change dissipation rate of kinetic energy in k-w SST turbulence model
 

Hello all,
I want to modify the dissipation rate of kinetic energy equation by UDF. Which macro can be used? Is it possible to use DEFINE_SOURCE for definning new dissipation rate?

Actually, I must change the formulation of dissipation rate of k-equation and then, Fluent uses the modified dissipation term instead of itselfs. My turbulence model is k-w SST and I just manipulate Y_k (dissipation rate of k).
Original: Y_k=ro*beta_s*k*w;
Modified: Y_k=ro*beta_s*k*w/delta; (delta is wall distance)

It would be appriciated if anyone makes a comment to how I do this task.