Bulletin of the American Physical Society
67th Annual Meeting of the APS Division of Fluid Dynamics
Volume 59, Number 20
Sunday–Tuesday, November 23–25, 2014; San Francisco, California
Session R7: Biofluids: Mechanics of Swallowing and Speech |
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Chair: Kartik Bulusu, The George Washington University Room: 3012 |
Tuesday, November 25, 2014 1:05PM - 1:18PM |
R7.00001: Mosquitoes drink with a burst in reserve: explaining pumping behavior with a fluid mechanics model Souvick Chatterjee, Jake Socha, Mark Stremler Mosquitoes drink using a pair of in-line pumps in the head that draw liquid food through the proboscis. Experimental observations with synchrotron x-ray imaging indicate two modes of drinking: a predominantly occurring continuous mode, in which the cibarial and pharyngeal pumps expand cyclically at a constant phase difference, and an occasional, isolated burst mode, in which the pharyngeal pump expansion is 10 to 30 times larger than in the continuous mode. We have used a reduced order model of the fluid mechanics to hypothesize an explanation of this variation in drinking behavior. Our model results show that the continuous mode is more energetically efficient, whereas the burst mode creates a large pressure drop across the proboscis, which could potentially be used to clear blockages. Comparisons with pump knock-out configurations demonstrate different functional roles of the pumps in mosquito feeding. [Preview Abstract] |
Tuesday, November 25, 2014 1:18PM - 1:31PM |
R7.00002: How dogs drink water Sean Gart, Jake Socha, Pavlos Vlachos, Sunghwan Jung Animals with incomplete cheeks (i.e. dogs and cats) need to move fluid against gravity into the body by means other than suction. They do this by lapping fluid with their tongue. When a dog drinks, it curls its tongue posteriorly while plunging it into the fluid and then quickly withdraws its tongue back into the mouth. During this fast retraction fluid sticks to the ventral part of the curled tongue and is drawn into the mouth due to inertia. We show several variations of this drinking behavior among many dog breeds, specifically, the relationship between tongue dynamics and geometry, lapping frequency, and dog weight. We also compare the results with the physical experiment of a rounded rod impact onto a fluid surface. [Preview Abstract] |
Tuesday, November 25, 2014 1:31PM - 1:44PM |
R7.00003: Influence of muscle activation and mucosal material property on esophageal transport: study based on a fully-resolved computational model Wenjun Kou, John Pandolfino, Peter Kahrilas, Neelesh Patankar Esophageal transport involves interactions between food (bolus), the esophageal walls (composed of mucosal, circular muscle (CM) and longitudinal muscle (LM) layers), and neurally coordinated muscle activation including CM contraction and LM shortening. Due to the complexity of these interactions, few studies have been conducted on the mechanical role of the mucosal layer in esophageal transport. Also poorly understood are the collaborative roles of CM contraction and LM shortening and the influence of their synchronization. Here, based on a fully-resolved computational model that we developed, we investigated the individual roles of CM contraction and LM shortening, compared bolus transport with various levels of discoordination between CM and LM activation, and studied the role of the mucosa and how its stiffening influenced transport. These preliminary findings should help understand the synergy between LM, CM, and the mucosal layer in facilitating bolus transport, thereby providing insight into related physiology and pathophysiology. [Preview Abstract] |
Tuesday, November 25, 2014 1:44PM - 1:57PM |
R7.00004: 3D separation over a wall-mounted hemisphere in steady and pulsatile flow Ian A. Carr, Michael W. Plesniak Flow separation over a surface-mounted hemispheriod is prevalent in countless applications, both under steady (constant freestream velocity) and unsteady flow over the protuberance. Previous studies of 3D separation have been limited to steady inflow conditions. In biological and geophysical flows, pulsatile flow conditions are much more commonly observed, yet such conditions have not been well studied. Primarily motivated by previous studies of the flow observed in various human vocal fold pathologies, such as polyps, our research aims to fill the knowledge gap in unsteady 3D flow separation. This is achieved by characterizing surface pressure fields and velocity fields, focused primarily on the vortical flow structures and dynamics that occur around a hemispheroid protuberance under pulsatile flow conditions. Surface static pressure and two-dimensional, instantaneous and phase-averaged, particle image velocimetry data in steady and pulsatile flow are presented and compared. Coherent vortical flow structures have been identified using the $\lambda_{ci}$ vortex identification criterion. This analysis has revealed a novel set of flow structures dependent on the pulsatile flow forcing function. [Preview Abstract] |
Tuesday, November 25, 2014 1:57PM - 2:10PM |
R7.00005: Wavelet analysis of hemispheroid flow separation toward understanding human vocal fold pathologies Daniel H. Plesniak, Ian A. Carr, Kartik V. Bulusu, Michael W. Plesniak Physiological flows observed in human vocal fold pathologies, such as polyps and nodules, can be modeled by flow over a wall-mounted protuberance. The experimental investigation of flow separation over a surface-mounted hemispheroid was performed using particle image velocimetry (PIV) and measurements of surface pressure in a low-speed wind tunnel. This study builds on the hypothesis that the signatures of vortical structures associated with flow separation are imprinted on the surface pressure distributions. Wavelet decomposition methods in one- and two-dimensions were utilized to elucidate the flow behavior. First, a complex Gaussian wavelet was used for the reconstruction of surface pressure time series from static pressure measurements acquired from ports upstream, downstream, and on the surface of the hemispheroid. This was followed by the application of a novel continuous wavelet transform algorithm (PIVlet 1.2) using a 2D-Ricker wavelet for coherent structure detection on instantaneous PIV-data. The goal of this study is to correlate phase shifts in surface pressure with Strouhal numbers associated with the vortex shedding. Ultimately, the wavelet-based analytical framework will be aimed at addressing pulsatile flows. [Preview Abstract] |
Tuesday, November 25, 2014 2:10PM - 2:23PM |
R7.00006: Characterizing phonatory aeroacoustic sources using Lagrangian Coherent Structures Michael McPhail, Michael Krane Voice disorders that lead to changes in vocal fold geometry, or posturing, are known to substantially affect phonatory airflow topology. How these topology changes affect aeroacoustic sound sources is not well understood, however. This talk presents modelling aeroacoustic sources with Lagrangian Coherent Structures (LCS). Here we use the motion of dynamically distinct fluid regions, identified by the LCS, to predict sound. This approach provides a means to connect phonatory airflow topology changes to resulting changes in sound production. Simple validation cases of this approach will be shown. The application of LCS analysis to phonatory flows will be also presented. [Preview Abstract] |
Tuesday, November 25, 2014 2:23PM - 2:36PM |
R7.00007: Self-oscillating Vocal Fold Model Mechanics: Healthy, Diseased, and Aging Elizabeth P. Hiubler, Lucas F. E. Pollok, Adam G. Apostoli, Adrienne B. Hancock, Michael W. Plesniak Voice disorders have been estimated to have a substantial economic impact of \$2.5 billion annually. Approximately 30\% of people will suffer from a voice disorder at some point in their lives. Life-sized, self-oscillating, synthetic vocal fold (VF) models are fabricated to exhibit material properties representative of human VFs. These models are created both with and without a polyp-like structure, a pathology that has been shown to produce rich viscous flow structures not normally observed for healthy VFs during normal phonation. Pressure measurements are acquired upstream of the VFs and high-speed images are captured at varying flow rates during VF oscillation to facilitate an understanding of the characteristics of healthy and diseased VFs. The images are analyzed using a videokymography line-scan technique. Clinically-relevant parameters calculated from the volume-velocity output of a circumferentially-vented mask (Rothenberg mask) are compared to human data collected from two groups of males aged 18-30 and 60-80. This study extends the use of synthetic VF models by assessing their ability to replicate behaviors observed in human subject data to advance a means of investigating changes associated with normal, pathological, and the aging voice. [Preview Abstract] |
Tuesday, November 25, 2014 2:36PM - 2:49PM |
R7.00008: Combining subject-specific and low-order modeling techniques to study fluid-structure interaction of rabbit phonation Siyuan Chang, Haoxiang Luo, Carolyn Novaleski, Bernard Rousseau A subject-specific computational model has been developed to simulate flow-induced vocal fold vibration for evoked rabbit phonation. A freshly excised larynx was scanned using micro magnetic resonance imaging. Images were segmented to identify the vocal fold tissue and lumen surface. The 3D fluid-structure interaction (FSI) model was then constructed with experimentally measured flow parameters as input. The tissue deformation is assumed to be finite, and a previously developed FSI solver is used to simulate the coupled flow and nonlinear tissue mechanics. In addition, a one-dimensional flow model based on heuristic estimate of the flow separation point is used as an efficient tool to guide the full 3D simulation. This low-order model is motivated by presence of uncertainties in the tissue properties and boundary conditions, and it has proven to be very useful in our study. Similarities and differences in the vibration characteristics of the vocal fold predicted by these two models will be discussed. [Preview Abstract] |
Tuesday, November 25, 2014 2:49PM - 3:02PM |
R7.00009: Study of non-linear deformation of vocal folds in simulations of human phonation Shakti Saurabh, Daniel Bodony Direct numerical simulation is performed on a two-dimensional compressible, viscous fluid interacting with a non-linear, viscoelastic solid as a model for the generation of the human voice. The vocal fold (VF) tissues are modeled as multi-layered with varying stiffness in each layer and using a finite-strain Standard Linear Solid (SLS) constitutive model implemented in a quadratic finite element code and coupled to a high-order compressible Navier-Stokes solver through a boundary-fitted fluid-solid interface. The large non-linear mesh deformation is handled using an elliptic/poisson smoothening technique. Supra-glottal flow shows asymmetry in the flow, which in turn has a coupling effect on the motion of the VF. The fully compressible simulations gives direct insight into the sound produced as pressure distributions and the vocal fold deformation helps study the unsteady vortical flow resulting from the fluid-structure interaction along the full phonation cycle. [Preview Abstract] |
Tuesday, November 25, 2014 3:02PM - 3:15PM |
R7.00010: Simulations of acoustic waves in channels and phonation in glottal ducts Jubiao Yang, Michael Krane, Lucy Zhang Numerical simulations of acoustic wave propagation were performed by solving compressible Navier-Stokes equations using finite element method. To avoid numerical contamination of acoustic field induced by non-physical reflections at computational boundaries, a Perfectly Matched Layer (PML) scheme was implemented to attenuate the acoustic waves and their reflections near these boundaries. The acoustic simulation was further combined with the simulation of interaction of vocal fold vibration and glottal flow, using our fully-coupled Immersed Finite Element Method (IFEM) approach, to study phonation in the glottal channel. In order to decouple the aeroelastic and aeroacoustic aspects of phonation, the airway duct used has a uniform cross section with PML properly applied. The dynamics of phonation were then studied by computing the terms of the equations of motion for a control volume comprised of the fluid in the vicinity of the vocal folds. It is shown that the principal dynamics is comprised of the near cancellation of the pressure force driving the flow through the glottis, and the aerodynamic drag on the vocal folds. Aeroacoustic source strengths are also presented, estimated from integral quantities computed in the source region, as well as from the radiated acoustic field. [Preview Abstract] |
Tuesday, November 25, 2014 3:15PM - 3:28PM |
R7.00011: Measurements of phonatory aeroacoustic source strengths in a physical model Michael Krane, Michael McPhail Aeroacoustic sources due to flow-induced vibration of a compliant constriction in a duct were characterized experimentally. The principal goal of this study is to estimate the character and level of the various sources of sound in human voice production. Measurements were performed in a model of the human airway, constructed to human dimensions, but with an idealized geometry. The airway duct models the passage from the trachea to the mouth, as a constant-area (7.64cm$^{2})$ square cross-section, interrupted only by the model vocal folds. These were fabricated in two layers of soft silicone rubber. Time-resolved measurements included subglottal and supraglottal absolute pressure, sound pressure at the model vocal tract ``mouth,'' and high-speed video of the model vocal folds. These were sampled synchronously at 22 kHz. Steady-state measurements included subglottal pressure and volume flow rate. Measurements were conducted over a subglottal pressures range of 2.25-2.80 kPa. Source strengths were estimated by theoretical expressions, using the measured pressures and glottal area as inputs. Results show that the dipole source typically associated with vocal fold drag is the dominant source. Furthermore, for the vibration pattern observed in these experiments, glottal jet turbulence dominates the dipole source above approximately 1 kHz. [Preview Abstract] |
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