Flow through channel contraction
Changes in flow regime as the flume passes through a reach contraction on an steep open channel. Upstream (supercritical) current slows down (and becomes subcritical) in order to adjust its specific energy and pass through critical depth. Hydraulic jump witness this transition.
Rapid velocity variations in the vertical are combined with significant horizontal variation.

Flow over broad-crested weir
A broad-crested weir is used to measure the discharge on open channels as weir height is great enough as to cause critical flow over the weir crest. Upstream and downstream corners are rounded to avoid flow separation.

V-Notch Weir
V-notch weir. This hydraulic tool is particularly effective at measuring low flow rates in open channel and laboratory equipment.
It’s a sharp-crested type such that the water springs clear of the crest.