Abstract
Wave interactions with vertical and sloping seawalls are indeed complicated, especially for the impacts due to breaking waves, which are unsteady, turbulent and multi-phase. Available studies successfully measured the impact pressure due to waves acting on seawalls, whereas the associated flow velocity and turbulence characteristic received limited attention, indicating that the momentum of such violent free-surface flows cannot be determined. In this study, new experiments were carried out in a laboratory-scale wave flume using a non-intrusive image-based measuring technique (bubble image velocimetry, BIV) to measure the flow velocities due to a shoaling solitary wave impinging on and overtopping a vertical seawall. By varying the wave height of solitary waves, the breaking point of a shoaling wave can be changed. As such, the impact point of a breaking wave in relation to the seawall can be thereby adjusted. Considering the same still-water depth, two wave height conditions are studied so as to produce different levels of aerated flows. Effects of high- and low-aerated cases on free surface elevations, flow velocities and turbulence characteristics are presented so as to develop a better understanding of wave-structure interactions. More specifically, the maximum velocities and turbulence intensities at different evolutionary phases are identified for these two cases.
Highlights
Coastal structures, such as levees and sea dikes, have long been used as coastal defenses to withstand wave impacts and protect the coastline
Two scenarios were considered through varying the wave heights of of solitary waves to further change the impinging point of breaking waves in relation to solitary waves to further change the impinging point of breaking waves in relation to the the vertical wall, which resulted in high-aeration and low-aeration flows for the comparvertical wall, which resulted in high-aeration and low-aeration flows for the comparisons isons of free surface elevation, mean flow velocity and turbulence intensity
Breaking waves impinging on and overtopping vertical seawalls have been investigated over decades, but there is still a limited understanding of the related wave hydrodynamics in terms of flow velocity and turbulent kinetic energy
Summary
Coastal structures, such as levees and sea dikes, have long been used as coastal defenses to withstand wave impacts and protect the coastline. To the clarify the effects of breaking with various onstructure, the structure, et al. Hattori et al [10] performed laboratory experiments to measure impact pressures due to waves with different overturning points in relation to the vertical wall. This is the main restriction of such techniques for breaking waves with entrained air bubbles [20] This might be one of the main reasons that, to the best knowledge of the author, a detailed measurement and insightful investigation of flow velocity and turbulence due to breaking waves impinging on and overtopping a vertical seawall is limited. Using an image-based flow visualization technique, it is expected to improve the understanding of wave hydrodynamics in the vicinity of a vertical seawall due to violent breaking-wave impacts Such data can be further 4used of 16 to validate analytical solutions [24] and multi-phase numerical models [25]
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