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)