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Old   May 5, 2013, 17:28
Default Back flow in axial comperssor
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eslam nagy
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DEAR SIRS
I NEED TO KNOW THE BEST BOUNDARY CONDITIONS USED IN MODELING OF AXIAL FLOW COMPRESSOR IN ANSYS CFX .
IF I USED INLET PRESSURE 1 Pa AND MASS FLOW RATE AT OUTLET =20KG/S
THE SOLUTION NOT CONVERGE ???I DO NOT KNOW WHY ??
THE PRESSURE RATIO =2.105
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Old   May 5, 2013, 18:52
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Glenn Horrocks
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FAQ: http://www.cfd-online.com/Wiki/Ansys...gence_criteria

And also read the best practises guide for turbomachinery in the CFX documentation.
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Old   May 26, 2013, 08:36
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Quote:
Originally Posted by ghorrocks View Post
FAQ: http://www.cfd-online.com/Wiki/Ansys...gence_criteria

And also read the best practises guide for turbomachinery in the CFX documentation.
i mean the best type of boundary condition (pressure inlet or mass flow rate inlet also pressure outlet or mass flow rate outlet)
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Old   May 26, 2013, 09:00
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Usually a mass flow inlet with a pressure outlet is best.

But this is all discussed in the documentation. You really should read it so you know the answers to these questions yourself.
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Old   May 27, 2013, 06:42
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Tushar Chourushi
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Quote:
Originally Posted by eslamnagy View Post
DEAR SIRS
I NEED TO KNOW THE BEST BOUNDARY CONDITIONS USED IN MODELING OF AXIAL FLOW COMPRESSOR IN ANSYS CFX .
IF I USED INLET PRESSURE 1 Pa AND MASS FLOW RATE AT OUTLET =20KG/S
THE SOLUTION NOT CONVERGE ???I DO NOT KNOW WHY ??
THE PRESSURE RATIO =2.105
Boundary conditions seems to be OK...
You can also give the following boundary conditions:
Inlet: massflowrate @ 20 kg/s
Outlet: Static Pressure

Try to put Y+ value correctly as found by the formula.

Apply SST turbulence model, if you are not having much experience in CFD.

I hope this will improve your convergence.
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