UC San Diego

Understanding physiological flows is essential to the advancement of medical science. This dissertation investigates two physiologically relevant flow problems and their applications through a combination of theoretical modeling and experimental analysis. The first investigation concerns cerebrospinal-fluid flow in the central nervous system, with particular emphasis on the in vitro experimental characterization of the slow fluid-particle drift induced by cardiac-driven motion in the spinal canal. The study shows that Time-Spatial Labeling Inversion Pulse (Time-SLIP), a non-contrast MRI technique, can be used to measure mean Lagrangian drift in a simplified phantom. It also identifies potential limitations associated with signal quality, spatial resolution, and post-processing methodology, which may complicate future clinical applications of the method. The second topic concerns blood flow in the main pulmonary artery. This problem is first addressed through the development of an in vitro experimental platform that applies pressure and shear stress simultaneously to endothelial cells. The results demonstrate a working platform capable of accurately reproducing flow-induced mechanical loads over a sufficient endothelial cell population for qRNA sequencing. Complementing this experimental work, the dissertation also presents a theoretical and experimental analysis of Poiseuille flow over a stretching bottom boundary, providing the foundation for a future device capable of reproducing the full range of flow-induced mechanical loads acting on endothelial cells, including shear stress, pressure, and stretching. Experimental observations further show qualitative agreement with the theoretical predictions, supporting the use of this analysis in the development of a future device.