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Drop deformation and breakup
KTH, Skolan för teknikvetenskap (SCI), Mekanik, Fysiokemisk strömningsmekanik.
KTH, Skolan för teknikvetenskap (SCI), Mekanik, Fysiokemisk strömningsmekanik.ORCID-id: 0000-0003-3336-1462
KTH, Skolan för teknikvetenskap (SCI), Mekanik.ORCID-id: 0000-0001-9976-8316
2014 (engelsk)Inngår i: International Journal of Multiphase Flow, ISSN 0301-9322, E-ISSN 1879-3533, Vol. 66, s. 1-10Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

A Volume of Fluid (VOF) method is applied to investigate the deformation and breakup of an initially spherical drop in the bag- and shear breakup regimes, induced by steady disturbances. The onset of breakup is sought by studying steady-shape deformations while increasing the Weber number until breakup occurs. A parameter study is carried out applying different material properties and a wide range of drop Reynolds numbers in the steady wake regime. Density ratios of liquid to gas of 20, 40, and 80, viscosity ratios in the range 0.5-50, and Reynolds numbers between 20 and 200 are investigated for a constant Weber number of 20. The critical Weber number is found to be 12, in agreement with observations of earlier studies. For Weber number of 20 varying density, viscosity ratios and Reynolds numbers, interesting mixed breakup modes are discovered. Moreover, a new regime map including all modes observed is presented. A criterion for the transition between bag-and shear breakup is defined relating the competing inertial and shear forces appearing in the flow. Furthermore, results on breakup times and the time history of the drag coefficient are presented; the latter is concluded to be a potential parameter to indicate the occurrence of breakup. (C) 2014 Elsevier Ltd. All rights reserved.

sted, utgiver, år, opplag, sider
Elsevier, 2014. Vol. 66, s. 1-10
Emneord [en]
Droplet, Deformation, Breakup, Regime map, Breakup time, Volume of Fluid (VOF)
HSV kategori
Identifikatorer
URN: urn:nbn:se:kth:diva-154737DOI: 10.1016/j.ijmultiphaseflow.2014.06.006ISI: 000342548300001Scopus ID: 2-s2.0-84904904082OAI: oai:DiVA.org:kth-154737DiVA, id: diva2:764505
Forskningsfinansiär
Swedish Research Council
Merknad

QC 20141119. QC 20160113

Tilgjengelig fra: 2014-11-19 Laget: 2014-10-27 Sist oppdatert: 2017-12-05bibliografisk kontrollert
Inngår i avhandling
1. Scenarios of drop deformation and breakup in sprays
Åpne denne publikasjonen i ny fane eller vindu >>Scenarios of drop deformation and breakup in sprays
2017 (engelsk)Doktoravhandling, med artikler (Annet vitenskapelig)
Abstract [en]

Sprays are used in a wide range of engineering applications, in the food and pharmaceutical industry in order to produce certain materials in the desired powder-form, or in internal combustion engines where liquid fuel is injected and atomized in order to obtain the required air/fuel mixture. The optimization of such processes requires the detailed understanding of the breakup of liquid structures.

In this work, we focus on the secondary breakup of medium size liquid drops that are the result of primary breakup at earlier stages of the breakup process, and that are subject to further breakup. The fragmentation of such drops is determined by the competing disruptive (pressure and viscous) and cohesive (surface tension) forces. In order to gain a deeper understanding on the dynamics of the deformation and breakup of such drops, numerical simulations on single drops in uniform and shear flows, and on dual drops in uniform flows are performed employing a Volume of Fluid method. The studied parameter range corresponds to an intermediate Weber number of 20, sufficiently high so that breakup occurs, but much lower than the limit for catastrophic breakup, and a range of Reynolds numbers covering the steady wake regime for liquid drops, Re = 20-200. In order to account for liquids in various applications, a set of different density and viscosity ratios are considered, ρ*=20-80, and μ*=0.5-50 respectively.

Single drop simulations show that depending on the Reynolds number and density and viscosity ratios, various breakup modes besides classical bag and shear breakup may be observed at a constant Weber number. The characteristics of the deformation process and the time required for breakup are considerably different for these modes; furthermore, both are significantly altered by velocity gradients in the flow. Dual drop simulations show that the relative position of the two drops, in addition to the Reynolds number and density and viscosity ratios, plays a crucial role in determining the interaction scenario. It is found that the behaviour of drops in tandem may be predicted based on data obtained for single drops: the breakup time and the length of the wake behind the drop. The region where collision is most likely to occur is identified as a two diameters wide and eight diameters long streak, however, weaker forms of interaction may occur up to twenty diameters behind the drop. Results presented in this thesis may be applied to formulate enhanced breakup models regarding the deformation, breakup, and interaction of liquid drops employed in spray simulations.

sted, utgiver, år, opplag, sider
Stockholm: Kungliga Tekniska högskolan, 2017. s. 60
Serie
TRITA-MEK, ISSN 0348-467X ; 2017:10
HSV kategori
Forskningsprogram
Teknisk mekanik
Identifikatorer
urn:nbn:se:kth:diva-212939 (URN)978-91-7729-500-6 (ISBN)
Disputas
2017-09-15, D3, Lindstedtsvägen 5, Stockholm, 10:15 (engelsk)
Opponent
Veileder
Merknad

QC 20170825

Tilgjengelig fra: 2017-08-25 Laget: 2017-08-24 Sist oppdatert: 2017-11-07bibliografisk kontrollert

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