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Old   August 14, 2003, 11:12
Default boundary conditions
  #1
hedonists
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Is it possible to use this set of boundary conditions in Fluent for 2D pipe flow:

Pressure inlet and constant mass flow rate?
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Old   August 14, 2003, 12:41
Default Re: boundary conditions
  #2
cfdweirdo
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For compressible flow: Total Pressure inlet & Static Pressure outlet

or

Mass Flow Inlet & Static Pressure Outlet

For incompressible flow: Velocity inlet & outlet condition
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Old   August 15, 2003, 01:19
Default Re: boundary conditions
  #3
mateus
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Hi!

I'm not shure what you want. Maybe you have the same problem as me...I have a known upstream pressure and velocity, but in Fluent you can't define both parameters on inlet bc. What I do is I define velocity inlet and pressure outlet (upstream pressure - pressure losses in pipe), and after simulation converges check if the pressure on inlet agrees with experimental one.

It's a bit awkward solution but I think most of the people with this problem solve it this way...

regards

MATEUS
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Old   August 15, 2003, 10:38
Default Re: boundary conditions
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hedonists
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Thanks all. I am suprised that Fluent doesn't have a constant mass flowrate outlet boundary condition.
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Old   August 17, 2003, 04:58
Default Re: boundary conditions
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thomas
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I think the outlet boundary condition 'outflow' may help you for your problem and get constant mass flow rate. thomas
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Old   August 17, 2003, 20:54
Default Re: boundary conditions
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zhsnaky
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constant mass flow rate is controled by approciate pressure. this may be the reason for no boundary conditions of constant mass flow rate in fluent software.
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Old   August 20, 2003, 05:23
Default Re: boundary conditions
  #7
jieremy
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Note that outflow boundaries cannot be used in the following cases:

if a problem includes pressure inlet boundaries; use pressure outlet boundary conditions (see Section 6.8) instead
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Old   August 21, 2003, 13:31
Default Re: boundary conditions
  #8
hedonists
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For non critical flow, the mass flow rate is governed by both inlet and outlet pressures. To obtain a constant mass, it seems that I should use constant pressure inlet and try-and-error outlet pressure. Is this a correct way?
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Old   August 21, 2003, 20:24
Default Re: boundary conditions
  #9
jieremy
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for the compressible flow,you can use these boundary condition:"Mass Flow Inlet & Static Pressure Outlet " then you have made the mass flow as a constant when you define the "Mass Flow Inlet".
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Old   August 24, 2003, 23:37
Default Re: boundary conditions
  #10
hedonists
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To be clear, the conditions I have are: constant mass flow rate and constant inlet pressure. But I don't know the downstream pressure. The question was: How to set the boundary conditions?
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