[syllablehq]

Hmm, is it possible that this could be partly caused because the water gets sucked not just directly down the pipe, but around the lip of the pipe opening... and one edge of the pipe opening is further away from the center axis of rotation (of the whole sprinkler) than the other end of the pipe opening. I'd think that whether or not this would have an effect could be easily tested by varying sizes of the pipe opening or how far away the opening was from the center to see if it made a difference -- even if the bends in the pipe were the same (the authors seem to attribute the whole effect to the bends in the arms).

[syllablehq]

I'll add that this could become particularly important in the 4d case once the sprinkler starts moving. Cause when it's still, the pressure gradient will create a partial-torus like shape around opening, but once it starts rotating, the outer side (rotating around the sprinkler's axis) of the 4D version of this shape has a larger diameter than the inside. So the inner side will be more affected by the environmental water's momentum state than the outside which has more water mass in it's scope rotating around the sprinkler axis.