Learning Forum

[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]

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]

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)