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Shear rheology of non-Newtonian emulsions made of viscoelastic droplets in a Newtonian matrix

University of British Columbia

In the case of an oil spill in a marine environment, an important aspect of an early response is to confine the oil spill and prevent it from getting dispersed. At the laboratory level, chemists are capable of designing new solidifiers known as "gellants", that when applied by spraying or injection in the marine oil-spill, are capable of making the oil regroup and create a gel-like material (gelled-oil). Even though gellants make the removing of oil-spill from a marine environment easier, it is not clear whether gelled-oil is more stable in terms of break-up and how gellants affect the dispersion rate of the oil-spill. Gellants create a gelled-oil emulsion in the marine environment, which can be modelled as a dispersion of non-Newtonian droplets (gelled-oil) in a Newtonian matrix (sea water). In this study we develop a better understanding of such a liquid/liquid system subjected to imposed shear. Both the rheological nature of the oil and the oil/water surface tension are the key parameters. We address this problem from a computational viewpoint using an advanced open source academic code to perform parallel simulations. We analyze two main problems: 1) the deformation of a single droplet in a simple shear flow, and 2) the rheological behaviour of an emulsion in a simple shear flow. We show that, since applying gellants increase the surface tension and viscosity of the dispersed oil phase, the oil-water emulsion is more stable (i.e. the dispersed oil droplets deform less) and the dispersion rate of the oil in the marine environment is reduced. Moreover, we obtain results showing that the elasticity of the dispersed gelled-oil phase has a non-monotonic impact on the flow features and a very limited influence on the general behaviour of the emulsion. The conducted analysis in this project and its outcome can help to provide recommendations on how these gelled materials behave.

Text

2020-08-31

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/75767

Chemical and Biological Engineering

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/