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      Effects of viscoelasticity on droplet dynamics and break-up in microfluidic T-Junctions: a lattice Boltzmann study

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          Abstract

          The effects of viscoelasticity on the dynamics and break-up of fluid threads in microfluidic T-junctions are investigated using numerical simulations of dilute polymer solutions at changing the Capillary number (\(\mbox {Ca}\)), i.e. at changing the balance between the viscous forces and the surface tension at the interface, up to \(\mbox{Ca} \approx 3 \times 10^{-2}\). A Navier-Stokes (NS) description of the solvent based on the lattice Boltzmann models (LBM) is here coupled to constitutive equations for finite extensible non-linear elastic dumbbells with the closure proposed by Peterlin (FENE-P model). We present the results of three-dimensional simulations in a range of \(\mbox{Ca}\) which is broad enough to characterize all the three characteristic mechanisms of breakup in the confined T-junction, i.e. \({\it squeezing}\), \({\it dripping}\) and \({\it jetting}\) regimes. The various model parameters of the FENE-P constitutive equations, including the polymer relaxation time \(\tau_P\) and the finite extensibility parameter \(L^2\), are changed to provide quantitative details on how the dynamics and break-up properties are affected by viscoelasticity. We will analyze cases with \({\it Droplet ~Viscoelasticity}\) (DV), where viscoelastic properties are confined in the dispersed (d) phase, as well as cases with \({\it Matrix ~Viscoelasticity}\) (MV), where viscoelastic properties are confined in the continuous (c) phase. Moderate flow-rate ratios \(Q \approx {\cal O}(1)\) of the two phases are considered in the present study. Overall, we find that the effects are more pronounced in the case with MV, as the flow driving the break-up process upstream of the emerging thread can be sensibly perturbed by the polymer stresses.

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          Author and article information

          Journal
          2015-08-01
          2016-07-26
          Article
          10.1140/epje/i2016-16006-9
          1508.00141
          b80b83b1-86ab-42be-a8f9-c277005b18de

          http://arxiv.org/licenses/nonexclusive-distrib/1.0/

          History
          Custom metadata
          16 pages, 14 figures; This Work applies the Numerical Methodology described in arXiv:1406.2686 to the Problem of Droplet Generation in Microfluidic T-Junctions. arXiv admin note: substantial text overlap with arXiv:1508.00559
          physics.flu-dyn cond-mat.soft

          Condensed matter,Thermal physics & Statistical mechanics
          Condensed matter, Thermal physics & Statistical mechanics

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