• 제목/요약/키워드: Bifurcation Angle

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

  • 정대진;장창래;정관수
    • 한국수자원학회논문집
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    • 제53권8호
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    • pp.617-626
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    • 2020
  • 본 연구에서는 TELEMAC-2D를 이용하여 개수로 분류부에서 분류각과 분류유량비 변화에 따른 유속분포, 흐름분리구역의 크기, 분류각과 유량비 변화의 상관관계를 파악하였다. 상·하류단 경계조건의 변화 없이 분류각만 90°에서 45°로 감소하면 주흐름에서 분리되어 분류수로로 유입되는 흐름의 곡률반경이 증가하고 급격한 흐름방향의 전환에 의한 에너지손실은 감소하며, 주수로와 분류수로 하류방향으로 흐르는 흐름의 관성력과 하류단 경계조건에 의한 압력경사의 영향으로 분류수로에 유입되는 분류유량비가 0.523에서 0.785로 약 1.5배 증가하였다. 분류부 상류 유입흐름의 프루우드 수가 F1 = 0.45~0.74인 흐름에서 분류각을 90°에서 45°로 15° 간격으로 감소할 때마다 분류유량비는 각각 6~10%, 17~30%, 32~54%로 비선형적으로 증가하며, F1가 최대 0.74인 흐름에서 분류유량비 증가율이 31.1%로 최소값을 나타내고 F1 = 0.58 일 때 분류유량비가 0.7 이하이면서 최대 분류유량비 증가율 53.5%을 나타내며, F1이 0.58보다 감소할수록 분류유량비가 0.7을 초과하면서 그 증가율도 함께 감소하게 된다. F1 > 0.4인 흐름은 F1 < 0.4의 흐름보다 무차원 흐름분리구역의 폭(SW/B) 변화율은 약 2.56배 높으며 무차원 흐름분리구역 길이(SL/B) 변화율은 약 5.5배 높게 나타난다.

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

  • 신장용;고성희;홍경태;홍금식
    • 한국해양공학회지
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    • 제19권2호
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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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    • 제21권3호
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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.

전방순환동맥류 발생 위치에 대한 혈류량 및 분지각의 영향 및 동맥류 발생 전후의 유동 변화에 관한 수치해석 연구 (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)

  • 김소윤;노경철;유홍선
    • 한국전산유체공학회지
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    • 제16권4호
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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.

전방순환동맥류 발생 위치에 대한 혈류량 및 분지각의 영향 및 동맥류 발생 전후의 유동 변화에 관한 수치해석 연구 (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)

  • 김소윤;노경철;유홍선
    • 한국전산유체공학회:학술대회논문집
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    • 한국전산유체공학회 2011년 춘계학술대회논문집
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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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    • 제3권4호
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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.

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

  • 이인섭;유홍선
    • 대한기계학회:학술대회논문집
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    • 대한기계학회 2003년도 추계학술대회
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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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주기 가속도 위상변화에 따른 협착 및 분지 혈관의 혈류 특성에 대한 수치해석적 연구 (NUMERICAL STUDY ON THE BLOOD FLOW CHARACTERISTICS OF STENOSED AND BIFURCATED BLOOD VESSELS WITH A PHASE ANGLE CHANGE OF A PERIODIC ACCELERATION)

  • 노경철;조성욱;이성혁;유홍선
    • 한국전산유체공학회지
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    • 제13권3호
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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.

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

  • 김무강
    • 대한수의학회지
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    • 제19권1호
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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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Load/Unload 하드디스크 드라이브 시스템에의 Fold Bifurcations의 교란 유한요소 해석 (Perturbed Finite Element Analysis of Fold Bifurcations in Load/unload Bard Disk Drive Systems)

  • 황평;콴폴리냐
    • 정보저장시스템학회:학술대회논문집
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    • 정보저장시스템학회 2005년도 추계학술대회 논문집
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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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