Studying hydraulic jump usually assumes liquid pressure to be hydrostatic pressure.
Hydraulic jump occurs if the pressure gradient becomes increasingly adverse as the flow
proceeds downstream. As sketched in figure 16(a), an increased liquid height (^ > h0 )
increases hydrostatic force (= pressure x height) against the downward flow, and decreases
downward velocity to satisfy conservation of momentum and mass. However, liquid height
at the downstream location can also be less than that at the upstream location, as illustrated
in figure 16(b). Hydrostatic force decreases whereas velocity increases. Provided that the
Froude number, U„ / ghn > 1, hydraulic jump occurs because of h / hn > 1 . As Froude 2 0 0 1 0 number Uq / ghp < 1, the height ratio ^ / h0 < 1. Surface tension can also play a role in
hydraulic jump , as observed the occurrence of polygonal patterns from breaking axial symmetry of a circular hydraulic jump.