Flow Transitions (reduction/expansion)

[rjw57]

I am in the process of developing a mixing stage for a process I am working on. To minimize the overall length in the process flow direction, I have chosen to use mixing elements that are smaller in diameter than the upstream/downstream piping. I am trying to determine a way to minimize the effect of the flow stream reduction/expansion with the use of baffles (I really want, again, to minimize the overall length required for this unit operation). Has anyone ever seen any information related to the sizing/placement/design of baffles to help in distributing the flow at the stepped inlet and outlet of the mixing stage (6" to 3" to 6")? I cannot afford the length required by a "perfect" reducer geometry on both ends of the mixing stage.

rjw57