• Title/Summary/Keyword: Bifurcation Angle

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Numerical study on flow characteristics at dividing open-channel with changing bifurcation angle using TELEMAC-2D (TELEMAC-2D모형을 이용한 분류각 변화에 따른 개수로 흐름특성변화 수치모의 연구)

  • Jung, Daejin;Jang, Chang-Lae;Jung, Kwansue
    • Journal of Korea Water Resources Association
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    • v.53 no.8
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    • pp.617-626
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    • 2020
  • This study investigates changes of bifurcation discharge ratio, flow velocity distributions and characteristics of separation zone due to variation of bifurcation angle by using TELEMAC-2D model. When the bifurcation angle is reduced from 90° to 45° without changing the boundary conditions, the bifurcation discharge ratio increased by 1.5 times from 0.523 to 0.785 because of increasing the radius of curvatures, the inertia force of the downstream flow, and the pressure gradient by the downstream boundary conditions. The bifurcation discharge ratio increases non-linearly whenever the bifurcation angle decreases by 15° intervals from 90° to 45° in flow with the upstream Froude number of 0.45 to 0.74. In flow with a maximum Froude number of 0.74, the rate of increase for bifurcation discharge ratio is 31.1% and the minimum value. When the Froude number is 0.58, the bifurcation discharge ratio is 0.7 or less, and the maximum rate of increase for that ratio is 53.5%. As the upstream Froude number decreases less than 0.58, the bifurcation discharge ratio exceeds 0.7, and the rate of increase decreases. When the upstream Froude number is 0.4 higher, the dimensionless width and length changing ratio of the separation zone are about 2.56 and 5.5 times higher than in 0.4 or less.

The Effect of Fleet-Angle on Sway Motions of a Cargo: Compatibility and Bifurcation Conditions (화물과 트롤리가 만드는 로프각이 화물의 진자운동에 미치는 영향: 적합조건과 분기조건)

  • SHIN JANG-RYONG;GOH SUNG-HEE;HONG KYUNG-TAE;HONG KEUM-SHIK
    • Journal of Ocean Engineering and Technology
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    • v.19 no.2 s.63
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    • pp.60-66
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    • 2005
  • This paper investigates the relationship between the fleet-angle of the hoisting rope and the swaying and pitching angles of a cargo in container cranes. It is found that for a given disturbance, when the fleet-angle is large, the sway Angle becomes smaller, but the pitching angle becomes larger. Therefore, for a quick suppression of a sway motion, it is desirable to have a large fleet-angle. The compatibility and bifurcation conditions, regarding instability, are characterized.

Numerical study of the effects of periodic body acceleration (PGZ) and bifurcation angle in the stenosed artery bifurcation

  • Ro, Kyoung-Chul;Ryou, Hong-Sun
    • Korea-Australia Rheology Journal
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    • v.21 no.3
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    • pp.175-183
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    • 2009
  • This article describes the numerical investigation of blood flow in the stenosed artery bifurcation with acceleration of the human body. Using the commercial software FLUENT, three-dimensional analyses were performed for six simulation cases with different body accelerations and bifurcation angles. The blood flow was considered to be pulsation flow, and the blood was considered to be a non-Newtonian fluid based on the Carreau viscosity model. In order to consider periodic body acceleration, a modified, time-dependent, gravitational-force term was used in the momentum equation. As a result, flow variables, such as flow rate and wall shear stress, increase with body acceleration and decrease with bifurcation angle. High values of body acceleration generate back flow during the diastolic period, which increases flow fluctuation and the oscillatory shear index at the stenosis.

NUMERICAL ANALYSIS FOR THE EFFECT OF BLOOD FLOW RATE AND BIFURCATION ANGLE ON THE LOCATION OF ANTERIOR CIRCULATION ANEURYSM AND THE CHANGE OF BLOOD FLOW CHARACTERISTICS AFTER ANEURYSM FORMATION (전방순환동맥류 발생 위치에 대한 혈류량 및 분지각의 영향 및 동맥류 발생 전후의 유동 변화에 관한 수치해석 연구)

  • Kim, S.Y.;Ro, K.C.;Ryou, H.S.
    • Journal of computational fluids engineering
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    • v.16 no.4
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    • pp.64-71
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    • 2011
  • 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.

NUMERICAL ANALYSIS FOR THE EFFECT OF BLOOD FLOW RATE AND BIFURCATION ANGLE ON THE LOCATION OF ANTERIOR CIRCULATION ANEURYSM AND THE CHANGE OF BLOOD FLOW CHARACTERISTICS AFTER ANEURYSM FORMATION (전방순환동맥류 발생 위치에 대한 혈류량 및 분지각의 영향 및 동맥류 발생 전후의 유동 변화에 관한 수치해석 연구)

  • Kim, S.Y.;Ro, K.C.;Ryou, H.S.
    • 한국전산유체공학회:학술대회논문집
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    • 2011.05a
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    • pp.161-168
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    • 2011
  • 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.

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Effect of sweep angle on bifurcation analysis of a wing containing cubic nonlinearity

  • Irani, Saied;Amoozgar, Mohammadreza;Sarrafzadeh, Hamid
    • Advances in aircraft and spacecraft science
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    • v.3 no.4
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    • pp.447-470
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    • 2016
  • Limit cycle oscillations (LCO) as well as nonlinear aeroelastic analysis of a swept aircraft wing with cubic restoring moments in the pitch degree of freedom is investigated. The unsteady aerodynamic loading applied on the wing is modeled by using the strip theory. The harmonic balance method is used to calculate the LCO frequency and amplitude for the swept wing. Finally the super and subcritical Hopf bifurcation diagrams are plotted. It is concluded that the type of bifurcation and turning point location is sensitive to the system parameters such as wing geometry and sweep angle.

The Numerical study for flow characteristics of bifurcation in blood vessel (혈관 분지부의 유동 특성에 대한 수치해석 연구)

  • Lee, In-Sub;Ryou, Hong-Sun
    • Proceedings of the KSME Conference
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    • 2003.11a
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    • pp.741-746
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    • 2003
  • The main objective of present study is to obtain information for flow characteristics, such as velocity and wall shear stress, of bifurcation in blood vessel. Branch flows for Newtonian fluids are simulated by using Fluent V.6.0. The numerical simulations are carried out for five cases divided by different values of bifurcation angle and area ratio. As a result of simulation, high wall shear stress is appeared at the bifurcated region. As increasing bifurcation angle, pressure drop is increasing. In addition, as the area is decreasing, pressure drop and wall shear stress is increasing.

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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.

Comparative Anatomic Structures of Nonhuman Primate Lungs 1. Literature Review (영장동물폐(靈長動物肺)의 비교해부학적연구(比較解剖學的硏究) 1. 문헌적고찰(文獻的考察))

  • Kim, Moo Gorng;Kim, James C.S.
    • Korean Journal of Veterinary Research
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    • v.19 no.1
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    • pp.1-8
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    • 1979
  • Detailed human gross anatomic structures have been characterized. No similar data are available in nonhuman primate species in spite of close phylogenic similarity found between man and nonhuman primates. The ever increasing incidence of lung cancer and air pollution related respiratory ailments found in man emphasizes the need for an ideal animal model for studying pathogenesis of these various human pulmonary diseases. Thus, detailed investigation of pulmonary structures found in various species of nonhuman primates is warranted. For determining primate gross pulmonary anatomic structure, published works concerning the number of tracheal cartilage, angle of tracheal bifurcation, caliber of trachea, lung lobe and bifurcation position of trachea recorded for several species of nonhuman pimates, were reviewed. Limited information is available concerning the number of tracheal cartilage, width of tracheal cartilage, angle of bronchus, caliber of trachea and bronchus, and the bifurcation position of the trachea including the length of bronchus on nonhuman primates. Since scanty data have been gathered with no specific reference to their age, sex and body weight, they have no comparative values.

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Perturbed Finite Element Analysis of Fold Bifurcations in Load/unload Bard Disk Drive Systems (Load/Unload 하드디스크 드라이브 시스템에의 Fold Bifurcations의 교란 유한요소 해석)

  • Hwang Pyung;Khan Polina V.
    • 정보저장시스템학회:학술대회논문집
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    • 2005.10a
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    • pp.177-178
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    • 2005
  • The load/unload behavior of the hard disk drive slider is studied in terms of the air bearing static characteristics. The numerical continuation methods are applied to calculate suspension force - equilibrium position curve. The critical preloads of the femto size slider are analyzed. The hi-stability conditions are depicted on the skew angle - preload diagram. The perturbation method is used to check the stability of the solution branches.

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