Thesis
Tracking of manifolds and coherent structures in flows: simulations and experiments
Master of Science (M.S.), Drexel University
Jun 2014
DOI:
https://doi.org/10.17918/etd-4483
Abstract
There has been a significant recent interest in using autonomous vehicles to study phenomena in the ocean including temperature and salinity profiles, contaminant transport, and biological processes such as plankton assemblages and algae blooms. It is challenging to deploy mobile robots with bounded actuation and limited communication in a highly nonlinear, time varying, and stochastic flow field such as the ocean. Despite natural stochasticity and arbitrary time dependence, geophysical flows do admit persistent transport controlling features known as Lagrangian coherent structures. These structures, which behave similarly to stable and unstable manifolds in time invariant dynamical systems, serve to characterize transport phenomena and have been shown to have many useful properties for ocean sampling and efficient navigation. In this work, a strategy for tracking manifolds of 2D conservative vector fields is described and the application of this strategy to track coherent structures in general time dependent flows is presented. Computer simulations of the tracking strategy on a variety of analytical and measured flow fields are presented, and it is shown that, in many cases, the strategy is capable of successfully tracking coherent structures in simulation. In addition, the development of an experimental testbed consisting of a fleet of small autonomous surface vessels and three flow tanks is described. Preliminary experimental results related to tracking coherent structures using this flow testbed are presented. The overall results of this effort have indicated that the tracking strategy, although designed for time invariant flows, can be used to track coherent structures in certain time dependent flows quite reliably.
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Details
- Title
- Tracking of manifolds and coherent structures in flows
- Creators
- Matt Michini - DU
- Contributors
- M. Ani Hsieh (Advisor) - Drexel University (1970-)
- Awarding Institution
- Drexel University
- Degree Awarded
- Master of Science (M.S.)
- Publisher
- Drexel University; Philadelphia, Pennsylvania
- Resource Type
- Thesis
- Language
- English
- Academic Unit
- College of Engineering (1970-2026); Mechanical Engineering (and Mechanics) (1970-2026); Drexel University
- Other Identifier
- 4483; 991014632824204721