Investigation of cohesive particle deagglomeration in homogeneous isotropic turbulence using particle-resolved DNS

TL;DR

This paper uses detailed particle-resolved DNS to analyze how turbulence causes particle agglomerates to break apart, revealing erosion as the main mechanism and providing insights for improved breakup modeling.

Contribution

It introduces a particle-resolved simulation framework to study agglomerate breakup in turbulence, identifying erosion as the dominant mechanism and linking breakage to flow strain.

Findings

Erosion-driven breakage dominates particle disintegration.

Breakage rate follows a power-law decay with adhesion number.

Fragment ejection aligns with local strain-rate eigenvectors.

Abstract

In this study, agglomerate breakage in homogeneous isotropic turbulence is investigated using particle-resolved direct numerical simulations. Single agglomerates composed of 500 monodisperse spherical particles are considered, and their interaction with the turbulent flow is resolved through an immersed boundary method coupled with a soft-sphere discrete element model. A range of Reynolds numbers and cohesion levels is examined to assess their influence on the breakup behavior. Detailed insights into the underlying breakage mechanisms are provided through the analysis of local flow structures and fluid stresses. Strain-dominated regions are identified as the primary contributors to the onset and propagation of particle erosion. The benefits of the particle-resolved simulation framework in capturing these physical processes in detail are demonstrated. The predicted fragment size distributions and breakup modes are analyzed leading to the outcome that erosion-driven breakage is the dominating mechanism. The time evolution of the fragment number and the main agglomerate structure is quantified. The breakage rate is evaluated and its dependence on the modified adhesion number is established, showing a power-law decay that agrees with general trends reported in the literature. In addition, the analysis of the fragment ejection direction reveals a strong alignment with the local deformation plane spanned by the most extensional and compressive strain-rate eigenvectors, indicating that breakage results from the interplay between flow stretching and compression. The results contribute to the development of physics-informed breakup kernels for use in efficient but less-detailed simulation approaches such as point-particle Euler--Lagrange predictions with agglomerates represented by effective spheres or Euler--Euler simulations.