On the Wake/Tailplane Interaction in Established Transonic Shock Buffet Mode

AIAA SciTech Forum

Abstract

Under particular combinations of upstream flow conditions the transonic flight regime is associated with a highly unsteady and complex shock-wave/boundary-layer interaction involving major parts of the flow field. The phenomenon typically referred to as transonic buffet is associated with a large-amplitude periodic motion of the compression shock coupled with large-scale flow separation and intermittent reattachment. Due to the resulting variation of the global flow topology, also the turbulent wake of the airfoil is severely affected, thus conveying its influence on the flow impinging on the tailplane further downstream. An experimental study is conducted capturing the fully developed buffet phenomenon at the main wing, the establishing turbulent wake properties, as well as the interaction of the impinging wake with the tailplane. To analyze and understand this complex turbulent interaction, a tandem wing configuration is explored, consisting of the supercritical OAT15A airfoil (main wing) and the NACA 64A-110 (tailplane) at chord Reynolds numbers of 2 million and 1 million, respectively. High-speed focusing schlieren imaging is employed to characterize the temporal and spectral nature of the developing periodic wake as induced by the global buffet mode. Established buffet conditions are shown to replicate those of an individual airfoil case. Modulated by the a perdiodic shock oscillation at a frequency of 103 Hz the flow is intermittently strongly separated, with a varying momentum deficit that extends far downstream. Velocity field measurements reveal severe global influences of the global buffet mode accompanied by the shedding of vortical structures that continue to persist at constant strength far into the wake. Depending on the phase within the buffet cycle, a recurring alteration of the downstream angle is observed affecting the interaction with both suction and pressure sides of the tailplane. Surface pressure fluctuations measured along either side of the tailplane are evaluated to extract characteristic spectral footprint. Analyses of the power spectral density reveal an exact match with the main buffet frequency of 103 Hz, thus confirming the suspected interaction and exerted impact on the tailplane aerodynamics.

Authors 2

1. Christopher J. Schauerte Aachen

   RWTH Aachen University

   Affiliation as printed

   RWTH Aachen University

2. Anne-Marie Schreyer Aachen

   RWTH Aachen University

   Affiliation as printed

   RWTH Aachen University