Master Degree / Yüksek Lisans Tezleri

Permanent URI for this collectionhttps://hdl.handle.net/11147/3008

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Author: search.filters.author.Özbahçeci, BergüzarSubject: search.filters.subject.Wind turbines

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  • Master Thesis
    Hydrodynamic Investigation of an Innovative Floating Platform for Offshore Wind Turbines
    (01. Izmir Institute of Technology, 2022) Özbahçeci, Bergüzar; Özbahçeci, Bergüzar; 03.03. Department of Civil Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
    With the realization of the potential of wind energy in deep water, interest in floating platforms is increasing. In this study, the hydrodynamic behavior of offshore floating wind turbines was examined experimentally and numerically. This study is the first small-scale experimental model study on floating offshore wind turbines in Turkey. Experiments were carried out in the wave channel with dimensions of 40.0m×1.0m×1.4m in the hydraulic laboratory of the IZTECH Civil Engineering Department. A new floating platform developed through a Tübitak project was tested under various wave and extreme wind conditions. Responses of the turbine and platform system and the tensions in the mooring chains were measured. Free decay, hydrostatic, quasi-static, and regular and irregular wave and wind tests were performed. Results were compared with the results of the existing spar platform model tests under the same test conditions. It was concluded that the innovative platform was more stable than the spar platform, especially in terms of rotation in the y direction, which is critical for stable energy generation and fatigue loads. The new platform, together with the turbine and the mooring lines, was also modeled numerically using a potential theory-based program. Experimental free decay tests were used to calibrate the numerical model. After calibration, regular and irregular wave test results were used for the validation. Agreement between the numerical and experimental model studies showed that the numerical model of the innovative floating platform was verified and could be used to develop and examine the platform on a prototype scale.
  • Master Thesis
    Wave Generation and Analysis in the Laboratory Wave Channel To Conduct Experiments on the Numerically Modeled Spar Type Floating Wind Turbine
    (01. Izmir Institute of Technology, 2020) Özbahçeci, Bergüzar; Aktaş, Kadir; Özbahçeci, Bergüzar; 01. Izmir Institute of Technology; 03.03. Department of Civil Engineering; 03. Faculty of Engineering
    The oceans offer immense potential for harvesting sustainable wind energy, with stronger and steadier winds for locations further offshore. Since the feasibility of fixed-bottom offshore wind turbines decreases with increasing water depth, floating offshore wind turbines (FOWT) becomes a promising field of study. As part of a TÜBİTAK project (217M451) that investigates the dynamic performance of different FOWT designs under wind and wave loads, the necessary laboratory wave generation, analysis, and test set-up to conduct physical model experiments of a spar-type FOWT model is established in this study. An investigation of the wavemaker theory yielded that using first-order wavemaker solutions in the laboratory leads to the generation of spurious harmonic waves that do not appear in natural waves. Therefore, the second-order solutions are applied to the piston-type wave generator for a closer approximation of natural waves in laboratory conditions. A numerical model investigation of a reference spar-type FOWT is conducted to gain insights into spar design using ANSYS AQWA. The results indicate that the spar model dynamic responses are susceptible to low-frequency waves in pitch and surge degrees of freedom as its natural frequency lies in that region which further emphasizes the importance of generating laboratory waves using second-order wavemaker theory. Additionally, a spar-type floating platform is modeled at the 1/40 Froude scale, to use in the hydraulic model experiments. The wave measurement set-up is fully implemented and theoretically generated waves are measured for validation. In conclusion, regular and irregular wave generation and wave analysis in the time and the frequency domain could be possible in the wave channel of IZTECH Civil Engineering Hydraulic Laboratory.