Ice-induced vibrations of offshore wind turbines

Abstract

Offshore wind turbines, given their structural properties, are expected to experience severe ice-induced vibrations. However, full-scale events neither have been observed nor published yet and thus predictions of existing numerical models could not yet been validated. Model-scale experiments, aiming to investigate ice-induced vibrations of offshore wind turbines, have been inconclusive as structures with low natural frequencies would exceed the capacity of test facilities (i.e., size and weight limits), while geometrical scaling introduced scaling effects (e.g., buckling) compromising the validity of conducted experiments.

In the absence of full-scale testing capabilities, the main goal of this work was thus to demonstrate how offshore wind turbines behave under dynamic ice loads in smallscale experiments. In total four research questions (RQ) have been formulated and are addressed in this thesis, collectively serving to achieve the primary objective of this thesis.

RQ1: How can ice-induced vibrations of vertically sided offshore structures be scaled?

RQ2: How can offshore structures with low and multiple eigenfrequencies be tested in
ice tank experiments?

RQ3: What types of ice-induced vibrations can an offshore wind turbine experience?

RQ4: What is the effect of wind-ice misalignment on the development of ice-induced
vibrations of offshore wind turbines?