Furukawa Hiroyuki, Watanabe Takashi, Toya Yorinobu, Nakamura Ikuo
Graduate School of Human Informatics, Nagoya University, Nagoya 464-8601 Japan.
Phys Rev E Stat Nonlin Soft Matter Phys. 2002 Mar;65(3 Pt 2B):036306. doi: 10.1103/PhysRevE.65.036306. Epub 2002 Feb 13.
Numerical investigation is carried out on the flow pattern exchanges found in Taylor-Couette flows between two concentric rotating cylinders. The inner cylinder rotates while the outer cylinder and both end walls are stationary. The aspect ratio (column length/gap width) is small, and its range is from 0.5 to 1.6. Previous experimental results for this range of the aspect ratio showed that the steady flow patterns are classified into three groups: the normal two-cell mode, anomalous one-cell mode and twin-cell mode. All modes found by experiments are predicted in the present numerical calculation. Besides these three flow modes, an unsteady mode is predicted, which is time dependent and fully developed. The existence of the unsteady mode is also confirmed by our experiments. When the inner cylinder starts to rotate from rest, vortices at the corners of the inner cylinder and both end walls develop, and they induce the normal two-cell mode. The flow of the anomalous one-cell mode or twin-cell mode appears after an abrupt breakdown of symmetric two-cell mode flows. During the gradual deceleration of the inner cylinder, the transitions of flow modes occur. We observed mode transitions between the normal two-cell mode and anomalous one-cell mode and mode transitions from the twin-cell mode to the normal two-cell mode, anomalous one-cell mode, and unsteady mode. The critical loci where these mode transitions appear are determined. The numerical confirmation of the twin-cell mode is a different result obtained in the present study.
对两个同心旋转圆柱之间的泰勒 - 库埃特流中发现的流型转换进行了数值研究。内圆柱旋转，而外圆柱和两个端壁静止不动。纵横比（柱长/间隙宽度）较小，其范围为0.5至1.6。此前针对该纵横比范围的实验结果表明，稳定流型可分为三组：正常双胞模式、异常单胞模式和双胞模式。实验发现的所有模式在本次数值计算中均得到了预测。除了这三种流模式外，还预测了一种非定常模式，它随时间变化且充分发展。我们的实验也证实了非定常模式的存在。当内圆柱从静止开始旋转时，内圆柱与两个端壁拐角处的涡旋会发展，并引发正常双胞模式。对称双胞模式流突然崩溃后，会出现异常单胞模式或双胞模式的流动。在内圆柱逐渐减速过程中，会发生流模式的转变。我们观察到了正常双胞模式与异常单胞模式之间的模式转变，以及从双胞模式到正常双胞模式、异常单胞模式和非定常模式的模式转变。确定了这些模式转变出现的临界轨迹。双胞模式的数值确认是本研究获得的一个不同结果。
