Hydraulic jumps: Why do they occur when/where they do?

[Brett0]

Hi guys,

I've been doing some light reading on hydraulic jumps.
For example:


So I've been through the basics, super critical to sub ciritcal etc:
https://en.wikipedia.org/wiki/Hydraulic_jump

So far I understand that the jump occurs at the two points either side of the critical depth, like we see here:
https://en.wikipedia.org/wiki/Hydra...annels-,Energy loss,the equation for ΔE below.

What I don't get is why does the jump occur in the first place? for example in the video above why doesn't the flow just remain super critical? why does the jump happen at the length-wise location that it does? what does that depend on?

Any thoughts?

Brett

 

[jrmichler]

For discussion of hydraulic jumps with less math and more discussion than the Wikipedia hydraulic jump article you referenced above, search a copy (free online) of HDS5 - Hydraulic Design of Highway Culverts.

The text and equations in that document are all believed to be correct, but at least one of the nomograms is wrong by an order of magnitude.