풍향변화에 따른 정사각주형 구조물 주위의 유동특성

노형운,서상호 崇實大學校 生産技術硏究所 1996 論文集 Vol.26 No.1

The purpose of this study is to understand the flow patterns around prismatic structure with wind direction changes. Wind flows around a model of prismatic shape are investigated experimentally in the wind tunnel and simulated by using finite volume method. Velocity vectors adn pressure coefficients are obtained by the experiment and calculated by numerical method of 3-D flows. The numerical results are compared with those of experiments.

복합영화관의 성능기준 피난안전성능 평가

김운형,노삼규 대한건축학회 2003 대한건축학회 학술발표대회 논문집 - 계획계/구조계 Vol.23 No.1(계획계)

A performance-based fire safety design process is applied to analyze an evacuation safety performance of multiplex theater. By comparing a egress time performance criteria, ASET(Available Safety Egress Time) with RSET(Required Safety Egress Time) and analyzing a design fire scenario based on fire and egress computer, alternative design plan was suggested for better egress safety in emergency situation. The limitations of egress software including human behaviors and movement characteristics should be considered in this new design approach.

복합상영관 화재에 대한 화재모델링의 적용

허준호,김종훈,노삼규,김운형 한국화재소방학회 2004 한국화재소방학회논문지 Vol.18 No.1

다중이용시설의 화재시 온도분포 및 연기유동 모델링은 결정론적 모델(Deterministic Model)인 존모델(Zone Model) 필드모델(Field Model)이 주로 사용되고 있다. 존모델은 공간을 두개의 지역으로 구분하여 화재현상을 분석하고, 필드모델은 공간을 다수의 Cell로 구분하여 분석하고 있으나 두모델의 비교치에 대해서는 효용성 검증에 어려움을 겪고 있다. 따라서 화재현상의 모델링에 따른 수치적 이해와 관련자료의 검증을 통하여 실상황에 보다 근접한 새로운 모델의 개발이 요구된다. 본 논문에서는 두모델을 복합상영관은 실내공간에 적용하여 그 효용성을 분석해본 결과 공간 평균분포도에서는 존모델이, 세부적 공간현상에서는 필드모델의 적용이 적절한 것으로 판단된다. 또한 구체적인 화재의 성상과 감지기의 위치선정, 연기제어를 위한 제연설비의 검토를 위해서는 필드모델의 활용이 더욱 효과적이다. The deterministic modeling techniques like Zone model and Field model are mainly used for thermal distribution and smoke flow at fire case in multi use facilities. While Zone model analyse fire simulation by dividing spaces by 2 section, the Field model dividing many cells. However, the difficultly follows to prove efficiency between the two models when it applys. Therefore new modeling development is required which in closes to real situation by verify number algorithm and related data for fire modeling. The paper analyses the efficiency of two different fire modeling at interior spaces of multiplex cinema theater. It is found that the zone model for average distribution and the field model for detail space phenomenon are relevant to apply. Also, Filed model is useful to the result that fire analysis and position of detector and review for smoke control system.

Effects of the Velocity Waveform of the Physiological Flow on the Hemodynamics in the Bifurcated Tube

Roh, Hyung-Woon,Kim, Jae-Soo,Suh, Sang-Ho The Korean Society of Mechanical Engineers 2003 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.17 No.2

The periodicity of the physiological flow has been the major interest of analytic research in this field up to now Among the mechanical forces stimulating the biochemical reaction of endothelial cells on the wall, the wall shear stresses show the strongest effect to the biochemical product. The objective of present study is to find the effects of velocity waveform on the wall shear stresses and pressure distribution along the artery and to present some correlation of the velocity waveform with the clinical observations. In order to investigate the complex flow phenomena in the bifurcated tube, constitutive equations, which are suitable to describe the rheological properties of the non-Newtonian fluids, are determined, and pulsatile momemtum equations are solved by the finite volume prediction. The results show that pressure and wall shear stresses are related to the velocity waveform of the physiological flow and the blood viscosity. And the variational tendency of the wall shear stresses along the flow direction is very similar to the applied sinusoidal and physiological velocity waveforms, but the stress values are quite different depending on the local region. Under the sinusoidal velocity waveform, a Newtonian fluid and blood show big differences in velocity. pressure, and wall shear stress as a function of time, but the differences under the physiological velocity waveform are negligibly small.

Effects of the Velocity Waveform of the Physiological Flow on the Hemodynamics in the Bifurcated Tube

Hyung-Woon Roh,Jae-Soo Kim,Sang-Ho Suh 대한기계학회 2003 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.17 No.2

The periodicity of the physiological flow has been the major interest of analytic research in this field up to now. Among the mechanical forces stimulating the biochemical reaction of endothelial cells on the wall,the wall shear stresses show the strongest effect to the biochemical product. The objective of present study is to find the effects of velocity waveform on the wall shear stresses and pressure distribution along the artery and to present some correlation of the velocity waveform with the clinical observations. In order to investigate the complex flow phenomena in the bifurcated tube, constitutive equations, which are suitable to describe the rheological properties of the non-Newtonian fluids, are determined, and pulsatile momemtum equations are solved by the finite volume prediction. The results show that pressure and wall shear stresses are related to the velocity waveform of the physiological flow and the blood viscosity. And the variational tendency of the wall shear stresses along the flow direction is very similar to the applied sinusoidal and physiological velocity waveforms, but the stress values are quite different depending on the local region. Under the sinusoidal velocity waveform,a Newtonian fluid and blood show big differences in velocity, pressure, and wall shear stress as a function of time, but the differences under the physiological velocity waveform are negligibly small.<br/>

카테터 삽입에 따른 협착 관상동맥내 혈류특성변화

노형운(Hyung-Woon Roh),김재수(Jae-Soo Kim),서상호(Sang-Ho Suh),권혁문(Hyuk-Moon Kwon) 대한기계학회 2002 대한기계학회 춘추학술대회 Vol.2002 No.5

Catheters are used to measure translesional pressure gradients in the stenosed coronary arteries.<br/> Catheter insertions during coronary angioplasty cause flow obstructions. A narrowed flow cross section<br/> with catheter present effectively introduced a tighter stenosis than the enlarged residual stenoses after<br/> balloon angiplasty. In this study, three dimensional computer simulations are conducted to investigate<br/> the flow blockage effects due to the catheter insertions during the coronary angioplasty. This study is<br/> also extended to investigate the effects of stenotic vessel sizes and shapes, catheter size and<br/> positioning effects on the blood flow characteristics.

혈액의 점도변화가 인체혈관의 혈류특성에 미치는 영향

노형운(Hyung-Woon Roh),서상호(Sang-Ho Suh) 대한기계학회 2004 대한기계학회 춘추학술대회 Vol.2004 No.8

고해상 PIV 시스템을 이용한 분지관내 차원 맥동유동 가시화

노형운(Hyung-Woon Roh),서상호(Sang-Ho Suh),최진용(Jin-Yong Choi) 대한기계학회 2003 대한기계학회 춘추학술대회 Vol.2003 No.11

The objective of the present study was to visualize the pulsatile flow field in a branching model by<br/> using the high-resolution PIV system. A bifurcated flow system was built for the experiments in the<br/> pulsatile flow. Harvard pulsatile pump was used to generate the pulsatile velocity waveforms. Conifer<br/> powder as the tracing particles was added to water to visualize the flow fields. Two consecutive<br/> particle images at several cross sections of the flow filed were captured by the CCD cameras (1K*1K<br/> and 640*480). The results after the image processing clearly showed the recirculation zones and the<br/> formation of the paired secondary flows from the distal to the apex in the bifurcated model. The<br/> results also indicated that the flow velocities in the inner wall moved faster than those in the outer<br/> wall due to the inertial force effects and the helical motions generated in the branch flows as the flow<br/> proceeded toward the outer wall. While the PIV images from the 1K*1K camera were closer to the<br/> simulation results thantheimagesfromthe640*480camera,bothresultsofthePIVexperimentsusingthetwo<br/> camerasgenerallyagreed quitewellwiththeresultsfromthenumericalsimulation.

축압기의 변화가 고주파 유압시스템의 주파수 특성에 미치는 영향

노형운(Hyung-Woon Roh),김재수(Jae-Soo Kim),박남은(Nam-Eun Park),김양수(Yang-Soo Kim),전승배(Seung-Bae Jeon),나홍철(Hong-Chul Na) 대한기계학회 2003 대한기계학회 춘추학술대회 Vol.2003 No.4

Characteristics of the high frequency and pulsatile flow investigated experimentally to understand the flow phenomena in the hydraulic system. In the study, I axis fatigue tester which are widely used for automobile filed are selected. 4 Pressure transducer, amplifier, A/D convertor are used to analyse and to obtain the pulsatle pressure waveform with high frequencies in hydraulic system. Matlab are used. to analyse the characteristics of frequency. Variation of Pump input pressure and actuator acceleration frequency, pressure wave are measured with or without accumulators. For with accumulator, frequency amplitude of pressure are very lower than those of without accumulator due to absorbing function of accumulator. As the actuator acceleration frequency increased, effect of accumulator are very important to decrease the pulsatile pressure waveform with high frequencies.

협착이 발생된 관상동맥내 시퀜셜 문합의 효과

노형운(Hyung-Woon Roh),서상호(Sang-Ho Suh),권혁문(Hyuck-Moon Kwon),이병권(Byung-Kwon Lee) 대한기계학회 2003 대한기계학회 춘추학술대회 Vol.2003 No.4

Bypass anastomosis are frequently adopted for surgical treatments. After the bypass grafting, the<br/> bypass artery is often occluded due to restenosis and/or anastomotic neointimal fibrous hyperplasia<br/> phenomena. Optimal coronary bypass anastomosis should be investigated to improve the<br/> patency for the arterial bypass techniques. The objective of this study is to investigate the<br/> influence of bypass with sequential bypass effects in the stenosed coronary artery. Numerical analyses<br/> are focused on the understanding of the flow patterns for different sequential anastomosis techniques.<br/> Blood flow field is treated as two-dimensional incompressible laminar flow. The finite volume method<br/> is adopted for discretization of the governing equations. The Carreau model is employed as the<br/> constitutive equation for blood. To find the optimal sequential bypass anastomotic configurations, the<br/> mass flow rates at the outlet of different models are compared quantitatively.