• 제목/요약/키워드: wall shear stress

검색결과 458건 처리시간 0.029초

Bending behavior of SWCNT reinforced composite plates

  • Chavan, Shivaji G.;Lal, Achchhe
    • Steel and Composite Structures
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    • 제24권5호
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    • pp.537-548
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    • 2017
  • In this paper presents bending characteristic of single wall carbon nanotube reinforced functionally graded composite (SWCNTRC-FG) plates. The finite element implementation of bending analysis of laminated composite plate via well-established higher order shear deformation theory (HSDT). A seven degree of freedom and $C^0$ continuity finite element model using eight noded isoperimetric elements is developed for precise computation of deflection and stresses of SWCNTRC plate subjected to sinusoidal transverse load. The finite element implementation is carried out through a finite element code developed in MATLAB. The results obtained by present approach are compared with the results available in the literatures. The effective material properties of the laminated SWCNTRC plate are used by Mori-Tanaka method. Numerical results have been obtained with different parameters, width-to-thickness ratio (a/h), stress distribution profile along thickness direction, different SWCNTRC-FG plate, boundary condition, through the thickness (z/h) ratio, volume fraction of SWCNT.

원심압축기의 성능에 미치는 형상변수들의 영향에 대한 수치적 연구 (Numerical Study on Effects of Geometrical Variables on Performance of A Centrifugal Compressor)

  • 김진혁;김광용
    • 한국전산유체공학회:학술대회논문집
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    • 한국전산유체공학회 2008년도 춘계학술대회논문집
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    • pp.152-155
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    • 2008
  • In this paper, the effect of modification of geometric variables on the performance of a centrifugal compressor blade has been studied numerically. The compressor contains six main blades and six splitter blades. Reynolds averaged Navier-Stokes (RANS) equations with shear stress turbulence (SST) model are discretized by finite volume approximations and solved on hexahedral grids for flow analysis. The design variables from blade lean angle at tip and middle of the blade have been modified. The isentropic blade efficiency and pressure have been predicted with the variation of the variables. Frozen rotor simulation is performed and adiabatic wall condition has been used. One of the six blades of compressor has been used for simulation to reduce the computational load. Optimum number of meshes has been selected by grid-dependency test, and this is used for all the simulations with changing geometric variables. The detailed flow analysis results have been reported as well as the effects of the variables.

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혈액 투석시 충혈방법에 따른 인조혈관 내 유동 특성에 관한 수치해석 연구 (NUMERICAL ANALYSIS ON THE BLOOD FLOW CHARACTERISTIC IN THE ARTERIOVENOUS GRAFT FOR DIFFERENT INJECTION METHOD OF BLOOD)

  • 김지태;성건혁;유홍선
    • 한국전산유체공학회지
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    • 제18권3호
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    • pp.14-19
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    • 2013
  • Renal failure patients have to operate arteriovenous graft for hemodialysis. Blood flow characteristics influence the patency rate of arteriovenous graft. Numerical investigation is performed with the arteriovenous graft according to injection of blood. As a result, when the injection is not applied to venous graft, the low wall shear stress region appears at venous anastomosis. It may cause intimal hyperplasia at venous anastomosis.

돌출형 거칠기벽이 있는 동심환형관의 유동에 대한 마찰계수 (Friction Factors for Flow in Concentric Annuli with Rib-Roughened Wall)

  • 안수환
    • 대한기계학회논문집B
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    • 제23권5호
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    • pp.587-592
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    • 1999
  • The combined effects of radius ratio and roughness pitch ratio on the turbulent fluid flow characteristics of the fully developed flow in the annullar tubes with rib-roughened core walls were determined for Reynolds number ranging from 12,000 to 66,000. To understand the underlying physical phenomena responsible for friction factor enhancement, measurements of velocity profiles and zero shear stress and maximum velocity positions were combined to propose the friction factor correlation. Friction factors were found to be a function of the roughness pitch ratio and radius ratio.

대동맥분기에서의 혈액유동: 맥도플러초음파 및 레이저도플러계측기를 사용한 연구 (Blood Flow in an Aortic Bifurcation Model: Pulsed Doppler Ultrasound and Laser Doppler Anemometry Studies)

  • 김영호
    • 대한의용생체공학회:학술대회논문집
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    • 대한의용생체공학회 1992년도 추계학술대회
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    • pp.43-46
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    • 1992
  • $\underline{In\;vitro}$ velocity measurements were made using both the pulsed Doppler ultrasound (PDU) machine and laser Doppler anemometer (LDA) system in order to investigate the flow characteristics near the aortic bifurcation. Velocities measured from the PDU machine was in good agreement with those from the LDA. The flow in the daughter branches was three-dimensional with a secondary flow. The oscillating wall shear stress with this secondary fluid motion is well correlated with the localization of the atherosclerosis.

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Design and Fabrication of Six-Degree of Freedom Piezoresistive Turbulent Water Flow Sensor

  • Dao, Dzung Viet;Toriyama, Toshiyuki;Wells, John;Sugiyama, Susumu
    • 센서학회지
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    • 제11권4호
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    • pp.191-199
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    • 2002
  • This paper presents the design concept, theoretical investigation, and fabrication of a six-degree of freedom (6-DOF) turbulent flow micro sensor utilizing the piezoresistive effect in silicon. Unlike other flow sensors, which typically measure just one component of wall shear stress, the proposed sensor can independently detect six components of force and moment on a test particle in a turbulent flow. By combining conventional and four-terminal piezoresistors in Si (111), and arranging them suitably on the sensing area, the total number of piezoresistors used in this sensing chip is only eighteen, much fewer than the forty eight piezoresistors of the prior art piezoresistive 6-DOF force sensor.

트렌치 굴착에 있어서 경량 흙막이 구조체의 안정성 해석 (Stability Analysis of the Light Weight Earth-Retaining Structure in the Trench Excavation)

  • 서성탁;허창환;김희덕;지홍기
    • 한국농공학회논문집
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    • 제46권2호
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    • pp.93-103
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    • 2004
  • In trench excavation, essential factor of earth-retaining temporary work structure should be easy taking to pieces and movement, and dead weight must be less. This paper studies about the light weight material and application as earth-retaining structure to prevent the slope failure of sand soil ground caused by the variation of groundwater level in trench excavation. That is, light weight earth-retaining structural is proposed and a simulation with FEM on application of proposed structural in sandy soil is presented. The results are summarized as follows; (1) The study proposed FRP H-shaped pannel for the light weight member, and also presented estimation method about stability. (2) Mechanical property (bending moment, shear force, axial force, displacement) were changed according to groundwater level, but these values had been within enough safety rate and allowable stress. Therefore, proposed light weight pannel with FRP is available for bracing structure in trench excavation.

증기터빈 바이패스밸브 케이지 유동장 해석관한 연구 (Analysis of Flow Field in a Steam Turbine Bypass Valve)

  • 최지용;조안태;김광용
    • 한국유체기계학회 논문집
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    • 제9권4호
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    • pp.36-42
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    • 2006
  • In the present work, characteristics of the flow in the cage of a steam turbine bypass control valve for thermal power plant are investigated. Experimental measurement for wall static pressure has been carried out to validate numerical solutions. And, the flowfield is analyzed by solving steady three-dimensional Reynolds-averaged Navier-Stokes equations. Shear stress transport (SST) model is used as turbulence closure. The effects of the flow area between stages of the cage on the pressure drop are also found.

속도 슬립모델 적용을 통한 마이크로 유체 시뮬레이션용 FEM 수치 코드 개발 (IMPLEMENTATION OF VELOCITY SLIP MODELS IN A FINITE ELEMENT NUMERICAL CODE FOR MICROSCALE FLUID SIMULATIONS)

  • ;명노신
    • 한국전산유체공학회지
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    • 제14권2호
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    • pp.46-51
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    • 2009
  • The slip effect from the molecular interaction between fluid particles and solid surface atoms plays a key role in microscale fluid transport and heat transfer since the relative importance of surface forces increases as the size of the system decreases to the microscale. There exist two models to describe the slip effect: the Maxwell slip model in which the slip correction is made on the basis of the degree of shear stress near the wall surface and the Langmuir slip model based on a theory of adsorption of gases on solids. In this study, as the first step towards developing a general purpose numerical code of the compressible Navier-Stokes equations for computational simulations of microscale fluid flow and heat transfer, two slip models are implemented into a finite element numerical code of a simplified equation. In addition, a pressure-driven gas flow in a microchannel is investigated by the numerical code in order to validate numerical results.

인조혈관의 단단문합에 대한 유동과 구조의 동시해석 (A Simultaneous Fluid -Structure Modeling of the End-to-End Vascular Graft Anastomosis)

  • 김영호
    • 대한의용생체공학회:의공학회지
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    • 제20권5호
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    • pp.593-599
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    • 1999
  • 수축절정기에 0.2mm, 0.4mm 두께의 소구경 인조혈관의 내경3.2mm의 동맥에 문합한 단단문합 주위의 유동과 구조해석을 동시에 수행하였다. 유동해석 결과 속도분포 및 벽단전률은 타 연구결과와 매우 유사하며 이론해와 매우 유사함을 보였다. 유동에 의해서 문합부 주위에 작용하는 응력은 문합부에 집중되며 이는 수십만 pa에 달했다. 또한 인조혈관과 동맥에 작용하는 원주방향의 응력을 이론해와 비교한 결과 서로 유사함을 보였으며 두께가 얇은 인조혈관을 사용하는 경우 문합부의 compliance mismatch 는 개선되나 반대로 응력은 더 많이 받음을 알 수 있었다. 본 연구를 통해서 유체에 의하여 혈관이 영향을 받는 심혈관계 현상을 연구하는데 있어서 이와 같은 유체-구조 상호작용을 고려하여 동시에 해결 하는 방법은 매우 유용할 것으로 생각된다.

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