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Flow field measurements in geometrically-realistic larynx models

Flow field measurements in geometrically-realistic larynx models. Jayrin Farley Research Assistant, Brigham Young University, Dept. of Mechanical Engineering Scott L. Thomson Associate Professor, Brigham Young University, Dept. of Mechanical Engineering

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Flow field measurements in geometrically-realistic larynx models

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  1. Flow field measurements in geometrically-realistic larynx models JayrinFarley Research Assistant, Brigham Young University, Dept. of Mechanical Engineering Scott L. Thomson Associate Professor, Brigham Young University, Dept. of Mechanical Engineering Visiting Professor, University of Erlangen, Graduate School in Advanced Optical Technologies 9th Pan European Voice Conference Marseille, France 31 August – 3 September 2011

  2. 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)

  3. 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/supraglottalflow using actual, complex geometries

  4. Present work • Method for measuring flow velocity in models using realistic geometry • Working fluid: liquid • Current implementation: static model • Driven model conceivable

  5. 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

  6. Model fabrication • 3D CAD model • Water-soluble rapid prototype • Seal prototype surface • Mount prototype in cube-shaped mold • Pour clear silicone around model • Let silicone cure • Dissolve model using running water Final product: Clear cube with airway-shaped cavity For details: Farley and Thomson, 2011, JASA 130:EL82-EL86

  7. Working fluid selection • Cavity has curved surfaces • For optical access, need fluid to match silicone index of refraction • Use glycerine/water mixture

  8. Working fluid selection • Place a grid behind the model • Start glycerol/water flowing through model • Dilute until grid distortion minimized Grid behind cube Silicone cube with air-filled cavity

  9. Working fluid selection • Place a grid behind the model • Start glycerol/water flowing through model • Dilute until grid distortion minimized Water 55% glycerin, 45% water Air

  10. Test setup

  11. PIV settings • Hollow glass spheres • 500 image pairs • 5 sagittal and 5 frontal planes • Interrogation: 16 × 16 window, 50% overlap

  12. PIV settings • Hollow glass spheres • 500 image pairs • 5 sagittal and 5 frontal planes • Interrogation: 16 × 16 window, 50% overlap

  13. Velocity results

  14. Velocity results

  15. Velocity results

  16. Counter-rotating vortices Clockwise vortex Counter-clockwise vortex

  17. Velocity results

  18. Velocity results

  19. Remarks 1. Reynolds # similarity maintained (not Mach #) 2. Static model Driven conceivable Self-oscillating not possible 3. Results show 3D PIV is desirable 4. Simultaneous pressure measurements possible

  20. 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

  21. Acknowledgements • U.S. National Institutes of Health • R01 DC009616 (Thomson, PI)

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