Spectral study of the laminar—turbulent transition in spherical Couette flow
Spectral study of the laminar—turbulent transition in spherical Couette flow
复制标题
球形库埃特流层流-湍流转变的光谱研究
DOI：
10.1017/s0022112088002915
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发表时间：
1988
影响因子：
3.7
通讯作者：
Yoichi Tsuchida
中科院分区：
文献类型：
--
作者：
K. Nakabayashi;Yoichi Tsuchida
内球旋转时两同心球间隙中Taylor-Görtler（TG）涡的层流-湍流转变在间隙与内球半径之比相对较小的情况下，通过测量用于流动显示的铝片的散射光强度，通过速度测量和同时的光谱和流动显示测量来研究球形Couette流（间隙比β = 0.14）。用恒温热线风速仪在两个不同的纬线（子午线角）θ（θ = 80°和90°（赤道））上测量了方位角速度分量。通过光谱和流动显示同时测量，获得了临界雷诺数、一些过渡雷诺数、流态和流动状态。流动状态用环形TG涡胞数N、螺旋TG涡对数Sp、环形TG涡上的方位波传播波数m和剪切波波数SH表示。计算了脉动流场的平均流速分布和脉动流场的自相关系数、功率谱和湍流度等特征量。值），被认为是在很大的范围内的雷诺数Re。通过速度测量、频谱测量和流动显示测量，发现了三种速度脉动的基频，并阐明了它们的特性。用fS、fW和fH表示的三种基频分别对应于螺旋形TG涡旋、行进方位波和剪切波。这些基频与θ和壁距内球的距离无关，但强烈依赖于Re。虽然方位波的旋转频率在圆形Couette流中，螺旋TG涡的旋转频率（或波速）随雷诺数的增加而单调减小，直到达到一个平台，球形Couette流中的螺旋TG涡的旋转频率、方位行波和剪切波的旋转频率fS/SP、fW/m和fH/SH随雷诺数的增加几乎不变，彼此之间有细微的差别。
The laminar—turbulent transition of the Taylor—Görtler (TG) vortex flow in the clearance between two concentric spheres with only the inner sphere rotating (spherical Couette flow) is investigated by velocity measurement and simultaneous spectral and flow-visualization measurements by measuring the intensity of light scattered by the aluminium flakes used in flow visualization in the case of a relatively small ratio of the clearance to inner-sphere radius (clearance ratio β = 0.14). An azimuthal velocity component has been measured by a constant-temperature hotwire anemometer at two different colatitudes (meridian angles) θ; θ = 80° and 90° (the equator). A critical Reynolds number, some transition Reynolds numbers, flow regimes and flow states are obtained by the simultaneous spectral and flow-visualization measurements. The flow state is expressed by the number of toroidal TG vortex cells N, that of spiral TG vortex pairs Sp, the wavenumber of the travelling azimuthal waves on the toroidal TG vortices m and the wavenumber of shear waves SH. The mean velocity distribution and the characteristic values of the fluctuating velocity, such as autocorrelation coefficient, power spectrum and turbulence intensity (r.m.s. value), are considered over a great range of Reynolds number Re. Three kinds of fundamental frequencies of the velocity fluctuation are discovered and their characteristics are clarified by means of the velocity measurement and the simultaneous spectral and flow-visualization measurements. The three kinds of fundamental frequencies expressed by fS, fW and fH correspond to the spiral TG vortices, the travelling azimuthal waves and the shear waves, respectively. These fundamental frequencies are independent of both θ and wall distances from the inner sphere, but depend strongly on Re. Although the rotation frequency of the travelling azimuthal waves (or wave speed) in the circular Couette flow decreases monotonically with increasing Reynolds number until it reaches a plateau, the values of the rotation frequencies of the spiral TG vortices, the travelling azimuthal waves and the shear waves in the spherical Couette flow, fS/SP, fW/m and fH/SH, are nearly constant as the Reynolds number is increased, and differ slightly from one another.