Aerodynamic loads on wind turbine towers arranged in groups with and without helical strakes

This work investigates the aerodynamic behavior of wind turbine towers when they are temporary placed in groups at small distance at the quayside of harbors. In this phase, many different arrangement geometries are possible, thus making wind tunnel tests a precious tool to pursue the economic design of the tower supporting structures. The effects of helical strakes, often employed to mitigate vortex-induced vibrations, is assessed through models at two different scales. The wind tunnel test results revealed complicated features of the problem and stressed the importance of the correct simulation in the experiments of the high Reynolds number regime. In particular, the strakes were found to reduce the mean base moment in the subcritical regime but to increase it in the developed supercritical regime.