impact data analysis and sensor modification for pressure data of granular gases in reduced gravity...
TRANSCRIPT
![Page 1: Impact Data Analysis and Sensor Modification for Pressure Data of Granular Gases in Reduced Gravity Aaron Coyner, Justin Mitchell, and Matthew Olson University](https://reader035.vdocument.in/reader035/viewer/2022062516/56649e375503460f94b27659/html5/thumbnails/1.jpg)
Impact Data Analysis and Sensor Modification for Pressure Data of
Granular Gases in Reduced Gravity
Aaron Coyner, Justin Mitchell, and Matthew Olson
University of Tulsa
April 9, 2003
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Granular Gases Excited granular media can
simulate molecules similar to those in ideal gases
Excitation results in kinetic motion
• Velocities have distribution of amplitudes
• Random directions
Modified gas laws can be applied
• Granular Temperature
• Theory shows v2
proportionality*
• Granular Pressure• One experiment shows
v3/2 proportionality** Theory predicts ordering
(inelastic collapse)
** É. Falcon et al. , Phys. Rev. Lett. 80. 440 (1999).
* A. Puglisi, A. Baldassarri, and V. Loreto, Phys. Rev E 66 061305.
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Importance of Impact Data
Impact data can aid in development of speed distributions.• Can apply results to large systems of particles without
individual tracking
Each experiment set should have a distinct set of collision frequencies• Frequency response should depend on number of particles
and driving parameters.
Data should also reflect the predicted collapse if it occurs
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Relevance to Reduced Gravity
Inelastic Collapse of granular systems in reduced gravity could explain:• Asteroid Formation
• Planetary Rings
• Other celestial systems that could not for by gravitation alone.
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Ways to Achieve Reduced Gravity
Sounding Rocket• Falcon et al. (1999)
Nasa’s KC-135 “Weightless Wonder”
Space Shuttle Flight• Get Away Special
KC-135
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The Gr.A.I.N.S. Experiment
Box set of 8 sample cells
• Each cell ~1 in3
• Each cell contain varied number of brass ball
• Sapphire walls
• Each cell has an impact sensor
• Impact data stored in external data drive
Mechanical Shaker System
• Varies amplitude and frequency
Cameras and Mirrors
• Cameras record video of 3 faces of the cube.
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Impact Sensors (Initial Run)
0.75” diameter APC 850 ceramic
piezoelectric material• lead zirconate titanate
formulation 2 MHz Bandwidth Wired into Camera Audio
Channels
• Subminiature coax used
Piezoelectric Disk
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Steps in Data Analysis
Determine camera effects• Amplification of signal
• Signal coupling (unexpected)
• 300 mV signal on right channel appears on left channel with equal amplitude at > 600 Hz
Initial run of time series and power spectra• FFT analysis
• Low frequency and high frequency responses
Audio parsing to obtain low frequency peaks evident in time series
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Camera Effects Camera Amplification
• Test signal 300 mV sine wave
• Frequency 10-1050 Hz
Plot Amplification (Vcam/Vin) vs frequency
Frequency Dead Spots at 150 Hz multiples
Amplification vs.Frequency
-0.2
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
-150 50 250 450 650 850 1050
Hz
Vca
m/V
app
Mag
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Time Series Analysis Low Frequency
~68 ms ~15 Hz
Time Series Excerpt from Reduced Gravity Parabola. Driving Frequency approximately 13 Hz. The variation in frequency involves higher harmonics
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Time Series (high frequency)
~2ms
High frequency analysis of time series shows systematic peaks every 2ms.FFT should have peak ~500 Hz.
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Initial FFT Analysis
474.7 Hz
952 Hz
Series of harmonic peaks in high frequency (474.7 Hz fundamental)Insufficient resolution (~1.5 Hz) to distinguish low frequency response
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Audio Parsing Data Files split into 8 files
each containing every 8th point
Sample rate decreases to 6 kHz (resolution improved to ~0.25 Hz)
Parabola 19 driving frequency 17.5 Hz from motor data
Peaks in FFT show harmonics of 20 Hz
A few questions remain about the effectiveness/ problems of parsing.
Parabola 19 Box B Parsing 8
0
0.05
0.1
0.15
0.2
0.25
0.3
-10 10 30 50 70 90 110 130 150
frequency
Per
cen
t F
ull
Sca
le (
V)
Series1
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Modifications/Improvements for 2003 Flight
Sensors reconstructed and more solidly bonded to central plate of box set.
Sensor voltage amplified using standard inverting op-amp (impacts easier to detect)
Data collection controlled by a microcontroller and stored on a hard drive. (Sampling rate reduced to 2kHz)
Reliance on camera function for impact information avoided.
Coupling of signal eliminated
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Impact Data SampleCH.0 Day 2 Parabola 4
-0.2
0
0.2
0.4
0.6
0.8
1
1.2
0 800 1600 2400 3200 4000
Sample
Vo
ltag
e
Ch.0
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Acknowledgements
Dr. Michael Wilson -- National Academy of Sciences
Mr. Shawn Jackson -- University of Tulsa
Rebecca Ragar, Jeffrey Wagner, Justin Eskridge, Adrienne McVey, Erin Lewallen, and Ian Zedalis.
Dr. Roger Blais -- University of Tulsa