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Document Type

Open Access

Degree Program

Mechanical Engineering

Degree Type

Master of Science in Mechanical Engineering (M.S.M.E.)

Year Degree Awarded

2012

Month Degree Awarded

September

Keywords

vibration, tuned, liquid, column, damper, reduction

Abstract

Offshore wind turbines (OWTs) are becoming an accepted method for generating electricity. The environmental conditions of offshore locations often impose high wind and wave forces on OWTs making them susceptible to intense loading and undesirable vibrations. One method to reduce system vibrations is through the use of structural control devices typically utilized in civil structures. Tuned liquid column dampers (TLCDs) show great promise in the application to OWTs due to their high performance and low cost. This thesis examines the use of TLCDs in OWTs.

Equations of motion for limited degree-of-freedom TLCD-turbine models are presented. A baseline analysis of each OWT is performed to generate a quantitative comparison to show how a TLCD would affect the overall dynamics of the system. The models are then subjected to two methods of testing. Optimal TLCD dimensions are derived for the models using a deterministic sweep method. The TLCD configurations examined include those with a uniform and non-uniform column cross-sectional area. The TLCD is shown to successfully reduce overall tower top displacement of each of the OWTs as well as the platform pitch when applicable. In some cases, use of the TLCD actually increases overall tower and platform motion.

This thesis also examines the use of idealized tuned mass dampers (TMDs) in OWTs. Comparisons between the optimized TLCD and the idealized TMD are made with regards to motion reduction and parameter values.

First Advisor

Matthew A Lackner

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