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Abstract

The objectives of this thesis are to investigate, experimentally and numerically, vortex shedding from cylinders submerged in laminar and turbulent flows and various means for its control.

The numerical model used is based on the finite-volume method for the discretisation of the governing transport equations. The k-e turbulence model with the SMART discretisation scheme are used throughout. In order to validate the methods, predictions were obtained for a number of flows for which extensive experimental results exist. These include single square and circular cylinders, as well as two circular cylinders in tandem. The code was also used in the prediction of very high Reynolds number flows (i.e. Re>9xl06), for which no experimental results exist.

The predicted values of the mean drag, the fluctuations of drag and lift and the Strouhal number were satisfactory for the laminar flow cases. For the turbulent cases, however, predictions for the circular cylinder slightly underestimated the mean drag while the fluctuating lift and the Strouhal number were slightly overestimated. The square cylinder results were satisfactory for all regimes.

The flow field that develops around two circular cylinders in tandem was investigated numerically in laminar and turbulent flow conditions. The wide range of well established flow phenomena observed experimentally were reproduced.

The techniques considered for the control of vortex shedding consist of the use of control cylinders, injection into both the approach flow and the wake.

It must be noted that injection into the flow is a novel method for which no previous research is reported. Experiments were carried out for forward injection to maximise its efficiency for a circular cylinder.

All the control techniques used, showed a complete suppression of vortex shedding behind a circular and square cylinder in laminar flow and a square cylinder in turbulent flow conditions. However, levels of suppression were not as high for the circular cylinder in turbulent flow.

It is hoped that the work reported herein will contribute to the understanding of the physics involved in the control of vortex shedding, and the instabilities it causes.

Publication Type:	Thesis (Doctoral)
Subjects:	T Technology > TA Engineering (General). Civil engineering (General) T Technology > TC Hydraulic engineering. Ocean engineering
Departments:	School of Science & Technology > Engineering > Civil Engineering School of Science & Technology > School of Science & Technology Doctoral Theses Doctoral Theses

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