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This study investigates the performance of podded propulsors in various operating conditions: open water and different ice conditions. The model used in this study is an icebreaker driven by twin-podded propulsors. Preliminary results from ice tank tests are presented. These include steering moment generated by the propulsors, thrust and torque of the propellers and the forces exerted on the hull at the location of the connection of the propulsors for different levels of ice and pack ice conditions, as well as in open water. © 2011 National Research Council of Canada.

Two ice trials were performed with the Finnish ice-breaker Sampo in the Gulf of Bothnia in the winters of 1988 and 1989. This paper includes results from the resistance tests in level-ice and in a fairway channel, as well as from turning circle tests in level-ice. A series of ice model-tests was also performed for the same ship. The extrapolated model-test resistance estimations as well as results obtained with some resistance calculation methods are compared with the measured full scale values. The turning circle results are compared with results published for other ships.

Two ice trials were performed with the Finnish ice-breaker Sampo in the Gulf of Bothnia in the winters of 1988 and 1989. This paper includes results from the resistance tests in level-ice and in a fairway channel, as well as from turning circle tests in level-ice. A series of ice model-tests was also performed for the same ship. The extrapolated model-test resistance estimations as well as results obtained with some resistance calculation methods are compared with the measured full scale values. The turning circle results are compared with results published for other ships.

The report describes the second and final phase of a joint research project between Canada and Finland. The objective of the work was to experimentally investigate the mechanics of a ship ramming a massive ice floe. In the first phase, models of the vessel M.V. Arctic were tested and compared with full scale data. While the model/full scale agreement was encouraging, concern was raised about the influence of ship size, bow form, ice strength scaling and other parameters on the ramming forces and ship hull response. In the second phase, described herein, these questions were addressed by testing a model of a very large vessel (150 000 tonne) and a model of the M.V. Canmar Kigoriak (6 700 tonne). Both models consisted of multiple segments connected to a flexible backbone. Ramming forces and vessel dynamic response were measured. Altogether 107 tests were conducted with these models. The results of the tests are summarised in this report. The main result of the project is the understanding of the ramming process and the ways in which the ship and ice parameters influence the vessel response. The main engineering concern is the maximum bending moment that may occur in the hull girder. It is shown that two separate processes take place during ramming. These can be called initial impact phase and beaching phase. There are cases in which only quasi-static beaching is important, especially for a large ship striking a square ice edge. Dynamically amplified interaction forces of the initial impact phase in some cases may be nearly 50 % larger, and the resulting bending moments may be nearly 100 % larger than those of the quasi-static case. The main factors contributing to dynamics of interaction forces are vessel size, bow form, size of previous imprint and ice strength. Velocity linearly influences force and bending moment, but does not affect the degree of dynamic amplification. The results have implications to both design and operation of Arctic vessels.

The report describes the second and final phase of a joint research project between Canada and Finland. The objective of the work was to experimentally investigate the mechanics of a ship ramming a massive ice floe. In the first phase, models of the vessel M.V. Arctic were tested and compared with full scale data. While the model/full scale agreement was encouraging, concern was raised about the influence of ship size, bow form, ice strength scaling and other parameters on the ramming forces and ship hull response. In the second phase, described herein, these questions were addressed by testing a model of a very large vessel (150 000 tonne) and a model of the M.V. Canmar Kigoriak (6 700 tonne). Both models consisted of multiple segments connected to a flexible backbone. Ramming forces and vessel dynamic response were measured. Altogether 107 tests were conducted with these models. The results of the tests are summarised in this report. The main result of the project is the understanding of the ramming process and the ways in which the ship and ice parameters influence the vessel response. The main engineering concern is the maximum bending moment that may occur in the hull girder. It is shown that two separate processes take place during ramming. These can be called initial impact phase and beaching phase. There are cases in which only quasi-static beaching is important, especially for a large ship striking a square ice edge. Dynamically amplified interaction forces of the initial impact phase in some cases may be nearly 50 % larger, and the resulting bending moments may be nearly 100 % larger than those of the quasi-static case. The main factors contributing to dynamics of interaction forces are vessel size, bow form, size of previous imprint and ice strength. Velocity linearly influences force and bending moment, but does not affect the degree of dynamic amplification. The results have implications to both design and operation of Arctic vessels.

The ramming interaction between a ship and a multi-year ice floe is studied by model tests of the ice-breaking supply vessel Canmar Kigoriak. A flexible backbone model of Kigoriak is designed and constructed. The model backbone is instrumented with strain gauges to measure hull bending moments and shear forces in five sections. The model is calibrated both statically and dynamically. The ramming tests are performed into an ice block formed of model ice sheets in an ice model basin. The forces of the ice block during the rams are measured with six component balance. The results are presented in the form of signal time histories and plots of the extreme values of different quantities as a function of ship and ice parameters. The model test results are compared with the available data from the Canmar Kigoriak full scale trials.

The report presents the results of numerical studies of ice failure load caused by a ship bow penetrating into a large multi-year ice floe. Ice crushing and methods available for constitutive modelling of ice are discussed. The applicability of different material models in commercial FE-codes are studied. Different failure criteria are presented and fitted into a set of multi-year ice strength test results. An FE-model of the ice block including ship bow imprint is constructed. Both linear elastic and linear elastic-ideally plastic material models are applied to the ice block with several loading and boundary conditions. The linear elastic-ideally plastic model is calculated with von Mises failure criterion and the associated flow rule. The calculated results are compared with the existing data from fullscale ship ice trials. Also an attempt to apply strain softening in the nonlinear model is made in order to take into account the reduced load-carrying capacity of ice after the initial failure.

The mechanics of the interaction occurring when a ship rams a massive ice floe is analyzed.A calculation procedure to determine the ice load and the ensuing ship response is developed.The experimental values from full scale and model scale ramming trials are compared with the calculated values.The ice displacement occurring due to the ship bow penetrating into the ice floe is divided into two components.One component correspond to the crushing penetration into ice and the other is associated with the elastic deformation of ice.A formulation of these two components based on measurements and calculations is developed.The ship motions and ship hull vertical deformation are analyzed treating the ship hull as a Timoshenko beam.The water surrounding the ship hull is accounted for using the strip theory.In the calculation procedure the ship motions and ice displacement are combined by a kinematic condition.The procedure developed is applied to three ramming cases.The ramming of M.V.Arctic is studied both in model scale and full scale.The repeated ramming of Canmar Kigoriak on existing bow imprints is also studied. This study on the mechanics of ramming interaction does not include all aspects needed for ship design.The aim is to develop a model to determine ice load in ramming based on ice mechanics and ship particulars.

Time and distance constants of self-propulsion tests with the ship model in ice are analyzed, which are associated with the steady state of the running model. As the steady state seems not to be easily attainable with the free running model, an alternative method is recommended to get reliable data. An index is proposed to evaluate the reliability of the self-propulsion test and the associated resistance test.

The mechanics of the interaction occurring when a ship rams a massive ice floe is analyzed.A calculation procedure to determine the ice load and the ensuing ship response is developed.The experimental values from full scale and model scale ramming trials are compared with the calculated values.The ice displacement occurring due to the ship bow penetrating into the ice floe is divided into two components.One component correspond to the crushing penetration into ice and the other is associated with the elastic deformation of ice.A formulation of these two components based on measurements and calculations is developed.The ship motions and ship hull vertical deformation are analyzed treating the ship hull as a Timoshenko beam.The water surrounding the ship hull is accounted for using the strip theory.In the calculation procedure the ship motions and ice displacement are combined by a kinematic condition.The procedure developed is applied to three ramming cases.The ramming of M.V.Arctic is studied both in model scale and full scale.The repeated ramming of Canmar Kigoriak on existing bow imprints is also studied. This study on the mechanics of ramming interaction does not include all aspects needed for ship design.The aim is to develop a model to determine ice load in ramming based on ice mechanics and ship particulars.