Numerical Simulation of Offshore Wind Turbine Dynamics in Drifting Level Ice

Jang, H. K. (Texas A&M University) | Kim, M. H. (Texas A&M University)

OnePetro 

ABSTRACT

According to the previous researchers, the bottom mounted offshore structure experienced ice-induced vibrations by the drifting level ice. In this study, a new ice breaking model based on the Matlock-method is proposed to explain the documented characteristics of ice-induced vibrations in many studies. A numerical simulation is performed by coupling the ice model with aero-hydro-servo-elastic numerical simulator, FAST. With this developed program, the monopile type wind turbine was examined in parked and operating conditions. The present results show that this model is capable of describing the three distinct ice crushing modes (intermittent ice crushing, frequency lock-in, and continuous brittle crushing), which are reported in both experimental tests and field data. In addition, it was found that the dynamics of tower and blades in two different conditions were dependent on the ice velocity.

INTRODUCTION

As the arctic offshore wind turbine has become a promising renewable energy system, several studies about the interaction of the wind turbines with ice have been carried out numerically and experimentally. Barker et al.(2005) conducted ice model tests with cones and vertical cylinder types of tower configurations in mean sea level. With this test results, Gravesen et al.(2005) analyzed the four distinguished ice failure modes and developed the design procedures to estimate extreme and combined ice loads. Some researchers (Heinonen et al.(2011); Hetmanczyk et al.(2011); Jussila et al.(2013)) investigated the wind turbine dynamics with ice numerically. They have integrated the ice load calculation models in the wind turbine simulation tool, OneWind. Yu et al.(2014, 2016) developed and added the ice loading module into FAST to consider the interaction between level ice and monopile-type offshore wind turbines. The model was based on the Matlock method with and without zonal concept. The numerical study of the monopile wind turbines in level ice(Shi et al.(2016)) was performed in parked and operating conditions. The pile with a conical waterline shape was modeled for level ice to fail in bending. They reported the ice-induced resonances at tower natural periods.