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.

NASA experiments such as the Source Diagnostic Test (SDT) conducted in early 2000s and the more recent Counter Rotating Open Rotor (CROR) testing have been instrumental in validating new Computational Fluid Dynamics (CFD) technologies including Volcano ScaLES. Consequently, we welcome utilization of Volcano ScaLES within NASA in design and analysis of novel ideas. With specific emphasis on enabling LES usage by non-CFD experts, we anticipate ScaLES usage by many experimentalists and designed within NASA in support of their existing research. Furthermore, many design concepts currently under active development under the Advanced Air Transport Technology (AATT) program such as the Transonic Truss Braced Wing (TTBW) could utilize ScaLES for studying the important propulsion airframe integration (PAI) challenges which require combined analysis of aerodynamic performance as well as aeroacoustics. Similarly, novel eVTOL concepts proposed under the Advanced Air Mobility (AAM) research and the Revolutionary Vertical Lift Technology (RVLT) program could greatly benefit from the low-cost broadband noise prediction technology being developed under phase-II. Volcano ScaLES is already licensed by two OEMs that have expressed high interest in further utilizing it for turbomachinery applications upon successful completion of Phase-II activities. The enhancements targeted under this proposal will be made available to these licensees as soon as the validity is demonstrated via quarterly release updates to ScaLES. New turbomachinery acoustics capabilities also provide a natural gateway for licensing opportunities with new players in the emerging commercial advanced air mobility sector given the rapid turnaround times and the low-learning curve for ScaLES utilization in Propulsion Airframe Integration (PAI).

This is a mature technology (TRL 7+) — the realistic path in is usually NASA's Technology Transfer Program: licensing an existing NASA patent, or a Space Act Agreement to use NASA facilities/expertise directly. NASA also runs a startup licensing program with no upfront fee for companies formed to commercialize a specific NASA technology.

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