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UDF for Herschel-Bulkely model

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Old   June 2, 2009, 12:49
Unhappy UDF for Herschel-Bulkely model
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emad khazal
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Dear All
I would to used Herschel-Bulkely model but my model don't have Yielding Viscosity. Can be any body help me to use model in Fluent for Herschel-Bulkely model only don't have the Yielding Viscosity term. Please, If any body have UDF for Herschel-Bulkely model send me.
Many Thanks for help me
Emad
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Old   June 17, 2009, 09:33
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#include "udf.h"
#include "mem.h"
DEFINE_PROPERTY(cell_viscosity, cell, thread)
{
real mu_lam;
real K=134.0;
real A=0.17;
real gamma;
real strain=C_STRAIN_RATE_MAG(cell, thread);
if(strain==0)
{
gamma=11.126;
}
else
{
gamma=strain;
}
mu_lam=K*pow(gamma,(A-1));
return mu_lam;
}
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Old   June 20, 2009, 02:54
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emad khazal
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Dear Lauren
Meny Thanks for reply. But I have some quations what mean terms K and A, I thanks the Herschel-Bulkley model have fluid yield stress where this term in your eqation. I would like to send me all terms with definetion.

Emad A.
My e-mail Emad_ab74@yahoo.com
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Old   June 22, 2009, 02:02
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A power law index, K consistency
add the yield stress in the definition of mu_lam
mu_lam=K*pow(gamma,(A-1)) + yield_stress/gamma;
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Old   July 6, 2009, 15:26
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emad khazal
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Dear Lauren
Meny Thanks for reply. I don't understand this term
if(strain==0)
{
gamma=11.126;

the number 11.126 from where equation.

Many Thanks again fro help me
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Old   July 20, 2009, 08:16
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i don't know exactly but it will be better to write something like
if strain < strain_min then mu_lam=mu_min
if strain > strain_max then mu_lam=mu_max
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