Wind Tunnel, Simulation, and “Real” Flight of Advanced Combat Aircraft: Industrial Perspective

Abstract

An industrial view on experimental and numerical investigations related to advanced combat aircraft needs is given. A critical comparison between experimental and numerical results under wind-tunnel conditions and real flight numerical simulations is presented. The Reynolds and Mach number influence on the aerodynamic behavior together with the development of the complex flowfields around generic unmanned combat aircraft configurations at transonic speed and medium and high angle-of-attack conditions is discussed. Static computational-fluid-dynamics results of forces and moments as well as the flow structure of the longitudinal and lateral flow conditions are compared to wind-tunnel measurements. Here, combat aircraft and flying-wing-type unmanned combat aircraft flow phenomena such as separation emerging at round and sharp leading edges into interacting vortex flows are shown. Also their possible development at transonic conditions causing interacting shock systems is addressed. Although wind-tunnel (low) Reynolds number, subsonic conditions are thought economic, they may be far off flight (high) Reynolds number and realistic subsonic and transonic Mach number speeds. Therefore, free-flight, full-scale conditions have also been prepared to probe the possible differences with the experimental and numerical investigations of the design and early development process of future shapes. This will show the sensitivity and possible basic uncertainty of the stability and control investigations of modern combat aircraft due to insufficient full-scale, free-flight knowledge.