Continuity not converging

    • otani

      I am running a model with the following specifications:

      • pressure-based

      • 2-D, axisymmetric

      • steady

      • turbulent (sst k-omega)

      • species transport (binary system of dimethylformamide and carbon dioxide)

      • UDFs for density, specific heat, viscosity, and thermal conductivity for CO2

      • UDFs for specific heat, viscosity, and thermal conductivity for DMF

      • polynomial fit for density for DMF

      • pressure outlet

      • two mass flow inlets, one for each species at nearly equivalent mass flow rate, different hydraulic diameter

      • constrained temperature range [300,335]K due to range of data UDFs are based on

      Continuity residual is staying consistently at E-3 and not dropping. I have tried many things like changing the polynomial fit to be higher order, changing the computational schemes for momentum, changing the relaxation factors, refining my mesh, and nothing has made it converge. Eventually around 30,000 iterations, the simulation diverges. Attached is a photo of the residuals up to the point of divergence.

      Any advice would be greatly appreciated. I can provide more information as necessary.

    • DrAmine
      Ansys Employee
      What about mass imbalances and energy from flux report as well as behaviour of some monitor points?
    • otani

      Hi Amine,


      Thank you for your response. I've added the flux reports below. Could you expand upon what you mean by the "behavior of some monitor points"?


      Mass Flow Rate (kg/s)


      innerinlet 0.00034

      interior-surface_body -0.92569468

      outerinlet 0.00031

      outlet -0.00064999698

      wall -0

      Net 3.018828e-09



      Custom Vector Based Flux

      Total Energy


      axis -9.0669255e-24

      innerinlet 4.2376269e-07

      interior-surface_body -0.0010646494

      outerinlet 3.2457537e-07

      outlet -6.8616645e-07

      wall 3.5971273e-08

      Net -0.0010645512


      Thanks much,


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