Estimation and Enhancement of Hydrodynamic Performance of Bio-Inspired Underwater Propulsion
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Authors
Gulsacan, Burak
Issue Date
2025
Type
Dissertation
Language
en_US
Keywords
bio-inspired propulsion , cantilever plates , hydrodynamic force
Alternative Title
Abstract
Fluid-structure interaction (FSI) research plays a pivotal role in the field of biomimeticand bio-inspired underwater propulsion in soft robotics, towards enhancing hydrodynamic
performance, maneuverability, and energy efficiency of underwater vehicles for exploration,
defense, and resource prospecting. In this project, we focus on the study and understanding
of the fundamental physical mechanisms of a novel paradigm of bio-inspired underwater
robotic propulsion based on the transformative concept of active stiffness and shapemorphing.
Our aim is to formalize a comprehensive experimental and computational framework
to shed light on the complex interplay of unsteady fluid flows and dynamically morphing
structures.
Chapter 1 introduces the study of biomimetic propulsion in underwater soft robotics,
where we highlight the approaches used to investigate the relevant FSI modeling. We present
a literature review of the mechanisms that FSI community has intensively studied. Finally,
the goals of the project, thesis outline, and document organization are concisely introduced.
In Chapter 2, we present a comprehensive experimental study on harmonic oscillations
of rigid plates with H-shaped cross sections submerged in stationary fluid environment. We
conduct a detailed experimental investigation of the flow physics created by the presence of
the flanges, that is, the vertical segments in the plate cross section. We perform particle image
velocimetry (PIV) experiments over a broad range of oscillation amplitudes, frequencies, and
flange size to width ratios by leveraging the identification of pathlines, vortex shedding and
dynamics, distinctive hydrodynamic regimes, and steady streaming.
Chapter 3 introduces a new nonlocal hydrodynamic theory for fluid-structure interactions
of cantilever beams and plates undergoing small amplitude vibrations in quiescent, Newtonian,
incompressible, viscous fluids. Our approach is based on a rigorous, yet efficient, 3D
treatment of the hydrodynamic loading on cantilevered thin structures. The off-line solution
of the FSI problem results in the so-called nonlocal modal hydrodynamic function matrix,that is, the representation of the nonlocal hydrodynamic load operator on a basis formed by
the structural modes. Our theory then integrates the nonlocal hydrodynamics within a fully
coupled structural modal model in the frequency domain. We compare and discuss our theory
predictions with the predictions of the classical local approaches, for different actuation
scenarios, identifying the limitations of the existing treatments. For clarity of presentation,
torsional vibrations of cantilever beams are investigated in a separate study, in Chapter 4,
due to technical differences in the treatment of the problem.
Chapter 5 presents an experimental study to investigate the effects of shape-morphing on
the flow physics of an oscillating submerged plate in a quiescent, incompressible, Newtonian
viscous fluid. This is the first soft robotic setup in which we implement and demonstrate
a time varying underwater shape-morphing deformation. With PIV and force measurement
via a load cell, we demonstrate that shape-morphing significantly results in reducing vortex
shedding intensity, minimizing hydrodynamic forces, and lowering energy dissipation.
In Chapter 6, we summarize the completed work on the vibration characteristics of
a plate oscillating in-air and in-vacuo. First, the concept of curvature-based stiffening is
introduced, which serves as a method to arbitrarily tune the stiffness and natural frequencies
of a microplate sensor for atomic force microscope applications. We perform a macroscale
experiment to verify the feasibility of this method. For our project, curvature-based stiffening
provides a preliminary perspective for active shape-morphing. The second part of Chapter 6
discusses the nonlinear vibration behavior of a shape-morphing cantilever plate excited by
base acceleration and time varying shape-morphing deformation. The interplay of these
motions causes the system to demonstrate distinctive and tunable nonlinear behavior. We
present frequency responses based on a finite element parametric study of the actuation
parameters, and propose a minimal modeling of the system based on the Duffing oscillator.
Chapter 7 summarizes this dissertation and my contributions to the project. Finally, the
chapter outlines future work for other researchers in our community.