Detailed measurements of a flap side-edge flow field

Abstract

Detailed flow measurements were performed with a five-hole probe in the flap side-edge region of a wing with a half-span flap. The experiments were conducted in the NASA-Langley Quiet Flow Facility as a part of an extensive experimental and computational investigation of airframe-related noise sources. Basic flow properties were verified using static pressure taps, pressure-sensitive paint, and oil-flow visualization. Detailed five-hole probe surveys were conducted in a set of planes at ten streamwise stations for flap deflections of 29 and 39 degrees. These measurements show the development of a two-vortex system at the flap side edge. The vortex path and strength are determined, and the process of vortex merging is documented in detail in the mid-chord region. At the higher flap deflection angle, vortex bursting is observed, which may be a factor in the observed higher noise levels for this condition. Results are compared with Reynolds-averaged NavierStokes calculations of a similar configuration (AIAA Paper 98-0768). These measurements and calculations form the basis for instability modeling and unsteady calculations which will ultimately lead to an understanding of flap side-edge noise sources.