I think this link will help https://www.google.co.in/url?sa=t&source=web&rct=j&url=http://www.southampton.ac.uk/~nwb/lectures/GoodPracticeCFD/Articles/Turbulence_Notes_Fluent-v6.3.06.pdf&ved=2ahUKEwiohIX3qqvfAhVZVH0KHeAjDMIQFjAJegQIBRAB&usg=AOvVaw2yiWH7b5a9DS---mq3oXcN