In a filled(steady state) pipe, nothing changes
In a completely steady state fluid, which is assumed when you apply Bernoulli equation,
there will actually be no effect.
What I mean by that is, the speed will only be different for the different pipes when the water is just initially going through and coming out,
but once it is in a state where it completely fills the pipe at all points in time, the speeds will more or less be the same(within experimental error).
[This can be proven using Bernoulli's equation Area1.Volume1=Area2.Volume2 which works regardless of the shape of the pipe]
But this'll only work if you create a steady state fluid, practically managing that may be a little difficult.
Hope I could help.
Thanks
