Numerical analysis of buffet flow for civil aircraft at low speed and high angle of attack

Abstract:

To investigate the horizontal tail buffet flow characteristics and mechanisms for civil aircraft at low speeds and high angles of attack (AOA), this study conducted high-precision flow simulations for a typical civil aircraft configuration under flow separation conditions based on the stress-blended eddy simulation (SBES) method. Firstly, the accuracy of the numerical simulation in resolving separated flow is validated using a NACA 0015 airfoil at high AOAs. Then, numerical simulations were performed for a clean configuration of a civil aircraft and compared with wind tunnel test data. The comparative analysis shows that the numerically predicted mean and fluctuating pressure coefficients on the horizontal tail agree well with the wind tunnel test data under various flow conditions and exhibit consistent variation trends with AOA, thus verifying the methods suitability for simulating the horizontal tail flow field under the interference of wing separation flow. Finally, based on the comparison between the simulation results and experimental data, the mechanism and evolution of aerodynamic interference on the horizontal tail caused by wing separation flow are analyzed in depth. Analysis results reveal that near the buffet boundary, local wing flow separation induces only minor buffet loads on the horizontal tail. As AOA increases, strong wing wake separation vortices gradually dominate the flow field of the horizontal tail, significantly amplifying the buffet loads of the horizontal tail. As the AOA increases further, the horizontal tail gradually moves out of the wing wake region, causing the growth of the buffet load amplitude to slow down. Consequently, the flow field becomes dominated by the horizontal tails own high-AOA separation flow, accompanied by a shift of the dominant flow frequency toward higher frequencies. The study clarifies the evolution of buffet load characteristics of the horizontal tail under the influence of wing separation flow at high AOA, offering guidance for safety assessment and design of civil aircraft.