AIAA-2001-0912 Reynolds Number Effects on a Supersonic Transport at Transonic Conditions (Invited)

A High Speed Civil Transport configuration was tested in the National Transonic Facility at the NASA Langley Research Center as part of NASA’s High Speed Research Program. The primary purposes of the tests were to assess Reynolds number scale effects and the high Reynolds number aerodynamic characteristics of a realistic, second generation supersonic transport while providing data for the assessment of computational methods. The tests included longitudinal and lateral/directional studies at lowspeed high-lift and transonic conditions across a range of Reynolds numbers from that available in conventional wind tunnels to near flight conditions. Results are presented which focus on both the Reynolds number and static aeroelastic sensitivities of longitudinal characteristics at Mach 0.90 for a configuration without an empennage. INTRODUCTION Ground to flight scaling remains one of many challenges facing today’s designers of aerospace vehicles. The goal of ground to flight scaling is the preflight prediction of multiple key aerodynamic characteristics with sufficient accuracy to meet both performance guarantees and certification requirements. In other words, the designer and his company strive to know the performance of their vehicle with high confidence prior to flight, thus enabling optimal design trades prior to flight and the elimination of costly fixes to the aircraft after the first flight. Specific challenges, experiences, and suggested approaches to ground to flight scaling have been documented extensively over the years for a variety of vehicle classes (refs. 1, 2, among many others). Reynolds number effects are foremost among many factors affecting successful ground to flight scaling (refs. 3 5). The Reynolds number is the ratio of inertial to viscous forces, and is the primary aerodynamic scaling parameter used to relate sub-scale wind tunnel models to full-scale aircraft in flight. The challenge of Reynolds number scaling increases with the size of a full-scale aircraft as the Reynolds number increment between that obtainable in conventional wind tunnels and flight conditions expands. Additionally, the challenge for both wind tunnel and computational approaches increases as flow features become dominated by viscoussensitive phenomena such as boundary-layer transition, shock/boundary layer interaction, and separation onset and progression. The present investigation was conducted in support of NASA’s High Speed Research (HSR) Program, Phase II, which was conducted from 1993-1999 (ref. 6). The objective of this program, which was NASA sponsored and jointly executed with US industry, was to develop critical high-risk airframe and propulsion technologies to enable industry development of an economically viable and environmentally acceptable second generation high speed civil transport (HSCT). Aerodynamic performance, one of several broad airframe technology areas, included tasks to address Configuration Aerodynamics for highspeed conditions and High-Lift Technology for take-off and landing. These elements encompassed not only the challenge of efficient supersonic cruise flight, but also the off-design challenges (ref. 7) of efficient transonic cruise and acceleration, and quiet high-performance take-off and landing. The objective of the Configuration Aerodynamics task was the development of aerodynamic drag reduction, stability and control, and propulsion airframe integration technologies required to support the HSCT development * Assistant Head, Configuration Aerodynamics Branch, Associate Fellow, AIAA † Aerospace Engineer, Subsonic Aerodynamics Branch, Senior Member, AIAA ‡ Aerospace Engineer, Configuration Aerodynamics Branch, Member, AIAA Copyright © 2001 by the American Institute of Aeronautics and Astronautics, Inc. No copyright is asserted in the United States under Title 17, U. S. Code. The U. S. Government has a royaltyfree license to exercise all rights under the copyright claimed herein for Governmental Purposes. All other rights are reserved by the copyright owner.