Experimental Study on Nonlinear Motion Characteristics of Clean and Biofouling Aquaculture Cage Array in Waves

This paper aimed to understand the nonlinear dynamic responses that arise from the interaction between waves and a biofouling aquaculture cage array. To that end, physical model tests of a biofouling aquaculture cage array in a 1 × 3 configuration in regular waves were conducted. Wave steepness values of 1/60, 1/30, and 1/15 were considered within the frequencies spanning from low- to high-frequency bands. Then, the nonlinear dynamic responses of the system were systematically decomposed into four successive orders of components. This approach allowed for a thorough assessment of the inherent nonlinearity within the biofouling system by analyzing each individual order. The results highlight that the first-order harmonic component was the predominant contributor influencing the nonlinear dynamic response, while the higher-order harmonic components remained crucial in their contribution to the overall nonlinear dynamic response of the system. In particular, the harmonics within the low-frequency regime exhibited significantly greater nonlinearity compared with those in the high-frequency regime. A notable decrease in the amplitude of the harmonic component could be identified in the low-frequency regime due to the damping from the biofouling. The comprehensive analysis of the nonlinear dynamics within the biofouling system provides insights into optimizing the performance of aquaculture systems.