Supercritical Flow over Sills at Incipient Jump Conditions

A laboratory investigation has been conducted to study the conditions mainly responsible for the stabilization and prediction of the hydraulic jump in a rectangular, horizontal-bed channel with a square-shaped bottom sill at the incipient jump condition (i.e., at the verge of formation of the jump, however, without it actually forming). A theoretical analysis based upon the momentum and continuity principles has been carried out. A formula for the design of the sills, when the ratio of the sill height to the upstream depth is smaller than 1.25, is suggested. A relationship between the drag experienced by the sill and the upstream Froude number is also given. The theoretical formulation has been checked by laboratory experimentation.