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-   -   crosspowerlaw nu0 and nuinf, which is bigger? (http://www.cfd-online.com/Forums/openfoam/111400-crosspowerlaw-nu0-nuinf-bigger.html)

sharonyue January 6, 2013 05:17

crosspowerlaw nu0 and nuinf, which is bigger?
 
return (nu0_ - nuInf_)/(scalar(1) + pow(m_*strainRate(), n_)) + nuInf_;

According to this, nu0 is the kinematic viscosity when the stress rate tends to zero. and nuinf is the one that the stress rate tends to infinate.

Quote:

transportModel CrossPowerLaw;

CrossPowerLawCoeffs
{
nu0 nu0 [ 0 2 -1 0 0 0 0 ] 0.01;
nuInf nuInf [ 0 2 -1 0 0 0 0 ] 10;
m m [ 0 0 1 0 0 0 0 ] 0.4;
n n [ 0 0 0 0 0 0 0 ] 3;
}
Should it be nu0 bigger than nuinf?
https://www.sharcnet.ca/Software/Flu...nn_carreau.png
but in the tutorial case is opposite.

sharonyue January 6, 2013 05:59

Maybe I figure it out, in this case n>3 which indicate its Shear thickening. I will validate it soon.

Tushar@cfd January 7, 2013 00:59

nu_0 is lesser in this case then the nu_inf, as n >1.

sharonyue January 17, 2013 09:35

Quote:

Originally Posted by Tushar_Mtechcfd (Post 400396)
nu_0 is lesser in this case then the nu_inf, as n >1.

Hi Tushar
Code:

m m [ 0 0 1 0 0 0 0 ] 0.4;
Does this m mean consistency index? but consistency index's dimension is not this. I am confused.

sharonyue March 7, 2013 03:49

Quote:

Originally Posted by sharonyue (Post 402441)
Hi Tushar
Code:

m m [ 0 0 1 0 0 0 0 ] 0.4;
Does this m mean consistency index? but consistency index's dimension is not this. I am confused.

Does anybody know whats the meaning of m?

Tushar@cfd April 1, 2013 01:29

Quote:

Originally Posted by sharonyue (Post 412190)
Does anybody know whats the meaning of m?


m actually is a natural time.
I think you are trying to co-relate with powerlaw but this isn't correct. The mentioned model is CrossPowerLaw and it is different from PowerLaw. Try looking some more literature on it.

Best of luck.
:)

sharonyue April 1, 2013 03:44

2 Attachment(s)
Quote:

Originally Posted by Tushar@cfd (Post 417480)
m actually is a natural time.
I think you are trying to co-relate with powerlaw but this isn't correct. The mentioned model is CrossPowerLaw and it is different from PowerLaw. Try looking some more literature on it.

Best of luck.
:)

Woo,Tushar,

That really helps me alot.I check it out and find its natural time from one paper.

But in another paper it said this:

Why is it so different?

Thanks a lot!

Regards,

Tushar@cfd April 1, 2013 08:13

Quote:

Originally Posted by sharonyue (Post 417492)
Woo,Tushar,

That really helps me alot.I check it out and find its natural time from one paper.

But in another paper it said this:

Why is it so different?

Thanks a lot!

Regards,

Well sharonyue, nice question.
I think, this may be because we are trying to match a range as mentioned in the 2.jpg
It's just a guess, I am also not sure.

Do let us know if you happen to find the answer.


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