Conclusions

Taylor vortex flows between two concentric cylinders with finite length have been investigated by the time-dependent numerical method, and the mode transitions during the gradual deceleration of the rotation speed of the inner cylinder have been examined. Then, the following results, which are difficult to be determined experimentally, are obtained.

1.

When the number of cells decreases with the deceleration of rotation, the transition from the normal mode begins with the weakening of a pair of counter-rotating cells with inward radial flow at their boundary.

2.

An anomalous cell has extra cells at the corners of the end wall and both cylinder walls. The anomalous cell extends to the end wall, and it has outward radial flow in the region adjacent to the end wall, while the extra cells have inward radial flow.

3.

In the transition process from the anomalous mode, extra cells accompanied by an anomalous cell develop and merge into a single cell. Then, as the merged cell grows, a pair of cells, which is adjacent to the merged cell and has a boundary with inward radial flow between the two cells, disappears.

4.

In nonunique flows with fixed values of aspect ratio and Reynolds number, the fewer cells a flow has, the more energy it has.