A Model Coupling CFD and DRL: Investigation on Wave Dissipation by Actively Controlled Flat Plate

Abstract

In order to protect structures along the offshore and off the coast, breakwaters are commonly applied to reduce the influence of waves. Flat plate breakwater is studied frequently due to its great performance near the water surface, however, traditional passive methods such as fixed and floating flat plate breakwaters usually fail to give full play of effective wave dissipation when encountering variable unknown incoming waves. Therefore, this paper develops an interdisciplinary model coupling computational fluid dynamics (CFD) and deep reinforcement learning (DRL) to study the wave dissipation of a submerged movable flat plate breakwater against regular waves. An in-house numerical wave tank (NWT) is built to simulate the fluid-structure interaction between the plate and regular waves. The fluid domain in NWT is regarded as environment while the flat plate breakwater is agent. In addition, the wave dissipation strategy is learned by the artificial neural network (ANN) through the continuous wave-plate interaction. It is excited to find that the coupling model is able to learn the control strategies automatically and exhibits good adaptability to the changes of environment. 13 14 INDEX TERMS Wave dissipation, deep reinforcement learning, flat plate breakwater, active controlling, CFD and DRL. culated, of which the results showed that a suitable geo-49 metrical porosity of the upper plate leads to a low level of 50 uplift wave forces on both plates. Reference [17] investi-51 gated the flow field passing over a submerged horizontal 52 flat plate by means of a free surface potential flow model, 53 a form discretized by the Boundary Element Method (BEM), 54 from which the wave dissipation mechanism of a plate-55 type breakwater and the influence of plate thickness, length 56 and submergence was concluded. Reference [18] presented 57 an integrated CFD+CSM approach to fully simulate the 58 hydroelastic interaction between nonlinear ocean waves and 59 a deformable SHPB device, making two major contributions: 60 (a) the research work demonstrated a valid computer-aided 61 approach that can perform hydroelastic offshore and coastal 62 designs; (b) the researching work demonstrated a hydroelastic 63 design methodology for breakwaters for the first time and 64 showed that the deformation of the structure has a significant 65 effect on the wave-damping performance. References [19] 66 and [20] conducted an experiment to research the wave dissi-67 pation performance of a twin-plate considering various wave 68 conditions. References [21] and [22] investigated the interac-69 tion between freak waves based on numerically investigating 70 the interaction characteristics of horizontal deck structures 71 and freak waves, which revealed the corresponding phenom-72 ena, wave loads, and structural response. Reference [23] 73 further studied the interaction between Peregrine breather-74 based freak waves and twin-plate breakwaters, including the 75 characteristics of interaction phenomena, transmitted wave 76 surface, wave loads, and st...