Advisors: Dr. Manish Paliwal and Dr. Lisa Grega Kevin Hynes
David Talarico
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At the current time, we have used somewhere around half of the
earths 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
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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 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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Pitching- rotational movement of wing Plunging- translational
movement of wing Coupling these two motions will allow the design
of a system that can extract flow energy through lift and vortex
formation Kinsey and Dumas 2008
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Plunge Amplitude (H o ) Pitch Amplitude ( o ) Effective angle
of attack ( ) 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
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Energy Harvesting through Flow-Induced Oscillations of a Foil 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 Y- component
of force and velocity are both at their maximum - Power Strokes
ended by rapid pitching of airfoil and change in vertical
direction
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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
Strive for 0 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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For fully flow driven motion, three models were considered
based off of relevant studies 1) System whose pitching movement was
allowed through a rotational spring 2) 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 3) 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 systems 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
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Kinsey and Dumas 2008 73, f* 0.15, H/c1 Platzer et al. 2010
Lever Arm T R = 0.3 Design, Build, Test Small Scale Model 28
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 Bearing Block HolesPegs Airfoil/ Lever Arm Pivot 30
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Heaving amplitude - Adjusted by moving a pair of locking
collars on track Bearing Block Track Locking Collar Airfoil/ Lever
Arm Pivo t Fixed Supports Mechanical Stops 31
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Objective: Linear Movement Electrical Energy Power Transmission
Linear Generator DIY/Patents Pneumatic Extremely Inefficient
Piezoelectric Need Small Displacement Mechanical ( Gear/Pulley )
Many Options/High Efficiency 32
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Method Linear Movement One-Way Rotation Rotary Generator
Flywheel Energy Storage 33
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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 -
Maurcio B. C. Salles I ; Jos R. Cardoso I ; Kay Hameyer II 34
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T 00 0.5*H 35
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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 Composite Wing Sails Styrofoam
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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 C L 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 models forcing function Algorithm inputs forcing
function is used to optimize system Kutta-Joukowski theorem ( =
free stream density, V = free stream velocity, and = circulation)
Definition of Cirulation (C is the curve enclosing the airfoil and
Vcos 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 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