Tech Briefs Magazine - May 2023 - 48

APPLICATION
BRIEFS
Predicting Buffet Onset on the Transonic Truss-Braced Wing
NASA
Washington, D.C
www.nasa.gov
Boeing
Arlington, VA
www.boeing.com
N
ASA recently issued an award to The Boeing Company for the
agency's Sustainable Flight Demonstrator project, which seeks
to inform a potential new generation of green single-aisle airliners.
Under a Funded Space Act Agreement, Boeing will work with
NASA to build, test, and fly a full-scale demonstrator aircraft and
validate technologies aimed at lowering emissions.
Over seven years, NASA will invest $425 million, while the
company and its partners will contribute the remainder of the
agreement funding, estimated at about $725 million. As part of
the agreement, the agency also will contribute technical expertise
and facilities.
Single-aisle aircraft are the workhorse of many airline fleets,
and due to their heavy usage, account for nearly half of worldwide
aviation emissions. NASA plans to complete testing for the
project by the late 2020s, so that technologies and designs
demonstrated by the project can inform industry decisions
about the next generation of single-aisle aircraft that could enter
into service in the 2030s.
Through the Sustainable Flight Demonstrator project, Boeing
and its industry team will partner with NASA to develop
and flight-test a full-scale Transonic Truss-Braced Wing (TTBW)
demonstrator aircraft.
The TTBW concept involves an aircraft with extra-long, thin
wings stabilized by diagonal struts. This design results in an aircraft
that is much more fuel efficient than a traditional airliner
due to a shape that would create less drag - resulting in its
burning less fuel.
The unconventional configuration of the TTBW, which includes
a high aspect ratio wing, in addition to wing and jury
struts, leads to complex flow phenomena such as transonic buffet,
separated flow, and a turbulent wake.
Current industry best practices tend to employ Reynolds-Averaged
Navier-Stokes (RANS)-based computational fluid dynamics
(CFD) analysis for buffet onset prediction, but accurate
prediction of the onset of buffet and the development of the
separated flow may require more accurate scale-resolving CFD
simulations. To provide more insight into the best practices for
using scale resolving simulations to predict transonic buffet onset,
among other challenges, NASA's Advanced Air Transport
Technology Project launched a collaborative multi-center effort
to develop new methods for simulating the TTBW to better
predict its performance and that of similar truss-braced wing
configurations.
Researchers in the NASA Advanced Supercomputing (NAS)
Division's Computational Aerosciences Branch are simulating
the TTBW's Mach 0.8 cruise configuration to validate and develop
their scale-resolving CFD models. A wind tunnel experiment
was conducted on a half-span model of this configuration
A Transonic Truss Braced Wing aircraft concept being tested in a virtual wind tunnel, showing how its wings interact with the air around them.
(Image: NASA)
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Tech Briefs, May 2023
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Tech Briefs Magazine - May 2023

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