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Particle injection issues in a cyclone

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Old   March 15, 2019, 12:36
Exclamation Particle injection issues in a cyclone
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Hello dear all,

I'm facing some issues regarding particle injection in a 3D simulation of a hydrocyclone (centrifugal equipment used to separate particles from fluids like water for example). My procedure was:
-First, I designed a mesh with dense concentration of cells near the walls of the equipment, in order to get the effect of the walls in the fluid's behaviour.
-Then, a simulation was performed using liquid water as fluid, time transient, pressure-based solver, RSM for turbulence effects and no-slip condition for the walls. I used a specific mass flow rate as inlet condition.

The approach used here was: obtain the fluid velocity field initially and, after this, inject particles as a post-processing exercise (widely used in the literature). The simulation was stopped when the flow-time reached 2 seconds, since the variables studied (inlet pressure, mass flow rate in the outlets) remained constant.

(Until here I had no problems regarding the simulations. I also performed the GCI test to ensure that the size of the mesh don't affect my simulations and some experiments using the equipment were conducted to validate some results related to fluid dynamics.)

After these steps the DPM was enabled and the injections were created. I attached here some pictures of the parameters which I have set in the DPM window and the parameters for each injection. (I needed to set many injectons in order to represent the size distribution of the feed).

For the DPM, the inlet boundary was defined as reflect, the walls were defined as reflect too, using 0.9 for reflect coefficients (normal and tangential). The outlets were set as trap.

When I track the particles in the post-processing, I get an efficiency of 96% (96% of the particles injected were collected in the underflow - an pressure-outlet boundary). The experimental results showed 91%. Until here everything is ok, however when I change the inlet conditions (lower the mass flow rate) I still get high efficiences(near 96%, 95%,...) It seems that no matter what I do, I always get the same results with the injections.

I've searched and read many articles looking for some approach to solve this problem but most of them doesn't show the procedures that they used to get their results.

I don't know if I'm missing something. Does anyone here already faced the same problem? I would appreciate if you could help me with this, its a crucial part of my dissertation and I don't know what to do anymore.

Thank you for your kind consideration of my problem.
Attached Images
File Type: png Tracking Scheme DPM.png (10.3 KB, 12 views)
File Type: png Physical Models DPM.png (11.5 KB, 11 views)
File Type: png Numerics DPM.png (15.3 KB, 9 views)
File Type: png Point Properties Injections.png (28.3 KB, 8 views)
File Type: png Turbulent Dispersion - Injections.png (26.8 KB, 7 views)
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dpm, injection, particle

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