The equation relating the pre-and post-hydraulic jump flow depths for rectangular channel is given by

Assume standard nomenclature of the terms used above.

Question

Question

This question was previously asked in

BPSC AE Paper 6 (Civil) 25 March 2022 Official Paper

Answer 1

Concept:

Hydraulic jump: Whenever supercritical flow merges into subcritical flow then to reduce the energy a jump is formed, called a hydraulic jump.

For a rectangular frictionless channel, both depths are related as:

\(\frac{{{{\rm{y}}_2}}}{{{{\rm{y}}_1}}} = \frac{1}{2}\left[ {\sqrt {1 + 8{{\rm{F}}_1}^2} - 1} \right]\)

Froude number (F) = \(\sqrt {\frac{{{{\rm{Q}}^2}{\rm{T}}}}{{{\rm{g}}{{\rm{A}}^3}}}}\)

Where,

Y₁= Pre jump depth, Y₂= Post jump depth, F₁= Froude Number before jump, Q = Discharge, T = top width, and A = area of flow

Length of hydraulic jump (L) is calculated empirically by: L = 7 × (Y₂- Y₁)