Theses and Dissertations from UMD
Permanent URI for this communityhttp://hdl.handle.net/1903/2
New submissions to the thesis/dissertation collections are added automatically as they are received from the Graduate School. Currently, the Graduate School deposits all theses and dissertations from a given semester after the official graduation date. This means that there may be up to a 4 month delay in the appearance of a give thesis/dissertation in DRUM
More information is available at Theses and Dissertations at University of Maryland Libraries.
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Item Flow and interfacial dynamics in vascular vessels and microfluidics(2007-01-19) Wang, Yechun; Dimitrakopoulos, Panagiotis; Chemical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This dissertation investigates the hemodynamic forces on biological cells adherent on vascular vessels as well as the interfacial dynamics of droplet motion in microfluidic channels. In addition, we develop a novel three-dimensional spectral boundary element algorithm for interfacial dynamics in Stokes flow. In physiological systems, the hemodynamic forces exerted on endothelial cells in vascular vessels affect the behavior of the cells via mechano-transduction. The hemodynamic forces also play a pivotal role in the adhesion of leukocytes onto the surface of blood vessels. This study investigates the relative importance and the nature of the two components of the hemodynamic force, i.e., the shear and normal force, on the cell and its vicinity. Based on computational investigation and scaling analysis, the study demonstrates that the normal force contributes significantly to the total hemodynamic force on the cell. This study points out the importance of the normal force exerted on biological cells attached to blood vessels which has been overlooked. This research may motivate experiments to identify the effects of the normal force on the functions of biological cells adhered in blood vessels. The results of the study are also applicable to the fluid forces over protuberances in microfluidic devices and porous media. For the efficient study of droplet dynamics, we have developed a novel three-dimensional high-order/high-accuracy spectral boundary element algorithm for interfacial dynamics in Stokes flow. This methodology has been employed to several interfacial problems and the results are in excellent agreement with experimental findings, analytical predictions and previous numerical computations. We also investigate the droplet motion in confined geometries which is primarily motivated by the recent development of microfluidic devices and has applications in the enhanced oil recovery, lubrication and coating processes. We consider the buoyancy-driven droplet motion along a solid wall and the pressure-driven droplet motion in a micro-channel. The influence of capillary number, Bond number and viscosity ratio on the droplet motion and deformation is investigated.Item Numerical Studies of Stokes Flow in Confined Geometries(2004-12-03) Wang, Yechun; Dimitrakopoulos, Panagiotis; Chemical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The current thesis includes two distinct projects. The first study involves the development of a novel three-dimensional Spectral Boundary Element algorithm for interfacial dynamics in Stokes flow. Our algorithm is the only available high-order/high-accuracy methodology for the problem of droplet deformation in viscous flows. By applying this algorithm to several interfacial problems, we find that our results are in excellent agreement with experimental findings, analytical predictions and previous numerical computations. The second project studies viscous flows over a protuberance on the inner wall of a solid microtube, a problem relevant to both physiological systems and microfluidic devices. The shear stress, drag and torque on the protuberance are determined as functions of the spreading angle and the relative size of the protuberance which may represent leukocytes, blood clots or endothelial cells on the microvessel wall. This study facilitates the understanding of mechano-transduction phenomena as well as cell adhesion in blood flow.