In cold regions, ice pressure poses a serious threat to the safe operation of ship hulls and fixed offshore platforms. In this study, a discrete element method (DEM) with bonded particles was adapted to simulate the generation and distribution of local ice pressures during the interaction between level ice and vertical structures. The strength and failure mode of simulated sea ice under uniaxial compression were consistent with the experimental results, which verifies the accuracy of the discrete element parameters. The crushing process of sea ice acting on the vertical structure simulated by the DEM was compared with the field test. The distribution of ice pressure on the contact surface was calculated, and it was found that the local ice pressure was much greater than the global ice pressure. The high-pressure zones in sea ice are mainly caused by its simultaneous destruction, and these zones are primarily distributed near the midline of the contact area of sea ice and the structure. The contact area and loading rate are the two main factors affecting the high-pressure zones. The maximum local and global ice pressures decrease with an increase in the contact area. The influence of the loading rate on the local ice pressure is caused by the change in the sea ice failure mode. When the loading rate is low, ductile failure of sea ice occurs, and the ice pressure increases with the increase in the loading rate. When the loading rate is high, brittle failure of sea ice occurs, and the ice pressure decreases with an increase in the loading rate. This DEM study of sea ice can reasonably predict the distribution of high-pressure zones on marine structures and provide a reference for the anti-ice performance design of marine structures.

In this study, the water entry of an air-launched underwater glider under wave conditions is numerically simulated by the computational fluid dynamics method. The numerical model is validated by the comparison of nondimensional water entry impact force with published experimental and numerical results. And the influence of water entry points, water entry angles, and water entry attack angles on impact force is studied, which provides guidance for the design of air-launched underwater gliders. The results show that the water entry point has a great influence on the peak value of vertical impact force. In the present study, the peak value of the maximum vertical impact force at different water entry points is almost twice the minimum peak value with the same water entry velocity. The water entry angle at the same water entry point has great influence on the peak value of horizontal impact force, which is mainly related to the horizontal component of the impact velocity. The greater the horizontal component of impact velocity, the greater the peak value of impact force. In addition, the attack angle hardly affects the water entry impact force of the glider with hemispherical head.

When a ship sails in an ice area, the ice could cause damage to ship hull and the propeller as well as the rudder. In the design process of an ice class propeller, the strength verification of the propeller has always been the focus of the design and research of the ice propeller. Based on the International Association of Classification Societies Unified Requirements for Polar Class (IACS Polar UR), it is required that the maximum torque from the propeller cannot exceed the required value to ensure the safety of the propeller shafting equipment. This paper investigates the hydrodynamic performance of the propeller under the condition of satisfying the propeller’s ice strength. A parametric propeller optimization design procedure was established in which the thrust coefficient and open water efficiency solved by CFD method were selected as the objective function and optimization target, the maximum ice torque was used as the optimization constraint under the condition that the ship’s shafting equipment remains unchanged, the propeller pitch, thickness, and camber at each radial direction were taken as the optimization design variables, and the optimization algorithm of SOBOL and NSGA-II was adopted. The interaction mode of propeller and ice was simulated by the method of explicit dynamics. The equivalent stress and displacement response of the blade during the cutting process of the ice propeller were calculated, monitoring the ice destruction process. The results show that the multi-objective Pareto optimal solution set of thrust coefficient and open water efficiency of the ice class propeller was formed at the design speed while maintain the maximum ice torque not exceeding the original ice torque.

The Energy Efficiency Design Index (EEDI) has been applied to ship carbon emission standards since 2013, ice ships subject to the Finnish Swedish Ice Class Rules (FSICR) also need to meet the requirements of EEDI. In this study, the engine power requirements by EEDI at different stages for the considered ice class ships with different ice classes (1C, 1B, 1A, 1A Super) are compared with engine power requirements obtained from the resistance calculated by FSICR or Lindqvist method. Three different bow shapes for the considered ice class ships and different pack ice coverage are studied. The results from FSICR or Lindqvist formula show that 1A Super ice classes for all considered bow shapes cannot meet the requirement by EEDI at Phase 2 and 3; For 1B and 1A class, some bow shapes can meet the EEDI requirement for all stages, but some cannot; For 1C class, all bow shapes can meet the EEDI requirements for all stages. The ship main engine power requirements under different pack ice concentration are studied and compared to EEDI requirements.

A pump-jet propulsion system is composed of rotor, stator, and duct. The stator has the front stator type and the rear stator type; the conduit also has the acceleration conduit and the deceleration conduit two forms. It is difficult to design and evaluate the performance of a pump-jet propulsion system because of its complex structure and many changes in component parameters. Due to the limitation of time and cost in the design process of the pump-jet propulsion system, it is difficult to find the optimal scheme in the design space. However, under the guidance of an optimization algorithm, the automatic optimization method can fill the design space with a large number of design schemes. In this paper, the geometry reconstruction technique, hydraulic performance evaluation technique and optimization technique of the pump-jet propulsion system are combined to realize the automation of the whole design process. Firstly, the geometric modeling of the pump-jet propulsion system is completed by a full parametric modeling method, and then the hydrodynamic performance of the pump-jet propulsion system is calculated based on the numerical simulation technique. The radial parameters in the fully parametric configuration of the pump-jet propulsion system were selected as the optimization design variables, and the hydro-dynamic performance was optimized as the objective function. Finally, the pump-jet propulsion system optimization design system was constructed by using the global intelligent optimization algorithm. This study provides a theoretical basis and technical guidance for numerical calculation and configuration optimization design of pump-jet propulsion system.