A Numerical Study of Hydraulic Jump and Mixing in a Stratified Channel With a Sill

by Ping Chen, McGill Univ, Montreal, Canada,
R. Grant Ingram, McGill Univ, Montreal, Canada,
Jianping Gan, McGill Univ, Montreal, Canada,

Document Type: Proceeding Paper

Part of: Estuarine and Coastal Modeling


An x-z plane two dimensional primitive equation model is used to study sill effects in a narrow channel. The aim is to examine the generation of internal bores/waves, hydraulic jumps and associated mixing processes in continuously stratified water under tidal forcing. Different cases with various sill heights, tidal currents and stratifications are considered. Results of these cases show complicated vertical structure of velocity and salinity, which differ from layer models but are similar to some observations. For selected cases of interest, supercritical conditions are reached at around maximum tidal current (both flooding and ebbing) in the sill region. Hydraulic jumps form at the location of the transition point from supercritical to subcritical, which is at lee side of sill and is consistent with layer theory in terms of composite Froude numbers. Internal bores will form at the jump location, propagate upstream across the sill and evolve into solitons when the current slackens. High turbulent kinetic energy, and strong mixing, occur not only in the jump but also in an extended area further downstream, where strong horizontal velocity shear and vertical velocity exist as a result of the jump. It is also found that unstable points occur in the upstream portion of the jump.

Subject Headings: Tides | Reefs and sills | Hydraulic jump | Water stratification | Hydraulic models | Water waves | Numerical models

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