• Korea-Australia Rheology Journal
• /
• 제19권2호
• /
• pp.89-95
• /
• 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.

• 대한의용생체공학회:학술대회논문집
• /
• 대한의용생체공학회 1995년도 춘계학술대회
• /
• pp.113-116
• /
• 1995

Steady and physiological flows of a Newtonian fluid and blood in the bifurcated arterial vessel are numerically simulated. Distributions of velocity, pressure and wall shear stress in the bifurcated arterial vessel are calculated to investigate the differences between steady and physiological flows. For the given Reynolds number physiological flow characteristics of a Newtonian fluid and blood in the bifurcated arterial vessel are quite different from those of steady flows. No flow separation or flow reversal in the bifurcated region in the downstream after stenosis appears during the acceleration phase. Also, no recirculation region is seen for steady flows. However, during the deceleration phase the flow began to exhibit flow reversal, which is eventually extended to the entire wall region.

• 한국가시화정보학회지
• /
• 제20권1호
• /
• pp.52-63
• /
• 2022

Direct numerical simulation of blood flow in a stenosed, patient-specific carotid artery was conducted to explore the transient behavior of blood flow with special emphasis on the wall-shear stress distribution over the transition region. We assumed the blood as an incompressible Newtonian fluid, and the vessel was treated as a solid wall. The pulsatile boundary condition was applied at the inlet of the carotid. The Reynolds number is 884 based on the inlet diameter, and the maximum flow rate and the corresponding Womersley number is approximately 5.9. We found the transitional behavior during the acceleration and deceleration phases. In order to quantitatively examine the wall-shear stress distribution over the transition region, the probability density function of the wall-shear stress was computed. It showed that the negative wall-shear stress events frequently occur near peak systole. In addition, the oscillatory shear stress index was used to further analyze the relationship with the negative wall-shear stress appearing in the systolic phase.

• 대한치과의사협회지
• /
• 제19권4호통권143호
• /
• pp.347-352
• /
• 1981

This experiment was performed to estimate the changes on blood flow of the oral structures in hemorrhagic shock. Rabbits were anesthetized by intravenous injection of nembutal(30mg/kg). The Femoral artery was exposed and cannulated with polyethylene tubing filled with heparinized saline. Hypovolemic shock was induced by collecting the bloos of which amount was equaled as 2 % of body weight through arterial cannula for about 30 minutes. During hemorrhage, arterial blood pressure was recorded on recorder. In hypovolemic shock, arterial blood pressure decreased from 116.2±4.1 mmHg to 62.6±4.0 mmHg. Distribution of blood flow in oral tissues decreased to 30-50 % of control group. But blood flow of the masseter muscle was increased and the mandibular angle was not changed.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2006년도 춘계학술대회논문집
• /
• pp.959-963
• /
• 2006

A three-dimensional elastic blood vessel model with internal diameter variation is considered to investigate internal flow characteristics and effects of structural deformation. Also, computational analyses for both the rigid model and the fully-coupled FSI model have been conducted in order to compare the shear stress, pressure distribution, and flow velocity in detail. A 70% narrowing area of asymmetric blood vessel model was especially investigated to show the versatility of fluid-structure interaction phenomenon. The results reveal that effect of fluid-structure interaction is very important to accurately investigate the flow characteristics of the blood vessel.

• 대한기계학회논문집B
• /
• 제20권11호
• /
• pp.3607-3619
• /
• 1996

Experimental and numerical studies for three-dimensional pulsatile flows are conducted to investigate the flow characteristics in the bifurcated tubes. Velocity measurements in experimental study were made by both Pulsed Doppler Ultrasound(PDU) machine and Laser Doppler Anemometer(LDA) system. Glycerin is used for experimental study. Experimental results are used to verify the results of the numerical simulation. Flow characteristics of Newtonian fluid and blood in the bifurcated tubes under the steady and pulsatlie flows are numerically investigated. Finite volume method is employed for three-dimensional numerical simulations. Blood is considered as a non-Newtonian fluid and the constitutive equation of blood is used for the numerical analysis. Numerical analyses are focused on the flow patterns for various branch angles ranging from 30.deg. to 90.deg. and diameter ratios such as 1.0, 0.8, and 0.6. Pulsatile flow characteristics of blood are compared with those of Newtonian fluid. Parameter effects on axial velocity, pressure and wall shear stress distribution along the bifurcated tubes are discussed in terms of the branch angle, diameter ratio, and Reynolds number.

• Journal of applied mathematics & informatics
• /
• 제9권2호
• /
• pp.731-744
• /
• 2002

The temperature distribution in human skin and subdermal tissue layer is presented using bioheat transfer equation. The body temperature is determined by the balance between heat produced and heat lost by our body. The time-dependent solutions have been found to be affected by the metabolic heat generation rate, blood mass flow, the rate of evaporation of perspiration and also by the atmospheric temperature. The analytic solutions for different layers have been calculated numerically and are also shown graphically.

• Journal of Advanced Marine Engineering and Technology
• /
• 제37권2호
• /
• pp.149-155
• /
• 2013

혈류 유동 연구를 위해서는 심장의 맥동 유동을 만들어 내는 것이 중요하다. 본 연구에서는 동맥혈류의 유동 해석을 위해 새롭게 설계된 심장 박동 모사 맥동펌프의 제작 및 그 성능에 관하여 시험을 수행하였다. 피스톤 펌프를 이용한 기본몸체 설계를 수행하였고 직류모터와 엔코더를 사용하여 회전수와 가속비를 설정할 수 있도록 하였으며, 시험결과는 전 영역에서 맥동 유동의 분포를 잘 따르고, 반복되는 맥동 주기의 편차도 작게 나타남을 확인하였다.

• Asian-Australasian Journal of Animal Sciences
• /
• 제12권6호
• /
• pp.886-890
• /
• 1999

From previous studies, there is a strong possibility in buffaloes that the marked increase in blood volume (BV) under hot conditions contributes to heat transportation from the rectum to the skin. The present study was done to clarify changes with environmental temperature on water-shift between blood and extracellular fluid (ECF), heat distribution between the rectum and the skin, and blood flow rates (BFR) at the hind legs (reflecting the skin surface). Four buffaloes and four Friesian cows were successively exposed to three different temperatures of $20^{\circ}C$, $30^{\circ}C$ and $35^{\circ}C$. BV and ECF volume were measured with Evans' blue and sodium-thiocyanate dilution methods, respectively. Rectal and subcutaneous (as the skin) temperatures were measured by copper-constantan thermocouples. BFR were measured by a supersonic blood flow meter. With an increase in environmental temperature, skin temperature in buffaloes increased significantly than cows, but rectal temperature was not significantly different between two species. BV, especially plasma compartment, increased significantly in only buffaloes, while ECF volume did not change in both species. BFR increased significantly in buffaloes, but not in cows. From these results, the increased of BV may be caused by water flowing from ECF compartment. The water-shift may induce the increase of BFR and skin temperature. It is suggested in the present study that internal changes of blood compartment in buffaloes contribute to transfer of heat to the skin surface.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2008년도 추계학술대회A
• /
• pp.1647-1650
• /
• 2008

The moyamoya disease is a type of cerebrovascular disease which produces thin abnormal blood vessels like haze in the brain base because the end of internal carotid artery which supplies about 80% of blood is blocked. Regarding this moyamoya disease, the shearing stress and thrombus generation are mentioned as its main causes. This study three-dimensionally implemented the ICA, ACA, and MCA parts of the cerebrovascular configuration related to the moyamoya disease, and analyzed the hydrodynamic phenomenon with the commercial program ADINA. In particular, the correlations between shearing stress and speed distribution according to the branch angle of ACA and MCA. A numerical analysis found that the greater the branch angle of ACA and MCA, the lower the shearing stress and the greater the stationary area of the flow.. Put Abstract text here.