Advanced

Methods for Vortex Identification

Holmén, Vivianne LU (2012) In Master’s Theses in Mathematical Sciences FMA820 20121
Mathematics (Faculty of Technology) and Numerical Analysis
Abstract
Initially, this paper presents an overview of the existing methods used for the identification of vortices in fluids, attempting to point out their different strengths and weaknesses. In addition, a new method is proposed to identify vortices directly from velocity field information. It defines a point inside a vortex as a point around which there is rotation. By looking at the velocity directions in the neighbourhood of a point we decide if there is rotation. A measure of the strength of rotation at the point is also introduced based on the magnitude of the velocity components in the neighbourhood. The method is tested on simulated data and performs well. Finally a Lagrangian identification method (Direct Lyapunov Exponents, DLE) is used... (More)
Initially, this paper presents an overview of the existing methods used for the identification of vortices in fluids, attempting to point out their different strengths and weaknesses. In addition, a new method is proposed to identify vortices directly from velocity field information. It defines a point inside a vortex as a point around which there is rotation. By looking at the velocity directions in the neighbourhood of a point we decide if there is rotation. A measure of the strength of rotation at the point is also introduced based on the magnitude of the velocity components in the neighbourhood. The method is tested on simulated data and performs well. Finally a Lagrangian identification method (Direct Lyapunov Exponents, DLE) is used to attempt to calibrate the most widely used Eulerian method in order to match an objectively defined edge. The results here indicate that it might not be possible to find a threshold for this method to match the edges found using the DLE method. (Less)
Please use this url to cite or link to this publication:
author
Holmén, Vivianne LU
supervisor
organization
course
FMA820 20121
year
type
H2 - Master's Degree (Two Years)
subject
publication/series
Master’s Theses in Mathematical Sciences
report number
LUTFMA-3239-2012
ISSN
1404-6342
other publication id
2012:E47
language
English
id
3241710
date added to LUP
2014-06-27 17:33:40
date last changed
2014-06-27 17:33:40
@misc{3241710,
  abstract     = {Initially, this paper presents an overview of the existing methods used for the identification of vortices in fluids, attempting to point out their different strengths and weaknesses. In addition, a new method is proposed to identify vortices directly from velocity field information. It defines a point inside a vortex as a point around which there is rotation. By looking at the velocity directions in the neighbourhood of a point we decide if there is rotation. A measure of the strength of rotation at the point is also introduced based on the magnitude of the velocity components in the neighbourhood. The method is tested on simulated data and performs well. Finally a Lagrangian identification method (Direct Lyapunov Exponents, DLE) is used to attempt to calibrate the most widely used Eulerian method in order to match an objectively defined edge. The results here indicate that it might not be possible to find a threshold for this method to match the edges found using the DLE method.},
  author       = {Holmén, Vivianne},
  issn         = {1404-6342},
  language     = {eng},
  note         = {Student Paper},
  series       = {Master’s Theses in Mathematical Sciences},
  title        = {Methods for Vortex Identification},
  year         = {2012},
}