Asymmetries and similarities of yawed rotor wakes

This paper describes an experimental study of the asymmetries and self-similarity/self-preservation of yawed rotor wakes and the similarity between different yaw angle scenarios. The wake asymmetry is found to increase with increasing yaw angle and also increases in the streamwise direction before the wake reaches a state of self-similarity. Furthermore, if we divide the profiles into left and right parts, the normalized profiles are the same for different streamwise locations even in the region where the profiles have not reached a state of self-similarity. The relation between the asymmetry of the velocity deficit profiles and the yaw angle is derived theoretically and validated by the present experimental measurements. A critical yaw angle is determined for the similarity in the streamwise evolution of the wake between different yaw angle scenarios. Specifically, there is a similarity between different yaw angle scenarios when the yaw angle is below the critical value. The results of this study will be helpful in understanding yawed rotor wakes and establishing a yawed rotor wake model.