In this case, the circular pipe would have some length L, diameter D, and would be attached to the centre of some rectangular reservoir. There is no pump, just gravity causing the flow. How would you calculate the average velocity in the pipe? Also, in a second set-up with an identical reservoir but pipe of different diameter, is the average velocity the same?
The reservoirs are assumed to be identical, open and rectangular reservoirs in both situations. The pressures on the top of the reservoirs and orifice at the end of the pipes are assumed to be at atmospheric pressure (or simply equal pressures, I'm trying to understand how the diameter change affects the flow rate and flow velocities in the pipes themselves)
Edit: I believe the velocities will be the same (and since Q = AvK), so volumetric flow rates will be different, and the time to drain will be different. Someone else said that this is not the case and the volumetric flow rates will be equivalent, although I don't see why they would be. This isn't a homework question, I'm just trying to understand the concept here! This question came about after discussing the pipe diamteres used in some toilets in america vs europe.