Particle resuspension from complex multilayer deposits by laminar flows: statistical analysis and modeling

TL;DR

This study investigates how large spherical particles detach and move from complex sediment beds under laminar flow, using detailed simulations and statistical analysis to understand the resuspension process and develop a predictive model.

Contribution

It provides a detailed statistical analysis of particle resuspension dynamics and introduces a simple surface-based model to predict detachment ratios in laminar flows.

Findings

Particles detach more frequently at surface peaks.

Detached particles undergo short hops before sedimenting.

A surface characteristic-based model predicts detachment ratios.

Abstract

Particle resuspension refers to the physical process by which solid particles deposited on a surface are, first, detached and, then, entrained away by the action of a fluid flow. In this study, we explore the dynamics of large and heavy spherical particles forming a complex sediment bed which is exposed to a laminar shear flow. For that purpose, we rely on fine-scale simulations based on a fully-resolved flow field around individual particles whose motion is explicitly tracked. Using statistical tools, we characterize several features: (a) the overall bed dynamics (e.g. the average particle velocity as a function of the elevation), (b) the evolution of the top surface of the sediment bed (e.g. distribution of the surface elevation or of the surface slope) and (c) the dynamics of individual particles as they detach from or re-attach to the sediment bed (including the frequency of these events, and the velocity difference / surface angle for each event). These results show that particles detach more frequently around the peaks in the top surface of the sediment bed and that, once detached, they undergo short hops as particles quickly sediment towards the sediment bed. A simple model based on the surface characteristics (including its slope and elevation) is proposed to reproduce the detachment ratio.