Flow field measurements in geometrically-realistic larynx models
Jayrin FarleyResearch Assistant, Brigham Young University, Dept. of Mechanical Engineering
Scott L. ThomsonAssociate Professor, Brigham Young University, Dept. of Mechanical EngineeringVisiting Professor, University of Erlangen, Graduate School in Advanced Optical Technologies
9th Pan European Voice ConferenceMarseille, France31 August – 3 September 2011
Background
• Laryngeal airflow:• Provides energy for vocal fold vibration• Influences speech sound quality• Strongly dependent on larynx geometry
• Most popular methods of measuring velocity:• Hot-wire anemometry• Particle image velocimetry (PIV)
PIV and hot-wire experiments
• Static models• Simplified geometry
• Synthetic driven & self-oscillating models• Simplified geometry
• Excised larynges• Supraglottis only, geometric and other limitations
• Problem with realistic geometry: curved surfaces• No studies of sub/intra/supraglottal flow using
actual, complex geometries
Present work
• Method for measuring flow velocity in models using realistic geometry
• Working fluid: liquid
• Current implementation: static model• Driven model conceivable
Basis for present work
• Nasal cavity airflow studies1
• Create hollow model of desired geometry
• Match index of refraction between fluid & model
• Use PIV to measure velocity within model
1Hopkins et al., 2000, Experiments in Fluids 29:91-95
Model fabrication
1. 3D CAD model2. Water-soluble rapid prototype 3. Seal prototype surface4. Mount prototype in cube-shaped mold5. Pour clear silicone around model6. Let silicone cure7. Dissolve model using running water
Final product: Clear cube with airway-shaped cavity
For details: Farley and Thomson, 2011, JASA 130:EL82-EL86
Working fluid selection
• Cavity has curved surfaces • For optical access, need fluid to match silicone
index of refraction• Use glycerine/water mixture
Working fluid selection
Silicone cube with air-filled cavity
Grid behind cube
• Place a grid behind the model• Start glycerol/water flowing through model• Dilute until grid distortion minimized
Working fluid selection
Air Water 55% glycerin, 45% water
• Place a grid behind the model• Start glycerol/water flowing through model• Dilute until grid distortion minimized
Test setup
PIV settings
• Hollow glass spheres• 500 image pairs• 5 sagittal and 5 frontal planes• Interrogation: 16 × 16 window, 50% overlap
PIV settings
• Hollow glass spheres• 500 image pairs• 5 sagittal and 5 frontal planes• Interrogation: 16 × 16 window, 50% overlap
Velocity results
1.6
m/s
0
Velocity results
1.6
m/s
0
Velocity results
1.6
m/s
0
Counter-rotating vortices
Counter-clockwise
vortex
Clockwise vortex
Velocity results
1.6
m/s
0
Velocity results
1.6
m/s
0
Remarks
1. Reynolds # similarity maintained (not Mach #)2. Static model
Driven conceivableSelf-oscillating not possible
3. Results show 3D PIV is desirable4. Simultaneous pressure measurements possible
Summary and Conclusions
• Velocity measured in models with complex geometry
• Can interrogate anywhere in model• Future use to characterize 3D flow field
• Vortical patterns, turbulence levels• Computer model validation
Acknowledgements
• U.S. National Institutes of Health• R01 DC009616 (Thomson, PI)
Top Related