Effects of viscoelasticity on droplet dynamics and break-up in microfluidic T-Junctions: a lattice Boltzmann study · arXivDesk
1508.00141Aug 1, 201516 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
Effects of viscoelasticity on droplet dynamics and break-up in microfluidic T-Junctions: a lattice Boltzmann study
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 (Ca), i.e. at changing the balance between the viscous forces and the surface tension at the interface, up to Ca ≈ 3 × 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 Ca which is broad enough to characterize all the three characteristic mechanisms of breakup in the confined T-junction, i.e. squeezing, dripping and jetting regimes. The various model parameters of the FENE-P constitutive equations, including the polymer relaxation time τP
Nearby in the stack
and the finite extensibility parameter
L2
, are changed to provide quantitative details on how the dynamics and break-up properties are affected by viscoelasticity. We will analyze cases with
DropletViscoelasticity
(DV), where viscoelastic properties are confined in the dispersed (d) phase, as well as cases with
MatrixViscoelasticity
(MV), where viscoelastic properties are confined in the continuous (c) phase. Moderate flow-rate ratios
Q≈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.