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Mixture model momentum equation in porous media

    • montenegro



      I need to specify the effect of the permeability in a porous medium in my case via UDF. Looking at the Fluent User's Guide, I can find the momentum equation for the porous media for the Eulerian Model - Equation (7-22).

      My first doubt is regarding the input in the Viscous Resistance (Inverse Absolute Permeability) box. Should I assume that porosity squared (γ^2) and volume fraction squared (α^2) are already part of the modification done when activating the porous model and only specify an UDF that calculates (1 / (K * k_rel)) or do I have to take into account the γ^2 and α^2 values in my UDF?


      My second doubt is regarding the Mixture Model. The User's Guide shows the modifications to the equations of the Eulerian Model, but I am working with the Mixture Model. What form does the momentum equation take in this case? Is it the same as in the Eulerian Model, but applied to the mixture? Do I create the UDF exactly the same way?

      Thank you.

      Best regards,

      Miguel Montenegro

    • Surya Deb
      Ansys Employee
      Hello, nThose terms represent the viscous and inertial drags , respectively imposed by the pore walls on each phase . They have been implemented like sink terms in the momentum equation. So you don't need to have the squared terms for the porosity and the volume fraction. In your UDF, you can just specify the inverse of permeability. Also keep in mind that the relative permeability will be set to 1 if you are not using the capillary pressure model. nYes, the mixture model should have similar model implementation but using mixture averaged velocity. nBut having said that, please do test it using a model that you can validate the results for from experiments or analytical data.nThis will give you more confidence on your model parameters and setup.nI hope this helps.nRegards,nSuryan
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