Fluids

Fluids

Transient Simulation Continuity Not Converging but other residual Converge

    • Ayomikun1
      Subscriber
      I am Modelling a 2D 203.2mm Steel Pipe, centered in a 50 by 50m domain, surrounded by seawater. The Pipe wall Is specified at -47.3C and the Seawater at 4C. The Solver is Set to Transient but I find that every other residual ( Energy, x-velocity and y-velocity) converge at the 0.001 specified except the continuity even though the results produced from the model is what was expected. Is my model inaccurate and how do I push my model towards converging or using other monitiors to provide confidence in the accuracy of my model?n
    • Rob
      Ansys Employee
      What time step did you use? Re monitors, do the tutorials in the Help system as at least one will cover how to set them up. n
    • Ayomikun1
      Subscriber
      I am using a time step of 0.05. My maximum Courant Number is below 1. No the tutorials havent help me find a solution to this problem
    • Rob
      Ansys Employee
      The tutorials will cover monitors. nIn buoyancy driven flow the flow can be transient, so steady solutions give poor convergence. For a transient flow the time step will depend on the flow velocity and rate of change of that and the temperature field. If the residuals don't converge but the monitor points stabilise and fluxes balance then you may find the solution is accurate enough: CFD is a tool and as such you need to assess the data it gives you. nTalk to your supervisor or the CFD lecturer, they'll be able to look at the results and advise. nAdding images of the flow and temperature field on here will also allow the wider community to help: staff are more limited due to the rules you read when signing up. n
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