CFD and ANN surrogate modelling for fixing angle optimisation of a Darrieus vertical axis wind turbine

Global decarbonisation requires efficient and reliable renewable energy systems, with Vertical Axis Wind Turbines Formula: see text offering advantages in turbulent and urban environments. This study examines the effect of blade Fixing Angle Formula: see text on the aerodynamic performance of a three-bladed Darrieus Formula: see text using Unsteady Reynolds-Averaged Navier–StokesFormula: see text based Computational Fluid Dynamics Formula: see text simulations coupled with an Artificial Neural Network Formula: see text surrogate model.A parametric analysis was carried out for seven Formula: see text values across a Tip-Speed Ratio Formula: see text range of Formula: see text. Results show that a small positive Formula: see text (toe-out) improves efficiency by delaying stall onset and extending upwind torque production. The optimum case Formula: see text achieved a Formula: see text increase in power coefficient Formula: see text compared to the baseline Formula: see text. In contrast, negative FA reduced performance due to earlier separation and greater downwind losses.The Formula: see text surrogate, trained on Formula: see text data, effectively captured the nonlinear dependence of Formula: see text on Formula: see text and Formula: see text, achieving Formula: see text and a Mean Absolute Error Formula: see text below Formula: see text. Once validated, the Formula: see text enabled rapid optimisation of the design space, locating the global optimum with negligible computational cost.Flow-field and force-coefficient analyses further reveal that positive Formula: see text modifies the incidence-angle distribution, mitigates torque ripple, and suppresses dynamic stall, thereby explaining the observed performance enhancement. Overall, the integration of Formula: see text and Formula: see text provides both physical insight and computational efficiency, establishing a solid foundation for future multi-objective optimisation of Formula: see text considering parameters such as Formula: see text, torque ripple, and self-starting capability.