• English
    • svenska
  • English 
    • English
    • svenska
  • Login
View Item 
  •   Home
  • Faculty of Science / Naturvetenskapliga fakulteten
  • Department of Physics / Institutionen för fysik
  • Doctoral Theses / Doktorsavhandlingar Institutionen för fysik
  • View Item
  •   Home
  • Faculty of Science / Naturvetenskapliga fakulteten
  • Department of Physics / Institutionen för fysik
  • Doctoral Theses / Doktorsavhandlingar Institutionen för fysik
  • View Item
JavaScript is disabled for your browser. Some features of this site may not work without it.

Angular dynamics of small particles in fluids

Abstract
This thesis concerns the angular motion of small particles suspended in fluid flows. A small particle experiences a hydrodynamic torque due to the local fluid velocity, and this torque leads to rotational motion. When inertial effects are negligible the torque on an ellipsoidal particle is given by Jeffery's theory [Jeffery, G. B. Proc. R. Soc. Lond. A 102, 161–179 (1922)]. In this thesis and the appended papers I describe three studies that all relate to this well-known result. First, we derive an effective equation of motion for the orientation of a spheroid in a simple shear flow, valid for small values of the shear Reynolds number $\textrm{Re}_s=sa^2/\nu$, where $s$ is the shear rate, $a$ the particle size and $\nu$ the kinematic viscosity of the suspending fluid. In absence of inertia the equation of motion has infinitely many periodic solutions, the 'Jeffery orbits'. We show how this degeneracy is lifted by the effects of inertia. Second, we describe experimental observations of the orientational dynamics of asymmetric particles advected in a microchannel. We record several trajectories with each particle by resetting the initial condition with an optical trap. We find that the dynamics depend sensitively on both particle shape and initial conditions. This confirms earlier theoretical results, which are also described in this thesis. Third, we discuss the angular dynamics of axisymmetric particles in turbulent and random flow. In these flows the statistical averages of the angular dynamical quantities depend crucially on the intricate correlations between the particle orientation, angular velocity, and the flow vorticity relative to the principal straining directions of the fluid flow. We illustrate this by direct numerical simulation, experimental measurements and statistical model calculations. Finally, this thesis contains an introduction to the field aimed at new students, as well as an accessible popular science introduction to low Reynolds particle dynamics.
Parts of work
Paper A: Effect of weak fluid inertia upon Jeffery orbits, J. Einarsson, F. Candelier, F. Lundell, J. R. Angilella, and B. Mehlig, Phys. Rev. E 91, 041002(R) (2015) ::doi::10.1103/PhysRevE.91.041002
 
Paper B: Role of inertia for the rotation of a nearly spherical particle in a general linear flow, F. Candelier, J. Einarsson, F. Lundell, B. Mehlig, and J.-R. Angilella, Phys. Rev. E 91, 053023 (2015) ::doi::10.1103/PhysRevE.91.053023
 
Paper C: Rotation of a spheroid in a simple shear at small Reynolds number, J. Einarsson, F. Candelier, F. Lundell, J. R. Angilella and B. Mehlig, Phys. Fluids 27, 063301 (2015) ::doi::10.1063/1.4921543
 
Paper D: Numerical analysis of the angular motion of a neutrally buoyant spheroid in shear flow at small Reynolds numbers, T. Rosen, J. Einarsson, A. Nordmark, C. K. Aidun, F. Lundell, B. Mehlig, in review Physical Review E (2015) arXiv:1508.04976
 
Paper E: Tumbling of asymmetric microrods in a microchannel flow, J. Einarsson, B. M. Mihiretie, A. Laas, S. Ankardal, J. R. Angilella, D. Hanstorp, B. Mehlig, in review Physics of Fluids (2015) (arXiv:1503.03023)
 
Paper F: Shape-dependence of particle rotation in isotropic turbulence, M. Byron, J. Einarsson, K. Gustavsson, G. Voth, B. Mehlig and E. Variano, Phys. Fluids 27, 035101 (2015) ::doi::10.1063/1.4913501
 
Degree
Doctor of Philosophy
University
Göteborgs universitet. Naturvetenskapliga fakulteten
Institution
Department of Physics ; Institutionen för fysik
Disputation
Dec. 14, 2015. 09:00 in PJ-salen, Fysikgården 2, Göteborg
Date of defence
2015-12-14
E-mail
jonas.einarsson@gmail.com
jonas.einarsson@physics.gu.se
URI
http://hdl.handle.net/2077/40830
Collections
  • Doctoral Theses / Doktorsavhandlingar Institutionen för fysik
  • Doctoral Theses from University of Gothenburg / Doktorsavhandlingar från Göteborgs universitet
View/Open
Thesis announcement (spikblad) (73.16Kb)
Thesis (without appended papers) (8.272Mb)
Date
2015-11-20
Author
Einarsson, Jonas
Keywords
Fluid mechanics
Particle dynamics
Multi-phase flow
Publication type
Doctoral thesis
ISBN
978-91-628-9656-0
978-91-628-9657-7
Language
eng
Metadata
Show full item record

DSpace software copyright © 2002-2016  DuraSpace
Contact Us | Send Feedback
Theme by 
Atmire NV
 

 

Browse

All of DSpaceCommunities & CollectionsBy Issue DateAuthorsTitlesSubjectsThis CollectionBy Issue DateAuthorsTitlesSubjects

My Account

LoginRegister

DSpace software copyright © 2002-2016  DuraSpace
Contact Us | Send Feedback
Theme by 
Atmire NV