A Study on Velocity Dependence of Breaking Component in Ice Resistance. Part 1 Experimental Evidence of Velocity Dependence of Breaking Component in I

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1 A Study on Velocity Dependence of Breaking Component in Ice Resistance. Part 1 Experimental Evidence of Velocity Dependence of Breaking Component in Ice Resistance. by Kato Kazuyuki, Member Adachi Meiya, Member Kishimoto Hiroharu Hayashiguchi Seiji Summary It is well recognized that the ice resistance in continuous breaking mode consists of several components. However, the quantitative recognition of those components in the ice resistance is poorly understood. To understand the ice resistance quantitatively, the dependency on such factors as a thickness of ice sheet, a bending strength of ice sheet, a velocity of ship and so on has to be clarified for each component. Among those components in the ice resistance, it is unanimously recognized that the breaking component is of primary importance. It has been considered by many investigators that the breaking component strongly relates to the moment capability of ice sheet, afe and does not depend on the ship velocity. However, the authors have had doubt on this recognition that the breaking component is independent of the velocity of ship. Such doubt comes partly from the experimental study by Kato et al. and partly from the theoretical study by Sorensen and Tawara & Horimizu. In order to clear this doubt, it is necessary to separate the breaking component from other components. For this purpose, a new component separation test-named the TBI test-was developed and employed to the 1/20 model test on medium size icebreaker. The TBI test can use an almost completely preserved broken ice field which has been made just before by the test of the same model in intact level ice. Thus the TBI test employs a realistic breaking patters of ice field. The model experiments were performed on three different velocities. Six or seven tests were conducted at each velocity under different combinations of ice thickness and bending strength to verify the prediction. It was found from experiments that a relationship between the breaking component and the moment capability of ice sheet is linear when the velocity is specified. It is in agreement with authors' prediction. A relationship between the submersion component and ice thickness is not strictly defined, but a linear relation is again tenable. Coefficients of both the relationship between the breaking component and the moment capability of ice sheet and the relationship between the submersion component and ice thickness were plotted with respect to velocity. It was found that both coefficients increase with velocities. This indicates that both the breaking component and the submersion component increase with velocities. It is concluded that the velocity dependence of the breaking component in ice resistance has been clearly evidenced. However, in order to understand the ice resistance more quantitatively, the authors should concern a study on the velocity dependency of the breaking component, which was not accomplished in the present study.

2 Fig. 1 Relationship between velocity and normalized ice force obtained from experiments on inclined pile structure

4 Table. 1 Principal particular of modeled ship

5 Fig. 2 Plots of Rb and 6fh2 for v=115 mm/s Fig. 5 Plots of R' and h for v=115 mm/s Fig. 3 Plots of Rb and (IA' for v=230 mm/s Fig. 6 Plots of R' and h for v=230 mm/s Fig. 4 Plots of Rb and cyfe for v =345 mm/s Fig. 7 Plots of R' and h for v = 345 mm/s

6 Fig. 8 Relationship between velocity and coefficient a in equation ( 8 ) indicating velocity dependence of breaking component Fig. 9 Relationship between velocity and coefficient 9' in equation (10) indicating velocity dependence of submersion component

7 Fig. 10 Comparision between experimental ice resistance and ice resistance calculated from empirical equation (equation (11) ) 1) Milano, V. R. (1973) : Ship Resistance to Continuous Motion in Ice, Transactions Society of Naval Architects and Marine Engineers, Vol. 81, (1973) pp ) Kotras, T. V., Baird, A. V. and Naege, J. N. : Predicting Ship Performance in Level Ice, Transactions Society of Naval Architects and Marine Engineers, Vol. 91, (1983) pp ) Carter, D. : Ship Resistance to Continuous Motion in Level Ice, Report prepared for The Transport Canada Research and Development Centre, (1982) 95 pp. 4) Lewis, J. W. and Edwards, Jr., R. Y. (1970) : Methods for Predicting Icebreaking and Ice Resistance Characteristics of Icebreakers. Transactions Society of Naval Architects and Marine Engineers, Vol. 78, 5) Tatinclaux, J.-C., Alexseyev, J., Enkvist, E., Kitagawa, H. Narita, S. Schwarz, J., Takekuma, K. and Williams, F. M. : Comparative Model

8 Tests in Ice of a Canadian Coast Guard R-Class Icebreaker, Transactions Society of Naval Architects and Marine Engineers, Vol. 97, (1989) pp ) Nevel, D. E. : The Narrow Free Infinite Wedge on an Elastic Foundation, US Army Cold Regions Research and Engineering Laboratory Research Report 79 (1961) 50pp. 10) Nevel, D. E. (1977) : Ice breaker simulation, US Army Cold Regions Research and Engineering Laboratory Report ) Sorensen, C. : Dynamic Response of a Semi- Infinite Plate Subjected to Steadily Increasing Boundary Force, ZAMM, Vol. 59, (1978) pp

Fig. 3 Coordinate system and notation Fig. 1 The hydrodynamic force and wave measured system Fig. 2 Apparatus of model testing

Fig. 3 Coordinate system and notation Fig. 1 The hydrodynamic force and wave measured system Fig. 2 Apparatus of model testing The Hydrodynamic Force Acting on the Ship in a Following Sea (1 St Report) Summary by Yutaka Terao, Member Broaching phenomena are most likely to occur in a following sea to relative small and fast craft