This paper performs a systematic numerical study to investigate the effect of rotation friction ratio on the power extraction\nperformance of a passive rotation H-type vertical axis wind turbine (H-VAWT). In contrast to the previous literature, the present\nwork does not impose rotation velocity on the turbine, and the rotation friction ratio which reflects the effect of external load\ncharacteristics on the turbine is introduced to the governing equation of the turbine. During each iteration, the rotation velocity of\nthe turbine is computed after having determined the aerodynamic torque exerted on the blade of the turbine. This ismore consistent\nwith the actual working environment of the H-VAWT.A novel numerical coupling model was developed to simulate the interaction\nbetween the fluid and the passive rotation of the H-VAWT; then, the power extraction performance of the turbine with different\nrotation friction ratio was systematically analyzed. The results demonstrate that the power extraction performance of H-VAWTwill\nbe enhanced when the H-VAWT has appropriate rotation friction ratio. It is also found that the flow separation induced by large\nangle of attack is alleviated essentially if the H-VAWT has appropriate rotation friction ratio, which makes theH-VAWThave better\nenergy extraction performance.
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