CFD Aerodynamic Database for the NASA X-57 Maxwell Airplane
Overview
The X-57 Maxwell is NASA’s unique, all-electric experimental airplane designed to demonstrate a distributed electric propulsion (DEP) high-lift system. This never before flown configuration integrates electric propulsion technology capabilities with the configuration design to have revolutionary benefits to aircraft performance. The goal of the X-57 project is to demonstrate that an all-electric airplane can be more efficient, quieter, and more environmentally friendly than airplanes powered by gas piston engines.
A NASA and industry team are working to demonstrate the increase in efficiency of the emission-free, X-57 airplane compared to its predecessor, the Tecnam P2006T airplane. The team is developing an aerodynamic database using computational fluid dynamics (CFD) results from three NASA centers—Langley, Armstrong, and Ames—to create a piloted simulator, make airworthiness assessments, and for safety analyses. Due to budget constraints, no wind tunnel tests were performed on the X-57 for aerodynamic performance. Therefore, this CFD work directly impacts the safety of flight during testing, and ultimately the life of the pilot.
Project Details
This work would not be possible without the HECC resources, due to the sizes of the computational meshes, the number of hours needed to complete each solution, and the number of solutions needed for the database.
The X-57 Maxwell will use the DEP system to increase lift at takeoff and landing conditions and will cruise efficiently at 150 knots true airspeed (KCAS). The DEP system includes twelve high-lift, electrically-powered propellers that are positioned along the wing leading edge to increase the dynamic pressure over the wing for a boost of lift at takeoff and landing. Over the last year, the primary focus for the Langley CFD team was to determine the impacts of DEP motor failures on lift and controllability using the NASA USM3D and Department of Defense Kestrel codes. A troublesome motor failure scenario for the X-57 is for one contactor bus to fail, causing an asymmetrical lift and thrust situation. Therefore, two scenarios of alternating failed DEP motors were investigated because they cause different asymmetrical conditions. In the Contactor A failure scenario, the alternating failed motors start near the wing tip and in the Contactor B failure scenario, the alternating failed motors start near the wing root.
Results and Impact
In general, results from the three NASA centers compare well for angles of attack (a) less than 10°, after which there are large uncertainties in the data due to differences in stall and flow separation. It is not uncommon for CFD codes to have different solutions for post stall at high a, and it is beneficial for uncertainty quantification to have results from multiple codes. For the landing configuration at 58 knots KCAS and at a 12°, a large region of flow separation is present at the inboard motor for the Contactor B motor failure scenario, while the full DEP system and the Contactor A failure scenario have no flow separation (click on figure at right). The Contactor A failure scenario has a large region of flow separation further outboard on the wing than the Contactor B failure scenario, which has a larger effect on rolling moment coefficient (figure not shown).
The current CFD work develops aerodynamic performance estimates for credible failure scenarios of the DEP system in the landing conditions; these are then used in simulations so the test pilots can prepare for system failures during the actual X-57 flight tests.
Why HPC Matters
The X-57 Maxwell Langley CFD team chose the NASA Advanced Supercomputing (NAS) facility at Ames Research Center to run their simulations due to the NAS resources available for large grid sizes, the solution complexity, and the number of solutions to compute. The NAS facility and resources were critical for computing solutions with multiple CFD codes to estimate the uncertainty in results at high angles of attack. The Langley team used the Pleaides supercomputer for the 380 time-accurate solutions they contributed to the aerodynamic database this year, using one million SBU hours, meshes up to 275 million cells, and up to 900 processors per solution.
What's Next
The NASA Langley CFD team will continue to support the development of the X-57 Maxwell aerodynamic database. Future work includes sinusoidal motion, higher-order Delayed Detached Eddy Simulation (DDES) analyses, benefits of laminar flow, and benefits of the cruise propellers on induced drag. Additionally, there are design changes planned for the cruise nacelle to improve cooling for the motor and internal components and the team plans to model the design changes and estimate the impact to aircraft drag.
More Information
Researchers
- Karen Deere, NASA Langley Research Center Please enable Javascript to see email address.
-
Jeffrey K. Viken, NASA Langley Research Center
Please enable Javascript to see email address.
