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Title: Gliding flight in megabats
Author: Edmonds, V. L.
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2006
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Measurements of overall wing morphology were taken from two species of megabat, Rousettus aegyptiacus and Pteropus rodricensis.  Differences in wing morphological parameters can largely be attributed to differences in flight behaviour and ecology. The cross-sectional geometry of the arm wing bones suggests adaptations to torsional loading as well as bending, or axial, loading during flight. The mechanical properties of the arm wing bones were also investigated using microhardness and cantilever bending techniques. The results were indicative of a low Young’s modulus, perhaps an adaptation to increase resilience and prevent buckling of the elongated bat wing bones during flight. 2D membranous wing profile models were constructed using these morphological parameters and wind tunnel test were used to measure aerodynamic force production at Re = 50 000. High life coefficients (CLmax about 2.4) and low L/D ratios (L/Dmax about 10.4) were consistent with values obtained from previous studies on membranous wings. The lift and drag curves also suggested the occurrence of leading edge separation and turbulent reattachment at high angles of attack. Smoke flow visualisation studies confirmed this phenomenon. They also indicated that the protruding spanwise spar improved performance at low angles of attack, yet began to interfere with the process of leading edge separation and turbulent reattachment at higher angles of attack. This strongly suggests that bats should tend to hold their wings at low angles of attack during glide and do not achieve the high lift coefficients of which they are capable. The interplay between leading edge flap angle, spar depth and chord-wise spar position is significantly important in regulating flow separation and force production during gliding flight in such a difficult flow regime.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available