A modeling approach to droplet contact-line motion dynamics in high-density-ratio two-phase flow

The present study is to investigate the contact line dynamics in high-density-ratio two-phase flow. A two-dimensional lattice Boltzmann model for immiscible fluids flow with gravity is developed, which combines the stabilized numerical discretization for the continuous Boltzmann equation and the diffuse-interface theory. The model is developed on the basis of previous work. However, some significant modifications are made to suit the purpose of the present study, including direct calculation of macroscopic variables without post-collision process and consideration of gravity. The model and numerical method are firstly validated by various flow problems with analytical solutions. It is then used to investigate the contact line motion of a droplet attached on a substrate in shear flow. The influences of a series of flow parameters are systematically investigated and some conclusions are obtained. Above the critical Capillary number, the droplet motion exhibits break-up characteristics. In steady-slip mode, the receding contact angle, θR, decreases and advancing contact angle, θA, increases linearly with the Capillary number, Ca, while the normalized droplet velocity nearly holds constant with different values of Ca. The contact line motion is not sensitive to Reynolds number, Re. When Bond number Bo > 1, both the dynamic contact angles and the droplet velocity decrease significantly with increasing Bo. The obtained results are partially compared with those reported by other investigators, and a good agreement has been reached in several aspects, such as break-up characteristics and Bond number effect.

► The model permits the simulations with high density ratio up to 1000. ► The gravity effect is considered. ► Several benchmark cases are computed to validate the model. ► Motion of a droplet attached on a substrate in shear flow is well depicted.