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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.
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.
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.
Lee, D.S.,Choi, H.G.,Wan Woo, K.,Kang, D.G.,Lee, H.S.,Oh, H.,Ro Lee, K.,Kim, Y.C. North-Holland ; Elsevier Science Ltd 2013 european journal of pharmacology Vol.715 No.1
Saussurea pulchella (Asteraceae) is widely distributed in Korea and has been used in Korean folk medicine for the treatment of inflammation, hypertension, hepatitis, and arthritis. Pulchellamin G is an amino acid-sesquiterpene lactone conjugate isolated from S. pulchella. In the present study, we focused on the anti-inflammatory effect of pulchellamin G, which acts by inducing the expression of heme oxygenase (HO)-1. HO-1 plays important roles in cytoprotection since it has antioxidant, anti-inflammatory, antiproliferative, and antiapoptotic properties. Pulchellamin G inhibited the mRNA and protein expression of inducible nitric oxide synthase (iNOS), iNOS-derived nitric oxide (NO), and cyclooxygenase (COX)-2 and COX-derived prostaglandin E2 (PGE<SUB>2</SUB>) production in lipopolysaccharide (LPS)-stimulated murine peritoneal macrophages. The compound also reduced tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) production and suppressed the phosphorylation and degradation of IκB-α and nuclear translocation of p65 in murine peritoneal macrophages in response to LPS stimulus. The inhibitory effects of pulchellamin G on nuclear factor kappa B (NF-κB) translocation was impaired by co-treatment of the cells with HO activity inhibitor tin protoporphyrin (SnPP). By using SnPP, we verified that the inhibitory effects of pulchellamin G on the pro-inflammatory mediators NO, PGE<SUB>2</SUB>, TNF-α, and IL-1β are associated with induction of HO-1 expression. Our data suggest that pulchellamin G might have potent therapeutic effects and it should be considered in the development of treatments for various inflammatory diseases.