Numerical Study on the Ability of Shock Control Bumps for Buffet Control

Abstract

In addition to efficient reduction of wave drag in transonic flight, shock control bumps also offer some potential for buffet alleviation. In the present paper, two different approaches for buffet control by shock control bumps are compared and assessed based on time-resolved (unsteady) Reynolds-averaged Navier–Stokes simulations: downstream positioning of two-dimensional bumps, necessitating an adaptive device for combining both features (wave drag reduction and buffet control), and vortex generation by three-dimensional bumps as “smart vortex generators”. With the intention of providing detailed insight into dominant flow features and linking geometrical bump characteristics to those flow structures, the effect of bump design condition, crest height, and streamwise positioning of two- and three-dimensional shock control bumps on buffet behavior and performance of a supercritical, unswept wing section has been analyzed. Two-dimensional shock control bumps improve buffet behavior by an efficient shock strength reduction in combination with positive effects on flow separation. For three-dimensional bumps, the same buffet-affecting mechanisms have been observed, only less dominant due to the finite spanwise extent. Furthermore, it has been demonstrated that the strength of three-dimensional bumps’ vortical wake can be tuned by appropriate bump shaping and that this strength positively correlates with delayed buffet onset.