Mikko Suominen

Full-Scale Measurements on a Polar Supply and Research Vessel During Maneouver Tests in an Ice Field in the Baltic Sea

Full-scale measurements were performed on the Polar Supply and Research Vessel, the S.A. Agulhas II during ice-trials in the Baltic Sea. Ice loads on the ship hull and propulsion system were measured concurrently with ice-thickness and whole-body vibration comfort for controlled maneuvers in a level ice field. These measurements were aimed at establishing the links between ice-properties, hull- and shaft loads and the vibration feedback received by the operator of the vessel. Results indicate that maneuvers significantly increase the frequency and magnitude of ice loads at the stern shoulder area as well as the ice impacts on the propellers. The number of ice impacts on the instrumented port side shaft line increased for turning maneuvers in a starboard direction. Occupants on the Bridge did not receive feedback through vibration transmission from ice impacts on the hull as a time-history of discrete events. Instead, ice passage excites the global bending modes of the vessel. Blade impacts between ice debris and the propellers are however perceivably transmitted to vessel operators. Although vibration exposure on the bridge is increased by operations in ice subjective experiences of vibration did not reach levels that caused discomfort.Copyright

THE ENCOUNTERED EXTREME EVENTS AND PREDICTED MAXIMUM ICE-INDUCED LOADS ON THE SHIP HULL IN THE SOUTHERN OCEAN

This paper studies the causes (ship operations and ice conditions) for the maximum ice-induced loads on the ship hull. Furthermore, the extreme loads are predicted with the Gumbel I asymptotic distribution. The study utilizes the full-scale measurement data collected in the Antarctic waters onboard S.A. Agulhas II between Dec 2013 and Feb 2014. The iceinduced loads were measured at the bow, bow shoulder and stern shoulder. The ice conditions were observed visually and the machinery control and navigational data were recorded continuously.The study showed that the turning of the ship has a major effect on the loading at the stern shoulder. The maximum loads also showed an increasing trend as a function of the observed ice concentration and maximum ice thickness in all three areas of the hull. In addition, the maximum loads at the bow showed a decreasing trend as a function of an increasing ice floe diameter. Furthermore, the study with the return period of the ice-induced loads showed that the return period of the loads was at the same level at the bow and stern shoulder. However, the extreme values exceeded with a probability of 1 % or 0.1 % are clearly higher for the bow.Copyright

From data to insight for a polar supply and research vessel

ABSTRACT Full-scale measurements on polar research vessels present an opportunity to advance the state-of-the-art in ship design through high-quality long-term measurements of environmental conditions and ship responses. The approaches, data analytics and synoptic results are presented for a comprehensive measurement campaign on a modern polar supply and research vessel, the SA Agulhas II. It is recognised that the real-time analysis and utilisation of such measurements could benefit the insightful operation and management of this vessel. To this end, the conceptual design of a monitoring and decision-aiding system is presented. Results indicate that significant potential beckons in the integrated acquisition, analysis and utilisation of full-scale ship-board measurements provided that this diverse data can be aggregated, analysed, visualised and interpreted in real time.

Purity and mechanical strength of naturally frozen ice in wastewater basins

A fairly clean ice cover can form over a contaminated water pond when the air-cooled surface of water freezes and impurities are efficiently expelled to the remaining water underneath. Natural freeze crystallization has recently been studied as a potential wastewater purification method with aqueous solutions on a laboratory scale. The effect of impurity inclusions on ice strength has been researched in model ice basins over the past few decades. It is of interest to discover how efficiently natural freeze separation works under real weather conditions before freezing can be utilized for wastewater treatment application. Herein, understanding the mechanical strength properties of naturally frozen wastewater (ice) is important when planning ice breaking and harvesting devices. This research implemented in-situ measurements of the flexural and compressive strength of ice in natural ice-covered environments of a freshwater lake, two peatlands and three mining site basins, and compares the determined strength with analyzed impurities of the ice. The results showed that despite varying ice growth conditions and initial water constituents, it was possible to deduce an evident yet simple relationship between mean ice strength and ice impurities: the more impure the ice is, the lower the value of strength is Based on this exploration, it was concluded that separation efficiencies, i.e. the impurity removal ratio between basin water and ice, from 65% up to 90% can be achieved by natural freezing.

Predicting local ice loads on ship bow as a function of ice and operational conditions in the Southern Sea

ABSTRACT Transportation in ice-prone waters is a timely topic because of the pursuit of natural resources and sea routes. S.A. Agulhas II voyaged in Antarctic waters during the austral summer of 2013–14. This paper studies how the local ice-induced loads on the ship bow are affected by different ice and operational conditions. A hierarchical Gaussian process model was used to study how the load distribution parameters change in different conditions. The operational conditions are described by ship speed, whereas the ice conditions varied from thin, first-year ice, to thick, multiyear ice. Because of this variation, the ice conditions are not represented by ice thickness alone but also by latitude, temperature and voyage time which represent the unmeasured ice strength. The predicted loads from the model match well with the measured loads. According to the model, loads increase in higher ship speed and ice thickness combination, further south, later in the summer and in higher temperatures.