1. –
Aeroelastic Composite Wing Design
Marshall LeVett, Nathan DeVille, Michael Ogrin, Michael Riashi
Adv: Prof. McNamara
INTRODUCTION
Performance automobiles use electromechanically
controlled rear wings to create downforce. This helps
improves traction and stability around curves.
Hypothesis
Developing a wing that passively deforms by exploiting
bend-twist coupling through composites can achieve
the same effect as traditional electromechanical “active
aerodynamics.”
Objective
Design and fabricate a wing with maximized bend-twist
coupling and associated measurement equipment for
examination of aerodynamic characteristics
Success Criteria
Will be compared to a similar conventional rigid spoiler.
Must have equivalent downforce at higher speeds while
reducing the amount of drag at low speeds
Methods
Fabrication
A flat piece of glass was used as a mold. 4/5 layers of
30° and 4/5 layers of 0° were laid on the glass with a
slow cure epoxy. The plate was placed in a vacuum bag
and left to cure over night. The final shape was cut out
of the cured layup.
WindTunnel
The 22” x 22” wind tunnel was used for testing. The
wing was mounted at an initial angle of attack of 2°.
The wing was tested under a freestream velocity of 10
m/s to 30 m/s. Once the test was run, the angle of
attack was increased by 2° up to 10°.
TestRig
The lift and drag were measured using a Futek bi-axial
load cell. The wing was mounted vertically in the wind
tunnel. This ensured that gravitational loads would not
effect the bend-twist .
Deformation
The deformation was measured using two grids, one on
the top and one on the bottom. Using an averaging
method and similar triangles, the deformation was
calculated. Due to the low-fidelity nature of the system,
this method is not very accurate.
ACKNOWLEDGEMENTS
Facilities and funding provided by The Ohio State University.
Goal
Using classical laminate theory, bend-twist coupling can
be optimized. This will allow the layup angles to be
calculated as a [0,θ] orientation. This layup is
experimentally tested to gather the lift, drag, and the
deformation. Various layups of the same orientation will
be created. The layups will vary in thickness and
materials. This will allow the different layups to be
compared to one another.
Optimization
Layup curing in vacuum bag
For a layup of [0,θ], 30° was found to be the optimal
angle to maximize bend-twist coupling.
RESULTS
Lift and Drag
Lift and drag coefficients were taken for each wing at each
angle of attack. The overall trends were somewhat
random, but there is usually a clear growth until a certain
velocity.
At this critical velocity, the wings would vibrate extremely
fast at about 300 Hz. These velocities and frequencies are
named the critical flutter velocities and frequencies.
However, typical flutter frequencies for cantilever wings of
similar geometries range from 5 to 10 Hz.
10 15 20 25 30 35
0
0.5
1
1.5
2
2.5
3
3.5
4
Velocity [m/s]
ForceCoefficient
Carbon Fiber [04
/304
] at 10 degrees AoA
CL
CD
Flutter Visualization
0
50
100
150
200
250
300
350
400
450
500
12
14
16
18
20
22
24
26
28
30
32
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Frequency (Hz)
FFT of CF [04
/304
] Lift Data
Velocity (m/s)
12.6 m/s
15.8 m/s
20.3 m/s
23.1 m/s
26.1 m/s
30.1 m/s
CONCLUSIONS
The hypothesis and objective were completed. The wing
exhibited excellent bend-twist coupling. However, the
success of the experiment was not able to be
determined from our data.
Top-down view of fiberglass wing
The onset of vibrations introduce chaotic, unsteady
aerodynamics. These aerodynamics can not be
resolved with a quasi-steady simulation.
An analytical model to account for this sudden drop off
in lift and drag, such as Theodorsen’s theory, explains
that a flapping wing will have less lift and drag at a
snapshot in time than a static wing at the same
conditions.
Sources of Error