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Author ORCID Identifier

https://orcid.org/0000-0002-0171-1934

AccessType

Open Access Dissertation

Document Type

dissertation

Degree Name

Doctor of Philosophy (PhD)

Degree Program

Mechanical Engineering

Year Degree Awarded

2019

Month Degree Awarded

May

First Advisor

Yahya Modarres-Sadeghi

Second Advisor

David Schmidt

Third Advisor

Paul Sievert

Subject Categories

Acoustics, Dynamics, and Controls | Fluid Dynamics | Ocean Engineering | Other Mechanical Engineering

Abstract

The goal of this thesis is to experimentally study the structural dynamics, wake interaction, and fluid forces on the multiple-degree of freedom systems typical of floating wind turbines. Vortex--surface alignment about flexibly-mounted prisms is studied to investigate the response of barges and semi-submersible hulls, and new results pertaining to the galloping response kink for a prism with dual inline--crossflow resonance is presented. Flow--induced oscillations of a spar model free to rotate in 3D space is replicated and observed as 2D figure--eight orbits about the center of the spar. Methods to suppress the flow from exciting the spar are proposed. The influence of mooring cable concavity is studied for a cylinder with crossflow--inline flexibility, and the effect of the axial tip on higher harmonic fluid forces is shown to have a significant reduction on the inline and crossflow oscillation components when concave. As a separate project, flow-induced oscillations are made beneficial to the operation of wind turbines via the study of larynx phonation to create an air-driven ultrasound generator for use as a bat deterrent on wind turbine blades.

DOI

https://doi.org/10.7275/ayn7-9a82

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