1 | Page Semi-Span Flapping Wing Model ME 435 Project Design and Management II Brayler Gonzalez, Julia Romanchik & Bryce Horvath 4/26/2011
1 | P a g e
Semi-Span Flapping Wing Model
ME 435 Project Design and Management II
Brayler Gonzalez, Julia Romanchik & Bryce Horvath
4/26/2011
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Contents:
List of Figures: .............................................................................................................................................. 3
Abstract: ........................................................................................................................................................ 4
Introduction: .................................................................................................................................................. 5
Wing Design and Wind Tunnel Assembly: .................................................................................................. 6
Inventor Model.......................................................................................................................................... 6
Materials ................................................................................................................................................... 7
Wing Mechanism ...................................................................................................................................... 7
Wing Characteristics ................................................................................................................................. 8
PIV ............................................................................................................................................................ 8
Force Transducer ...................................................................................................................................... 9
List of Materials ...................................................................................................................................... 10
Overall Wing Mechanism Set-Up ........................................................................................................... 11
Wind Tunnel ........................................................................................................................................... 12
Cost Consideration Summary: .................................................................................................................... 12
Scheduling: ................................................................................................................................................. 13
Future .......................................................................................................................................................... 13
References: .................................................................................................................................................. 14
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List of Figures:
Figure 1 – Inventor Model of Wing ……………………………………………………………6
Figure 2 – Inventor Model of T-Connecter …………………………………………………….6
Figure 3 – Wing Mechanism …………………………………………………………………...7
Figure 4 – Particle Image Velocimetry ………………………………………………………...8
Figure 5 – Force Transducer …………………………………………………………………....9
Figure 6 – List of Materials ……………………………………………………………………10
Figure 7 – Wing Mechanism Set-up …………………………………………………………...11
Figure 8 – Layout of ODU's low Low-Speed wind tunnel …………………………………….12
Figure 9 – Gantt Chart …………………………………………………………………………13
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Abstract:
The Semi-Span Flapping Wing project’s main objectives include obtaining a force
analysis and determining the flow field around a single flapping wing in order to demonstrate the
aerodynamics surrounding the wing due to both vertical flapping motion and varying angles of
attack. The wing utilizes a design which causes it to aeroelastically bend while flapping due to
spar rotation in conjunction with a turn table, allowing for both the vertical flapping motion,
bending motion, and varying angles of attack, imitating bird flight (Rabiger). This project
employs the use of the low speed wind tunnel, as well as a force transducer and particle image
velocimetry to measure the desired properties. The resulting data will give insight to the multiple
aerodynamic occurrences surrounding the wing model for further use in designing more efficient
and effective flapping wings.
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Introduction:
Flapping Wing Flight refers to flight driven by oscillating airfoils which imitate nature.
This includes flapping wing flight as seen in insects, bats, and birds. Currently, ornithopters are
the most popular form of flapping wing aircraft (Chronister, 1996), but research progression has
expanded the range of flapping wing aircraft to include multiple devices with various uses, and
has evolved from simple toy models to flapping UAVs for use in spy missions. Our research
objective includes obtaining information on flapping wing motion in bird flight, bird anatomy
and skeletal structure, and past and present flapping wing projects. This information, in
conjunction with some assumptions and simplifications due to the complexity of bird flight, will
allow us to determine a plausible and testable wing design. Using this design, we will construct a
simplified kinematic wing structure mechanism using Inventor software. After calculating the
theoretical forces expected to act on the wing during flapping flight, we will determine possible
materials which contain necessary properties to obtain vertical and torsional flapping motion and
build the model for use in testing in the low speed wind tunnel. Through this experiment, we
hope to be able to better apprehend flapping flight for future use in aircraft, since little
information on how or why flapping flight works is currently available. The data collected in this
experiment would allow for a better understanding of the air flow and forces acting on the wing,
which could be used to improve the design to produce a more efficient flapping wing for use in
aircraft.
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Wing Design and Wind Tunnel Assembly:
Inventor Model
Figure 1 Inventor Model of Wing
Figure 2 Inventor Model of T-Connecters
Note: The first four
T-connecters are
exactly
perpendicular. The
following four T-
connecters are
angled, with the
angle increasing per
connecter towards
the tip of the wing.
H1 (Rigid Spar)
H2
(Bending
Spar)
Ribs Ripstop Nylon
Ribs
H1
(Rigid
Spar)
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Materials
The spars H1 and H2 and the ribs will be carbon fiber rods, with the rigid spar H1
constructed from a larger diameter rod to promote rigidity, and the bending spar H2 made up of a
smaller diameter rod to promote flexion. The ribs will attach to the rigid member by means of the
T-Connectors as seen on Figure 2. The surface membrane of the wing will be Ripstop Nylon,
allowing the wing to bend naturally. The Ripstop Nylon membrane will be attached to the rods
using sewn in pockets around the ribs and spars, in combination with glue, if necessary. A DC
current motor with a specially made encoder will be used to create the flapping motion.
Figure 3 Wing Mechanism
Wing Mechanism
The figure above shows that the motor will generate the flapping motion by rotating the two
connected links and shaft, which is connected to spar H1by a connector pin. When the wing
completes a cycle, going from a downstroke to an upstroke and back down to a downstroke, the
resulting motion produces one wing beat. Each wing beat cycle, measured in Hertz, can be
manipulated and controlled by using an encoder. Our highest upstroke angle is 23 degrees and
our lowest downstroke angle is 23 degrees (Bullen, & McKenzie, 2002), based on our research
of bird flight. Spar H2 rotates the wing passively as the mechanism moves the rigid spar,
producing torsion without requiring any direct input from the motor. In other words, H1 acts as a
rigid bar or a bending resistant spar that transmits the power, while H2 is free to elastically twist
due to torsion, making it twist naturally with maximum torsion occurring at the tip of the wing
(Rabiger). The encoder will give Labview the motor's position with respect to time. It should be
noted that the entire moving mechanism sits on top of the force transducer to precisely measure
all forces.
Connector Pin
DC Motor
Shaft
Links
H1
Force
Transducer
Page 8
Wing Characteristics
Table 1 Wing characteristics
Wing Semi-Span 1.5 ft
Wing Area of Semi-Span .807 ft2
Aspect Ratio of the Span 5.577
Wingbeat Frequency 5 Hz
With a uniform flow of 10 m/s and an angle of attack of 5 degrees applied to the Semi-Span
Wing, and using the NACA 0012 2-D Lift Coefficient (Abbott, &Von Doenhoff, 1959) the
results turnout to be:
Table 2 Lift and Drag Parameters
Lift .4166 lbs
Drag .0153 lbs
L/D 27.28
PIV
A particle image velocimetry system will be used to
measure the velocity of the flow stream around the
wing. The particle image velocimetry system consists
of a high quality digital camera, a laser, and a fiber
optics cable that synchronizes the instruments together
by an external trigger that fires the laser and the camera.
It contains an optical arrangement to covert the laser
output light into a thin light sheet, which measures the
instantaneous velocity at a 2 dimensional slice of the flow field. After multiple fires from both
the laser and camera, we will have a sufficient number of instantaneous flow fields to compile
them into a video clip. This clip will show how the flow moves around the wing, turbulent spots,
separation of flow, and vortices generated by the wing.
Figure 4 Particle Image Velocimetry
Layout (Kerenyi, 2007)
(Hennington, Spedding, & Hedenstrom, 2008)
These numbers were calculated assuming the Elliptic-Spanwise
Circulation Distribution for the Lifting Line Theory (Bertin, &
Cummings, 2009)
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Force Transducer
A force transducer will be used to measure the forces acting on the wing. A table of the
measureable forces is illustrated below. The device converts force, weight and pressure into
output signals. These signals are then sent to a data acquisition system
on a computer. The measurements from the force transducer, the PIV
system, and the position of the DC motor will be combined in Labview
to give a full analysis of the forces acting on wing at different points in
time.
Table 3 Max Load and Accuracy of the Force Transducer
Fx,Fy Fz Tx,Ty Tz
Max
Load
±280 lbf ±930 lbf ±700 lbf-in ±730 lbf-in
Accuracy 1/160 lbf 1/80 lbf 1/80 lbf-in 1/80 lbf-in
Figure 5 Force
Transducer
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List of Materials
Cost Amount in a Pack
Needed Amount
Total
Mechanism
Keyed Shaft $20.00 1 1 $20.00
Key Stock (3/32" x 12") $1.50 1 1 $1.50
Sleeve Bearing (for Shaft) $0.53 1 2 $1.06
Shaft Collars (ID - 3/8") $2.17 1 5 $10.85
Shaft Collars (ID - .25" $2.03 1 3 $6.09
Dowel Pins (D - .25") $9.85 50 1 $9.85
Sleeve Bearing (Thrust Washer)(.25") $1.84 1 4 $7.36
Sleeve Bearing (Thrust Washer)(3/8") $2.24 1 2 $4.48
Socket cap Screws (M4x16mm) $7.69 25 1 $7.69
Socket cap Screws (M6x25mm) $6.62 25 1 $6.62
Washers (for a M6 Screw - OD 9.9mm) $8.65 50 1 $8.65
Socket cap Screws (M6x16mm) $8.00 100 1 $8
Motor 27:1 Planetary $49.99 1 1 $49.99
H1 (Rigid Member) 32.5L - .252OD - .154ID $6.18 1 1 $6.18
H2 (Twisting Member) 29.5L - .179OD - .102ID $4.36 1 1 $4.36
Ribs 48L - CR.098in - W 7.53g $4.49 1 2 $8.98
Ripstop Nylon $11.95 1 1 $11.95
Reed Switch $0.61 1 3 $1.83
Figure 6: List of Materials
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11
Overall Wing Mechanism Set-Up
Figure 7 Wing Mechanism Set-up
This assembly consists of a bottom plate with a force transducer on top of spacer plate, followed
by another rectangular plate that has the two side plates, where the DC gear motor is mounted.
The DC motor powers two links; an upper and a lower link. The upper link is connected to a
shaft which has a connector pin in the middle where the H1 member is attached. This rigid
member (H1) powers the entire wing. The motor has a torque of 694 oz-in and a max rpm value
of 300, which is more than enough to oscillate the wing. The connection between the motor and
the shaft consists of: a wheel connector, a dowel pin, a thrust washer, a link, another thrust
washer, a shaft collar, then another dowel pin that connects the two links, a thrust washer and a
shaft collar on each side. The shaft the link is connected to it by a square key, followed by a
thrust washer and a sleeve bearing, and on the other side, there is a thrust washer and a shaft
collar. The whole assembly will be mounted on a turntable to allow easy and rapid modification
to the angle of attack. This will enable easy comparison of performance at different angles of
attack to help optimize results. The top plate's top surface sits flush to the wind tunnel and will
be bolted down to the turntable.
H1 Side Plates
Upper &
Lower Link
Shaft
Dowel Pin
Shaft
Collar
Thrust
Washer
Wheel
Connector
Motor
Bottom
Plate
Top Plate
Rectangular
Plate
Force
Transducer
Spacer
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12
Wind Tunnel
Figure 8 Layout of ODU's low Low-Speed wind tunnel
This is a schematic of the ODU's subsonic wind tunnel. It is a closed loop wind tunnel with the
necessary turning vanes to redirect the flow, as well as honeycombs and screens to achieve a
uniform flow by the time it reaches our model. Our model is located at the teal ellipse, which is
the high speed test section which measures 3 by 4 feet.
Cost Consideration Summary:
Dr. Landman is providing funding for the project. The only direct costs come from the
cost of carbon fiber rods, Ripstop Nylon fabric, the motor, and the mechanism. All machining
will be done in ODU's machine shop at no cost to us. ODU already owns the force transducer,
turntable, and PIV equipment.
1) Motor: $50
2) Wing: $60
3) Mechanism Components: $95
Total: $205
Old Dominion University
Department of Aerospace Engineering
Low-Speed Wind Tunnel
Dimensions in Inches
High Speed Test Section
(3” X 4’ X 8’ long)
Low Speed Test Section (9’ X 8’)
Fan
Diffuser
Diffuser
Flow
Flow
Turning VanesWing Model Location
Located in KH Room 143
Low Speed Test SectionHigh Speed Test Section
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13
Scheduling:
Gantt Chart
Figure 9 Gantt Chart
The research phase began on October 21st and was completed on November 22nd, with the
selection of the flapping motion that was to be modeled. After this, we selected the wing design
which promotes aeroelastic twisting by spar rotation. Then, we constructed an Inventor model to
get an idea of the flapping angle and to see how everything would fit together. Soon after, we
assembled a prototype wing made out of kite material, wood and fiberglass. During this time we
completed the technical drawings and the part selection for the mechanism. The machine shop
has finished the parts and the parts have come in enabling us to assemble our mechanism.
However, our mechanism cannot be complete without the force transducer which we won't be
able to get a hold of till mid May, along with the wind tunnel. Therefore, we are taking our time
applying the ripstop nylon to our skeletal structure of the wing. The ripstop nylon is cut out and
will be sown around the rigid spar and the ribs in the near future.
Future
Because of the encroaching end to the semester and the lack of wind tunnel time, we will
continue working on the project through the summer. The remaining tasks include: setting up
the tachometer in Labview using input from the reed switch, integrating the force transducer in
LabVIEW, and testing the wing in the wind tunnel.
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14
References:
Abbot t , I r a , & Von Doenhoff , Alber t . (1959) . Theory o f wing sect ions . New
York: Dover .
Ber t in , John, & Cummings , Russel l . (2009) .Aerodynamics for engineers .
Upper Saddle River : Pearson Educat ion .
Bu l l en , R . , & M cKenz ie , N . ( 20 02 ) . Sca l i n g b a t wi n gbea t f r equ en c y an d
am pl i tu de . Th e Jour na l o f E xp er i m en ta l B i o lo g y , 2 3 . R e t r i ev ed f ro m
h t t p : / / j eb .b i o l o g i s t s .o r g / cg i / co n t en t / fu l l / 20 5 / 17 / 26 15
C h ro n i s t e r , N a t h an . (1 99 6 ) . Th e o rn i th o p t er z on e . R e t r i ev ed f r om
h t t p : / / w w w. or n i th op t e r .o r g /
H en n in g t on , P , S p ed d i n g , G , & Hed ens t rom , A . (2 00 8 ) . V o r t ex w ak e an d
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K e r en yi , K o rn e l . (A r t i s t ) . ( 20 07 ) . E xp er i m en ta l s e t u p fo r pa r t i c l e i m ag e
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h t t p : / / w w w. fh w a .do t . go v / en g i n eer in g /h yd r au l i c s / r es ea rch / md do t . c fm
R äb i ge r , Ho r s t . (n .d . ) . Oth er f l a pp in g w in g d es ig ns . R e t r i ev ed f r om
h t t p : / / o rn i th op t e r .de / en gl i s h / win gs .h tm