Boom Overtopping Assessment Based on a Coupled Hydrodynamic - CFD Analysis

Plastic pollution in the marine environment is an increasing problem with severe impacts on ecosystems and economies around the globe. The Ocean Cleanup (TOC) Foundation develops a floating barrier able to intercept, concentrate and extract plastic from the marine environment. TOC has conducted several experiments and numerical studies to determine the capture efficiency of its system. One of the phenomena leading to its decrease is wave overtopping or under-flowing when the system cannot properly follow the waves, this issue is amplified by the use of a stiffer barrier than the original deep-water moored concept. When such events occur, plastic debris won’t be captured by the system and will escape into the open ocean. Such an event will therefore be decreasing the capture efficiency. To model and quantify plastic loss due to wave overtopping and under-flowing, the ideal approach would be to use a nonlinear 3D CFD method including hydro-elasticity of the barrier structure. Given the size of the problem and the number of conditions that need to be simulated to characterize the design space of the system, the use of such a method is computationally very expensive and therefore unrealistic. Therefore, the objective of this work is to propose an alternative method. This paper presents a method of quantifying plastic loss by coupling a hydrodynamic solver to a 2D CFD solver. A hydrodynamic model is set up to predict the dynamics of the boom. A 2D CFD model with imposed motion is used to analyze the local effects of wave overtopping. From there, wave overtopping events along the barrier system are analyzed and quantified using the results found in the 2D CFD study.