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Mass flow averaged pressure

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Old   June 28, 2013, 10:01
Question Mass flow averaged pressure
  #1
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Aditya
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Hello
I am using MRFSimple foam to do simulation of a blower. I want to calculate the mass flow averaged pressure on the outflow patch of the geometry. I have tried doing it using "libfieldFunctionObjects.so" in controlDict like :

weight_avg_p
{
type faceSource;
functionObjectLibs ("libfieldFunctionObjects.so");
enabled true;
outputControl timeStep;
outputInterval 1;
log true;
valueOutput true;
source patch;
sourceName wall_inlet;
operation weightedAverage;
weightField phi;

fields
(
p
);


But I get an error saying that the solver has a floating point exception.
Please help me in this regard. If any one has any suggestion on how to calculate the mass flow averaged pressure on a patch it will be very helpful.

Also it says that It cannot find field U when I give U as weightField in the above.
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Old   June 28, 2013, 10:47
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Bernhard Gschaider
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Quote:
Originally Posted by kingmaker View Post
Hello
I am using MRFSimple foam to do simulation of a blower. I want to calculate the mass flow averaged pressure on the outflow patch of the geometry. I have tried doing it using "libfieldFunctionObjects.so" in controlDict like :

weight_avg_p
{
type faceSource;
functionObjectLibs ("libfieldFunctionObjects.so");
enabled true;
outputControl timeStep;
outputInterval 1;
log true;
valueOutput true;
source patch;
sourceName wall_inlet;
operation weightedAverage;
weightField phi;

fields
(
p
);


But I get an error saying that the solver has a floating point exception.
Please help me in this regard. If any one has any suggestion on how to calculate the mass flow averaged pressure on a patch it will be very helpful.

Also it says that It cannot find field U when I give U as weightField in the above.
I your example the patch you average on has "wall" in the name. This does not necessarily mean that phi is 0 there. But it is rather common. And if you divide through a sum of zeros (no matter how many zeros there are) you get a floating point exception
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