Transonic buffet is a critical issue for high-subsonic and supersonic aircraft, severely limiting their performance and flight safety. This paper reviews the recent research progress in this field, covering numerical simulation methods, buffet mechanisms, wind tunnel testing, buffet control, and engineering applications. The key technologies in each aspect are summarized, and important considerations for transonic buffet research in the context of aircraft design requirements are identified. First, numerical methods for transonic buffet simulation are briefly introduced, and the similarities and differences in the mechanisms and analysis approaches between rigid and elastic wings are compared. Second, advances in wind tunnel testing of transonic buffet are summarized in detail, including buffet boundary criteria and measurement techniques. Finally, key technologies for transonic buffet control and representative engineering cases are reviewed. On this basis, several directions worthy of future in-depth investigation are discussed, including fluid-structure coupled buffet computation and mechanism analysis for civil aircraft with ultra-high aspect ratio configurations, high-precision multi-physics visual buffet test and measurement methods, multidisciplinary layout design considering buffet constraints, engineering application of novel control methods, and deep integration of intelligent methods in buffet analysis and control. This paper aims to provide a reference for further research and engineering application of transonic buffet control technologies for various aircraft.

The drag rudder serves as an unconventional control surface specifically designed for flying wing aircraft. Positioned near the wingtips, the drag rudder splits to generate drag force and yawing moments, which exhibits significant nonlinear characteristics. This paper introduces a flutter analysis method for drag rudder equipped wing model, which is based on high-precision unsteady aerodynamic force corrections at the flutter frequency domain. Subsequently, a low-speed wind tunnel test for the drag-rudder wing flutter is conducted. The study reveals the flutter patterns of the drag-rudder wing under various split angles by comparing the simulation and wind tunnel test results. Both sets of results indicate that an increase in the split angle leads to a higher flutter speed of the drag-rudder wing. Specificially, a unilateral 20° split angle results in an approximately 8.5% increase in flutter speed compared to the non-split state.

The geometric nonlinearity and aerodynamic nonlinearity cannot be ignored as the large flexible wing undergoes significant deformation when subjected to high gusts. In order to study the response of a large flexible wing under strong gusts, a fluid-structure interaction analysis method based on geometric nonlinear beam theory and computational fluid dynamics (CFD) was established. The fluid model and geometrically nonlinear beam model of a big flexible wing with a semi-aspect ratio of 9 were constructed, and the accuracy of the fluid-structure interaction simulation approach was confirmed by comparing wind tunnel tests of inverted flexible plate. The dynamic response characteristics of large flexible airfoils were examined at various gust ratios (R_G=0.1-0.4). In particular, the dynamic stall aerodynamic characteristics of the airfoils caused by gusts at large gust ratios (R_G=0.4) were examined. The gust response analysis was conducted at a Reynolds number of 10⁵. The results show that significant nonlinear bending deformation of the wing occurs with the increase of gust ratios, and the maximum bending deformation of the wing reaches 63% of the half-spread length at R_G=0.4. Meanwhile, the bending deformation of the wing reduces the width of the spreading distribution of the leading-edge vortex (LEV), which affects the distribution of aerodynamic forces and reduces the gust loads.

This paper focuses on the effect of the phase offset of Leading-Edge (LE) morphing on the aerodynamic characteristics of a pitching NACA0012 airfoil. Assuming an unstretched camber and using polynomial interpolation, an explicit expression for LE nonlinear morphing is proposed and implemented for the large pitching motion of the airfoil. Flow field results and aerodynamic forces are obtained by solving the unsteady Reynolds-averaged Navier-Stokes equations for both the airfoil’s pitching motion and LE morphing. Furthermore, the index of instantaneous aerodynamic power is used to quantify the work done by the airflow in a dynamic process. According to the instantaneous aerodynamic power and energy map, which denotes the energy transfer between the airfoil’s oscillation and flow field, the airfoil is subject to stall flutter. The results show that LE morphing with an optimal phase offset of 315° reduces the energy extraction from the flow field, suppressing the stall flutter instability. This optimal phase offset is effective at different pitching axis positions of the airfoil. The results signify that LE morphing can suppress stall flutter by advancing the occurrence of the first LE vortex and increasing the nose-down moment during the upstroke period.

The seamless and smooth aerodynamic shape of the flexible morphing trailing edge not only offers significant improvements over traditional hinged rudders in aerodynamic performance, but also has the potential to enhance noise reduction capabilities. Using the large eddy simulation model and the acoustic analogy method based on the FW-H equation, the aeroacoustic characteristics of the stitched and seamless trailing edges are investigated through CFD numerical simulation. Furthermore, the study explores the aeroacoustic characteristics of the aircraft when it encounters gusts, with a particular focus on the flexible morphing of the seamless trailing edge. The load alleviation efficiency and aeroacoustic characteristics of the flexible morphing of seamless trailing edge are compared with those of rigid deflection of the seamless trailing edge. The results show that at 4° angle of attack, the tonal noise peak of seamless trailing edge decreases by 20.2 dB compared with that of slotted trailing edge With the sine wind gust of 4°-20° equivalent angle of attack, the load alleviation efficiency of flexible morphing trailing edge is more than 60%, which is 10%-30% higher than that in the rigid deflection. In addition, the tonal noise peak value of flexible morphing trailing edge can be reduced by 7.2 dB compared with that of the rigid deflection at 12° equivalent angle sine gust. Finally, the effects of the two deflection modes of the seamless trailing edge on wind load alleviation efficiency and aeroacoustic characteristics are analyzed from the perspective of dynamic characteristics and flow evolution.