Balancing Fidelity and Computational Efficiency in Mooring System Simulations for Floating Offshore Wind Turbines

Abstract

Floating Offshore Wind Turbines (FOWTs) are nearing commercial deployment, expanding offshore wind development opportunities to deeper waters beyond the reach of bottom-fixed turbines. Reducing the capital and operational costs of FOWTs is essential, with mooring systems identified as a key area for cost savings. High-fidelity, coupled, time-domain simulations ensure a mooring design’s suitability for a particular site, considering the full range of environmental conditions, but this process can be computationally demanding. During early design and optimization, lower-fidelity simulations enable exploration of a wider envelope of configurations at the cost of reduced model accuracy. This paper quantifies the trade-off between computational efficiency and model-to-model accuracy when reducing simulation fidelity. Using the IEC 15 MW turbine atop the UMaine VolturnUS-S platform with semi-taut and catenary mooring configurations, the study examines methods of reducing model fidelity with time and frequency domain approaches. Findings show strategic fidelity reduction, such as replacing the turbine with a lumped mass and applying a constant force, reduces computation by up to 96 %, while maintaining errors within 10 % for key performance parameters and enabling relative fatigue assessment. However, omitting critical elements like the control system may increase error without saving computational time. This work informs efficient mooring optimization strategies for FOWTs.