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Title: A near wake study of vortex shedding from bluff bodies at low Reynolds numbers
Author: Corlett, Anne Emily
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1996
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Vortex shedding in the near wakes behind a flat plate and a circular cylinder is studied for Reynolds numbers, R, between 80 and 235. Particle Image Velocimetry (PIV) is used to generate velocity maps of the surface flow from which the vorticity fields are found. The majority of results are taken within the two-dimensional shedding regime for which R < 180. Vortex strength calculations of the Karman vortices show that there is little variation of this quantity with Reynolds number for both bodies, and that, for a circular cylinder, there is no discontinuity at a Reynolds number of 100 as found by Green & Gerrard (1991). When the Reynolds number is increased to above 180, no major changes are found. However, dye visualisations of the flow within the water indicate the presence of three-dimensional transitional modes. The effect of rotation, at Reynolds numbers 100 and 200, on the vortex shedding from a flat plate is also investigated. All the flow characteristics are modified by the rotation. As the ratio of rotational to translational velocity (spin parameter, S) is increased the vortices become weaker and the wakes become increasingly asymmetrical. At Reynolds number 00, vortex shedding ceases by S = 2.4. Examination of the mean streamwise velocity profiles shows that the velocity deficit decreases with increasing spin parameter, and indeed for S = 4.5 Re = 100, the mean velocity has a jet profile. Thus rotation is shown to be an effective means of wake control.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available