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This is the first time for me here.

Consider a pipe with inlet and outlet. This outlet is open to atmosphere.

In CFD we can set inlet having variable velocity profile (e.x. parabolic profile) and I understand the flow phenomenon.

What will happen if we set inlet having variable pressure profile (e.x parabolic profile)? Can someone explain the flow behaviour?

Also, will there be difference between compressible and incompressible flow?

Thanks in advance.

PS: I mentioned CFD so that it will be easy to frame my question.

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What will happen if we set inlet having variable pressure profile (e.x parabolic profile)? Can someone explain the flow behaviour?

varying the inlet pressure profile will vary the flow rate, possibly cause boundary layer separation, eddies, vorticity, etc. There are many possibilities.

Also, will there be difference between compressible and incompressible flow?

Depends. Generally flow velocity determines whether flow is laminar or turbulent, but channel geometry also plays a role. Mach number generally determines if a flow is compressible. Subsonic flow can generally be considered incompressible.

But your question - not really clear. Specifically what are you trying to determine.

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  • $\begingroup$ Thanks for the response. It is not something I specifically want to determine. Just was curious of the flow behaviour. $\endgroup$
    – Selva
    Jul 12 '16 at 16:55
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If you set parabolic profile for axial velocity at inlet then flow will be axial throughout pipe's length. This is because, apart from hydrostatic contribution, there is no pressure variation in radial direction. If you set parabolic profile for pressure at inlet, then you will have radial motion too (at least at inlet), and how the flow shall develop subsequently is hard to tell. Adding compressibility to fluid only makes the question more difficult.

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