Cyclone: DPM

Cyclone by DPM, ANSYS Fluent CFD Simulation Training

Description

This project simulates a cyclone separator using the Discrete Phase Model (DPM) in ANSYS Fluent. Cyclones are among the most widely used industrial systems for air dewatering, dust disposal, and separating solid particles from gas flow, relying purely on centrifugal and gravitational forces to achieve separation — without the need for filters. Beyond reducing air pollution, cyclones also serve to reclaim solid particles back into the production cycle, and are commonly used in industries such as wood processing and cement production where suspended solid particles are a byproduct.

Cyclones typically feature one inlet and two outlets: particle-laden air enters through the inlet and travels in a spiral, vortex-like pattern through the space between the inner and outer cylindrical bodies, keeping the solid particles suspended within the flow. Centrifugal force, combined with the particles' greater mass, drives them outward and eventually downward under gravity, separating them from the gas stream — while the cleaner gas flow continues upward, passing through the conical region before exiting through the upper outlet.

Geometry & Mesh

The 3D geometry was designed in Design Modeler, consisting of a cylindrical upper section transitioning into a partially conical lower section. A trapezoidal cross-section at the top serves as the dust-laden air inlet, with a circular cross-section forming the pure air outlet above it, while a circular cross-section at the bottom collects the separated dust particles. The domain was meshed in ANSYS Meshing using an unstructured grid totaling 142,499 elements.

Methodology

Gas flow continuously enters from the top into the space between the two cylinders and subsequently the conical section, while solid particles enter simultaneously as the discrete phase. The interaction between these two flows, combined with centrifugal force, drives their separation. In this simulation, air was defined as the continuous gas flow, with ash modeled as the discrete solid particle phase.

This setup examines discrete-phase behavior from a Lagrangian perspective within a continuous Eulerian fluid — the gas flow is treated under the Eulerian framework, while the ash particles are tracked discretely under the Lagrangian framework. Since the continuous phase was assumed not to be affected by the discrete phase, the Interaction with Continuous Phase option was disabled for the DPM setup. The discrete phase injection was defined as inert at the cyclone inlet, meaning the particles exhibit no specific reactive behavior, allowing their trajectories and residence time to be tracked cleanly for performance analysis.

Conclusion

By tracking the ash particles' trajectories and residence time throughout the cyclone, this simulation enables direct evaluation of separator performance — confirming how effectively the combined centrifugal and gravitational forces separate solid particles from the gas stream as they travel through the cyclone's cylindrical and conical geometry, consistent with the expected operating principle of this widely used industrial separation device.