Date of Award

Fall 2020

Project Type

Thesis

Program or Major

Mechanical Engineering

Degree Name

Master of Science

First Advisor

Barbaros Celokkol

Second Advisor

Igor Tsukrov

Abstract

Aquaculture, the process of growing marine plants and animals in the ocean, has been rapidly expanding due to increased seafood consumption coupled with the steady decrease of wild fish stocks. Increasing environmental concerns due to near-shore farming practices have pressured farmers to expand into more energetic open ocean sites. Environmental loading in these off-shore sites can deform common non-rigid aquaculture fish cages, reducing the cage’s net chamber volume, which can severely impacting the health of the rearing fish.

Copper alloy nets have emerged as a possible alternative to traditional polymer (nylon) twine used in the net chamber of fish cages. Copper alloy nets have a natural resistance to marine growth and help prevent fish escapement from predators due to net damages. However, little is known of copper alloy’s effectiveness in net chamber volume reduction under waves and current. In this study, the volume deformation of a gravity type cage system employing copper alloy netting was analyzed. Numerical modeling tools were employed to predict the dynamic and structural behavior of fish cages outfitted with this type of netting. Copper alloy and nylon net chamber volume loss were predicted and compared. Experimental testing and theoretical predictions were performed to determine the needed structural characteristics of the copper alloy netting to properly simulate the dynamic behavior. Computational finite element software packages, MSC.Marc Mentat and AQUA-FE, were adopted as the primary tools to simulate and analyze the dynamic and structural behavior of the gravity fish cages in waves and current.

It was found that the implementation of the bending stiffness associated with copper netting yielded little discernible differences when compared to nylon netting. The primary factors found to influence the reduction of the copper alloy cage volume were the material mass and the drag coefficients, which resulted in a 70% improvement in volumetric stability.

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