An experimental study on the motion of buoyant particles in the free-surface vortex flow

Journal article (2021)

Authors

S.P.A. Duinmeijer Sanitary Engineering - CEG , Gemeente Rotterdam
F.H.L.R. Clemens Deltares, Sanitary Engineering - CEG
Research Group
Sanitary Engineering (CEG) (TU Delft)
Copyright: © 2021 S.P.A. Duinmeijer, F.H.L.R. Clemens
DOI: https://doi.org/10.1080/00221686.2020.1845827
3D-PTV Axial particle motion Chaotic behaviour Free-surface vortex Particle dynamics Stable limit cycle Taylor column drag coefficient Vortex core
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Published Date

2021

Language

English

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Faculty

Civil Engineering & Geosciences

Department

Water Management

Research Group

Sanitary Engineering

Abstract

Experiments are conducted in a Ø600 mm tank to analyse the 3D motion of buoyant particles in the free-surface vortex flow. The experiments revealed two stages in the particle motion: stage 1 is the helical motion along the vortex air core and stage 2 is the axial motion inside the vortex core. The stage 1 motion is sensitive to the particle’s initial conditions by showing a chaotic behaviour and quantified by determining the largest Lyapunov exponent. Consequently, the predictability (forecast horizon) of the particle’s motion is limited. A motion parameter is proposed that indicates if a continuous downward motion along the air core occurs. The dynamics in the stage 2 motion is determined by the imbalance between the particle’s buoyancy force and fluid drag force. The drag appears to be determined by the Taylor column drag force as present in rotating fluids. Based on this force, a motion condition is proposed that indicates if axial motion inside the vortex core occurs.