Based on the boundary data immersion method (BDIM) and the fluid-structure coupling algorithm for rigid body motions, a numerical program for the vertical water-entry of a sphere was developed. The accuracy and effectiveness of the numerical method were verified by comparison with the experimental results. Based on the analysis of the numerical calculation results, the cavity development and corresponding flow structures with different impact velocities during vertical water entry, as well as the development of the splash were obtained. Different vortex identification criteria were adopted to investigate the development of vortex structures. The results show that the impact velocity of the sphere has a significant effect on the closure of the splash, the cavity shape and the evolution of the flow structures inside the cavity. The Q criterion can identify the complex vortex structure more accurately, and the entry velocity of the sphere will affect the vortex intensity inside the cavity.

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, 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.

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.

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.

Ice ridges are one of the typical features of polar ice underlying surface. Understanding the interaction between ice ridge and fluid flow is important for the navigation of submersibles. Five groups of typically spaced ice ridges were established based on the polar field data to investigate the influence of ice ridges on the fluid flow beneath the ice surface and its influence range. By solving the steady-state Reynolds stress equation model (RSM) through Fluent software, the effect of ice ridge spacing on fluid flow beneath the ice was studied. The relationship between spacing and wake vortex oscillation was explored. The radiation depth of ice ridge interference with the ice flow field was also studied. The numerical result shows that the continuous ice ridges have a tensile effect on the tail vortex. Depending on the level of interference, radiation depth can be divided into three ranges: strong radiation area, stable radiation area and no influence area.

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.

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.

The bow configuration of the tumblehome hull has a certain influence on the motion and the characteristics of green water loads in waves. In this paper, based on the inclination angle of stem, three kinds of bow configurations with inclination angles of 30°, 45° and 60° were selected. The motion response of the tumblehome hull in regular waves and the load characteristics of green water were studied by using the CNT-CGFDM method. The simulation of object boundary and motion was realized by immersed boundary method, and the free surface was captured by THINC/SW method. The ship models with 45° and 60° inclination angles of stem were selected for model test. The numerical simulation results are in good agreement with the experimental results. The results show that the bow configuration has little effect on the motion response of the tumblehome hull in regular waves, and show that some local differences exist only in some sea conditions. It has a certain influence on the slamming load of green water on the tumblehome hulls. Compared with the configuration scheme with the inclination angles of 30° and 60°, the load performance of green water on tumblehome hull with the inclination angle of 45° is more excellent.

For a high-speed planing craft, remarkable variation of the sailing state may cause abnormal distribution of air-water on the bottom for numerical calculation. In order to match the mesh layout and free-surface, a numerical wave tank based on Reynolds-averaged Navier-Stokes (RANS) method was established with dynamic mesh and manual six degrees of freedom (6-DOF) motion model. The high-resolution interface capturing with volume-of-fluid model (HRIC-VOF) scheme was applied to calculate the bottom’s water-air distribution on the ship model. The influences of angle factor, sharpening factor, Courant number’s upper bound, Courant number’s lower bound and time step on the calculation results of water-air distribution and total resistance were explored. The comparison of calculation and experimental results indicates that the current method is feasible for high-speed crafts’resistance forecast and for capture of free-surface. The relative error is less than 4.5% for ship model’s velocity at 2-13 m/s when FV=0.96-5.78.