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Channel flow of rigid sphere suspensions: Particle dynamics in the inertial regime
KTH, Centres, SeRC - Swedish e-Science Research Centre. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, School of Engineering Sciences (SCI), Mechanics.
KTH, School of Engineering Sciences (SCI), Mechanics, Physicochemical Fluid Mechanics. KTH, Centres, SeRC - Swedish e-Science Research Centre. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. University of Padova, Italy.
KTH, School of Engineering Sciences (SCI), Mechanics, Physicochemical Fluid Mechanics. KTH, Centres, SeRC - Swedish e-Science Research Centre. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.ORCID iD: 0000-0002-4346-4732
2016 (English)In: International Journal of Multiphase Flow, ISSN 0301-9322, E-ISSN 1879-3533, Vol. 78, 12-24 p.Article in journal (Refereed) Published
Abstract [en]

We consider suspensions of neutrally-buoyant finite-size rigid spherical particles in channel flow and investigate the relation between the particle dynamics and the mean bulk behavior of the mixture for Reynolds numbers 500 ≤ Re ≤ 5000 and particle volume fraction 0 ≤ Φ ≤ 0.3, via fully resolved numerical simulations. Analysis of the momentum balance reveals the existence of three different regimes: laminar, turbulent and inertial shear-thickening depending on which of the stress terms, viscous, Reynolds or particle stress, is the major responsible for the momentum transfer across the channel. We show that both Reynolds and particle stress dominated flows fall into the Bagnoldian inertial regime and that the Bagnold number can predict the bulk behavior although this is due to two distinct physical mechanisms. A turbulent flow is characterized by larger particle dispersion and a more uniform particle distribution, whereas the particulate-dominated flows is associated with a significant particle migration towards the channel center where the flow is smooth laminar-like and dispersion low. Interestingly, the collision kernel shows similar values in the different regimes, although the relative particle velocity and clustering clearly vary with inertia and particle concentration.

Place, publisher, year, edition, pages
Elsevier, 2016. Vol. 78, 12-24 p.
Keyword [en]
IMMERSED BOUNDARY METHOD, PRESSURE-DRIVEN FLOW, LINEAR SHEAR FLOWS, POISEUILLE FLOW, CONCENTRATED SUSPENSIONS, NUMERICAL SIMULATIONS, SELF-DIFFUSION, MIGRATION, STRESS, LIFT
National Category
Fluid Mechanics and Acoustics
Identifiers
URN: urn:nbn:se:kth:diva-177849DOI: 10.1016/j.ijmultiphaseflow.2015.09.008ISI: 000367771300002Scopus ID: 2-s2.0-84944810937OAI: oai:DiVA.org:kth-177849DiVA: diva2:874518
Funder
EU, European Research Council, ERC-2013-CoG-616186Swedish Research Council, VR 2011-5354Swedish Research Council, 2014-5001
Note

QC 20152227. QC 20160203

Available from: 2015-11-27 Created: 2015-11-27 Last updated: 2017-12-01Bibliographically approved
In thesis
1. Stability analysis and inertial regimes in complex  flows
Open this publication in new window or tab >>Stability analysis and inertial regimes in complex  flows
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In this work we rst study the non-Newtonian effects on the inertial instabilities in shear flows and second the inertial suspensions of finite size rigid particles by means of numerical simulations.

In the first part, both inelastic (Carreau) and elastic models (Oldroyd-B and FENE-P) have been employed to examine the main features of the non-Newtonian fluids in several congurations; flow past a circular cylinder, in a lid-driven cavity and in a channel. In the framework of the linear stability analysis, modal, non-modal, energy and sensitivity analysis are used to determine the instability mechanisms of the non-Newtonian flows. Signicant modifications/alterations in the instability of the different flows have been observed under the action of the non-Newtonian effects. In general, shear-thinning/shear-thickening effects destabilize/stabilize the flow around the cylinder and in a lid driven cavity. Viscoelastic effects both stabilize and destabilize the channel flow depending on the ratio between the viscoelastic and flow time scales. The instability mechanism is just slightly modied in the cylinder flow whereas new instability mechanisms arise in the lid-driven cavity flow.

In the second part, we employ Direct Numerical Simulation together with an Immersed Boundary Method to simulate the inertial suspensions of rigid spherical neutrally buoyant particles in a channel. A wide range of the bulk Reynolds numbers, 500<Re<5000, and particle volume fractions, 0<\Phi<3, is studied while fixing the ratio between the channel height to particle diameter, 2h/d = 10. Three different inertial regimes are identied by studying the stress budget of two-phase flow. These regimes are laminar, turbulent and inertial shear-thickening where the contribution of the viscous, Reynolds and particle stress to transfer the momentum across the channel is the strongest respectively. In the inertial shear-thickening regime we observe a signicant enhancement in the wall shear stress attributed to an increment in particle stress and not the Reynolds stress. Examining the particle dynamics, particle distribution, dispersion, relative velocities and collision kernel, confirms the existence of the three regimes. We further study the transition and turbulence in the dilute regime of finite size particulate channel flow. We show that the turbulence can sustain in the domain at Reynolds numbers lower than the one of the unladen flow due to the disturbances induced by particles.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2015. x, 60 p.
Series
TRITA-MEK, ISSN 0348-467X
Keyword
non-Newtonian flow, global stability analysis, inertial suspensions, particle dynamics
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-177850 (URN)978-91-7595-782-1 (ISBN)
Public defence
2015-12-18, Kollegiesalen, Brinellvägen 8, KTH, Stockholm, 10:15 (English)
Opponent
Supervisors
Note

QC 20151127

Available from: 2015-11-27 Created: 2015-11-27 Last updated: 2015-11-27Bibliographically approved

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Brandt, Luca

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