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-   -   Back flow in axial comperssor (http://www.cfd-online.com/Forums/cfx/117259-back-flow-axial-comperssor.html)

eslamnagy May 5, 2013 17:28

Back flow in axial comperssor
 
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

ghorrocks May 5, 2013 18:52

FAQ: http://www.cfd-online.com/Wiki/Ansys...gence_criteria

And also read the best practises guide for turbomachinery in the CFX documentation.

eslamnagy May 26, 2013 08:36

Quote:

Originally Posted by ghorrocks (Post 425426)
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)

ghorrocks May 26, 2013 09:00

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.

Tushar@cfd May 27, 2013 06:42

Quote:

Originally Posted by eslamnagy (Post 425415)
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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