Study on wake–tailplane interactions in transonic buffeting separated flow: Horizontal tail in pre-buffet states

Abstract

In transonic flight, the fluctuating loads imposed on the horizontal tail by wing shock-induced flow separation are critical factors affecting both flight safety and structural integrity. In this study, a delayed detached-eddy simulation approach based on the Spalart–Allmaras (S–A) turbulence model is employed to systematically investigate the evolution of the turbulent wake generated by the main wing and its unsteady interaction with the horizontal tail. The analysis focuses on the shock buffet flow over an OAT15A airfoil at a 5.0° angle of attack under transonic conditions. The accuracy of the numerical method in simulating the shock motion range, buffet frequency, and turbulent kinetic energy dissipation in the wake is validated. The results show that during the forward motion of the main wing shock toward the leading edge within one buffet cycle, a large-scale separation bubble is generated and shed, forming highly fluctuating alternating vortex structures accompanied by high-frequency pulsations of the shear layer at the shock foot. Turbulent kinetic energy analysis reveals that although the separated wake dissipates rapidly during downstream transport, it still retains about 30% of its peak energy intensity in the region where the horizontal tail is located. Using sliding-window proper orthogonal decomposition and flow field reconstruction, it is found that the large-scale separated vortices from the main wing undergo vortex breakup when interacting with the horizontal tail, with energy transferring to small-scale separation vortices on the tail surface and upstream-traveling wave modes. The aerodynamic forces on the horizontal tail exhibit unsteady fluctuations associated with the fundamental frequency of the main wing shock oscillation and its harmonics, and show distinct spectral response characteristics at different tail angles of attack. This study reveals the complex energy transfer mechanism of shock–vortex–tail coupling in the separated buffet flow, providing a flow-physics basis for the dynamic load analysis of horizontal tails on transonic aircraft.