Study on influence of complex geometry details on the aerodynamic performance of high-lift system

By numerical simulation, the influence of the main-wing root geometry details, wing-mounted engine nacelle, slat tracks and flap track fairings on the aerodynamic performance of a high-lift system is investigated. The results show that a separated low-power vortex is generated by the wing-root fairing which is left at the main-wing root when the slat is cut, and the aerodynamic performance of the lift system is damaged seriously by this vortex. Cutting most of the wing-root fairing as part of the slat can eliminate the condition needed to generate the separated low-power vortex. Remarkable decrease of the stall angle and maxim lift coefficient is caused by a large size wing-mounted engine nacelle. This is mainly because of the flow mechanism that a large space filled with low-speed fluid above the upper surface of the main wing is generated by the separated fluid which comes from the nacelle upper surface, pylon and the gaps between the pylon and slat. Strong vortices generated by the nacelle strake with proper shape and setting at proper positions can eliminate most of the low-speed fluid and recover part of the aerodynamic performance loss. Low-momentum wake flow generated by the slat tracks mixed with the boundary layer of the main wing causes the loss of the lift. Large fluid separation may be caused by the slat track at high angles of attack, which will result in a remarkable loss of the aerodynamic performance. The flap slot section area may be diminished as a result of the blockage effect of the large size geometry the of flap track fairings, which may cause the high speed flow of the flap slot to move faster, thus blowing away the separation flow on the flap surface.