(546c) Fingering Effects in Oil-Water Interfaces with Nanoparticles Using Coarse-Grained Computations

There are several applications in which the stability of interfaces in the presence of surface-active nanoparticles is of great importance, such as separation processes [1,2], environmental remediation [3,4], etc. While appropriate attention has been paid to the physical mechanism for stabilizing the fluid-fluid interface in bare oil-water systems, the effects of particles on the resulting properties of the oil-water interface under applied stresses still need to be explored. In this work, the dissipative particle dynamics (DPD) technique [5-7] is applied to investigate the impact of nanoparticles and their wettability on the stability of two immiscible fluids with different types of nanoparticles; pure oil (dodecane) and water are placed side by side in a nanochannel forming a meniscus. Nanoparticles are simulated at the oil-water interface, and their wettability is controlled based on their amphiphilicity. The results show that during water flooding, two instabilities occur: the formation of fingers and the separation of oil from the channel wall.

The meniscus stability is significantly affected by the wettability of the nanoparticles. A hydrophobic nanoparticle network can disrupt the formation of a stable water meniscus at lower flow rates when compared with Janus and hydrophilic nanoparticles. All particles allow for fingering at lower pressure drops than in pure oil and water. The second instability leads to the formation of a drop that propagates through the channel. The wetting properties of nanoparticles do not influence the critical flow rate for developing the second instability. Therefore detachment occurs at the same three-phase contact angle regardless of particle wetting properties. Moreover, as the droplet travels at the center of the channel, nanoparticles tend to locate at the front side of the droplets for all cases. A discussion of the computational methodology and its validation will be presented, as well as the mechanism for stabilizing the oil-water interface using different types of nanoparticles.

References

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