Unsteady state simulation

ashish

Hi, I am a new user of Fluent. I am trying to run an unsteady simulation. But to make sure I'm using the correct parameters, I am simulating a very simple geometry (laminar flow between two parallel plates). My question is, at time t=0, there is no fluid inside the plate region (in at left, out at right) and say it takes a time t_f for the fluid to reach outlet. How can I specify these conditions in Fluent? Even at time of say 1e-5, it shows some flow at the outlet (with flow through some of the faces to be reversed). Can somebody help me in this matter?