Calibrating hydrodynamic viscous damping in engineering models of floating wind platform utilising simplified CFD models

Accurately investigating hydrodynamics for floating wind platforms using potential theory poses challenges due to uncertainties in quadratic damping estimation, significantly influenced by drag coefficient selection. Costs associated with wave basin testing for calibration data have prompted a shift towards the use Computational Fluid Dynamics (CFD) to estimate appropriate drag coefficients to calibrate potential theory models. However, CFD simulation of six-degrees-of-freedom floating substructure, with addition of turbine loading across varying metocean conditions, demands substantial computational resources. This study evaluates whether simplified CFD models can fine-tune viscous terms in potential theory models or if a fully complex model is needed. Decay, steady current, and wave condition tests were conducted in the CFD model of a floating wind platform. Calculated drag coefficients from these CFD-based approaches varied by 15–85% of offshore standards. Coefficients obtained were used to calibrate potential theory models of the platform. Without viscous correction, the potential theory model overestimated response amplitude operator values at the platform's natural frequency for surge and pitch degrees of freedom by up to twofold. Applying viscous drag coefficients from CFD methods reduced these differences to within 10–20%. This research guides numerical modellers in choosing dynamic complexity levels and adjusting CFD simulation accuracy within computational resource limits.