Fluent Reversed Flow for a cascade simulation

manukamin · December 27, 2012, 10:51

Hey guys,

I need to study flow properties for a particular cascade that I've designed. I tried out first with the simplest conditions using ANSYS FLUENT.

My fluid model in inviscid, incompressible(Euler) and subsonic. It is a compressor cascade configuration. Inlet condition is given to be velocity inlet and exit as outflow. The top and bottom surfaces are periodic (translational). I have attached an image of my geometry .

For this simple configuration, Fluent says there's reverse flow occuring on outlet face.
Would anyone happen to know what could be the possible reason?

msaeedsadeghi · December 28, 2012, 11:20

You may need to add a free channel to outlet.

itsqi7 · January 24, 2013, 22:15

Quote:

Originally Posted by msaeedsadeghi

You may need to add a free channel to outlet.

Hi, could you pls specify how to add that? Thanks!

msaeedsadeghi · January 25, 2013, 00:18

Quote:

Originally Posted by itsqi7

Hi, could you pls specify how to add that? Thanks!

Add it in Gambit. Add a straight channel to it. Reverse flow will be disappeared if the length was enough.

itsqi7 · January 25, 2013, 00:20

Quote:

Originally Posted by msaeedsadeghi

Add it in Gambit. Add a straight channel to it. Reverse flow will be disappeared if the length was enough.

Thanks for ur reply. It seems different from my problem. Could you pls explain my question?
http://www.cfd-online.com/Forums/flu...ow-output.html
Thank you.

msaeedsadeghi · January 25, 2013, 00:24

Which forces makes the oscillating flow? inlet or outlet condition causes it?

itsqi7 · January 25, 2013, 04:42

Quote:

Originally Posted by msaeedsadeghi

Which forces makes the oscillating flow? inlet or outlet condition causes it?

actually it's the diaphragm between inlet and outlet causes the oscillating flow. Thanks.

msaeedsadeghi · January 25, 2013, 04:59

so both inlet and outlet do the same, at some time inlet and at the other time does as outlet. correct? Is your case unsteady?

itsqi7 · January 25, 2013, 15:41

Quote:

Originally Posted by msaeedsadeghi

so both inlet and outlet do the same, at some time inlet and at the other time does as outlet. correct? Is your case unsteady?

Exactly，they r unsteady. In the first pi phase, there is inflow from the inlet and outflow at the outlet, and in the last pi phase, reversed flow comes from both of them.
Thanks.

msaeedsadeghi · January 26, 2013, 02:29

You should use pressure inlet for both outlet and inlet. For more configuration you should use a DEFINE_PROFILE udf.

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December 28, 2012, 11:20		#2
msaeedsadeghi Senior Member SSL Join Date: Oct 2012 Posts: 226 Rep Power: 13	You may need to add a free channel to outlet.

January 25, 2013, 00:24		#6
msaeedsadeghi Senior Member SSL Join Date: Oct 2012 Posts: 226 Rep Power: 13	Which forces makes the oscillating flow? inlet or outlet condition causes it?

January 25, 2013, 04:59		#8
msaeedsadeghi Senior Member SSL Join Date: Oct 2012 Posts: 226 Rep Power: 13	so both inlet and outlet do the same, at some time inlet and at the other time does as outlet. correct? Is your case unsteady?

January 26, 2013, 02:29		#10
msaeedsadeghi Senior Member SSL Join Date: Oct 2012 Posts: 226 Rep Power: 13	You should use pressure inlet for both outlet and inlet. For more configuration you should use a DEFINE_PROFILE udf.