Fingering Effects in Oil-Water Interfaces with Nanoparticles

Nanoparticles (NPs) influence the stability of interfaces especially in non-equilibrium situations. Attention has been primarily focused on the physical mechanism for fluid-fluid interfaces stabilized in bare oil-water systems without the presence of nanoparticles. Here, the dissipative particle dynamics (DPD) method [1-3] is applied to investigate the influence of nanoparticles and their wetting properties on the stability of two immiscible fluids; pure oil and water positioned adjacent to each other, resulting in the formation of a meniscus in a nanochannel. The NPs are placed at the oil-water interface. Our findings show that the meniscus stability is affected by the wettability of the nanoparticles, and two instabilities occur during water flooding: first, the formation of fingers, and second, the separation of oil from the channel wall. The presence of NPs allows for fingering at lower pressure drops than in pure oil and water. When considering different NPs, hydrophobic NPs can disrupt the formation of a stable water meniscus at lower flow rates when compared with Janus and hydrophilic nanoparticles. The second instability leads to the formation of a drop that propagates through the channel. The wettability of NPs does not influence the critical flow rate, resulting in the three-phase contact angle being the same when the detachment occurs. The discussion will cover the computational methodology employed and its validation, as well as an analysis of how different types of nanoparticles stabilize the oil-water interface.

References

[1] T. V. Vu and D. V. Papavassiliou, Journal of colloid and interface science 553, 50 (2019).

[2] T. X. Nguyen, S. Razavi, and D. V. Papavassiliou, The Journal of Physical Chemistry B 126, 6314 (2022).

[3] T. X. Nguyen, T. V. Vu, S. Razavi, and D. V. Papavassiliou, Polymers 14, 543 (2022).