Fluids

Fluids

UDS source term unit and expressions

    • BiomedModeller
      Subscriber

      Hi all,


      I am trying some mass transport using UDS.


      I am setting all coefficients and assuming the UDS unitless. The case is I expect the source terms to be of unit [kg m^-3 s^-1]. When I use an expression for sourceterms (as they depend on other UDSs) Fluent gives error that it should have no unit. required []. WHY?


      I have same problem with flux on a wall boundary. It again says it should have unit of [].


      Thanks

    • DrAmine
      Ansys Employee
      source term will be density/time. Also mention which release you are using also provide the whole expression here
    • BiomedModeller
      Subscriber

      Thanks Amine for the response.


      I agree it should be but it is not.


      I am using 2020 R1.


      The source term is:


      K[s^-1}* UDS(uds="uds-0"] * (A [] - UDS(uds="uds-1"]

    • DrAmine
      Ansys Employee

      Try providing a dimensionless source term first. Let me double check and get back to you later today or the next week.

    • DrAmine
      Ansys Employee

      Okay: actually very clear Fluent does expect the source term not to have the dimension as UDS itself does not have unit. You just need to provide the right formula and just make dimensionsless.

    • BiomedModeller
      Subscriber

      Thanks a lot for the reply Amine!


      But how Fluent demands it dimensionless when the formula is :



       


      d(rho*phi)/dt has the dimension of kg m^-3 s^-1


      Sorry if my question is naive

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