Numerical simulation on the settling characteristics of biomass in a bionic intestinal peristaltic reactor

Bioconversion of lignocellulosic biomass is an eco-friendly approach to energy utilization, and bionic intestinal peristaltic reactors (BIPRs) show promise for enhancing this process through low-shear mixing. However, previous studies often treat substrate flow as a single phase, thereby ignoring the two-phase nature of actual biomass slurries and the associated sedimentation of solid particles. In this study, a multiphysics model of solid–liquid two-phase flow and mass transfer in BIPRs was developed for the first time using the Eulerian–Eulerian approach, and the settling characteristics of biomass slurry in flexible reactors were investigated. Dimensionless secondary flow intensity Sem increases from 8.7 to 48.9 when the peristaltic amplitude ratio rises from 16.7% to 66.7%. The time-averaged relative standard deviation (RSD) decreases by 38.0% from 0.77 to 0.48 when the dimensionless peristaltic amplitude ratio increases from 16.7% to 66.7%. When the dimensionless peristaltic period is more than 0.5, the maximum distribution of the shear strain rate of each condition is less than 1000 s−1. At the dimensionless peristaltic amplitude ratio of 66.7%, the dimensionless peristaltic period of 2, the dimensionless peristaltic wavelength of 1.67, and the inlet volume fraction of 0.055, the biomass slurry achieves the optimal suspension performance with an RSD of 0.18, which shows a 74.3% decrease as compared with the static reactor, indicating a more efficient mixing effect.