The fully developed Taylor vortex flow between two concentric rotating cylinders with a very small aspect ratio have been investigated by the time-dependent numerical method. The mode transitions during the gradual deceleration of the rotation speed of the inner cylinder have also been examined. The following results were obtained.
(1) The existence of the normal two-cell mode, the anomalous one-cell mode and the twin-cell mode was confirmed numerically. The existence of the twin-cell mode has so far been confirmed only by experimental evidence. Our results showed good agreement with the experimental results.
(2) An unsteady mode of the fully developed flow was obtained. In this mode, vortices are split by each other when the Reynolds number is high. One period of the dynamic movement of flow fields corresponds to two periods of the time variation of mean enstrophy.
(3) Transitions from the normal two-cell mode to the anomalous one-cell mode, from the anomalous one-cell mode to the normal two-cell mode and from the twin-cell mode to the anomalous one-cell mode were predicted. The anomalous cell is accompanied by extra cells at both cylinder sides, and the development and decay of the extra cells causes the mode transition.