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Temperature dependent Non-Newtonian viscosity UDF |
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April 14, 2013, 07:31 |
Temperature dependent Non-Newtonian viscosity UDF
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Join Date: Dec 2012
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Hi, I am trying to write a UDF for Temperature dependent non Newtonian viscosity.. The following UDF works,
#include "udf.h" DEFINE_PROPERTY(u_visc,c,t) { real temp,mu,strain,Q,A,R,n,Y,alpha; Q= 1e5; A=5e13; R=8.314; n=5.86; alpha=0.0118; temp=C_T(c,t); strain=C_STRAIN_RATE_MAG(c,t); Y=strain*exp(Q/(R*temp))/A; mu=pow(Y,(-1/n))+pow((1+pow(Y,(2/n))),0.5); mu=(1/(3*alpha*strain))*log(mu); return mu; } But however when I try to calculate the value of strain rate by the gradients of velocity using the following formula, instead of UDF command C_STRAIN_RATE_MAG(c,t), my solution diverges. strain=(2/3)*(pow(C_DUDX(c,t),2)+pow(C_DVDY(c,t),2)+pow(C_DW DZ(c,t),2)+0.5*pow((C_DUDY(c,t)+C_DVDX(c,t),2)+0.5 *pow((C_DUDZ(c,t)+C_DWDX(c,t)),2)+0.5*pow((C_DWDY( c,t)+C_DVDZ(c,t)),2); strain=pow(strain,0.5); What might be the problem that is causing the solution to diverge??? |
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