Spinning up NASA Supercomputers for Rotorcraft Design
From monitoring automobile traffic to lifting wounded soldiers out of combat zones, helicopters and other rotorcraft provide many useful civil and military functions without needing airports and runways. Aimed at enhancing the utility of these unique vehicles even further, NASA's Subsonic Rotary Wing (SRW) Project is performing cutting-edge research to help increase their performance and reduce the amount of noise that they produce. Modeling and simulation experts at the NASA Advanced Supercomputing (NAS) Division are greatly advancing these efforts by developing high-fidelity simulations to more accurately analyze the complex aeromechanics of rotorcraft flight.
Rotorcraft simulations are extremely challenging because they must simultaneously account for the interacting effects of rotor blade aerodynamics, blade flexibility, and blade motion. To keep these multi-disciplinary analyses from becoming too computationally demanding, traditional rotorcraft codes—typically referred to as "comprehensive" codes—utilize simplified, lower-fidelity aerodynamics models.
Using NASA's powerful Pleiades and Columbia supercomputers, however, NAS modeling and simulation experts are able to dramatically enhance the accuracy of their rotor simulations by coupling a comprehensive code with high-fidelity computational fluid dynamics (CFD) analyses.
"High-fidelity CFD analyses are advancing the state-of-the-art for accurately capturing aerodynamic phenomena in rotorcraft flight," said Neal Chaderjian, a research scientist on the NAS SRW team. "Rotor blades generate complex vortex and turbulent flow interactions that lower-fidelity models can't adequately resolve. Our team uses a more sophisticated CFD code to compute the rotor aerodynamics, and then couples those results with a comprehensive code analysis, improving its accuracy across the board."
The NAS SRW team has also made several modeling improvements that have further increased the accuracy of their high-fidelity CFD models. For example, they use of a technique called adaptive mesh refinement (AMR) to efficiently and selectively refine the resolution of the computational grid in the specific areas where it is needed most. They have also increased the spatial accuracy of the code's numerical algorithm and implemented a more advanced turbulence model.
Thanks to these advancements, the NAS SRW team was able to compute the efficiency for a hovering V-22 Osprey rotor more accurately than ever before. "For the first time, we have been able to predict the V-22's rotor efficiency within experimental error over a range of different blade pitch angles," Chaderjian said. "Use of AMR in the rotor wake region also revealed complex turbulent structures and interactions that were previously unknown."
These improved high-fidelity simulations—enabled by NASA's powerful supercomputing resources—are providing new insights into the complex aerodynamic and aeromechanic phenomena that are at the heart of rotorcraft performance. Armed with this knowledge, aeronautical engineers can fine-tune rotorcraft designs to create vehicles that are quieter, more efficient, and capable of carrying heavier loads for greater distances.
Related SC11 Demo
High-Fidelity Navier-Stokes Simulation of Rotor Wakes
Contact Information:
Neal Chaderjian
NASA Advanced Supercomputing (NAS) Division, NASA Ames Research Center
neal.chaderjian@nasa.gov
(650) 604-4472
More Information:
- NASA Advanced Supercomputing (NAS) Division: Fundamental Modeling & Simulation Datasheet (PDF-2.3MB)
