Dear Ketan, Many thanks for your reply. Basically I want to get the averaged velocity, rms velocities and shear stress where I got two questions. 1. Once the subroutines were writen in usr file, Is calling avg_all still needed? In other words, the post-processing is done after longtime running, and usr file is changed instead of calling avg_all, isn't it? 2. After trying the subroutines you provided, there isnt no files generated in the directory. Can you give me more infomation about the averaging process. Best wishes, ZJ