  This paper presents an improved immersed moving boundary model (IBM) for
solving complex fluid-particle interactions in a coupled lattice Boltzmann
method (LBM) and an adhesive discrete element method (DEM), using the
"partially saturated cell" scheme. It is shown that the existing scheme does
not well address the contribution of each solid particle to the fluid when
multiple particles intersect with the same lattice cell. This issue is
completely addressed by modifying the weighting function in the partially
covered cells in the present study. Furthermore, a fast linear approximation
method with high efficiency and good accuracy is applied to calculate the
partially intersected volume between a particle and a lattice cell. Verified
with several benchmark cases, the developed hybrid IBM-LBM-DEM numerical
framework is capable of describing the flow field between dense particles with
a relatively low grid resolution in more details, as well as effectively
capturing the adhesive mechanics between microspheres.
