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Title: Aerodynamic flow sensing in the desert locust (Schistocerca gregaria)
Author: McCorkell, Fergus
ISNI:       0000 0004 6496 7536
Awarding Body: University of Oxford
Current Institution: University of Oxford
Date of Award: 2016
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Insects are richly instrumented with sensors used in flight control. Whilst we have good knowledge of the basic physiology of these structures, in many cases we have only a cursory understanding of the likely stimuli each sensory system receives during flight or why these systems have evolved to perform their particular function. This thesis examines the role and optimisation of arrays of cephalic flow-sensitive hairs, called trichoid sensilla, in the flight control of the desert locust (Schistocerca gregaria). Particle image velocimetry and computational fluid dynamics are used to measure and simulate the airflows being received by the fields of sensilla during flight. The visualisations reveal distinct local flow conditions over each field and how these are modulated differently by perturbations. The geometry of every individual hair is captured using both benchtop and synchrotron based X-ray micro tomography (XMT). These scans enable three-dimensional measurement of each hair's direction of curvature, which represents the direction of peak sensitivity to airflow. By combining flow stimulus and directional sensitivity data, we provide strong evidence for separate fields being tuned for distinct roles: some as step detectors for monitoring stall at extreme angles of attack, others as graded sensors for angles of attack and sideslip, and possibly for monitoring airspeed. Finally, we examine the flight response of tethered locusts to varying aerodynamic stimuli by changing the angle of sideslip and selectively covering fields of sensilla from oncoming airflow. We demonstrate a clear role for the sensilla in modifying the forces and moments generated under varying sideslip, as well as in changing the underlying natural modes of motion of the system. We reveal the axes about which the locusts are unstable under our experimental conditions, and demonstrate the necessary additional sensory feedback required to stabilise the system fully. The combined data represent a comprehensive and thorough examination of the complete cephalic flow-sensing system, providing insights applicable to both further biological study on multi-modal flight control and the use of bio-inspired arrays of sensors for manmade applications.
Supervisor: Taylor, Graham ; Bomphrey, Richard Sponsor: Defence Science and Technology Laboratory (Dstl)
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available