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Leading Edge Tubercles as Passive Flow Control Devices
[Thesis]. Manchester, UK: The University of Manchester; 2019.
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Abstract
Leading edge tubercles are bio-inspired passive flow control devices. Investigations in the literature are predominantly in the transitional range 1e5 < Re < 6e5. On simple non-swept sections, tubercles produce an earlier stall and reduce maximum lift. A slight improvement in drag is predominantly reported. Reasonable evidence of topology and corresponding mechanism of operation does not yet exist. In addition to this, the application of tubercles to moderately swept wings is less developed. In this thesis, aerodynamic coefficients (CL and CD) have validated results documented in literature. Flow visualisation results validate the existence of stream-wise vortex pairs which are shown to remain coherent up to 1.5c behind the trailing edge. Surface topology has been elucidated with greater fidelity leading to a new flow topology being assigned. Based on this, a mechanism for the operation of leading edge tubercles has been ventured. Studies on moderately swept wings (20 and 40 degrees) show that tubercle behaviour remains approximately unchanged from the non-swept cases. This allows conclusions from non-swept studies to be applied to swept wings with greater confidence. A Reynolds number suitable application of the findings in this thesis is Small Unmanned Aerial Systems (SUAS). Tubercles could remove unwanted dynamic modes such as wing rock and negative tendencies like tip stall.