Experimental investigation of hysteresis in the break-up of liquid curtains
Thoroddsen, Sigurdur T
Thompson, John W.
Blyth, Mark G.
KAUST DepartmentPhysical Sciences and Engineering (PSE) Division
Mechanical Engineering Program
High-Speed Fluids Imaging Laboratory
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AbstractFindings from an experimental investigation of the break-up of liquid curtains are reported, with the overall aim of examining stability windows for multi-layer liquid curtains composed of Newtonian fluids, where the properties of each layer can be kept constant or varied. For a single-layer curtain it is known that the minimum flow rate required for initial stability can be violated by carefully reducing the flow rate below this point, which defines a hysteresis region. However, when two or three layers are used to form a composite curtain, the hysteresis window can be considerably reduced depending on the experimental procedure used. Extensive quantitative measurements of this hysteresis region are provided alongside an examination of the influence of physical properties such as viscosity and surface tension. The origins of curtain break-up for two different geometries are analysed; first where the curtain width remains constant, pinned by straight edge guides; and second where the curtain is tapered by angled edge guides. For both cases, the rupture speed is measured, which appears to be consistent with the Taylor-Culick velocity. Observations of the typical linearly spaced jets which form after the break-up has transpired and the periodicity of these jets are compared to the Rayleigh-Taylor wavelength and previous experimental measurements. Furthermore, the curtain stability criterion originally developed by Brown (1961), summarised in terms of a Weber number, has recently been extended to multi-layer curtains by Dyson et al. (2009); thus this report provides the first experimental measurements which puts this to the test. Ultimately, it is found that only the most viscous and polymer-based liquids violate this criterion. © 2014 Elsevier Ltd.
SponsorsThis work was partially supported by an Academic Excellence Alliance grant awarded by the KAUST office of Competitive Research Funds number 7000000028. The experimental work was conducted while J.T. and D.H. were on research visits at KAUST. We thank the Analytical Core Laboratory and Sahraoui Chaieb at KAUST for assistance with characterisation of the fluid physical properties. We also thank Thomas Ramel and Maick Nielsen from TSE Troller AG for technical advice and guidance for certain aspects of the experimental work.
JournalChemical Engineering Science