In many industries like food and cement, factories need to clean dust out of the air. They use a machine called a Cyclone Separator. This machine does not have moving parts. Instead, it uses a fast-spinning wind (vortex) to throw heavy dust particles against the wall. To study this complex process, engineers use computer simulation. We combine two methods: CFD (for air) and DEM (for particles).

This project is a Particles in Cyclone Separator CFD DEM simulation designed to teach you how to model this system. We use ANSYS Fluent to simulate the air and ANSYS ROCKY to simulate the solid particles. This combination, called Cyclone DEM CFD, allows us to track every single piece of dust. For more learning resources on particle simulation, please visit our DEM tutorials. Our simulation follows the methods used in the research paper by Zhou et al. [1].

• Reference [1]: Zhou, Haili, et al. “Numerical study on gas-solid flow characteristics of ultra-light particles in a cyclone separator.” Powder technology344 (2019): 784-796.
• Reference [2]: Hoekstra, A. J., J. J. Derksen, and H. E. A. Van Den Akker. “An experimental and numerical study of turbulent swirling flow in gas cyclones.” Chemical engineering science13-14 (1999): 2055-2065.
• Reference [3]: Wang, B., et al. “Numerical study of gas–solid flow in a cyclone separator.” Applied Mathematical Modelling11 (2006): 1326-1342.

Figure 1: The 3D geometry of the Cyclone Separator with 8 parts. [1]

Simulation Process: Coupling ANSYS Fluent and Rocky DEM

To start this Cyclone Separator DEM ROCKY tutorial, we first built the 3D model. The geometry has a special tangential inlet. This means the air enters from the side, not the top. This shape forces the air to spin. We divided the model into 8 parts to make a structured mesh. A structured mesh uses neat, box-shaped cells. This is very important for accuracy.

In the ANSYS Fluent setup, we focused on the airflow. Because the air spins very fast and is very chaotic, simple turbulence models do not work. We selected the Reynolds Stress Model (RSM). This is the best model for Cyclone DEM ROCKY studies because it can calculate the strong twisting forces correctly. After Fluent solved the airflow, we sent the data to ANSYS ROCKY. In Rocky, we created the particles and injected them into the cyclone. This is called One-Way Coupling. Fluent tells Rocky where the wind is blowing, and Rocky calculates where the particles fly.

Post-processing: Analysis of Vortex Speed and Particle Separation

A deep and substantiated analysis of the Particles in Cyclone Separator CFD DEM simulation shows exactly how the physics of the machine works. We must first look at the airflow data from Fluent. The streamlines in Figure 2 show a double vortex structure. The air enters the side and immediately spins down the walls. The data shows this Outer Vortex is extremely fast, reaching speeds of up to 47 m/s. This high speed is critical. It creates a strong “centrifugal force” that pushes everything outward. As the air hits the bottom of the cone, it cannot go any further. It reverses direction and spins upwards in the center. The data shows this Inner Vortex moves up at a speed of about 23 m/s.

Figure 2: Streamlines of gas flow showing high-speed outer vortex.

The ANSYS ROCKY results in Figure 3 explain how these two wind speeds separate the particles. We can see particles colored by mass. The heavy particles, like the one labeled 3.29e-7 kg, are affected mostly by the Outer Vortex. Because they are heavy, they have high inertia. The centrifugal force from the 47 m/s wind throws them hard against the wall. Once they hit the wall, they lose energy and slide down to the bottom collection bin. This is how the “cleaning” happens.

However, the physics is different for very light particles. The simulation shows that lighter dust does not have enough mass to reach the wall. Instead, the “Drag Force” from the air is stronger than the centrifugal force. These light particles get caught in the Inner Vortex. Since this inner wind is moving up at 23 m/s, it carries the light particles out of the top of the cyclone. This clear difference in path—heavy down, light up—proves that our Cyclone Separator DEM ANSYS fluent setup is working correctly. The simulation successfully visualized the competition between the centrifugal force (pushing out) and the drag force (pulling up), which is the main principle of cyclone separation.

Figure 3: Particle trajectories colored by mass showing heavy particles falling and light particles rising.

Key Takeaways & FAQ

• Q: Why use the Reynolds Stress Model (RSM)?
  • A: In a Cyclone DEM CFD study, the airflow spins violently (anisotropic flow). Simple models cannot predict this. RSM is the only model in ANSYS Fluent that is accurate enough for strong swirling flows.
• Q: What is the role of the 47 m/s outer vortex?
  • A: The high speed of 47 m/s creates the centrifugal force. This force is what pushes the heavy particles (3.29e-7 kg) to the wall so they can be collected.
• Q: Why do we use ANSYS ROCKY?
  • A: ANSYS ROCKY is a DEM software. It is better than standard CFD for tracking solid particles because it calculates the collisions between particles and the wall very accurately.