Ansys Fluent – Dense Discrete Phase Model (DDPM)

The standard Discrete Phase Model tracks particles as points through the fluid and assumes they are dilute enough to ignore the volume they occupy. That assumption breaks as soon as the particles crowd together, which is exactly what happens in fluidised beds, cyclones with heavy loading, or slurry transport.

The Dense Discrete Phase Model removes that limitation. It accounts for the volume fraction occupied by the particles, so the fluid sees them as an obstruction and the two phases exchange momentum in both directions. Particle collisions can also be included through a granular model rather than being ignored.

The price is computational. You are tracking a large number of parcels while solving the continuous phase, so the setup rewards planning: choose the injection carefully, keep the parcel count reasonable, and check the mass balance before trusting anything else.