Experiments on Gravity- and Wind-Driven Droplet Stability and Motion on Rough Surfaces

CBET - 0828469白色，爱德华B。 固体表面上的液滴可以保持固定在表面上，由于重力而沿着表面流下，或者由于外部空气流而沿着表面沿着。存在液滴对重力作用的稳定性模型，也存在一些低雷诺数对风作用的稳定性模拟。由于模型验证所需的测量困难和接触角变化，特别是在粗糙表面上，这些模型几乎没有得到实验验证。为了解决这一缺点，已经开发了一种新的测量技术，该技术通过跟踪来自顶视图像的跨液体/气体界面的激光散斑图案的折射来揭示液滴的界面形状和接触角。该技术将确定接触角如何受到常见工程金属上的粗糙度幅度和分布的影响。它还将确定液滴对重力作用的静态稳定性的现有模型的准确性，以及它与风驱动液滴的区别。这些问题正在解决，通过一个系统的程序，测量蒸馏水液滴粗糙的金属表面上，倾斜表面上的液滴和测量风驱动的液滴在倾斜表面上低于临界倾角。液体从表面的润湿和脱落影响从制造过程到飞机结冰的许多技术领域。除了其广泛的技术影响，这项工作将为本科生参与研究提供充足的机会。

CBET - 0828469 White, Edward B. Liquid droplets on solid surfaces can remain fixed to the surface, run down the surface due to gravity or run along the surface due to external air flow. Models exist for droplet stability to gravity forcing as do some low-Reynolds-number simulations of stability to wind forcing. These models have received little experimental validation due to the difficulty of measurements needed for model validation and contact angle variation, particularly on rough surfaces. To address this shortcoming, a new measurement technique has been developed that reveals a droplet's interface shape and contact angles by tracking the refraction of a laser speckle pattern across the liquid/gas interface from top-view images. This technique will determine how contact angles are affected by roughness amplitudes and distributions on common engineering metals. It will also determine the accuracy of existing models of droplets' static stability to gravity forcing and how it differs from wind-driven droplets. These questions are being addressed through a systematic program of measurements of distilled-water droplets on rough metal surfaces, droplets on inclined surfaces and measurements of wind-driven droplets on inclined surfaces just below critical inclination angles. Wetting and shedding of liquids from surfaces affect numerous areas of technology from manufacturing processes to aircraft icing. Beyond its broad technological impacts, the work will provide ample opportunities for undergraduate research participation.