eprintid: 1472968 rev_number: 24 eprint_status: archive userid: 608 dir: disk0/01/47/29/68 datestamp: 2015-12-04 15:34:55 lastmod: 2021-10-18 00:11:07 status_changed: 2015-12-04 15:34:55 type: article metadata_visibility: show creators_name: Chinaud, M creators_name: Roumpea, E-P creators_name: Angeli, P title: Studies of plug formation in microchannel liquid-liquid flows using advanced particle image velocimetry techniques ispublished: pub divisions: UCL divisions: B04 divisions: C05 divisions: F43 keywords: Liquid-liquid, Plug flow, Microchannels, Micro-PIV, Bright field PIV note: © 2015 The Authors. Published by Elsevier Inc. This is an open access article under the CC BY license (http:// creativecommons.org/licenses/by/4.0/). abstract: Two complementary micro Particle Image Velocimetry (μPIV) techniques have been developed in this work to study plug formation at a microchannel inlet during the flow of two immiscible liquids. Experiments were conducted for different fluid flow rate combinations in a T-junction, where all branches had internal diameters equal to 200 μm. The dispersed phase was a water/glycerol solution and was injected from the side branch of the junction, while the continuous phase was silicon oil and was injected along the main channel axis. In the two-colour μPIV technique two laser wavelengths are used to illuminate two different tracer particles, one in each fluid, and phase averaged velocity profiles can be obtained in both phases simultaneously. In the high speed bright field μPIV technique, a backlight illuminates the test section, where the dispersed phase plug is seeded with tracer particles. This approach allows velocity profiles of the forming dispersed plugs to be followed in time. Non-dimensional plug lengths were found to vary linearly with the aqueous to organic phase flow rate ratio, in agreement with a well-known scaling correlation. The flowrate ratio also affected the velocity profiles within the forming plugs. In particular, for a ratio equal to one, a vortex appears at the tip of the plug in the early stages of plug formation. The interface curvature at the rear of the forming plug changes sign at the later stages of plug formation and accelerates the thinning of the meniscus leading to plug breakage. The spatially resolved velocity fields obtained in both phases with the two-colour PIV show that the continuous phase resists the flow of the dispersed phase into the main channel at the rear of the plug meniscus and causes the change in the interface curvature. This change of interface curvature was accompanied by an increase in vorticity inside the dispersed phase during plug formation. date: 2015-12-01 date_type: published official_url: http://dx.doi.org/10.1016/j.expthermflusci.2015.07.022 oa_status: green full_text_type: pub language: eng primo: open primo_central: open_green verified: verified_manual elements_id: 1051675 doi: 10.1016/j.expthermflusci.2015.07.022 lyricists_name: Angeli, Panagiota lyricists_name: Chinaud, Maxime lyricists_name: Roumpea, Evangelia lyricists_id: PANGE44 lyricists_id: MCHIN69 lyricists_id: EROUM36 actors_name: Chinaud, Maxime actors_name: Barczynska, Patrycja actors_id: MCHIN69 actors_id: PBARC91 actors_role: owner actors_role: impersonator full_text_status: public publication: EXPERIMENTAL THERMAL AND FLUID SCIENCE volume: 69 pagerange: 99-110 issn: 0894-1777 citation: Chinaud, M; Roumpea, E-P; Angeli, P; (2015) Studies of plug formation in microchannel liquid-liquid flows using advanced particle image velocimetry techniques. EXPERIMENTAL THERMAL AND FLUID SCIENCE , 69 pp. 99-110. 10.1016/j.expthermflusci.2015.07.022 <https://doi.org/10.1016/j.expthermflusci.2015.07.022>. Green open access document_url: https://discovery.ucl.ac.uk/id/eprint/1472968/1/1-s2.0-S0894177715001995-main.pdf