The videos below report on the entrainment mechanisms that were identified after conducting measurements on a Taylor bubble that was artificially held in the same position, in an attempt to simulate slug flow conditions. Experiments were conducted in a 67mm pipe, where an hemispherical cap was placed in the middle of the test section and connected to a small concentric pipe for the gas flow to occur, which would create an artificial Taylor bubble. Simultaneously, water was induced in the downwards direction in order to simulate the falling film surrounding a Taylor bubble. The downwards liquid flowrate could be controlled [ Read More ]
Open access paper “Kinetics of liquid bridges and formation of satellite droplets:Difference between micellar and bi-layer forming solutions” by Nina Kovalchuk∗, Emilia Nowak and Mark Simmons (Uniersity of Birmingham) is published in Colloids and Surfaces A: Physicochemical and Engineering Aspects. Abstract The process of drop detachment from a capillary tip and formation of satellite droplets is studied for solutions of trisiloxane surfactants above the critical aggregation concentration. Two of the studied surfactants self-assemble in bilayer based phases, whereas the third forms micelles. The difference in the aggregates formed results in an essential difference in the rate of equilibration between the [ Read More ]
This animation shows a reconstructed contours interfacial wave structure in a falling liquid film (from the top to the bottom of the pipe/sensor) using Multi-Pin Film Sensor (MPFS). MPFS comprises of 2 X 5 axial planes x 64 circumferential pin electrodes (i.e. 640 points measurement). Red colour corresponds to the high energy (large wave). Liquid Reynolds number is 1670.
Results on formation of surfactant-laden drops from University of Birmingham have been presented at 30th Conference of The European Colloid and Interface Society ECIS-2016, Rome, 4-9 September 2016. Abstract Effect of soluble surfactants of kinetics of liquid bridges and formation of satellite droplets N Kovalchuk, E Nowak, M.J.H. Simmons School of Chemical Engineering, University of Birmingham, UK Bespoke drop formation is an essential part of many industrial processes such as emulsification, spray drying, inkjet printing and others. Surfactants are often present in the aqueous formulations used in these processes and therefore influence the quality of the final product. In particular [ Read More ]
New article on Physical Review E explaining the effect of surfactants on the neck expansion dynamics and the flow field around the rupture point has been published! Abstract: In this work the coalescence of an aqueous drop with a flat aqueous-organic interface was investigated in a thin gap Hele-Shaw cell. Different concentrations of a nonionic surfactant (Span 80) dissolved in the organic phase were studied. We present experimental results on the velocity field inside a coalescing droplet in the presence of surfactants. The evolution of the neck between the drop and the interface was studied with high-speed imaging. It was found that [ Read More ]
A short presentation summarising the main results of the paper “Effect of Soluble Surfactants on the Kinetics of Thinning of Liquid Bridges during Drops Formation and on Size of Satellite Droplets” by Nina Kovalchuk, Emilia Novak and Mark Simmons recently published in Langmuir is now available as the LiveSlides on Langmuir web-site and is directly connected to this open access paper.
This animation shows the reconstructed interfacial wave structure in a falling liquid film using Multi-Pin Film Sensor (MPFS). MPFS comprises of 2 X 5 axial planes x 64 circumferential pin electrodes (i.e. 640 points measurement). MPFS can provide film thickness data with high temporal and spatial distribution for upward /downward annular flows in time, circumferential and axial coordinates, δ(t,θ,z). The pipe diameter used was 127 mm. The animation shows non-coherent wave structure.