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점탄성 유체의 난류 해석을 위한 수정된 k-ε 난류모델 개발 및 혈류역학에의 적용
노경철(K.C. Ro),유홍선(H.S. Ryou) 한국전산유체공학회 2010 한국전산유체공학회지 Vol.15 No.4
This article describes the numerical investigation of turbulent blood flow in the stenosed artery bifurcation under periodic acceleration of the human body. Numerical analyses for turbulent blood flow were performed with different magnitude of periodic accelerations using a modified turbulence model which was considering drag reduction of non-Newtonian fluid. The blood was considered to be a non-Newtonian fluid which was based on the power-law viscosity. In order to validate the modified k-ε model, numerical simulations were compared with the standard k-ε model and the Malin's low Reynolds number turbulence model for power-law fluid. As results, the modified k-ε model represents intermediate characteristics between laminar and standard k-ε model, and the modified k-ε model showed good agreements with Malin's verified power law model. Moreover, the computing time and computer resource of the modified k-ε model were reduced about one third than low Reynolds number model including Malin's model.
점탄성 유체의 난류 해석을 위한 수정된 k-ε 난류모델 개발 및 혈류역학에의 적용
노경철(K.C. Ro),유홍선(H.S. Ryou) 한국전산유체공학회 2010 한국전산유체공학회 학술대회논문집 Vol.2010 No.5
This article described that a high Reynolds number version of a turbulence model was modified by using drag reduction to analyze the turbulent flows of non-Newtonian fluid with visco-elastic viscosity and it was applied hemodynamics which was representative of visco-elastic fluid. The turbulence characteristics of visco-elastic fluid was expanded viscous sublayer region and buffer layer region by drag reduction phenomenon, and also Newtonian turbulence models does not predict because viscosity was related with shear rate of fluid flow. Hence, numerical simulation using a modified turbulence model was conducted under the same conditions that were applied to obtain the experiment results and previous turbulence models and then the numerical investigation of turbulent blood flow in the stenosed artery bifurcation under periodic acceleration of the human body.
주기 가속도 위상변화에 따른 협착 및 분지 혈관의 혈류 특성에 대한 수치해석적 연구
노경철(K.C. Ro),조성욱(S.W. Cho),이성혁(S.H. Lee),유홍선(H.S. Ryou) 한국전산유체공학회 2008 한국전산유체공학회지 Vol.13 No.3
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 ±20 % and ±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.
호흡량에 따른 사람의 기도 내 유동 특성에 관한 수치 해석적 연구
성건혁(K.H. Sung),노경철(K.C. Ro),유홍선(H.S. Ryou) 한국전산유체공학회 2012 한국전산유체공학회 학술대회논문집 Vol.2012 No.5
The inspiratory rate of a human is changed with the amount of the workload. The flow field is affected by the inspiratory flow rate. In the flow filed, the wall shear stress is important to predict the inflammation or a injury in airway wall. In addition, the turbulence intensity and secondary flow affect the deposition pattern of particle which is important for the drug-aerosol targeting. Thus the analysis of the flow characteristic in a human airway is important. The purpose of this study is to investigate the effects of the inspiratory flow rate on the flow characteristics in a human airway. The tubular airway is consistent with the oral cavity, pharynx, larynx and trachea. The constant inspiratory flow rate is used at each case of human states regarding the workload. By the effect of geometric airway changes, transition to turbulent airflow after the larynx can occur with relaminarization further downstream. Consequently, the low Reynolds number k-ω turbulence model is used for analysis with flow regime. As the inspiratory flow rate is larger, the wall shear stress and the turbulence intensity increase in airway. On the other hand, the area of recirculation zone is smaller.
전방순환동맥류 발생 위치에 대한 혈류량 및 분지각의 영향 및 동맥류 발생 전후의 유동 변화에 관한 수치해석 연구
김소윤(S.Y. Kim),노경철(K.C. Ro),유홍선(H.S. Ryou) 한국전산유체공학회 2011 한국전산유체공학회지 Vol.16 No.4
Cerebral aneurysm mostly occurs at a bifurcation of the circle of Willis. When the cerebral aneurysm is ruptured, a disease like subarachnoid hemorrhage and stroke is caused and this can be even deadly for patients. Generally it is known that causes of the intracranial aneurysm are a congenital deformity of the artery and pressure or shear stress from the blood flow. A blood flow pattern and the geometry of the blood vessel are important factors for the aneurysm formation. Research for several hemodynamic indices has been performed and these indices can be used for the prediction of aneurysm initiation and rupture. Therefore, the numerical analysis was performed for hemodynamic characteristics of the blood flow through the cerebral artery applying the various bifurcation angle and flow rate ratio. We analyze the flow characteristics using indices from the results of the numerical simulation. In addition, to investigate the flow pattern in the aneurysm according to the bifurcation angle and the flow rate ratio, we performed the numerical simulation on the supposition that the aneurysm occurs.
인조혈관 동정맥루의 혈액 투석량에 따른 인조혈관 내부 유동 특성에 관한 수치해석 연구
김재열(J.Y. Kim),노경철(K.C. Ro),유홍선(H.S. Ryou) 한국전산유체공학회 2011 한국전산유체공학회지 Vol.16 No.4
Hemodialysis is essential for patients with end stage renal failure. It is important to improve the patency rate and to minimize occurrence of the stenosis. Also, the blood flow to the artificial kidney can affect the blood flow characteristics through arteriovenous graft. Thus, the delivered dose are important factors for analyzing hemodynamic characteristics during hemodialysis access. In this study, the numerical analysis was performed for the effect of the delivered dose during hemodialysis access on the blood flow through the graft. As a result, The adverse pressure gradient occurred in case of a larger delivered dose through a catheter than standard dose and the flow instability increased. Also the circulation flow appeared largely at anastomotic site of the vein when the delivered dose was exceeded about half blood flow of inlet blood flow.
충돌분무와 액막의 열전달 해석모델을 고려한 범용 열/유체 프로그램 NUFLEX의 개발
김현정(H.J. Kim),노경철(K.C. Ro),유홍선(H.S. Ryou),허남건(N. Hur) 한국전산유체공학회 2008 한국전산유체공학회지 Vol.13 No.2
NUFLEX is a general purpose thermo/fluid flow analysis program which has various physical models including spray. In NUFLEX, spray models are composed of breakup and collision models of droplet. However, in case of diesel engine, interaction between wall-film and impingement model considering heat transfer is not coded in NUFLEX. In this study, Lee & Ryou impingement & wall-film model considering heat transfer is applied to NUFLEX For the verification of this NUFLEX program, numerical results are compared with experimental data. Differences of film thickness and radius between numerical results and experimental data are within 10% error range. The results show that NUFLEX can be used for comprehensive analysis of spray phenomena.
혈액 투석 시 주사침에서의 투석량에 따른 인조혈관 내부 유동 특성에 관한 수치해석 연구
김재열(J.Y. Kim),노경철(K.C. Ro),유홍선(H.S. Ryou) 한국전산유체공학회 2011 한국전산유체공학회 학술대회논문집 Vol.2011 No.5
Hemodialysis is essential for patients with end stage renal failure. It is important to improve the patency rate and to minimize occurrence of the stenosis. Also, the blood flow to the artificial kidney can affect the blood flow characteristics though arteriovenous graft. Thus, the delivered dose are important factors for analyzing hemodynamic characteristics during hemodialysis access. In this study, the numerical analysis was performed for the effect of the delivered dose during hemodialysis access on the blood flow through the graft. As a result, The adverse pressure gradient occurred in case of a larger delivered dose through a catheter than standard dose and the flow instability increased. Also the circulation flow appeared largely at anastomotic site of the vein when the delivered dose was exceeded about half blood flow of inlet blood flow.
전방순환동맥류 발생 위치에 대한 혈류량 및 분지각의 영향 및 동맥류 발생 전후의 유동 변화에 관한 수치해석 연구
김소윤(S.Y. Kim),노경철(K.C. Ro),유홍선(H.S. Ryou) 한국전산유체공학회 2011 한국전산유체공학회 학술대회논문집 Vol.2011 No.5
Cerebral aneurysm mostly occurs at a bifurcation of the circle of Willis. When the cerebral aneurysm is ruptured, a disease like subarachnoid hemorrhage and stroke is caused and this can be even deadly for patients. Generally it is known that causes of the intracranial aneurysm are a congenital deformity of the artery and pressure or shear stress from the blood flow. A blood flow pattern and the geometry of the blood vessel are important factors for the aneurysm formation. Research for several hemodynamic indices has been performed and these indices can be used for the prediction of aneurysm initiation and rupture. Therefore, the numerical analysis was performed for hemodynamic characteristics of the blood flow through the cerebral artery applying the various bifurcation angle and flow rate ratio. We analyze the flow characteristics using indices from the results of the numerical simulation. In addition, to investigate the flow pattern in the aneurysm according to the bifurcation angle and the flow rate ratio, we performed the numerical simulation on the supposition that the aneurysm occurs.