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Identification of Lagrangian Coherent Structures Around Swimming Jellyfish from Experimental Time-Series Data


Zhang, Zhonglin Johnny (2008) Identification of Lagrangian Coherent Structures Around Swimming Jellyfish from Experimental Time-Series Data. Senior thesis (Minor), California Institute of Technology. doi:10.7907/KK45-ZV02.


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:01112018-113614173
Persistent URL:
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:10642
Deposited By: Kathy Johnson
Deposited On:11 Jan 2018 19:38
Last Modified:26 Nov 2019 21:33

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