Master of Engineering Science
Mechanical and Materials Engineering
Ogden, Kelly A.
Hydraulic jumps at the interface of stratified rotating fluids are studied. The flow is de- fined with continuous density and velocity profiles, with the velocity in each layer changing (upstream shear). The study is conducted in jumps defined by an imposed velocity transition, and jumps developing over a topography.
The numerical simulations conducted showed the qualitative structure of the flow changing in the cross-width direction, as well as the size and amount of turbulence of the jumps. Mixing in these jumps was shown to increase towards the side of the domain where the jumps were larger and more turbulent. The qualitative structure of the flow remained unchanged in the cases with topography. The amount of mixing was also shown to decrease as rotation values increase. In the simulations with topography, the size of the jumps and the amount of mixing were shown to depend on upstream shear developing over the topography.
Summary for Lay Audience
Hydraulic jumps are a dissipative phenomenon in which a change in the depth of a layer of the flow causes the flow to slow down. This work focuses on flows with two layers of different densities. The hydraulic jump happens when there is a sudden contraction/expansion in one of the layers.
The effects of Earth’s rotation on the formation of such hydraulic jumps are investigated in this work. Previous work has focused on rotating flows with constant density or flows where the upper layer (lower density portion) is stagnant. Here, hydraulic jumps form in rotating flows where density changes between two layers moving with different velocities. Numerical sim- ulations are conducted that showed the flow banking and the structure of the hydraulic jumps changing across the width of the channel. Mixing in the jumps also changed across the width of the domain increasing towards the direction where the jumps were larger and more turbulent.
Different theories were compared against results from the simulations. These comparisons showed that the theories reasonably predict the behaviour of the jumps if the lateral movement in the flow is considered. More realistic simulation, in which the jumps develop over a topog- raphy, bridged the gap between the idealized cases and natural channel flows. A clear trend in the change in the amount of mixing with rotation was found in the simplified simulations – the amount of mixing decreased as rotation got stronger.
Mucaza, Muveno Pascoal Elias, "Complicating factors in hydraulic jumps: the effects of earth's rotation" (2021). Electronic Thesis and Dissertation Repository. 8166.
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