# direct map vs cyclic

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 December 13, 2010, 16:39 direct map vs cyclic #1 Senior Member   Nima Samkhaniani Join Date: Sep 2009 Location: Tehran, Iran Posts: 1,266 Blog Entries: 1 Rep Power: 24 im going to modeling a two phase-flow which is heated along pipe, my boundary is cyclic in U and alpha but not in p and T so im going to use following boundary .............wall.................. inlet outlet .............axis.................. i would like to direct map of outlet into inlet for alpha and U, alpha: inlet { type directMapped; value uniform 0; setAverage false; average 0; } outlet { type zeroGradient; } U: inlet { type directMapped; value uniform (0 0 1); setAverage true; average (0 0 1); } outlet { type zeroGradient; } p: inlet { type zeroGradient; } outlet { type fixedValue; value uniform 0; } T: inlet { type fixedValue; value uniform 0 ; } outlet { type zeroGradient; } are my boundaries corrects ? whats the meaning of value,setAverage, and average? what should be those values for direct map of outlet value into inlet value i want something exactly like cyclic boundary condition for U and alpha? P.S: i used changeDictionary Dict like below dictionaryReplacement { boundary { inlet { type directMappedPatch; offset ( 0 0 4e-5 ); samplePatch outlet; } } }

December 14, 2010, 05:52
#2
Senior Member

Stefan Herbert
Join Date: Dec 2009
Posts: 129
Rep Power: 16
Quote:
 Originally Posted by nimasam are my boundaries corrects ?
I think so.
Quote:
 Originally Posted by nimasam whats the meaning of value,setAverage, and average? what should be those values for direct map of outlet value into inlet value i want something exactly like cyclic boundary condition for U and alpha?
The value entry is as often ignored by any solver but holds just the actual value of the faces.
If you want to fix the mass flow through your domain for example you can use the average option. If "setAverage" is set to "true" (as you did for U) the values are mapped from the outlet but are scaled in a way to reach the specified "average"-value. Else this entry is ignored, too. So if you don't want to fix your average velocity to (0 0 1) you should turn off the setAverage-option.

Kind regards,
Stefan

 February 15, 2017, 12:58 #3 New Member   Michela Join Date: Mar 2015 Location: Italy Posts: 7 Rep Power: 10 Dear Nima I've got problem similar to yours: I'm trying to perform a LES simulation in a channel and I would like to reproduce cyclic boundary condition only for U, but not for a scalar release from the bottom of the channel. Have you managed to use directMappedPatch in the correct way? Can you help me please? Thanks in advance Michela

 Tags cyclic, directmapped