Effect of particle size ratio on shear-induced onset of particle motion at low particle Reynolds numbers: From high shielding to roughness
Effect of particle size ratio on shear-induced onset of particle motion at low particle Reynolds numbers: From high shielding to roughness
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DOI：
10.1063/1.5108800
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发表时间：
2019-06
影响因子：
4.6
通讯作者：
N. Topic;S. Retzepoglu;M. Wensing;C. Illigmann;G. Luzi;J. R. Agudo;A. Wierschem
中科院分区：
文献类型：
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作者：
N. Topic;S. Retzepoglu;M. Wensing;C. Illigmann;G. Luzi;J. R. Agudo;A. Wierschem
本文研究了小颗粒雷诺数条件下，在稳定剪切流中，不同粒径的球形颗粒在规则基底上的单珠初始运动。我们涵盖了大范围的尺寸：从被基底球体高度屏蔽而不受剪切流影响的小珠，因此，容易受到通过基底间隙的流动的影响，到完全暴露于流动的珠，其中基底的作用类似于平坦表面的粗糙度。数值和实验研究在测量不确定度范围内一致。为了描述这些发现，我们扩展了一个最近推导出的相同尺寸颗粒的模型，该模型在广泛的基质上得到了验证[Agudo等人，“在低颗粒雷诺数下均匀基底上单个球体的剪切诱导初始运动”，J. Fluid Mech. 825，284-314（2017）]。扩展模型涵盖了整个谱的大小比，其中临界希尔兹数从零到无穷大不等。该模型正确地描述了数值和实验数据。对于暴露较好的小球，发现临界Shields数与移动的小球与基底小球的尺寸比之间存在一个指数为− 1的标度关系.我们涵盖了大范围的尺寸：从被基底球体高度屏蔽而不受剪切流影响的小珠，因此，容易受到通过基底间隙的流动的影响，到完全暴露于流动的珠，其中基底的作用类似于平坦表面的粗糙度。数值和实验研究在测量不确定度范围内一致。为了描述这些发现，我们扩展了一个最近推导出的相同尺寸颗粒的模型，该模型在广泛的基质上得到了验证[Agudo等人，“在低颗粒雷诺数下均匀基底上单个球体的剪切诱导初始运动”，J. Fluid Mech. 825，284-314（2017）]。扩展模型涵盖了整个谱的大小比，其中临界希尔兹数从零到无穷大不等。该模型正确地描述了T…
We study incipient motion of single beads on regular substrates made of spherical particles of a different size in steady shear flow at small particle Reynolds numbers. We cover a large range of sizes: from small beads that are highly shielded from the shear flow by the substrate spheres, and hence, are susceptible to the flow through the interstices of the substrate, to beads fully exposed to the flow, where the substrate rather acts like roughness of an otherwise flat surface. Numerical and experimental studies agree within measurement uncertainty. To describe the findings, we extend a recently derived model for particles of equal size which was validated over a wide range of substrates [Agudo et al., “Shear-induced incipient motion of a single sphere on uniform substrates at low particle Reynolds numbers,” J. Fluid Mech. 825, 284–314 (2017)]. The extended model covers the entire spectrum of size ratios, where the critical Shields number varies from about zero to infinity. The model properly describes the numerical and experimental data. For well exposed beads, we find a scaling law between the critical Shields number and the size ratio between mobile bead and substrate spheres with an exponent of −1.We study incipient motion of single beads on regular substrates made of spherical particles of a different size in steady shear flow at small particle Reynolds numbers. We cover a large range of sizes: from small beads that are highly shielded from the shear flow by the substrate spheres, and hence, are susceptible to the flow through the interstices of the substrate, to beads fully exposed to the flow, where the substrate rather acts like roughness of an otherwise flat surface. Numerical and experimental studies agree within measurement uncertainty. To describe the findings, we extend a recently derived model for particles of equal size which was validated over a wide range of substrates [Agudo et al., “Shear-induced incipient motion of a single sphere on uniform substrates at low particle Reynolds numbers,” J. Fluid Mech. 825, 284–314 (2017)]. The extended model covers the entire spectrum of size ratios, where the critical Shields number varies from about zero to infinity. The model properly describes t...