Publication Date

2021

Document Type

Dissertation/Thesis

First Advisor

Tan, Jifu

Degree Name

M.S. (Master of Science)

Legacy Department

Department of Mechanical Engineering

Abstract

Cardiovascular disease such as heart attack or stroke has been the leading cause of death in the US for over 100 years. Understanding the blood cell transport physics in a vascular network is important in both fundamental research and clinical practices. In this study, 3Dnumerical simulations on blood flow in a complex retina vascular network were performed considering deformable red blood cells (RBCs), white blood cells (WBCs), and obstructed vessels. The blood was modeled as a mixture of RBCs and WBCs suspended in fluid. The fluid was solved using the lattice Boltzmann method (LBM), and blood cells were modeled by coarse-grained molecular dynamics. The coupling between the fluid and cells was achieved through the immersed boundary method. Firstly, the impact of blockage on flow rate distribution (without any blood cells) was investigated. It showed that the blockage may change the flow rate significantly on distant vessels that are not directly connected with the blocked vessel. The flow rate in some vessels can increase up to 1200% due to an obstruction in the network. Cells in a vessel near a partial obstruction were found to oscillate, as the flow direction in the vessel changed multiple times. Next, the cell transport physics in the network were studied. It showed the fraction of cells in each daughter branch for a bifurcated region strongly depends on the cell incoming position and geometry of the bifurcation. Cell accumulation may occur in some bifurcation such a T shaped junction that may eventually lead to a physical blockage. The addition of WBCs impacts the local flowrate when they are squeezed through a capillary vessel, and the flow rate can be decreased up to 32% due to larger size of a WBC. Finally, to reduce the computational cost of the3D Multiphysics model, multiple non-Newtonian viscosity models were incorporated into a lumped parameter blood flow model. Compared with the 3D model, all lumped models can reproduce an accurate Hematocrit distribution in the vascular network. Among them the Fahræus-Lindqvist model was found to be the most accurate one. The work from the thesis can be used to build a multiscale model for blood flow where the macroscale flow will be solved by the lumped model and the microscale flow will be solved by the 3D Multiphysics model with heterogeneous cell suspensions.

Extent

54 pages

Language

eng

Publisher

Northern Illinois University

Rights Statement

In Copyright

Rights Statement 2

NIU theses are protected by copyright. They may be viewed from Huskie Commons for any purpose, but reproduction or distribution in any format is prohibited without the written permission of the authors.

Media Type

Text

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