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Old   July 9, 2014, 04:16
Default Q criterion question
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Greetings!

Excuse me if this question has already been answered, however I searched a lot and didn't find something on the forum.

My question is about the Q field that is created by the OpenFoam Q utility and whether this field is the standard or the normalized Q criterion.

Furthermore, in case that it is not the normalized one, what should it be divided by, in order to achieve normalization?

Thanks a lot in advance,
Greg
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Old   July 9, 2014, 05:31
Default Q criterion = 0.5*(sqr(tr(gradU)) - tr(((gradU)&(gradU))))
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Fabian Roesler
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Hi

I did not use the Q criterion before but from the Q.C file I get the following:

Quote:
Calculates and writes the second invariant of the velocity gradient tensor.

Q = 0.5*(sqr(tr(gradU)) - tr(((gradU)&(gradU)))) [1/s^2]

The -noWrite option just outputs the max/min values without writing
the field.
As the file is very short, there should not happen much after this calculation.

Cheers

Fabian
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Old   July 11, 2014, 05:50
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Many thanks for the reply Fabian.

I will also try to find more info about the normalization.

Cheers,
Greg
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Old   February 23, 2016, 06:07
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Quote:
Originally Posted by greg.cfd View Post
Many thanks for the reply Fabian.

I will also try to find more info about the normalization.

Cheers,
Greg

Hello Greg,

Did you find out how to get the normalized Q criterion in OpenFOAM ?

Thanks in advance

Paul
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