Author(s): Alejandro Jesus Cebada Relea; Mario Lopez Gallego; Ruben Claus Gomez; Fernando Soto Perez

Linked Author(s):

Keywords: Floating breakwaters; Marine structures; Numerical modelling; Ports

Abstract: In ports with mild wave conditions it is common to deploy floating modular breakwaters with lower costs and environmental impacts than solutions fixed to the seabed (McCartney, 1985). Nonetheless, these structures withstand high loads during extreme events that can break the connections between modules – the weakest element of these structures and the keystone of their design. On these grounds, an exhaustive analysis of the wave-structure interaction under site-specific wave conditions during the project phase and an appropriate maintenance once in operation are mandatory to prevent possible failures (Diamantoulaki and Angelides, 2013). An example of failed floating breakwater is the pontoon of the Port of Figueras (Asturias, Spain), which has reported several connection breaks in recent years. The wave loads on floating breakwaters and their joint interaction have been examined through physical modelling in previous works (e.g., Ferreras et al., 2014, Loukogeorgaki et al., 2017). Several numerical modelling approaches may also be used with this aim, such as: the potential flow theory (e.g., Koo, 2009), the hydroelasticity theory (e.g., Michailides and Angelides, 2012) or the Navier-Stokes equations (He et al., 2019).. Codes based on the boundary element method (BEM) have been commonly applied to model the response of different marine structures, including: platform-risers (Wang and Liu, 2018), Mid Water Arch structures (Hill et al., 2014) or wave energy converters (López et al., 2017). However, the application of BEM to simulate the response of floating breakwaters is rather limited in the literature (e.g., Samaei et al., 2016). In this work, the potential flow theory is used along with the BEM to investigate the pontoon of the Port of Figueras. First, the harmonic response of a pontoon unit is analysed in the frequency domain to estimate the hydrodynamic coefficients – namely: the added mass and the hydrodynamic damping – and the hydrostatic stiffness. Subsequently, the response of a complete structure is solved in the time domain by applying the convolution integral and including the bending stiffness of the connections, the mooring forces, and the nonlinear Froude-Krylov forces. In addition, the non-viscous damping forces are considered in the simulations, for which the corresponding parameters are calibrated with the experimental results obtained by Peña et al. (2011). Finally, the results of the simulations for different wave conditions are discussed and conclusions are drawn, which can help to improve the design of future floating breakwaters and the analysis of their interaction with local wave conditions.

DOI: https://doi.org/10.3850/IAHR-39WC252171192022379

Year: 2022