Predictive Low-Cost Large Eddy Simulation Capability for Fan and Open Rotor Noise

The modern trend towards ultra-high bypass ratio (UHBR) engines with larger fan diameters and a shorter nacelle, along with re-examination of 1960s highly fuel efficient technologies such as counter-rotating open rotors (CROR), has highlighted the need to mitigate turbomachinery-induced propulsion noise. Computational tools capable of predicting both tonal and broadband components of the generated noise with rapid turnaround times are critically needed. A wall-modeled Large Eddy Simulation method utilizing highly automated Cartesian octree grids with viscous immersed boundary description of geometries to study turbomachinery generated aeroacoustics is proposed. Phase-I of the research successfully demonstrate this capability for aeroacoustics in three different categories: a) quadrotor noise in forward flight, b) Counter-rotating open rotors in transonic cruise conditions, and c) a ducted fan at approach conditions using very modest single-node general purpose GPU resources with overnight turnaround times. Highly automated and rapid grid generation for very complex geometries as well as effective use of in-situ visualization and farfield acoustics post-processing was also highlighted. Phase II research is intended to build upon these findings in three key ways: a) Rigorous and expanded verification and validation across a large variety of operating conditions, b) substantial further improvements in time-to-solution via improvements in both the numerical algorithms and software infrastructure, and c) investigation of this capability to study propulsion-airframe integration problem with full aeroacoustic and aerodynamic analysis with overnight turnaround times. This technology will target both the existing propulsion and airframe markets, as well as the emerging eVTOL/air-taxi market.