Particle Removal from Surfaces using Rinsing Flows with Extensional Viscosity Liquids

Fuller0930100“漂洗流动”是指一种液体烧蚀覆盖在固体基材上的第二层可混溶液体。这一过程在日常经验和许多工业过程中都是常见的，特别是在清洁操作中。这种流动安排伴随着经典的“水力跳跃”现象，但两种粘度不同的液体的分层导致了定性的新结果。这项研究的一个特别感兴趣的是，当液体涂层衬底(被冲洗掉的涂层)是非牛顿时，从固体平面衬底上清除胶体颗粒。提供的初步数据表明，具有大应变增稠拉伸粘度的非牛顿聚合物和表面活性剂溶液非常有效地从平面表面“拔出”吸附的胶体颗粒。然而，这只能通过清洗包含伸展流动梯度的流动来实现。这项研究将利用高速摄影和粒子跟踪来探索漂洗流动的流体力学，它是两种液体(涂层液体和喷射液)粘度比的函数，也是涂层液体流变性的函数。还将直接测量粒子实时去除的动力学。另一个重要的考虑因素是施加漂洗流动的固体基质的疏水性。PI的初步数据表明，衬底的表面能对惯性除湿过程有深刻的影响，本研究将对这一现象进行探讨。美国国家科学基金会以前赞助的研究激发了一系列的倡议，扩大了国际科学基金会学术活动的影响。除了参加大学的REU项目外，在过去的四个夏天里，PI还向当地高中生提供了机会。已向东帕洛阿尔托的东区预备学校和桑尼维尔的哈克学校的学生提供了职位。这项工作是由CBET的流体动力学、颗粒和多相计划共同资助的。

Fuller0930100"Rinsing flows" are where one fluid ablates a layer of a second, miscible liquid that coats a solid substrate. This process is common to everyday experience and to many industrial processes, particularly in cleaning operations. This flow arrangement is accompanied by a classic, "hydraulic jump" phenomenon but the stratification of two liquids, with differing viscosities, leads to qualitatively new results. A particular interest in this study is during the cleaning of colloidal particles from solid, planar substrates when the liquid coating the substrate (the one being rinsed off) is non-Newtonian. Preliminary data are offered that demonstrate that non-Newtonian polymer and surfactant solutions with large strain thickening extensional viscosities very effectively "pluck" adsorbed colloidal particles from planar surfaces. However, this can only be accomplished by rinsing flows that contain extensional flow gradients. This research will explore the fluid mechanics of rinsing flows as a function of the viscosity ratio of the two fluids (the coating liquid and the jet liquid) and as a function of the rheological character of the coating liquids using high-speed photography and particle tracking. The dynamics of particle removal in real time will also be directly measured. Another important consideration is the hydrophobicity of the solid substrates onto which the rinsing flows are applied. The PI's preliminary data demonstrate that the surface energy of the substrates has a profound effect on the process of inertial dewetting and this research will explore this phenomenon. The PI's previous NSF sponsored research has stimulated a number of initiatives that broadened the impact of the PI's scholarly activities. In addition to participating in a REU program at the university, for the past four summers the PI has extended opportunities to local high school students. Positions have been made available to students from Eastside Preparatory School in East Palo Alto and Harker School in Sunnyvale. This work is jointly funded by the Fluid Dynamics and Particulate and Multiphase Programs of CBET.