Toward the development of an effective upward-acting icebreaking bow: the preliminary design and testing of the S-Bow

Paterson, Robert Bruce (1989) Toward the development of an effective upward-acting icebreaking bow: the preliminary design and testing of the S-Bow. Masters thesis, Memorial University of Newfoundland.

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Abstract

An upward-acting icebreaking bow offers certain features, referred to as operational advantages, that may improve the utility, reliability, or some aspect of the performance of ice-transitting shipping. Since the cessation of testing of icebreaking plow designs in the mid-1970's, there have been important developments in icebreaking technology that may make an upward-acting icebreaking bow feasible. -- A new concept for an upward-acting icebreaking bow, designated the S-Bow, incorporates a shearing fracture action as a method of reducing ice resistance. This study was directed toward generating a bow form to demonstrate the concept. An experimental program was conducted in level uniform ice, but the range of conditions that an icebreaking vessel would encounter was considered in the development of the bow form. -- Alternative bow configurations were tested in a small-scale experimental program. The S-Bow form selected for 1:30 scale resistance tests resulted from this design program. The resistance trials were conducted in the ice tank of the NRCC Institute for Marine Dynamics using the M. V. "ARCTIC" as a test case. -- The trials were evaluated from videotaped observations, resistance measurements, and a numerical analysis of the breaking mechanisms. A clearly defined fracture sequence and an adequate flow of broken ice could be observed, but the measured average resistance levels ranged from 2.0 to 5.0 times the ice resistance of the "ARCTIC" with its present bow form. The analyses indicated a large component of the recorded resistance could be attributed to design problems but it was also established that a significant inherent resistance resulted from the lifting and movement of broken ice. -- A set of revisions are proposed to rectify the design problems. The indicated performance envelope was assessed against the potential influence of the operational advantages of an upward-acting bow. The development of the open water capability of the S-Bow and reduction of the magnitudes of ice resistance are required to demonstrate its feasibility.

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