Immersed boundary method for considering lubrication effects in the CFD-DEM simulations

Although the CFD-DEM simulations could predict the long-range hydrodynamic interaction with high accuracy, they face difficulty in the close distance between particles because mesh resolution is not fine enough to capture the lubrication effects. As a remedy, we used a variant of Immersed Boundary method in our CFD solver to model a problem as a fully resolved simulation. Then, we developed a second-order boundary layer reconstruction approach to increase the accuracy of the immersed boundary method. Furthermore, for the first time and in the present work, we considered how shared cells between the particles need to be treated in the simulation of two approaching particles. Moreover, we investigated the relationship between mesh resolution and time step size on the accuracy of the calculated force. We found a specific range for this ratio to capture the correct short-range hydrodynamic interactions.