Author(s): R. U. F. Von Bock Und Polach
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Keywords: No Keywords
Abstract: The impact of heave and pitch motions on the overall performance of ships is ice is not investigated much. The model test results presented in this paper are dedicated to explore the differences in resistance caused by vertical motions. In order to assess the impact of the heave and pitch motions on the resistance, towed resistance model tests have been carried out in two different modes. In the first mode the vertical motions of the model were constrained and in the second mode the model was allowed to heave and pitch freely. The tests were carried out with a model of the ice going tanker Uikku in the ice tank of the Marine Technology Group of the Aalto University, School of Science and Technology. The model tests have been carried out in an ice thickness of 20mm which is equivalent 60cm full scale thickness at low speeds with Froude-numbers between 0.04 and 0.08. The tested conditions have been level ice, pre-sawn ice and open water. The information gained from the tests are that the heave and pitch motions are affecting the average resistance and the resistance peak values. The average resistance in the free mode was around 20% higher than in the constrained mode for lower speeds, which indicates a significant loss of energy, but with increasing speed the difference between the two modes becomes smaller. The quantification of the peak values has been done with two new approaches which both show that peak values in the free mode are almost 100% higher than in the constrained mode. The vertical motions are thus considered being too significant to be neglected.
Year: 2010