Dense Particle Suspensions in Turbulence

Dense particle suspensions in turbulence are commonly encountered in industrial and geophysical environments. However, previous studies have mainly focused on either dense suspension in laminar flows or dilute particle-laden turbulence. This is partly due to the challenges in visualizing and tracking a large number of particles individually in a turbulent system.

Here we perform laboratory experiments on non-Brownian spherical particles suspended in an electro-magnetically driven quasi-two-dimensional (Q2D) flow. This enables us to track the particles up to jamming conditions. By systematically varying the particle size, area fraction (up to 70%), interfacial conditions, and the Reynolds number up to developed turbulence, we gain insights into clustering tendencies and transport of the particles both from Lagrangian and Eulerian perspectives.

Our comprehensive analysis of over 100 cases elucidates the interplay of three forces that mainly govern the dynamics: capillary attraction due to undulation of the contact line, drag force exerted by the fluid, and lubrication forces between nearby particles. We propose a phase diagram based on the balance of the involved forces and experimental results, which highlights distinct regimes of cluster formation and particle transport.