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Impact of the adhesion-force lever-arm “a” on the Rock ‘n’ Roll resuspension model and how to compute it from contact mechanics
Journal of Aerosol Science ( IF 3.9 ) Pub Date : 2020-05-01 , DOI: 10.1016/j.jaerosci.2020.105525
Sara Brambilla , Michael J. Brown

Abstract The paper proposes a methodology to fill a gap in the context of mechanistic particle resuspension models related to the adhesion and lift force lever arms ( a ): to date, only one experimental observation exists from a centrifuge experiment with a specific particle/surface pair which found r P / a = 100 and assumed that the contact points were symmetric with respect to the particle center (Reeks, M.W., & D. Hall (2001) Kinetic Models for Particle Resuspension in Turbulent Flows: Theory and Measurement. Aerosol Science, 32, 1–31). However, the Reeks and Hall’s (2001) model is highly sensitive to this parameter, which therefore cannot be used as-is for different particle diameters or materials. This paper proposes a methodology to compute the adhesion and lift force lever arms ( a A and a L , respectively) based on Atomic Force Microcopy (AFM) surface roughness measurements and contact mechanics arguments. In practice, a spherical, perfectly smooth particle is brought in contact (computationally) with the measured surface roughness and is then rotated by the point of contact to determine the two or more asperities over which the particle would sit on the surface. A method to compute the asperity radius of curvature is devised to compute the asperity deformation and the correct partitioning of the total deformation between the particle and the asperity is presented. For the glass surface under consideration, the asperity deformation was negligible, i.e., it was below the van der Waals radius, which is the limit of applicability of contact mechanics. The Reeks and Hall’s (2001) model is then extended to account for the joint probability of a A and a L . Significant differences in particle resuspended after a day in common atmospheric conditions are found between the approach that uses the lever-arm distributions or their mean values. Also, important differences are found when comparing the lever-arm distribution and r P / a = 100. Hence, one should be cautious of using r P / a = 100 for surface/particle pairs differing from those in the original study. Limits of applicability of the theories used are presented together with considerations regarding how to extend the method to non-spherical particles and different materials.

中文翻译:

粘附力杠杆臂“a”对 Rock 'n' Roll 再悬浮模型的影响以及如何从接触力学计算它

摘要 本文提出了一种方法来填补与粘附力和升力杠杆臂 ( a ) 相关的机械粒子再悬浮模型背景下的空白:迄今为止,只有一个实验观察来自具有特定粒子/表面对的离心机实验。发现 r P / a = 100 并假设接触点相对于粒子中心对称(Reeks, MW, & D. Hall (2001) Kinetic Models for Particle Resuspension in Turbulent Flows: Theory and Measurement. Aerosol Science, 32, 1–31)。然而,Reeks 和 Hall (2001) 的模型对该参数高度敏感,因此不能按原样用于不同的粒径或材料。本文提出了一种计算附着力和提升力杠杆臂(a A 和 a L ,分别)基于原子力显微镜(AFM)表面粗糙度测量和接触力学参数。在实践中,将一个完美光滑的球形颗粒与测量的表面粗糙度接触(计算上),然后通过接触点旋转以确定颗粒将位于表面上的两个或多个凹凸不平。设计了一种计算粗糙曲率半径的方法来计算粗糙变形,并提出了粒子与粗糙之间总变形的正确划分。对于所考虑的玻璃表面,粗糙变形可以忽略不计,即低于范德华半径,这是接触力学适用性的极限。然后将 Reeks 和 Hall (2001) 的模型扩展到考虑 A 和 L 的联合概率。在使用杠杆臂分布或其平均值的方法之间发现在普通大气条件下一天后重新悬浮的颗粒的显着差异。此外,在比较杠杆臂分布和 r P / a = 100 时发现了重要差异。因此,对于与原始研究中不同的表面/粒子对,应谨慎使用 r P / a = 100。所使用的理论的适用性限制与有关如何将方法扩展到非球形颗粒和不同材料的考虑一起提出。在使用杠杆臂分布或其平均值的方法之间发现在普通大气条件下一天后重新悬浮的颗粒的显着差异。此外,在比较杠杆臂分布和 r P / a = 100 时发现了重要差异。因此,对于与原始研究中不同的表面/粒子对,应谨慎使用 r P / a = 100。所使用的理论的适用性限制与有关如何将方法扩展到非球形颗粒和不同材料的考虑一起提出。在使用杠杆臂分布或其平均值的方法之间发现在普通大气条件下一天后重新悬浮的颗粒的显着差异。此外,在比较杠杆臂分布和 r P / a = 100 时发现了重要差异。因此,对于与原始研究中不同的表面/粒子对,应谨慎使用 r P / a = 100。所使用的理论的适用性限制与有关如何将方法扩展到非球形颗粒和不同材料的考虑一起提出。
更新日期:2020-05-01
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