• 제목/요약/키워드: Square duct

검색결과 174건 처리시간 0.023초

비선형 ${\kappa}-{\epsilon}$ 난류모델에 따른 정사각형 덕트내 난류유동 예측 (Prediction of Turbulent Flow in a Square Duct with Nonlinear ${\kappa}-{\epsilon}$ Models)

  • 명현국
    • 대한기계학회:학술대회논문집
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    • 대한기계학회 2003년도 춘계학술대회
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    • pp.1980-1985
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    • 2003
  • Two nonlinear ${\kappa}-{\epsilon}$ 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 ${\kappa}-{\epsilon}$ 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 ${\kappa}-{\epsilon}$ model 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.

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

  • 명현국
    • 한국전산유체공학회지
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    • 제8권1호
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    • pp.23-29
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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.

정사각단면 $180^{\circ}$ 곡관덕트의 입구영역에서 비정상층류유동의 유동특성에 관한 연구 (A Study on Characteristics of Unsteady Laminar Flows in Squaresectional $180^{\circ}$ Curved Duct)

  • 박길문;모양우;조병기
    • 대한의용생체공학회:의공학회지
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    • 제17권4호
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    • pp.515-524
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    • 1996
  • The flow characteristics of developing unsteady laminar flow in a square-sectional $180^{\circ}$ curved duct are experimentally investigated by using laser doppler velocimerty (LDV) system with data acquisition and processing system of rotating machinery resolver(RMR) and PHASE software. The major flow characteristics of developing laminar pulsating flows are presented by mean velocity profilel velocity distribution of secondary flow, wall shear stress distributions, entrance lengths according to dimensionless angular frequency($\omega^+$), velocity amplitude ratio($A^1$), and time-averaged Dean number($De_ta$). The velocity profiles and wall shear stress distribution of laminar pulsating flow with dimensionlessangular frequency show the flow characteristics of the quasi-steady laminar flow in a curved duct. The developing region of laminar pulsatile flows in a square-sectional $180^{\circ}$ curved duct is extended to the curved duct angle of approximately $120^{\circ}$ under the present experimental condition.

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곡관덕트에서 난류진동유동의 전단응력분포와 압력분포 (Wall shear stress and Pressure Distributions of Developing Turbulent Oscillatory Flows in a Square sectional Curved Duct)

  • 이홍구;손현철;이행남;박길문
    • 대한기계학회:학술대회논문집
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    • 대한기계학회 2001년도 춘계학술대회논문집E
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    • pp.380-385
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    • 2001
  • In the present study, flow characteristics of turbulent oscillatory flow in a square-sectional $180^{\circ}$ curved duct are investigated experimentally. In order to measure wall shear stress and pressure distributions, experimental studies for air flow are conducted in a square-sectional $180^{\circ}$ curved duct by using the LDV system with the data acquisition and the processing system. The wall shear stress measuring point bend angle of the $150^{\circ}$ and pressure distribution of the inlet (${\phi}=0^{\circ}$) to the outlet (${\phi}=180^{\circ}$) at $10^{\circ}$ intervals of the duct. The results obtained from the experimentation are summarized as follows: A wall shear stress value in an inner wall is larger than that in an outer wall, except for the phase angle (${\omega}t/{\pi}/6$) of 3, because of the intensity of secondary flow. The pressure distributions are the largest in accelerating and decelerating regions at the bend angle(${\phi}$) of $90^{\circ}$ and pressure difference of inner and outer walls is the largest before and after the ${\phi}=90^{\circ}$.

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정사각형 단면을 갖는 90° 곡관의 층류유동 계산 (Numerical calculation of Laminar flow in a Square Duct of 90° Bend)

  • 김형태;김정중
    • 한국전산유체공학회지
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    • 제2권1호
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    • pp.1-7
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    • 1997
  • A FA-FD hybrid method, developed for solving three-dimensional incompressible Navier-Stokes equations, is applied to calculate three-dimensional laminar flows through a square duct with a 90° bend. The method discretizes the convective terms in the primary flow direction with 3rd-order upwind finite-differences and the convective and diffusive terms in the transverse directions with the two-dimensional finite analytic method. The non-staggered grid system is used and the pressure-velocity coupling is achieved by a global iteration procedure based on the PISO algorithm. Detailed comparisons between the computed solutions and the available experimental data are given mainly for the velocity distributions at cross-sections in a 90° bend of a square duct with both fully developed and developing entry flows. Although the computational result shows generally a good agreement with the experimental data, there are some significant discrepancies underlining the necessity of more accurate numerical methods as well as reliable experimental data for their validation.

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정방형 공기덕트 내부의 유동특성에 원심력이 미치는 영향에 관한 연구 (A Study on the Influence of Centrifugal Force for Flow Characteristics in Square-sectional Air Duct)

  • 봉태근;조대환
    • 해양환경안전학회지
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    • 제18권5호
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    • pp.455-460
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    • 2012
  • 이 연구에서는 정사각 단면을 갖는 덕트 내부에 원심력의 영향을 받는 유동의 천이특성을 실험 및 수치적으로 규명하였다. 실험적 연구로서 레이저도플러 속도계를 이용하여 축방향속도를 측정하였고, 상용소프트웨어인 플루언트를 이용한 전산유체 시뮬레이션으로 천이특성을 고찰하였다. 유동의 발달은 딘수와 굽힘각에 의존한다는 사실을 알 수 있었으며 덕트의 중앙에서의 속도분포는 원심력 때문에 내외벽보다 낮은 값을 나타내었다.

격자 볼츠만 방법을 이용한 덕트 내 쌍둥이 직렬배열 사각 실린더에 의한 Aeolian 순음소음 고찰 (Investigation Into Aeolian Tone Noise by Twin Tandem Square Cylinders in duct Using Lattice Boltzmann Method)

  • 이송준;정철웅
    • 한국소음진동공학회논문집
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    • 제24권12호
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    • pp.962-968
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    • 2014
  • The lattice Boltzmann method(LBM) has attracted attention as an alternative numerical algorithm for solving fluid mechanics since the end of the 90's. In these days, its intrinsic unsteadiness and rapid increase in computing power make the LBM be more applicable for computing flow-induced noise as well as fluid dynamics. The lattice Boltzmann method is a weakly compressible scheme, so we can get information about both aerodynamics and aeroacoustics from single simulation. In this paper, numerical analysis on Aeolian tone noise generated by tandem-twin square cylinders in duct is performed using the LBM. For simplicity, laminar two-dimensional fluid models are used. To verify the validity and accuracy of the current numerical techniques, numerical results for the laminar duct and the cylinder flows are compared with the analytical solution and the measurement, respectively. Then, aerodynamic noise of the twin tandem square cylinders is investigated. It is shown that the aerodynamic noise from the twin tandem square cylinders can be reduced by controlling the distance between the cylinders.

4각 안내덕트 루프형상에 의한 난류특성변화 수치해석 (A Numerical Study of the Turbulent Flow Characteristics in the Inlet Transition Square Duct Based on Roof Configuration)

  • 유근종;최훈기;최기림;신병주
    • 대한기계학회논문집B
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    • 제33권7호
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    • pp.541-551
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    • 2009
  • Configuration of the inlet transition square duct (hereinafter referred to as "transition duct") for heat recovery steam generator (hereinafter referred to as "HRSG") in combined cycle power plant is limited by the construction type of HRSG and plant site condition. The main purpose of the present study is to analyze the effect of a variation in turbulent flow pattern by roof slop angle change of transition duct for horizontal HRSG, which is influencing heat flux in heat transfer structure to the finned tube bank. In this study, a computational fluid dynamics(CFD) is applied to predict turbulent flow pattern and comparisons are made to 1/12th scale cold model test data for verification. Re-normalization group theory (RNG) based k-$\epsilon$ turbulent model, which improves the accuracy for rapidly strained flow and swirling flow in comparison with standard k-$\epsilon$ model, is used for the results cited in this study. To reduce the amount of computer resources required for modeling the finned tube bank, a porous media model is used.

LDV에 의한 곡관덕트에서 난류맥동유동의 유동특성에 관한 실험적 연구 (An Experimental Study on Flow Characteristics of Turbulent Pulsating Flow in a Curved Duct by Using LDV)

  • 이홍구;손현철;이행남;박길문
    • 대한기계학회논문집B
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    • 제25권11호
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    • pp.1561-1568
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    • 2001
  • In the present study, flow characteristics of turbulent pulsating flow in a square-sectional 180$^{\circ}$curved duct were experimentally investigated. The experimental study for air flows in a curved duct are carried out to measure axial velocity profiles, wall shear stress distributions and entrance length in a square-sectional 180$^{\circ}$curved duct by using the Laser Doppler Velocimeter(LDV) system and the data acquisition. Velocity profiles are obtained using the Rotating Machinery Resolver(RMR)and PHASE software in case of turbulent pulsating flow. Finally, it was plotted by the ORIGIN software. The experiment was conducted in seven sections from the inlet (ø = 0$^{\circ}$) to the outlet (ø=l80$^{\circ}$) at 3 0$^{\circ}$intervals of the duct.