Adaptive near-contact repulsion in conservative Allen-Cahn phase-field lattice Boltzmann multiphase model

Abstract: Unresolved thin-film dynamics often causes spurious coalescence in diffuse-interface simulations of multiphase flows. We address this issue by introducing a fully local repulsive near-contact flux in a conservative Allen--Cahn phase-field model coupled to lattice Boltzmann hydrodynamics. The interaction activates only for oppositely oriented nearby interfaces, with a strength that self-adjusts based upon an analytical estimate of the local film thickness extracted from the phase field. The resulting method circumvents nonlocal geometric procedures, preserves computational efficiency, and is well suited to massively parallel implementations. Tests on collision benchmarks and three-dimensional bubble swarms demonstrate robust suppression of artificial merging and physically consistent near-contact dynamics.