Can random eddy lifetime give better result

Douglas

Hi,

I am currently working on a manhole model. I would like to know the residence time of neutrally buoyant particles in the manhole that filled with water. I used the stochastic particle tracking model to solve the problem. But I encountered a problem that should I use 'random eddy lifetime' to describe the turbulent motion of the particles. In the Fluent Manual it doesn't state when should it be used and its major benefit. Can anyone help me?

Many thanks, Douglas