Fluids

Fluids

Please help me how to define mass source at a point?

    • safwan_nasir
      Subscriber

       The gas sparging pipes were not really modelled instead a gas mass source was imposed at the locations of the gas sparging pipes so that the numbers of mesh used in the sim

    • Murari Iyengar
      Ansys Employee
      Hi safwan_nasir You cannot directly specify mass source at a point but you can create a small volumetric region and specify a volumetric mass source. To create a point mass source, you would have to define it in a UDF which can be more complicated if you are new to Fluent.
      For more information on volumetric mass source, please refer to the link below.
      7.2.7. Defining Mass, Momentum, Energy, and Other Sources (ansys.com)
    • DrAmine
      Ansys Employee
      Best as highlighted by is to create some Fluent Expressions and cell registers and just to set a non-zero value for source whenever one is in a cell register or when condition based on spatial coordinates is fulfilled. You do not require an UDF for that.
    • DrAmine
      Ansys Employee
      But If I think more about your case you can take advantage of the perforated walls BC to inject the primary phase out of holes along the walls where the holes are not resolved.
    • safwan_nasir
      Subscriber
      Thanks for the reply. Let me further explain my problem. Actually I'm currently using this mesh. I want to make structured mesh to reduce computations.

      These are the inlet face sections (1mm diameter each) from which air is injected into the water column. From different papers I have read that "they do not model these sections but create mass point source instead". I shall be very thankful if you guide from ab initio as these things are new to me or please suggest me any guide source from where I can follow complete steps. Thank you again.
    • Rob
      Ansys Employee
      Stop trying to build an O-grid, just pave the whole surface. It's most likely more efficient for the cell count and will reduce the likelihood of large jumps in cell size and squashed faces.
      You can split cells out of the mesh in Fluent and then add mass into these separated cells. Or you can tag the cells with a UDF and then add the mass. I've used the former and seen the latter.
    • safwan_nasir
      Subscriber
      Thanks alot.
    • DrAmine
      Ansys Employee
      So a sort of sparger: the easiest way is to go back to Meshing and create dedicated named selection for this faces or do what mentioned. Perforated walls won't work as your gas phase is secondary phase.

      If you do not expect any accumulation and large volume fractions you can even use DPM and code a your injection to just inject gas from the requested inlets.
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