CBET-EPSRC: Dynamic Wetting & Interfacial Transitions in Three Dimensions: Theory vs Experiment

University Of Minnesota-Twin Cities, Minneapolis MN

Investigators

Abstract

This project was awarded through the "Special Guidelines for Submitting Collaborative Proposals under the Division of Chemical, Bioengineering, Environmental, and Transport Systems, the Division of Civil, Mechanical and Manufacturing Innovation, and the Division of Electrical, Communications and Cyber Systems - the UK Engineering and Physical Sciences Research Council (ENG-EPSRC) Lead Agency Activity" opportunity. The maximum speed at which a liquid can spread stably over a solid surface is the key factor to determining the outcomes of numerous natural and technological processes. The instability that emerges when this maximum speed of dynamic wetting is exceeded creates complex three-dimensional flows that are typically undesirable. For example, undesirable air bubbles can be entrained into the liquid while applying a coating, severely limiting the rate of manufacture of a wide range of products. Improved understanding of this instability is essential for developing strategies to increase the maximum speed of dynamic wetting, which will benefit many practical applications. This project uses a combination of experimental analysis and computational modelling to significantly advance fundamental understanding of the complex three-dimensional flows that arise when the maximum speed of dynamic wetting is exceeded. User-friendly software will be developed that others can apply to understand numerous other problems involving dynamic wetting that arise in areas such as climate science. The proposed research at the University of Minnesota-Twin Cities, in collaboration with researchers at the University of Warwick, will make significant progress in resolving longstanding issues in the area of dynamic wetting by (i) development of a user-friendly multiscale computational framework capable of capturing 3D phenomena, (ii) use of both analysis and computational modelling to characterize and understand the stability of dynamic wetting lines, and (iii) use of both computational capabilities and experimental investigations to characterize and understand interfacial instabilities governing the dynamics of droplets. The key advance of the computational modeling will be the development of a dynamic mesh generation capability for finite-element methods that can accurately resolve three-dimensional time-dependent flows. The experiments will be conducted in a custom-made coating apparatus, and will involve measurements of the maximum speed of dynamic wetting and instability wavelength by flow visualization, as well as measurements of the thickness of entrained air films by interferometry. The knowledge generated from this project is expected to stimulate new directions of fundamental research and to benefit numerous natural and technological processes in which dynamic wetting plays a key role. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.