It is well known the solution of the flow between flat-plates(infinitive plate);

u=0.5*Re*(dp/dx)(y^2-h^2).

Here,h is for half-length of the height between plates. The problem is what is the reference velocity.If the Re=10, and dp/dx=0.01, max velocity is 0.1. Here, I wonder the meaning of the max velocity.

I'd like to use Uavg(=Q/A) as reference velocity. How can I do that?

Thanks ahead.

Max velocity is the one at the center, y=0 in your case. This the velocity which should be used as a reference.