Axisymmetric propagating vortices in the flow between a stationary and a rotating disk enclosed by a cylinder
Axisymmetric propagating vortices in the flow between a stationary and a rotating disk enclosed by a cylinder
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DOI：
10.1017/s0022112099004346
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发表时间：
1999-05-10
影响因子：
3.7
通讯作者：
Rabaud, M
中科院分区：
文献类型：
--
作者：
Gauthier, G;Gondret, P;Rabaud, M
实验研究了当圆盘半径大于圆盘间距时，两圆盘间定常基流的失稳现象。在探索的范围内的细胞的纵横比，当一个磁盘只有旋转，圆形涡传播到中心观察到高于临界角速度。这些结构自然发生，但也可以通过对圆盘角速度的微小调制来强制。对于每个旋转速率，通过可视化实验重建了不稳定性的色散关系，并且表明该色散关系可以通过在静止圆盘上测量的边界层厚度来缩放。分叉被发现是超临界性质。强迫振幅的影响是有利于线性对流性质的这种不稳定性的非平行向内流动存在于静止盘上方。最不稳定的时间频率被发现是大约四倍的旋转盘的频率。这种主要的不稳定性的阈值的演变被描述为不同的纵横比的细胞。最后，给出了在瞬态条件下进行的两组实验：一组是为了进一步研究不稳定性的可能的对流/绝对转变，另一组是为了与Savas（1983）的脉冲自旋降到静止实验进行比较。
The destabilization of the stationary basic flow occurring between two disks enclosed by a cylinder is studied experimentally when the radius of the disks is large compared to the spacing. In the explored range of the cell aspect ratio, when one disk only is rotating, circular vortices propagating to the centre are observed above a critical angular velocity. These structures occur naturally but can also be forced by small modulations of the angular velocity of the disk. For each rotation rate the dispersion relation of the instability is experimentally reconstructed from visualizations and it is shown that this dispersion relation can be scaled by the boundary layer thickness measured over the disk at rest. The bifurcation is found to be of supercritical nature. The effect of the forcing amplitude is in favour of a linear convective nature of this instability of the non-parallel inward flow existing above the stationary disk. The most unstable temporal frequency is found to be about four times the frequency of the rotating disk. The evolution of the threshold of this primary instability is described for different aspect ratios of the cell. Finally, two sets of experiments made under transient conditions are presented: one in order to investigate further a possible convective/absolute transition for the instability, and the other to compare with the impulsive spin-down-to-rest experiments of Savas (1983).