Fluids

Fluids

Laminar Flow in Drain Pipe with solid Particles

    • arman
      Subscriber

      Hi everyone,

      Regarding my project, I have to simulate laminar flow in drain pipe and movement of solid particles should be tracked! My problem is that these particles are not mixed in water, and they should remain at rest, before the flow comes through inlet. Actually I have to find the minimum necessary velocity, that is required to move these solid particles through the pipe for avoiding sediments. 
      I tried to use DPM model in Ansys Fluent 19. But the main problem is that I cannot define an inlet for these solid particles! I do not know how I can add them right after the flow inlet in my simulation!
      Is there any way to make the simulation understand, that the solid particles are in pipe before flow comes? I also tried to define a section for injection of these particles, but it did not work.
      I'll be thankful for any advice and help!

      Thank you in advance!

      Arman

    • Rob
      Ansys Employee

      DPM uses an injection to add particles to the domain, rather than an inlet, and this is covered in the User Guide (click on help on any of the panels and go from there). However, the standard models assume the particles are smaller than the cells. Additionally in the DPM approach we track a point mass which has the drag etc for the defined diameter. If you have large particles you may need to consider the macro particle model. 


      I'd suggest looking up saltation too: this may be important depending on whether you're looking at single large particles or a sediment bed. 


      Multiphase models require a good understanding of the physics, not just of CFD modelling, so can be quite difficult start with: the set up is usually the easier part! 


       

    • Raef.Kobeissi
      Subscriber

      Just on the issue of defining an inlet for DPM. Particles  using DPM are injectable and you can chose a surface or a defined  point as the starting location for the injection.


      Regards

    • arman
      Subscriber
      Thank you so much for your detailed reply! Actually these solids are bigger than cell size, you can consider that i want to simulate the movement of some screws in drain pipe! Is that possible with DPM?

      Thanks!
    • arman
      Subscriber
      That is is exaclty, what I could not find for my simulation! Consider my flow domain as cylinder pipe. How can I select a surface on this pipe to determine it as injection point of my solids?
      What i‘ve done is, i tried to add a vertical pipe to my flow domain and I wanted to set connection surface of these two as injection point! Bur it did not work! Can you help me further? Any Idea how i can set injection area for example like circle surface on the wall or domain flow?

      Warm Regards
      Arman
    • Rob
      Ansys Employee

      The injection just needs a surface, so you just need to split the geometry where you need to add particles. 


      Re the relative sizes, if the screws are big compared to the mesh you may struggle as the multiphase models are designed for small diameter (relative to the mesh) particles/droplets/bubbles.  Read up on the Macro Particle Model, and general multiphase to understand how these are applied, and whether they meet your needs. l


       

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