IMPLEMENTATION OF ACTIVE FLOW CONTROL ON A SHORT-INLET UHBR ENGINE NACELLE

Innovative nacelle designs and disruptive technologies are required to minimize drag and weight penalties of high bypass ratio turbofan engines. Active flow control can improve flow quality at the fan-face while significantly reducing structural weight and aerodynamic drag through more aggressive, i.e., shorter inlet geometries. Within the scope of the Lufo VI-2 project AKTIVER, the implementation of active flow control (AFC) on a shortinlet ultra-high bypass ratio (UHBR) engine nacelle is being investigated experimentally and numerically. This paper introduces the generic axisymmetric model, reffered to as SIA (Short-Inlet Active Flow Control)-Nacelle, followed by numerical results of a design concept analysis of the AFC system. Unsteady Reynolds-averaged Navier-Stokes simulations and scale-adaptive simulations are conducted. Analysis of the clean reference case without AFC indicate that large-scale inlet separation starts at an angle of attack of 26◦. Here, the primary use case for AFC is at an angle of attack of α = 29◦ and a free-stream Mach number of Ma = 0.15, which is representative of a take-off roll for strong crosswinds or the wing C_L,max condition. The AFC system is tested in continuous and pulsed blowing mode. For the present case, the continuous blowing mode is found to be more effective since pairs of counter-rotating vortices formed by the round jets tend to be more stable. In evaluating the AFC system, significant improvements in inlet performance data are observed compared to the clean configuration. The total pressure coefficient ησ improves by up to 7.1%, the distortion coefficient DC₆₀ by 53.0%, and the swirl coefficient SC₆₀ by 29.4%.