• Korea-Australia Rheology Journal
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• v.20 no.4
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• pp.197-211
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• 2008

The purpose of this study is mainly directed towards present of viewpoints on critical and commentary analysis on blood rheology, blood viscosity models, and physiological flow conditions. Understanding these basics is fundamental to meet the need for a sufficient and reliable CFD model of blood. Most of the used viscosity models on this manner have determined from parameter fitting on experimental viscosity data. Availability of experimental data from literature to define viscosity models of CFD analysis should be accurately chosen and treated in order to avoid any errors. Several basic gaps that limit the CFD model results are identified and given opportunities for future research.

• Korea-Australia Rheology Journal
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• v.21 no.3
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• pp.161-173
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• 2009

This study analyzes especially drag and lift models recently developed for fluid-solid, fluid-fluid or liquid-liquid two-phase flows to understand their applicability on the computational fluid dynamics, CFD modeling of pulsatile blood flow. Virtual mass effect and the effect of red blood cells, RBCs aggregation on CFD modeling of blood flow are also shortly reviewed to recognize future tendencies in this field. Recent studies on two-phase flows are found as very useful to develop more powerful drag-lift models that reflect the effects of blood cell's shape, deformation, concentration, and aggregation.

• Korea-Australia Rheology Journal
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• v.14 no.2
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• pp.77-86
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• 2002

A microscopic theoretical study is performed to predict the rheological properties of human blood in the low concentration limit. The shear thinning behavior of blood in the low shear limit is studied by considering the aggregate formation of red blood cells, which is called the rouleaux formation. Then the constitutive equations of blood in the high shear limit are derived for various flow situations by considering the unique features of deformation of blood cells. Specifically, the effects of the surface-area-preserving constraint and the lank-treading motion of blood cells on the rheological properties are studied.

• 한국전산유체공학회:학술대회논문집
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• 2010.05a
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• pp.224-227
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• 2010

In the present study, the characteristics of blood flow inside a carotid artery numerically investigated with shear rate specific blood viscosity. To simulate the blood flow with a patient-specific arterial geometry, the geometry of a carotid artery was constructed from 2D rain MRA data. The measured data of blood flow velocity at the common carotid artery were used as boundary conditions of the simulation. For the blood rheology data to be used in the simulation, the patient specific blood viscosity over the whole ranges of shear rate was obtained using $BioVisco^{TM}$. From the numerical results of the blood flow in the carotid artery, the increase of blood viscosity and the decrease of wall shear stress could be found in the carotid bifurcated region, more specifically at the post-plaque dilated region. These characteristics of blood viscosity and wall shear stress can be used more precisely and efficiently to predict the region vulnerable to plaque growht or thrombosis on top of the plaque.

• Korea-Australia Rheology Journal
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• v.16 no.2
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• pp.85-90
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• 2004

The present study investigated the deformability of red blood cells (RBC) and its effect on whole blood viscosity using a laser-diffraction slit-rheometer (LDSR). The LDSR has been recently developed with significant advances in laser-diffractometry design, operation and data analysis. While shear stress levels in a slit flow are continuously decreasing, both the deformation of red blood cells and the shear stress were simultaneously measured. Additionally, the viscosity of whole blood was measured using the LDSR. The present study found that the whole blood viscosity is strongly dependent on the RBC deformability. The less deformable the RBCs are, the higher the blood viscosity is.

• Korea-Australia Rheology Journal
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• v.19 no.2
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• pp.89-95
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• 2007

The flow characteristics of chicken blood in a micro-tube with a $100{\mu}m$ diameter are investigated using a micro-Particle Image Velocimetry (PIV) technique. Chicken blood with 40% hematocrit is supplied into the micro-tube using a syringe pump. For comparison, the same experiments are repeated for human blood with 40% hematocrit. Chicken blood flow has a cell-free layer near the tube wall, and this layer's thickness increases with the increased flow speed due to radial migration. As a hemorheological feature, the aggregation index of chicken blood is about 50% less than that of human blood. Therefore, the non-Newtonian fluid features of chicken blood are not very remarkable compared with those of human blood. As the flow rate increases, the blunt velocity profile in the central region of the micro-tube sharpens, and the parabolicshaped shear stress distribution becomes to have a linear profile. The viscosity of both blood samples in a low shear rate condition is overestimated, while the viscosity in a high shear rate range is underestimated due to radial migration and the presence of a cell-depleted layer.

• Korea-Australia Rheology Journal
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• v.21 no.1
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• pp.39-46
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• 2009

Atherosclerosis is a disease that narrows, thickens, hardens, and restructures a blood vessel due to substantial plaque deposit. The geometric models of the considered stenotic blood flow are three different types of constriction of cross-sectional area of blood vessel; 25%, 50%, and 75% of constriction. The computational model with the fluid-structure interaction is introduced to investigate the wall shear stresses, blood flow field and recirculation zone in the stenotic vessels. The velocity profile in a compliant stenotic artery with various constrictions is subjected to prescribed physiologic waveform. The computational simulations were performed, in which the physiological flow through a compliant axisymmetric stenotic blood vessel was solved using commercial software ADINA 8.4 developed by finite element method. We demonstrated comparisons of the wall shear stress with or without the fluid-structure interaction and their velocity profiles under the physiological flow condition in the compliant stenotic artery. The present results enhance our understanding of the hemodynamic characteristics in a compliant stenotic artery.

• Korea-Australia Rheology Journal
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• v.20 no.4
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• pp.189-196
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• 2008

The pulsatile flow of blood through a stenosed artery under the influence of external periodic body acceleration is studied. The effect of non-Newtonian nature of blood in small blood vessels has been taken into account by modeling blood as a Casson fluid. The non-linear coupled equations governing the flow are solved using perturbation analysis assuming that the Womersley frequency parameter is small which is valid for physiological situations in small blood vessels. The effect of pulsatility, stenosis, body acceleration, yield stress of the fluid and pressure gradient on the yield plane locations, velocity distribution, flow rate, shear stress and frictional resistance are investigated. It is noticed that the effect of yield stress and stenosis is to reduce flow rate and increase flow resistance. The impact of body acceleration is to enhance the flow rate and reduces resistance to flow.

• Korea-Australia Rheology Journal
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• v.21 no.2
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• pp.119-126
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• 2009

A numerical analysis is performed to investigate the effect of rotation on the blood flow characteristics with four different angular velocities. The artery has a cylindrical shape with 50% stenosis rate symmetrically distributed at the middle. Blood flow is considered a non-Newtonian fluid. Using the Carreau model, we apply the pulsatile velocity profile at the inlet boundary. The period of the heart beat is one second. In comparison with no-rotation case, the flow recirculation zone (FRZ) contracts and its duration is reduced in axially rotating artery. Also wall shear stress is larger after the FRZ disappears. Although the geometry of artery is axisymmetry, the spiral wave and asymmetric flow occur clearly at the small rotation rate. It is caused that the flow is influenced by the effects of the rotation and the stenosis at same time.

• Proceedings of the Korean Society of Rheology Conference
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• 2006.06a
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• pp.115-118
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• 2006