CFD modeling of tidal bores: development and validation challenges

Abstract

A tidal bore is a natural estuarine phenomenon forming a positive surge in a funnel shaped river mouth during the early flood tide under spring tide conditions and low freshwater levels. The bore propagates upstream into the lower estuarine zone and its passage may induce some enhanced turbulent mixing, with upstream advection of suspended material. Herein the flow field and turbulence characteristics of tidal bores were measured using both numerical (CFD) and physical modelling. This joint modelling approach, combined with some theoretical knowledge, led to some new understanding of turbulent velocity field, turbulent mixing process, Reynolds stress tensor, and tidal bore hydrodynamics. The numerical CFD tool Thétis was used herein. Thétis is a CFD model using the volume of fluid technique (VOF) to model the free-surface and Large Eddy Simulation technique (LES) for the turbulence modelling. Physical data sets were used to map the velocity and pressure field and resolve some unusual feature of the unsteady flow motion. A discussion will be provided to explain why a detailed validation process is crucial, involving a physical knowledge of the flow. Comparison of the numerical model results and experimental data over broad ranges of conditions for the same flow is mandatory. The validation process from 2D to 3D will be commented and difficulties will be highlighted.

Hybrid modelling of low velocity zones in box culverts to assist upstream fish passage

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Statistical analysis methods for transient flows – the dam-break case

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