Lagrangian Particle track

[jamesbewley]

Hello


I have been involved in a project to simulate the flow in a hydrocyclone. (using CFX-10)

Part of the project requires me to look at the efficiency.

To do this I have been trying to use the particle track method, to determine the number and size of particles going to ueach outlet, but have been getting some strange results.

All of the particles I put in, very quickly move to the outer wall and exit via the underflow orifice. I reality I would expect the smaller particles to stay close to the center of the cyclone and exit via the overflow orifice.

For background I have been running this using the SSG renyolds stress turbulance model (second moment closure), but only as a steady state.

I was wondering if anyone has some experience of this.

I also read somewhere that particle track could not cope with second moment closer turbulance models, does anyone know if this is the case.

I know this analysis should be run as a transient analysis(time limits have hindered this in the past) but could the fact I and running it as a steady state also cause the particle track to show the strange results.

Many thanks in advance

 

[ColourfulFigsnDiags]

I assume you have tested your simulation for grid and convergence independence? Could it be possible that you have given the perticles an incorrect density or otherwise specified the system incorrectly (check for dimensionless number using the same basis etc)?

I am not sure about the SS vs. Transient option- it really depends on the size of your particles and whether you have coupling between the phases (which would make the problem decidedly more complex! i.e. you assume the solid phase has no effect on the gas phase). In general I would have thought for small particles in a cyclone, a SS solution would be sufficient.

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