The goal of the proposed research is to explore the wetting and drainage of thin layers of liquid from curved surfaces. This largely experimental program will provide simultaneous measurements of the layer thicknesses of an upper, less dense liquid draining atop a second, more dense liquid that is also undergoing drainage. An example of such a system is an oil and water system that drains from a curved surface. An important event that occurring in the environment involving the drainage and dewetting of stratified liquid films is the interaction of oil slicks at the surface of water with aquatic life. It is important to understand this example since the coating of water-based plants, birds, mammals and fish is an unfortunate result of such spillage. In terms of education and outreach, the PI will develop and disseminate teaching modules that upgrade and complement existing core chemical engineering classes by covering new developments and challenges in fluid mechanics and interface science.
The drainage and dewetting of stratified liquid layers from curved surfaces (e.g., hemispheres will be examined) is expected to be strongly affected by the viscosity ratio of the two liquids. It is expected that the drainage dynamics will undergo a number of transitions, depending on the viscosity ratio. For example, in the limit that the upper liquid becomes much more viscous, its drainage will transition from a Reynolds draining response where the thinning of the upper film decreases algebraically to an exponential decay. The experiments proposed are designed to measure the morphology of the resulting surface coverage patterns when drainage has proceeded to sufficiently long times. That is when dewetting of the curved substrate will ensue. The project will examine these processes as a function of the viscosity ratio of the two immiscible liquids and the surface energy of the substrate. In addition, the influence of interfacial viscoelasticity of the liquid/liquid interface will be examined.
