A simplified model for ice forces in ship-ice collision
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Journal Title
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Insinööritieteiden korkeakoulu |
Master's thesis
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Authors
Date
2014-10-20
Department
Major/Subject
Marine Technology
Mcode
K3005
Degree programme
Konetekniikan koulutusohjelma
Language
en
Pages
68+17
Series
Abstract
The maritime transportation system in the Northern Baltic Sea (NBS) is complex and operates under varying environmental conditions. The most challenging conditions relate to the presence of ice-cover, which for the NBS i.e. Gulf of Finland or Bay of Bothnia, can remain up to several months. Therefore it is evident, that the number of accidents in these two areas is the highest during winter season which can involve accidents like groundings, collisions and damages due to the ice. This thesis seeks for a simplified method for evaluating the ice force for a case where ship collides with ice in transverse direction. The derived ice force formula is added to the time-domain collision simulation model for the evaluation of collision damage. Additionally, Minorsky’s classical collision model is developed further to consider the influence of ice in ship collision dynamics. The ice force calculation model was developed based on the knowledge of calculating ice force for wide sloping offshore structures and based on the model test results measured during SAFEWIN project. The model was validated on the basis of ice damage statistics report. The collision calculations in ice were done by time-domain model and compared to the developed simple model. As a result, the ice force formula showed satisfactory agreement compared to the SAFEWIN project model test results. Derived simplified collision calculation model revealed a good agreement with time-domain model. In comparison with open water results, the main change in collision in ice came from the added mass increase due to the ice. Therefore, deformation energy and penetration depth rose. In calculations, the increase in deformation energy, compared to the open water result was however not significant as the ice forces evaluated with the present model are small compared to other forces such as collision and inertia force.Description
Supervisor
Kujala, PenttiThesis advisor
Tabri, KristjanMontewka, Jakub
Keywords
ice force, ship collision, sideways movement