Fluid structure interactions occur to some extent in nearly every type of fluid flow. Understanding how structures interact with fluids and visa-versa is of vital importance in many engineering applications. The purpose of this research is to explore how fluids interact with flexible and rigid structures. A computational model was used to model the fluid structure interactions of vibrating synthetic vocal folds. The model simulated the coupling of the fluid and solid domains using a fluid-structure interface boundary condition. The fluid domain used a slightly compressible flow solver to allow for the possibility of acoustic coupling with the subglottal geometry and vibration of the vocal fold model. As the subglottis lengthened, the frequency of vibration decreased until a new acoustic mode could form in the subglottis. Synthetic aperture particle image velocimetry (SAPIV) is a three-dimensional particle tracking technique. SAPIV was used to image the jet of air that emerges from vibrating human vocal folds (glottal jet) during phonation. The three-dimensional reconstruction of the glottal jet found faint evidence of flow characteristics seen in previous research, such as axis-switching, but did not have sufficient resolution to detect small features. SAPIV was further applied to reconstruct the smaller flow characteristics of the glottal jet of vibrating synthetic vocal folds. Two- and four-layer synthetic vocal fold models were used to determine how the glottal jet from the synthetic models compared to the glottal jet from excised human vocal folds. The two- and four-layer models clearly exhibited axis-switching which has been seen in other 3D analyses of the glottal jet. Cavitation in a quiescent fluid can break a rigid structure such as a glass bottle. A new cavitation number was derived to include acceleration and pressure head at cavitation onset. A cavitation stick was used to validate the cavitation number by filling it with different depths and hitting the stick to cause fluid cavitation. Acceleration was measured using an accelerometer and cavitation bubbles were detected using a high-speed camera. Cavitation in an accelerating fluid occurred at a cavitation number of 1.

Voice quality is strongly linked to quality of life; those who suffer from voice disorders are adversely affected in their social, family, and professional relationships. An effort has been made to more fully understand the physics behind how the voice is created, specifically the fluid structure interactions that occur during vocal fold vibration. Many techniques have been developed and implemented to study both the motion of the vocal folds and the airflow that creates the motion. Until recently these techniques have sought to understand a highly three-dimensional phenomenon with 1D or 2D perspectives.This research focuses on the development and implementation of an experimental technique to obtain three-dimensional characterizations of vocal fold motion and fluid flow. Experiments were performed on excised human vocal fold models at the University Hospital Erlangen Medical School in Erlangen, Germany. A novel technique for tracking the motion of the vocal folds using multiple camera viewpoints and limited user interaction was developed. Four high-speed cameras (2000 fps) recorded an excised vocal fold model vibrating at 250 Hz. Based on the images from these four cameras a fully 3D reconstruction of the superior surface of the vocal folds was achieved. The 3D reconstruction of 70 consecutive time steps was assembled to characterize the motion of the vocal folds over eight cycles. The 3D reconstruction accurately modeled the observed behavior of vocal fold vibration with a clearly visible mucosal wave. The average reprojection error for this technique was on par with other contemporary techniques (~20 micrometers). A whole field, time resolved, three-dimensional reconstruction of the vocal fold fluid flow was obtained using synthetic aperture particle image velocimetry. Simultaneous 3D flow fields, subglottal pressure waves, and superior surface motion were presented for 2 consecutive cycles of oscillation. The vocal fold fluid flow and motion measurements correlated with behavior observed in previous three-dimensional studies. A higher resolution view of one full cycle of oscillation was compiled from 16 time resolved data sets via pressure data. The result was a full three-dimensional characterization of the evolution and disintegration of the glottal jet.

This thesis examines two important problems in fluid dynamics: that of a partially immersed sphere spinning in a bath of liquid and the measurement of flow velocities around a free flying butterfly. Although the actual problems are quite different, each problem incorporates many of the same principles and techniques. When a hard-boiled egg spins through a pool of milk on the kitchen counter, the milk rises up the sides of the egg and droplets are ejected. This phenomenon occurs when any partially submerged object whose radius increases upward from the fluid surface (e.g., spheres, inverted cones, rings, etc.), spins in a shallow bath of fluid. The fluid ejects from the surface at the maximum diameter in one of three ejection modes: jets, sheets, or sheet breakup. Additionally, a surprisingly large flow rate is induced by the spinning object. Spheres are used in this study to determine the effects of experimental parameters on the induced flow rate. High-speed imaging is used to experimentally characterize the modes of ejection and measure sheet breakup distance and velocities of liquid within liquid sheets. A theoretical model is derived using an integral momentum boundary layer analysis both beneath the free surface and in the thin film attached to the sphere. Experimental results are presented in comparison with predicted behavior with good agreement. The suitability of using a spinning sphere as a pump is also discussed. Second, the use of PIV to measure flow velocities around living species is becoming more widely adopted. Current efforts are starting to measure 3D, time-resolved velocities around insects in tethered flight. This work investigates the use of Synthetic Aperture PIV (SAPIV) in obtaining 3D, time-resolved volumetric velocity fields around a painted lady butterfly in free flight. Results are presented from several time steps during both the down stroke and upstroke of the butterfly showing the development of the leading edge vortex. The velocity field results have limited spatial resolution; however, the results show that SAPIV has potential in further investigating these flow structures. The reconstructed visual hull of the butterfly is also discussed.

This work presents the development and analysis of a system that combines the concepts of light field microscopy and particle image velocimetry (PIV) to measure three-dimensional velocities within a microvolume. Rectanglar microchannels were fabricated with dimensions on the order of 350-950 micrometers using a photolithographic process and polydimethylsiloxane (PDMS). The flow was seeded with fluorescent particles and pumped through microchannels at Reynolds numbers ranging from 0.016 to 0.028. Flow at Reynolds numbers in the range of 0.02 to 0.03 was seeded with fluorescent particles and pumped through microchannels. A light field microscope with a lateral resolution of 6.25 micrometers and an axial resolution of 15.5 micrometers was designed and built based on the concepts described by Levoy et al. Light field images were captured continuously at a frame rate of 3.9 frames per second using a Canon 5D Mark II DSLR camera. Each image was post processed to render a stack of two-dimensional images. The focal stacks were further post processed using various methods including bandpass filtering, 3D deconvolution, and intensity-based thresholding, to remove effects of diffraction and blurring. Subsequently, a multi-pass, three-dimensional PIV algorithm was used to measure channel velocities. Results from PIV analysis were compared with an analytical solution for fully-developed cases, and with CFD simulations for developing flows. Relative errors for fully-developed flow measurements, within the light field microscope refocusing range, were approximately 5% or less. Overall, the main limitations are the reduction in lateral resolution, and the somewhat low axial resolution. Advantages include the relatively low cost, ease of incorporation into existing micro-PIV systems, simple self-calibration process, and potential for resolving instantaneous three-dimensional velocities in a microvolume.