Hydrodynamic Friction of Rotating Cylinders With Eccentricity Using Numerical Simulation

Abstract The Floating Axis Wind Turbine (FAWT) is a vertical axis design used to generate power from offshore winds. It features a rigidly coupled spar-type floating platform and a wind turbine for rotational motion. The FAWT’s spar floater can be simplified as a rotating cylinder in a uniform flow, similar to offshore drilling structures. Theodorsen’s empirical formula, commonly used to predict fluid friction experienced by rotating cylinders, tends to underestimate friction compared to two-dimensional computational fluid dynamics (CFD) analyses. This is due to the limited ability of simulations to replicate real-world phenomena accurately. This study used three-dimensional CFD to investigate the effects of eccentric fluid friction on a rotating cylinder. The sliding-mesh method was validated as a means of representing the eccentricity effectively. The analysis of the flow field revealed the influence of eccentricity and Reynolds number, and the friction coefficient was calculated. The results show that the friction coefficient increases with higher eccentricity, and agrees with the empirical formula at approximately 4% eccentricity. The impact of eccentricity on the friction coefficient is primarily governed by drag forces during the cylinder’s translational motion.