Wall slipping behavior of foam with nanoparticle-armored bubbles and its flow resistance factor in cracks

In this work, wall slipping behavior of foam with nanoparticle-armored bubbles was first studied in a capillary tube and the novel multiphase foam was characterized by a slipping law. A crack model with a cuboid geometry was then used to compare with the foam slipping results from the capillary tube and also to evaluate the flow resistance factor of the foam. The results showed that the slipping friction force F _FR in the capillary tube significantly increased by addition of modified SiO₂ nanoparticles, and an appropriate power law exponents by fitting F _FR vs. Capillary number, Ca, was 1/2. The modified nanoparticles at the surface were bridged together and formed a dense particle "armor" surrounding the bubble, and the interconnected structures of the "armor" with strong steric integrity made the surface solid-like, which was in agreement with the slip regime associated with rigid surface. Moreover, as confirmed by 3D microscopy, the roughness of the bubble surface increased with nanoparticle concentration, which in turn increased the slipping friction force. Compared with pure SDBS foam, SDBS/SiO₂ foam shows excellent stability and high flow resistance in visual crack. The resistance factor of SiO₂/SDBS foam increased as the wall surface roughness increased in core cracks.