Transonic Flutter Characteristics of an Arrow Wing Mounted with Engine

Abstract

Transonic flutter wind tunnel tests with a flexible scaled model of the Jet-powered Supersonic Experimental Airplane were conducted at Japan Aerospace Exploration Agency (JAXA). The test results would be used for establishing and verifying analysis tools to evaluate transonic aeroelasticity. The test article was designed as 11% scaled model of the experimental airplane which length and width are 11.5m and 4.93m respectively. The wind tunnel was operated by sweeping either total pressure or by sweeping Mach number, or both proportionally. Typical dip shape boundary of transonic flutter was obtained and limit cycle oscillation was also revealed below the flutter boundary. In this paper, the summary of the flutter tests is reported. I. Introduction eroelastic flutter evaluation plays a significant role in the structural design of aircraft since flutter phenomenon can cause serious damage or loss of aircraft. Structural requirements for less weight and less cost make the role more important on high-speed aircraft, especially a supersonic transport (SST) due to the complexities in aerodynamic and structural aspects in transonic region. Transonic Flows are characterized by the presence of adjacent regions of subsonic and supersonic flow, usually accompanied by shock waves. Nonlinear behavior of the shock waves causes unexpected unstable vibrations such as transonic flutter (transonic-dip) and limit cycle oscillation (LCO) which are inconvenient for performance of high speed aircraft. In the past, there have been many activities, not only numerically but also experimentally, in investigation of this kind of nonlinear aeroelasticity. Since 1997, the National Aerospace Laboratory (NAL), presently the Japan Aerospace Exploration Agency (JAXA), has been conducting the National Experimental Supersonic Transport (NEXST) program to prepare the nation's technical base for coming international development of the next generation SST (Ref. 1). Major objectives of the NEXST program are as follows; a) to develop system integration technology for aircraft b) to establish CFD-based aerodynamic design technology with inverse and optimization method c) to progress component technologies in aerodynamic and composite structures design In order to demonstrate these technologies, the developments of two types of scaled supersonic experimental aircraft are promoted; one is non-powered experimental airplane and the other is jet-powered one. The non-powered airplane (NEXST-1) was developed to demonstrate the inverse aerodynamic design technology to realize a low drag configuration. The cranked arrow wing, area rule and warp concept are integrated with the natural laminar wing technology. During the development of the NEXST-1, the aeroelastic characteristics of a clean arrow wing are investigated elaborately (Ref.2). Following the NEXST-1, aeroelastic investigation of the jet-powered experimental airplane (NEXST-2) was conducted in the basic design phase. The NEXST-2 has a role to demonstrate the optimized-inverse design system and some component technologies including engine-airframe integration, high performance stable air-intake and composite structure for the wing. The NEXST-2 is characterized as unique