Experiments on Active Drag Reduction on a Complex Outer Wing Model

The potential of active flow control by means of pulsed blowing to counter performance degradation at high angles of attack is demonstrated on a modern civil aircraft outer wing configuration provided by the European aeronautical industry. Flow control actuators are incorporated into the leading edge between the slat edge and the wingtip, where the wing’s slender shape and its high local curvature do not allow for the integration of mechanical leading-edge devices. Surface flow visualization identifies the highly three-dimensional topology of the uncontrolled flow, which is dominated by the slat edge vortex and leading-edge flow separation at high incidence angles. The influence of the varying-momentum coefficient on drag reduction, lift gain, and aerodynamic efficiency is studied, considering force and pressure measurements, as well as flow visualization. Results indicate that a momentum coefficient of cμ=0.6% suffices to reduce drag by up to 38%, compared to the uncontrolled baseline flow, and to offset aerodynamic performance degradation by 4 deg if the actuation effort is distributed efficiently along the span.