Critical issues in the moving reference frame CFD simulation of small horizontal axis wind turbines

Steady computational fluid dynamics with the Moving Reference Frame method has shown promise as a tool for assessing the aerodynamic performance of small horizontal-axis wind turbines, offering sufficient accuracy with low computational costs, thus supporting the development of these machines and facilitating their vital role in the growing distributed energy systems. However, accurately simulating the intricate low Reynolds number flow around the blades of these turbines remains a significant challenge, with certain critical issues yet to be fully resolved. Through a comparative literature review, this study firstly uncovered a lack of standardized simulation settings for small horizontal axis wind turbines, resulting in inconsistencies across different studies. Addressing this gap, the research delves into the critical issues identified, specifically the computational domain crosssection shape and size, discretization scheme accuracy, meshing criteria, freestream turbulence intensity, and turbulence modelling. To rectify these challenges, the study conducts a detailed sensitivity analysis of the aforementioned parameters applied on a well-documented turbine in the literature as a case study. For validation purposes, an empirical method is employed to correct the tunnel wall blockage effect on the case study turbine experimental data. This method is verified, and the correction of the closed test section tunnel data, notably, shows a significant blockage effect, contradicting the notion of insignificance for a blockage ratio of 11.8% in the literature. The analysis revealed how incorrect simulation settings can yield misleading results that initially may align with experimental data but fail to guarantee a reliable numerical setup for extending the study. Ultimately, this research furnishes best practice guidelines for establishing accurate simulation setups.