Control of super-critical distribution in spherical Couette flow by introduction of outside disturbances

点击翻译按钮获取中文摘要

Receptivity of relaminarizing flow in the laminar-turbulent transition process are investigated by the introduction of the outside disturbances into the super-critical flow models with one toroidal TG vortex for clearance ratio β=0.14 in the spherical Couette flow with an inner rotating sphere. Meridional velocity perturbations were introduced as the outside disturbances from a pole by a loudspeaker or cam system. The present work can be summarized as follows :1. Lowest critical Reynolds number Rec1 for the occurrence of toroidal TG vortex can be defined universally for each β. It is clarified experimentally that the value of Rec1 (Rec1=860 for β=0.14) is not influenced by the outside disturbances.2. The onset Reynolds numbers of spiral TG vortex and travelling waves are not influenced by the outside disturbances. However, the onset Reynolds number of the relaminarization is influenced by it. The value of the latter changes with the value of frequency of introduced outside disturbance.3. RMS value of the azimuthal component of fluctuating velocity is not influenced by the outside disturbance, but that of the meridional component is influenced by it in the relaminarizing Re-range.4. Fundamental frequencies of the disturbances in the super-critical modes are not influenced by the outside disturbances.5. Skewness factor of the meridional component of fluctuating velocity changes on the sign in the relaminarizing Re-range, but that of the azimuthal component does not change. On the other hand, the flatness factor is not influenced by the outside disturbance.6. The receptively of the super-critical disturbance modes to the outside disturbances has greater influence in the relaminarizing Re-range than the Re-range from the spiral TG vortex to the chaos.