This study employs an improved delayed detached eddy simulation method to examine the open-water performance and wake evolution of a propeller with notched blades, using an unstructured grid with 52.5 × 106 cells. The numerical method's validity was confirmed by comparing computed thrust and torque coefficients, as well as the flow field, with experimental data. The findings reveal that notched blades significantly reduce the propeller's hydrodynamic performance and accelerate wake instability. The notches introduce substantial disturbances in the surrounding flow, generating numerous small-scale vortices. These vortices interact with neighboring tip vortices, altering their topology and leading to rapid disintegration and the formation of secondary vortex structures. Increasing the number of notches further destabilizes the tip vortex system, causing tip vortices to lose coherence and become uniformly distributed in the mid-field. This study offers a detailed analysis of how notched blade configurations impact propeller performance, near-field flow characteristics, and wake evolution, providing valuable insights into the underlying mechanisms.

The problem of strong flow separation presents challenges in terms of both the accuracy and computational cost of numerical simulation methods. To address the issue where traditional wall-resolved large eddy simulation (WRLES) methods offer high accuracy but require fine-scale grids, and Reynolds-averaged Navier–Stokes methods are computationally efficient but struggle to capture transient turbulent structures, this study introduces a wall-modeled large eddy simulation (WMLES) method with multi-layer grid mapping. In this method, WRLES is employed in the bulk flow to solve the velocity and pressure fields, while a wall model is used to compute the wall shear stress near the wall. Based on appropriate grid partitioning strategies, numerical simulations of the high Reynolds number airflow field around the Simple Frigate Ship model are conducted. The comparison between WMLES, WRLES results, and experimental data indicates that the WMLES method effectively reduces the potential for random errors introduced by single-layer grid mapping and can successfully capture flow separation and boundary layer redevelopment phenomena. Moreover, it offers significantly lower computational cost compared to traditional WRLES methods, providing a practical method for numerical simulation of strong flow separation problems.

Algebraic wall models based on the stress-balance hypothesis and conventional EqODE (equilibrium ordinary differential equation model) models often lead to computational distortions when handling complex flow separation at high Reynolds numbers due to the neglect of non-equilibrium effects. To address this issue, a wall model that simultaneously considers the effects of convection terms and pressure gradients while avoiding the calculation of wall-parallel derivatives is developed by modeling the convective terms. Numerical simulations are performed on the periodic hill and the generic ship simplified frigate ship (SFS2) models using this model, EqODE, algebraic wall models, and WRLES (wall-resolved large-eddy simulation). Detailed comparisons between simulation results and experimental data indicate that traditional equilibrium models fail to effectively predict near-wall shear stress within the range of y+ between 10 and 50, resulting in the smoothing of skin friction distributions in the separation and reattachment regions. Furthermore, in cross-sectional flow separation, traditional equilibrium models cannot resolve the bistable structures of three-dimensional backward-facing step flows. In contrast, the Non-EqODE model accurately captures wall shear stress, pressure, Reynolds stress, and velocity distributions even under conditions of higher y+ and lower grid resolution, and successfully captures the turbulent asymmetric bistable characteristics in the wake field. This method significantly reduces computational costs while ensuring the numerical conservation of the equations, providing a new approach for the efficient simulation of complex flow fields at high Reynolds numbers.

Floating offshore platforms are subjected to significant impact loads from ocean currents, which pose considerable challenges to the safety of floating offshore wind turbines. To address this issue, this study develops a novel infill criterion framework based on the parallel Efficient Global Optimization (EGO) algorithm. Compared with the traditional EGO algorithm, the proposed framework enables the simultaneous addition of multiple infill samples in each iteration, resulting in substantially improved optimization efficiency. The proposed method is applied to the optimization of floating offshore platforms, where drag minimization is considered the primary design objective. The results demonstrate that incorporating the mean squared error (MSE) criterion into the conventional EGO algorithm, while constraining the search space of the MSE criterion, effectively accelerates the convergence of the Expected Improvement (EI) criterion. Furthermore, an optimization method for floating platforms is established, leading to a reduction in drag of approximately 1.69% after optimization. The proposed optimization framework improves the drag performance of floating offshore platforms and provides a new approach for structural optimization in offshore engineering.