Jakob Hærvig, On the Adhesive Behaviour of Micron-sized particles in Turbulent Flow

248 Pages·2017·19.42 MB·English

by  Jakob Hærvig

Aalborg Universitet

On the Adhesive Behaviour of Micron-sized Particles in Turbulent Flow
A Numerical Study Coupling the Discrete Element Method and Large Eddy Simulations
Hærvig, Jakob
DOI (link to publication from Publisher):
10.5278/vbn.phd.eng.00022
Publication date:
2017
Document Version
Publisher's PDF, also known as Version of record
Link to publication from Aalborg University
Citation for published version (APA):
Hærvig, J. (2017). On the Adhesive Behaviour of Micron-sized Particles in Turbulent Flow: A Numerical Study
Coupling the Discrete Element Method and Large Eddy Simulations. Aalborg Universitetsforlag. Ph.d.-serien for
Det Ingeniør- og Naturvidenskabelige Fakultet, Aalborg Universitet https://doi.org/10.5278/vbn.phd.eng.00022
General rights
Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners
and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.
- Users may download and print one copy of any publication from the public portal for the purpose of private study or research.
- You may not further distribute the material or use it for any profit-making activity or commercial gain
- You may freely distribute the URL identifying the publication in the public portal -
Take down policy
If you believe that this document breaches copyright please contact us at [email protected] providing details, and we will remove access to
the work immediately and investigate your claim.
Downloaded from vbn.aau.dk on: February 01, 2023

O
N
T
H
E
A
D
H
E
S
IV
E
B
E
H
A
V
IO
U
R
O
F
M
IC
ON THE ADHESIVE BEHAVIOUR OF MICRON-SIZED
R
O
N PARTICLES IN TURBULENT FLOW
-
S
IZ
E
D A NUMERICAL STUDY COUPLING THE DISCRETE ELEMENT
P
A METHOD AND LARGE EDDY SIMULATIONS
R
T
IC BY
L JAKOB HÆRVIG
E
S
IN
T DISSERTATION SUBMITTED 2017
U
R
B
U
L
E
N
T
F
L
O
W
J
A
K
O
B
H
Æ
R
V
IG

On the Adhesive Behaviour
of Micron-sized Particles in
Turbulent Flow
A Numerical Study Coupling the Discrete Element
Method and Large Eddy Simulations
Ph.D. Dissertation
Jakob Hærvig
DissertationsubmittedOctober2017
Dissertation submitted: October 2017
PhD supervisor: Assoc. Prof. Kim Sørensen
Aalborg University
Dissertationsubmitted: October2017
Assistant PhD supervisor: Assoc. Prof. Thomas J. Condra
PhDSupervisor: Assoc. Prof.KimSørensen
Aalborg University
AalborgUniversity
AssistantPhDSupervisor: Assoc. Prof.ThomasJ.Condra
PhD committee: Professor Søren Knudsen Kær (Chairman)
AalborgUniversity
Aalborg University
PhDCommittee: Prof. SørenK.Kær
PAraolfbeossrgorU Mnaivretirns iStyommerfeld
Otto-von-Guericke University Magdeburg
Prof.JeffreyS.Marshall
PUrnofiveessrsoirt yJeofffrVeeyr Sm.o Mntarshall
UPrnoivf.eDrsri.t-yI nogf. VMearmrtionntSommerfeld
OttovonGuerickeUniversityMagdeburg
PhDSeries: FacultyofEngineeringandScience,
PhD Series: Faculty of Engineering and Science, Aalborg University
AalborgUniversity
Department: Department of Energy Technology
IISSSSNN: (onxlxinxxe-)x: x2x4x46-1636
ISBN: xxx-xx-xxxx-xxx-x
ISBN (online): 978-87-7210-079-1
PPuubblliisshheedd bbyy::
AAaallbboorrgg UUnniivveerrssiittyy PPrreessss
SSkkjjeerrnnvveejj 44AA,,2 2nndd flfloooorr
DDKK –– 99222200A AaalblboorrggØ Ø
PPhhoonnee:: ++4455 9999440077114400
aaaauuff@@ffoorrllaagg.a.aaauu..ddkk
ffoorrllaagg..aaaauu..ddkk
© 2017JakobHærvig
© Copyright: Jakob Hærvig
PrintedinDenmarkbyRosendahls,2017
Printed in Denmark by Rosendahls, 2017
Standardpages: 243pages(2,400charactersincl. spaces).
This dissertation is typeset using LATEX2ε, plots are prepared using TikZ
anddrawingsareincludedbycombiningvectorgraphicswithLATEX-overlay
functionality.
Abstract
Small particles are commonly observed to stick to one another (typically de-
noted agglomerate) due to inter-particle attractive forces. When particles
agglomeratetheirinteractionwiththesurroundingsischangedsignificantly.
Particles with this behaviour are found in wide range of processes ranging
fromdustparticlesinspace,thatagglomeratetoformearlystagesofplanets,
to soot particles emitted from various combustion processes on Earth that
reducetheefficiencyofvariousindustrialprocessesbystickingtosurfaces.
Most particles influenced by inter-particle attractive forces have diame-
ters ranging from d = O(0.1µm) to d = O(10µm). Due to their small
p p
size,experimentalinvestigationsarelimitedtosingleparticlescollidingwith
a surface under well-controlled conditions. When adhesive particles interact
in a turbulent flow, tracking individual particles in time becomes close to
impossible. Due to the difficulties with tracking adhesive particles experi-
mentally,computationalmethodswithvaryinglevelofcomplexityhavebeen
developed over the last decades. Recent development within computational
methods, such as the Discrete Element Method (DEM), allow more aspects
of the agglomeration process to be resolved directly based on the properties
of the particles. Despite the increase in computational power in the recent
years, simulating the interaction of thousands, millions or even billions par-
ticlesremainslimitedbythecomputationalpowerofmoderncomputers.
Inthisstudy,focusisfirstonhowtoanalyticallyderiveacriteriondescrib-
ing how to effectively speed up DEM simulations by altering the physical
propertiesoftheparticles. Forthispurpose,simulationsinvolvingtwoparti-
clescollidingundervariousconditionsarecarriedouttoensuretheadhesive
behaviour remains unchanged after applying the criterion. In conjunction
with the criterion proposed, a relation describing the computational speed-
upisproposed.
Secondly, focus is on applying the criterion to investigate how adhesive
particles interact in a turbulent pipe flow by coupling Large Eddy Simula-
tions(LES)ofturbulentflowtotheDiscreteElementMethod(DEM).Initially,
simulations are done to verify the validity of the analytically-derived crite-
rion. Next,simulationsaredoneforawiderangeofparticlepropertiestoget
iii
a better understanding of how particle properties affect the agglomeration
anddepositionprocess.
Even though this dissertation is part of a project with focus on how soot
particles agglomerate and deposit on heat exchanger surfaces, the work re-
portedhereisgenerallyapplicabletoamuchwiderrangeofproblems.
JakobHærvig
AalborgUniversity
Resumé
Småpartiklersesofteklæbesigtilhinanden,hvilketkanforklaresvedhjælp
af tiltrækningskræfter, der virker mellem partiklerne. Når partikler klistrer
sig til hinanden, ændrer det på måden, hvormed de interagerer med deres
omgivelser. Partikler med denne adfærd kan observeres i en lang række
tilfælde, som blandt andet inkluderer partikler i rummet, der danner tidlige
stadierafnyeplanetersamtsodpartiklerfraforbrændingsprocesser,somsæt-
tersigpåoverfladerogreducervirkningsgradenafenlangrækkeindustrielle
processer.
Partikler med adfærd påvirket af tiltrækningskræfter er typisk i stør-
relsesordenen d = O(0.1µm) til d = O(10µm). Grundet den lille stør-
p p
relseerderkunudførtyderstvelkontrolleredeforsøg,somomhandler,hvor-
dan enkelte partikler rammer en overflade. Hvis man ydermere er inter-
esseret i at følge enkelte partikler i en turbulent strømning, er dette tæt på
umuligt. Grundet vanskelighederne med at følge enkelte partikler er der
gennem de sidste årtier blevet udviklet forskellige beregningsmetoder med
varierende kompleksitet. Nylige beregningsmetoder inkluderer Discrete El-
ement Metoden (DEM), som baserer sig direkte på partiklernes egenskaber
foratopløse,hvordanpartiklerkolliderer. AfdennegrundegnerDEMsigtil
beregningsmæssigt at forudsige alle stadier af, hvordan partikler sætter sig
sammen. På trods af en stigning i beregningskraft i de senere år, begrænses
simuleringer af tusind, millioner eller milliarder af partikler dog stadig af
beregningskraft.
I denne afhandling udledes der indledningsvist et analytisk udtryk for,
hvordan beregningstiden kan nedbringes betydeligt ved at ændre på par-
tiklernes egenskaber. I denne forbindelse simuleres først partikelkollisioner
med to partikler under forskellige forhold for at sikre, at resultatet af kol-
lisionen ikke ændrer sig, når det analytiske udtryk anvendes. Udover det
analytiske udtryk udledes i afhandlingen et udtryk for, hvor meget beregn-
ingstidenkannedbringes.
Derefter anvendes det udledte udtryk til numerisk at koble Large Eddy
Simuleringer (LES) til Discrete Element Metoden (DEM) for at undersøge,
hvordan partikler klæber til hinanden i turbulente strømninger. Først verifi-
v
ceres det, at udtrykket udledt i den første del er gældende. Dernæst bliver
derudførtsimuleringermedenlangrækkepartikler,derhartilformålatgive
en bedre forståelse for, hvordan partiklernes egenskaber påvirker processen,
hvorpåpartiklerklæbersigtilhinanden.
Selvom denne afhandling er del af et projekt, hvor fokus er på, hvordan
sodpartikler sætter sig på varmevekslerflader, er de rapporterede resultater
genereltanvendeligeienlangrækkeandretilfælde.
JakobHærvig
AalborgUniversitet