Identification of Lagrangian coherent structures around swimming jellyfish from experimental time-series data

Citation

Zhang, Zhonglin (2008) Identification of Lagrangian coherent structures around swimming jellyfish from experimental time-series data. Senior thesis (Minor), California Institute of Technology. http://resolver.caltech.edu/CaltechTHESIS:01152011-143930896

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Abstract

The unique body kinematics of jellyfish embodies the most intriguing form of biological propulsion, which makes jellyfish a promising resource for developing new locomotion systems. Instead of the conventional Eulerian method, we take an unprecedented Lagrangian approach by tracking individual fluid particles around a swimming jellyfish over a finite time interval. Specifically, we utilize the Lagrangian coherent structures (LCS) in the flow field to investigate the flow characteristics around a jellyfish. LCS are separatrices or invariant manifolds, which separate the flow field into distinct regions. To locate the LCS in the flow, we employ the concept of the finite-time Lyapunov Exponent (FTLE), which measures the rate at which particles diverge from each other, and LCS are identified as the high-value ridges in the FTLE field. This method is implemented and validated by analysis on two-dimensional vortex dipole flow, two-dimensional experimental time-series data, and Hill’s vortex sphere. This method is expected to extract LCS from three-dimensional experimental time-series data.

Item Type:	Thesis (Senior thesis (Minor))
Subject Keywords:	Lagrangian Coherent Structure; LCS; FTLE; finite-time Lyapunov Exponent; three-dimensional; 3D; vortex dipole; vortex flow; swimming jellyfish; graphical user interface
Degree Grantor:	California Institute of Technology
Division:	Engineering and Applied Science
Major Option:	Aeronautics
Minor Option:	Control and Dynamical Systems
Thesis Availability:	Public (worldwide access)
Research Advisor(s):	Dabiri, John O. (advisor) Murray, Richard M. (co-advisor)
Thesis Committee:	Unknown, Unknown
Defense Date:	8 June 2008
Record Number:	CaltechTHESIS:01152011-143930896
Persistent URL:	http://resolver.caltech.edu/CaltechTHESIS:01152011-143930896
Default Usage Policy:	No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:	6226
Collection:	CaltechTHESIS
Deposited By:	Zhonglin Zhang
Deposited On:	24 Jan 2011 13:37
Last Modified:	26 Dec 2012 04:32

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Identification of Lagrangian coherent structures around swimming jellyfish from experimental time-series data. (deposited 24 Jan 2011 13:37) [Currently Displayed]