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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.

Computational aeroacoustics study of circular and elliptical jets

Alonso, Mikel January 2007 (has links)
No description available.

Sensitivity study of HLFC nacelles

Standfuss, S. January 2004 (has links)
No description available.

Steady and unsteady features of twin-jet STOVL ground effects

Cabrita, Pedro Miguel January 2006 (has links)
No description available.

Aerodynamics of nonslender delta wings

McClain, A. January 2004 (has links)
No description available.

Active control of low frequency buzz-saw tones

Wilkinson, Matthew Jon January 2005 (has links)
No description available.

An experimental investigation into wing in ground effect over flat and wavy surfaces

Moore, Nicholas John January 2005 (has links)
No description available.

A hybrid spectral discretisation and iterative solution methods for acoustic models in potential flow

Laird, Alistair January 2004 (has links)
No description available.

The investigation of blade-vortex interaction noise using computational fluid dynamics

Morvant, Romuald January 2004 (has links)
No description available.

Investigation of the structural interaction between the wing and body of a class of simple remotely piloted aircraft

Ahn, D. M. January 1982 (has links)
Effects of various wing-body interaction design parameter variations on the structural behaviour of a small RPV have been investigated using the finite element method on an adhoc basis rather than a classical analytic approach. The method in use is based on the substructuring displacement method considering the body and the wing as two major substructures. The elastic coupling effect of wing stiffness on the body structural behaviour also examined. By comparing classical analysis methods to the present. investigation, comments are made upon the use of those methods in the design analysis of the RPV class of structure. From the calculated results, general guidelines on the structural wing-body interaction analysis or design of this class of vehicle have been proposed. A set of finite element programs have been developed for the present investigation, and relevant finite elements based on the displacement assumption have been formulated.

Plunging low aspect ratio wings in low Reynolds number flows

Calderon, Dario January 2014 (has links)
A growing desire exists to develop Micro Air Vehicles (MA Vs) that fall within a 15cm span. Their small scale and low operating flight speeds encourage a low Reynolds Number (Re) regime, in the order of Re - 104 - 105 . Wings under these conditions are highly susceptible to separated flows, posing a significant challenge for the MA V. Natural flyers are able to confront these issues through flapping flight, which has inspired an entire research field on the aerodynamics of oscillating wings. While the number of parameters that govern the problem is exhaustive, studies are required to explain the contribution of each and any phenomena that may ensue. This lends itself to a canonical approach. This thesis presents an experimental study on various wing geometries, undergoing a small amplitude oscillation in the form of a pure plunge. The focus lies on understanding the three-dimensional effects of oscillating a finite wing with a positive geometric angle of attack, to encourage greater lift than that achieved from an unforced wing. This expands on the current research which predominantly focuses on the thrust generating capabilities of a 'flapping' airfoil. Force measurements, hot-film measurements, Particle Image Velocimetry (PIV) and volumetric velocimetry, are used to examine the performance and flow topology that ensues from actuating the various wings. The study presents time-averaged force measurements as a function of Strouhal number (non-dimensionalised plunge frequency) for the various low aspect ratio wings. It is shown that while the finite nature of these wings suppresses lift, significant improvements are nonetheless possible. For example, a semi Aspect Ratio = 2 NACA0012 rectangular wing, is able to achieve 180% more lift than the unforced wing. A phenomenon arises in which peaks are observed in the time-averaged lift curve, for various rectangular and delta wing planforms. This suggests optimal lift conditions at particular Strouhal numbers. In a similar manner to a 2D airfoil the oscillating wing stimulates the formation of both leading and trailing-edge vortices. The trajectory and timing of these vortices, in relation to the plunge cycle, appear to be significantly affected by Strouhal number. At particular frequencies, the vortices interact in such a way that their induced flow generates a significant region of low velocity, recirculating flow near the wing. The size of the recirculating region closely correlates with the shape of the time-averaged lift curve, agreeing well with points of troughs and peaks when this region is maximised and minimised, respectively. It is thought that these Wing/vortex and vortex/vortex interactions contribute to the selection of optimal frequencies, and therefore determine optimal lift for the oscillating wing.

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