Chesters, AK Allen

Meijer, HEH

Stegeman, YW Yvonne

Vosse, FN Frans  van de

Stegeman, Y.W.

Vosse, van de, F.N.

Chesters, A.K.

Meijer, H.E.H.

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 Break up of droplets in time-dependent flowCitation for published version (APA):Stegeman, Y. W., Vosse, van de, F. N., Chesters, A. K., & Meijer, H. E. H. (1998). Break up of droplets in time-dependent flow. Poster session presented at Mate Poster Award 1998 : 3rd Annual Poster Contest.Document status and date:Published: 01/01/1998Document Version:Accepted manuscript including changes made at the peer-review stagePlease check the document version of this publication:• A submitted manuscript is the version of the article upon submission and before peer-review. There can beimportant differences between the submitted version and the official published version of record. Peopleinterested in the research are advised to contact the author for the final version of the publication, or visit theDOI to the publisher's website.• The final author version and the galley proof are versions of the publication after peer review.• The final published version features the final layout of the paper including the volume, issue and pagenumbers.Link to publicationGeneral rightsCopyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright ownersand it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.            • Users may download and print one copy of any publication from the public portal for the purpose of private study or research.            • You may not further distribute the material or use it for any profit-making activity or commercial gain            • You may freely distribute the URL identifying the publication in the public portal.If the publication is distributed under the terms of Article 25fa of the Dutch Copyright Act, indicated by the “Taverne” license above, pleasefollow below link for the End User Agreement:www.tue.nl/taverneTake down policyIf you believe that this document breaches copyright please contact us at:openaccess@tue.nlproviding details and we will investigate your claim.Download date: 17. Nov. 2023Break up of droplets in time-dependent flowY.W. Stegeman, F.N. vd Vosse, A.K. Chesters and H.E.H. MeijerEindhoven University of Technology,Faculty of Mechanical Engineering,Section Materials Technology,P.O. Box 513, NL 5600 MB EindhovenIntroductionProperties of blends depend largely on the micro-structure, which is the result of break up andcoalescence during processing. The objective ofthe present study is to determine the effect of time-dependent flow conditions and visco-elastic behavioron the deformation and break up of droplets.Experimental MethodsA single Newtonian or visco-elastic droplet issubjected to a Newtonian hyperbolic flow, usingan opposed jets device, as shown in figure 1..γCBADMicroscopewith cameraHomogeneousilluminationDroppositioncontrolPositionPump speed PumpReservoirT′Timeε̇Determination critical capillary number Ca= ε̇ηcR/σThe elongation rate ε̇ is slowly increased, withtime interval T′ much larger than the characteristicdrop deformation time ηcR/σ. Here ηc denotes thecontinuous phase viscosity, R the drop radius and σthe interfacial tension.Timeε̇ε̇c1ε̇1TTriangular strain rate - time profilefig. 1 Experimental setup and strain rate profiles appliedIn quasi steady flow, the critical capillary number isdetermined, which defines the critical elongation rateε̇c at which a stable drop shape no longer exists. Tostudy the droplet behavior in a more realistic flow, atriangular strain rate - time profile is applied, varyingthe rheological properties of the phases as well as theparameters 1T and 1ε̇ (see figure 1).ResultsExperiments have been performed using a visco-elastic drop (R=1.23 mm, 1.65 wt% PEO 5e6 in H2O)dispersed in silicon oil (ηc =10 Pa·s), which has acritical deformation Dc ≈ 0.35 (figure 2).ε̇ε̇cε̇ε̇cDDLBD = (L− B) / (L + B)Dlin. theoryTime [s]0000.10.20.20.30.40.40.50.60.60.81.01.2100 200 300 400 500 600 700 800 900fig. 2 Deformation in quasi steady flowε̇ε̇cDDcAABBBLD = (L− B) / (L + B)Time [s]0000.10.20.30.40.50.50.6110 20 30 40 50 60 70 80 90fig. 3 Droplet deformation, applying a triangular strainrate profile with 1ε̇ = 0.25ε̇c and 1T=2.7, 5.6, 11, 17, 22,28, 33, 39, 44, 50, and 56 s.Applying triangular strain rate - time profiles with1ε̇ = 0.25 ε̇c and various 1T, it is found that at small1T, the droplet can not respond fast enough to reachthis deformation Dc, see figure 3. As 1T is in-creased, the droplet reaches more elongated shapeswith D > Dc, though break up does not occur. As isshown in figure 4, the drop will break up if 1T ex-ceeds a critical value.t = 0 st = 13 st = 26 st = 40 st = 49 st = 57 st = 63 st = 68 st = 71 st = 74 st = 76 st = 79 st = 82 st = 85 sfig. 4 Droplet response to the triangular strain rate - timeprofiles A (left, 1T=50s) and B(right,1T=56s) of figure 3Future Work3 Experimental examination of:? the influence of visco-elasticity? the critical values of parameters 1T, 1ε̇3 Numerical analysis of the response of a dropletto time-dependent strain rate profilesAcknowledgementsThis research is part of the FAIR project BioMix,funded by the European Community.

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Break up of droplets in time-dependent flow

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Break up of droplets in time-dependent flow

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