An improved immersed moving boundary-based curved wetting condition method for the pseudopotential multiphase lattice Boltzmann model

The wettability treatment of curved boundaries is crucial for multiphase flow simulations at high density ratio. The conventional curved boundary methods all suffer from the problem of mass leakage. The immersed moving boundary (IMB) method is naturally mass-conserving for handling curved boundary but is currently only applicable to multiphase flows of low density ratios. Herein, an improved IMB curved wetting condition method in the pseudopotential lattice Boltzmann (LB) model is proposed for simulating multiphase flows at high density ratios. The IMB method is employed to manage curved boundaries, and the calculation of intermolecular interaction forces is modified to adjust contact angles. A series of static and dynamic multiphase flow simulations are conducted to demonstrate the performance of this method. Compared with the conventional curved boundary methods, the improved IMB method achieves mass conservation in multiphase flow simulations naturally without additional correction. Meanwhile, it exhibits lower spurious currents at large density ratios and various contact angles and accurately reproduces the fluid density distribution near curved wall. This improved IMB method also effectively models the dynamic behavior of the droplet impact on curved surfaces. Finally, the improved IMB method is extended to the simulation of multi-component multiphase flows-the impact behavior of droplet on sinusoidal wall surface at low Weber numbers (0.78-8.65) and a high density ratio of 140. Three different droplet behaviors of deposition, rebound, and breakup are observed upon the impingement by adjusting the droplet's velocity, wall wettability, and wall width. Additionally, the relationship of the contact time follows the law: t(c)* similar to We(0.17) ( We = 2.16-7.01). The present method is expected to be an alternative for complex curved wetting phenomena in pseudopotential LB multiphase flow simulations.