Scale-Resolving Simulations of a Civil Aircraft Wing Transonic Shock-Buffet Experiment

Abstract

The flow physics governing the shock-buffet phenomenon on swept wings remain disputed without an unequivocal description. Herein is a contribution to the ongoing discussion that addresses the inherent dynamics near the onset of unsteadiness, complementing experimental data of a large aircraft wing geometry with scale-resolving simulation. Specifically, delayed detached-eddy simulations are performed to reproduce the experiments with a Reynolds number of and a Mach number of 0.801, and they are analyzed using modal methods. Motivated by the recognized difficulty in simulating separating and reattaching shallow shear layers employing such techniques, the impact of two subgrid length-scale definitions are scrutinized. The simulations, using both the standard definition of maximum local spacing and a more recent vorticity-sensitive variant, are validated against experimental data from conventional steady and unsteady instrumentation and dynamic pressure-sensitive paint. Remarkable agreement is found between experiment and simulation when using the vorticity-sensitive definition, whereby dominant modal features extracted from surface pressures show striking similarity in describing localized pockets of shear-layer pulsation synchronized with an outboard-propagating shock oscillation. Identified modes from simulation cover broadband content centered at a Strouhal number of approximately 0.27, which is within the experimental frequency range characteristic for swept-wing shock buffet. Modes capturing an inboard-running lower-frequency shock unsteadiness centered at a Strouhal number of approximately 0.07 are exclusive to wind-tunnel conditions. Nevertheless, modal analysis succeeds in extracting key characteristics from such practical unsteady-flow datasets. It is anticipated that the current findings with help clarify these edge-of-the-envelope flow phenomena and ultimately inform shock-buffet delay and control strategies.