convergent-divergent nozzle Fluent simulation: converged but BC not respected

    • bottini.henny

      hello everybody,

      I have computed the flow field in a convergent-divergent rocket nozzle in Fluent with these settings:
      -) inviscid flow model
      -) density-based solver
      -) steady flow
      -) 2D axisymmetric (the flow domain ends at the nozzle exit: I do not simulate the jet expansion outside the nozzle)

      the computation converges very well, and I see no warnings or error messages,
      but when I post-process the data in Fluent, or CFD-post, I see that
      the gauge-pressure value I set as boundary condition (pressure-outlet type) for the nozzle exit is not respected (the final pressure at the nozzle exit is much lower than my BC).
      The pressure-inlet BC, however, is respected.

      Can someone explain me why is this happening (without any warning from fluent),
      and how can I have my computation converge with the BC I impose at the nozzle exit?

      Thank you for your time and attentio

    • DrAmine
      Ansys Employee

      Add a screenshot showing the pressoure Outlet Panel in Ansys Fluent. Aslo issue an area weighted average of the Static Pressure in Ansys Fluent there. Also Add a screenshot showing the values of Static Pressure at that outlet with node values set to off.

    • DrAmine
      Ansys Employee

      Is your flow supersonic at the outlet? If yes then values there won't be used as all information get extrapolated from neighbooring cells (I remind here the chracteristcs theory)

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