Fluids

Fluids

constant Source term vs. mass flow inlet

    • majam
      Subscriber

      Hello all,

      I am simulating reactions in a fed-batch bioreactor. I have feed coming to the system and I tried to simulate it as a constant source term, The way I calculate the feed rate is kg of feed/(second ) divided by the volume of the region where I apply the feed. (it is a small region). 

      I tried to make a feed nozzle in my geometry to check if the results are different when I use mass flow inlet (kg/s of feed) and they are way different from each other.

      Can anyone help me with this? Does my source term lack something? 

      Thanks,

       

    • Rob
      Ansys Employee

      Check you're adding mass AND species into the system at the same rate: setting one or the other may result in unexpected results. It's a good approach but check momentum is more-or-less as expected. 

    • majam
      Subscriber

      Hello Rob,

       

      Thanks for your response, for the source term, I separate a small part of mesh cells and create a new zone to enter the feed. The zone is HEX and has a dimension of 0.02,0.02,0.01. But when the zone is separated and I want to check the volume in the report, I can see that the volume is 8.9e-6, but it should be 4e-6. Any clue why this happens?

       

      Thanks,

    • Rob
      Ansys Employee

      The register will only contain cells that are fully within the set ranges. So, if the box is slightly offset or fractionally misses a part of a cell it'll not be in the register. 

    • majam
      Subscriber

      But this seems the opposite since the volume of the register is bigger than the dimensions I give for the cell register.

      So it means it includes whatever cell is around as long as it is slightly within the defined dimensions, am I correct?

    • majam
      Subscriber

      With this in mind, which volume should I consider when I want to calculate the source term? I am using the exact volume I get from the volume report, not the dimensions that I define for the region.

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