2008 COMSOL Conference BostonOutline Introduction: The Advanced Lab Concept “Education is not the...
Transcript of 2008 COMSOL Conference BostonOutline Introduction: The Advanced Lab Concept “Education is not the...
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Resonating with Students in the Undergraduate Physics Laboratory:
Comprehending Acoustic VibrationsKeith SteinBethel UniversitySt. Paul, Minnesota
Dr. Richard Peterson, Jack Houlton, Justin Knapp,Brandon Peplinski, Chris Scheevel, David Swenson
Presented at the COMSOL Conference 2008 Boston
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Introduction: The Advanced Lab Concept Approach
• Optical Diagnostics: Stroboscopic Holography• Computational Modeling: COMSOL Eigenfrequency
Analysis
Examples• Vibrational Modes of a Handbell• Vibrational Modes of a Coffee Cup• Vibrational Modes of a Tuning Fork
Concluding Remarks
Outline
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Introduction:The Advanced Lab Concept
“Education is not the filling of a pail, but the lighting of a fire.” −W.B. Yeats
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Optical Diagnostics Approach:Real-time Stroboscopic Holography
Creation of Reference Hologram
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Optical Diagnostics Approach:Real-time Stroboscopic Holography
Viewing of Reference Hologram
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Optical Diagnostics Approach:Real-time Stroboscopic Holography
Stroboscopic Viewing
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Eigenvalue Analyses• Linear Elasticity• Undamped vibrations• Three objects
• Handbell• Coffee Cup• Tuning Fork
Computational Approach:COMSOL Eigenfrequency Analysis
( ) 0XIA
=λ−
0xKxM
=+
Ftu2
2
=σ⋅∇−∂∂
ρ
22f4π=λ
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Results:Vibrational Modes of a Handbell
Degenerate vibrational mode (3,1) of a handbell
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Results:Vibrational Modes of a Coffee Cup
Non-degenerate vibrationalmode (3,0) of a coffee cup
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Results:Vibrational Modes of a Tuning Fork
Vibrational modes of a tuning fork:FFT sound spectrum
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Results:Vibrational Modes of a Tuning Fork
Vibrational modes of a tuning fork
1st in-plane symmetric mode
COMSOL (278 Hz)
Stroboscopic Holography (273 Hz)
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Results:Vibrational Modes of a Tuning Fork
Vibrational modes of a tuning fork
3rd in-plane symmetric mode
COMSOL (4560 Hz)
Stroboscopic Holography (4647 Hz)
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Results:Vibrational Modes of a Tuning Fork
Vibrational modes of a tuning fork
Out-of-phase torsional mode (3240 Hz)
In-phase torsional mode (3462 Hz)
1st torsionalmodes
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Results:Vibrational Modes of a Tuning Fork
Vibrational modes of a tuning fork
COMSOL (582 Hz)
Stroboscopic Holography (530 Hz)
1st out-of plane bending mode
?
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Concluding Remarks
COMSOL and optical diagnostics can serve as complementary tools in the undergraduate advanced laboratory.
Together, COMSOL and optical diagnostics can provide students of applied physics, optics, and engineering with a fuller and richer understanding of acoustic vibrations.
COMSOL can serve to illuminate aspects of acoustic vibrations that might be overlooked by purely experimental approaches (and vice versa).