Limit loads of ice ridge formation around offshore wind farms

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master_Wan_Haokai_2025.pdf (9.74 MB)

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School of Engineering | Master's thesis
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2025-09-29

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Mcode

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Master's programme in Mechanical Engineering

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en

Pages

56

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Abstract

This study investigates ice ridge formation around offshore wind farms in the Northern Baltic Sea using the Helsinki Discrete Element Model (HiDEM). The simulations successfully capture the multi-stage ridge-building process and demonstrate a strong non-linear dependence of ridge-building line load on interaction width, aligning with the empirical trend prescribed by ISO 19906 for strong ice conditions. However, the ISO formulation may overestimate loads for the typically weaker first-year ice of the Baltic Sea, highlighting the need for region-specific calibration. Two distinct failure modes were identified: a \textit{limit stress} scenario where ice fails locally against individual turbines, and a \textit{limit force} scenario where the collective resistance of the turbine array triggers large-scale pressure ridging at the farm perimeter. The transition between these mechanisms depends on ice properties, environmental driving forces, and the number of turbines enveloped by the ice floe. Under limit force conditions, the total ice load on the wind farm increased by 27\% compared to limit stress scenarios, though this manifests as a sum of individual loads on structurally independent foundations rather than a single global force. The simulated ridge morphologies—including sail heights (2 m) and keel depths (7.5 m)—closely match field observations, validating the capability of HiDEM for engineering-scale ice load predictions.

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Supervisor

Polojärvi, Arttu

Thesis advisor

Prasanna, Malith

Keywords

ice mechanics, limit force scenario, pressure ridges, discrete element method, Helsinki discrete element modelling, offshore wind farm

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https://urn.fi/URN:NBN:fi:aalto-202510208305

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[dipl] Insinööritieteiden korkeakoulu / ENG