Structural modelling and numerical analysis of dynamic passive flow control mechanisms in flight feathers

Within 100 years of the Wright Brother's first flight, we are already approaching the top of aviation’s technological S-curve. Breakthrough technical improvements have resulted in an undeniable increase in efficiency and range, but today’s aircrafts are still relatively inefficient resulting in a large amount of air and noise pollution. In order to aid further new advancements, in this thesis I set out drawing inspiration from nature - specifically birds; to understand how through more than 150 million years of evolution they came to be the most efficient flying creatures we know. The work presented in this thesis is related to the structural modeling and numerical analysis of the primary feather of the western jackdaw (Corvus monedula) to hypothesize its passive deformations under varying morphology and aerodynamic loading. Starting with Computed Micro-Tomograph scans of a primary feather, several techniques were devised towards realizing the detailed micro – and macro - structure of the feather. Modular capabilities of the model allow for rapidly creating morphological variants of the feather. This is the first attempt to model with such high detail the structural response of the micro-structures of flight feathers. Existing experimental or numerical investigations used highly simplified forms of the feathers structure, allowing the analysis of only stand-alone aspects of deformation dynamics of various avian species. Consequently, these low fidelity models failed to capture how individual sub-micron deformations collectively form the passive response of the feather. Passive dynamic deformation of the feathers micro-structures under increasing load revealed an initial decrease and then and increase in nose droop, overall profile camber and transmissivity of the vanes in order to limit flow separation. Response of feather structures due to change in microstructural morphology revealed high stresses at low loading conditions caused due to their reduced strength and rigidity. Buckling of the barbs at their kink zones was found and is attributed to aforementioned morphological changes and the large and unsteady pressure gradients caused as a result. Based on numerical quantification and evidences, the conclusion of this thesis presents a detailed hypothesis on the series of events and interactions which define the mechanics of dynamic passive flow control abilities of primary flight feathers.