Assistant Professor Energy Grant awarded
Karen received a 2017 AP Energy Grant from the Swiss National Science Foundation to investigate dynamic stall on H-type wind turbines.
Straight bladed H-type Darrieus vertical axis wind turbines have a much simpler design, a reduced visual, acoustic, and environmental impact and potentially an increased energy density compared to the classical horizontal propellor type. Therefore, vertical axis wind turbines (VAWT) offer an appealing economically viable and socially acceptable option for diversified sustainable power generation in Switzerland. However, the aerodynamics at the blade and rotor level of VAWT are slightly more complex than the classical propellor aerodynamics as e.g. large variations in both the angle of attack and the magnitude of the incident flow velocity induce dynamics stall, a classic example of unsteady flow separation and reattachment. To fully explore the potential and the advantages of VAWT, this project aims for an improved management of unsteady aerodynamic effects with a focus on dynamic stall within the simple design of VAWT. A comprehensive description of the complete dynamic stall life-cycle including time scales and causal relationships related to unsteady flow separation and reattachment, and the influence of external disturbances is sought for with a view to improving the aerodynamic robustness and power density of VAWT. The objective of smart-H is to devise a generalised physics-based dynamic stall description based on systematic experiments of dynamic stall on a two-dimensional blade in a rotating and non-rotating environment mimicking VAWT operation conditions, to improve prediction capabilities of blade loading, aerodynamic robustness, and performance of VAWT. By applying, adapting, and combining state-of-the-art measurements and data analysis techniques, the individual development stages during unsteady flow separation and reattachment and the associated timescales will be identified. Additionally, the influence of external disturbances on the stall development, aerodynamic robustness and performance will be characterised. As such, smart-H will contribute to optimising wind power generation in complex terrains, such as the building environment and mountainous regions, closer to population centres, and in delimited regions where wind conditions are particularly favourable. In a smart age, energy harvesting is not just about optimising energy conversion, but it is also about increasing the ability to generate energy reliably and closer to its point of consumption.