Suppression of array resonance by biofouling-induced dissipation in wave interaction with concentric monopile-cage structures

The structural integration of aquaculture facilities within offshore wind farms introduces a critical risk of collective hydrodynamic resonance, a phenomenon capable of causing catastrophic load amplifications in multi-body arrays. To address these, the present study develops a semi-analytical model, leveraging the eigenfunction expansion method and Graf's addition theorem, to analyze the wave-induced response of an Array of Concentric Monopile-Cage Integrated Structures (ACMCIS). A comprehensive parametric study uncovers a fundamental competition between wave energy amplification through collective resonance and its suppression via porosity-induced dissipation. The results demonstrate that specific array spacings can trigger powerful collective resonances, leading to hydrodynamic loads that dramatically exceed the single-body baseline. Counter-intuitively, a paradoxical dual role of biofouling is revealed: while fouling increases the direct wave load on the cages, it simultaneously acts as a powerful system-wide damper, effectively mitigating these severe resonant amplifications. Furthermore, the annular gap within each unit is identified as a critical “tuning knob” that modulates this resonant behavior. The developed model and the physical insights obtained offer a theoretical foundation essential for the safe and resilient design of these emerging multi-use platforms.