Large Eddy Simulation of an Open Rotor Fan Blade

Abstract Open rotor fan blades, when exercised across a range of operating conditions and design options, present a variety of complex flow physics including leading-edge flow separation, wake evolution and interaction effects, and laminar-to-turbulent transition. In this paper, we present a large-eddy-simulation (LES) study of a three-dimensional open rotor fan blade at realistic conditions. Specifically, we focus in this paper on takeoff conditions, run at a Reynolds number representative of a subscale rig typically used for aeroacoustic technology maturation testing, to explore the flow behavior and its effects on takeoff aerodynamic performance and aeroacoustics that contribute to community noise. The simulations were performed using GENESIS, a high-order unstructured LES solver. The convergence of the solution is assessed by varying the polynomial order of the solution from low to high order. The analysis presented in the paper focuses on the evolution of the flow near the blade surface and the subsequent mixing downstream in the wake for a realistic blade design that exhibits the full three-dimensionality of these flow physics. A detailed understanding of these flow features is most useful for the aerodynamic and acoustic design of open rotor propulsors and the related implications of the LES results relative to conventional RANS-based CFD/CAA predictions is discussed.