of models and can be optionally recorded as a track. Dispersed phases modeled using the Lagrangian Multiphase model are known as Lagrangian Phases.
In the same way as models are selected for physics continua, the models that are provided to predict the state of each parcel can be selected per phase. Either (real) material particles or (virtual) massless particles can be modeled. Material models are available to represent single-component gases, single-, or multi-component liquids and single-component solids, together with constant density or polynomial density equations of state. The momentum conservation equation governs the flow of material particles and can optionally include drag, virtual mass, and user-defined forces. Similarly, an energy conservation equation can be solved, including convective heat transfer and an optional user-defined energy source. Specific models for droplets in a gaseous medium (“sprays”) include a mass conservation equation to account for the change in droplet mass from evaporation or condensation. They also include models for primary atomization and secondary breakup.
Boundary conditions define the interaction between particles and boundaries. Particle behavior at impermeable boundaries, in particular, requires modeling. You can control this behavior, depending on the active models. Particles can optionally be considered to cause erosion at these boundaries.
Injectors define the initial conditions of each particle, namely how and where they are introduced into the simulation.
In general, the state of the continuous phase influences the state of the dispersed phases. Two-way coupling can therefore be applicable, in which the state of the continuous phase depends on the dispersed phases, through inter-phase mass, momentum, and energy transfer effects.
If the flow of the continuous phase is laminar, a parcel that is released from a point at a given instant follows a smooth unique trajectory, that is, the motion is deterministic. On the other hand, parcels that are introduced into a turbulent carrier flow each have their own random path due to interaction with the fluctuating turbulent velocity field. A turbulent dispersion model is provided to account for this phenomenon.