Effects of Wind-Wave Misalignment on a Wind Turbine Blade Mating Process: Impact Velocities, Blade Root Damages and Structural SafetyAssessment

Abstract

Most wind turbine blades are assembled piece-by-piece onto the hub of a monopile-type offshore wind turbine using jack-up crane vessels. Despite the stable foundation of the lifting cranes, the mating process exhibits substantial relative responses amidst blade root and hub. These relative motions are combined effects of wave-induced monopile motions and wind-induced blade root motions, which can cause impact loads at the blade root’s guide pin in the course of alignment procedure. Environmental parameters including the wind-wave misalignments play an important role for the safety of the installation tasks and govern the impact scenarios. The present study investigates the effects of wind-wave misalignments on the blade root mating process on a monopile-type offshore wind turbine. The dynamic responses including the impact velocities between root and hub in selected wind-wave misalignment conditions are investigated using multibody simulations. Furthermore, based on a finite element study, different impact-induced failure modes at the blade root for sideways and head-on impact scenarios, developed due to wind-wave misalignment conditions, are investigated. Finally, based on extreme value analyses of critical responses, safe domain for the mating task under different wind-wave misalignments is compared. The results show that although misaligned wind-wave conditions develop substantial relative motions between root and hub, aligned wind-wave conditions induce largest impact velocities and develop critical failure modes at a relatively low threshold velocity of impact.

Joint Offshore Wind and Wave Energy Resources in the Caribbean Sea

“…As swell is relatively insensitive to wind speed, it is also often misaligned with wind direction. Crucially, offshore platforms and wind turbines installed in seas where there is misalignment between winds and waves cause increases in fatigue damage, construction time, and costs (Hildebrandt and Cossu 2018 ; Hildebrandt et al 2019 ; Kang and Yang 2019 ; Porchetta et al 2019 ; Sørum et al 2019 ; Verma et al 2020 ; Wei et al 2021 ). In Figure 6 , the difference between wave and wind directions ( ) was calculated for NDBC buoys 42058 and 41043 for the year 2019.…”

A review of impact loads on composite wind turbine blades: Impact threats and classification

“…3) [17,22]. For example, bird and atmospheric particles collision strikes (e.g., hailstone and rain droplet impacts) during operation as well as impact with surrounding structures during transportation and installation [23,24]. Wind turbine blades are made of composite materials as well as sandwich sections (Fig.…”

Simulation of Offshore Wind Turbine Blade Docking Based on the Stewart Platform

“…A numerical study [10] showed that the hub motion caused by wind and waves seriously affects the safety of blade docking. Verma et al [11][12][13] analyzed the blade root damage caused by hub motion. At the same time, Verma et al [14] and Jiang [15] adopted passively tuned mass dampers to reduce hub oscillation and hub impact on the blade to improve docking safety.…”