High Angle-of-Attack Aerodynamics

High angle-of-attack (high-IX) aerodynamics has been a key element in airplane design beginning with the first attempts at unpowered manned flight using gliders in the 1 800s and extending to the present day with civil and military airplanes. High-IX aerodynamics is commonly perceived as arising on an airplane at a physically large angle of attack with its leading­ edge vortex separating from highly swept wings. However, the underlying flow is that of a heavily loaded lifting surface, operating at other than optimum lift-to-drag ratio. This off-design or high-lift condition often includes regions of separated flow. In this regard, high-IX embraces a broader range of aerodynamic flows than is widely appreciated. For example, high-IX can be defined as any situation where an airplane or any of its components encounters off-design, high-lift flight, and includes attached flows, uncontrolled separated flows, and organized flow sep­ aration in the form of vortices, shock waves, and combinations of these flow conditions. The high-IX regime encompasses local and global flow fields that can occur at subsonic through hypersonic speeds. These flow fields can be highly interactive and either static or dynamic in nature. Examples of localized high-IX flows include the interaction of the propeller tip vortex system with the airframe of a light general aviation airplane;