Abstract
This paper analyses in-service measurements acquired onboard a 155 m long Ro-Ro cargo ship equipped with Flettner rotors, over a period of about 6 months. Simple CFD-based lift and drag coefficients are combined with wind speed estimates to predict the forces on the rotors, which are compared to in-service force measurements. The onboard recorded wind speed was scaled to rectify the large deviation from the hindcast, which can be due to several factors. The agreement between measured and estimated forces is generally good, with some minor deviations, which can be attributed to uncertainty due to various factors, briefly discussed here.