Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Numerical analysis of the angular motion of a neutrally buoyant spheroid in shear flow at small Reynolds numbers
KTH, School of Engineering Sciences (SCI), Mechanics, Fluid Physics.ORCID iD: 0000-0002-2346-7063
KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
Show others and affiliations
2015 (English)In: Physical Review E. Statistical, Nonlinear, and Soft Matter Physics, ISSN 1539-3755, E-ISSN 1550-2376, Vol. 92, no 6, 063022Article in journal (Refereed) Published
Resource type
Text
Abstract [en]

We numerically analyze the rotation of a neutrally buoyant spheroid in a shear flow at small shear Reynolds number. Using direct numerical stability analysis of the coupled nonlinear particle-flow problem, we compute the linear stability of the log-rolling orbit at small shear Reynolds number Re-a. As Re-a -> 0 and as the box size of the system tends to infinity, we find good agreement between the numerical results and earlier analytical predictions valid to linear order in Re-a for the case of an unbounded shear. The numerical stability analysis indicates that there are substantial finite-size corrections to the analytical results obtained for the unbounded system. We also compare the analytical results to results of lattice Boltzmann simulations to analyze the stability of the tumbling orbit at shear Reynolds numbers of order unity. Theory for an unbounded system at infinitesimal shear Reynolds number predicts a bifurcation of the tumbling orbit at aspect ratio lambda(c) approximate to 0.137 below which tumbling is stable (as well as log rolling). The simulation results show a bifurcation line in the lambda-Re-a plane that reaches lambda approximate to 0.1275 at the smallest shear Reynolds number (Re-a = 1) at which we could simulate with the lattice Boltzmann code, in qualitative agreement with the analytical results.

Place, publisher, year, edition, pages
American Physical Society , 2015. Vol. 92, no 6, 063022
Keyword [en]
ELLIPSOIDAL PARTICLES, FLUID INERTIA, COUETTE FLOWS, DYNAMICS, TURBULENCE, ROTATION, ORIENTATION, FORCE
National Category
Fluid Mechanics and Acoustics
Identifiers
URN: urn:nbn:se:kth:diva-180597DOI: 10.1103/PhysRevE.92.063022ISI: 000367081600010Scopus ID: 2-s2.0-84954503118OAI: oai:DiVA.org:kth-180597DiVA: diva2:896194
Note

QC 20160120

Available from: 2016-01-20 Created: 2016-01-19 Last updated: 2016-09-29Bibliographically approved
In thesis
1. Angular dynamics of non-spherical particles in linear flows related to production of biobased materials
Open this publication in new window or tab >>Angular dynamics of non-spherical particles in linear flows related to production of biobased materials
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Dispersed particle flows are encountered in many biological, geophysical but also in industrial situations, e.g. during processing of materials. In these flows, the particles usually are non-spherical and their angular dynamics play a crucial role for the final material properties. Generally, the angular dynamics of a particle is dependent on the local flow in the frame-of-reference of this particle. In this frame, the surrounding flow can be linearized and the linear velocity gradient will determine how the particle rotates. In this thesis, the main objective is to improve the fundamental knowledge of the angular dynamics of non-spherical particles related to two specific biobased material processes.

Firstly, the flow of suspended cellulose fibers in a papermaking process is used as a motivation. In this process, strong shear rates close to walls and the size of the fibers motivates the study of inertial effects on a single particle in a simple shear flow. Through direct numerical simulations combined with a global stability analysis, this flow problem is approached and all stable rotational states are found for spheroidal particles with aspect ratios ranging from moderately slender fibers to thin disc-shaped particles.

The second material process of interest is the production of strong cellulose filaments produced through hydrodynamic alignment and assembly of cellulose nanofibrils (CNF). The flow in the preparation process and the small size of the particles motivates the study of alignment and rotary diffusion of CNF in a strain flow. However, since the particles are smaller than the wavelength of visible light, the dynamics of CNF is not easily captured with standard optical techniques. With a new flow-stop experiment, rotary diffusion of CNF is measured using Polarized optical microscopy. This process is found to be quite complicated, where short-range interactions between fibrils seem to play an important role. New time-resolved X-ray characterization techniques were used to target the underlying mechanisms, but are found to be limited by the strong degradation of CNF due to the radiation.

Although the results in this thesis have limited direct applicability, they provide important fundamental stepping stones towards the possibility to control fiber orientation in flows and can potentially lead to new tailor-made materials assembled from a nano-scale.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2016. 134 p.
Series
TRITA-MEK, ISSN 0348-467X ; 2016:14
Keyword
Fluid mechanics, dispersed particle flows, inertia, non-linear dynamics, rotary diffusion, characterization techniques
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-193124 (URN)978-91-7729-139-8 (ISBN)
Public defence
2016-10-28, F2, Lindstedsvägen 26, Stockholm, 10:30 (English)
Opponent
Supervisors
Note

QC 20160929

Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2016-09-29Bibliographically approved

Open Access in DiVA

No full text

Other links

Publisher's full textScopus

Search in DiVA

By author/editor
Rosen, TomasNordmark, ArneLundell, Fredrik
By organisation
Fluid PhysicsStructural MechanicsWallenberg Wood Science Center
In the same journal
Physical Review E. Statistical, Nonlinear, and Soft Matter Physics
Fluid Mechanics and Acoustics

Search outside of DiVA

GoogleGoogle Scholar

Altmetric score

Total: 145 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf