Date of Award

5-2023

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Ocean Engineering and Marine Sciences

First Advisor

Robert J. Weaver

Second Advisor

Deniz Velioglu Sogut

Third Advisor

Robert van Woesik

Fourth Advisor

Richard B. Aronson

Abstract

Coral reef populations have rapidly been declining in coastal waters worldwide. Losing these ecosystems results not only in a loss of habitat and biodiversity, but also a loss of wave attenuation and subsequent coastal protection. Ongoing projects seek to rehabilitate and/or replace destroyed reefs with artificial structures like reef balls and rip-rap, but none perform as well as a healthy, natural reef. This project created scale modules mimicking the reef-crest and spur-and-groove (SAG) zones commonly found in natural reefs and used these models to support new efforts in artificial reef design. The modular structure consists of three different components including: berms in the groove area that encourage wave-shoaling and mitigate scouring, spurs that initiate wave breaking and circulation, and crests that will be behind the spurs to dissipate any remaining wave energy. 3D renderings of the reef modules were created and imported into the CFD software package FLOW-3D® HYDRO, which was used to calculate information on the fluid-structure interaction. Change in wave height was the main indicator of energy dissipation from the structure, but turbulence within the grooves as well as beyond the structure were analyzed to further understand the interaction. Based on model simulation results, the morphology of the structures was adjusted to optimize the design in terms of wave height reduction and use of materials to lower costs. Wave height, wave period, spur length, crest length, groove width, and depth during different tidal conditions were all individually varied from a base case scenario to test the sensitivity of the flow to the changes. These tests further informed a second set of testing with optimized spur and crest design, which consisted of a 1:1 slope at the front of the spur, uniform submergence across the top of the spur module, and a sloping back crest. Results showed that the model was sensitive to wave height, wave period, spur length, groove width, and depth during different tidal conditions, and the reef was most effective when it initiated wave breaking in waves that were not depth limited otherwise. With the optimized design the structure has the ability to achieve a 57% wave height reduction. This research acts as a steppingstone in the design aspect of the larger scale project of designing, manufacturing, and installing artificial coral reef mimics in coastal waters.

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