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Unsteady Fluid Mechanics of Starting-Flow Vortex Generators with Time-Dependent Boundary Conditions


Dabiri, John Oluseun (2005) Unsteady Fluid Mechanics of Starting-Flow Vortex Generators with Time-Dependent Boundary Conditions. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/QV8Y-YZ12.


Nature has repeatedly converged on the use of starting flows for mass, momentum, and energy transport. The vortex loops that form during flow initiation have been reproduced in the laboratory and have been shown to make a proportionally larger contribution to fluid transport than an equivalent steady jet. However, physical processes limit growth of the vortex loops, suggesting that these flows may be amenable to optimization. Although it has been speculated that optimal vortex formation might occur naturally in biological systems, previous efforts to quantify the biological mechanisms of vortex formation have been inconclusive. In addition, the unsteady fluid dynamical effects associated with starting flow vortex generators are poorly understood.

This thesis describes a combination of new experimental techniques and in vivo animal measurements that determine the effects of fluid-structure interactions on vortex formation by starting flow propulsors. Results indicate that vortex formation across various biological systems is manipulated by these kinematics in order to maximize thrust and/or propulsive efficiency. An emphasis on observed vortex dynamics and transient boundary conditions facilitates quantitative comparisons across fluid transport schemes, irrespective of their individual biological functions and physical scales.

The primary contributions of this thesis are the achievement of quantitative measures of unsteady vortex dynamics via fluid entrainment and added-mass effects, and the development of a robust framework to facilitate the discovery of general design principles for effective fluid transport in engineering technologies and biological therapies. The utility of this new research paradigm is demonstrated through a variety of examples.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:biological flows; cardiovascular flows; locomotion; vortex dynamics
Degree Grantor:California Institute of Technology
Division:Engineering and Applied Science
Major Option:Bioengineering
Minor Option:Aeronautics
Awards:Alan T. Waterman Award (NSF), 2020. MacArthur Fellow, 2010. Donald Coles Prize in Aeronautics, 2005.
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Gharib, Morteza
Thesis Committee:
  • Gharib, Morteza (chair)
  • Leonard, Anthony
  • Pullin, Dale Ian
  • Burdick, Joel Wakeman
  • Brady, John F.
  • Dickinson, Michael H.
Defense Date:8 April 2005
Record Number:CaltechETD:etd-04112005-151435
Persistent URL:
Dabiri, John Oluseun0000-0002-6722-9008
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:1343
Deposited By: Imported from ETD-db
Deposited On:15 Apr 2005
Last Modified:09 Aug 2022 17:17

Thesis Files

PDF (jodabiri_thesis.pdf) - Final Version
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