When using the circumference crack method to calculate the ice load, the size of the circumference crack is usually determined by an empirical formula, but this can introduce many uncertainties to the selection of input parameters.

To accurately determine the size of circumference cracks, we propose a method of recognizing ice circumference crack size based on YOLACT, which can identify ice in images taken with ships. We then detect the edge of the mask and obtain the shape of the ice cracks, and the ice breaking radius and angle can be estimated by fitting the cracks.

The results show that the accuracy of the ice breaking radius and angle estimated by the proposed method can reach up to 96.12% and 96.58% respectively.

This method can accurately determine the size of circumference cracks and assist in the initial design of marine structures in cold regions.

This paper aims to analyze the influence of polar low temperature environment and ballast water capacity on the dynamic change process of the temperature field in polar ship's ballast tank.

The volume of fluid (VOF) model was used to simulate the two phases of gas and liquid, and the standard k-ε turbulence model was used to simulate the fluid movement. The numerical analysis model of heat transfer in the ballast tank of polar ships was established to analyze the dynamic change process of the temperature field of the ballast tank at low temperature, and reveal the influence mechanism of multiple ambient temperatures and multiple loading heights on the temperature field of the ballast tank.

With the continuous occurrence of heat transfer, the temperature in the area above the waterline of the side ballast tank decreases rapidly, and the cooling area extends laterally to the cabin and downward along the bulkhead respectively. When there is more ballast water, the temperature field in the cabin is relatively stable due to the large heat capacity of water, but the air heat capacity is low and the temperature field changes greatly, which is prone to cyclones and further affects the temperature field distribution in the calculation domain. Under the condition of the same ballast water capacity, the lower the external ambient temperature, the greater the difference between internal and external temperatures, the more intense the heat exchange, and the faster the temperature of the ballast tank changes.

The VOF two-phase flow model and the standard k-ε turbulence model can better reveal the temporal and spatial evolution characteristics of the temperature field in the ballast tank in polar low temperature environment, and analyze the influence of internal and external thermal boundary conditions on the change of the temperature field in the ballast tank, which can provide necessary technical reference for the cold/freeze protection of polar ships' ballast tanks.

In order to study the distribution of ship ice pressure during the interaction between an icebreaker and pack ice, a numerical simulation analysis is carried out for polar ships in pack ice channels.

The discrete element method (DEM) is used to model the ship and pack ice. It is assumed that the pack ice is composed of an ideal two-dimensional disc, and the effects of the ocean current on the buoyancy, drag and additional mass of the pack ice are taken into account. The numerical model is validated by comparison with the experimental results of an MT Uikku model, and the effects of different speeds and ice conditions on the ship ice pressure in the pack ice area are analyzed.

The results show that the ice load is mainly concentrated on the bow of the ship when it moves in the pack ice channel. The ice pressure in the bow area increases with the increase in ice thickness, speed and the density of pack ice, among which ice thickness is the most important factor affecting the amplitude of the ice pressure. The ice pressure in the pack ice area has the greatest influence on the ice pressure in the bow area, and the ice pressure in the bow transition area has a significant effect.

The numerical analysis method can provide certain references for the safe navigation and structural design of polar ships.

This study aims to investigate the dynamic coupling effect of "hull-fender-dock" during ship berthing.

Using the nonlinear finite element method, a port side and fender structure finite element model is established to simulate the dynamic evolution of speed, stress and energy during ship berthing.

The results show that when the fender makes contact with the dock, the ship's speed decreases to zero and the dynamic deformation and interaction force of the fender structure are at their maximum. When the ship is berthing, the fender shows strong energy absorption capacity, accounting for about 70% of the initial total kinetic energy of the ship, and the hull structure is well protected.

Further analysis indicates that, with the improvement of the initial berthing speed, port protection efficiency shows a decreasing trend. The ultimate berthing speed of the target ship of this study is 2.5 kn, and the recommended safe berthing speed is 2 kn. The results of this study can be used as a reference for ship berthing speed limits and hull structure energy absorption design.