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3D mixing of two fluids in cylinder with stirrer bar

    • Patrickodon
      Subscriber

      Hello,

       

      I want to mix two fluids in a basic cylinder. I've tried doing it through Inventor

       

       

      and DesignModeler

       

       

      where I have 212 mm of water at the top, and 1 mm of milk at the bottom (both with a diameter of 265 mm), with a 20 mm tall gap for a stirrer bar (diameter 52 mm) in the bottom centre (the fluids are arbitrary, they're just both miscible).

      I can't get them to mix properly; the Inventor one won't let me create separate bodies, and in DesignModeler, though I am allowed to make two separate bodies by creating a separate drawing for the milk and importing it as a STP file in DesignModeler, I am not allowed to open the Setup:

       

       

      How should I set this up? I know there's a 2D tutorial for this (_ANSYS Customer Portal_Training Materials_eulerian_multiphase_granular), but I want to go in 3D. Do I need to create a zone where the stirrer bar is that they initially mix in, and how do I do that?

       

      To summarize: I have a cylinder with a bottom 1 mm layer of milk, covered by 212 mm of water. I'm mixing them via a stirrer bar (the "doughnut" for which I've left blank) rotating in the bottom-centre. How do I do this in 3D?

    • Rob
      Ansys Employee

      Have a look at the mrf examples for mixing tanks. You may, or may not, need a separate zone for the milk, but if you do have mutliple zones read up on share topology too.  Note, as milk and water mix it's a species problem, not multiphase. If you also have a head space (air) at the top then you have a multiphase model, with the liquid phase being a species mixture. 

      • Patrickodon
        Subscriber

        Thanks for the reply. I found this tutorial (

        ) which is kind of like what I have, without having two materials mixing (it only has one material), and it's in 2D.

         

        How do I set up 3D mixing for two fluids (I imagine it's to do with setting up multiple zones)? My setup seems very simple, all I want is to be able to mix two fluids (ideally in 3D). I'm surprised I can't find a tutorial on this - I'm checking here (https://www.youtube.com/@AnsysTutor/videos), here (https://www.youtube.com/@AnsysLearning/videos), here (https://www.ansys.com/academic/learning-resources), and here (https://courses.ansys.com/).

    • Rob
      Ansys Employee

      It's a species model, so have a look at the combustion tutorials: just don't turn on the reactions part! You'd then patch in the second species. 

      • Patrickodon
        Subscriber

        I'm looking at this

         

         

        It has mass flow inlet, mass flow air, and an outflow. It's also in 2D (as are the other two I've looked at)

         

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        Are there any basic models with mixing, like mine? My one is very simple, I literally just have two fluids mixing in 3D with no input/output (i.e. the fluids start inside the cylinder). Everything else is in 2D and has fluids in/out during mixing.

  • Rob
    Ansys Employee

    There may be a mixing tank tutorial somewhere, but I can't see one for single phase on the public side of our system. Typically, we don't have tutorials for every application but use parts of a few where needed. So, 2d to 3d is trivial; use patch rather than an inlet/outlet and review the chemistry to just look at mixing. 

    There is a webinar  https://www.ansys.com/en-gb/resource-center/webinar/mixing-tank-modeling  which may be of interest. 

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