CONTRIBUTION OF TOWER WIND FORCES TO THE BASE MOMENT OF ONSHORE WIND TURBINES

Resumo

Wind turbines are analyzed and designed according to specific standards such as IEC
61400-1 which provides design requirements for all subsystems. Internal forces in the structural
elements are obtained through dynamic analyses of the rotor-tower-foundation coupled system under
the action of turbulent wind. This work presents and discusses dynamic analyses of a horizontal axis
onshore wind turbine model, representative of large wind turbines: the 5MW NREL Base Wind
Turbine, designed by the National Renewable Energy Laboratory (NREL). The simulations are
performed using the FAST and TurbSim computational tools, developed and made available by
NREL. The design situations cover normal operating and stationary rotor conditions, with wind
velocity fields given by the normal turbulence profile, extreme turbulence model and extreme wind
velocity model. The results are discussed in terms of the contributions to the base internal forces of the
wind forces applied to the tower, showing that these are predominant in analyses with extreme wind
speed.