High lift research program for a fighter-type, multi-element airfoil at high Reynolds numbers

Abstract

This paper describes an experimental research program being conducted to help understand and predict the high-lift airflow characteristics about thin, fighter-type, multi-element airfoils at flight Reynolds numbers and lift coefficients up to lmax' Tne wind nl tests supporting this program are being conducted in the NASA Langley Research Center (LaRC) Low Turbulence Pressure Tunnel (LTPT) as part of a cooperative effort between McDonnell Douglas Aerospace (MDA) and NASA LaRC. The test article is a twodimensional (2-D) airfoil model of an MDA advanced fighter wing section configured with a plain leading edge flap and a single slotted trailing edge flap. Test data obtained include surface static pressures integrated to provide lift and pitching moment, external balance forces and moments, and off-body flowfield surveys at several model longitudinal locations. Reynolds number and trailing edge flap gap and overhang arrangements were investigated to assess the effects on the section high-lift performance. * Principal Engineer, Aerodynamics, New Aircraft and Missile Products t Group Manager, Experimental Fluid Dynamics $ Group Manager, New Aircraft and Missile Products § Senior Test Engineer, Low Turbulence Pressure Tunnel Copyright © 1995 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved. C C, lmax Cp M O.H. RN x/c y/c a Sf Nomenclature Clean Airfoil Chord Lift Coefficient Maximum Lift Coefficient Pressure Coefficient Mach Number Overhang (% Chord) Reynolds Number Nondimensional Chord (%) Nondimensional Span (%) Angle of Attack (Deg.) Trailing Edge Flap Deflection Angle (Deg.) Leading Edge Flap Deflection Angle (Deg.) Shroud Deflection Angle (Deg.) Introduction Fast, reliable, and inexpensive high-lift design techniques for the conceptual development phases of advanced fighter programs are sorely needed and long overdue. The schematic in Figure 1 illustrates why the airflow characteristics about thin, fighter-type wings are so complex and difficult to predict. Accurate modeling of this complex flowfield, including trailing viscous wakes that impact aft elements, confluent boundary layers, separated flows, and different transition regions, is essential for predicting the performance of high-lift configurations. Responding to the challenges offered by this particular need, MDA initiated an Independent Research and 1 American Institute of Aeronautics and Astronautics Development (IRAD) program, the objectives of which are to derive semi-empirical, high-lift design techniques and to promote a better understanding of the flow phenomena about fighter-type high-lift systems. The one overriding requirement for success that permeates the entire experimental or CFD-based process is the need to understand the physics involved in every flow situation being addressed. The understanding of the pertinent flow physics can only be attained through flowdiagnostic testing that involves surface flow measurement and visualization capabilities, offbody flowfield measurements, and boundary layer transition measurements. Experimental Apparatus