摘要
圆Ｃｏｕｅｔｅ系统已成为研究从层流转捩为湍流以及有限几何尺寸对图案选择影响的范例．本文以实验和计算机模拟方法研究中等半径比圆Ｃｏｕｅｔｅ系统的稳定性．考察同轴独立旋转圆筒之间的粘性不可压缩流体运动，推广了经典的Ｒａｙｌｅｉｇｈ离心不稳定性理论，导出稳定性判据，用来定量地确定稳定界限．实验采用了流动显示和激光散射技术．仪器有半径比η＝０６９９，形状比Γ＝１８．流动状态相图中的显著特征是新的首次失稳态：当外筒静止或反向旋转时，首次失稳出现具有非零方位角波数的螺旋涡流，在轴向和方位角方向为行进波，而并非与时间无关的Ｔａｙｌｏｒ涡．初步实验所得的转捩Ｒｅｙｎｏｌｄｓ数与数值计算结果一致．实验室和数值实验显示出半径比对图案形成和转捩序列的影响．
AbstractCircular Couette System has served as a paradigm for studying complex transitions to turbulence,the influence of finite geometry on pattern selection mechanisms.In this paper stability of a circular Couette system with the intermediate radius ratio is investigated through laboratory experiments and computer simulation.The classical Rayleigh centrifugal instability theory is extended to general viscous,incompressible fluid between concentric independently rotating cylinders.A criterion of stability is formulated to quantitatively determine the stability boundary.The laboratory experiments employ the techniques of the laser light scattering and the flow visualization.The apparatus has a radius ratio of η=0699 and an aspect ratio of Γ=18.A striking feature in phase diagram of flow states is the novel primary instability:when the outer cylinder is at rest,or counterrotating,instability occurs first for nonzero azimuthal wave number.Instead of time independent Taylor vortex flow,the resulting flow is spiral vortices which are traveling waves in both the axial and azimuthal directions.Preliminary experimental measurements of transition Reynolds numbers presented here are in agreement with those obtained numerically.Laboratory and numerical experiments have revealed the effects of radius ratio on pattern formation,the sequence of transitions.
出处
《物理学报》
SCIE
EI
CAS
CSCD
北大核心
1998年第10期1658-1664,共7页
Acta Physica Sinica
基金
国家基础研究"攀登计划"
国家自然科学基金
