Journal of Fluid Mechanics Webinar Series : Zijing Ding, China and Mazi Jalaal, Netherlands
- Date
- Friday 7 May 2021, 4:00pm BST/11am EST
- Location
- Zoom
- External URL
- https://www.cambridge.org/core/journals/journal-of-fluid-mechanics/fluid-mechanics-webinar-series
- Category
- JFM Webinar Series
Speaker: Zijing Ding, Harbin Institute of Technology, China
Date/Time: Friday 7th May 2021 4:00pm BST/11am EST
Title: Coating Liquid Films down a Vertical Fibre
Abstract: Previous experimental study by Kliakhandler et al. (JFM 429:381-390, 2001) reported three different flow patterns of a liquid film flowing down a vertical cylinder. The film flow is unstable due to the famous Plateau-Rayleigh mechanism, which evolves into organised droplets flow patterns. When the flow rate is high, steady moving droplets separated by a long-thin film were observed. When the flow rate is reduced, necklace-like flow structure was seen. When the flow rate is very small, droplets of multi-scales were observed and complex dynamical interactions between these droplets cause an unsteady flow. However, no previous theoretical model correctly predicted the droplet dynamics in the three regimes. In this talk, I will discuss the reasons accounting for poor predictions of liquid film dynamics down a vertical fibre. Then, we solve the Navier-Stokes problem and our results show excellent agreements with the experimental data by Kliakhandler et al.
Enjoy free access to papers in support of Ding's webinar, courtesy of the Journal of Fluid Mechanics.
Speaker: Mazi Jalaal, University of Amsterdam, Netherlands
Date/Time: Friday 7th May 2021 4:30pm BST/11:30am EST
Title: Droplets of Yield Stress Fluids
Abstract: The impact and spreading of droplets of complex fluids over surfaces occur in a variety of industrial applications. We will study the spreading of viscoplastic droplets under surface tension and gravity. The droplet converges to a final equilibrium shape once the driving stresses inside the droplet fall below the yield stress. Scaling laws are presented for the final radius and complemented with an asymptotic analysis for shallow droplets. Moreover, numerical simulations using the volume-of-fluid method and a regularized constitutive law and experiments with an aqueous solution of Carbopol are presented. In the end, we briefly present the other applications of droplets of yield stress fluids.