Methods and Analysis of Multiphase Flow and Interfacial Phenomena in Medical Devices

Javad Eshraghi, Purdue University

Abstract

Cavitation, liquid slosh, and splashes are ubiquitous in science and engineering. However, these phenomena are not fully understood. Yet to date, we do not understand when or why sometimes the splash seals, and other times does not. Regarding cavitation, a high temporal resolution method is needed to characterize this phenomenon. The low temporal resolution of experimental data suggests a model-based analysis of this problem. However, high-fidelity models are not always available, and even for these models, the sensitivity of the model outputs to the initial input parameters makes this method less reliable since some initial inputs are not experimentally measurable. As for sloshing, the air-liquid interface area and hydrodynamic stress for the liquid slosh inside a confined accelerating cylinder have not been experimentally measured due to the challenges for direct measurement. This dissertation provides the first detailed analysis and physical explanations for the abovementioned phenomena. These have consequences for diverse applications such as biomedical, diving, sound propagation in oceans, ocean oxygenation, and energy harvesting. First, we developed an analytical model to describe the trajectory and dynamics of the splash curtain in the water entry of hydrophobic spheres and validated it with a series of experiments. We elucidated the dynamics of splash curtain and discovered the existence of a critical dimensionless number that predicts the occurrence of the surface seal. As for the cavitation modeling, we proposed a robust characterization tool based on a novel state observer-based data-assimilation technique to overcome the limitations in the existing methods. We fused time-resolved cavitation bubble diameter measurements with the governing model to yield enhanced Spatiotemporal prediction of the cavitation bubble dynamics in this new autonomous technique. We then employed the data assimilation modeling to investigate the dynamics of a single air bubble exposed to an acoustic pressure field induced by a cavitation bubble using a unique combination of theory and experiment. We elucidated the effects of acoustic source intensity, the distance from the acoustic source, and air bubble size on the air bubble final oscillation regime. We also used data assimilation modeling to quantify cavitation intensity in autoinjector medical devices to assess the impact of cavitation on therapeutic protein. Furthermore, a set of experiments by conducting simultaneous PIV and shadowgraphy were used to investigate the interfacial motion and hydrodynamic shear due to the acceleration/deceleration during the autoinjector insertion that might cause therapeutic protein aggregation.

Degree

Ph.D.

Advisors

Vlachos, Purdue University.

Subject Area

Energy|Acoustics|Fluid mechanics|Mathematics|Mechanics|Medicine|Optics

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