Hi all I am using binary diffusion model , I use DEFINE_DIFFUSIVITY to enter mass diffusivity, but I recieve this error: DOMAIN_MULTICOMP_DIFF: undeclared variable my udf is :

#include "udf.h" DEFINE_DIFFUSIVITY(uds_diff,c,t,i) { real d; C_DIFF_L(c,t,0,1)= 12345; d = C_DIFF_L(c,t,0,1); return d; }

How I must use C_DIFF_L(c,t,i,j)in udf?

thanks

you can test

DEFINE_DIFFUSIVITY(alo,c,t,i) { return 12345; }

thanks , but I want to use binary diffusion Di,j not Di,m. I have four species in flow field as H2,O2,H2o,N2.