Highly Integrated Subsonic Air Intakes

Abstract

Aerodynamic integration of air intakes with increasingly compact shaping and the optimization of their performance are challenging tasks for innovative design of advanced unmanned aerial vehicles (UAVs) featuring superior combat or reconnaissance abilities. In order to meet configurational requirements, diverterless intake designs with optimized entry shaping and sophisticated serpentine duct layout are primary goals in the overall development process. These design challenges, however, can generate intake flow characteristics, which can adversely impact the aerodynamic performance of the intake and the engine/intake compatibility. Unsteady flow physics like separation and reattachment as well as pre-entry and internal flow control imply an advanced degree of detailed understanding of the highly three-dimensional flow during the early design process. Installed thrust, range, and weight as additional key factors strongly relate to all these design requirements. Competitive aspects demand reduced development costs and short delivery times and thus are also main drivers within the UAV design process. Current diffuser flow management and control systems are largely empirically derived. Enhanced understanding of the flow physics involved in complex innovative intake design can lead to improved active and passive methodologies for controlling these internal flows. In order to reduce costly wind tunnel experiments during the development phase of aerial vehicles the ability to accurately predict the aerodynamic performance of highly integrated intakes is of great importance. The most promising simulation methods for time-accurate flow phenomena with high turbulence levels in an industrial environment are hybrid methods combining the inexpensive RANS (Reynolds- Averaged Navier-Stokes) and the accurate LES (Large Eddy Simulation) techniques.