Vortex shedding load on a full-scale wind turbine tower at transcritical Reynolds numbers

As the size of modern wind turbines increases, the phenomenon of vortex resonance, which occurs at lower critical speeds due to lower natural frequencies of larger turbines, becomes more significant. Vortex shedding in the wake of a slender structure is still not fully investigated, particularly with regard to the Reynolds number mismatch between small-scale models and the full-scale structure. The vortex shedding load with Re=4−10∙106 is addressed in this paper by investigating a full-scale measurement on a large wind turbine tower. The aerodynamic coefficients and vortex shedding load parameters are studied based on the measurement of wind pressure around the circumference of the tower. The results are compared to previous studies and values suggested in related standards. A detailed methodology for data evaluation is presented. As local parameters have been measured, the work marks the distinction between local and global parameters, in particular for the Strouhal number. Although this paper focuses on the tower-only configuration (without nacelle), the measurements are also carried out for a turbine including rotor-nacelle assembly (RNA), which allows the effect of blade position and rotation of the parked wind turbine on the lift coefficient of the tower to be studied.