Lattice Boltzmann method with immersed spring boundaries for flow around deformable porous media

For swollen polyethylene (PE) particle composed of a rigid solid core surrounded by a porous shell in slurry loop reactors, an efficient approach is proposed for simulating its complex flow behaviors in fluid, mainly concerning the liquid capture in the porous shell and the deformation of the porous shell. The proposed method (i.e. the IB-LBM for short) employs the immersed boundary method (IBM) to deal with the moving and deformation of PE particle, and uses the lattice Boltzmann method (LBM) to calculate the flow field. Further, a generalized Hooke's law is embodied to calculate the restoring force on the boundary of PE particle and a modified lattice Boltzmann equation is proposed to consider both the porous and deformable effects of swollen PE particle. Then a series of numerical experiments are designed to study the liquid capture in the deformable porous shell. The simulation results can reveal clearly the complicated evolution process, such as the flow fields around a swollen PE particle, the deformable porous shell and the liquid capture capability, in the way how to be influenced by the PE particle size, the porosity distribution and the external flow velocities respectively. The main contribution of the work is to consider the intrinsic relationship between the deformation and the porosity distribution in the porous shell during the evolution. Numerical results show that IB-LBM successfully reveal the hydrodynamic characteristics of flow around a swollen PE particle, indicating it's feasibility and practicality for modeling the complex deformable particles. (C) 2016 Elsevier Ltd. All rights reserved.