We study the physics of droplet breakup in a statistically stationary
homogeneous and isotropic turbulent flow by means of high resolution numerical
investigations based on the multicomponent lattice Boltzmann method. We
verified the validity of the criterion proposed by Hinze (1955) for droplet
breakup and we measured the full probability distribution function (pdf) of
droplets radii at different Reynolds numbers and for different volume fraction.
By means of a Lagrangian tracking we could follow individual droplets along
their trajectories, define a local Weber number based on the velocity gradients
and study its cross-correlation with droplet deformation.Comment: 10 pages, 6 figure
We study the dynamics of the interface between two immiscible fluids in contact with a chemically homogeneous moving solid plate. We consider the generic case of two fluids with any viscosity ratio and of a plate moving in either directions (pulled or pushed in the bath). The problem is studied by a combination of two models, namely, an extension to finite viscosity ratio of the lubrication theory and a Lattice Boltzmann method. Both methods allow to resolve, in different ways, the viscous singularity at the triple contact between the two fluids and the wall. We find a good agreement between the two models particularly for small capillary numbers. When the solid plate moves fast enough, the entrainment of one fluid into the other one can occur. The extension of the lubrication model to the case of a non-zero air viscosity, as developed here, allows us to study the dependence of the critical capillary number for air entrainment on the other parameters in the problem (contact angle and viscosity ratio). C 2013 AIP Publishing LLC. [http://dx
A lattice Boltzmann method for axisymmetric multiphase flows is presented and validated. The method is capable of accurately modeling flows with variable density. We develop the classic Shan-Chen multiphase model [Phys. Rev. E 47, 1815(1993] for axisymmetric flows. The model can be used to efficiently simulate single and multiphase flows. The convergence to the axisymmetric Navier-Stokes equations is demonstrated analytically by means of a Chapmann-Enskog expansion and numerically through several test cases. In particular, the model is benchmarked for its accuracy in reproducing the dynamics of the oscillations of an axially symmetric droplet and on the capillary breakup of a viscous liquid thread. Very good quantitative agreement between the numerical solutions and the analytical results is observed.
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