In this paper, numerical simulation and comparative verification tests of two ship models in heading regular waves, which was recommended by ITTC, were conducted. Based on the Reynolds time averaged method for solving the N-S equation, a calculation method of wave interference and 6DOF motions for two ships under horizontal mooring constraints was established. With the model and mooring parameters in the test taken as inputs, the numerical simulation of wave interference between the two ships under typical wave conditions was carried out. The time curves of 6DOF motions, wave surface rise between the two ships and mooring tension were obtained and compared with the results of model tests. The comparison shows that the motions of surge, heave, roll and pitch as well as the wave surface rise of the comparative conditions (wave period: 1.5 s) are in good agreement with the test results. There are relatively large errors in motions of sway and yaw compared with the test results, because these motions result from the coupling of wave system interference between two ships and mooring constraints, and the superposition of multi-factor simulation errors reduces calculation accuracy.

The line spectra noise radiated by cavity flows greatly deteriorates the acoustic stealth of naval ships, whose formation mechanisms are related to the flow and acoustic modal effects, as well as the acoustic-vibration and flow-sound coupling effects. In this paper, the transient flow, equivalent sound source and acoustic fields of the simple square and typical cavity flows were numerically simulated, based on the CFD/CHA hybrid approaches. The applicability of the numerical methods was verified by comparison with experimental data of water tunnel test. The characteristics of the flow and acoustic modes of the cavity flows were concluded, particularly the effects of the acoustic-vibration coupling of elastic cavity walls and the complexity of cavity inner shapes upon the acoustic mode frequencies were quantitatively calculated. The important regularity, which the line spectrum induced by the effect of the first acoustic mode is the "decisive line spectrum" in the far-field radiated noise spectrum, is summed up. The tendency of the acoustic mode frequencies to shifting sharply towards lower frequencies under the actual cavity conditions was analyzed, indicating the necessity of avoiding the flow-sound coupling. The necessary condition of the cross-sectional area ratio for the related acoustic experiments in water tunnels was quantitatively established through an analytical solution. The research has an important guiding value for the designs of experimental modals.

In order to accurately evaluate the influence of irregular current load on the safety of semi-submersible platform towing operation, based on the coupled time-domain analysis theory and potential flow theory, this paper presents an analysis of the influence of different current velocities and flow angles on the dynamic response and towing tension of semi-submersible platform towing under the same wave environment and towing speed through the semi-submersible platform-towing-tug coupling dynamic model. The results show that under certain wind and wave conditions, the current velocity and flow direction angle have little influence on the heave and pitch of the platform, but have great influence on the roll and towing tension. With the increase of flow velocity and flow direction angle, the platform heave gradually increases, with the platform roll and pitch angles under different flow velocities and flow angles fluctuating within ± 3.5°. The maximum towing tension is obtained when the flow angle is 90°. Therefore, the angle of 90° between the heading and the flow direction should be avoided during the towing process, and it is not suitable for towing when the flow rate reaches 1 m/s.

In ships’voyaging conditions, the global hull girder is subjected to the combination action of cargo loads on ship decks, still water moment and wave moment on hull bottom, and correspondingly partial ship stiffened panels suffer complex loads including longtudinal, transverse forces and pressures. Lateral loads could to some degree influence the ultimate compressive strength in the longitudinal and transverse directions. Thus, it is needed to establish the interaction formulae of ultimate strength for stiffened panels under combined loads. The stiffened panel structures in hull bottom of bulk carrier was selected as the research object. Based on the two-bays-and-two-spans geometrical extent model of stiffened panel with periodic boundary conditions, a nonlinear numerical method was employed to investigate the interaction formulae of ultimate strength for hull girder structures under longitudinal, transverse and lateral loads. It is found that lateral loads always reduce the ultimate strength in longitudinal and transverse directions, meanwhile the larger the lateral loads are, the more the ultimate strength decreases. It is suggested to increase stiffener size and plate thickness for improving the longitudinal and transverse ultimate strength under lateral pressures, respectively. The interaction formulae were developed to assess the ultimate strength of stiffened panels under combined loads and the interaction relationship of ultimate strength under multiple loads. It can be used to perform rapid calculation on the structural strength design under complex combined loads.

Flow-induced vibration of valves is the main source of vibration and noise in pipeline system. The characteristics of flow-induced vibration of liquid valves are important for analyzing vibration and noise in pipeline system, designing and establishing low-noise system. By taking ball valve as the research object, a three-way spring and beam element model was used to simulate the elasticity bolt connection of ball valve inlet and outlet flange end face. Constrained boundary conditions of valves under actual working conditions were established though correcting constrained boundary stiffness with measured dry-humid modal results. Based on Finite Element Method (FEM) and Computational Fluid Dynamics (CFD) theory, the flow-induced vibration analysis model of ball valves was established to research the flow field and fluid-induced vibration characteristics and the correlative influence law of ball valve under variable opening and mass flow conditions. The results show that the three-way spring and beam element model can better simulate the actual installation boundary conditions of ball valve in water pipe. With the decrease of ball valve opening or the increase of mass flow rate, the disturbance of flow field becomes more obvious, and the vibration acceleration level at each measuring point increases.

Based on the STAR-CCM+ software, CFD-DEM method was used to simulate the process of a type of an actual built transport ship sailing in a brash ice channel. The influence of different drafts on the resistance performance of the ship was studied. The interaction between the ship and water was obtained using CFD method. A numerical brash ice particle model was established using DEM method, the ship-ice collision phenomena and the brash ice resistance were studied. The results show that the distribution pattern of brash ice particles obtained based on the above method agrees well with that of the test conducted in Hamburg Ship Model Basin (HSVA). The total resistance of the numerical prediction varies little from the model test results. Also, the numerical method performs much better than the FSICR empirical formula's prediction, which verifies the reliability of the present method. The ice resistance of the whole ship does not show a monotonically decreasing trend with the decrease of draft, but increases significantly when a specific draft is reached. At a small draft, the change in trim has a little effect on the ice resistance of the whole ship, but has a large effect on the proportion of ice resistances of the fore, middle, aft and bottom parts of the hull.

The Bend Stiffener (BSR) manufactured from polyurethane is generally used at the connection between nonbonded pipes and water surface platform. It is necessary to predict curvature distribution of BSR. This paper proposed a curvature prediction model that took into account the stress-strain nonlinearity of BSR and bending hysteresis of nonbonded pipes. Then, a nonlinear regression method was used to identify the Prony parameters which could be used to describe the stress relaxation behavior of BSR materials. Then the stress relaxation model was substituted into the curvature prediction model, so that the effect of BSR’s stress relaxation could be taken into considernation. Finally, an optimization criteria was proposed for BSR and conducts parameter analysis on regular shaped BSR.

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 .

Submerged waterjet propulsion is a variant of conventional waterjet propulsion, whose inlet duct is fully integrated into the bottom plate of hull, reulting in a more complex coupled flow field behind. In order to meet the development requirements of submerged waterjet propulsion, the differences in mechanical control system between two types of waterjet propulsion were studied. Numerical simulations were conducted for both conventional and submerged waterjet propulsion at designed speed point. The comparison results show that submerged waterjet propulsion has larger flow obtaining area, higher inlet duct efficiency and less impact on the ship motion while the thrust reduction fraction is larger.

Conventional resistance prediction method of proxy models takes main scale ratios, ship form coefficients, and other similar parameters as inputs. Compared to CFD calculations, in which the complete hull form is used as input, prediction method with lower information density of proxy models results in lower prediction accuracy. In this paper, a high-dimensional, high-precision resistance prediction method was proposed for ship hulls using 4108 sets of complete hull geometry feature tensors as input and employing neural networks as proxy models. The total resistance coefficient of the ship was taken as the output. Dimensionless treatment of the hull forms was conducted at first and feature tensors were extracted as inputs. Next, a neural network model was constructed, comprising input layers, hidden layers, and an output layer. Finally, the feature tensors of the hull forms and the corresponding total resistance coefficients were fed into the neural network, and the model was trained using error back propagation until the loss function converges. The research findings in this paper can provide theoretical and technical support for high-dimensional proxy model-based resistance performance prediction.