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dc.contributor.advisorEhlers, Sören
dc.contributor.advisorSteen, Sverre
dc.contributor.authorMyland, Daniela
dc.date.accessioned2019-08-20T11:16:40Z
dc.date.available2019-08-20T11:16:40Z
dc.date.issued2019
dc.identifier.isbn978-82-326-3993-9
dc.identifier.issn1503-8181
dc.identifier.urihttp://hdl.handle.net/11250/2609299
dc.description.abstractThe growing interest in Arctic transportation and field logistics leads to an increasing demand for ships with good ice breaking performance. The ice breaking performance of ships is usually defined by their ability to proceed in uniform level ice, where good performance means low ice resistance, high propulsion efficiency and continuous ice breaking. In order to assess the ice breaking performance in an early design stage, several theoretical methods may be applied to predict the ice resistance. However, every theoretical method necessarily makes use of simplifications and assumptions what in turn affects its precision and its reliability. Due to the physical nature of model tests, all processes, and thus, all forces contributing to the ice resistance are considered. As a result, model tests are still the most reliable method to predict the total resistance in ice. But with regard to the high costs of model tests there is a continued demand to gain knowledge on the reliability of theoretical prediction methods and to improve their accuracy. In the course of this thesis a systematic comparison of existing ice resistance prediction methods is carried out which represent the current state of the art. On this basis an assessment of the assumptions and simplifications of these different methods is outlined and the semi-empirical method of Lindqvist is found to be the most suitable method for further improvement. In order to achieve a valuable improvement, model test results are used to update the empirical basis of the prediction method with respect to an ice breaking ship type, i.e. ice breaking offshore supply vessels, anchor handling tugs and rescue and salvage vessels. Furthermore, ice model tests are conducted with newly developed testing equipment and techniques as well as a newly developed post-processing procedure to gain new insight on the ice breaking process. Thus, assumptions made by Lindqvist can be verified or corrected with regard to the investigated ship type. In particular, the creation of ice floes in the bow area of the ship and the resulting bottom ice coverage is evaluated by application of an underwater image analysis methodology. Furthermore, the ice floe characteristics are correlated to hull shape parameters, ice properties and finally the ice resistance. A refined version of Lindqvist’s method is then subjected to a numerical optimization algorithm. Thereby, the newly gained insights and a current empirical data set comprising the investigated ship type of ice breaking offshore supply vessels, anchor handling tugs and rescue and salvage vessels are used. During the optimization process, four variables are applied to the refined version of the semi-empirical prediction method of Lindqvist. By means of a computer algorithm these variables are optimized within specific boundary limits with regard to a minimization of the deviation to the total resistance in ice determined by model tests. Eventually, this process provides an optimized prediction method, with which the total resistance in ice can be predicted with a higher accuracy and reliability for the aforementioned ice breaking ship type.nb_NO
dc.language.isoengnb_NO
dc.publisherNTNUnb_NO
dc.relation.ispartofseriesDoctoral theses at NTNU;2019:198
dc.relation.haspartPaper 1: Myland, D., Ehlers, S. (2014). Theoretical Investigation on Ice Resistance Prediction Methods for Ships in Level Ice. Proceedings of the 33rd International Conference on Ocean, Offshore and Arctic Engineering, OMAE 2014 - Is not included due to copyright available at https://doi.org/10.1115/OMAE2014-23304nb_NO
dc.relation.haspartPaper 2: Myland, Daniela; Ehlers, Sören. Influence of bow design on ice breaking resistance. Ocean Engineering 2016 ;Volum 119. s. 217-232 https://doi.org/10.1016/j.oceaneng.2016.02.021nb_NO
dc.relation.haspartPaper 3: Myland, Daniela; Ehlers, Sören. Methodology to assess the floe size and distribution along a ship hull during model scale ice tests for self-propelled ships sailing ahead in level ice. Ships and Offshore Structures 2017 ;Volum 12. s. S100-S108 - Is not included due to copyright available at https://doi.org/10.1080/17445302.2016.1266591nb_NO
dc.relation.haspartPaper 4: Myland, Daniela; Ehlers, Sören. Model scale investigation of aspects influencing the ice resistance of ships sailing ahead in level ice. Ship Technology Research 2019 - Is not included due to copyright available at https://doi.org/10.1080/09377255.2019.1576390nb_NO
dc.relation.haspartPaper 5: Myland, Daniela; Ehlers, Sören. Investigation on semi-empirical coefficients and exponents of a resistance prediction method for ships sailing ahead in level ice. Ships and Offshore Structures 2019 - Is not included due to copyright available at https://doi.org/10.1080/17445302.2018.1564535nb_NO
dc.relation.haspartPaper 6: Myland D. (2019). Experimental and Theoretical Investigations on the Characteristics of Ice Floes Broken by Ships Sailing Ahead in Level Ice. 38th International Conference on Ocean, Offshore and Arctic Engineering, OMAE 2019 - Is not included due to copyrightnb_NO
dc.titleExperimental and Theoretical Investigations on the Ship Resistance in Level Icenb_NO
dc.typeDoctoral thesisnb_NO
dc.subject.nsiVDP::Technology: 500::Marine technology: 580nb_NO


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