Investigation on spontaneous liquid–liquid imbibition in capillaries with varying axial geometries using lattice Boltzmann method

Underground H2 storage (UHS), i.e., injecting H2 into subsurface geological formation and its withdrawal when needed, is identified as a promising solution for large-scale and long-term storage of H2. In this study, molecular dynamics (MD) simulation was performed at a typical temperature 320 K with pressure up to 60 MPa to predict H2 transport properties and H2–H2O–rock interfacial properties, which are compared with those of CO2 and CH4. The MD results show that the CH4 profiles of property variations with pressure lie between those of H2 and CO2 and more comparable to CO2. The interaction of H2 with H2O/silica is much weaker than that of CH4 and CO2. It is found that the effect of H2 pressure on altering the water contact angle and interfacial tension is negligible under all conditions. Unlike the multi-adsorption layers of the confined CO2 and CH4, there is only one adsorption layer of H2 confined by silica nano-slit. The planar diffusion of H2 in the confined system is slower than that in the bulk system at pressures lower than 20 MPa. The data and findings of this study will be useful for modeling the multiphase flow dynamics of UHS on reservoir scale, optimizing UHS operation, and assessing the performance of a cushion gas, e.g., CO2 or CH4.

A comparative study on transport and interfacial physics of H2/CO2/CH4 interacting with H2O and/or silica by molecular dynamics simulation

Chen,

Xia

2024

Simulation of droplet dynamics in an inclined channel considering contact angle hysteresis using the cascade lattice Boltzmann method

Zhang,

Li,

Zhu

et al. 2024

Modeling droplet dynamics on solid surfaces with rough or chemically heterogeneous walls is crucial in various industrial applications. In such cases, the downstream and upstream contact lines of the droplet usually move incongruously, leading to droplet deformation known as the contact angle hysteresis (CAH) phenomenon. In this work, we developed a cascaded multicomponent Shan–Chen lattice Boltzmann method to simulate droplet dynamics considering the CAH. Specifically, the Peng–Robinson equation of state is added to one component to improve the density ratio of the model. By modifying the fluid–fluid interaction force scheme, we achieve thermodynamic consistency and independent adjustment of the surface tension. We also implement the modeling of CAH by applying geometric wetting boundaries with a hysteresis window. Based on this model, we first simulated pinned droplets in inclined channels with different hysteresis windows. We obtain the critical tilt angle of the droplet at the onset of sliding, which agrees with the theoretical result. For sliding droplets in the inclined channel, our results reveal that a slight tilt angle is unfavorable for the upstream portion of the droplet sliding, while a large tilt angle is favorable for the entire droplet sliding. A small receding angle results in a large droplet deformation at the quasi-steady state. Finally, by periodically transitioning between different hysteresis windows, enabling exclusive sliding of the upstream contact line during the first half period and subsequent sliding of the downstream contact line during the second half period, we successfully observed the stick-slip phenomenon of the droplet.

Minimum resistance radius for gas–liquid spontaneous imbibition in microtubes

Ding,

Song,

Huang

et al. 2024

Spontaneous imbibition is the natural movement of a wetting phase liquid within porous media or microtubes. Such flow occurs commonly in nature and industrial settings, where gas and liquid phases flow spontaneously through porous materials. To delve deeper into the characteristics and mechanisms of gas–liquid two-phase spontaneous imbibition at the microscale, this paper establishes a mathematical model considering acceleration. Through both numerical simulations and experiments, the detailed analysis of de-ionized water's spontaneous imbibition within microtubes sheds light on interface phenomena at the microscale. The results highlight the pronounced influence of the microtube radius and gas-water interfacial tension on the imbibition process. By combining experimental work, theoretical analysis, and numerical simulations, this study identifies the minimum resistance radius—a tube radius leading to the shortest imbibition time to the top. The research underscores the significance of considering acceleration and provides a theoretical groundwork for leveraging spontaneous imbibition. It also holds potential value for applications in microfluidic technology, nanomaterial synthesis, and biomedical fields.