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-   -   UDF for Herschel-Bulkely model (http://www.cfd-online.com/Forums/fluent-udf/65059-udf-herschel-bulkely-model.html)

emad June 2, 2009 12:49

UDF for Herschel-Bulkely model
 
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

laurentb June 17, 2009 09:33

#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;
}

emad June 20, 2009 02:54

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

laurentb June 22, 2009 02:02

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;

emad July 6, 2009 15:26

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

laurentb July 20, 2009 08:16

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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