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PROCEEDINGS OF THE ELEVENTH INTERNATIONAL CONFERENCE ON CIVIL, STRUCTURAL AND ENVIRONMENTAL ENGINEERING COMPUTING
Edited by: B.H.V. Topping
Vibration Control of an Offshore Wind Turbine with a Tuned Liquid Column Damper
S. Colwell and B. Basu
Department of Civil, Structural and Environmental Engineering, Trinity College Dublin, Ireland
S. Colwell, B. Basu, "Vibration Control of an Offshore Wind Turbine with a Tuned Liquid Column Damper", in B.H.V. Topping, (Editor), "Proceedings of the Eleventh International Conference on Civil, Structural and Environmental Engineering Computing", Civil-Comp Press, Stirlingshire, UK, Paper 234, 2007. doi:10.4203/ccp.86.234
Keywords: offshore, wind turbine, wind loading, wave loading, tuned liquid column damper, vibration control.
Reductions in the peak acceleration response of a wind turbine system with attached tuned liquid column damper (TLCD) over that of the turbine without a TLCD allow economic design of the structural tower and foundations of the system. TLCDs provide a significant response reduction over a range of frequencies. When the excitation frequencies of the wind and wave loadings coincide with those of the natural frequencies of the wind turbine, the dynamic response of the turbine is such that the harnessing of the wind energy is not possible for an uncontrolled wind turbine. Thus, TLCDs will also increase the efficiency of wind turbines by extending the operating regime. The Kaimal spectrum for the wind part of the loading is combined with the JONSWAP wave spectrum to formulate correlated wind and wave loadings. Joint wind and wave loading time histories have been simulated to be compatible with wind and wave spectra. Time history analysis is carried out on a wind turbine with a TLCD modelled as a multi-degree-of-freedom (MDOF) system. The responses of wind turbines with varying parameters are simulated with the attached TLCD and the reduction in bending moments and structural response for each case are examined.
It was found that when an offshore wind turbine is equipped with a TLCD and subjected to wind and wave forces, reductions of the order of up to 60% in the peak response without a TLCD may be achieved. Significant reductions in the base bending moment were recorded. This leaves the option open to design the wind turbine more efficiently with less steelwork and less foundation expense. Changing soil properties over time may alter the natural frequencies of the structure and although the TLCD is usually tuned to the natural frequency of the structure, it will also dampen the shifted frequencies. Thus, TLCDs will control the vibration under such situations allowing an increased operating time for the wind turbine which will also increase the efficiency of wind turbines.
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