Fluids

Fluids

Why does Outlet Pressure value have no effect on Fluent when flow is Supersonic?

    • CleverBoy
      Subscriber

      Hello everyone,

      Iam working on a supersonic nozzle as a school project  and for Pressure Inlet - Pressure Outlet BCs, I specify 3 different outlet pressure values and at each one of them I get a flow seperation, shock-waves, at different locations etc.

      On this website: https://www.afs.enea.it/project/neptunius/docs/fluent/html/ug/node244.htm ,under the Defining Static Pressure section it says : "To set the static pressure at the pressure outlet boundary, enter the appropriate value for Gauge Pressure in the Pressure Outlet dialog box. This value will be used for subsonic flow only."

      This manual basically says any value for pressure outlet will not be used if the flow is supersonic. How can this be? How does Fluent calculate the exit pressure in this case? Every time I change the value of gauge pressure at the outlet I get a different result. Shouldn't I get the same result even if I change the outlet pressure? Are manuals wrong in this case?

    • aitor.amatriain
      Subscriber
      Are you sure that in both cases the flow at the outlet is supersonic? Could you please show us some pictures?
    • RK
      Ansys Employee
      Hello,
      Refer to this section of the user's guide for more explanation : 9.4.3. Modeling Inputs for Compressible Flows (ansys.com)
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