A Physical and Computational Comparison of Floating Breakwater Design Efficiencies for Habitat Restoration in the Indian River Lagoon

Abstract

This study examines the design and implementation of floating breakwaters (FB) in the Indian River Lagoon (IRL) to support and protect living shoreline restoration projects from damaging wave climates. The design significant wave climate of the IRL in a 0.6 m water depth had an incident significant wave height of 0.20 m with a wave period of 1.6 s. Based on previous studies, it has been found that habitat restoration will be successful if the wave height is reduced from 0.20 m to 0.10 m with the use of a FB structure. FB structures attenuate wave energies and are transportable, allowing for removal once the living shoreline restoration is established. The transmission coefficient is physically tested in a wave channel and numerically simulated in OpenFOAM for a rectangular FB structure to determine the effects of the draft parameter (dr/d) and the breadth parameter (B/L). The dimension parameters were compared to the transmission coefficient, which is a nondimensional value traditionally used to compare the transmitted wave height to the incident wave height. Additionally, the FB motion response to wave interaction is simulated using a static structure and a dampened, dynamic structure. The physical testing was performed in the Florida Institute of Technology (FIT) wave channel at 1:1 scale using a rectangular, wooden FB structure. The OpenFOAM solver, olaFoam, developed in 2015 by Pablo Higuera for wave generation and absorption, was applied to a numerical replicate of the FB structure in the FIT wave channel for ease of comparison and validation. A wave-by-wave analysis was performed to determine the significant wave height, as well as a singular wave analysis that is comparable between each data set. In the numeric modeling, the static FB structures attenuated the wave energies more effectively than the dynamic structures due to the lack of motion response. The numerically modeled predicted a lower transmission coefficient than the physical testing, due to assumptions during the computation and a uniform dampening coefficient throughout the dynamic cases. The suggested FB structure dimensions for wave attenuation in the IRL during living shoreline restoration are a draft of 0.4 m and a breadth of 1-1.25 m in a 0.6 m water depth.