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Flat plate breakwater is widely studied for wave dissipation because of its good performance near the water surface and low cost in deep-water areas. However, a fixed flat plate suffers from low adaptability problems as a result of various incoming waves. This paper studies the wave dissipation of a submerged movable flat plate against regular waves, in which the plate is actively controllable to maximize the wave dissipation ability. Simulations of the interaction between regular and irregular waves and the actively controlled plate are conducted in an in-house solver, and the deep reinforcement learning method is applied to control the plate motion.

Introduction

Ocean waves usually create a huge impact on the numerous coastal, offshore, and marine structures, resulting in structural damage and destruction. Over the past few years, a significant amount of effort has been put into studying how ocean waves interact with structures to protect coastal and offshore areas. Researchers have developed and analyzed many types of breakwaters to be used under different environmental conditions in recent decades. Among various breakwaters, plate-type breakwaters are favorable because most of the wave energy is concentrated near the water surface. Lo and Liu (2014) investigated the wave scattering of a solitary wave traveling over a submerged horizontal plate experimentally, numerically, and analytically, where the fluid field, surface elevation, and wave loads were calculated and compared. Koraim (2013) studied the hydrodynamic efficiency of the breakwater consisting of one or more horizontal rows of half pipes suspended on supporting piles, showing that the proposed breakwater system was more efficient than the smooth plate type by about 5% to 25%. Wang et al. (2016) proposed a kind of arc plate breakwater made up of several arc plates suspended on supporting piles and explored the wave damping performance of the breakwater. The performance of the arc plate breakwater was shown to be better than that of a similar breakwater with several horizontal plates. Gu and Zhang (2016) and Gu et al. (2017) studied the wave-dissipating performance of a twin-plate breakwater under the consideration of an incident wave angle, relative plate length, and wave height based on physical model tests.

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