Analysis of Contact Angle in Capillary Invasion

The correct knowledge of the physical processes that control the fluid-fluid interface displacement at the pore-level is of increasing interest due to the growing possibility of direct simulation of immiscible displacement offered by the strong development of computers’ performance and numeric methods and to the increasing accuracy in three-dimensional reconstruction methods. Flow of immiscible fluids is, classically, treated by considering that the transition layer has a null thickness. In this way, in addition to intrinsic physical properties of the involved fluids, the only macroscopic parameter of interest is the interfacial tension. At microscopic level, when two immiscible fluids are mixed, the long-range attraction between the molecules of each fluid is the molecular mechanism promoting fluid segregation. The thickness of transition layer is, consequently, controlled by the strength and length of long-range potentials and by the binary diffusivity. Theoretical difficulty is strongly increased when these two fluids interact with a solid surface. In fact, the interfacial energies between the fluids and the surface are the main macroscopic mechanisms governing interface advancing or receding on a solid surface. In present work, a lattice Boltzmann model is presented and used for studying the dynamic effects on the contact angle produced by interface displacement.