Will water flowing through a funnel be accelerated more by a "curve-walled" funnel rather than a "straight-walled" funnel?
The aim is to avoid sudden changes in flow direction, which can lead to a "vena contracta" that will reduce the effective diameter of the funnel.
Potential energy must be smoothly converted to kinetic energy as the fluid falls through the funnel. Cross-section must change by the same ratio per unit travel along the funnel.
I believe the optimum flow will be with an exponential horn, like a reversed loud hailer, so the fluid is accelerating smoothly along the channel, without sudden changes in fluid wall pressure.
Here is a short video demonstrating what I am talking about.Thanks for the description. That looks like an interesting toy. Does the water come out in a relatively collimated jet? I'm sure that turbulent flow is the enemy here. But it may be very subtle. I may cut up some "larger" plastic bottles and hit the pool !