Karthik R
Hello,nAre you obtaining the mass flux at a certain boundary? Or on the entire domain? Is this the entire UDF you are using?nThere is UDF in the Fluent customization manual which achieves a similar objective. Here is the link to this (Example you use this as the template and modify it to suit your needs (perhaps, rejig it for the macro F_FLUX you wish to use)?nKarthiknn