In-Flight Boundary-Layer State Measurements on a High-Lift System: Main Element and Flap

Abstract

Flight experiments on NASA Langley Research Center's B737-100 airplane were conducted to document ow characteristics for further understanding of the ow physics on multielement high-lift systems. The measurements presented in this paper show that signi cant regions of laminar ow exist on the main element and the fore ap of the airplane. Flow mechanisms that affect the extent of laminar ow include relaminarization of the ow in the leading-edge region of the main element and contamination of the laminar ow on the ap by turbulent shear layers emanating from upstream elements. This information should be valuable in the development and assessment of high-Reynolds-number wind-tunnel experiments and numerical models for predicting the ows around multielement wings at full-scale high-lift conditions. Nomenclature C p = pressure coef cient, ( p 2 p`)/qC p,max = maximum pressure coef cient in leading-edge region of main element c = local chord length, ft c = mean aerodynamic chord, 11.20 ft h p = pressure altitude, ft K = relaminarization parameter M`= freestream Mach number p = local static pressure, psf p`= freestream static pressure, psf q`= freestream dynamic pressure, psf R bar = attachment-line Reynolds number Rc = Reynolds number, V`c/n s = surface distance, ft t = time, s V i = indicated airspeed, kn Presented as Paper 95-3911 at

The aerodynamic design of multi-element high-lift systems for transport airplanes

“…In two-dimensional airfoil flows, where surfaces are generally smooth and freestream turbulence levels are low, transition is governed by Tollmien-Schlichting (TS) instability, laminar separation, or turbulence contamination [105]. The latter mechanism is often overlooked, but can be important when, for instance, the flap boundary layer is contaminated by the wake of the main element and/or the slat [24]. The method is described in more detail by Brodeur and van Dam [103,104].…”

“…The experimental data presented and discussed in [23,24] show that extended regions of laminar flow occur on multi-element wings at high-lift conditions. On the B737-100, the entire slat (except for the cove) experienced laminar flow over a wide angle-of-attack range for all flap settings.…”

“…Flight experiments on NASA Langley's TSRV (B737-100) airplane were conducted to document flow characteristics for further understanding of high-lift flows [23][24][25][26][27]. The results of these flight experiments provide a good example of the complexity of the flow about threedimensional multi-element high-lift systems and the diversity of the transitional mechanisms.…”

“…Phase II involved surface pressure measurements and flow visualization across the full chord in the same region of the wing [25,26]. Phase III involved not only surface and skin-friction measurements but also boundary-layer profiles, boundary-layer states using hot films, and aeroelastic deformations using an optical system across the full chord near the mid-span station [27,23,24]. Fig.…”