I am a big fan of Dyson’s vacuum cleaner. So I tried to check how particles separated in the flow with the help of the cyclone.

First, I made a simple 3D model of a cyclone separator. The dirty air with particles will go in the inlet in the right upper side. With the help of the shape of the cyclone body, the flow will rotate inside the cyclone body and conical section. However, the particles collide with wall of the cyclone body and that collision will make particle lose its kinetic energy. The particles will drop down to the lower side (or a particle collection chamber). Then cleaner air without particles will go out through the outlet. The principle looks very simple.  but I believe that the inventor should be a genius or a man of inspiration.


OK. My CFD tool is comsol. I put the related file this page to help you try it by yourself.

20140501_cyclone_model : Solidworks model

20140501_cyclone_comsol_small : Comsol file

This is the simple procedure to accomplish the calculation.

  1.  Define the geometry and materials. The fluid used in this calculation is Air.
  2.  In the Laminar flow section, define the inlet and outlet conditions. U_inlet = 1 [m/sec], P_outlet = 0 [Pa]
  3. In the Particle tracing section, define the particle properties such as density and diameter.
  4. There are two main forces that acts on the particle. The first one is the drag force that makes particles move with flow. The second one is the gravity force that make particles drop down when particles lose its kinetic energy. So you can define these two forces in the setting menu carefully.
  5. Build  Mesh and Calculate. You can increase the accuracy by increasing the number of mesh. but it will increase the calculation time dramatically in this case.

Here is the calculation results. 1st figure shows velocity magnitude of the fluid. 2nd figure shows the velocity filed of the fluid. 3rd figure shows the particle trajectories.

velocity_magnitude velocity_field particle_field

Finally, I put the animation and see how the cyclone separate the particles and makes clean air.

Thanks for your time.


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  1. Thank you very much for your model.
    Would you mind telling me what version of COMSOL you used??
    Btw, there is a misspelling in your first category – says: Evaulation, should say: Evaluation.

    1. Hello. Luis.
      Thanks for showing your interests. The comsol version is 5.1.
      I will update the model with turbulent module soon.

      P.S. Thanks for saying to me about the misspelling. I fixed it. 🙂

  2. Hello,

    nice model. I have downloaded from your site the Comsol model. I run the simulaton but couldn’t see any particle trajectories. I use Comsol 5.2a.

    1. me too

  3. Hello, Barbara, Thanks for your message. I checked my comsol file but I could see the particle in my comsol. I will give you mail for this. Thanks.

  4. Did you make the turbelent module already? 🙂

  5. There is a new turbulent hydrocyclone model available from Comsol: https://www.comsol.com/model/flow-in-a-hydrocyclone-49271


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