Degree Type

Dissertation

Date of Award

2003

Degree Name

Doctor of Philosophy

Department

Civil, Construction, and Environmental Engineering

First Advisor

Lowell F. Greimann

Second Advisor

Partha P. Sarkar

Abstract

Eight rectangular cylinders with aspect ratios that varied from 2 to 7 tested in the wind tunnel at zero degree incidence in a nearly turbulence-free flow field. The models were elastically suspended in the wind tunnel and constrained to a single degree of freedom, vertical motion transverse to the wind flow direction.;Five tests were conducted for every aspect ratio, each with a different system mass. Side plates were utilized to minimize three-dimensional flow effects at the ends of the models and to maximum the two-dimensional flow field.;Prior to testing each model, the following dynamic parameters were determined: natural frequency, mass, stiffness, damping, and Scruton number. Each test began with the model motionless. The wind speed was incrementally increased until vortex-induced transverse vibrations were observed. At each increment of wind speed where transverse vibrations were observed, the maximum amplitude of vibration and the wind speed were recorded.;All models exhibited vortex-induced vibration lock-in during at least one wind regime. Five models exhibited vortex-induced vibration lock-in during two wind regimes. All models exhibited vortex-induced vibration lock-in at the critical reduced velocity predicted by the modified Strouhal number.;Experimental results for each of the forty test cases include the reduced amplitudes and reduced velocities during lock-in, confirmation that lock-in can occur during more than one wind regime, and confirmation that the modified Strouhal number accurately predicts the reduced velocity when lock-in commences.;The relation between the reduced amplitude and the mass/damping parameter was studied. As a result, a parameter for rectangular cylinders was derived as a function of the mass, damping, and geometry of the system. This parameter is analogous to the mass/damping parameter for circular cylinders, the Scruton number. Finally, a single response equation was developed that predicts the amplitude of vortex-induced vibration for a rectangular cylinders with aspect ratios from 2 to 7 utilizing the mass/damping/geometry parameter derived as part of this study.

DOI

https://doi.org/10.31274/rtd-180813-110

Publisher

Digital Repository @ Iowa State University, http://lib.dr.iastate.edu

Copyright Owner

Jeffrey L. Garrett

Language

en

Proquest ID

AAI3118227

File Format

application/pdf

File Size

282 pages

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