Surface velocity in three-dimensional granular tumblers
Surface velocity in three-dimensional granular tumblers
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DOI：
10.1017/s0022112006000437
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发表时间：
2006-07
影响因子：
3.7
通讯作者：
N. Pohlman;S. W. Meier;Richard M. Lueptow;J. Ottino
中科院分区：
文献类型：
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作者：
N. Pohlman;S. W. Meier;Richard M. Lueptow;J. Ottino
颗粒流的一个基本特征是它们通常局限于快速表面流动的薄层。因此，对表面流动的完整理解是准确表示整个流动动力学的关键。实验在三维玻璃杯中进行：不同直径的圆柱形玻璃杯、双锥玻璃杯和球形玻璃杯，后两者的弗劳德数是局部几何的函数，范围从$2.6\times10^{-5}$到$7.5\times10^{-4}$。采用颗粒跟踪测速法测量了1 mm和2 mm玻璃颗粒的表面速度。结果表明，与翻滚体形状、颗粒大小、旋转速率和填充率无关，流动层中点的顺流表面速度与局部流动层长度成线性关系。此外，粒子在自由表面的轴向速度可以忽略不计。这些结果对颗粒流动三维模型的发展至关重要。
A fundamental characteristic of granular flows is that they are typically restricted to thin layers of rapid surface flow. Thus, a complete understanding of surface flows is key for an accurate representation of the dynamics of the entire flow. Experiments were conducted in three-dimensional tumblers: cylindrical tumblers of various diameters, a double-cone tumbler, and a spherical tumbler, the Froude number for the last two being a function of the local geometry and ranging from $2.6\times10^{-5}$ to $7.5\times10^{-4}$. Surface velocity measurements for 1 mm and 2 mm glass particles were obtained using particle tracking velocimetry. Results indicate that the streamwise surface velocity at the midpoint of the flowing layer is a linear function of local flowing layer length, regardless of tumbler shape, particle size, rotation rate, and fill fraction. In addition, the axial velocity of particles at the free surface is negligible. These results are key for the development of three-dimensional models of granular flows.