Experimental investigation of the confluent boundary layer of a multielement low speed airfoil

Introduction Measurements of the confluent boundary layer on the upper surface of a two-dimensional high-lift airfoil model, consisting of a wing section with a slotted leading edge flap and a double-slotted trailing edge flap in a take-off setting, are described. The experimental investigation was conducted in the Boeing Research Wind Tunnel in Seattle a t low speed (M, = 0.11) and a chord Reynolds number of 1.55 x los. The confluent boundary layer resulted from the merging of the turbulent wing boundary layer with the turbulent wake of the leading edge flap and remained completely attached to the wing surface. The measured data, which include surface static pressures, streamwise velocity profiles, three components of Reynolds normal stress, and Reynolds shear stress, represent a complete test case for computational methods. The boundary layer measuring system consisted of a mechanical traverse with a Pitot probe and two X-hot wires. This paper contains a thorough discussion of the data quality, including comparisons with theoretical predictions using the k, +model of turbulence.