Numerical Investigation on the Interaction between a Tsunami-like Solitary Wave and a Monopile on a Sloping Sandy Seabed

Abstract

An integrated numerical model was developed to investigate the interaction between a tsunami-like solitary wave and a monopile on a sloping sandy seabed in this study. The solitary wave motion is governed by the RANS equations with the k-ε turbulence model. The porous sloping sandy seabed is governed by Biot’s equation (u-p approximation). The solitary wave is validated with previous experimental data. Meanwhile, a further comparison of solitary wave scattering by the monopile is carried out to verify the numerical model. Then, the effects of different monopile locations were examined in investigating the solitary wave–monopile interaction problem. The velocity magnitudes and the free-surface elevation changes in the solitary wave around the monopile are investigated at various monopile locations. In addition, the response of the sloping sandy seabed and monopile under the solitary wave are examined. The numerical results demonstrate the accuracy of the current method in simulating solitary waves and wave height variation around monopiles. Wave run-up is observed in front of the monopile, with a high-velocity forward-moving water jet forming behind it. The maximum fluid velocity, wave run-up height in front of the monopile, excess pore water pressure (EPWP), and bending moment of the monopile increase as the monopile approaches the shoreline. However, at the closest location to the shoreline, due to the strong dynamic interaction between the solitary wave and the monopile, significant wave shoaling and breaking are observed, resulting in a slight decrease in the wave force acting on the monopile.