Loads and dynamics analysis of a downwind offshore floating wind turbine

• Main Author: Koh, Jian Hao
• Other Authors: Ng Yin Kwee, Eddie
• Format: Theses and Dissertations
• Language: English
• Published: 2017
• Subjects: DRNTU::Engineering::Mechanical engineering::Alternative, renewable energy sources; DRNTU::Engineering::Aeronautical engineering::Aerodynamics; DRNTU::Engineering::Mechanical engineering::Fluid mechanics
• Online Access: http://hdl.handle.net/10356/72314
• Institution: Nanyang Technological University

Current offshore wind turbine designs are basic concepts using standard upwind land-based wind turbines 'marinised' using a platform from the offshore oil and gas industry with additional anticorrosion and structural stiffness. This design conservatism is present to avoid significant changes to the proven technology of land-based wind turbines and offshore foundations, to assure technical feasibility and economic viability for short term development. This study aims to tackle some of the technical challenges and gaps identified for implementing downwind floating wind turbines. Using data obtained from open-sea testing of the 1/6.5th scale prototype of the SWAY hybrid tension-leg spar-type floating wind turbine, a FAST model of the SWAY system was built and validated using an improved version of FAST numerical simulation tool. The author developed a novel meshing and modeling method to conduct computational fluid dynamics analysis efficiently for high Reynolds number flow over bluff bodies that can produce reasonable predictions of turbulent wake profile. A new tower influence model was proposed by the author based on the computational fluid dynamics analysis conducted for different 18 test cases generated to analyze the flow across a wind turbine tower. The new tower influence model proposed by the author showed significant improvement over the models used in FAST and Bladed. Similarly, 9 test cases were generated to analyze the flow across a wind turbine nacelle based on each permutation of smooth- and sharp-edged nacelles, and cylindrical or cuboid shaped nacelles. The simulation and experiment results showed very good comparisons over various flow parameters. Key findings were noted that support in the development of nacelle influence model.