Researchers in the NASA Advanced Supercomputing (NAS) Division at Ames Research Center are supporting the development of the agency’s SUbsonic Single Aft eNgine (SUSAN) aircraft concept by providing high-fidelity computational fluid dynamics (CFD) analysis capabilities for investigating the design and performance of novel integrated propulsion technologies. SUSAN is an innovative turbo-electric transport aircraft being developed to help address growing concerns surrounding the future environmental sustainability of the aviation industry. The CFD work is done in collaboration with researchers at NASA’s Glenn, Langley, and Armstrong Flight Research Centers, and is funded as a NASA Convergent Aeronautics Solutions (CAS) project.
Accurate and efficient CFD tools are well positioned for helping researchers understand the complex interactions involved, while also providing a means for rapid design turnarounds when exploring the trade space of such novel aircraft technologies.
CFD simulations for the SUSAN transport aircraft were performed using the NAS Division’s Launch Ascent Vehicle Aerodynamics (LAVA) curvilinear solver for the Reynolds-Averaged Navier-Stokes (RANS) equations and includes an an actuator zone method for modeling the effect of each propulsor on the airframe aerodynamics. Investigations of the aerodynamic and propulsive coupling for the aft fuselage turbofan involved simulations that include models for the wing, fuselage, tail, and aft engine. The focus was to gain insight into the impact of the airframe aerodynamics—including the effect of “downwash” from the wing—on the performance of the propulsion system. Investigations of the integrated distributed propulsion systems were performed through a simplified wing model with an isolated ducted fan unit installed either in an over- or under-wing configuration to examine design trends and tradeoffs, especially between aerodynamics and propulsion. All simulations were performed at Mach 0.785 and an altitude of 37,000 feet to simulate nominal operating conditions for the aircraft.
This project was made possible by the HPC resources available at the NASA Advanced Supercomputing facility, enabling fast and efficient design turnarounds for exploring the aerodynamics of novel integrated propulsion technologies.
Results and Impact
The simulation results help guide the design efforts for investigating novel integrated propulsion systems that can provide significant improvements to aircraft efficiency. By understanding the impact that the integration has on the external aerodynamics of the airframe, researchers can get a better idea of how to efficiently integrate the propulsors with the aerodynamic surfaces to maintain or enhance the lifting capabilities of the aircraft and reduce drag. Such simulations can also help determine the benefits enabled by distributed propulsion and boundary layer ingestion, while providing measures of the inlet distortion experienced by each propulsor. These simulations also help engineers identify and evaluate the advantages of different propulsion system configurations, such as over- and under-wing distributed systems, which require accurate simulations of the flow field to understand the interactions between aerodynamics and propulsion.
Why HPC Matters
This project was made possible by the high-performance computing resources available at the NAS facility, which enabled fast and efficient design turnarounds for exploring the aerodynamics and propulsion trade space of these novel integrated aircraft technologies. This allowed for a rapid exchange of design iterations between the various disciplinary teams located at each of the four research centers, providing a virtually seamless collaborative investigation of the design factors involved. All CFD simulations were performed on the Pleiades supercomputer with up to 1,500 Ivy Bridge cores utilized per run to enable several dozens of design iterations.
Future work will include extending the investigations of these integrated propulsion systems to a full aircraft configuration in order to assess the system-level performance of the SUSAN concept. High-fidelity aerodynamic shape optimization methodologies will also be used to automate and further improve the aero-propulsive design of each aircraft component. Other work will include further collaborations with researchers at NASA’s Glenn, Langley, and Armstrong Flight Research Centers on investigating the structural design of each integrated propulsion system, the implementation of natural-laminar-flow wing technology, and the development of scaled model prototypes for studying not only the coupling between aerodynamics and propulsion, but also the potential for control and stability augmentation through thrust vectoring.