Anderson Thesis

245 Pages·2007·10.21 MB·English

ADVANCES IN THE VISUALIZATION AND ANALYSIS OF
BOUNDARY LAYER now IN SWIMMING FISH
BY
Erik J. Anderson
M.S., Saint Francis Xavier University, 1998
B.S., Gordon College, 1989
Submitted in partial fulfillment of the requirements for the degree of
Doctor of Philosophy
at the
MASSACHUSETTS INSTITUTE OF TECHNOLOGY
and the
WOODS HOLE OCEANOGRAPHIC INSTmJTION
February 2005
O 2005 Erik J. Anderson. All rights reserved.
The author hereby grants to
electronic copies of this thes
Signature of Author
assachusetts Institute of Technology
oods Hole Oceanographic Institution
Certified by
Mark A. Grosenbaugh
Thesis supervis&
Certified by
Wade R. McGillis
Thesis Supervisor
Certified by
/ Mark A. Grosenbaugh
Chairman, Joint Committee for Applied Ocean Science and Engineering
Woods Hole Oceanographic Institution
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Advances in the visualization and analysis of boundary layer flow in swimming fish
BY
Erik J. Anderson
Abstract
In biology, the importance of fluid drag, diffusion, and heat transfer both internally and
externally, suggest the boundary layer as an important subject of investigation, however,
the complexities of biologcal systems present significant and unique challenges to
analysis by experimental fluid dynamics. In this investigation, a system for automatically
profiling the boundary layer over free-swimming, deforming bodies was developed and
the boundary layer over rigid and live mackerel, bluefish, scup and eel was profiled. The
profiling system combined robotics, particle imaging velocimetry, a custom particle
tracking code, and an automatic boundary layer analysis code. Over 100,000 image pairs
of flow in the boundary layer were acquired in swimming fish alone, making spatial and
temporal ensemble averaging possible.
A flat plate boundary layer was profiled and compared to known laminar and turbulent
boundary layer theory. In general, profiles resembled those of Blasius for sub-critical
length Reynolds numbers, Re,. Transition to a turbulent boundary layer was observed
near the expected critical Re, and subsequent profiles agreed well with the law of the
wall. The flat plate analysis demonstrated that the particle tracking and boundary layer
analysis algorithms were highly accurate.
In rigid fish, separation of flow was clearly evident and the boundary layer transitioned to
turbulent at lower Re, than in swimming fish and the flat plate. Wall shear stress, z,,
forward of separation was slightly higher than flat plate values. Friction drag in rigid and
swimming fish was determined by integrating z, over the surface of the fish. The
analysis was facilitated by the definition of the relative local coefficient of friction. In
general, there was no.s ignificant difference in friction drag between the rigid-body and
swimming cases. In swimming, separation was, on average, delayed. Therefore,
pressure drag was estimated on the basis of thickness ratio and used to calculate an
upper-bound total drag on a swimming fish. Total drag was used to determine the
required muscle power output during swimming and compare that with existing muscle
power data. z, and boundary layer thickness oscillated with undulatory phase. The
magnitude of oscillation appears to be linked to body wave amplitude.
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Contents
1. Acknowledgements
..
11. List of figures
iii, List of tables
iv. List of symbols
1 Introduction
1.1 Definition of a boundary layer
1.2 History of boundary layer studies in fish swimming
1.3 The problem and history of drag measurement in undulatory swimming
1.4 Contribution of the present investigation
1.5 Chapter preview
2 Boundary layer theory
2.1 Laminar boundary layer solutions
2.2 Length Reynolds number, Re,
2.3 Falkner-Skan laminar boundary layer solution
2.4 Turbulent boundary layer equations
2.5 The 117~p~ow er turbulent boundary layer profile approximation
2.6 Turbulence intensity
2.7 Boundary layer thickness
2.8 Wall shear stress and friction drag
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3 Preliminary investigation
3.1 Methods and materials
3.1.1 Fish
3.1.2 Swimming conditions
3.1.3 Image acquisition
3.1.4 Rigid-body drag
3.1.5 Digital particle tracking velocimetry
3.1.6 Tangential and normal velocity calculations
3.1.7 DPTV errors
3.1.8 Undulatory phase
3.2 Results
3.2.1 Fish boundary layer profiles
3.2.2 Flow condition in the boundary layer
3.2.3 Local friction coefficients
3.2.4 Oscillatory behavior of the boundary layer
3.2.5 Oscillation of normal velocity
3.2.6 Incipient separation
3.2.7 Total skin friction and friction coefficients
3.3 Discussion
3.3.1 The nature of the fish boundary layer
3.3.2 Wave-like distributions of boundary layer variables and pressure
3.3.3 Drag enhancement and drag reduction
3.3.4 Drag reduction mechanisms
3.3.5 Two-dimensional analysis of a three-dimensional phenomenon
3.3.6 Power to overcome friction drag
3.3.7 The advantages of boundary layer visualization
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4 Advances data acquisition
4.1 Specimens and trials
4.2 Specimen collection and care
4.3 Flume test section
4.4 Strobe imaging of the flow
4.5 Robotic control of data acquisition
4.6 Automatic calibration
4.7 Automatic scanning of long video records for usable data
5 Automatic boundary layer PTV and analysis
5.1 The failure of conventional DPIV and DPTV to resolve the boundary layer
5.2 An automatic boundary layer profiling and analysis code
5.2.1 Automatic object surface edge detection
5.2.2 Surface tracking
5.2.3 Surface and glare removal
5.2.4 Particle centroiding
5.2.5 Particle tracking by track convergence velacimetry
5.3 Boundary layer profile calculation
5.4 Boundary layer profile andysis
5.5 The relative, local drag coefficient
5.6 Errors in the calculation of boundary layer parameters
5.7 Criteria for accurate boundary layer data
5.8 Undulatory phase
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6 Experimental controls: flume profile, flat plate, rigid fish
6.1 Flume profile
6.1.1 Flume wall boundary layers
6.1.2 Flume plug flow
6.1.3 Fluctuations of streamwise velocity in the plug flow
6.1.4 Summary of flume profile analysis
6.2 Flat plate boundary layer
6.2.1 Details of the flat plate experiments
6.2.2 The flat plate coordinate system
6.2.3 Comparison of upstteam profile with flume plug profile
6.2.4 General observations of the flat plate boundary layer
6.2.5 Boundary layer thickness
6.2.6 Errors in estimating velocity gradient at the plate surface
6.2.7 Velocity gradient and local coefficient of friction on the flat plate
6.2.8 Relative local coefficient of friction, C', on the flat plate
6.3 Boundary layer flow over rigid fish
6.3.1 Boundary layer separation in rigid fish
6.3.2 Early transition to a turbulent boundary layer
6.3.3 Friction on a rigid fish
7 The boundary layer of swimming fish
7.1 Body wave amplitude and frequency
7.2 The bluefish boundary layer
7.2.1 Bluefish boundary layer thickness
7.2.2 Bluefish boundary layer local coefficient of friction
7.2.3 Significance of bluefish boundary layer findings
7.3 The scup boundary layer
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7.3.1 Scup boundary layer thickness
7.3.2 Scup boundary layer local coefficient of friction
7.3.3 Significance of scup boundary layer findings
7.4 The eel boundary layer
7.4.1 Eel boundary layer thickness
7.4.2 Eel boundary layer local coefficient of friction
7.4.3 Significance of eel boundary layer findings
7.5 The mackerel boundary layer
7.5.1 Mackerel boundary layer thickness
7.5.2 Mackerel boundary layer local coefficient of friction
7.5.3 Significance of mackerel boundary layer findings
7.6 Drag and power in swimming fish
7.6.1 Comparison of local friction in rigid and swimming fish
7.6.2 Total friction coefficients and total friction drag on swimming fish
7.6.3 Estimated pressure drag and an upper-bound overall drag
7.6.4 Power requirements and available muscle power
8 Conclusions and suggestions for future work
8.1 The boundary layer of swimming fish
8.2 The drag on swimming fish
8.3 Improvements in boundary layer profiling
8.3.1 Improved temporal and spatial resolution
8.3.2 Machine vision
8.4 Boundary layers in biology-a new frontier
References
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