American Physics Society Division of Fluid Dynamics Meeting Presentation. Fluid dynamics study of vortex ring propagating tangentially over a flexible beam.
1. Fluid-Structure Interactions as Flow Propagates
Tangentially Over a Flexible Plate with Application
to Voiced Speech Production
Andrea R. Westervelt
Byron D. Erath
Department of Mechanical and Aeronautical Engineering
Clarkson University, Potsdam, NY
American Physical Society
Division of Fluid Dynamics 66th Annual Meeting
November 24–26, 2013
Pittsburgh, Pennsylvania
2. Objective
1
• Fluid-structure interactions
– Between a vortex ring and cantilevered flexible beam in axial flow
– Relates to impact of vortices on vocal folds
• Future applications
– Apply more directly to speech
– Energy harvesting in a flexible beam
66th Annual APS DFD Meeting, November 26, 2013
3. Introduction
2
• Formation
– Areas of concentrated rotational motion
– Intraglottal flow separation
– Shear layer
• Effects in speech
– Cause pressure drop along vocal folds
– Assists in rapid closure
– Sources of sound
• Effects in energy harvesting
– Impact plate to create a voltage
Vorticity plot of regular vocal fold motion (Erath
and Plesniak, 2010)
66th Annual APS DFD Meeting, November 26, 2013
4. Research Questions
3
• How are the dynamics of a flexible beam affected as a vortex
ring propagates tangentially over it?
• What effect will intraglottal vortices have on the dynamics of
human vocal folds during phonation?
– Is this worth investigating?
66th Annual APS DFD Meeting, November 26, 2013
5. Experimental Setup
4
• Rectangular tank filled with deionized water
– Tank dimensions: 4’ x 1’ x 2’
• Vortex generation
– Pressure-driven flow generated by timed solenoid release
– L/d (slug length to pipe diameter) ratio regulated by LabVIEW
• Beam properties
– 4” x 4” x 0.005”
– Offset ½” from vortex output, 3-1/2” downstream
Diagram of experimental setup
66th Annual APS DFD Meeting, November 26, 2013
12. Discussion and Conclusions
11
• Voiced speech
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Movement
Match stiffness
Unknown mass ratio, external tension
Circulation strength?
Advection velocity?
• Energy Harvesting
– Small displacements
– Angle of impact
– Expand parameter regime
66th Annual APS DFD Meeting, November 26, 2013
13. Future Works
12
• Scaling to speech
– Beam/vocal fold dimensions
– Nondimensional parameters
– Physiological parameters
• PIV system
– Vortex circulation
– Quiescence
• Energy harvesting
– Piezoelectric plate
66th Annual APS DFD Meeting, November 26, 2013
14. 13
Acknowledgements
This research was supported by A Scholarship Program to
Increase Retention in Engineering (ASPIRE) through Clarkson
University’s Community of Underrepresented Professional
Opportunities (CUPO).
66th Annual APS DFD Meeting, November 26, 2013
15. References
14
• Erath, B. D., & Plesniak, M. W. (2010). Viscous flow features in
scaled-up physical models of normal and pathological vocal
phonation. International Journal of Heat and Fluid Flow, 31(3),
468-481. doi:10.1016/j.ijheatfluidflow.2010.02.014
66th Annual APS DFD Meeting, November 26, 2013
Editor's Notes
The objective of this study is to determine the impact of the fluid-structure interactions between a vortex ring and a flexible beam in axial flow. This is relevant to the fluid-structure interactions between the human vocal folds and the shear vortices generated during phonation.Future applications of this research can apply more directly to speech, as well as measure energy harvesting in a piezoelectric flexible beam.
Vortices are areas of concentrated rotational motionIn speech, vortices cam form by means of intraglottal flow separation.In addition, shear layer vortices can be observed.Intraglottal vortices occur in the glottis, or the area in between the vocal folds.These vortices cause a pressure drop along the vocal folds, which aids in their rapid closure. Once closed, the pressure builds up again to result in the vocal folds reopening, only to have the cycle continue again. This results in self-sustained oscillations of the vocal folds.Rapid closure of the vocal folds has been related to quality of speech. Fast/good rapid closure = better speechVortices can be sources of soundAs vortices impact a piezoelectric plate, they incite plate motion to create a voltage which can produce energy
The questions I would like to investigate are:How are the dynamics of a flexible beam affected as a vortex ring propagates tangentially over it?Using the results from this question, we can try to use our model to discover What effect will intraglottal vortices have on the dynamics of human vocal folds during phonation?
I conducted experimental research to investigate the questionsBuilt a rectangular tank filled with deionized water, dimensions 4 feet by 1 ft by 2 ftI generated a vortex ring by using pressure-driven flow. The flow was expelled into the tank using a timed solenoid release based on the desired vorticity of the vortex ring.In speech, circulation of vortices relates to an L/d ratio of 4. Therefore, we time the solenoid valve to open for adequate time to create this ratio to model vortices formed during phonation.Beam properties: originally 10x scaled up model of human speech (1.25 inches by 4 inches), but this plate did not see any displacements when passed by vortex ring.Therefore, increased beam length to 4 inches by 4 inches.Beam was offset ½ inch from pipe exit into tank, and beginning of beam 3 ½ inches downstream
Using the Euler-Bernoulli beam equation, tried to match nondimensional parameters of our experiment to those of speech.However, not completely successful due to circumstancesMass ratio:Could not match to speech, because when considering the ratio of the fluid densities as well as our scale factor, our mass of the plate would have to be 10,000 times that of the vocal folds which we could not obtain in our setup.Stiffness: Originally were able to match almost exactly to that of speech, upon changing the length, no longer as close as originally was. However, still of same order.Fluid tension:Neglected because it was of a much smaller order than the other forcesExternal tension:Neglected because our beam is cantilevered and therefore there is no tension on the free endReynolds number & Strouhal number then allowed us to match the frequency of the beam to the frequency of the vocal folds in speech
To capture our data, we used a high-speed camera with a capture rate of 100 frames per secondCreated contrast to analyze beam and vortices by using a laser to create a 2-D sheet of beam location and that combined with fluorescein dye allowed us to see the vortex structureMotion tracking software to analyze the displacements of the beam as it was impacted by vortex ring
Here you can see the beam moving as the vortex passes over it. Can see vortex breaking up as it passes over the plate whereas it no longer has a uniform circulation
Snapshots of vortex ring passing over the plate, once again see the same things as video
Analyzed displacement of end of beam (blue) and middle of beam (green) as vortex passed over it.As expected, the end of the beam has a greater displacement than the middle. However, unexpectedly, the beam does not see displacement at the center earlier than displacement at the free end. We thought that as the vortex passes over the exact location, that’s exactly when we would see the displacements
So some conclusions we saw from our experiment was that the experimental setup was not able to model speech as we had planned. Mass ratio was impossible to scale to voiced speech, and we were unable to guarantee that the vorticity matched that of the vortices in speech. However, although it may not match speech, it may still be relevant to energy harvesting.The beam did not oscillate as expected based on our previous experiment. In the previous setup, used a plunger to generate vortices instead of solenoid released. This had a much higher flow velocity than our current setup, which may be why the displacements are so different. In the previous setup, you can see the wavelike motion of the beam as impacted by the vortex ring, and the vortex ring also does not break up until the end of the plate. Can also see Coanda effect as exhibited in speech.
In the future, we’d like to try and adjust the beam dimensions and nondimensional parameters to improve our results and once again see if changing various parameters will allow our setup to model voiced speech production.In addition, using a PIV system will improve the ability to have quiescence of fluid (right now using dye, the longer you wait, the poorer your vortices can be visualized). Also, we will be able to measure the vortex circulation to match the ciriculation strength in speech.We plan to try using a piezoelectric plate to measure energy harvested in beam as it is impacted by the vortices
