It basically signifies a loss of energy. You can think of it in the context of collisions, except with a continuous distribution of fluid instead of a discrete distribution of objects.
We know that momentum (mv) is always conserved. In this context, we can replace mass with cross-sectional area, because mass in a given cross-section is proportional to the area. V is flow velocity in length/time. So momentum is flow in length^3/time.
Energy is 1/2mv^2. If you lose energy, mv is constant and m*v^2 decreases, meaning that v must decrease and m must increase. In this context, that means that the flow is slower with a larger area. This corresponds to an "inelastic collision". In fluid dynamics this is a hydraulic jump.
In this situation, most of the energy loss is near the surface, so you end up with moving hydraulic jumps on top of a laminar flow. This doesn't really happen in natural situations, because riverbeds generally aren't this smooth.
This doesn't really happen in natural situations, because riverbeds generally aren't this smooth.
When I first noticed it, I was reminded of waterfalls, especially the way they were portrayed in 8 bit games. [1] It turns out not to be that easy to find a good real world example, at least not without watching hours of waterfall footage, but this one [2] does an acceptable job showing it. I have no idea if this could be caused by the same or at least a similar mechanism.
We know that momentum (mv) is always conserved. In this context, we can replace mass with cross-sectional area, because mass in a given cross-section is proportional to the area. V is flow velocity in length/time. So momentum is flow in length^3/time.
Energy is 1/2mv^2. If you lose energy, mv is constant and m*v^2 decreases, meaning that v must decrease and m must increase. In this context, that means that the flow is slower with a larger area. This corresponds to an "inelastic collision". In fluid dynamics this is a hydraulic jump.
In this situation, most of the energy loss is near the surface, so you end up with moving hydraulic jumps on top of a laminar flow. This doesn't really happen in natural situations, because riverbeds generally aren't this smooth.