Two approaches are proposed to derive the fatigue life of a rigid wing sail. The first one is based only on the wind speed the wing encounters during its service life and the other makes use of a model built in the software SIMA to include the effect of the ship's motion.
The SIMA model represents a reference ship with one wing on its deck. The hydrodynamic description of the ship was done thanks to the ShipX Vessel Response (VERES) software. The wing was modeled as a beam, and the aerodynamic forces acting on it were considered using sets of two-dimensional airfoil coefficients, chord and wing span. The input wind was turbulent using a stochastic, full-field, turbulence simulator called TurbSim, developed by the US National Renewable Energy Laboratory (NREL). Routing tables from the software Adrena were analysed to describe the environment the ship and wing will experience.
From a load point of view, the stress values considered in both approaches were derived using a finite element model built with Abaqus. Bending moments are applied on the wing model and the stresses in the composite parts were read at the root of the wing on the pressure and suction sides. A transfer function from bending moments to stresses was built for the stresses in the longitudinal and transverse fibre directions, enabling converting the bending moment history into stress time series.The material properties considered were based on the SNL/MSU/DOE database. The damages were computed using Miner's rule and unidirectional fibreglass SN curves which were fitted to the test data. The materials are not specific to the wing and the carbon fibres material are not studied since their fatigue properties are better than fibreglass.
Additional analysis were carried out, such as evaluation of aerodynamic damping due to sudden stall, an estimation of the thrust force and a sensitivity study to measure the wing's response depending of the stiffness proportional damping applied.