DOI

10.17077/etd.x9g6p2cr

Document Type

Thesis

Date of Degree

Spring 2012

Degree Name

MS (Master of Science)

Degree In

Mechanical Engineering

First Advisor

Buchholz, James H J

First Committee Member

Buchholz, James H J

Second Committee Member

Carrica, Pablo M

Third Committee Member

Ratner, Albert

Abstract

The initial rotation of flat, rectangular plates in quiescent flow were studied experimentally using two-dimensional and stereoscopic particle image velocimetry. The study examined the vortex dynamics of spanwise vorticity created on the upper, leeward surface of each plate of aspect ratio 2 and 4, which consists primarily of a leading-edge vortex. Reynolds numbers of 4,000, 8,000, and 16,000 based on the tip velocity and angles of attack of 25°, 35°, and 45° were investigated at five different azimuthal locations (90°, 180°, 235°, 270°, and 320°). The 25% and 50% spanwise positions for the aspect ratio 4 plate and 50% spanwise position for the aspect ratio 2 plate were studied. For the 25% and 50% spanwise location for the aspect ratio 4 and 2 plate, respectively, the leading-edge vortex structure's shape and coherence appear to be evolving temporally as the plate begins its initial motion. Leading-edge vortex circulation measurements confirm there is a non-monotonic trend showing increasing values until an azimuthal position of approximately 220° where there is a dip in the circulation values, but the circulation then rises towards the end of the range of azimuthal positions investigated. A strong region of counter-rotating vorticity was observed on the surface of the plate beneath the leading-edge vortex from the interaction of the leading-edge vortex with the plate. It was hypothesized that the interactions between the leading-edge vortex and counter-rotating vorticity are an important factor in governing the dynamics and strength of the leading-edge vortex which may ultimately determine whether the leading-edge vortex remains attached. To validate this claim, a transport analysis of the vorticity in the leading-edge vortex was developed to determine the contributions of spanwise flux, tilting of in-plane vorticity components, the shear layer, and annihilation has on the rate of change of circulation of the leading-edge vortex in the spanwise direction. Results of this analysis indicate that annihilation of the leading-edge vortex from entrainment of the counter-rotating vorticity is an important factor in governing the dynamics of the leading-edge vortex.

Keywords

Rotating Flat Plate, Spanwise Vorticity

Pages

xviii, 200 pages

Bibliography

Includes bibliographical references (pages 191-200).

Comments

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Copyright

Copyright © 2012 Craig James Wojcik

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