Breaking Solitary Wave Impact on a Vertical Seawall

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.

Keywords

• breaking wave
• solitary wave
• vertical seawall
• wave overtopping
• multi-phase flow
• bubble image velocimetry