A computational fluid dynamics (CFD) model is developed to simulate the flow and delivery of oxygen and other substances in a capillary network. A three-dimensional capillary network has been constructed to replicate the one studied by Secomb et al. (2000), and the computational framework features a non-Newtonian viscosity model of blood and the oxygen transport model including in-stream oxygen-hemoglobin dissociation and wall flux due to tissue absorption, as well as an ability to study delivery of drugs and other materials in the capillary streams. The model is first run to compute the volumetric flow rates from the velocity profiles in the segments and compared with Secomb’s work with good agreement. Effects of abnormal pressure and stenosis conditions, as well as those arising from different capillary configurations, on the flow and oxygen delivery are investigated, along with a brief look at the unsteady effects and drug dispersion in the capillary network. The current approach allows for inclusion of oxygen and other material transports, including drugs, nutrients, or contaminants based on the flow simulations. Also, three-dimensional models of complex circulatory systems ranging in scale from macro- to microvascular vessels, in principle, can be constructed and analyzed in detail using the current method. 1. Introduction The capillary vessels, among other functions, transport oxygen, carbon dioxide, and other materials (nutrients and drugs) to and from cells. These smaller blood vessels in the body (the arterioles, venules, and capillaries) make up the so-called microcirculatory system. Larger blood vessels, that is, arteries and veins with inner diameters greater than approximately 100？μm, are termed “macrovascular.” The two systems have distinguishing characteristics. The macrovascular vessels serve as reservoirs of pressure on the high and low side of the cardiovascular system, as well as a passage for relatively large flow rates of blood between the heart and peripheral organs. The microcirculatory vessels are responsible for regulating flow and also for direct material transport at the cell levels. The transport may involve oxygen, carbon dioxide, nutrients, and other biochemical species. About 80% of the total pressure drop in the circulatory system occurs in these microcirculation networks, as the vessel diameters are small and lengths quite large in total [1]. The microcirculation system inherently includes complex flow patterns such as bifurcations in forward and backward directions, constrictions, and flow turns. It is of both academic
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