Fluids

Fluids

Regarding User Defined Scalar

    • sj21
      Subscriber

      Hello, i want to implement a UDS equation( image attached) in a multiphase flow for the secondary phase.

      When I compare my equation to the equation in Fluent theory guide ( also attached) , I understand that diffusivity constant should be taken zero and density is constant in my case.

      But i am not not understanding how to remove the volume fraction term from the original UDS equation which is given in theory guide.

      Can anyone help me to implement my equation as UDS.UDS equation in theory guideMy equation

    • DrAmine
      Ansys Employee

      Will your scalar be convected by the phase velocity or by the bulk velocity?

    • sj21
      Subscriber

      Phase velocity. Velocity vector in my UDS equation is the secondary phase velocity.

    • DrAmine
      Ansys Employee

      I then recommend to use the bulk equation transport and write your own DEFINE_UDS_FLUX to have it as secondary velocity field. The volume fraction will always appear as you are trying to solve for the phasic UDS. (Like Temperature, Energy, etc..).

    • sj21
      Subscriber

       

      I attached the mixture or bulk transport equation from the manual. After changing the velocity vector to secondary phase velocity, how to change the densities in the transient term  to that of secondary phase density?

       

    • DrAmine
      Ansys Employee

      By using an UDF to adjust the Unsteady term.

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