The coating and drying of non-flat discrete objects is a key manufacturing step for a wide variety of products. Flow of a thin, non-volatile liquid film on the outside of a rotating cylinder is commonly used as a model problem to study the coating of discrete objects. However, the behavior of a volatile, particle-laden coating has yet to be studied and remains an important open problem. In this work, we use lubrication theory to study the evolution of a liquid film laden with colloidal particles in the presence of solvent evaporation. Two coupled evolution equations describing variations in coating thickness and composition as a function of time and the angular coordinate are solved numerically. In the limit of a rapidly rotating cylinder, gravitational effects are negligible, and linear stability analysis and nonlinear simulations demonstrate that non-uniform drying at larger drying rates may cause thickness and composition disturbances to re-grow after initially decaying. When gravitational effects are significant, poor liquid redistribution at lower rotation rates and larger drying rates leads to less uniform coatings. Colloidal particles hinder liquid redistribution at high concentrations by increasing the viscosity, but help prevent rupture of the coating at more moderate concentrations. A parametric study reveals that both thickness and composition variations are minimized at large rotation rate, low drying rate, and moderate initial particle concentration.

中文翻译：

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旋转缸同时进行液体流动和干燥

非扁平离散物体的涂层和干燥是多种产品的关键制造步骤。薄的，不挥发的液体薄膜在旋转圆柱体外部的流动通常用作研究离散物体涂层的模型问题。然而，挥发性的，负载颗粒的涂层的性能尚待研究，仍然是一个重要的开放问题。在这项工作中，我们使用润滑理论来研究在溶剂蒸发的情况下充满胶体颗粒的液膜的演变。数值求解了两个耦合的演化方程，这些方程描述了涂层厚度和成分随时间和角度坐标的变化。在快速旋转的圆柱体的极限内，重力影响可以忽略不计，线性稳定性分析和非线性模拟表明，在较大的干燥速率下干燥不均匀可能会导致厚度和成分扰动在最初衰减后重新增长。当重力作用显着时，较低的旋转速度和较大的干燥速度会使液体重新分配变差，导致涂层不均匀。胶体颗粒通过增加粘度来阻止高浓度下的液体重新分布，但有助于防止中等浓度下的涂层破裂。参数研究表明，在大旋转速率，低干燥速率和适度的初始颗粒浓度下，厚度和成分变化均最小。当重力作用显着时，较低的旋转速度和较大的干燥速度会使液体重新分配变差，导致涂层不均匀。胶体颗粒通过增加粘度来阻止高浓度下的液体重新分布，但有助于防止中等浓度下的涂层破裂。参数研究表明，在大旋转速率，低干燥速率和适度的初始颗粒浓度下，厚度和成分变化均最小。当重力作用显着时，较低的旋转速度和较大的干燥速度会使液体重新分配变差，导致涂层不均匀。胶体颗粒通过增加粘度来阻止高浓度下的液体重新分布，但有助于防止中等浓度下的涂层破裂。参数研究表明，在大旋转速率，低干燥速率和适度的初始颗粒浓度下，厚度和成分变化均最小。