Synopsis of the Project EUROSHOCK II

Abstract

The development of the boundary layer and the interaction of the boundary layer with the wing-upper-surface shock wave play an essential role in determining the design and off-design performance of transonic transport aircraft in the case of a turbulent wing but more so for laminar wings where moderate to strong shock waves may already be present at cruise conditions in order to take full advantage of the potential of laminarization. Based on the experience gained during the EUROSHOCK I project, where it was found that passive shock control by a perforated surface/cavity arrangement always lead, for laminar wings, to an increase in total drag, active control by contour bumps, discrete slot suction, a perforated surface / cavity arrangement with part-suction, and by hybrid control, i.e., a combination of control schemes, was investigated. The study consisted of four elements: basic experiments with the objective of improving the physical models associated with control, the extension of numerical prediction methods to properly treat shock and boundary layer control and the performance of parametric control effectiveness studies, the performance of airfoil and sheared-wing tests to provide data for the validation of the computational methods and to determine — in conjunction with the computational results — the aerodynamic merits of active shock and boundary layer control, and the assessment of benefits and penalties associated with incorporating potential control methods into existing and/or new wing designs. The results have shown that active shock control by a perforated surface / cavity arrangement with part-suction and similarly hybrid control, consisting of a passive cavity arrangement upstream followed by active suction downstream, always lead to an increase in total drag for the airfoils and the sheared wing considered here, while discrete suction resulted in a noticeable decrease in drag, even when accounting for “pump” drag. The most effective device, however, was found to be an adaptive contour bump placed in the shock region which lead to drag reductions of up to 23%. A further reduction in drag was achieved when combining the contour bump with discrete suction upstream of the bump. The implementation studies have shown, accordingly, that by incorporating an adaptive, variable-height bump into a laminar-wing aircraft, fuel reductions of up to 2.11% can be achieved on typical long-range flight missions. All devices investigated had a positive effect on the buffet boundary.