A method and system for controlling a velocity field in a processing system is described. In an exemplary embodiment described, the system includes a multi-outlet exhaust manifold having three or more outlets coupled to the processing system adjacent a surface of a substrate to be process. The three or more outlets are located adjacent the substrate in order to provide for a uniform flow of fluid above the surface of the substrate. Additionally, the flow of fluid through the three or more outlets is cyclically and sequentially alternated.