• 제목/요약/키워드: Square duct

검색결과 174건 처리시간 0.026초

곡관덕트에서 난류맥동유동의 축방향 속도분포와 2차유동속도분포 (Axial Direction Velocity and Secondary Flow Distributions of Turbulent Pulsating Flow in a Curved Duct)

  • 손현철;이홍구;이행남;박길문
    • Journal of Advanced Marine Engineering and Technology
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    • 제24권6호
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    • pp.15-23
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    • 2000
  • In the present study, flow characteristics of turbulent pulsating flow in the square-sectional $180^{\circ}$curved duct are investigated experimentally. In order to measure axial direction velocity and secondary flow distributions, experimental studies for air flow are conducted in the square-sectional $180^{\circ}$curved duct by using the LDV system with the data acquisition and the processing system of the Rotating Machinery Resolver (RMR) and the PHASE software. The experiment is conducted on seven sections form the inlet($\phi=0^{\circ}$) to the outlet($\phi=180^{\circ}$) at $30^{\circ}$intervals of the duct. The results obtained from the experimentation are summarized as follows : In the axial direction velocity distributions of turbulent pulsating flow, when the ratio of velocity amplitude (A1) is less than one, there is hardly any velocity change in the section except near the wall and in axial velocity distribution along the phase. The secondary flow of turbulent pulsating flow has a positive value at the bend angle of $150^{\circ}$regardless of the ratio of velocity amplitude. The dimensionless value of secondary flow becomes gradually weak and approaches zero in the region of bend angle $180^{\circ}$without regard to the ratio of velocity amplitude.

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정사각단면 $180^{\circ}C$ 곡덕트에서 층류진동유동의 유동 특성에 관한 연구 (A study on flow characteristics of laminar oscillatory flows in a square-sectional $180^{\circ}C$ curved duct)

  • 박길문;조병기;봉태근
    • 대한기계학회논문집B
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    • 제22권2호
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    • pp.139-152
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    • 1998
  • In the present study, the flow characteristics of developing laminar oscillatory flows in a square -sectional 180 deg. curved duct are investigated experimentally. The experimental study using air in a square-sectional 180 deg. curved duct is carried out to measure velocity distributions with a data acquisition and LDV (Laser Doppler Velocimetry) processing system. In this system, Rotating Machinery Resolver (RMR) and PHASE program are used to obtain the results of unsteady flows. The major flow characteristics of developing oscillatory flows are found by analyzing velocity curves, mean velocity profiles, time-averaged velocity distribution of secondary flow, wall shear stress distributions, and entrance lengths. In a lower dimensionless angular frequency, the axial velocity distribution of laminar oscillatory flow in a curved duct shows a convex shape in a central part and axial symmetry. The maximum value of wall shear stress in a lower dimensionless angular frequency is located in an outside wall, but according to increasing the dimensionless angular frequency, the maximum of wall shear stress is moved to inner wall. The entrance lengths of laminar oscillatory flows in a square-sectional 180 deg. curved duct is obtained to 90 deg. of bended angle of duct in this experimental conditions.

충돌제트에 의한 덕트내 사각발열체의 냉각특성에 관한 수치해석적 연구 (A Numerical Study on Cooling Characteristics by Impinging Jet at a Square Heating Element with Duct)

  • 윤정호;김시범;김동균;이치우;김지훈
    • Journal of Advanced Marine Engineering and Technology
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    • 제29권1호
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    • pp.42-48
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    • 2005
  • Because Impinging jet has excellent heat & mass transfer characteristics. it has many advantages of cooling. drying. etc and widely applied at industrial fields. Therefore, there have been many experimental investigations and theoretical studies about Impinging jet. The present study is about a cooling characteristic by Impinging jet for a Square Plate on Duct and investigated this characteristic through three-dimensions numerical analysis, using FLUENT. As the result of this study, heat transfer effect is the most appropriate condition when the ratio of distance is 6 between nozzle exit diameter and heat source. diameter of duct is 90mm and height of duct is 60mm. In addition. under the influence of injected jet. stagnant fluid flow into free jet field and this affected the whole flow field. So the shape of duct is a important factor and the researcher confirmed the need of investigation about duct.

나선형 사각덕트 내의 압력강하 (Pressure Drop in a Helical Square Duct)

  • 유승엽;윤주현;이두정
    • 대한기계학회:학술대회논문집
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    • 대한기계학회 2001년도 춘계학술대회논문집E
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    • pp.398-403
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    • 2001
  • Pressure drop at a helical square duct orifice is numerically evaluated. The orifice is installed at the entrance of a once-through steam generator tube to suppress flow instabilities. The calculated results are compared with the available experimental correlations, and showed good agreement. Effects of curvature ratio and characteristics of the secondary flow with Reynolds number are reported. Through the numerical simulations, pressure drop mechanisms were well understood inside the compact and complicated orifice geometry.

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회전하는 정사각 직관내 난류유동 (Investigation of Turbulent Flow in Rotating Straight Square Duct)

  • 전건호;최영돈;김동철;최선용;임홍영
    • 대한기계학회:학술대회논문집
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    • 대한기계학회 2001년도 춘계학술대회논문집E
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    • pp.766-771
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    • 2001
  • An experimental study was undertaken to investigate the effect of coriolis force for the turbulent flow at low Reynolds numbers in a rotating straight square duct. The study was carried out using a hot-wire anemometer. The flow Reynolds number based on the hydraulic diameter ranged from 4,000 to 18,000 and Rotation number ranged from 0 to 0.196. At Re=9000, developing turbulent flow was calculated for mean velocity and Reynolds stress. Pressure coefficient and energy dissipation spectrum were also calculated.

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종횡비가 큰 사각 덕트내 난류 유동의 대류 열전달 증진 기술에 대한 연구 (TURBULENCE HEAT TRANSFER ENHANCEMENT TECHNIQUE FOR SQUARE DUCT WITH HIGH ASPECT RATIO)

  • 이찬용;신승원;정하승;박승호
    • 한국전산유체공학회:학술대회논문집
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    • 한국전산유체공학회 2010년 춘계학술대회논문집
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    • pp.305-307
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    • 2010
  • In this study, we develop a method to achieve heat transfer enhancement inside a square duct with high aspect ratio without changing any inner structures. Especially, a method to lower the possible maximum temperature is suggested if constant heat flux is provided to single surface of square duct. Knowing the fact that heat transfer rate is inversely proportional to flow area, we proposed tapered channel concept which uses narrower gap toward the flow exit where the maximum temperature is expected. To maintain equivalent power consumption, inlet section has been enlarged. To verify the proposed concept, experimental tests have been performed.

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정4각덕트의 입구영역에서 난류 비정상유동에 대한 이론과 실험적 연구 (A Theoretical and Experimental Study on the Developing Turbulent Unsteady Flows in the Entrance Region of a Square Duct)

  • 고영하
    • Journal of Advanced Marine Engineering and Technology
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    • 제22권5호
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    • pp.643-651
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    • 1998
  • Turbulent unsteady flows in the entrance region of a square duct are investigated with a hot-wire anemometer system. The velocity waveforms the mean and turbulence components of the axial velocity and the entrance length are obtained as a major characteristics of the developing turbulent unsteady flows. An inviscid flow theory is presented to describe the developing axial mean velocity profiles. A good agreement is seen between the measured and theoretically predicted values. The propagation of turbulence generated near the entrance of the square duct is satisfactorily approximated by an empirical correlation of the propagation of turbulence proposed so far. The local turbulence intensi-ty is found to be a little smaller in the accelerating phase than in the decelerating phase. The entrance length is about 60 times as large the hydraulic diameter.

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비선형 k-$\varepsilon$ 난류모델에 따른 정사각형 덕트내 난류유동 수치해석(8권1호 게재논문중 그림정정) (Simulation of Turbulent Flow in a Square Duct with Nonlinear k-$\varepsilon$ Models)

  • 명현국
    • 한국전산유체공학회지
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    • 제8권2호
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    • pp.57-63
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    • 2003
  • Two nonlinear κ-ε models with the wall function method are applied to the fully developed turbulent flow in a square duct. Typical predicted quantities such as axial and secondary velocities, turbulent kinetic energy and Reynolds stresses are compared in details both qualitatively and quantitatively with each other. A nonlinear κ-ε model with the wall function method capable of predicting accurately duct flows involving turbulence-driven secondary motion is presented in the present paper. The nonlinear κ-ε model of Shih et al.[1] adopted in a commercial code is found to be unable to predict accurately duct flows with the prediction level of secondary flows one order less than that of the experiment.

Buckling of insulated irregular transition flue gas ducts under axial loading

  • Ramadan, H.M.
    • Structural Engineering and Mechanics
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    • 제43권4호
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    • pp.449-458
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    • 2012
  • Finite element buckling analysis of insulated transition flue ducts is carried out to determine the critical buckling load multipliers when subjected to axial compression for design process. Through this investigation, the results of numerical computations to examine the buckling strength for different possible duct shapes (cylinder, and circular-to-square) are presented. The load multipliers are determined through detailed buckling analysis taking into account the effects of geometrical construction and duct plate thickness which have great influence on the buckling load. Enhancement in the buckling capacity of such ducts by the addition of horizontal and vertical stiffeners is also investigated. Several models with varying dimensions and plate thicknesses are examined to obtain the linear buckling capacities against duct dimensions. The percentage improvement in the buckling capacity due to the addition of vertical stiffeners and horizontal Stiffeners is shown to be as high as three times for some cases. The study suggests that the best location of the horizontal stiffener is at 0.25 of duct depth from the bottom to achieve the maximum buckling capacity. A design equation estimating the buckling strength of geometrically perfect cylindrical-to-square shell is developed by using regression analysis accurately with approximately 4% errors.

3차원 일반 좌표계에서의 PISO, SIMPLE, SIMPLE-C 알고리즘의 비교 (A Comparative Study of PISO, SIMPLE, SIMPLE-C Algorithms in 3-dimensional Generalized Coordinate Systems)

  • 박준영;백제현
    • 한국전산유체공학회지
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    • 제1권1호
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    • pp.26-34
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    • 1996
  • The performance of the SIMPLE, SIMPLE-C and PISO algorithms for the treatment of the pressure-velocity coupling in fluid flow problems were examined by comparing the computational effort required to obtain the same level of the convergence. Example problems are circular duct and 90-degree bent square-duct. For circular duct case, laminar and turbulent flow were computed. For 90-degree bent square-duct case, laminar flow was simulated by the time-marching method as well as the iterative method. The convergence speed of the other two algorithms are not always superior to SIMPLE algorithm. SIMPLE algorithm is faster than SIMPLE-C algorithm in the simple laminar flow calculations. The application of the PISO algorithm in three dimensional general coordinates is not so effective as in two-dimensional ones. Since computational time of PISO algorithm is increased at each time step(or iterative step) in three dimension, the total convergence speed is not decreased. But PISO algorithm is stable for large time step by using time marching method,.

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