Endeavour Simulations Help Reshape the Future of Aircraft Fuel Efficiency
Flying home from summer vacation, you look out the window as the flight attendants prepare for landing. Your gaze follows the span of the wing and beyond, out to an infinite blue horizon. Although it seems that the aircraft has not changed since the beginning of the flight, it weighs much less now than when you left the ground. The amount of fuel needed to power a flight—especially a long-haul flight across the ocean—accounts for a significant amount of an aircraft’s total weight at takeoff. As fuel burns, the aircraft gets lighter, which along with varying speed, altitude, and other factors leads to continually changing flight conditions.
Aircraft wings are typically designed for optimal aerodynamic performance at a single or averaged mid-flight condition. Although this design provides near-optimal efficiency throughout flight despite the changing conditions, for truly optimal efficiency the best possible wing shape would be different for each flight condition. This means that for the majority of the flight, the wings are “off-design”—not fully optimized for the best possible performance. This problem is exacerbated in newer aircraft with highly flexible wings.
But what if the wings could be actively reshaped during flight to adapt to the changing conditions? To research one possible way for aircraft industry designers to achieve this, aerospace engineers are running simulations on the Endeavour supercomputer at the NASA Advanced Supercomputing (NAS) facility at Ames Research Center.
“We set out to examine the potential benefits of a distributed flap system—placing flaps down the length of the wingspan that can be moved independently to adaptively reshape the wings for varying flight conditions,” explained David L. Rodriguez, senior research scientist and engineer at Ames. “This would keep the wings operating near peak efficiency throughout the flight.”
Rodriguez and his colleague Michael Aftosmis simulated such a flap system on a standard NASA aircraft model, running multiple scenarios with the flaps in different positions to determine which shapes would work best at various flight conditions. Their goal was not only to find the optimal shape for each condition, but to determine how much better the reshaped wing would perform at each condition than the baseline wing design.
“Better aerodynamic performance leads to higher fuel efficiency, which in turn leads to new, lighter aircraft designs,” Rodriguez said. Then the benefits really begin to take off, as lighter planes require even less fuel.
High-fidelity aerodynamic shape optimization takes a lot of computing power. Although Rodriguez and Aftosmis developed an approach that is roughly five times more computationally efficient than typical analysis methods, their complex simulations required the advanced capability of the Endeavour supercomputer. The researchers ran about two dozen full aerostructural optimizations on Endeavour that equated to thousands of individual computational fluid dynamics simulations.
Their results showed improvements in aerodynamic performance and potential fuel savings in all of the simulation scenarios. There are trade-offs, however. Existing flap systems on today’s planes—used primarily to assist takeoff and landing, but also for drag reduction—require heavy mechanical equipment on each wing to operate. Extending a distributed flap system across an entire wingspan using existing technology would add weight and increase complexity; these factors need to be considered carefully when assessing lifecycle costs.
According to the researchers, as the technology evolves, distributed flap systems could become commonplace within the next few decades. Such systems could not only be preprogrammed for certain anticipated flight conditions but also coupled with advanced flight controls to automatically adjust the flap deployment to actual flight conditions on-the-fly.
— Michelle Moyer, NASA Ames Research Center
This work was supported by the Aeronautics Research Mission Directorate’s Advanced Air Transport Technology project under the Performance Adaptive Aeroelastic Wing element led by Dr. Nhan T. Nguyen.
