Doctor of Philosophy
Civil and Environmental Engineering
Prof. Ashraf El Damatty
Prof. Kaoshan Dai
Prof. Wensheng Lu
Wind turbines are among the fastest-growing technologies for producing sustainable energy. In order to enhance efficiency, most wind turbines are built in rural locations where strong wind speeds are anticipated. These areas can be exposed to thunderstorms and extreme wind events, which are becoming more frequent and destructive owing to climate change. Downbursts are one of these events linked with thunderstorms, which occur in a sudden and localized manner. The wind loads specified in the wind turbine design codes are based on large-scale wind events and do not consider the effect of downbursts. As such, the current thesis aims to investigate the wind turbine behaviour under downburst wind effect. To achieve that, the numerical model, HIW-TUR, is developed incorporating a downburst wind field generated based on a previously developed Computational Fluid Dynamics (CFD) simulations, and a wind turbine structural model developed in this thesis to simulate the structural behaviour of the tower and blades. This numerical model is capable of predicting the quasi-static response of wind turbines under downbursts taking into consideration different downburst parameters (the jet diameter, the jet velocity, and the event location) as well as the change in the pitch angle of the blades. Dynamic response of wind turbines under downbursts is assessed using the open-source code, FAST, with two developed modules. These modules are responsible for introducing the downburst wind field into FAST and simulating the interaction between the downburst wind field and the wind turbine structure. Based on an extensive parametric study conducted using the developed numerical models, a complete set of design load provisions are proposed to simulate the critical effect of downbursts on the tower and the blades of generic wind turbines. Finally, HIW-TUR is extended to generate HIW-FARM to study a group of wind turbines under the effect of downbursts.
Summary for Lay Audience
Because of their green nature, wind turbines are one of the most rapidly growing sources of renewable energy. Wind turbines are often located in rural areas, far from cities, where potential wind speeds are anticipated to enhance the wind turbine efficiency. These areas can be subjected to thunderstorms and extreme wind events, which are becoming more frequent and severe as our climate changes. A lot of wind turbine failures have been observed recently under extreme wind events. Downbursts are an example of extreme wind events, which occur in a sudden and localized manner. The design codes for wind turbines show a lack of information regarding the analysis and design of wind turbines to sustain such an extreme wind event. Research also has shown that limited number of studies were devoted to provide an understanding on the behaviour of wind turbines under downbursts. Considering the sparsity of information on this matter, and the critical nature of such structures, this thesis discusses the methodology of a novel numerical method to investigate the behaviour of wind turbines subjected to downburst wind loading. The developed numerical model is capable of studying the response of wind turbines taking into consideration the different parameters of a downburst, which are the jet velocity, the size of the downburst and its location relative to the wind turbine. The model also accounts for the change in the pitch angle of the blades, which is a parameter typically used to control the blades rotation and power generation. In order to understand the wind turbine behavior under these parameters, a parametric study is conducted by varying the downburst parameters and the blade pitch angle on a real wind turbine as a case study. By comparing the downburst loads to the wind loads recommended by the design code, it is observed that downburst loads have higher impact on wind turbines than the design loads. As such, downburst design loads are developed in this thesis and are presented in a format, which can be used by designers and implemented in the design codes. The ideal group configuration, which minimizes the downburst effect on a group of wind turbines in a wind farm, is then determined by studying a number of wind turbines under the downburst effect.
Ahmed, Mostafa Mohamed Mohamed Ramadan, "Numerical Models and Design Loads for Wind Turbines under Downbursts" (2022). Electronic Thesis and Dissertation Repository. 8916.
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Available for download on Saturday, October 26, 2024