Unlock the Secrets of Flight: Discovering the Wonders of the Grey-headed Albatross

Posted on July 13, 2023

Title: Unlock the Secrets of Flight: Discovering the Wonders of the Grey-headed Albatross

Authors: Alex Winter, Janine Schoombie, Dr Lelanie Smith

At the University of Pretoria, the Aeronautical Research Group is investigating the geometric and aerodynamic features of avian species of which there is very little information available. This ground-breaking research promises to offer valuable insights to engineers in design applications and the study of low Reynolds number (Re) flow phenomena. In particular the focus is on unpacking the unparalleled efficiency in flight of the Grey-headed Albatross (Thalassarche chrysostoma, GHA).

Grey-headed Albatross on Marion Islands. Photograph courtesy of Janine Schoombie

Recently, researchers considered using an aerofoil design parameterisation model to describe a laser-scanned 3D point cloud of a Grey-headed Albatross wing specimen that was donated by the FitzPatrick Institute of African Ornithology (UCT). This combination allowed the researchers to generate accurate spanwise aerofoils and construct a comprehensive 3D model of the preserved wing. Feathered wings are not rigid and, even if one only focuses solely on soaring flight, the wings of the albatross can morph with changes in air pressure acting on the wing in different flight conditions. In order to analyse the potential morphing of the aerofoil sections, the team employed a pseudo 2D computational fluid dynamics model with a single objective design exploration, using commercial software Siemens Star-CCM+ Design Manager. The design exploration attempted to morph the aerofoil to maximise the aerodynamic efficiency at conditions typically seen in soaring flight. This model therefore  predicts the passive morphing of the albatross’s wing aerofoil in flight, taking into consideration the biological wing constraints observed in live bird wings.

The aerofoil creation process in CloudCompare showing (left) the lines where the sections were to be taken and (right) the result of the sectioning process. Scans are courtesy of Mitchell Whiting.

The results were promising, with the best-performing aerofoil exhibiting a decrease in camber compared to the highly cambered unmorphed version. This adjustment significantly improved the maximum lift-to-drag ratio, increasing it from 3 to 44, well above the expected efficiency of around 25 from the available literature. The most substantial enhancement came from a reduction of pressure drag, which decreased by a factor of 13.6 compared to the original wing. These results show that the use of engineering tools in the study of birds in flight may reveal more of the capabilities of seabirds than what previous research suggests.

Although this study offered valuable insights, the research team continues to refine the methodologies for extracting information from preserved bird wings. Currently, four final-year students are guided by the primary PhD student on the project to continue with wind tunnel experiments and aim to extract improved scans with the assistance of the UP Makerspace. The team also hopes to verify the current methods with those used to extract information from live birds in flight. Such comparisons will enhance our understanding of the aerodynamic capabilities of pelagic seabirds and inspire future advancements in engineering design.

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