Fluids

Fluids

How to implement a source term using UDS in the Expression Editor of Fluent

    • Lola
      Subscriber

      Hello,


      I want to simulate water treatment in a channel by using wetlands. The idea is that when water passes through the wetlands, a first-order decay term will be applied inside the wetlands, and this mechanism will promote the nutrient removal from water. The wetlands are being represented by a porous medium.


      I thought of doing the following:


      1) Create a user-defined scalar (UDS) to represent the nutrients;


      2) Create one source term for the UDS in the wetlands cell zone;


      3) Create an expression for the UDS source term, in which source term = -k*C (k = constant of removal, C = nutrient concentration = the UDS itself).


      My difficulty is in inserting the C term in the expression editor of Fluent. I looked for the UDS in the Variables option of the editor box, but I could not find it. I tried to write "uds-scalar-0" (the name that appears for the UDS in the Custom Function Calculator) in the editor box, but it says that the name was not defined. How can I define the UDS so that it can appear in the editor expression? Or, what should be the name of the UDS to be put in the expression editor? The figure below shows the situation.


    • DrAmine
      Ansys Employee
      It will be supported with the release of 2020 which will be released soon.
    • Lola
      Subscriber

      Hello Amine,


      Thanks for your reply. Do you have an estimate of the release date of 2020? Meanwhile, is there any other way to implement the -k*C term as a source term inside the wetlands zone?


      Kind regards,

    • DrAmine
      Ansys Employee
      Officially in the next few weeks. If you are using academic version just look on the portal.
    • BiomedModeller
      Subscriber

      Dear abenhadj,


      Your comment was very helpful. I installed 2020 and I see the UDS added to the list of variables. Could you please help me explaining what to do if there is more than one UDS. 


      I have 3 UDSs and in Expressions Fluent only brings one UDS (like general) in variables.


      Thanks

    • BiomedModeller
      Subscriber

      I think I found it and I am asking for the confirmation, and helping others if correct.


      I used this terminology:


      UDS (uds="uds-0")

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