Universal Scaling Laws for Dense Particle Suspensions in Turbulent Wall-Bounded Flows

TL;DR

This paper develops universal scaling laws for dense particle suspensions in turbulent wall-bounded flows, accounting for particle size effects and near-wall particle layers to predict flow behavior and drag increase.

Contribution

It introduces a new framework that incorporates particle size and near-wall effects into scaling laws for suspension flow velocity profiles.

Findings

Particles larger than turbulence scales cause deviations from continuum behavior.

A new effective wall location accounts for near-wall slip and particle layers.

The proposed master equation predicts drag increase based on particle size and volume fraction.

Abstract

The macroscopic behavior of dense suspensions of neutrally-buoyant spheres in turbulent plane channel flow is examined. We show that particles larger than the smallest turbulence scales cause the suspension to deviate from the continuum limit in which its dynamics is well described by an effective suspension viscosity. This deviation is caused by the formation of a particle layer close to the wall with significant slip velocity. By assuming two distinct transport mechanisms in the near-wall layer and the turbulence in the bulk, we define an effective wall location such that the flow in the bulk can still be accurately described by an effective suspension viscosity. We thus propose scaling laws for the mean velocity profile of the suspension flow, together with a master equation able to predict the increase in drag as function of the particle size and volume fraction.