  In this paper, a diffuse-interface lattice Boltzmann method (DI-LBM) is
developed for fluid-particle interaction problems. In this method, the sharp
interface between the fluid and solid is replaced by a thin but nonzero
thickness transition region named diffuse interface, where the physical
variables varies continuously. In order to describe the diffuse interface, we
introduce a smooth function, which is similar to the order parameter in
phase-field model or the volume fraction of solid phase in the partially
saturated lattice Boltzmann method (PS-LBM). In addition, to depict the
fluid-particle interaction more accurately, a modified force term is also
proposed and included in the evolution equation of the DI-LBM. Some classical
problems are used to test the DI-LBM, and the results are in good agreement
with some available theoretical and numerical works. Finally, it is also found
that the DI-LBM is more efficient and accurate than the PS-LBM with the
superposition model.
