EFFECT OF TOLERANCES OF SURFACE IRREGULARITIES ON LAMINAR-TURBULENT TRANSITION FOR HLFC WINGS

Abstract

Hybrid Laminar Flow Control (HLFC) is one of the most promising technologies for reducing the drag and therefore, the fuel consumption, of modern commercial aircraft. This technology is based on the potential of boundary-layer (BL) suction for delaying laminar-turbulent transition (LTT) and thus to reduce the viscous drag on aerodynamic devices, in particular swept wings. Suction is applied on the leading edge panel of the wing solely. However, the joint between the leading edge suction panel and the wing box may introduce relatively small surface irregularities, such as backward/forward-facing steps (BFS/FFS) or gaps. Such irregularities can promote the LTT by enhancing the spatial development of BL instabilities like Tollmien-Schlichting (TS) waves or crossflow (CF) vortices and therefore, may reduce the potential benefit of the suction system.