Altman Lauren E, Hollingsworth Andrew D, Grier David G
Department of Physics and Center for Soft Matter Research, New York University, New York, New York 10003, USA.
Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.
Phys Rev E. 2023 Sep;108(3-1):034609. doi: 10.1103/PhysRevE.108.034609.
Shear flows cause aspherical colloidal particles to tumble so that their orientations trace out complex trajectories known as Jeffery orbits. The Jeffery orbit of a prolate ellipsoid is predicted to align the particle's principal axis preferentially in the plane transverse to the axis of shear. Holographic microscopy measurements reveal instead that colloidal ellipsoids' trajectories in Poiseuille flows strongly favor an orientation inclined by roughly π/8 relative to this plane. This anomalous observation is consistent with at least two previous reports of colloidal rods and dimers of colloidal spheres in Poiseuille flow and therefore appears to be a generic, yet unexplained feature of colloidal transport at low Reynolds numbers.
剪切流会使非球形胶体颗粒翻滚，从而使其取向描绘出被称为杰弗里轨道的复杂轨迹。对于一个长椭球体，其杰弗里轨道预计会使颗粒的主轴优先排列在垂直于剪切轴的平面内。然而，全息显微镜测量结果显示，在泊肃叶流中，胶体椭球体的轨迹强烈倾向于相对于该平面倾斜约π/8的取向。这一异常观测结果与之前至少两篇关于泊肃叶流中胶体棒和胶体球二聚体的报道一致，因此似乎是低雷诺数下胶体输运的一个普遍但尚未得到解释的特征。
