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Translational periodicity and compressible flows

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Old   June 4, 2020, 19:35
Question Translational periodicity and compressible flows
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Background: I am trying to simulate flow over an infinite plate with hemispherical pimples. I reduced my domain to a row of a few hemispherical pimples. I am applying periodic BC in two directions: sideways (pressure drop=0) and from inlet to outlet (specified pressure drop). The top surface is a simple free-slip wall.

Problem: My set-up works fine if I use air with constant properties but as soon as I switch to ideal gas air I get the following error message:
"A mass and momentum model can be set for periodic domain interfaces only if all fluids have constant density".

Question: Is it possible to model compressible flows with periodic heat transfer through CFX?

Thank you in advance.
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Old   June 5, 2020, 17:21
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Old   July 15, 2020, 14:19
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I presume it is not possible simply because of the concept behind periodic boundary conditions. When you assign two boundaries as periodic, what you are telling the solver is that it has to enforce the velocity field on both boundaries to be equivalent, for a given pressure drop between them. How can the velocity field be equivalent between inlet and outlet if the flow is compressible (given that mass has to be conserved)?
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