To address the strong nonlinear aeroelastic bottleneck in the lightweight development of ultra-large wind turbines, as well as the insufficient simulation accuracy of the traditional blade element momentum (BEM) theory under large-angle separated flow conditions and the incomplete coverage of working conditions in existing fluid-structure interaction studies, this paper developed a high-precision and high-stability bidirectional CFD-CSD coupled simulation method. A coupling framework was established using a general-purpose CFD solver and the self-developed multi-body dynamics software GTSim. By integrating the improved delayed detached eddy simulation （IDDES） turbulence model, Timoshenko beam theory, and a progressive adaptive multi-level B-Spline dynamic mesh technique, the proposed method enabled refined aeroelastic response simulations of wind turbine blades across full operating conditions, including blade stacking, parked idling, and grid-connected power generation. The method was validated through multi-dimensional experiments and comparisons. Results show that the relative deviation of the aerodynamic force coefficients calculated by the proposed method from experimental measurements is less than 5%, and the calculated structural deflection deviates by less than 4.9% from that obtained using the industry-standard software Bladed. Under normal power generation conditions, the relative deviation of load predictions from measured data is within 10%. Moreover, the method accurately captures aeroelastic instability and coupled vibration characteristics under extreme conditions that cannot be predicted by traditional methods. This approach overcomes the inherent limitations of conventional methods and provides reliable technical support for the aeroelastic design and safety assessment of large wind turbines.

Shutdown and individual pitch for load reduction are important measures to ensure the structural safety of large wind turbines in extreme typhoon weather. When the blade trailing edge faces the wind (180° angle of attack), the aerodynamic coefficient of the airfoil is relatively small. This indicates that the trailing edge windward condition is favorable for load reduction. However, unfavorable vibrations exist in the flapwise direction under this condition. Based on wind tunnel experiments, this paper investigates the aeroelastic characteristics of three different typical wind turbine airfoils (DU00-W2-401, DU91-W2-250, and NACA64618) under the condition of the trailing edge windward load reduction. The study measures the flapwise displacement of the different airfoils at various wind speeds in the trailing edge windward condition. It is discovered that airfoils with different cross-sections of the blade exhibit flapwise vibrations at a specific flow angle of attack and reduced structural frequency. Specifically, the overall range of unstable angle of attack is from 155° to 167°. The instability region forms an inverted "V" shape, where the unstable angle of attack range increases as the reduced frequency decreases. This type of flapwise vibration exhibits frequency lock-in characteristics, meaning that the vibration frequency becomes locked to the first flapwise mode natural frequency of the structure. Additionally, the vibration amplitude increases as the structural reduced frequency decreases, and the maximum peak-to-peak vibration exceeds the chord length of the airfoils. For modern wind turbine blades with a pre-torsion design, it is advisable to minimize the occurrence of the main blade section entering the sensitive angles of flapwise instability during the trailing edge windward load reduction condition to prevent structural damage.

The next-generation passenger aircraft feature higher cruise speeds, rendering transonic buffet and Reynolds number effects pivotal in their aerodynamic design. This paper employs the high-precision delayed detached eddy simulation, based on the k-ω SST turbulence model, to investigate the aerodynamic characteristics of the CHN-T2 model for wide-body aircraft. Unsteady simulations demonstrate that, for a cruise Mach number of 0.85 and a Reynolds number of Re = 5×10⁷, the critical angle of attack at which the transonic buffet manifests is 4.4°. Large-scale separation around the wing root trailing edge serves as an indicator for the presence of the transonic buffet of CHN-T2, which exhibits the low-frequency (St = 0.0297) shock oscillation and high-frequency (St = 0.314) fluctuations in the high-pressure region near the trailing edge of the wing root. Regarding the Reynolds number effects, as the Reynolds number increases from Re = 5×10⁶ to 5×10⁷, the shock wave position on the CHN-T2 wing shifts aft by approximately 10% of the local chord length, and the boundary layer thickness decreases by 10% to 50%, resulting in considerable variation in the aerodynamic coefficients. It is further revealed that the Reynolds number effect on the lift and friction drag coefficients remains unchanged regardless of the angle of attack, whereas that on the pressure drag coefficient is linearly correlated with the angle of attack. Concurrently, the variation in the Reynolds number significantly affects the unsteady flow field of transonic buffet, with excessively low Reynolds numbers potentially leading to the disappearance of shock wave oscillations. An increase in the Reynolds number will significantly enhance the shock oscillation intensity but barely affect the high-frequency fluctuations at the wing root trailing edge.