Zhang, Chengzhao;
(2024)
Numerical modelling of breaking
waves in deep and intermediate
water using a hybrid wave model.
Doctoral thesis (Ph.D), UCL(University College London).
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Abstract
Understanding the characteristics of breaking waves in deep and intermediate water is essential for both air-sea interaction and wave-structure interaction. Recent advancements in experimental studies have revealed that the spectral properties of wave groups can result in different breaking processes. Measuring the flow field details associated with breaking in a physical flume presents significant challenges, necessitating further investigation through numerical modelling to gain a deeper understanding of these physical phenomena. This thesis explores optimal numerical methods for modelling breaking events within the OpenFOAM framework, using a 2D numerical wave tank. It conducts a comprehensive examination of the physical processes underlying breaking, including geometrical deformation, kinematic behaviour, and dynamic characteristics. The initial sections discuss the implementation of initial wave conditions in the OpenFOAM framework and the optimal combination of numerical techniques used for modelling breaking events. The generation of breaking waves using Stokes wave theories is initially employed to test the applicability of the numerical model based on OpenFOAM. Subsequently, a hybrid model that couples the Lagrangian wave model with the VOF model is developed to simulate breaking wave groups resulting from dispersive focusing, with a spectrum related to a modelled sea state. The numerical results obtained through the hybrid wave model are validated against experimental data, demonstrating a high level of accuracy. The following sections present the effects of four different turbulence models on breaking modelling, which lead to variations in kinematic behaviour, energy dissipation due to breakers, and associated breaking parameters. Subsequently, the discussion centres on various breaking scenarios of the breakers due to dispersive focusing with different phase shifts. Numerical cases are conducted both with and without turbulence models, and the breaking criteria are revisited, including geometrical, kinematic, and dynamic criteria based on the specific wave cases examined. In addition, an eddy viscosity model is used for interpretation of breaking wave parameters based on our present tests with a set of phase distributions. These findings demonstrate that neglecting the spectral properties of wave groups and the impact of turbulence models can lead to misinterpretations of breaking criteria and breaking properties.
| Type: | Thesis (Doctoral) |
|---|---|
| Qualification: | Ph.D |
| Title: | Numerical modelling of breaking waves in deep and intermediate water using a hybrid wave model |
| Language: | English |
| Additional information: | Copyright © The Author 2024. Original content in this thesis is licensed under the terms of the Creative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0) Licence (https://creativecommons.org/licenses/by-nc/4.0/). Any third-party copyright material present remains the property of its respective owner(s) and is licensed under its existing terms. Access may initially be restricted at the author’s request. |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science > Dept of Civil, Environ and Geomatic Eng |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10195818 |
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