Abstract

In recent years the lattice Boltzmann method has increasingly become a method of choice for simulating complex multiphase and interfacial flows, owing to its suitability for parallel computations and its flexibility to incorporate different physical phenomena. Here, I will illustrate the prowess of LBM by using two applications. First, by coupling LBM and Discrete Element Method, we elucidate salient mechanisms of how particles can be captured and removed by liquid droplets, which is key for designing self-cleaning surfaces. We can map out the different possible outcomes of the particle-droplet collision dynamics, in good agreement compared to experiments, and rationalise them by considering the competition between capillary, hydrodynamics, and friction forces. We are also able to identify a threshold parameter to predict particle capture. Second, by extending the LBM scheme to arbitrary N immiscible fluid components, we can explore spontaneous phase separation dynamics for up to 8 immiscible fluid components. In 2D (and thin 3D) systems, droplet coalescence is strongly suppressed because of the four-colour theorem, leading to diffusion-dominated coarsening dynamics that can be captured by a master scaling law for N equal or larger than 4. In 3D, the absence of four-color theorem (or its equivalent) means that the diffusive scaling law is only reached for asymptotically large N.