Dimensionality and morphology of particle and bubble clusters in turbulent flow

TL;DR

This study uses numerical simulations and morphological analysis to explore how particles and bubbles cluster in turbulent flows, revealing distinct structures and dimensions based on particle properties.

Contribution

It introduces a morphological analysis using Minkowski functionals to distinguish clustering structures in turbulent multiphase flows, advancing understanding beyond traditional dimension measures.

Findings

Light bubbles form filamentary structures with a dimension of ~1.4.

Heavy particles form wall-like structures with a dimension of ~2.4.

Morphological analysis reveals different clustering geometries not captured by dimension alone.

Abstract

We conduct numerical experiments to investigate the spatial clustering of particles and bubbles in simulations of homogeneous and isotropic turbulence. Varying the Stokes parameter and the densities, striking differences in the clustering of the particles can be observed. To quantify these visual findings we use the Kaplan--Yorke dimension. This local scaling analysis shows a dimension of approximately 1.4 for the light bubble distribution, whereas the distribution of very heavy particles shows a dimension of approximately 2.4. However, clearly separate parameter combinations yield the same dimensions. To overcome this degeneracy and to further develop the understanding of clustering, we perform a morphological (geometrical and topological) analysis of the particle distribution. For such an analysis, Minkowski functionals have been successfully employed in cosmology, in order to quantify the global geometry and topology of the large-scale distribution of galaxies. In the context of dispersed multiphase flow, these Minkowski functionals -- being morphological order parameters -- allow us to discern the filamentary structure of the light particle distribution from the wall-like distribution of heavy particles around empty interconnected tunnels.