UVM Theses and Dissertations
Format:
Print
Author:
McGarry, Matthew T.
Dept./Program:
Mechanical Engineering
Year:
2004
Degree:
Ph. D.
Abstract:
The human bodies process of arresting bleeding from a punctured artery or vein is known as hemostasis(clotting). When an artery or vein is injured, blood rapidly exits the puncture site. This high outflow results in elevated values of the shear stress at the puncture site. These elevated shear stresses leave collagen and tissue factor exposed, which facilitate platelet deposition. In fact, researchers have shown that platelet deposition is a function of the strain rate along the vessel wall. As a result it is now recognized that fluid mechanics plays as much of a factor in the formation of the blood clots as biochemical factors. This new view of the importance of the fluid dynamics in hemostasis has created a need for models that examine the local fluid dynamics in the vicinity of vessel punctures as means for understanding the clotting process. Owing to the unique flow properties in the arterial and venous sides of the circulatory system, the bleeding dynamics in these regions are vastly different. Three models are presented to simulate bleeding from a punctured vessel in three different regions of the circulatory system. The first model seeks to examine the bleeding dynamics for large and medium sized arteries where significant flow pulsations exist with high internal pressures. The second model simulates bleeding in small arteries where steady flow exists with high internal pressures. The final model will examine the behavior of veins where steady flow occurs with low internal pressures. These three models quantify the leakage rate and strain rate as a function of key hydrodynamic and geometric parameters. The first two models demonstrate that bleeding exhibits a jet like behavior, while the last model, veins, shows the formation of droplets over the puncture site. Due to droplet formation and the vastly different droplet growth mechanisms in microgravity, the vein model will be examined in a reduced gravity environment to examine the possible effects on clotting responses.