• Title/Summary/Keyword: 벽전단응력

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Computational Hemodynamics in the Intracranial Aneurysm Model (뇌동맥류 모델에 대한 혈류역학 해석)

  • Seo, Taewon;Byun, Jun Soo
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.37 no.10
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    • pp.927-932
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    • 2013
  • The intracranial aneurysm model is extracted based on the Computed Tomography (CT) scan images. Computational fluid dynamics simulations were conducted under both steady and realistic flow conditions in ANSYS-FLUENT. The minimum wall shear stress in the intracranial aneurysm tended to occur in the aneurysmal region. The magnitude of wall shear stress along inner wall of the curvature in the right M1 segment of middle cerebral artery is approximately 20 times higher than that along both the proximal and distal walls. However, the magnitudes of the wall shear stress at the aneurysm region were considerably low. The blood flow has the complex distribution in the aneurysmal region during the systolic period. Complex helical flow patterns are observed inside the aneurysm. Through an analysis of the hemodynamic characteristics, one may predict the rupture of the cerebral aneurysms.

Elastic Motion of the Blood Vessel and Wall Shear Stress in Carotid Artery with Stenosis (협착된 경동맥 내의 벽전단응력 및 혈관의 탄성적 거동)

  • Kim Chang Nyung;Oh Taek Yeol;Choi Myung Jin;Jung Sam Doo
    • Journal of the Korean Society for Precision Engineering
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    • v.22 no.9 s.174
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    • pp.179-187
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    • 2005
  • The characteristics of blood flow and the interaction between the blood vessel and blood flow play important roles in plaque cap rupture and the growth of atherosclerosis which may lead directly to a heart attack or a stroke. In this study, carotid arteries with different stenoses have been numerically simulated to investigate the wall shear stress(WSS) and the elastic motion of the vessel. Blood flow has been treated as physiological, laminar and incompressible flow. To model the shear thining behavior of the blood, the Carreau-Yasuda model has been employed but the viscoelasticity of blood has not been considered. The results show that the WSS of $severe(75\%)$ stenosis is much higher than those of $25\%\;and\;50\%$ stenosis in the region of stenosis. With the increase in the stenosis thickness, the expansion ratio of the center of the stenosis decreases while the expansion ratio of the upstream region of the stenosis increases.

Effect of Stent Design Porosity on Hemodynamics Within Cerebral Aneurysm Model: Numerical Analysis (스텐트 공극률의 뇌동맥류 모델 내부 유동장 영향 수치해석)

  • Phan, Dai Thanh;Lee, Sang-Wook
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.38 no.1
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    • pp.63-70
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    • 2014
  • In the present study, CFD simulations were conducted for investigating intra-aneurysmal flow characteristics with different stent porosities ($C_{\alpha}$ = 80%, 74%, and 64%), and the simulation results were compared with experimental data. Using a quadratic tetrahedral element-based finite element scheme, we estimated velocity fields and wall shear stress. The intra-aneurysmal velocity reduction ratios obtained via simulation agree well with published experimental data. It was found that a stent with a porosity of 80%, which is highest in the present study, is able to effectively reduce flow into the aneurysm, which causes intra-aneurysmal stasis, and that stents with lower porosities afford only incremental benefits in reducing inflow to an aneurysm.

Modeling of the Artery Tree in the Human Upper Extremity and Numerical Simulation of Blood Flow in the Artery Tree (상지동맥 혈관계의 모델링과 혈유동의 전산수치해석)

  • Kim, Keewon;Kim, Jaeuk U.;Beak, Hyun Man;Kim, Sung Kyun
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.40 no.4
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    • pp.221-226
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    • 2016
  • Since arterial disease in the upper extremity is less common than that in the lower extremity, experimental and numerical investigations related to upper extremity have been rarely performed. We created a three-dimensional model of the arteries, larger than approximately 1 mm, in a Korean adult's left hand (from brachial to digital arteries), from 3T magnetic resonance imaging (MRI) data. For the first time, a three-dimensional computational fluid dynamic method was employed to investigate blood flow velocity, blood pressure variation, and wall shear stress (WSS) on this complicated artery system. Investigations were done on physiological blood flows near the branches of radial and deep palmar arch arteries, and ulnar and superficial palmar arch arteries. The flow is assumed to be laminar and the fluid is assumed to be Newtonian, with density and viscosity properties of plasma.

Numerical Analysis on the Effect of Wall Shear Stress Around the Ring Drug-Eluting Stent (고리형 약물분출 스텐트 주위 벽전단응력의 영향에 대한 수치해석)

  • Seo, Tae-Won;Barakat, Abdul
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.31 no.1 s.256
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    • pp.21-28
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    • 2007
  • The use of drug-eluting stents has dramatically reduced the incidence of restenosis however, much remains to be teamed about the performance of these stouts. In the present study, we tested the hypothesis that the design of drug-eluting stents influences the efficacy of local drug delivery to the arterial wall and that this effect depends on both arterial geometry and the prevailing flow conditions. We performed computational simulations in which the coupled Navier-Stokes and advection-diffusion equations were solved to determine the flow field and drug concentration in the vicinity of model drug-eluting stouts It is found that the characteristics of flow phenomena can be influenced greatly by the ratio of stent diameter to vessel diameter. The presence of drug-eluting stent may have profound effect on wall shear stresses, recirculation sizes and drug distributions. The results show that recirculation zone is influenced by the imposed flow conditions and stent diameter. In pulsatile flow, the low wall shear stress and high drug concentration occur along the arterial wall during the decelerating flow conditions. These results could provide the guideline for future drug-eluting stent designs toward reducing restenosis by affecting local wall shear stress distributions associated with neointimal hyperplasia.

NUMERICAL STUDY ON THE BLOOD FLOW CHARACTERISTICS OF STENOSED AND BIFURCATED BLOOD VESSELS WITH A PHASE ANGLE CHANGE OF A PERIODIC ACCELERATION (주기 가속도 위상변화에 따른 협착 및 분지 혈관의 혈류 특성에 대한 수치해석적 연구)

  • Ro, K.C.;Cho, S.W.;Lee, S.H.;Ryou, H.S.
    • Journal of computational fluids engineering
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    • v.13 no.3
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    • pp.44-50
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    • 2008
  • The present study is carried out in order to investigate the effect of the periodic acceleration in the stenosed and bifurcated blood vessels. The blood flow and wall shear stress are changed under body movement or acceleration variation. Numerical studies are performed for various periodic acceleration phase angles, bifurcation angles and section area ratios of inlet and outlet. It is found that blood flow and wall shear stress are changed about ${\pm}20%$ and ${\pm}24%$ as acceleration phase angle variation with the same periodic frequency. also wall shear stress and blood flow rate are decreased as bifurcation angle increased.

A Numerical Analysis on the Hemodynamic Characteristics in Elastic Blood Vessel with Stenosis (협착이 있는 탄성혈관을 흐르는 혈액의 유동특성에 관한 수치해석적 연구)

  • 정삼두;김창녕
    • Journal of Biomedical Engineering Research
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    • v.23 no.4
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    • pp.281-286
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    • 2002
  • In this study, blood flow in a carotid artery supplying blood to the human's brain has been numerically simulated to find out how the blood flow affects the genesis and the growth of atherosclerosis and arterial thrombosis. Velocity Profiles and hemodynamic parameters have been investigated for the carotid arteries with three different stenoses under physiological flow condition. Blood has been treated as Newtonian and non-Newtonian fluid. To model the shear thinning properties of blood for non-Newtonian fluid, the Carreau-Yasuda model has been employed. The result shows that the wall shear stress(WSS) increases with the development of stenosis and that the wall shear stress in Newtonian fluid is highly evaluated compared with that in non-Newtonian Fluid. Oscillatory shear index has been employed to identify the time-averaged reattachment point and this point is located farther from the stenosis for Newtonian fluid than for non-Newtonian fluid The wall shear stress gradient(WSSG) along the wall has been estimated to be very high around the stenosis region when stenosis is developed much and the WSSG peak value of Newtonian fluid is higher than that of non-Newtonian fluid.

EFFEECTS OF NON-NEWTONIAN FLUID MODEL ON HEMODYNAMICS IN CEREBRAL SACCULAR ANEURYSMS (낭상 뇌동맥류 혈류유동에서 비뉴우토니안 유체 모델의 영향)

  • Park, J.S.;Lee, S.W.
    • Journal of computational fluids engineering
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    • v.16 no.2
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    • pp.81-87
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    • 2011
  • The importance of shear thinning non-Newtonian blood rheology on the hemodynamic characteristics of idealized cerebral saccular aneurysms were investigated by carrying out CFD simulations assuming two different non-Newtonian rheology models (Carreau and Ballyk models). To explore effects of vessel curvature, a straight and a curved vessel geometry were considered. The wall shear stress(WSS), relative residence time(RRT) and velocity distribution were compared at the different phases of cardiac cycle. As expected, blood entered the aneurysm at the distal neck and created large vortex in both aneurysms, but with higher momentum on the curved vessel. Hemodynamic characteristics such as WSS, and RRT exhibited only minor effects by choice of different rheological models although Ballyk model produced relatively higher effects. We conclude that the assumption of Newtonian fluid is reasonable for studies aimed at quantifying the hemodynamic characteristics, in particular, WSS-based parameters, considering the current accuracy level of medical image of cerebral aneurysm.

Numerical Study of Pulsatile Blood Flow in Stenotic Artery (협착 동맥에서의 맥동 혈류 유동에 대한 수치해석적 연구)

  • Seo, Tae-Won;Buriev, Bahtiyor
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.32 no.11
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    • pp.891-896
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    • 2008
  • In the present computational study, simple stenotic artery models using pulsatile flow condition were investigated. A 1 Hz non-reversing sinusoidal velocity for pulsatile flow was imposed at the flow inlet and the corresponding Womersley number based on the vessel radius is 2.75. The simple stenotic geometries have been used that consist of 25%, 50% and 75% semicircular constriction in a cylindrical tube. In this paper, numerical solutions are presented for a first harmonic oscillatory flow using commercial software ADINA 8.4. As stenosis and Reynolds number increase, the maximum wall shear stress(WSS) increases while the minimum WSS decreases. As the stenotic rate increases, the pressure drop at the throat severely decreases to collapse the artery and plaque. It is found that the fluid mechanical disturbances due to the constriction were highly sensitive with rate of stenosis and Reynolds number. When Reynolds number and stenosis increase, the larger recirculation region exists. In this recirculation region the possibility of plaque attachment is increasingly higher. The present results enhance our understanding of the hemodynamics of a stenotic artery.

Atherogenic Risk Stratification According to Changes in the Geometrical Shape of the Coronary Artery (관상동맥의 기하학적 형상변화에 따른 동맥경화 위험도)

  • Suh, Sang-Ho;Park, Jun-Gil;Roh, Hyung-Woon;Lee, Byung-Kwon;Kwon, Hyuck-Moon
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.34 no.10
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    • pp.893-899
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    • 2010
  • A previous study showed that hemodynamics is correlated with stenosis in the coronary artery. The flow characteristics and the distributions of the hemodynamic wall parameters in the coronary artery are investigated under physiological flow condition. The present study also aims to establish the mechanism of the generation of atherosclerosis by analyzing the hemodynamic variables in the coronary artery where atherosclerosis frequently occurs. The stenosis phenomena due to atherosclerosis are related to not only the biochemical reaction between blood and blood vessels but also the hemodynamic factors sush as flow separation and oscillatory wall shear stress. As the bifurcated angle increases, the size of the recirculation area that appears in the cross section increases and disturbed flow is observed in this area. We speculate that this area is the starting point of atherosclerosis in the coronary artery.