Large-Scale Vortical Structures in The Developing Plane Mixing Layer Using LES

Seo, Taewon,Kim, Yeung-Chan,Keum, Kihyun The Korean Society for Aeronautical and Space Scie 2001 International Journal of Aeronautical and Space Sc Vol. No.

Study of turbulent mixing layers has been a popular subject from the point of view of both practical application and phenomenological importance in engineering field. Turbulent mixing layers can be applied in many fields where rapid transition to turbulence is desirable in order to prevent boundary layer separation or to enhance mixing. The ability to control mixing, structure and growth of the shear flow would obviously have a considerable impact on many engineering applications. In addition to practical applications, free shear flows are one of the simplest flows to understand the fundamental mechanism in the transition process to turbulence. After the discovery of large-scale vortical structure in free shear flows many researchers have investigated the physical mechanism of generation and dissipation processes of the vortical structure. This study investigated the role of the large-scale vortical structures in the turbulent mixing layer using LES(Large-Eddy Simulation). The result shows that the pairing interaction of the vortical structure plays an important role in the growth rate of a mixing layer. It is found that the turbulence quantities depend strongly on the velocity ratio. It is also found that the vorticity in the high-velocity-side can extract energy from the mean flow, while the vorticity in the low-velocity-side lose energy by the viscous dissipation. Finally the results suggest the guideline to obtain the desired flow by control of the velocity ratio.

Numerical simulations of blood flow in arterial bifurcation models

Seo, Taewon 한국유변학회 2013 Korea-Australia rheology journal Vol.25 No.3

In the study, two different arterial bifurcation model geometries were used in the flow simulation. The model 1 is assumed the internal carotid artery (ICA) and the external carotid artery (ECA) branches of the bifurcation aligned in parallel to each other, while the model 2 is the typical carotid geometry. In the computation the Non-Newtonian behavior of blood was described using Carreau model. Generally, in the comparison between Newtonian and Non-Newtonian results good agreement was observed in the velocity profiles, while some discrepancies were found in the temporal wall shear stress (WSS) distributions as well as pressure profiles due to the shear thinning behavior. The temporal evolution of WSS periodically increases and decreases closely that of the inlet velocity waveform. It was also observed that the reversed flow region in the ICA of model 2 is 2.5 times larger than that of model 1. As a result, the variation of the flow characteristics can be dependent on the geometry as well as the arterial bifurcation geometry plays an important role in the development of atherosclerosis.

Drug-Eluting Stent Design is a Determinant of Drug Concentration at the Endothelial Cell Surface

Seo, Taewon,Lafont, Antoine,Choi, Sun-Young,Barakat, Abdul I. Springer-Verlag 2016 Annals of biomedical engineering Vol.44 No.2

<P>Although drug-eluting stents (DES) have greatly reduced arterial restenosis, there are persistent concerns about stent thrombosis. DES thrombosis is attributable to retarded vascular re-endothelialization due to both stent-induced flow disturbance and the inhibition by the eluted drug of endothelial cell proliferation and migration. The present computational study aims to determine the effect of DES design on both stent-induced flow disturbance and the concentration of eluted drug at the arterial luminal surface. To this end, we consider three closed-cell stent designs that resemble certain commercial stents as well as three 'idealized' stents that provide insight into the impact of specific characteristics of stent design. To objectively compare the different stents, we introduce the Stent Penalty Index (SPI), a dimensionless quantity whose value increases with both the extent of flow disturbance and luminal drug concentration. Our results show that among the three closed-cell designs studied, wide cell designs lead to lower SPI and are thus expected to have a less adverse effect on vascular re-endothelialization. For the idealized stent designs, a spiral stent provides favorable SPI values, whereas an intertwined ring stent leads to an elevated SPI. The present findings shed light onto the effect of stent design on the concentration of the eluted drug at the arterial luminal surface, an important consideration in the assessment of DES performance.</P>

Large-Scale Vortical Structures in The Developing Plane Mixing Layer Using LES

Taewon Seo,Yeung-Chan Kim,Kihyun Keum 한국항공우주학회 2001 International Journal of Aeronautical and Space Sc Vol.2 No.1

The Air Flow Model Study within the Electrostatic Precipitator

Seo, Taewon 안동대학교 공업기술연구소 1996 공업기술연구논문집 Vol.3 No.1996

As the industries are rapidly growing, the stringent regulation of clean air is widely spread in the developed countires. In the sense of clean air, the electrostatic precipitator is one of the gas cleaning equipment in the large-scale industries in that the forces separating the particulate from the gas stream are applied directly to the particles. The purposes of this study are to know the flow characteristics and to obtain the uniform velocity distribution within the electrostatic precipitator. The parametric study is conducted to control and manage the flow field in the diverging channel to obtain the satisfying result. The gas flow control devices which are the parameters to be considered to manage the air flow modeling of the electrostatic precipitator are following; ● Guide vane ● Perforated plate ● Grid attached on the perforated plates By the adequate combination of these flow control devices, we can get a uniform velocity distribution within the electrostatic precipitator.

Computational Analysis of the Performance of Drug-Eluting Stent Using Effective Index (EI)

Taewon Seo,Sun-Young Choi,Abdul Barakat 대한기계학회 2016 대한기계학회 춘추학술대회 Vol.2016 No.4

[세션초청논문] 외벽 청소 로봇 상용화를 위한 연구

서태원(TaeWon Seo) 대한기계학회 2019 대한기계학회 춘추학술대회 Vol.2019 No.11

협착 동맥에서의 맥동 혈류 유동에 대한 수치해석적 연구

서태원(Taewon Seo),Bahtiyor Buriev 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.5

In the present computational study, the pulsatile flow in simple stenotic artery model was investigated. A 1 ㎐ non-reversing sinusoidal velocity was imposed at the flow inlet and the corresponding Womersley number based on the vessel radius is 2.75. The simulations of fluid flow with 25%, 50% and 75% stenosis respectively were carried using commercial code ADINA 8.4. As stenosis and Reynolds number increase, the maximum wall shear stress(WSS) increases while the minimum WSS decreases. It is found that the fluid mechanical disturbances due to stenosis 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.

객체 마스킹을 통한 동영상 메타데이타 편집 도구의 설계 및 구현

서태원(Taewon Seo),서진호(Jinho Seo),이상준(Sangjun Lee) 한국정보과학회 2009 한국정보과학회 학술발표논문집 Vol.36 No.2C

동영상 데이타는 2차원의 이미지가 시간에 따라 변화하는 3차원의 데이타로 볼 수 있으며, 동영상 내에 등장하는 객체 등의 컨텐츠를 효율적으로 검색하고 브라우징 하는데 복잡한 기술이 필요하다. 본 논문에서는 객체 마스킹을 통해 동영상에 메타데이타를 삽입하고 이를 XML로 저장하는 동영상 메타데이타 편집 도구와 이를 브라우징할 수 있는 플레이어를 제안한다. 제안된 기법은 기존의 연구에서 특정한 객체가 누락되거나 짧은 재생 시간에 비해 많은 대표 프레임이 추출되어 브라우징하는데 어려움이 따르는 문제를 해결할 수 있다. 이와 더불어 본 논문에서는 대규모 메타데이타의 효율적 전송을 고려한 저장 구조 및 전송 방법을 개선하여 불필요한 네트워크 트래픽을 줄일 수 있는 기법을 제시한다.

약물분출 스텐트 주위 유동형태와 약물침전에 대한 수치해석

서태원(Taewon Seo) 대한기계학회 2011 대한기계학회 춘추학술대회 Vol.2011 No.4

본 연구는 맥동유동 조건하에서 이상적인 원형 환 스텐트와 Intertwined 스텐트의 삽입에 의해 야기되는 혈류유동 형태와 스텐트 표면에서 방출되는 약물의 농도분포를 조사하는 것이다. 본 연구를 통해 Intertwined 스텐트의 스텐트 사이 영역에서 약물농도는 원형 환 스텐트에 비해 더 많이 분포해 있는 것을 알 수 있었다. 주어진 스텐트의 형상에 대하여 스텐트 사이 영역에서의 국소적인 약물농도분포는 레이놀드 수가 증가함에 따라 감소하는 것으로 나타났다. 주어진 레이놀드 수에 대하여는 약물 농도분포는 스텐트의 형상과는 비교적 무관함을 알 수 있다. 원형 환 스텐트보다 Intertwined 스텐트가 스텐트 사이 영역과 스텐트 하류영역에서혈관 벽면을 따른 약물 농도분포는 크게 나타나는 것을 볼 수 있다. This study is investigated to determine the flow patterns induced by implanted stent and the drug concentration profiles of drug-eluting stents (DES) for ideal circular ring stent and intertwined stent models for pulsatile flow. As a result, the drug concentration for the intertwined stent is higher over the in-stent region to comparison with the ideal stents. For a given stent geometry, the local drug concentration in the in-stent region decreases with Reynolds number, while for a given Reynolds number, the local drug concentration is relatively insensitive to the stent geometry. The results have shown that drug concentration along the arterial wall is significantly higher within the in-stent and the post-stent regions for the intertwined stent geometry than for the ideal stent geometries.