Experimental investigation of the instability of a sedimenting suspension of fibres
Experimental investigation of the instability of a sedimenting suspension of fibres
复制标题
纤维沉降悬浮液不稳定性的实验研究
DOI：
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复制
发表时间：
2007
影响因子：
3.7
通讯作者：
É. Guazzelli
中科院分区：
文献类型：
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作者：
B. Metzger;Jason E. Butler;É. Guazzelli
在雷诺数约为10−4的粘性流体中，对高长径比刚性纤维沉积形成的流动结构的观察证实了先前理论、实验和数值模拟中所报道的不稳定性的存在。利用颗粒图像测速测量产生的数据，我们通过广泛的参数来量化沉积结构，这些参数包括流体的高度、沉降池的横截面、纤维尺寸、流体性质以及从稀到半稀的体积分数。横跨沉降池高度的流带和回流区的交替结构在短时间内形成，并随着沉降的进行从大波长过渡到小波长。在实验中没有观察到水平波长与长度尺度和浓度的简单依赖关系，这表明需要进行额外的分析。我们还报告了平均速度和速度波动；速度波动的强度与沉降结构垂直分量的大小密切相关。利用一种有效的新技术对取向分布进行测量，结果与先前发表的结果一致。该论文的在线版本提供了一部电影。
Observations of the flow structures formed by rigid fibres of high aspect ratio sedimenting within a viscous fluid at a Reynolds number of approximately 10−4 confirm the existence of an instability as reported in previous theories, experiments, and numerical simulations. Using data generated from particle image velocimetry measurements, we quantify the sedimentation structures over a wide range of parameters, which include the height of fluid, cross-section of the sedimentation cell, fibre dimensions, fluid properties, and volume fractions ranging from dilute to semi-dilute. Alternating structures of streamers and backflow regions which span the height of the sedimentation cell form at short times and transition from large wavelengths to smaller wavelength as the sedimentation proceeds. No simple dependence of the horizontal wavelength on the length scales and concentration was observed in the experiments, suggesting the need for additional analysis. We also report the mean velocities and velocity fluctuations; the strength of the velocity fluctuations strongly correlates with the size of the vertical component of the sedimentation structure. Measurements of the orientation distribution, using an efficient and newly employed technique, agree with previously published results. A movie is available with the online version of the paper.