In general, in the calculation of the hull girder ultimate strength and the residual strength, the bilge plate should be considered as a hard corner element in Common Structural Rules for Bulk Carriers and Oil Tankers, but the specific conditions are not clear. In this paper, a bilge curved plate with typical geometric shape inside and outside the midship region was studied by means of the buckling capacity evaluation method and the nonlinear buckling finite element analysis method. The brief conditions in which the bilge plate can be regarded as a hard corner element in the calculation of hull girder ultimate strength and residual strength required by common structural rule were obtained.

In this paper, the dynamic response characteristics of aluminium honeycomb sandwich panels under repeated rigid wedge impacts and ice wedge impacts were experimentally studied by using the horizontal impact test apparatus. The impact force-displacement curves and the structural deformation properties were obtained. Results show that with the increase of collision numbers, the peak value of collision force increases continuously, the contact time decreases significantly, the local indentation and global bending deformation of face sheet increase gradually, the compressive deformations of the honeycomb cores enlarge gradually and finally the densification phenomenon appears. Due to the ice fragmentation phenomenon in the collision process, the contact area under ice wedge impact increases. Compared with rigid wedge impact, the midpoint permanent deflection of top facesheet under ice wedge impact is smaller, but the local damage area is obviously larger. With the increase of collision numbers, the plastic accumulated deformation of honeycomb sandwich panel evolves from a plastic hinge line to an elliptic plastic zone.

The calculation method for the slamming load of manned submersibles floating on the water surface at zero speed was studied in this paper, the calculation processes for predicting slamming pressure were provided based on the frequency domain and time domain response, the calculation formula for the extreme value of slamming pressure was derived, and the frequency domain and time domain slamming pressure prediction on a certain manned submersible were performed. According to the calculation results, the effects of ship motion and wave surface inclination on the water entry angle were not considered in the frequency domain method, so it is only suitable for ships whose motion responses have little effect on the water entry angle. For a manned submersible, the motion response is significant, which will reduce the entry angle and lead to obvious increase of the slamming pressure coefficient. At this point, the slamming load should be calculated based on the time domain method to avoid the underestimation of the slamming load. At zero speed, the slamming pressure of the submersible on the wave facing side is significantly greater than that on the other side. So the slamming pressure on the stern is greater in following waves, while the slamming pressure on the bow is greater in head waves.

In order to study the vortex-induced motion characteristics with coupled multi-degrees of freedom of Spar platforms under a uniform flow, a numerical model about the vortex-induced motion of a Spar platform considering fluid-structure interactions was established based on STAR-CCM+, and the coupling effects of five-degrees of freedom (surge, sway, heave, pitch and roll) were investigated. The results show that the vortex-induced resonance can be observed obviously at three degrees of freedom (sway, heave and roll), and the velocity interval of vortex-induced resonance is the same at the two degrees of freedom (heave and roll). Meanwhile, the coupling effects between sway and roll are obvious. In the case of sway resonance, the relationship of the dominant frequency between sway and roll is 1:1, and in the case of roll resonance, the secondary peak frequency of sway is the same as the dominant frequency of roll. Moreover, there are complex nonlinear coupling relationships among the three degrees of freedom (surge, heave and pitch), not only the dominant frequency of surge and heave always exists in the pitch spectrum, but also the coupling effects between pitch and surge, pitch and heave are various in the different ranges of reduced velocity.

The development of the potential flow solver for the CAE software of a ship requests a reliable method to solve the potential flow. The numerical method of the diffraction force with a three-dimensional time-domain panel method was studied. With a three-dimensional time-domain Green function introduced, its Rankine part was calculated by Hess & Smith’s method while its free-surface memory part was calculated by the method of Beck team from the University of Michigan, followed by the derivation of the diffraction impulse function in the mathematical expressions for making the program. Then the source method was used to calculate the source and the diffraction potential, and the diffraction potential force was obtained by integrating the pressure around the floating body. Finally, the diffraction force and Froude-Krylov force were calculated with the Wigley I ship. The verification was carried out by comparing the results with the published experimental and numerical results. The method and the code in this paper are reliable for developing the potential flow solver of the CAE software and predicting the nonlinear stability failure models in waves.

Polar ship icing is formed when supercooled droplets from the air or seawater fall onto ships. After the crystal nuclei in the supercooled droplet are formed, they solidify and release heat, so that the temperature returns to the freezing point and forms an ice water mixture, which is called recalescence. This process is the beginning of the freezing stage. The phase field method was used to simulate the recalescence process of water under different undercooling conditions, and the icing morphology and ice-phase proportion after recalescence were studied. The results show that the undercooling has a certain effect on the results of recalescence. The dendrite growth rate in the process of recalescence is fast at first and then becomes slow. The proportion of ice phase increases with the increase of undercooling. When the undercooling increases from 30K to 45k, the proportion of ice phase increases from 11.92% to 29.17%.

High-precision monitoring of the thrust of the propulsion shafting is of great significance for the ship rapidity prediction, hull-engine-propeller matching, and health management of the shaft. However, for the super-long propulsion shafting, because of its large span, small slenderness ratio (ratio of the radius to the length of the shaft) and large thrust, the shaft will produce severe bending-longitudinal coupling nonlinear deformation, which will have an important influence on the thrust measurement based on deformation information such as strain or displacement. Therefore, the bending-longitudinal coupling nonlinear effect of the propulsion shafting on the thrust measurement accuracy was studied. Considering the Von Karman nonlinear displacement-strain relationship, a nonlinear mechanical model of the propulsion shaft was established by using the Hamilton variational principle combined with the finite element method. The bending-longitudinal coupling effect on the displacement, strain and thrust measurement errors was studied. The results show that at low rotation speeds, the bending-longitudinal coupling effect is weak and has little effect on the thrust measurement. However, at high rotational speeds, ignoring the bending-longitudinal coupling effect will cause large measurement errors (the error can reach 13.95% at 240 r/min). Besides, the closer the measuring point is to the propeller, the stronger the bending-longitudinal coupling effect will be, and the larger the thrust measurement errors will be. Therefore, arranging the measuring point near the thrust bearing at the front end of the shaft can effectively reduce the measurement errors caused by the bending-longitudinal coupling effect. The research results have guiding significance for the thrust measurement of super-long shafts with large spans and small slenderness ratios.

Offshore wind energy resources is richer than land wind energy, and water depth of the continental shelf in China's waters increases slowly as the distance offshore increases. Based on the characteristics, how to optimize the design of mooring systems to adapt to the water depth conditions in China is one of the major problems encountered in the development of floating wind turbines. In this paper, a 5MW-OC4 semi-submersible floating wind turbine was used as the research object, the floating wind turbine was moored by suspended chain lines, and the frequency domain and time domain calculations of the floating wind turbine were performed under 40 m water depth in a sea area of Bohai Sea using SESAM software. Mooring accessories were used separately and in combination for parameter sensitivity analysis, and then the mooring system was optimized by combining buoys and clump weight blocks. The results of the study show that under shallow water conditions, the combination of mooring fittings has the same effect on the overall response of the floating wind turbine as changing the same mooring parameters when used alone, but the effect of changing the mooring parameters on the optimisation of the performance of the mooring system is more obvious when used in combination, the optimisation difference in the mean value of the counterweight block position parameters when used in combination can reach 15.7%, and the optimisation difference in the longitudinal oscillation, longitudinal rocking and the tension response are all within 10% of each other. The optimisation difference of longitudinal oscillation, longitudinal rocking and tension response is basically within 10%. Therefore, choosing a reasonable combination of accessories can significantly change the overall characteristics of the floating system and affect the safety and cost of the system.

In this paper, for the demand of low-frequency hydrodynamic noise control in submarine sonar dome, based on the coupled vibration equations of the plate and acoustic cavity, the hydrodynamic self-noise calculation model of the multi-layer composite plate was established by using the acoustic vibration transfer matrix, modal expansion method and wave vector-frequency spectrum of turbulence boundary layer pressure. According to the analysis of dynamic vibration absorption characteristics, the vibration and noise equations of the plate under the control of distributed energy absorption unit were formed, and the hydrodynamic self-noise of the distributed power absorption composite sonar domes was evaluated. The hydrodynamic self-noise reduction effect was verified through the large cavitation channel tests, providing technical support for the design of advanced low-noise sonar domes.

A rigid polyurethane foam (RPUF) buffer was designed to reduce the load of a projectile during high-speed water entry. Based on the Hopkinson compression bar technique, the density and strain rate effects of RPUF under impact loading were obtained, and its macroscopic constitutive model was established. Based on the Arbitrary Lagrangian-Eulerian (ALE), the numerical simulation model of the projectile during high-speed water entry was established. The numerical simulation of the projectile during high-speed water entry with different densities of RPUF was carried out. The dynamic failure process and motion parameters of the buffer during the water entry were obtained, and the influence law of the density and thickness of RPUF on the load reduction characteristics was analyzed. It can be found that the strain rate effect of RPUF is not obvious, but the density effect is obvious, and that, as the density and thickness of RPUF increase, the load reduction performance of RPUF increases.