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Aerodynamic Design Optimization of a Transonic Strut-Braced-Wing Regional Aircraft

AMS Seminar Series

Speaker: Timothy Chau, Science and Technology Corporation, NASA Ames Research Center

Presentation

Seminar Slide Deck (PDF-22MB)

Abstract

The strut-braced wing is an unconventional aircraft configuration that has the potential to provide significant improvements in the fuel efficiency of transport aircraft through lower induced drag and higher structural efficiency. At transonic Mach numbers, however, the junction region between the wing and strut emulates a transonic channel, which can cause the flow to accelerate and form shock waves, potentially leading to boundary-layer separation and severe drag penalties that can diminish the overall benefits of the concept. Such adverse effects are even more of a challenge at conventional transonic Mach numbers, bringing into question the viability of the configuration for commercial transport aircraft applications.

The present work attempts to address these concerns for a Mach 0.78 strut-braced-wing regional jet class aircraft through the application of aerodynamic shape optimization based on the Reynolds-averaged Navier-Stokes equations. To begin, conceptual-level multidisciplinary design optimization is first performed to size the strut-braced-wing aircraft for a design mission similar to the Embraer E190-E2, with a design range and payload of 3100 nmi and 104 passengers, respectively. Gradient-based aerodynamic shape optimization is then performed on a wing—body—tail model of the aircraft, with the objective of drag minimization at cruise over a 500 nmi nominal mission. Design variables include twist and section shape degrees of freedom, which are realized through a free-form and axial deformation geometry control system. Nonlinear constraints include constant lift, zero pitching moment, minimum wing volume, and spanwise minimum maximum thickness-to-chord ratios. Results from single-point optimization indicate that the optimizer is capable of efficiently mitigating shock formation and boundary-layer separation, especially within the wing-strut junction. With current technology levels, the strut-braced-wing regional jet offers a 12.9% improvement in cruise lift-to-drag ratio over a similarly optimized Embraer E190-E2-like conventional tube-and-wing aircraft, which translates to a 7.6% reduction in block fuel for the nominal mission. Multipoint optimization demonstrates that the low drag performance can be maintained over a range of suitable cruise conditions, resulting in a similar relative savings in block fuel over the same mission.

Biography

Photo of Timothy Chau
Timothy Chau is a research scientist in the Computational Aerosciences Branch of the NASA Advanced Supercomputing Division at NASA's Ames Research Center. He joined the Launch Ascent and Vehicle Aerodynamics (LAVA) team in June 2020, where he works on the conceptual design of advanced aircraft concepts for activities within the Convergent Aeronautics Solutions (CAS) project, and applications involving high-fidelity aerodynamic shape optimization for the Advanced Air Transport Technology (AATT) project. He is also a Ph.D. candidate at the University of Toronto Institute for Aerospace Studies under the supervision of Professor David W. Zingg, where his research focuses on applying high-fidelity aerodynamic shape optimization to the aerodynamic design and performance evaluation of unconventional aircraft configurations. Timothy also has research experience from the industry, including work on the structural optimization of strut-braced wings at Bombardier Aerospace, and the aerodynamic optimization of centrifugal compressors at Pratt & Whitney Canada.