Podded propeller wash effect on level ice clearance

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master_Taimuri_Ghalib_2018.pdf (118.29 MB)

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Insinööritieteiden korkeakoulu | Master's thesis
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Date

2018-08-20

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Major/Subject

Marine Technology

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Degree programme

Master’s Programme in Mechanical Engineering

Language

en

Pages

7+100

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Abstract

Marine vessels and offshore structures functioning in Earth's frigid zones requires ice management to continue their routine operations. Icebreakers are the most influential vessel in assisting marine operations. The present study is set to analyze the clearance area of Level-ice using Azimuthing propeller jet in bollard pull condition. Advantages of the current investigation is that propeller jet effect in clearing level ice can be incorporated in designing new icebreaker and to maintain desired channel width. Propeller jets can be used to break level ice, when the ship is stationary or moving, where the amount and capacity of breaking or clearing the ice are based on the thrust of the propeller, angle between the propeller jet axis and free surface, and thickness of the ice as well as propeller running time. This thesis presents a comparison between full-scale experiments data (carry out in Gulf of Bothnia, March 2017) and model scale trials performed in Aker Arctic testing facility on the level ice sheet. These experiments were based on image data from external camera and propeller flow parameters, where the area, as well as coordinate calculation, were within 3% accuracy from the acquired images. Full-scale ice thickness utilized in the experiments were selected and confirmed from surveillance videos. Model-scale images were corrected using Hugin software while ImageJ was used to calculate ice clearance parameters. Propeller thrust and area analysis show 10-22 % of the variation in results of the model and full-scale experiments for 16 mm thick model ice. 16 mm thick model ice results are much closer to full-scale trials than 25 mm thick model ice. Analysis of transversal expansion of open water distance shows random outcomes. Furthermore, time scaling of the propeller operation is not feasible as it does not provide convenient results. Test results at 30-degree and 90-degree pod angles could be extrapolated to design a prototype vessel.

Description

Supervisor

Kujala, Pentti

Thesis advisor

Kujala, Pentti

Keywords

propeller jets, ice clearance, image analysis, Azipods, model scale, full scale

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https://urn.fi/URN:NBN:fi:aalto-201809034880

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