# non newtonian viscosity problem

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 June 27, 2012, 07:21 non newtonian viscosity problem #1 Member   Dr. Moloy Kumar Banerjee Join Date: Jun 2011 Posts: 71 Rep Power: 7 Dear all, I am simulating the problem of blood flow through an artery in 2D considering laminar flow. For this I am using the Walburn and Scneck model to define the blood viscosity using the equation: mu_lam=K*(strain)^(n-1), where K=14.67*10^(-3) and n=0.7755. In order to define the viscosity I am using the following UDF: #include "udf.h" DEFINE_PROPERTY(cell_viscosity_power_law,c,t) { double mu_lam; double strain; double muinf = 14.67e-3; double n = .7755; strain = pow(C_DUDX(c, t),2)+ pow(C_DVDY(c, t),2)+ 2*pow(C_DUDY(c, t)+ C_DVDX(c, t),2)+ 2*pow(C_DUDZ(c, t),2)+ 2*pow(C_DVDZ(c, t),2); strain = pow(strain, 0.5); strain =fabs(strain); mu_lam=muinf*pow(strain,n-1); return mu_lam; } But, once I try to solve it the solver gives the error: Divergence detected in the AMG solver. Please help me....

 July 3, 2012, 16:47 #2 Member   Casey Join Date: Jun 2009 Posts: 96 Rep Power: 9 You should repost this in the UDF section of the forum. You will likely get more help. presidentmamun likes this.

 July 3, 2012, 16:48 #3 Member   Casey Join Date: Jun 2009 Posts: 96 Rep Power: 9 I think it is because when Strain = 0, you will be dividing by zero. Try adding an if statment in there that says if strain is below some value than mu_lam = some large value... or make stain = pow(C_DU...) + 1x10^(-12), presidentmamun likes this.

 July 4, 2012, 02:51 #4 Member   Dr. Moloy Kumar Banerjee Join Date: Jun 2011 Posts: 71 Rep Power: 7 Thanks for the reply. It works properly.

 July 5, 2012, 15:47 #5 Member   Casey Join Date: Jun 2009 Posts: 96 Rep Power: 9 no problem.

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