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-   -   direct map vs cyclic (http://www.cfd-online.com/Forums/openfoam/83065-direct-map-vs-cyclic.html)

nimasam December 13, 2010 16:39

direct map vs cyclic
 
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;
}
}
}

herbert December 14, 2010 05:52

Quote:

Originally Posted by nimasam (Post 287279)
are my boundaries corrects;) ?

I think so.
Quote:

Originally Posted by nimasam (Post 287279)
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


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