I defined a species diffusivity using "DEFINE_DIFFUSIVITY" and i try to use this species diffusivity value in my UDF. I have confused about how to use "C_DIFF_L(c,t,i,j)". Where, "i" denotes the species "i" that I want to use and "j" denotes what? How can I obtain the species "i" diffusivity by "C_DIFF_L(c,t,i,j)"? Thanks.

may be you can help naima

I like te difine the UDS Diffusivity with a UDF but i have some problems. so, I used the udf given by fluent :

# include "udf.h" DEFINE_DIFFUSIVITY(mean_age_diff, c, t, i) { return C_R(c,t) * 2.88e-05 + C_MU_EFF(c,t) / 0.7; }

also with this udf(fluent) Ihave the same error : Error: C:\work\tt.c: line 1: parse error. I'd appreciate your help, think you

Hi,I think you should begin your "DEFINE_DIFFUSIVITY" at the first column. Don't leave blank in front of this UDF and then try it again.

Thank you a lot for your response, you know, the problem is I don't write this UDF, it is from the chapter 4 page 4-17 "define Macro" in the documentation of Fluent, I just copy and past the sentenses, like naima did. Sincerly Yours