how to get the average values on parallel channels

Hello everybody. Now I simulate the hydynamics of the distributor with parrallel channels. I want to get the mean velocity values in the middle of each channels. I try to use the 'cut plane' on the postprocess, but this operation will create the surface for all parrallel channels. So it doest not get the value for each channel. The geometry is like the attached document.

Thank you for your help!!