hi, can any body help me to write UDF for turbulent eddy viscosity. i have written UDF but its not working... i am attaching my UDF here. can anyone find where is the mistake in UDF. Its very urgent.

turbulent viscosity is defined as "c-mue*f-mue*k*k/epsilon"

where f_mu is a damping function defined as follows

/*damping functions*/ real re_t(cell_t c,Thread *t) {

return C_R(c,t)*C_UDSI(c,t,TKE)/(C_MU_L(c,t)*C_UDSI(c,t,TSDR));

} real f_mu(cell_t c,Thread *t) {

return 0.09+(0.91+(1/pow(re_t(c,t),3.0)))*(1-exp(pow((-re_t(c,t)/25.0),2.75))); }

DEFINE_TURBULENT_VISCOSITY(eddy_vis,c,t) {

real mu_t;

mu_t=C_R(c,t)*f_mu(c,t)*C_UDSI(c,t,TKE)/C_UDSI(c,t,TSDR);

return mu_t; }

i compiled the UDF with no problems provided that i specified TKE and TSDR. Can you compile the UDF?

hi yah i can compile with out any errors but we are giving iterations then fatal erroe is coming in fluent interface.

Did you define user defined scalars?

yah i have defined for turbulent kinetic energy and specific dissipation rate

Want to start at the beginning - can you compile and run other UDF's that are known to work?

hi yah i compiled all other udfs which i know ..........they are all working well

Hi seeta u seems to be more familiar with FLUENT...can u suggest me which model is the best accurate to simulate flow in ducts of varying cross section like bends, sudden expansion, sudden contraction etc..I hope u r aware of the minor loss coefficient..most the ealier workers who have worked on duct flow analysis they have given some empirical formulae to finding out the loss coefficient called "K"..now the question is using fluent can i get the loss coefficient values in comparision with the ealier empirical formulae...ur help in this regard is highly appreciated..thanks and regards... Purushotham