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Rheology of red blood cell flow in large geometries
KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.ORCID iD: 0000-0001-9976-8316
KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.ORCID iD: 0000-0003-2830-0454
KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
2013 (English)Conference paper, Published paper (Refereed)
Abstract [en]

When studying disease development in arteries, it is important to understand the local variations in blood rheology. Blood flow in large arteries is often assumed to behave as a homogeneous fluid, an assumption that is not entirely correct. The local viscosity changes with the local concentration of Red Blood Cells (RBCs) and the rate of shear strongly influences the Wall Shear Stress (WSS) and its gradients, physiological parameters important in the study of atherosclerosis. Moreover, the flow behavior of RBCs is influenced by the geometric structure of the flow environment. In experiment, rheological properties across a tube cross-section are difficult to measure if non-invasive techniques are to be used. Therefore, rheometric devices are constructed of simple geometries to measure the bulk rheology. In this study, the Lattice Boltzmann Method is used to model the blood as a particle suspension of RBCs. The RBC Volume Fractions (VF) investigated corresponds to 1, 2 and 5%, and both a channel and a tube flow are considered. The results display large differences in RBC distributions and velocity profiles. Estimated from existing viscosity models, the viscosity distributions are found to display variations of up to 5% when comparing the two geometries. This is of importance since errors in quantifying the viscosity can lead to miscalculations of the physiological variables.

Place, publisher, year, edition, pages
2013.
National Category
Fluid Mechanics and Acoustics
Identifiers
URN: urn:nbn:se:kth:diva-136607OAI: oai:DiVA.org:kth-136607DiVA: diva2:676631
Conference
8th International Conference on Multiphase Flow (ICMF), Jeju, Korea (2013)
Note

QC 20131206

Available from: 2013-12-06 Created: 2013-12-06 Last updated: 2013-12-06Bibliographically approved
In thesis
1. Blood Flow variations in Large Arteries due to non-Newtonian rheology
Open this publication in new window or tab >>Blood Flow variations in Large Arteries due to non-Newtonian rheology
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The blood is a complex fluid that contains, in addition to water, cells, macro-molecules and a large number of smaller molecules. The physical properties of the blood are therefore the result of non-linear interactions of its constituents, which are influenced by the local flow field conditions. Hence, the local blood viscosity is a function of the local concentration of the blood constituents and the local flow field itself. This study considers the flow of blood-like fluids in generalised 90-degree bifurcating pipes and patient-specific arterial bifurcations relevant to the large aortic branches in humans. It is shown that the Red Blood Cell (RBC) distribution in the region of bifurcations may lead to large changes in the viscosity, with implications on the concentrations of the various cells in the blood plasma. This in turn implies that the flow in the near wall regions is more difficult to estimate and predict than that under the assumption of a homogeneous fluid. The rheological properties of blood are complex and are difficult to measure, since the results depend on the measuring equipment and the inherent flow conditions. We attempt to model the viscosity of water containing different volume fractions of non-deforming RBC-like particles in tubes. The apparent viscosities of the mixtures obtained from these model experiments have been compared to the predictions of the different rheological models found in the literature. The same rheological models have also been used in the different simulations, where the local RBC concentration and local shear rate are used in the viscosity models. The flow simulations account for the non-linearity due to coupling between the flow and fluid rheology. Furthermore, from a physiological perspective, it is shown that oscillatory wall shear stresses are affected by changes in RBC concentration in the regions of the bifurcation associated with atherogenesis. The intrinsic shear thinning rheological property of the blood, in conjunction with stagnation in separated flows, may be responsible for elevated temporal wall shear stress gradients (TWSSG) influencing endothelial cell behaviour, which has been postulated to play a role in the development of atherosclerosis. The blood-like fluid properties along with variations in the RBC concentration could also lead to variations in the developing flow structures in the larger arteries that could influence the work the heart has to bear.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2013. xx, 98 p.
Series
Trita-MEK, ISSN 0348-467X ; 2013:18
Keyword
Blood, Rheology, Viscosity, non-Newtonian, CFD, Bifurcations, Unsteadiness, Wall Shear Stress, Atherosclerosis
National Category
Other Engineering and Technologies
Identifiers
urn:nbn:se:kth:diva-136594 (URN)978-91-7501-952-9 (ISBN)
Public defence
2013-12-19, Sal F3, Lindstedtsvägen 26, KTH, Stockholm, 10:15 (English)
Opponent
Supervisors
Note

QC 20131206

Available from: 2013-12-06 Created: 2013-12-06 Last updated: 2013-12-06Bibliographically approved

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Prahl Wittberg, LisaDo-Quang, Minh

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