City Research Online

Abstract

Inspiration from nature has been used to develop passive, adaptive wing technology with the purpose of reducing aeroacoustic noise and enhancing aerodynamic performance. The work carried out has been specifically focused on the modification of the tip vortex with the addition of leading edge serrations and slotted wingtips. The leading edge serrations are inspired from those found on an owl’s wing which are complex 3D geometries that protrude from the leading edge. And the slotted wingtip is formed of extensions that extend out of the wingtip, and mimic the elastic properties and configuration of tip feathers found on a variety of birds. The thesis is split into two publications and a third that is simultaneously in review, the first two are aerodynamic studies and the third is a combined aerodynamic-aeroacoustic study.

The first publication demonstrated owl’s leading edge serrations are able to break up incoming velocity fluctuations created by the vortex street of varying diameter cylinders upstream. In all cases with the serrations present a broad band reduction in velocity fluctuations was observed, along with a reduction in turbulent kinetic energy. This effect was determined to be dependent on the barb height where the fluctuations interacted with the serrations and was particularly effective at reducing the spanwise velocity component.

The second publication found a self adaptive flexible, slotted winglet was able to break up the tip vortex into smaller dispersed cores. Further, depending on the configuration of the wingtip extensions, it was surmised that the wingtip can be either optimised for enhanced vortex destruction in the wake or for quieter flight. This was thought to be due to the extensions optimally spreading the cores to promote self interaction which resulted in a comparatively shorter decay length (for the wake decay configuration). Or for the quieter flight configuration, promote a smooth continuous roll up of the vortex which is dislocated away from the wing tip and subsequently reduces the tip noise.

The aeroacoustic study brought together the effect of leading edge serrations on the development of the tip vortex and its associated noise. It was evident the serrations were firstly able to reduce the tip vortex strength and secondly to reduce the noise emission in the tip region. Further the magnitude of noise reduction scaled with serration scale, a larger barb resulted in a greater flow turning and subsequently more effective noise suppression.

Publication Type:	Thesis (Doctoral)
Subjects:	T Technology > TJ Mechanical engineering and machinery T Technology > TL Motor vehicles. Aeronautics. Astronautics
Departments:	School of Science & Technology > Department of Engineering School of Science & Technology > School of Science & Technology Doctoral Theses Doctoral Theses

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