Flow control plays a crucial role in enhancing the wind-resistance safety and comfort of structures. This study employs large eddy simulation (LES) to investigate the optimization of the aerodynamic and wake characteristics of a square cylindrical structure at a high Reynolds number, resulting from the addition of corner-mounted vertical-axis wind turbines (VAWTs). An improved modal-decomposition method named period-averaged proper orthogonal decomposition (PA-POD) is proposed to analyze the flow components. The flow-control mechanism of VAWTs on the square cylinder is revealed using modal decomposition, chaos theory, and linear-stability theory. The results indicate that, after installing passive-rotating VAWTs at the corners of the square cylinder, the vortex shedding pattern changes from P + S to 2S, and the position of vortex shedding is delayed. The fluctuating lift and mean drag of the square cylinder decrease by 55% and 11%, respectively. The PA-POD method proposed in this study is more suitable for problems of flow around a blunt body with poor periodicity of wake–structure evolution, compared to the traditional POD method, and exhibits improved energy-distribution accuracy without high-order mode distortion. The addition of VAWTs does not change the energy proportion of the wake modes, but significantly weakens the coherent structure on both sides of the square cylinder, which suppresses the fluctuating lift. Although the corner-mounted VAWTs cannot eliminate vortex shedding, they suppresses the chaotic behavior of the wake. The linear instability component in the near-wake region moves farther away from the square cylinder because of VAWT action, thereby optimizing the aerodynamic characteristics of the square cylinder.
Feng et al. (Mon,) studied this question.