Design considerations for a continuous mussel farm in New England Offshore waters. Part II: Using validated numerical models to estimate the probability of failure Aquacultural Engineering

In response to stakeholder conflicts, coastal pollution, and spatial constraints limiting sustainable nearshore aquaculture, offshore farms have emerged as a potential solution. However, offshore farms are exposed to energetic wave–current conditions and require a rigorous engineering approach to reduce failure risk. This paper presents a methodology to evaluate the risk of structural failure of offshore mussel farms in response to extreme wave and current conditions using a representative mussel farm design in New England offshore waters. This includes a three-step methodology: (1) Computational fluid dynamics-derived drag coefficients: 2D OpenFOAM simulations determine normal and tangential drag coefficients for mussel droppers; (2) Hydro-elastic finite-element modeling: a time-domain finite-element model driven by Airy-wave kinematics and Morison loads to predict mooring, mainline, strap, and dropper responses under 10-, 25-, and 50-year return-period wave and current scenarios; and (3) Statistical risk assessment: simulation outputs are interpolated to create a continuous response field across the full range of wave heights and current speeds, which is then integrated with a joint probability density function of significant wave height and current speed – alongside component ultimate and residual strength at three growth phases – to estimate failure probabilities over specified design lives and recommend optimized safety factors. Results indicate that combining accurate drag coefficients with a continuous response surface and joint-PDF risk analysis enables systematic estimation of component failure probabilities and informs appropriate safety-factor selection. Thus, the proposed integrated methodology can be used to quantify structural failure risk and support informed design decisions for reliable offshore aquaculture structures.