Dynamic stall characterisation and control on vertical-axis wind turbines

According to the International Energy Agency, the global net-zero emissions objective requires the installed wind power capacity to increase 11-fold between 2020 and 2050. The scientific community has recently voiced concerns about the logistic feasibility of scenarios expecting wind power to meet this target. Diversifying wind turbine technology can help mitigate these concerns. Vertical-axis wind turbines provide an attractive design that complements their ubiquitous horizontal-axis counterparts. These turbines can operate in a broad range of wind conditions and emit little noise during operation, making them ideal for urban applications. However, the aerodynamic complexity of vertical-axis wind turbines has hampered their industrial deployment. The blades of vertical-axis wind turbines encounter varying flow conditions throughout a single turbine rotation, even in a steady wind. Varying flow conditions can give rise to flow separation and dynamic stall. Dynamic stall is characterised by the formation, growth, and shedding of large-scale vortices. Vortex shedding on the turbine blades leads to a significant loss in efficiency and load fluctuations that jeopardise the turbine's structural integrity. This thesis investigates the occurrence and control of dynamic stall on vertical-axis wind turbines.