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Old   September 19, 2012, 02:32
Default Boundary Condition
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Prashant Kumar Singh
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Hello
I have given BC at inlet of a compressor as velocity profile and total T
And at outlet BC as mass flow rate but it did not run, showing error that P is not mention at any boundary.I wanted to know is it necessary to give Pressure as a BC in case of compressor at any one of the boundary.

If my compressor outlet is going into the atmosphere then what could be the pressure(total/static) boundary condition at outlet plane.

Thanks
Prashant
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Old   September 22, 2012, 20:01
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Maged
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Hello Prashant,

You need to set the boundary condition at the outlet as:
P_static = atmospheric pressure

Note that your outlet plane should be far enough from the compressor blades.
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Old   September 24, 2012, 01:18
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Prashant Kumar Singh
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Thanks Maged_CFD
I did same thing and give outlet static P 101325Pa and after completion in cfx also shows outlet static P as 101334Pa which ony 9pa higher i think this BC is ok.
thanks once again
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Old   October 31, 2012, 06:15
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Pedram Mojtabavi
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You need to set both inlet and outlet boundary conditions as pressure. You calculate the inlet velocity from the compressor flow coefficient (phi) and dynamic pressure (Pv) as well. Then you calculate the inlet static pressure (Ps=Pt-Pv). Pt as total pressure and Ps as static pressure. the outlet static pressure can be calculated by the compressor head coefficeint (si). By in entering these BCs your solver will be able to calculate the velocity and pressure field.

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