What does this message mean?

pks126 · April 26, 2013, 08:16

Dear All
I am doing inflow distortion analysis in CFX for single stage axial flow fan.
While running following is showing in between iteration,
what is its significance?

****** Notice ****** |
| A wall has been placed at portion(s) of an INLET |
| boundary condition (at 6.9% of the faces, 4.3% of the area) |
| to prevent fluid from flowing out of the domain. |
| The boundary condition name is: Inlet. |
| The fluid name is: Air Ideal Gas. |
| If this situation persists, consider switching |
| to an Opening type boundary condition instead. |

thanks
+---------------------------------------------

ghorrocks · April 26, 2013, 08:21

It means exactly what it says: you have back flow at your inlet which the solver artificially stopped. This is sometimes not a problem, but often it is and it certainly makes convergence harder. Move your inlets further upstream to get it out of the recirculation.

pks126 · April 26, 2013, 10:58

Thanks Sir,
Yes I am getting problem in convergence. Can i say that back flow at the inlet may be due to compressor stall or surge?

ghorrocks · April 27, 2013, 07:50

There is an FAQ on this as well (the concept is just as applicable to inlets as outlets).

No, this is unlikely to be related to stall or surge. Don't forget an inlet is upstream of the rotor

.

April 26, 2013, 08:16	What does this message mean?	#1
pks126 New Member Prashant Kumar Singh Join Date: Jun 2012 Location: IIT Bombay Posts: 19 Rep Power: 14	Dear All I am doing inflow distortion analysis in CFX for single stage axial flow fan. While running following is showing in between iteration, what is its significance? **** Notice **** \| \| A wall has been placed at portion(s) of an INLET \| \| boundary condition (at 6.9% of the faces, 4.3% of the area) \| \| to prevent fluid from flowing out of the domain. \| \| The boundary condition name is: Inlet. \| \| The fluid name is: Air Ideal Gas. \| \| If this situation persists, consider switching \| \| to an Opening type boundary condition instead. \| thanks +---------------------------------------------

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April 26, 2013, 08:21		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,872 Rep Power: 144	It means exactly what it says: you have back flow at your inlet which the solver artificially stopped. This is sometimes not a problem, but often it is and it certainly makes convergence harder. Move your inlets further upstream to get it out of the recirculation.

April 26, 2013, 10:58		#3
pks126 New Member Prashant Kumar Singh Join Date: Jun 2012 Location: IIT Bombay Posts: 19 Rep Power: 14	Thanks Sir, Yes I am getting problem in convergence. Can i say that back flow at the inlet may be due to compressor stall or surge?

April 27, 2013, 07:50		#4
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,872 Rep Power: 144	There is an FAQ on this as well (the concept is just as applicable to inlets as outlets). No, this is unlikely to be related to stall or surge. Don't forget an inlet is upstream of the rotor .