Oxygen mass transfer in a model three-dimensional artery

Abstract

Arterial geometry is commonly non-planar and associated with swirling blood flow. In this study, we examine the effect of arterial three-dimensionality on the distribution of wall shear stress (WSS) and the mass transfer of oxygen from the blood to the vessel wall in a U-bend, by modelling the blood vessels as either cylindrical or helical conduits. The results show that under physiological flow conditions, three-dimensionality can reduce both the range and extent of low WSS regions and substantially increase oxygen flux through the walls. The Sherwood number and WSS distributions between the three-dimensional helical model and a human coronary artery show remarkable qualitative agreement, implying that coronary arteries may potentially be described with a relatively simple idealized three-dimensional model, characterized by a small number of well-defined geometric parameters. The flow pattern downstream of a planar bend results in separation of the Sh number and WSS effects, a finding that implies means of investigating them individually.

Computational modelling of the interaction of shock waves with multiple gas-filled bubbles in a liquid

“…Specifically, cells near the anastomosis had an average size of 3.6 × 10 −5 m, expanding progressively to 3.6 × 10 −4 m beyond a distance of ∼ 4 × 10 −2 m from the anastomosis. The prismatic boundary layers were 17 cells thick, with the first cell having a thickness of 5 × 10 −6 m (in line with the mesh resolution employed by Coppola and Caro 41 in a similar Reynolds/Schmidt number regime). Each mesh had ∼ 5 × 10 6 cells in total, and was found a posteriori to satisfy the resolution criteria set out by Valen-Sendstad 43 who performed direct numerical simulations of transitional flow in an aneurysm.…”

“…The imposition of zero boundary-normal oxygen concentration gradients at the DAO and DVO is a standard practice [38][39][40][41] and minimizes impact on the evolution of the oxygen boundary layer as it exits the domain. The imposition of a spatially constant oxygen concentration at the arterial wall assumes that the arterial wall acts as an oxygen sink, readily consuming excess oxygen, in line with the arguments of Tarbell.…”

Wall shear stress exposure time: a Lagrangian measure of near-wall stagnation and concentration in cardiovascular flows

“…The local transport of several substances near and at the vessel wall are known to influence atherosclerosis progression [56]. For example, previous studies have looked into transport of low density lipoproteins (LDL) [17,20,30,14], high density lipoproteins (HDL) [40,24], oxygen [16,27], nitric oxide (NO) [45,35], monocytes [12,14], and adenine triphosphate ATP and adenine diphosphate ADP [13,15,8] as important mass transport processes involved in atherosclerosis.Intravascular thrombosis is another compelling pathology associated with most cardiovascular diseases where near-wall transport becomes important [7,25]. The trajectories of individual platelets and the accumulation and residence time of chemical solutes including ADP, thrombin, and various blood factors control clot formation.…”

Mixing Through Stirring of Steady Flow in Small Amplitude Helical Tubes

“…This property helps to guarantee the geometry of the graft in vivo, and prevents extreme curvatures, due to a kink, that would more easily cause the flow to separate. Related to this, a recent study by Coppola and Caro (2008) that investigated a helical geometry formed on a curved centreline showed that even at Re = 600 the flow remained attached throughout the bend, so that even though the mixing behaviour may be altered, the additional curvature is unlikely to have a pathological effect.…”