Research on the Influences of Broken Ice Parameters on Maneuverable Forces of Ice-Going Ship Oblique Sailing

The broken ice is one of the most common ice conditions for ice-going ships, and the research of ship maneuvering movement in broken ice field can improve sailing safety. In this paper, the discrete element method (DEM) was adopted to study the maneuverable forces, including resistance and transverse force, of ice-going ship oblique sailing in broken ice fields. First, the Araon model tests data of Korea Institute of Ocean Science & Technology (KIOST) was used to verify the ice resistance of direct sailing under different ice sizes and model speeds, and the numerical results are in good agreement with the test results. Second, the influences of broken ice parameters (including concentration, thickness, and shape) on ship-ice interaction and maneuverable forces distribution were researched. The maneuverable forces on the ice-going ships are mainly from the ship-ice interaction. The time history curves of maneuverable forces were analyzed from the average value of maneuverable forces, the average value of peak maneuverable forces, and the number of peaks. Besides, the parameters of broken ice have a heavy influence on the movement of broken ice around the hull, such as accumulating and sliding. The analysis of the broken ice movement contributes to understanding the influences of broken ice parameters on ice-going ships.

Numerical Simulation of Model Test in Pre-Sawn Ice by CFD-DEM Coupled Method

Arctic shipping activities have been steadily increased due to global warming and economic benefit. As a result, there are more demands to estimate the ship performance in various ice conditions at the early design stage. In this paper, a CFD-DEM coupled approach was applied to estimate the ice resistance and broken ice behavior around the hull including hydrodynamic interactions. For the simulation, the moving ship in the stationary ice field was implemented using the overset grid technique. The estimated ice resistance as well as ice behaviors around the hull from the simulations were compared with model test results and underwater videos of the same vessel in a similar ice condition. The results demonstrated good agreement with model test measurements and further improvement for actual application was discussed in the paper.

Cavitation and Induced Excitation Force of Ice-Class Propeller Blocked by Ice

The presence of broken ice in the flow field around a propeller causes severe blade erosion, shafting, and hull vibration. This study investigates the performance of the propeller of a ship sailing in the polar regions under the propeller–ice non-contact condition. To this end, we construct a test platform for the propeller-induced excitation force due to ice blockage in a large circulating water channel. The hydrodynamic load of the propeller, and the cavitation and propeller-induced fluctuating pressure, were measured and observed by varying the cavitation number and ice–propeller axial distance under atmospheric pressure and decompression conditions. The results show that the fluctuation range of the blade load increases with a decrease in cavitation number and ice–propeller axial distance. The decrease in the cavitation number leads to broadband characteristics in the frequency-domain curves of the propeller thrust coefficient and blade-bearing force. Under the combined effects of ice blockage and proximity, propeller suction, the circumfluence zone around the ice, and the Pirouette effect, propeller–hull vortex cavitation is generated between the ice and propeller. The decrease in cavitation number leads to a sharp increase in the amplitude of the high-order frequency of the propeller-induced fluctuating pressure.

Field test of herder and controlled burning of spilled oil in Kazakhstan

ABSTRACT Recent years have seen renewed interest in the viability of using herding chemicals in conjunction with in-situ burning. NCOC, an operator in the shallow north Caspian Sea, undertook herder research as an extension to studies performed under the Arctic Response Technology Joint Industry Programme (JIP). The purpose was to investigate the feasibility of using herders as part of their response toolkit. Laboratory tests were performed in Kazakhstan on weathered Kashagan export crude oil, using two herders listed on the US NCP Product Schedule. Results were positive and it was considered that a reasonable size test spill under realistic conditions was required to verify laboratory work. In November 2018 a field trial was undertaken in the boat basin at Damba in western Kazakhstan. A volume of 400 litres of artificially weathered Kashagan crude was pumped onto the water surface and allowed to spread. Air and water temperatures were just above freezing and a small amount of ice was present due to overnight low temperatures. The test was recorded by an unmanned aerial vehicle, using thermal IR and 4K video. After the oil had been allowed to spread out to be <1 mm, i.e. too thin to sustain combustion, a small boat was used to spray Siltech OP-40 herder around the periphery of the oil. After less than five minutes the effect of the herder became apparent. The oiled area was observed to begin contracting. A member of the boat crew successfully placed an igniter into the thick oil. A plume of black smoke was produced and the oil burned vigorously with flames of 2 to 3 metres high for approximately 8 minutes. After the burning had finished a visual inspection showed a relatively small quantity of oil residue. Pre- and post-environmental monitoring of the test site was undertaken. Based on the success of the test, the next steps are to develop a formal methodology for the inclusion of herders in the list of approved oil spill treatment products. It will then be possible to incorporate the technique into contingency plans using NEBA/SIMA justification. This will have the potential to improve the response options and speed of response to incidents in broken ice or open waters.

The MALINA oceanographic expedition: how do changes in ice cover, permafrost and UV radiation impact biodiversity and biogeochemical fluxes in the Arctic Ocean?

The MALINA oceanographic campaign was conducted during summer 2009 to investigate the carbon stocks and the processes controlling the carbon fluxes in the Mackenzie River estuary and the Beaufort Sea. During the campaign, an extensive suite of physical, chemical and biological variables were measured across seven shelf–basin transects (south–north) to capture the meridional gradient between the estuary and the open ocean. Key variables such as temperature, absolute salinity, radiance, irradiance, nutrient concentrations, chlorophyll a concentration, bacteria, phytoplankton and zooplankton abundance and taxonomy, and carbon stocks and fluxes were routinely measured onboard the Canadian research icebreaker CCGS Amundsen and from a barge in shallow coastal areas or for sampling within broken ice fields. Here, we present the results of a joint effort to compile and standardize the collected data sets that will facilitate their reuse in further studies of the changing Arctic Ocean. The data set is available at https://doi.org/10.17882/75345 (Massicotte et al., 2020).

Investigation of the Effect of Block Size, Shape, and Freeze Bond Strength on Flexural Failure of Freshwater Ice Rubble Using the Discrete Element Method

As part of the Mechanics of Ice Rubble project, recent experiments have been carried out to study the strength and failure behavior of ice rubble beams and the freeze bonds that form between individual ice blocks. In this study, we present results obtained from a newly developed model for the three-dimensional (3D) discrete element modeling (DEM) open-source code LIGGGHTS. The ice model contains normal and shear springs that operate between neighboring particles which are bonded or that overlap due to compressional stresses. Energy dissipation is accounted for by using a viscous damping model. Using this DEM model, medium-scale freshwater ice rubble punch tests have been simulated. Rubble specimens were generated by “raining” individual DEM ice pieces into a rectangular form and compacting the rubble mass to achieve the target porosity. Before the compacting pressure was removed, bonds between contacting blocks were introduced with parameter values based on representative freeze bond experiments. The rubble beam was then deformed by pushing a platen vertically downward through the center of the beam until failure occurred. Two types of block size and shapes have been simulated: cuboid blocks generated based on the size distribution of the actual rubble, and rubble blocks generated by image processing of actual blocks of broken ice used in the comparison experiments. The mechanism of flexural rubble failure for both cuboid block [s4.2] simulations and empirical block [s4.3] simulations is in line with experimental results; however, the empirical block simulations provide a significantly better estimation of the failure force.