With the continuous development of offshore floating wind turbines, their positioning ability has gradually attracted the attention of academia and engineering. The freak wave is destructive to the floating structure because of its large energy, strong suddenness and prominent nonlinear characteristics. In this paper, the new Moray-Base floating wind turbine concept designed by Maridea Company is taken as the research object, and the finite element model with a mooring system is established based on the potential flow theory. In order to improve correct the accuracy of the numerical model, the physical model test of the pool was carried out, and five sets of mooring schemes were designed to study the positioning ability of the numerical model improved by the physical model test. This paper focuses on the motion response and mooring line tension characteristics of five mooring schemes under the action of freak waves, which provides a reference for the design of floating wind turbine mooring system.

In order to predict the second-order force and moment of ships sailing in waves, the fluid domain is decomposed into two parts (where the steady flow effects are considered in the internal one), and a multi-domain coupled hydrodynamic model is established based on the continuity of the flow field. Then a higher-order coupled method is developed, in which nine-node quadratic elements are employed to discretize the boundary, Rankine source is adopted to deal with the complex boundary condition near the ship and higher-order translating-pulsating panel source Green’s function (i.e., analytical integral of the Green’s function over the higher-order panel) is derived over the control surface. On this basis, formulas for second-order force and moment in oblique waves are established under the weak scattering assumption. A numerical program is developed to calculate and analyze the second-order wave forces in surge/sway and yaw moment of various ships advancing in different wave directions. The results show that the present method is more stable and accurate than the traditional higher-order translating-pulsating source method based on Gaussian quadrature formula, as well as the lower-order constant panel method. It is generally applicable to different ship types sailing in both head and oblique waves.

In turbulent channel flows, traditional Detached Eddy Simulation (DES) methods suffer from significant deficiencies in capturing detailed turbulent structures due to the improper allocation of modeling scales. DDES models fail to accurately predict the streamwise mean velocity and are prone to the problem of logarithmic layer mismatch. Although IDDES provides some improvements, it still shows considerable discrepancies in the prediction of second-order statistical quantities. As an improved hybrid approach, the Wall-Modelled Hybrid RANS-LES (WM-HRL) framework addresses this limitation by employing a predefined partitioning strategy to rationally allocate modeling scales between RANS and LES regions. This study systematically investigates the performance of the WM-HRL model in turbulent channel flow and compares its results with those obtained from DDES, IDDES, and direct numerical simulation (DNS) data. The findings demonstrate that the WM-HRL model can more accurately predict near-wall turbulent structures and Reynolds stress distributions, effectively overcoming the limitations of traditional DES methods in the near-wall region.

Buoyancy elements are primarily used to provide additional buoyancy to improve the tension distribution along the risers. Risers covered with buoyancy elements exhibit more complex fluid–structure interaction phenomena under ocean currents, and the current understanding of their hydrodynamic characteristics remains limited. This study conducted stationary towing tests on a rigid riser model covered with buoyancy elements. Based on the hydrodynamic unit formed by the riser-buoyancy system, the drag and lift characteristics in uniform flow were investigated for different spacing arrangements and diameters of the buoyancy elements. The time-frequency characteristics of the cross-flow lift were further analyzed using wavelet transforms. The main conclusions are as follows: compared with a bare riser, the drag coefficient of the buoyancy element decreases to approximately 0.9 due to the low aspect ratio; when the diameter ratio of the buoyancy element to the riser reaches 3.52 and both components operate at Reynolds numbers above 10⁵, the RMS lift coefficient of the hydrodynamic unit increases significantly, reaching up to 1.2 when the length ratio equals 1; the dominant frequency of lift on a riser covered with buoyancy elements exhibits time-varying jumps, with a wider fluctuation range than the vortex shedding frequencies of both the riser and the buoyancy element.

In this paper, the fluctuating pressure on the wall of turbulent boundary layer is studied. Based on the governing equations of the fluctuating pressure in the boundary layer, the unified dimensionless expression of the fluctuating pressure in the full wavenumber region is derived in detail, and the influence of Mach number on the self-spectrum and wavenumber-frequency spectrum of the fluctuating pressure is emphatically analyzed. The fluctuating pressure data of cylindrical boundary layer at different Mach numbers (0 < Ma < 0.176) were obtained by acoustic wind tunnel and water tank experiments. Based on the analysis of experimental data, the accuracy of the predicted Mach-number effect on fluctuating pressure is finally verified.

During maritime operations, ships are subject to wave-induced disturbances, resulting in complex multi-degree-of-freedom motions that severely affect the stability of ships during offshore operations. To address this challenge, this study proposes a CNN-BiLSTM hybrid prediction model for real-time ship attitude forecasting and designs a dual-layer Stewart platform compensation mechanism to mitigate ship motion effects. To overcome sensor latency and noise interference, 2011 ship attitude samples collected in the South China Sea were first filtered using a Savitzky-Golay (SG) filter. The processed data were then fed into the CNN-BiLSTM hybrid prediction model, which significantly improved the accuracy of attitude prediction. Furthermore, a platform kinematic model was established using the closed-loop vector method. The predicted data were utilized to compensate the dual-layer Stewart platform, enabling coordinated control between the lower platform (simulating wave disturbances) and the upper platform (performing dynamic compensation). Experimental results demonstrate that the proposed approach achieves effective ship attitude compensation and provides a feasible solution for stable landing operations of unmanned aerial vehicles (UAVs) at sea.

Energy-saving ducts ahead of the propeller are widely applied to merchant ships as highly efficient energy-saving devices. Taking a certain bulk carrier as the research object, this paper adopts CFD technology to establish a numerical analysis method for the hydrodynamic loads of the energy-saving duct ahead of the propeller under ship steering conditions, and verifies the accuracy of the proposed method through convergence analysis and comparison with relevant experimental data. Based on this method, the influence laws of key factors including displacement volume, ship speed, rudder angle and rudder speed on the hydrodynamic loads of the energy-saving duct ahead of the propeller are investigated. The results show that the larger the ship's displacement volume, the greater the hydrodynamic loads acting on the energy-saving duct ahead of the propeller in all directions; the increases in ship speed and rudder angle both lead to an increase in the hydrodynamic loads on the duct in all directions; rudder speed has almost no effect on the hydrodynamic loads of the duct.

Real-time inversion of wave parameters in actual oceans using ship motion sensor data holds significant value for ship performance research. Compared to direct measurement methods, this indirect inversion approach offers advantages in real-time capability, cost efficiency, and ease of installation. Based on potential flow theory, this paper derives the wave-induced hull motion transfer function (response amplitude operator, RAO) using the principle of linear superposition. Combined with Kalman filtering (KF) technology, a time-frequency inversion model for wave parameters is proposed. The objective is to inversely determine the wave height time history and directional spectrum of random multi-directional waves based on the ship's multi-degree-of-freedom motion. Testing and validation were conducted using simulated multi-degree-of-freedom ship motion signals with noise as input. Results demonstrate that the KF model can effectively inverts directional spectra and wave height time histories for each principal wave direction and sea state level, with a maximum significant wave height inversion error of 10.08%. This indicates the KF model's potential for inverting wave directional spectra in real ocean environments.

The dynamic mechanical behavior of ice at high strain rates is crucial for polar engineering safety and ice–structure interaction studies. Based on an improved specimen preparation method and a Split Hopkinson Pressure Bar (SHPB) system, this study conducted high strain rate uniaxial compression tests on pure water ice at −20 ℃ in the range of 1054−1972 s⁻¹. The results show that pure water ice exhibits clear strain rate sensitivity: peak stress increases from 13.2 MPa to 25.1 MPa (≈ 90% increase), while peak strain shows no monotonic trend but remains scattered. Stress-strain curves generally display a sharp-peak profile, followed by rapid decay and the formation of a residual load-bearing platform of 1−7 MPa at strains around 0.05−0.06, with higher strain rates showing a "delayed instability" characterized by slower post-peak decay and higher residual strength. High-speed imaging further reveals a staged failure process of crack initiation, macro-cracking, and granular fragmentation, corresponding to the residual platform. Even under strict specimen screening and temperature control, peak stress still exhibits scatter of about 15%−20% at similar strain rates, suggesting that strain rate alone is insufficient to explain the mechanical response and that future constitutive models should introduce microstructural or statistical parameters. Cross-comparison with existing literature indicates that the present results fall within the established response range but demonstrate higher consistency and reliability due to stricter control of specimen thickness, temperature uniformity, and loading conditions. Overall, this study supplements the high strain rate database of pure water ice at −20 ℃, clarifies its strain rate sensitivity, residual load-bearing mechanism, and staged failure characteristics, and provides experimental evidence for dynamic response analysis and constitutive model development in cold-region engineering.

Compared with the rigid support scheme of traditional ship shafting systems, the bearing load in an elastically supported shafting system is more easily affected by external disturbances. To address the difficulty in accurately obtaining the bearing load under different operating conditions after the ship is launched, this paper proposes a method for predicting the bearing load of elastically supported shafting systems based on transfer learning. This method focuses on the influence of vertical disturbance forces caused by pressure changes in the air spring isolators on the shafting system. It collects strain data from characteristic regions and air spring pressure data during the installation and commissioning phase of the shafting system. These data, together with finite element simulation data, are used to build a bearing load prediction model with a GA-BP neural network algorithm. Validation with measured data shows that this method has good generalization ability and prediction accuracy for untrained operating conditions, with an average error of 8.8%.