Deagglomeration of cohesive particles by turbulence

摘要

We present a numerical study analysing the breakup of a single cohesive particle aggregate in turbulence. Solid particles with diameters smaller than the Kolmogorov length scale () are initially aggregated into a spherical 'clump' of diameter and placed in homogeneous isotropic turbulence. Parameters are chosen relevant to dust or powder suspended in air such that cohesion due to van der Waals is important. Simulations are performed using an Eulerian-Lagrangian framework that models two-way coupling between the fluid and solid phases and resolves particle-particle interactions. Aggregate breakup is investigated for different adhesion numbers , Taylor microscale Reynolds numbers and non-dimensional clump sizes . The intermittency of turbulence is found to play a key role on the early stage breakup process, which can be characterized by a turbulent adhesion number that relates the potential energy of the van der Waals force to turbulent shear stresses. A scaling analysis shows that the time rate of breakup for each case collapses when scaled by and an aggregate Reynolds number proportional to . A phenomenological model of the breakup process is proposed that acts as a granular counterpart to the Taylor analogy breakup (TAB) model commonly used for droplet breakup. Such a model is useful for predicting particle breakup in coarse-grained simulation frameworks, such as Reynolds-averaged Navier-Stokes, where relevant spatial and temporal scales are not resolved.