Riser deployment is an important step in deepwater drilling, during which the spider is the primary support of the riser system. At the same time, the harsh deepwater environment leads to a high risk of riser deployment. To ensure the safety of riser deployment, firstly, a joint distribution model of environmental parameters was constructed. Then, an intelligent prediction model of structural response based on IAGA-BRNN was determined. Finally, the method of structure reliability assessment for riser deployment was established combining Monte Carlo, and a case study was carried out. Results show that most parameters in the joint distribution model of environment obey Weibull distribution and Beta distribution. The prediction model proposed in this paper performs well in all the prediction indicators, and has a stronger prediction ability compared with the conventional prediction model. The equivalent stress and maximum axial force are the first and secondary limitation factors of the riser deployment. In addition, as the number of hang-off riser increases, the reliability is on the decline, and wave height is the main limiting factor of operational reliability.

Based on the principle of "attribute subdivision and knowledge encapsulation", the application process research of virtual test of ship resistance performance based on RANS equation by encapsulating virtual test expert knowledge was carried out, The application process of virtual test of ship resistance performance was established and compared to the physical pool model test process. Precise prediction of resistance performance can be carried out by only inputting the geometric surface and the main scale parameters of test object, which has the characteristics of high prediction accuracy and good effect. Compared with the traditional CFD resistance numerical calculation, the evaluation efficiency of ship resistance performance is greatly improved, the research cycle of ship performance is shortened, and the barrier to entry is significantly lowered .

A double-buoy floating breakwater and an oscillating buoy wave energy power converter were coupled into an integrated device. Based on the CFD technology, a numerical water tank was established to calculate and explore the energy capture efficiency and wave-dissipating performance of the integrated device. The results show that the floater motion in the cavity has strong nonlinearity. When the incident wave period is near the natural period of the cavity, the floater has the best energy capture efficiency, and the power generation and energy absorption efficiency can reach 2.4 times that of a single floater. In addition, the wave-dissipating performance of the integrated device is related to the wave steepness and the natural period of the structure. When the incident period is less than the natural period of the structure, the floating breakwater has a better wave dissipating effect on large steep waves; beyond the natural period, the floating breakwater will lose its excellent wave dissipation ability.

In order to investigate the impact of the blowing rate and sequence of the main ballast water tank on the emergency surfacing characteristics of submarines, Suboff was taken as the research object. Based on RANS equation and overall dynamic grid technology, a simplified high-pressure air blowing model of the main ballast water tank was combined to construct a simulated calculation model for the emergency surfacing motion of submarines. By linearly applying buoyancy, the submarine emergency surfacing motion parameters varying with time were obtained under different blowing rates, blowing sequences, and time intervals at an initial speed of 1m/s. The results show that the faster the blowing rate of the main ballast water tank is, the faster the hull water flows out, the smaller the amplitude of the pitch angle is, and the larger the amplitude of the roll angle is. Blowing out the water tank in the order of the bow, middle, and stern groups, as well as the middle, bow, and stern groups, results in a larger longitudinal angle amplitude and faster upward buoyancy compared to simultaneous blowing out. Blowing out the water tank in the order of the bow, middle, and stern groups, results in faster water output compared to that in the order of the middle, bow, and stern groups. Under the same blowing sequence, the longer the time interval, the greater the amplitude of pitch angle and the surfacing time with an interval of 1.0 s is earlier than the other two working conditions. In all operating conditions, the highest point of surfacing occurred at 7.08 s in the condition of blowing out the water tank in the order of the bow, middle, and stern groups with a time interval of 1.0 s, which is 1.21 earlier than simultaneous blowing. The research results have certain guiding significance for the pressure design of high-pressure gas in submarines and the blowing strategy for emergency surfacing of real submarine.

The fracture failure of ship structures often results from the combination of low cycle fatigue and cumulative plasticity. In order to study the low cycle fatigue crack growth and plastic zone size of a marine high-strength steel considering cumulative plasticity, the low cycle fatigue crack growth test of a marine high-strength steel CT specimen under tension-tension-cyclic load was conducted according to ASTM E647 standard, and the plastic zone size of crack tip under different crack lengths was measured by DIC method. By introducing Chaboche model, an extended finite element simulation method was established to obtain the plastic zone size at the crack tip for exploring the influence of different load factors on the plastic zone size. Then the effectiveness of the method was verified based on test data. Finally, based on the results of finite element calculation and Irwin model, a prediction model of plastic zone size at crack tip considering cumulative plastic strain was proposed, and a crack growth rate model based on plastic zone size was established.

Liquid sloshing load is one of the key loads for the structural design of tank in Liquefied Natural Gas (LNG) carrying vehicle. When the sloshing load is too large, it will lead to local damage of the tank structure, which will cause liquid leakage and even the overturning of LNG vehicle. In this paper, based on the previous numerical results, two kinds of wall structures, i.e. trapezoid and square, were proposed. Liquid sloshing in tanks with different wall structures was experimentally studied. For the free-surface evolution and the distribution characteristics of impact load, with the help of statistical analysis, the effectiveness of wall structures in suppressing liquid sloshing was qualitatively and quantitatively analyzed. The results show that the presence of wall structures has changed the flow field. And instead of direct impact by water, an indirect impact by gas-containing liguid occurs. During the sloshing and impact of air-containing liquid, a large number of air-liquid mixtures and bubbles are generated, effectively reducing the impact load. Furthermore, the square wall structure is better than the trapezoidal wall structure for suppressing impact load.

With the continuous development of large-scale offshore floating structures, the rain load of large-scale offshore floating structures in extreme environment has become one of the focus issues of designers. Based on the discrete particle model, the motion prediction of wind driven rain field was made and the distribution law of spatial characteristic parameters of rain field was quantified. The calculation formula of structural rain load was deduced, and the rain load prediction of offshore platform under different wind speed and rainfall intensity combination conditions was completed. The research results show that the rain load of offshore platforms under the action of DNV wind profile and Davenport wind spectrum follows Gamma distribution. Compared to the average wind load, when the rainfall intensity R is 800 mm/h, the significant value of rain load accounts for 5.07%, and the maximum value accounts for 8.87%; when the rainfall intensity R is 20 mm/h, the significant value of rain load accounts for 0.36%, and the maximum value accounts for 0.6%. The research results of this paper can provide guidance for the design of offshore structures and their mooring systems.

To solve the path tracking problem of ROV deep-sea mining equipment, where a Mining Robot (MRT) is towed by a Remote Operated Vehicle (ROV), the motion model of a simplified ROV deep-sea mining equipment was established first. Then, a path tracking algorithm based on Linear Model Predictive Control (LMPC) and Nonlinear Model Predictive Control (NMPC) was proposed. Different from the traditional Model Predictive Control (MPC), the proposed Double Model Predictive Control (DMPC) algorithm consists of two parts: (1) the LMPC controller of MRT for calculation of the speed control law of MRT, which is used to quickly converge the tracking error of MRT; (2) the NMPC controller of the ROV for calculation of the control input of the ROV, which is used to follow the speed control law of the MRT. In the design of DMPC, constraints of state quantity and control quantity were considered effectively. In order to ensure the smoothness of ROV control input, the incremental control quantity constraint of ROV was introduced. Finally, simulation experiments were designed to verify the path tracking performance of MRT. Numerical simulation results demonstrate the effectiveness of the proposed algorithm.

A shallow water interface interference separation and sound field reconstruction method based on the equivalent source method was proposed. The combination of the ray acoustic virtual source method with the equivalent source method can effectively separate the impact of interface reflected sound in shallow water conditions, and accurately reconstruct the radiated sound field of structural sound sources. The virtual source method model was briefly described in this paper, the basic principle and algorithm implementation process of the interference stripping equivalent source method were given, the impact of different frequencies and holographic surface configurations on the algorithm was illustrated through simulation, and the advantages and applicability of this method compared to conventional equivalent source methods were summarized.

Abrupt annular shear flows induced by internal solitary waves will cause submersibles to produce a large depth drop and pitch motion, threatening the safety and operation performance of submersibles. Based on the velocity inlet wave generation method and overset grid technique of CFD, the motion response prediction method of submersibles in internal solitary wave was established. With the prediction results compared with the experimental results, it is proved that the method can accurately simulate the large amplitude motion of submersibles in internal solitary waves. Through the simulation analysis of motion process of unpowered floating submersibles at the stratified interface under the action of internal solitary waves, the mechanism of depth drop and pitch motion of submersibles in internal solitary waves was revealed, and the effects of stratified thickness ratio, wave amplitude and depth of navigation on the longitudinal motion of unpowered floating submersibles were investigated. The results show that the amplitude of depth drop and pitch of the submersibles in internal solitary waves were determined by the wave amplitude and the maximum slope of wave surface; The factors such as amplitude, stratified thickness ratio and depth of navigation have great influence on the longitudinal motion property of submersibles.