With a scale model of tuned liquid multi-column damper (TLMCD) and floating substructure established, experiments were carried out in a flume to study the control effect of TLMCD on the pitch motion response of the floating foundation under regular wave excitation. The numerical model was established and verified by OpenFOAM. The coupling mechanism of TLMCD and floating foundation was analyzed from the aspects of flow field, hydrodynamic loads, floating body motion and damping force. The results show that TLMCD has the best pitch suppression effect under resonant excitation, and that the liquid with a mass ratio of 2% reduces the maximum pitch response of the floating body under resonant excitation by 10.84% to 18.53%, and achieves at least 7.32% damping effect in the range of 0.9<T/T₀<1.1. By numerical method, it was observed that under the condition of resonance, the hydrodynamic force generated by tank sloshing took up 89.52% of the time to do positive work, and that the sloshing of liquid in the liquid columns periodically provided reverse damping moment for the floating body.

In order to clarify the influencing factors of the amplitude of local ice pressure and pressure-area curve of the upright wide structures, the calculation method of the local ice pressure in ISO 19906 was firstly analyzed in this paper, and its limitation was found. Secondly, the discrete element method was used to simulate the interaction between different sea ice conditions and multi-scale structures. It is found that the amplitude of local ice pressure increases with the increase of ice thickness and decreases with the increase of structure width. The amplitude and standard deviation of local ice pressure decrease with the increase of width-thickness ratio, showing obvious scale effect. Finally, the influence of ice thickness and width on pressure-area curve parameters was studied by square-averaging method, and one similar working condition was selected to compare with that of ISO specifications. The rationality of the discrete element simulation method in dealing with the local ice pressure-area curve was verified, which provides a certain basis and reference for the ice resistance performance analysis and structural design of the platform.

In order to evaluate the 3D effects of wave glider spring hydrofoil mechanism in waves on its dynamic performance, a numerical computational model of the wave glider spring hydrofoil mechanism was developed. Based on the overset mesh technology, the dynamic performance between 2D and 3D hydrofoils was analyzed and studied by using CFD FLUENT software. The results show that due to the limited span of the 3D hydrofoil, the tip vortex phenomenon is generated at the wing tip, resulting in reduced hydrofoil dynamic performance, and that the forward propulsion efficiency of the 3D hydrofoil is reduced by 22.1% compared with that of the 2D hydrofoil. Then, the bionic principle was used to design the wave glider bionic hydrofoil. It is found that the bionic hydrofoil reduces the loss of hydrofoil power performance by the tip vortex, while the forward thrust of the bionic hydrofoil is increased by 17.6% and the efficiency by 10.4% compared with the 3D hydrofoil of the same spreading chord ratio. Finally, the experimental comparison shows that the CFD simulation data and the experimental data have the same trend, and the reliability of the CFD simulation model is verified.

Path planning is one of the key technologies for autonomous navigation of unmanned vehicles. A good path planning method is of great significance to the intelligent development of unmanned vehicles. In the existing path planning research, the maneuvering performance of unmanned vehicles is not considered. In order to make the planned path have shorter voyage time, shorter path length and better path tracking ability, it is necessary to combine the maneuvering performance of unmanned vehicles with the path planning algorithm. In order to accurately predict the ship maneuverability, the channel-type unmanned catamaran was taken as the research object, and simulation tests of three planar motion mechanisms were carried out by CFD technology. Simulation results were fitted with different hydrodynamic models, and corresponding hydrodynamic derivatives were calculated. The MMG model was used to establish a mathematical model of ship maneuvering motion to simulate the turning motion and Z-shape motion of the unmanned catamaran. The influence of different hydrodynamic models on the simulation results was analyzed, and the maneuvering pre-diction of the unmanned catamaran was realized.

The two compulsory conditions for boundary layer separation are fluid viscosity and positive pressure gradient. By designing the shape of a vehicle so that its surface has a negative pressure gradient area as large as possible, the flow transition and separation are delayed so as to achieve the purpose of drag reduction. Based on the theoretical flow non-separation shape design method of slender bodies, the shape of a vehicle with a critical speed of 100 m/s was designed, and numerical simulation was used to analyze its flow characteristics at different speeds and angles of attack. It is found that the simulation results at zero angle of attack are consistent with those of the theoretical calculation, which proves that the surface of the vehicle can be in a state of non-separation of laminar flow through the shape design. A small attack angle will not destroy the fluid adhesion state on the surface of the vehicle, but whirlpools will appear in the flow when the attack angle is greater than 2 degrees.

Aiming at the actual demand of improving the numerical simulation of unsteady submarine motion in maneuvering condition, the overset mesh was used to directly model six degree of freedom coupling motion of a submarine and the independent motion of each control surface, and the sliding mesh was used to directly simulate the propeller rotation at the stern of a submarine, so as to carry out the research on the numerical simulation of a generic submarine in self-propulsion and free running maneuvering conditions. Through the procedure of numerical simulation in typical working conditions, such as submerged self-propulsion, turning maneuver, zigzag maneuver, crashback, etc., the issues of submarine/propeller/rudder hydrodynamic coupling modeling and PD (proportional-derivative) numerical control realization of autopilot in maneuvering condition were emphatically solved, and the technology of free running submarine model numerical simulation based on overset mesh was established. At the same time, the surrounding flow phenomenon and the time-history change process of kinematics and dynamics parameters of the submarine in maneuvering condition were analyzed. By comparing the numerical simulation results of typical dynamics parameters with the model test results, the practicability of the approach for engineering prediction was verified. The research can provide a guidance for the prediction and evaluation of submarine maneuverability and seaworthiness. It is beneficial for the improvement of free running submarine model tests.

Movement of a revolution body at high speed with an angle of attack induces a large-scale asymmetric cloud cavitation flow attached to the surface of the revolution body. The large pressure induced by the interface instability at the end of the cloud cavitation has an important impact on the performance of the revolution body, which is an important basic theory problem in the development of revolution bodies. This paper combs the relevant research on asymmetric cloud cavitation flow of revolution bodies, introduces the experiment and numerical simulation method research on asymmetric cloud cavitation flow mechanism of flow control, and flow field structure and interface stability of the asymmetric cloud cavitation, analyzes the future development trend, and offers some suggestions of the main research directions in future.

A dynamic numerical analysis model for hang-off evacuation down-hole riser was established with coupling the longitudinal and transverse deformation. The hard hang-off and soft hang-off boundary conditions were given considering the horizontal evacuation and vertical heave movement of the platform. The down-hole riser model was discretized by the finite element method and solved by the Newmark-β method. An experiment for the hang-off riser was conducted to verify the accuracy of the numerical model. For a deep-water well in the South China Sea, the dynamic characteristics of hard hang-off and soft hang-off risers coupling the longitudinal and transverse deformation were analyzed. The research results show that the lateral deformation of the hang-off evacuation riser presents a wave shape, and the vertical deformation vibrates periodically with the platform heaving. The maximum lateral and longitudinal displacements of the down-hole risers appear at the bottom of the riser under both hard and soft hang-off conditions. The displacement of the down-hole riser under the hard hang-off condition is small near the top, where the bending moment reaches a maximum value. The displacement of the down-hole riser near the top increases sharply under the soft hang-off condition, but the maximum bending moment appears near the water surface. The range of longitudinal displacement envelope of the hang-off evacuation riser increases gradually from top to bottom, while the range of axial tension envelope increases gradually from bottom to top. Besides, the minimum tension of the down-hole riser under hard hang-off conditions is negative near the top, where obvious axial compression with the risk of buckling failure appears.

The potential-viscous flow coupling method, which combines the potential flow method with the CFD method, has gradually attracted attention in solving issues of wave evolution and wave structure interaction in marine engineering field. The potential-viscous coupling method can effectively reduce the computational cost of numerical simulation while ensuring the calculation accuracy, making it possible to achieve fine simulation of fluid-structure coupling on a real scale. In this paper, the state of art of the potential-viscous flow coupling method for marine engineering hydrodynamic applications are reviewed. Two types of coupling methods, domain decomposition and functional decomposition, are discussed to analyze advantages and challenges of the coupling method.

Ventilation law of supercaviting vehicles plays an important part in cavity shape control. This paper presents the development of an experimental method in high speed water tunnel to study the supercavity stability which describes the relationship between cavity shape and ventilation rate. An empirical formula was established based on test results of cavity shape and ventilation flow rate under different cavitator sizes and angles of attack of the model. By making analysis and comparison of the experiment results with and without tail wings, the influence of tail wing on ventilation law was preliminarily obtained. The results show that ventilation rate needs to be kept in certain range in order to maintain a steady and smooth ventilated supercavity.