Fluids

Fluids

Population balance model for Eulerian multiphase model

    • ALX
      Subscriber

      Hi,

      I'm trying to simulate particle deposition on a 3D pipe (NOT through DPM). I activate the Eulerian multiphase model and enabled the dense discrete phase model. So in total, there is one Eulerian phase (the fluid), and one Discrete phase (the solid particle that I should enable by setting an injection, right?).

      When I load the PBM and try to enable it, the following message appears:

      Error: CDR: invalid argument [1]: wrong type [not a pair]

      Error Object: ()

      Can anyone explain why is that? and how one might overcome this issue?

      If the population balance only controls the Eulerian phases only and not the discrete ones, how can I make the PBM control the discrete phase?

      Thanks.

    • Rob
      Ansys Employee
      The error tends to mean that something hasn't been set in a panel that must be. I assume you've set an injection for the DPM part? However, I'm not sure how the models will interact as the injection also controls the particle size. What are you trying to model?
    • ALX
      Subscriber
      Hi Rob IÔÇÖm trying to simulate solid particles deposition on the (internal) pipe wall in oil flow.
      Yes I have set an injection from inlet of uniform particle diameter distribution (even when I changed it to Rosin-Rammler, it doesnÔÇÖt make any difference). This is after I chose Eulerian model with Dense Discrete Phase Model.
      Intriguingly, when I added another Eulerian phase, the phase bar in PBM is not greyed out and you can now see (and choose) the Eulerian (secondary phase) youÔÇÖve just added. However, the Discrete phase still doesnÔÇÖt appear on the PBM.
      So, I think that because I added one Eulerian phase (the primary phase), the secondary (Eulerian) phase is the missing input, hence, the PBM couldnÔÇÖt find a (secondary) phase to apply the PBM calculations to it. (Correct me if IÔÇÖm wrong here)
      Is there a way to control the discrete phase by population balance? e.g. through udf.
      Thanks.
    • Rob
      Ansys Employee
      If you're depositing particles are you assuming that they stay on the wall? Do you need to see the build up effect on the local flow? For DPM we'd typically just use many particle sizes and not worry about population balance: there is a collision model but that's tuned for droplets.
    • ALX
      Subscriber
      Hi Rob,
      Yes, I am assuming particles will be trapped once they hit the wall.
      For this, is there a way (udf, calculation activities, .. etc.) to visualise the particles, in post processing, that hit and trapped on the wall surface? To have the option to show only those who have been trapped only and hide those in the bulk.
      ThatÔÇÖs actually a good idea to enter different particle sizes.

    • DrAmine
      Ansys Employee
      You use DPM and rely on DPM Accretion rate to post-process the accretion along the walls. if you want to show in discrete manner where the particles are hitting the wall (say to see where they hitting the wall) you probably need to do DPM Sampling along the walls and second step use that Sample file as injection to just show the seeds.
    • ALX
      Subscriber
      Hi Dr. Amine Yes, I tried this approach and showed the accretion as contours. I also tried to export particle tracking history and import it to post-processing. However, this shows the particles tracked and I believe that in the calculation process, the particles which hit the wall are excluded from the history. (correct me here if I'm wrong). So, is there a way to store data (location) of the particles hitting the wall and fulfilling the trapped criterion? and be able to show it in post-processing.
      I haven't used Sampling yet. Can you please share a tutorial or a website explaining this?
      Many thanks.
    • Rob
      Ansys Employee
      Trapped particles are tracked up to the point that they hit the surface. As such they'll be in the surface sample. Not sure about a tutorial, check in the Help ones or just have a play: it's in the Results section.
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