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

引入外部扰动控制球形库埃特流的超临界分布

基本信息

批准号：
10650169
负责人：
NAKABAYASHI Koichi
金额：
$ 2.05万
依托单位：
Nagoya Institute of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1998
资助国家：
日本
起止时间：
1998 至 1999
项目状态：
已结题

项目摘要

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.

通过将外部扰动引入具有一个环形 TG 涡流的超临界流模型中，研究了层流-湍流转变过程中再层流的接受性，在具有内部旋转球体的球形库埃特流中间隙比 β=0.14。经向速度扰动是通过扬声器或凸轮系统从极点引入的外部扰动。目前的工作可概括如下： 1．对于每个β，可以普遍定义出现环形TG涡流的最低临界雷诺数Rec1。实验表明Rec1的值（β=0.14时Rec1=860）不受外界干扰的影响。 2．螺旋TG涡和行波的起始雷诺数不受外界扰动的影响。然而，再层化的起始雷诺数受其影响。后者的值随引入外界扰动的频率值而变化。 3．在再层化Re-range中，脉动速度方位分量的均方根值不受外界扰动的影响，而经向分量的均方根值则受外界扰动的影响。4．超临界模态扰动的基频不受外界扰动的影响。5．在再层化Re-range中，脉动速度经向分量的偏斜因子在符号上发生变化，但方位角分量的偏斜因子没有变化。另一方面，平坦度因子不受外界干扰的影响。6．超临界扰动模式对外界扰动的接受程度对再层化Re-range的影响比螺旋TG涡对混沌的Re-range的影响更大。