Advisors: Dr. Manish Paliwal and Dr. Lisa Grega
Kevin Hynes
David Talarico
• At the current time, we have used somewhere around half of
the earth’s natural supply of fossil fuels
• How will we continue to supply society with the energy it
needs to function?
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1 in 4 people in
the world live
without electricity
This energy
poverty is the
biggest limitation
to improving
living conditions
Need for a cheap
open source
design
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Blades spin a
central shaft
Shaft runs to a
gearbox
Gearbox steps
up shaft speed
to 60Hz in
generator
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Use linear, oscillatory movement to improve wind
energy capture technology in one or more of the
following categories:
 Overall efficiency
 Energy produced per dollar input
 Energy produced per unit area of land used
Design a system that exploits rather than mitigates
vortex energy
Make design as simple and modular as possible
 Lower shipping and maintenance costs
 Opening the door to ‘open source’ use
Use vibrational modeling to widen range of resonant
behavior
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Drucker E G , Lauder G V Integr. Comp. Biol. 2002;42:243-257
Forces exerted on cylinder
only from vortex shedding
Forces exerted on airfoil to
due pressure differential
(lift) as well as vortex
formation and shedding
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‘Synchronization’ of a vibrational system occurs where driving frequency
approaches natural frequency
Mass ratio defined as m* = mass of system/mass of displaced fluid
Plot of oscillatory frequency vs.
This occurs over a large range of flow speeds if the mass ratio is
very low
Low mass ratio allows the system to respond more quickly
E. Swanton, B. Vanier, and K. Mohseni, Leading Edge
Vortex Stability in a Flapping Model Hummingbird
Wing, 38th Fluid Dynamics Conference and Exhibit,
AIAA paper 2008-3718, Seattle, OR, June 23-26, 2008.
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‘Delayed Stall’
Proves concept that a leading edge vortex (LEV) provides an
additional lift force during the time that it remains in contact with
the wing
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Kinsey and Dumas 2008
Pitching- rotational
movement of wing
Plungingtranslational
movement of wing
Coupling these two
motions will allow
the design of a system
that can extract flow
energy through lift
and vortex formation
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Plunge Amplitude
(Ho)
Pitch Amplitude
(θo)
Effective angle of
attack (α)
Chord Length (c)
Airfoil Thickness
Pitching Center
Frequency of
Oscillation
Flow Speed (U∞)
Motion
characteristics
Vibration constants
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Reduced frequency = f* = fc/U∞
Thickness has a negligible effect on efficiency
Our Design: More flexibility on selection of airfoil
design
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Optimal
pitching center
location found
to be 1/3
Efficiency
increases with
Reynolds
number
Our Design
Re~30,000
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Sine curve is
position vs. time
Slope is velocity
Resultant of lift and
drag resolved into X
and Y components
Power vs.
Propulsion
 Effective angle of
attack
 Y-component in
phase with
velocity
Quasi-steady
assumption
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Propulsion = High energy wake
Power extraction = Low Energy wake
Our Design: Must keep Y-component of force in phase with velocity
“Energy Harvesting through Flow-Induced Oscillations of a Foil”
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A ‘Leading Edge Vortex’ (LEV) is formed at the leading edge of an airfoil
that is about to undergo flow separation
LEV energy can be recovered at the trailing edge – depends on LEV-foil
interaction and timing
This occurs over a large range of flow speeds at a low mass ratio
Unsteady phenomenon
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Leading Edge
Vortex
Synchronization
(LEVS) dependent
on maximum
pitching amplitude
and reduced
frequency
Optimal pitching
amplitude ~ 75°
Optimal reduced
frequency ~ 0.15
Our Design: Use as
baseline
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What is the most efficient form of movement?
- Power extraction dominated by vertical force in phase with
vertical velocity
- Square wave ensures that the movement of the wing spends the
most time in the power stroke, highlighted below, where the Ycomponent of force and velocity are both at their maximum
- ‘Power Strokes’ ended by rapid pitching of airfoil and change in
vertical direction
Sinusoidal vs. Non-Sinusoidal (Square Wave) Oscillation
“Extracting Power from the Jet Stream: Pushing the Performance of Flapping Wing Technology” Platzer et. al.
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Mass ratio of wing must be very low
Thickness has a negligible effect on efficiency
Optimal pitching center location found to be 1/3
Efficiency increases with increasing Reynolds
number
Pitching amplitude and reduced frequency –
extremely important parameters
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Strive for θ0 ≈ 75° and f*=0.15 for highest efficiency
Optimal vertical motion of wing section is a square
wave
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Exceptional
complexity of the
CFD modeling in this
situation
Beyond our scope of
knowledge
Use studies presented
to create an
adjustable
experimental
apparatus
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1)
2)
3)
For fully flow driven motion, three models
were considered based off of relevant studies
System whose pitching movement was
allowed through a rotational spring
System whose pitching movement was
allowed to achieve a max value during ‘power
stroke’ and used a mechanical lever arm to
change angles of attack, and thus, direction
System which utilized a mechanically
prescribed motion
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While all three models have been confirmed to
operate effectively with numerical simulations,
the use of a mechanical lever arm was chosen
on the basis of simplicity of design and higher
efficiency
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Linear bearings needed
to reduce friction and
mechanical inefficiency
Two wings attached to
same track
To apply as much force
to the generator as
possible, new system’s
wing sections will stand
vertically – weight will
not counteract lift
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Use of one track cuts
costs
Use of two wing
sections increases
power, eliminates
unwanted moments
Lever arm responsible
for pitch angle reversal
by coming into contact
with a stopper
Mechanism by which
ideal pitch reversal time
will be approximated
Design, Build, Test Small Scale Model
Kinsey and Dumas 2008
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θ≈73°, f*≈0.15, H/c≈1
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Platzer et al. 2010
Lever Arm
ΔTR = 0.3
28
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Design
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Adjustability
Power Transmission
Wing Design
Testing
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PIV
Velocity Profile
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The pitching amplitude
will adjust by a series
of holes on the bearing
block
Each pair of holes will
allow for a different
maximum pitch
Pivot
Bearing
Holes
Airfoil/
Lever Arm
Block
Pegs
30
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Heaving amplitude - Adjusted by moving a pair of
locking collars on track
Fixed Supports
Pivot
Bearing Block
Locking
Collar
Locking
Collar
Track
Mechanical
Stops
Airfoil/
Lever Arm
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Objective: Linear Movement
Electrical Energy
Power
Transmission
Linear
Generator
Pneumatic
Piezoelectric
DIY/Patents
Extremely
Inefficient
Need Small
Displacement
Mechanical
(Gear/Pulley)
Many
Options/High
Efficiency
32
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Method
Linear
Movement
One-Way
Rotation
Flywheel Energy
Storage
Rotary Generator
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Found that
magnetic flux is
directly related to
rotor speed and
efficiency
Most PM
Generators
designed for use at
a given rotor speed
Use of a flywheel
for constant speed
“Dynamic modeling of transverse flux
permanent magnet generator for wind
turbines “ - Maurício B. C. SallesI; José R.
CardosoI; Kay HameyerII
34
T
Energy extracted flywheel =
energy gained by airfoil +
frictional losses each cycle
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θ0
𝐻
𝑇𝑑θ= 0 𝐿𝑑𝑦
0
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θ0
T= Torque of generator
θ0=angle passed through in
one cycle
L=lift force
H=total linear distance
traveled in one cycle
0.5*H
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Very low mass
Strong enough to
withstand forces of lift
and momentum change
Durability – must
withstand outdoor
weather conditions
Ease of manufacturing
and assembly
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Inflatable Wing
Styrofoam
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Composite Wing
Sails
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Inflatable wing very light and cheap, but
leaking may pose problems
Composite wing is very strong and
lightweight, but it is difficult to manufacture
and repair
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ANSYS calculation for Styrofoam wing
Stress levels too high at peak power output levels
Styrofoam ruled out
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Sail is an attractive choice
Cheapest option
 Most Durable
 Ease of manufacture,
assembly and maintenance
 Reversible camber
 Lose some efficiency –
lower CL
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Partially rigid ‘wingsail’
– best option
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Movement will be
translated to
generator by timing
pulley-belt system
First order vibration
analysis of the
system reveals its
equation of motion,
natural frequency
and damping ratio
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PIV testing to be conducted on completed prototype
Integration of the velocity fields around the airfoil can supply
the vibrational model’s forcing function
Algorithm inputs forcing function is used to optimize system
Kutta-Joukowski theorem
(ρ = free stream density,
V = free stream velocity,
and Γ = circulation)
Definition of Cirulation
(C is the curve enclosing
the airfoil and Vcosθ is
the velocity tangent to the
curve)
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Optimize parameters in
nonlinear system
Need for algorithm that can
input complex forcing function
First order approximation
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Simple sinusoidal forcing function
Amplitude determined from thin
airfoil theory calculations
MATLAB - Runge Kutta
Approximation for vibrational
analysis
Used vibration hand calculations
to supply governing equation