Insight into the Pressure-induced Displacement Mechanism for Selecting Efficient Nanofluids in Various Capillaries

Designing fluids to regulate two-phase displacement has been of great interest because of its roles in groundwater remediation, oil recovery and water desalination. Currently, the displacement efficiency of fluids is observed to depend on the surface properties of capillary and external pressure. Herein, the pressure-induced displacement mechanisms in various capillaries are investigated by molecular dynamics simulations. Our results suggest that the surface wettability and pressure are crucial to the displacement performance of fluids. Specifically, reducing the interfacial tension of fluids is beneficial to displacement efficiency in hydrophobic capillary, while increasing viscosity of fluids favors for hydrophilic capillary. Based on our proposed mechanisms and considering the capillaries wettability, three types of nanofluids are designed to improve the displacement efficiency for different capillaries. Our results are significant for understanding fluids flow phenomenon and provide an efficient way to design the target fluids for numerous applications