An experimental study on the effect of speed on the ice resistance of a ship

• Main Author: Heinonen, Teemu
• Other Authors: Leiviskä, Topi, Insinööritieteiden korkeakoulu, School of Engineering, Sovelletun mekaniikan laitos, Kujala, Pentti, Aalto-yliopisto, Aalto University
• Format: Master Thesis
• Language: Finnish
• Published: 2010
• Subjects: ice resistance; breaking component; wave making; speed dependency; model tests; level ice; presawn ice; high speed; jäänmurto; tasainen jää; jäävastus; nopeus; murtokomponentti; nopeusriippuvuus; mallikoe; esisahattu jää; aallonmuodostus; Ice Sheet; Icebreaker
• Online Access: https://aaltodoc.aalto.fi/handle/123456789/98747

The previous studies on the ice resistance of a ship have focused on speeds below 10 knots oven though icebreakers often move with higher speeds when ice is thinner. The effect of speed on the ice resistance is poorly known. One of the main reasons for this is that the effect of ice sheet on open water resistance is not known. The ice resistance is often divided into different components, for example into breaking submersion- and speed components, The relative magnitudes and speed dependencies of the components are not agreed on literature, especially the speed dependency of the breaking component is unclear in literature. The purpose of this work was to experimentally study the speed dependency of the breaking component and the restraining effect of ice sheet on the wave making of the ship, and also gather information about the ice breaking process on high speeds for future research. Visual observations of the breaking process were done by filming the bow of icebreaker Kontio in full scale tests in March 2009. The speed dependency of the breaking component was studied by performing model tests in level and presawn ice. The effect of the ice sheet on the wave making was studied visually from model test videos. Tests were performed in the lee tank of the Ship Laboratory in November-December 2009 with the model of icebreaker Otso (sister ship of Kontio). Tests were performed in two ice thicknesses (30 cm and 50 cm in full scale) with four different speeds (2 kn, 6 kn, 12 kn and 16 kn in full scale) in order to get the effect of ice thickness and have a broad speed range. Open water tests and tests in ice-free channel were also performed. According to model tests, the total resistance increases linearly with speed. The breaking component also increases linearly with speed. The ice sheet restrains the wave making and the restraining effect increases with ice thickness. The ice sheet could increase the pressure against the hull which could increase the viscous resistance. The presence of ice sheet increased the ...