Drag force on a sphere in steady motion through a yield-stress fluid
Drag force on a sphere in steady motion through a yield-stress fluid
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DOI：
10.1122/1.2401614
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发表时间：
2007-01-01
影响因子：
3.3
通讯作者：
de Bruyn, John R.
中科院分区：
文献类型：
--
作者：
Tabuteau, Herve;Coussot, Philippe;de Bruyn, John R.
我们已经研究了球体通过屈服应力卡波波尔凝胶下落的运动。我们测量了下落球体的速度作为时间和球体密度的函数。实验流体经过精心制备和均质处理后，得到了可重复的结果。观察到三种运动状态。密度足够高的球体达到恒定的终端速度，如牛顿流体。低于临界密度时，球体完全停止，而在中间状态下，球体继续运动，但速度随时间稳步下降。我们还仔细地描述了流体的神学行为。在不同的施加应力水平下，观察到的下落球体的流动状态与在蠕变试验中观察到的流动状态相似。从我们的数据中获得的屈服准则和球体上的阻力与Beris等人的长期但先前未经证实的理论预测非常一致。
We have studied the motion of spheres falling through yield-stress Carbopol gels. We measured the velocity of the falling sphere as a function of time and sphere density. Reproducible results were obtained when the experimental fluids were carefully prepared and homogenized. Three regimes of motion were observed. Spheres of high enough density reached a constant terminal velocity, as in Newtonian fluids. Below a critical density, the sphere came to a complete stop, while in an intermediate regime, the sphere continued to move but with a velocity which steadily decreased with time. We have also carefully characterized the theological behavior of the fluids. The flow regimes observed for the falling sphere are analogous to those observed in creep tests for different applied stress levels. The yielding criterion and the drag force on the sphere obtained from our data are in excellent agreement with the longstanding but previously unconfirmed theoretical predictions of Beris et al.