Michael H Krane - Academia.edu (original) (raw)

Papers by Michael H Krane

Fluid Dynamics Research, 2019

Spatially and temporally resolved Digital Particle Image Velocimetry (DPIV) measurements are pres... more Spatially and temporally resolved Digital Particle Image Velocimetry (DPIV) measurements are presented of flow complexities in a nominally two-dimensional, symmetric, duct with an oscillating constriction. The motivation for this research lies in advancing the state-of-the-art in applying integral control volume analysis to modeling unsteady internal flows. The specific target is acoustic modeling of human phonation. The integral mass and momentum equations are directly coupled to the acoustic equations and provide quantitative insight into acoustic source strengths in addition to the dynamics of the fluid-structure interactions in the glottis. In this study, a square cross-section duct was constructed with symmetric, computer controlled, oscillating constrictions that incorporate both rocking as well as oscillatory open/close motions. Experiments were run in a free-surface water tunnel over a Strouhal number range, based on maximum jet speed and model length, of 0.012-0.048, for a fixed Reynolds number, based on maximum gap opening and maximum jet speed, of 8000. In this study, the constriction motions were continuous with one open-close cycle immediately following another. While the model and its motions were nominally two-dimensional and symmetric, flow asymmetries and oscillation frequency dependent cycle-tocycle variations were observed. These are examined in the context of terms in the integral conservation equations.

Journal of the American Helicopter Society

A 1:4.25-scale model of a generic helicopter rotor hub was tested at Reynolds numbers ranging fro... more A 1:4.25-scale model of a generic helicopter rotor hub was tested at Reynolds numbers ranging from 1.75 × 106 to 7 × 106 at advance ratio of 0.2 in The Pennsylvania State University Applied Research Laboratory Garfield Thomas 48-inch diameter water tunnel. Measurements including drag and wake characteristics were performed up to full-scale Reynolds number with respect to an industry-representative helicopter rotor hub. In particular, the variation of drag and flow field with Reynolds number was characterized. Load measurements were conducted using an improved load cell design, with greater accuracy than in previous experiments. Wake velocity was measured using laser Doppler velocimetry at two downstream planes, yielding velocity statistics to the second order. Improved load measurement accuracy and wake velocity spatial resolution, at full-scale Reynolds number, provide a unique dataset for computational fluid dynamics validation as part of the Penn State Rotor Hub Flow Prediction W...

Experiments in Fluids, 2018

The integral length scale can be calculated from planar particle image velocimetry (PIV) data by ... more The integral length scale can be calculated from planar particle image velocimetry (PIV) data by integrating a two-point velocity correlation over a range of in-plane spatial separations. However, the field of view restricts the integral scale that can be measured by limiting the integration domain. This limitation can be overcome if multiple planes are imaged, and velocity is correlated along the out-of-plane direction. Multiplane particle shadow velocimetry (PSV) is introduced for this purpose. A backlight is used to illuminate particles in the flow field, rather than a laser sheet as in PIV. These illuminated particles obstruct light from entering the camera, thus appearing dark. The combination of two colors in the backlight and a dichroic mirror makes possible the simultaneous imaging of two planes. Separated along the the out-of-plane direction (the optical axis), the multiple imaged planes allow for an integral length scale to be measured independent of the field of view. Experiments were conducted in the axisymmetric 285 mm diameter glycerin tunnel at Penn State's Applied Research Laboratory. Turbulence statistics calculated using multiplane PSV are consistent with those obtained using planar PSV and laser Doppler velocimetry (LDV) at the same facility. The temporal autocorrelation and the integral timescale, measured with planar and multiplane PSV, agree within 95% confidence. The two-point velocity correlation separated spatially along the in-plane radial direction is the same, within 95% confidence, as that separated spatially along the out-of-plane radial direction. The former is insufficient for calculating an integral length scale due to its limited domain. Integrating the latter yields an integral length scale equal to 11% of the radius of the tunnel.

Journal of Biomechanics, 2006

Proceedings of the 10th International Symposium on Cavitation (CAV2018), 2018

Statistics of tip vortex core pressure are estimated from instantaneous Stereo PIV measurements o... more Statistics of tip vortex core pressure are estimated from instantaneous Stereo PIV measurements of the velocity field. The tip vortex was generated by a rectangular planform (aspect ratio 2), elliptically-loaded fin with a NACA66 foil shape. A set of 500 velocity field realizations were acquired at each of three angles of attack. Estimates of pressure for each measured velocity field were computed using a finiteelement scheme that minimized error propagation from the measured velocity field. Histograms of core pressure show that the mean core pressure followed expected scaling with vortex strength, and that the width of the distribution is inversely proportional to vortex strength.

The Journal of the Acoustical Society of America

This paper presents measurements conducted in a physical model of the adult human airway. The goa... more This paper presents measurements conducted in a physical model of the adult human airway. The goals of this work are to (1) benchmark the physical model to excised larynx models in the literature and (2) empirically demonstrate the relationship between vocal fold drag and sound production. Results from the airway model are first benchmarked to published time-averaged behavior of excised larynx models. The airway model in this work exhibited higher glottal volume flow, lower glottal resistance, and less fundamental frequency variation than excised larynx models. Next, concurrent measurements of source behavior and radiated sound were compared. Unsteady transglottal pressure (a surrogate measure for vocal fold drag) and radiated sound, measured at the mouth, showed good correlation. In particular, the standard deviation and the ratio of the power of the first and second harmonics of the transglottal and mouth pressures were strongly correlated. This empirical result supports the assertion that vocal fold drag is the principal source of sound in phonation.

The Journal of the Acoustical Society of America

Scientific Reports

ejecta with a size much larger than the mean particle size of feedstock powder have been observed... more ejecta with a size much larger than the mean particle size of feedstock powder have been observed in powder bed fusion additive manufacturing, both during post-process sieving and embedded within built components. However, their origin has not been adequately explained. Here, we test a hypothesis on the origin of large (much larger than the mass-median-diameter of feedstock powder) ejecta-that, in part, they result from stochastic, inelastic collisions of ejecta and coalescence of partially-sintered agglomerates. the hypothesis is tested using direct observation of ejecta behavior, via high-speed imaging, to identify interactions between ejecta and consequences on melt pool formation. We show that stochastic collisions occur both between particles which are nearly-simultaneously expelled from the laser interaction zone and between particles ejected from distant locations. ejecta are also shown to perturb melt pool geometry, which is argued to be a potential cause of lack-of-fusion flaws. Laser powder bed fusion additive manufacturing (PBFAM), a subcategory of metal 3D printing technology, is rapidly emerging as an important industrial manufacturing technology for aerospace, medical, and defense applications 1,2. The process, which relies on sequential melting of powder layers on the order of tens of microns in thickness, is useful for the production of complex, previously un-manufacturable, geometries. However, significant challenges remain in understanding the complex material transfer and heat transfer mechanisms which take pace during the many melting and re-melting cycles during processing. In particular, the mechanism leading to the formation of ejecta (e.g. spatter), commonly observed during processing, and their influence on build quality remains in dispute. To date, little is known regarding the mechanisms by which spattered particles form or how they influence flaw formation processes in powder bed fusion additive manufacturing. Models of the PBFAM process have proven useful in better understanding melt pool dynamics and in showing that melt ejection and powder denudation play important roles in the process 3,4. More recently, high-speed imaging has been used to argue that ejecta primarily forms, not as a result of melt ejection, but due to evaporation-driven entrainment of powder 5. Though, according to Ly et al. 5 , when melt ejection does occur in PBFAM, it tends to produce ejecta on the order of 25-100 μm in size. This is because the kinetic energy of ejected melt must exceed the capillary pressure of the melt (surface tension divided by the melt's radius of curvature). Hence, larger melt droplets are more likely to be ejected; powder enhances this effect by hindering forward motion of the melt. Nevertheless, entrained particles-of a similar size distribution as the feedstock powder particles-are argued to form approximately 85% of spatter. Of this portion, about 60% are described as "hot" 5. High-speed X-ray imaging of the PBFAM process 6 reinforces, and adds to, the findings of Ly et al. 5. Again, evaporation-driven entrainment of particles, due to flows of metal vapor and ambient gas, is identified as the primary mechanism for spatter formation. The proportion of hot particles also appears to depend on environmental pressure 6. Interestingly, both works 5,6 maintain that larger spatter particles are likely due to melt ejection, while entrained particles have similar size distributions to the feedstock powder. Though it should be noted that Ly et al. 5 do show the formation of large particles through the collision and merging of neighboring, hot droplets

Journal of fluids and structures, 2018

In this work, a non-reflective boundary condition, the Perfectly Matched Layer (PML) technique, i... more In this work, a non-reflective boundary condition, the Perfectly Matched Layer (PML) technique, is adapted and implemented in a fluid-structure interaction numerical framework to demonstrate that proper boundary conditions are not only necessary to capture correct wave propagations in a flow field, but also its interacted solid behavior and responses. While most research on the topics of the non-reflective boundary conditions are focused on fluids, little effort has been done in a fluid-structure interaction setting. In this study, the effectiveness of the PML is closely examined in both pure fluid and fluid-structure interaction settings upon incorporating the PML algorithm in a fully-coupled fluid-structure interaction framework, the Immersed Finite Element Method. The performance of the PML boundary condition is evaluated and compared to reference solutions with a variety of benchmark test cases including known and expected solutions of aeroacoustic wave propagation as well as vo...

Computer Methods in Applied Mechanics and Engineering

In this study, a fully-coupled fluid-structure interaction model is developed for studying dynami... more In this study, a fully-coupled fluid-structure interaction model is developed for studying dynamic interactions between compressible fluid and aeroelastic structures. The technique is built based on the modified Immersed Finite Element Method (mIFEM), a robust numerical technique to simulate fluid-structure interactions that has capabilities to simulate high Reynolds number flows and handles large density disparities between the fluid and the solid. For accurate assessment of this intricate dynamic process between compressible fluid, such as air and aeroelastic structures, we included in the model the fluid compressibility in an isentropic process and a solid contact model. The accuracy of the compressible fluid solver is verified by examining acoustic wave propagations in a closed and an open duct, respectively. The fully-coupled fluid-structure interaction model is then used to simulate and analyze vocal folds vibrations using compressible air interacting with vocal folds that are represented as layered viscoelastic structures. Using physiological geometric and parametric setup, we are able to obtain a self-sustained vocal fold vibration with a constant inflow pressure. Parametric studies are also performed to study the effects of lung pressure and vocal fold tissue stiffness in vocal folds vibrations. All the case studies produce expected airflow behavior and a sustained vibration, which provide verification and confidence in our future studies of realistic acoustical studies of the phonation process.

Measurement Science and Technology

ABSTRACT Color crosstalk and chromatic aberration can bias estimates of fluid velocity measured b... more ABSTRACT Color crosstalk and chromatic aberration can bias estimates of fluid velocity measured by color particle shadow velocimetry (CPSV), using multicolor illumination and a color camera. This article describes corrections to remove these bias errors, and their evaluation. Color crosstalk removal is demonstrated with linear unmixing. It is also shown that chromatic aberrations may be removed using either scale calibration, or by processing an image illuminated by all colors simultaneously. CPSV measurements of a fully developed turbulent pipe flow of glycerin were conducted. Corrected velocity statistics from these measurements were compared to both single-color PSV and LDV measurements and showed excellent agreement to fourth-order, to well into the viscous sublayer. Recommendations for practical assessment and correction of color aberration and color crosstalk are discussed.

Aps Division of Fluid Dynamics Meeting Abstracts, Nov 1, 2007

Aps Division of Fluid Dynamics Meeting Abstracts, Nov 1, 2003

The effect of transverse curvature on boundary layer structure is studied using DPIV measurements... more The effect of transverse curvature on boundary layer structure is studied using DPIV measurements of the velocity field in the boundary layer of an axial flow over a series of small radius cables. Of particular interest is the occurrence of relaminarixation for small transverse curvature. Velocity measurements in the r-z and r-q planes are presented as radial profiles of mean

Experimental results derived from DPIV measurements in a scaled up dynamic human vocal fold model... more Experimental results derived from DPIV measurements in a scaled up dynamic human vocal fold model are presented. The 10x scale vocal fold model is a new design that incorporates key features of vocal fold oscillatory motion. This includes coupling of down/upstream ...

Aps Division of Fluid Dynamics Meeting Abstracts, Nov 1, 2006

The behavior of the starting vortex issuing from a time-varying rectangular slit with an imposed ... more The behavior of the starting vortex issuing from a time-varying rectangular slit with an imposed pressure gradient, representing the flow through the human glottis, is presented. The range of reduced frequency of vibration was 0.01-0.04 and the Reynolds number ...

Experiments were conducted in a compliant, self-oscillating model of the glottis in a large free-... more Experiments were conducted in a compliant, self-oscillating model of the glottis in a large free-surface water tunnel. The in vitro model was geometrically similar to the human vocal folds, allowing a greater understanding of fluid-solid coupling, but was not dynamically ...

ABSTRACT The phonation process occurs as air expelled from the lungs creates a pressure drop and ... more ABSTRACT The phonation process occurs as air expelled from the lungs creates a pressure drop and a subsequent air flow across the larynx. The fluid-structure interaction between the turbulent air flow and oscillating vocal folds, combined with additional resonance in the oral and nasal cavities, creates much of what we hear in the human voice. As many voice-related disorders can be traced to irregular vocal tract shape or motion, it is important to understand in detail the physics involved in the phonation process. To numerically compute the physics of phonation, a solver must be able to accurately model acoustic airflow through a moving domain. The open-source CFD package OpenFOAM is currently being used to evaluate existing solvers against simple acoustic test cases, including an open-ended resonator and an expansion chamber, both of which utilize boundary conditions simulating acoustic sources as well as anechoic termination. Results of these test cases will be presented and compared with theory, and the future development of a three-dimensional vocal tract model and custom-mode acoustic solver will be discussed.

Fluid Dynamics Research, 2019

Spatially and temporally resolved Digital Particle Image Velocimetry (DPIV) measurements are pres... more Spatially and temporally resolved Digital Particle Image Velocimetry (DPIV) measurements are presented of flow complexities in a nominally two-dimensional, symmetric, duct with an oscillating constriction. The motivation for this research lies in advancing the state-of-the-art in applying integral control volume analysis to modeling unsteady internal flows. The specific target is acoustic modeling of human phonation. The integral mass and momentum equations are directly coupled to the acoustic equations and provide quantitative insight into acoustic source strengths in addition to the dynamics of the fluid-structure interactions in the glottis. In this study, a square cross-section duct was constructed with symmetric, computer controlled, oscillating constrictions that incorporate both rocking as well as oscillatory open/close motions. Experiments were run in a free-surface water tunnel over a Strouhal number range, based on maximum jet speed and model length, of 0.012-0.048, for a fixed Reynolds number, based on maximum gap opening and maximum jet speed, of 8000. In this study, the constriction motions were continuous with one open-close cycle immediately following another. While the model and its motions were nominally two-dimensional and symmetric, flow asymmetries and oscillation frequency dependent cycle-tocycle variations were observed. These are examined in the context of terms in the integral conservation equations.

Journal of the American Helicopter Society

A 1:4.25-scale model of a generic helicopter rotor hub was tested at Reynolds numbers ranging fro... more A 1:4.25-scale model of a generic helicopter rotor hub was tested at Reynolds numbers ranging from 1.75 × 106 to 7 × 106 at advance ratio of 0.2 in The Pennsylvania State University Applied Research Laboratory Garfield Thomas 48-inch diameter water tunnel. Measurements including drag and wake characteristics were performed up to full-scale Reynolds number with respect to an industry-representative helicopter rotor hub. In particular, the variation of drag and flow field with Reynolds number was characterized. Load measurements were conducted using an improved load cell design, with greater accuracy than in previous experiments. Wake velocity was measured using laser Doppler velocimetry at two downstream planes, yielding velocity statistics to the second order. Improved load measurement accuracy and wake velocity spatial resolution, at full-scale Reynolds number, provide a unique dataset for computational fluid dynamics validation as part of the Penn State Rotor Hub Flow Prediction W...

Experiments in Fluids, 2018

The integral length scale can be calculated from planar particle image velocimetry (PIV) data by ... more The integral length scale can be calculated from planar particle image velocimetry (PIV) data by integrating a two-point velocity correlation over a range of in-plane spatial separations. However, the field of view restricts the integral scale that can be measured by limiting the integration domain. This limitation can be overcome if multiple planes are imaged, and velocity is correlated along the out-of-plane direction. Multiplane particle shadow velocimetry (PSV) is introduced for this purpose. A backlight is used to illuminate particles in the flow field, rather than a laser sheet as in PIV. These illuminated particles obstruct light from entering the camera, thus appearing dark. The combination of two colors in the backlight and a dichroic mirror makes possible the simultaneous imaging of two planes. Separated along the the out-of-plane direction (the optical axis), the multiple imaged planes allow for an integral length scale to be measured independent of the field of view. Experiments were conducted in the axisymmetric 285 mm diameter glycerin tunnel at Penn State's Applied Research Laboratory. Turbulence statistics calculated using multiplane PSV are consistent with those obtained using planar PSV and laser Doppler velocimetry (LDV) at the same facility. The temporal autocorrelation and the integral timescale, measured with planar and multiplane PSV, agree within 95% confidence. The two-point velocity correlation separated spatially along the in-plane radial direction is the same, within 95% confidence, as that separated spatially along the out-of-plane radial direction. The former is insufficient for calculating an integral length scale due to its limited domain. Integrating the latter yields an integral length scale equal to 11% of the radius of the tunnel.

Journal of Biomechanics, 2006

Proceedings of the 10th International Symposium on Cavitation (CAV2018), 2018

Statistics of tip vortex core pressure are estimated from instantaneous Stereo PIV measurements o... more Statistics of tip vortex core pressure are estimated from instantaneous Stereo PIV measurements of the velocity field. The tip vortex was generated by a rectangular planform (aspect ratio 2), elliptically-loaded fin with a NACA66 foil shape. A set of 500 velocity field realizations were acquired at each of three angles of attack. Estimates of pressure for each measured velocity field were computed using a finiteelement scheme that minimized error propagation from the measured velocity field. Histograms of core pressure show that the mean core pressure followed expected scaling with vortex strength, and that the width of the distribution is inversely proportional to vortex strength.

The Journal of the Acoustical Society of America

This paper presents measurements conducted in a physical model of the adult human airway. The goa... more This paper presents measurements conducted in a physical model of the adult human airway. The goals of this work are to (1) benchmark the physical model to excised larynx models in the literature and (2) empirically demonstrate the relationship between vocal fold drag and sound production. Results from the airway model are first benchmarked to published time-averaged behavior of excised larynx models. The airway model in this work exhibited higher glottal volume flow, lower glottal resistance, and less fundamental frequency variation than excised larynx models. Next, concurrent measurements of source behavior and radiated sound were compared. Unsteady transglottal pressure (a surrogate measure for vocal fold drag) and radiated sound, measured at the mouth, showed good correlation. In particular, the standard deviation and the ratio of the power of the first and second harmonics of the transglottal and mouth pressures were strongly correlated. This empirical result supports the assertion that vocal fold drag is the principal source of sound in phonation.

The Journal of the Acoustical Society of America

Scientific Reports

ejecta with a size much larger than the mean particle size of feedstock powder have been observed... more ejecta with a size much larger than the mean particle size of feedstock powder have been observed in powder bed fusion additive manufacturing, both during post-process sieving and embedded within built components. However, their origin has not been adequately explained. Here, we test a hypothesis on the origin of large (much larger than the mass-median-diameter of feedstock powder) ejecta-that, in part, they result from stochastic, inelastic collisions of ejecta and coalescence of partially-sintered agglomerates. the hypothesis is tested using direct observation of ejecta behavior, via high-speed imaging, to identify interactions between ejecta and consequences on melt pool formation. We show that stochastic collisions occur both between particles which are nearly-simultaneously expelled from the laser interaction zone and between particles ejected from distant locations. ejecta are also shown to perturb melt pool geometry, which is argued to be a potential cause of lack-of-fusion flaws. Laser powder bed fusion additive manufacturing (PBFAM), a subcategory of metal 3D printing technology, is rapidly emerging as an important industrial manufacturing technology for aerospace, medical, and defense applications 1,2. The process, which relies on sequential melting of powder layers on the order of tens of microns in thickness, is useful for the production of complex, previously un-manufacturable, geometries. However, significant challenges remain in understanding the complex material transfer and heat transfer mechanisms which take pace during the many melting and re-melting cycles during processing. In particular, the mechanism leading to the formation of ejecta (e.g. spatter), commonly observed during processing, and their influence on build quality remains in dispute. To date, little is known regarding the mechanisms by which spattered particles form or how they influence flaw formation processes in powder bed fusion additive manufacturing. Models of the PBFAM process have proven useful in better understanding melt pool dynamics and in showing that melt ejection and powder denudation play important roles in the process 3,4. More recently, high-speed imaging has been used to argue that ejecta primarily forms, not as a result of melt ejection, but due to evaporation-driven entrainment of powder 5. Though, according to Ly et al. 5 , when melt ejection does occur in PBFAM, it tends to produce ejecta on the order of 25-100 μm in size. This is because the kinetic energy of ejected melt must exceed the capillary pressure of the melt (surface tension divided by the melt's radius of curvature). Hence, larger melt droplets are more likely to be ejected; powder enhances this effect by hindering forward motion of the melt. Nevertheless, entrained particles-of a similar size distribution as the feedstock powder particles-are argued to form approximately 85% of spatter. Of this portion, about 60% are described as "hot" 5. High-speed X-ray imaging of the PBFAM process 6 reinforces, and adds to, the findings of Ly et al. 5. Again, evaporation-driven entrainment of particles, due to flows of metal vapor and ambient gas, is identified as the primary mechanism for spatter formation. The proportion of hot particles also appears to depend on environmental pressure 6. Interestingly, both works 5,6 maintain that larger spatter particles are likely due to melt ejection, while entrained particles have similar size distributions to the feedstock powder. Though it should be noted that Ly et al. 5 do show the formation of large particles through the collision and merging of neighboring, hot droplets

Journal of fluids and structures, 2018

In this work, a non-reflective boundary condition, the Perfectly Matched Layer (PML) technique, i... more In this work, a non-reflective boundary condition, the Perfectly Matched Layer (PML) technique, is adapted and implemented in a fluid-structure interaction numerical framework to demonstrate that proper boundary conditions are not only necessary to capture correct wave propagations in a flow field, but also its interacted solid behavior and responses. While most research on the topics of the non-reflective boundary conditions are focused on fluids, little effort has been done in a fluid-structure interaction setting. In this study, the effectiveness of the PML is closely examined in both pure fluid and fluid-structure interaction settings upon incorporating the PML algorithm in a fully-coupled fluid-structure interaction framework, the Immersed Finite Element Method. The performance of the PML boundary condition is evaluated and compared to reference solutions with a variety of benchmark test cases including known and expected solutions of aeroacoustic wave propagation as well as vo...

Computer Methods in Applied Mechanics and Engineering

In this study, a fully-coupled fluid-structure interaction model is developed for studying dynami... more In this study, a fully-coupled fluid-structure interaction model is developed for studying dynamic interactions between compressible fluid and aeroelastic structures. The technique is built based on the modified Immersed Finite Element Method (mIFEM), a robust numerical technique to simulate fluid-structure interactions that has capabilities to simulate high Reynolds number flows and handles large density disparities between the fluid and the solid. For accurate assessment of this intricate dynamic process between compressible fluid, such as air and aeroelastic structures, we included in the model the fluid compressibility in an isentropic process and a solid contact model. The accuracy of the compressible fluid solver is verified by examining acoustic wave propagations in a closed and an open duct, respectively. The fully-coupled fluid-structure interaction model is then used to simulate and analyze vocal folds vibrations using compressible air interacting with vocal folds that are represented as layered viscoelastic structures. Using physiological geometric and parametric setup, we are able to obtain a self-sustained vocal fold vibration with a constant inflow pressure. Parametric studies are also performed to study the effects of lung pressure and vocal fold tissue stiffness in vocal folds vibrations. All the case studies produce expected airflow behavior and a sustained vibration, which provide verification and confidence in our future studies of realistic acoustical studies of the phonation process.

Measurement Science and Technology

ABSTRACT Color crosstalk and chromatic aberration can bias estimates of fluid velocity measured b... more ABSTRACT Color crosstalk and chromatic aberration can bias estimates of fluid velocity measured by color particle shadow velocimetry (CPSV), using multicolor illumination and a color camera. This article describes corrections to remove these bias errors, and their evaluation. Color crosstalk removal is demonstrated with linear unmixing. It is also shown that chromatic aberrations may be removed using either scale calibration, or by processing an image illuminated by all colors simultaneously. CPSV measurements of a fully developed turbulent pipe flow of glycerin were conducted. Corrected velocity statistics from these measurements were compared to both single-color PSV and LDV measurements and showed excellent agreement to fourth-order, to well into the viscous sublayer. Recommendations for practical assessment and correction of color aberration and color crosstalk are discussed.

Aps Division of Fluid Dynamics Meeting Abstracts, Nov 1, 2007

Aps Division of Fluid Dynamics Meeting Abstracts, Nov 1, 2003

The effect of transverse curvature on boundary layer structure is studied using DPIV measurements... more The effect of transverse curvature on boundary layer structure is studied using DPIV measurements of the velocity field in the boundary layer of an axial flow over a series of small radius cables. Of particular interest is the occurrence of relaminarixation for small transverse curvature. Velocity measurements in the r-z and r-q planes are presented as radial profiles of mean

Experimental results derived from DPIV measurements in a scaled up dynamic human vocal fold model... more Experimental results derived from DPIV measurements in a scaled up dynamic human vocal fold model are presented. The 10x scale vocal fold model is a new design that incorporates key features of vocal fold oscillatory motion. This includes coupling of down/upstream ...

Aps Division of Fluid Dynamics Meeting Abstracts, Nov 1, 2006

The behavior of the starting vortex issuing from a time-varying rectangular slit with an imposed ... more The behavior of the starting vortex issuing from a time-varying rectangular slit with an imposed pressure gradient, representing the flow through the human glottis, is presented. The range of reduced frequency of vibration was 0.01-0.04 and the Reynolds number ...

Experiments were conducted in a compliant, self-oscillating model of the glottis in a large free-... more Experiments were conducted in a compliant, self-oscillating model of the glottis in a large free-surface water tunnel. The in vitro model was geometrically similar to the human vocal folds, allowing a greater understanding of fluid-solid coupling, but was not dynamically ...

ABSTRACT The phonation process occurs as air expelled from the lungs creates a pressure drop and ... more ABSTRACT The phonation process occurs as air expelled from the lungs creates a pressure drop and a subsequent air flow across the larynx. The fluid-structure interaction between the turbulent air flow and oscillating vocal folds, combined with additional resonance in the oral and nasal cavities, creates much of what we hear in the human voice. As many voice-related disorders can be traced to irregular vocal tract shape or motion, it is important to understand in detail the physics involved in the phonation process. To numerically compute the physics of phonation, a solver must be able to accurately model acoustic airflow through a moving domain. The open-source CFD package OpenFOAM is currently being used to evaluate existing solvers against simple acoustic test cases, including an open-ended resonator and an expansion chamber, both of which utilize boundary conditions simulating acoustic sources as well as anechoic termination. Results of these test cases will be presented and compared with theory, and the future development of a three-dimensional vocal tract model and custom-mode acoustic solver will be discussed.