Start Date

2018 1:50 PM

Creative Commons License

Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 License.

Abstract

In an estuary, a tidal bore is a hydraulic jump in translation generated at the leading edge of the tidal wave during the early flood tide under spring macro-tidal conditions in a narrow funnelled channel. After formation, the bore is traditionally analysed as a hydraulic jump in translation and its leading edge is characterised by a breaking roller for Fr1 > 1.3–1.5. The roller is a key flow feature characterised by intense turbulence and air bubble entrainment. Herein detailed air-water flow measurements were conducted in breaking bores propagating in a large-size channel. The data showed a relatively steep roller, with a short and dynamic bubbly flow region. The results were used to validate a Computational Fluid Dynamics (CFD) model of breaking bores. The instantaneous void fraction and bubble distribution data showed systematically a lesser aeration region in the physical model, compared to the numerical data. The differences may be linked to some limitation of the CFD modelling.

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May 17th, 1:50 PM

Air Bubble Entrainment in Breaking Bores: Physical and Numerical CFD Modelling

In an estuary, a tidal bore is a hydraulic jump in translation generated at the leading edge of the tidal wave during the early flood tide under spring macro-tidal conditions in a narrow funnelled channel. After formation, the bore is traditionally analysed as a hydraulic jump in translation and its leading edge is characterised by a breaking roller for Fr1 > 1.3–1.5. The roller is a key flow feature characterised by intense turbulence and air bubble entrainment. Herein detailed air-water flow measurements were conducted in breaking bores propagating in a large-size channel. The data showed a relatively steep roller, with a short and dynamic bubbly flow region. The results were used to validate a Computational Fluid Dynamics (CFD) model of breaking bores. The instantaneous void fraction and bubble distribution data showed systematically a lesser aeration region in the physical model, compared to the numerical data. The differences may be linked to some limitation of the CFD modelling.