Professor Adrian Thomas
Biomechanics, Aerodynamics and Evolution: the adaptations of animals for aerodynamic and biomechanical performance provide a unique opportunity to analyse evolutionary processes because the optimal designs for particular aspects of performance can often be predicted a priori, and independently of the evolutionary history of the animals involved. I use aerodynamic theory to predict optimal morphologies for specific aspects of flight ecology (flight missions), and test the predictions with phylogenetically controlled comparative methods, with mechanical model organisms, and with free-flying or swimming animals in the laboratory, or in the field.
Additional Information
I am Director of Studies in Biological Sciences at Lady Margaret Hall. I run the animal flight research group in Zoology. I am chairman of the Flight section of the Bionis International Biomimetics Network. I am aerodynamics consultant with Airwave GMBH paraglider, hangglider and ultralight aircraft manufacturers.
-
Aerodynamic characteristics of hoverflies during hovering flight
April 2019|Journal article|COMPUTERS & FLUIDSSharp-interface immersed boundary method, Insect flight, Alula, Equilibrium flight -
Free Flight Physiology: Paragliding and the Study of Extreme Altitude.
March 2017|Journal article|High Alt Med BiolAltitude, Aviation, Humans, Hypoxia, Psychomotor Performance -
The flight of the dragonfl y
November 2016|Journal article|Engineer -
Soaring energetics and glide performance in a moving atmosphere.
September 2016|Journal article|Philosophical transactions of the Royal Society of London. Series B, Biological sciencesHere, we analyse the energetics, performance and optimization of flight in a moving atmosphere. We begin by deriving a succinct expression describing all of the mechanical energy flows associated with gliding, dynamic soaring and thermal soaring, which we use to explore the optimization of gliding in an arbitrary wind. We use this optimization to revisit the classical theory of the glide polar, which we expand upon in two significant ways. First, we compare the predictions of the glide polar for different species under the various published models. Second, we derive a glide optimization chart that maps every combination of headwind and updraft speed to the unique combination of airspeed and inertial sink rate at which the aerodynamic cost of transport is expected to be minimized. With these theoretical tools in hand, we test their predictions using empirical data collected from a captive steppe eagle (Aquila nipalensis) carrying an inertial measurement unit, global positioning system, barometer and pitot tube. We show that the bird adjusts airspeed in relation to headwind speed as expected if it were seeking to minimize its aerodynamic cost of transport, but find only weak evidence to suggest that it adjusts airspeed similarly in response to updrafts during straight and interthermal glides.This article is part of the themed issue 'Moving in a moving medium: new perspectives on flight'.Animals, Birds, Eagles, Atmosphere, Air Movements, Energy Metabolism, Flight, Animal, Models, Biological, Wales, Male, Biomechanical Phenomena -
Thermal soaring characteristics in a Steppe Eagle
April 2015|Conference paper|INTEGRATIVE AND COMPARATIVE BIOLOGY -
Wing tucks are a response to atmospheric turbulence in the soaring flight of the steppe eagle Aquila nipalensis.
December 2014|Journal article|J R Soc InterfaceTurbulent atmospheric conditions represent a challenge to stable flight in soaring birds, which are often seen to drop their wings in a transient motion that we call a tuck. Here, we investigate the mechanics, occurrence and causation of wing tucking in a captive steppe eagle Aquila nipalensis, using ground-based video and onboard inertial instrumentation. Statistical analysis of 2594 tucks, identified automatically from 45 flights, reveals that wing tucks occur more frequently under conditions of higher atmospheric turbulence. Furthermore, wing tucks are usually preceded by transient increases in airspeed, load factor and pitch rate, consistent with the bird encountering a headwind gust. The tuck itself immediately follows a rapid drop in angle of attack, caused by a downdraft or nose-down pitch motion, which produces a rapid drop in load factor. Positive aerodynamic loading acts to elevate the wings, and the resulting aerodynamic moment must therefore be balanced in soaring by an opposing musculoskeletal moment. Wing tucking presumably occurs when the reduction in the aerodynamic moment caused by a drop in load factor is not met by an equivalent reduction in the applied musculoskeletal moment. We conclude that wing tucks represent a gust response precipitated by a transient drop in aerodynamic loading.atmospheric turbulence, bird flight, gust alleviation, gust response, soaring, wing tuck, Animals, Atmosphere, Eagles, Flight, Animal, Wings, Animal -
Analysis of the function and mechanics of the wing tuck manoeuvre in a steppe eagle Aquila nipalensis
January 2014|Journal article|INTEGRATIVE AND COMPARATIVE BIOLOGY -
Wake development behind paired wings with tip and root trailing vortices: consequences for animal flight force estimates.
January 2014|Journal article|PLoS OneRecent experiments on flapping flight in animals have shown that a variety of unrelated species shed a wake behind left and right wings consisting of both tip and root vortices. Here we present an investigation using Particle Image Velocimetry (PIV) of the behaviour and interaction of trailing vortices shed by paired, fixed wings that simplify and mimic the wake of a flying animal with a non-lifting body. We measured flow velocities at five positions downstream of two adjacent NACA 0012 aerofoils and systematically varied aspect ratio, the gap between the wings (corresponding to the width of a non-lifting body), angle of attack, and the Reynolds number. The range of aspect ratios and Reynolds number where chosen to be relevant to natural fliers and swimmers, and insect flight in particular. We show that the wake behind the paired wings deformed as a consequence of the induced flow distribution such that the wingtip vortices convected downwards while the root vortices twist around each other. Vortex interaction and wake deformation became more pronounced further downstream of the wing, so the positioning of PIV measurement planes in experiments on flying animals has an important effect on subsequent force estimates due to rotating induced flow vectors. Wake deformation was most severe behind wings with lower aspect ratios and when the distance between the wings was small, suggesting that animals that match this description constitute high-risk groups in terms of measurement error. Our results, therefore, have significant implications for experimental design where wake measurements are used to estimate forces generated in animal flight. In particular, the downstream distance of the measurement plane should be minimised, notwithstanding the animal welfare constraints when measuring the wake behind flying animals.Animals, Flight, Animal, Models, Biological, Rheology, Wings, Animal