Research pick: Wing design takes flight - "The role of pressure field dynamics on the onset of transonic aeroelastic instabilities of high aspect ratio swept wings"

Research in the International Journal of Sustainable Aviation is stacked up to improve aircraft wing design in order to give lift to performance and put safety on a smoother flight path in the critical transonic speed range. The work looks at intricate dynamics of high aspect ratio wings that will fly in the speed range where airflows around the wing can be simultaneously subsonic and supersonic. The actual speed an aircraft is flying where this condition is met depends on many factors but usually lies between 0.8 and 1.2 times the speed of sound as measured at atmospheric pressure, Mach 0.8 to Mach 1.2.

By highlighting the role of wing design and pressure fields in aeroelastic instabilities, the research could have long-haul implications for the development of new aircraft that fly just below or just above Mach 1.

Mario Rosario Chiarelli and Salvatore Bonomo of the Department of Civil and Industrial Engineering at the University of Pisa in Pisa, Italy, investigated two types of high aspect ratio wings: the traditional swept wing and the curved-planform wing. They used a two-way fluid-structure interaction (FSI) analysis, combining computational fluid dynamics (CFD) with structural analysis to study the behaviour of these types of wings in transonic conditions.

Important factors that emerged from the analyses were the power spectral density of both wing-tip displacements and wing aerodynamic coefficients. This information is important for revealing critical instabilities that might arise during a flight at these speeds and so guide modifications to wing design to circumvent instability problems.

The team found that a conventional swept wing displayed instability known as a flutter-buffet. This leads to coupling between structural bending and pressure field oscillations, which would lead to fuel inefficiencies in limited cases but could cause problems with the flight and even the wing itself in extreme cases. By contrast, the curved-planform wing exhibited transonic pressure field oscillations, but these were not a direct cause of aeroelastic instability. This wing design thus shows promise in reducing wave drag effects and enhancing high-speed aeroelastic stability. Even small changes in the detailed characteristics of the design can have a substantial impact on an aircraft’s stability at transonic speeds, the work suggests.

Future work will look at how the geometry of the streamlined enclosues, nacelles, of aircraft engines affect the aerodynamic field and stability issues at such speeds with a view to improving wing design still further.

Chiarelli, M.R. and Bonomo, S. (2023) ‘The role of pressure field dynamics on the onset of transonic aeroelastic instabilities of high aspect ratio swept wings’, Int. J. Sustainable Aviation, Vol. 9, No. 4, pp.332–370.