Global and local statistics in turbulent emulsions
Abstract
Turbulent emulsions are complex physical systems characterized by a strong and dynamical coupling between smallscale droplets and largescale rheology. By using a specifically designed TaylorCouette (TC) shear flow system, we are able to characterize the statistical properties of a turbulent emulsion made of oil droplets dispersed in an ethanolwater continuous solution, at the oil volume fraction up to 40%. We find that the dependence of the droplet size on the Reynolds number of the flow at the volume fraction of 1% can be well described by Hinze's criterion. The distribution of droplet sizes is found to follow a lognormal distribution, hinting at a fragmentation process as the possible mechanism dominating droplet formation. Additionally, the effective viscosity of the turbulent emulsion increases with the volume fraction of the dispersed oil phase, and decreases when the shear strength is increased. We find that the dependence of the effective viscosity on the shear rate can be described by the HerschelBulkley model, with a flow index monotonically decreasing with increasing the oil volume fraction. This finding indicates that the degree of shear thinning systematically increases with the volume fraction of the dispersed phase. The current findings have important implications for bridging the knowledge on turbulence and lowReynoldsnumber emulsion flows to turbulent emulsion flows.
 Publication:

Journal of Fluid Mechanics
 Pub Date:
 April 2021
 DOI:
 10.1017/jfm.2020.1118
 arXiv:
 arXiv:2011.00963
 Bibcode:
 2021JFM...912A..13Y
 Keywords:

 Physics  Fluid Dynamics
 EPrint:
 J. Fluid Mech. 912 (2021) A13