Abstract
In the present paper, a comparative study of different cylindrical and conical substructures was performed under breaking wave loading with the open-source Computational Fluid Dynamics (CFD) package OpenFoam capable of the development of a numerical wave tank (NWT) with the use of Reynolds-Averaged Navier–Stokes (RANS) equations, the k-ω Shear Stress Transport (k-ω SST) turbulence model, and the volume of fluid (VOF) method. The validity of the NWT was verified with relevant experimental data. Then, through the application of the present numerical model, the distributions of dynamic pressure and velocity in the x-direction around the circumference of different cylindrical and conical substructures were examined. The results showed that the velocity and dynamic pressure distribution did not change significantly with the increase in the substructure’s diameter near the wave breaking height, although the incident wave conditions were similar. Another important aspect of the study was whether the hydrodynamic loading or the dynamic pressure distribution of a conical substructure would improve or deteriorate under the influence of breaking wave loading compared to a cylindrical one. It was concluded that the primary wave load in a conical substructure increased by 62.57% compared to the numerical results of a cylindrical substructure. In addition, the secondary load’s magnitude in the conical substructure was 3.39 times higher and the primary-to-secondary load ratio was double compared to a cylindrical substructure. These findings demonstrate that the conical substructure’s performance will deteriorate under breaking wave loading compared to a cylindrical one, and it is not recommended to use this type of substructure.
Highlights
Marine renewable energy was generating considerable interest on a worldwide scale due to the effects of climate change and energy demand leading to offshore wind turbine substructures (OWTs)
Based on the simulations performed and the observations made, it is not recommended to use a conical substructure in place of a cylindrical one
The numerical results of the free surface elevation, primary wave load, and secondary load were compared to available experimental data provided by Irschik et al [5] to validate the numerical model
Summary
Marine renewable energy was generating considerable interest on a worldwide scale due to the effects of climate change and energy demand leading to offshore wind turbine substructures (OWTs). Turbulence model and the Volume of Fluid (VOF) method to examine the characteristics of higher-harmonic breaking wave forces and secondary load cycles on a single vertical circular cylinder at various Froude numbers by modifying the diameter and incident wave conditions. Kamath et al [11] utilized the k–ω turbulence model and the level set method and analysed the wave structure interactions among a single monopile at varying breaker locations with plunging breaking conditions They found that the wave breaking position was correlated with the breaking wave forces on the substructure. Numerical simulations of different cylindrical and conical substructures were performed in a developed Numerical Wave Tank (NWT) applying the Reynolds Averaged Navier Stokes (RANS) equations with the use of the k-ω SST turbulence model and the VOF method in OpenFoam. Based on the simulations performed and the observations made, it is not recommended to use a conical substructure in place of a cylindrical one
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