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We study the rebound of drops impacting non-wetting substrates at low Weber number (We) through experiment, direct numerical simulation and reduced-order modelling. Submillimetre-sized drops are normally impacted onto glass slides coated with a thin viscous film that allows them to rebound without contact line formation. Experiments are performed with various drop viscosities, sizes and impact velocities, and we directly measure metrics pertinent to spreading, retraction and rebound using high-speed imaging. We complement experiments with direct numerical simulation and a fully predictive reduced-order model that applies natural geometric and kinematic constraints to simulate the drop shape and dynamics using a spectral method. At low We, drop rebound is characterised by a weaker dependence of the coefficient of restitution on We than in the more commonly studied high-We regime, with nearly We-independent rebound in the inertio-capillary limit, and an increasing contact time as We decreases. Drops with higher viscosity or size interact with the substrate longer, have a lower coefficient of restitution and stop bouncing sooner, in good quantitative agreement with our reduced-order model. In the inertio-capillary limit, low-We rebound has nearly symmetric spreading and retraction phases and a coefficient of restitution near unity. Increasing We or viscosity breaks this symmetry, coinciding with a drop in the coefficient of restitution and an increased dependence on We. Lastly, the maximum drop deformation and spreading are related through energy arguments, providing a comprehensive framework for drop impact and rebound at low We. 

Electrokinetic instabilities in a shear thinning fluid start at a smaller electric field and an earlier location than in a Newtonian fluid but with a smaller wave amplitude and frequency. 

Thin-film flow down a fibre exhibits rich dynamics and is relevant to applications such as desalination, fibre coating and fog harvesting. These flows are subject to instabilities that result in dynamic bead-on-fibre patterns. We perform an experimental study of shear-thinning flow down fibres using 20 different xanthan gum solutions as our working liquid. The bead-on-fibre morphology can be oriented either symmetrically or asymmetrically on the fibre, and this depends upon the surface tension, fibre diameter and liquid rheology, as defined by the Ostwald power-law index. For highly shear-thinning liquids, it is possible for the pattern to be complex and exhibit simultaneously both asymmetric large beads and symmetric small beads in the isolated and convective flow regimes. We quantify the transition between flow regimes and bead dynamics for the asymmetric morphology, and compare with Newtonian flow, as it depends upon the experimental parameters. Finally, the dimensionless bead frequency is shown to scale with the Bond number for all of our experimental data (symmetric and asymmetric). 

The Urban STEM Collaboratory is a five-year project sponsored by the National Science Foundation (NSF) that addresses challenges to student success in STEM disciplines through a multi-institutional collaboration via the University of Memphis (UofM), University of Colorado Denver (CU Denver), and Indiana University--Purdue University Indianapolis (IUPUI). Study groups, tutoring, peer and faculty mentoring, and career exploration programs are being used across the three campuses to increase the participants’ commitment to a STEM field. Innovative features from Course Networking (CN) software are being deployed to provide scholars with evidence of their learning journey while expanding a meaningful academic cloud-based social network. This paper extends a previous introductory ASEE conference paper titled: “Launching the Urban STEM Collaboratory,” (Goodman et al., 2020), which outlined the initial efforts of the tri-campus collaboration. The purpose of the present paper is to summarize the impact of the project, including data analysis of effectiveness, for Year 1: 2019-2020 and Year 2: 2020-2021. Although still in progress, with the longitudinal efficacy of several of the project’s components undetermined, the project’s organizational structure, activities, and findings to date should be of value to others conducting or proposing projects with similar goals. 

The Urban STEM Collaboratory is a five-year project sponsored by the National Science Foundation (NSF) that addresses challenges to student success in STEM disciplines through a multi-institutional collaboration via the University of Memphis (UofM), University of Colorado Denver (CU Denver), and Indiana University--Purdue University Indianapolis (IUPUI). Study groups, tutoring, peer and faculty mentoring, and career exploration programs are being used across the three campuses to increase the participants’ commitment to a STEM field. Innovative features from Course Networking (CN) software are being deployed to provide scholars with evidence of their learning journey while expanding a meaningful academic cloud-based social network. This paper extends a previous introductory ASEE conference paper titled: “Launching the Urban STEM Collaboratory,” (Goodman et al., 2020), which outlined the initial efforts of the tri-campus collaboration. The purpose of the present paper is to summarize the impact of the project, including data analysis of effectiveness, for Year 1: 2019-2020 and Year 2: 2020-2021. Although still in progress, with the longitudinal efficacy of several of the project’s components undetermined, the project’s organizational structure, activities, and findings to date should be of value to others conducting or proposing projects with similar goals.