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

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.