Date of Award

2009

Publication Type

Master Thesis

Degree Name

M.A.Sc.

Department

Mechanical, Automotive, and Materials Engineering

Keywords

Applied sciences

Supervisor

Dr. S. Cheng

Supervisor

Dr. D. S-K Ting

Rights

info:eu-repo/semantics/openAccess

Abstract

Bridge stay cables are prone to dynamic excitations by wind. Depending on the orientation and mechanical properties of cable, wind speed, and other environmental factors, unstable cable response of different features could occur. The current work focuses on exploring the possible excitation mechanisms associated with two different types of wind-induced unstable responses observed on a rigid circular cylinder model in a series of wind tunnel tests. Characteristics of critical flow past a circular cylinder model in cross-flow were first studied to provide additional insight into the impact of critical Reynolds number regime. Then, the limited-amplitude and divergent type responses of a wind tunnel cable model were investigated. Unsteady surface pressure data were utilized to determine the separation angle, aerodynamic damping ratio, spatial correlation, and power spectra of lift and drag forces. It has been found that the divergent type response was not only accompanied with negative aerodynamic damping ratio, but also it occurred when the spatial flow was highly correlated along the cylinder. In addition, a breakdown range was detected for cable-wind relative angle around 60° within which flow characteristics could be significantly altered. This would lead to suppression of regular Karman vortex shedding in the subcritical Reynolds number range which is known to be the reason for the limited-amplitude response.

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