Title page for ETD etd-06172005-114444

Type of Document Master's Thesis
Author Linklater, Amy Catherine
Author's Email Address alinklat@vt.edu
URN etd-06172005-114444
Title Design and Simulation of a Towed Underwater Vehicle
Degree Master of Science
Department Aerospace and Ocean Engineering
Advisory Committee
Advisor Name Title
Woolsey, Craig A. Committee Chair
McCue-Weil, Leigh S. Committee Member
Neu, Wayne L. Committee Member
  • Towfish
  • Dynamic Modeling
  • Underwater Vehicle
  • Towed Vehicle
Date of Defense 2005-06-03
Availability unrestricted
Oceanographers are currently investigating small-scale ocean turbulence to understand how to better model the ocean. To measure ocean turbulence, one must measure fluid velocity with great precision. The three components of velocity can be used to compute the turbulent kinetic energy dissipation rate. Fluid velocity can be measured using a five-beam acoustic Doppler current profiler (VADCP). The VADCP needs to maintain a tilt-free attitude so the turbulent kinetic energy dissipation rate can be accurately computed to observe small-scale ocean turbulence in a vertical column.

To provide attitude stability, the sensor may be towed behind a research vessel, with a depressor fixed somewhere along the length of the towing cable. This type of setup is known as a two-part towing arrangement.

This thesis examines the dynamics, stability and control of the two-part tow. A Simulink simulation that models the towfish dynamics was implemented. Through this Simulink simulation a parametric study was conducted to see the effects of sea state, towing speed, center of gravity position, and a PID controller on the towfish dynamics. A detailed static analysis of the towing cable’s effects on the towfish enhanced this dynamic model. The thesis also describes vehicle design and fabrication, including procedures for trimming and ballasting the towfish.

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