I have built water channel 3.5 meter long, all horizontal, I added a glass test section at end of channel for laser measurements, I added a contraction and flow conditioner in the start of water channel to get fully developed flow, I used LDV to measure velocity of flow profile starting from top of pipe to bottom, all measurements are skewed, that flow velocity measurements are higher above the center of pipe. the pipe ID is 38 mm , I measure at each 2 mm, that is 19 measurements in total, Can someone help me why the flow velocity measurements are skewed to top that is higher above pipe center and lower below center of pipe