• Title/Summary/Keyword: 난류유동특성

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Interaction Effects of Turbulent Flow and Chemical Reaction in a Swirl Combustor (스월연소기의 난류와 화학반응 간섭효과)

  • Sung, Hong-Gye;Kim, Jong-Chan;Yang, Vigor;Cha, Bong-Jun;Ahn, I-Ki
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2007.04a
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    • pp.71-74
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    • 2007
  • Large Eddy Simulation(LES) has been conducted to insight interaction effects of turbulent flow and chemical reaction of a lean-Premixed swirl combustor. The unsteady turbulent flame is carefully simulated so that the motion of flow and flame can be characterized in detail. Fuel lumps escaping from the primary combustion zone move downstream and consequently produce local hot spots conveying large vortical structures in the azimuthal direction. The correlation between pressure oscillation and unsteady heat release is examined by the spatial and temporal Rayleigh parameter.

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Flow Measurements on the Propeller Plane Using Fiber Optics LDV at Towing Tank (예인수조에서 Fiber Optics LDV를 이용한 프로펠러면에서의 유속측정)

  • J.E. Choi;H.W. Seo;K.S. Min
    • Journal of the Society of Naval Architects of Korea
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    • v.36 no.3
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    • pp.22-28
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    • 1999
  • Flow measurements on the propeller plane of a 180,000 TDW Bulk Carrier model are carried out using a 3D fiber optics LDV at a towing tank. Mean velocities are successfully obtained. The turbulence characteristics such as Reynolds stresses, skewnesses, and flatnesses, are also investigated. However, those turbulence characteristics may include some errors due to the characteristics of the towing-tank experiments.

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An experimental study on the thermal entrance lengths for viscoelastic polymer solutions in turbulent tube flow (점탄성 특성을 가진 폴리머용액의 난류유동 열적입구길이에 관한 실험적 연구)

  • 유상신;황태성;엄정섭
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.12 no.5
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    • pp.1189-1196
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    • 1988
  • Thermal entrance lengths of turbulent tube flow for viscoelastic polymer solutions are investigated experimentally in the recirculating flow system with tubes of inside diameters 8.5mm(L/D=710) and 10.3mm(L/D=1158), respectively. In the present system, the hydrodynamic and thermal boundary layers develop simultaneously from the beginning of the test section. To provide the boundary condition of constant heat flux at the wall, the test tubes are heated directly by electricity. The polymer solution used in the current study is 1000 wppm aqueous solution of polyacrylamide(Separan AP-273). The apparent viscosity of the polymer solutions circulating in the flow system are measured by the capillary tube viscometer at regular time intervals. Thermal entrance lengths vary due to the rate of degradation. The entrance lengths of degraded polymer solutions are about 500~600 times the diameter. However, the entrance lengths of fresh polymer solutions are greater than the lengths of the test tubes used in this study suggesting that thermal entrance lengths for viscoelastic polymer solutions are greater than 1100 tube times the diameters. Friction factor is almost insensitive to the degradation, but the heat transfer $j_{H}$-factor is affected seriously by degradation. Based on the present experimental data of fresh solutions a correlation for the heat transfer $j_{H}$-factor is presented.ted.

Computation of Four Quadrant Performance for a Marine Propeller in Open Water (박용 프로펠러의 4상한 단독성능 계산)

  • Hyoung-Tae Kim;Jeong-Jung Kim
    • Journal of the Society of Naval Architects of Korea
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    • v.38 no.4
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    • pp.1-10
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    • 2001
  • A numerical solution method of the incompressible Reynolds-Averaged Navier-Stokes equations is applied for calculating turbulent flows and performances of a marine propeller in open-water, four-quadrant conditions. Computed propeller flows of the model propeller P4381, for which the experimental data of the open-water performances exist, reveal complex viscous-flow characteristics including three-dimensional flow separations in various off-design conditions and also computed propeller thrusts and torques agree quite well with experimental data except some cases for which severe propeller cavitations occurred in the experiment.

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Flow Safety Assessment by CFD Analysis in One-touch Insertion Type Pipe Joint for Refrigerant (CFD 해석을 이용한 냉매용 원터치 삽입식 파이프 조인트의 안전성 평가)

  • Kim Eun-Yonung;Park Dong-sam;Kim, Hong-Yong
    • Proceedings of the Korean Society of Disaster Information Conference
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    • 2022.10a
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    • pp.303-304
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    • 2022
  • 파이프는 기계, 전자, 전기, 플랜트 등 많은 산업 분야에서 응용기기로 널리 사용되고 있으며, 소방, 화학 등 안전 관련 분야에서도 널리 사용되고 있다. 제품의 다양화에 따라 배관 분야에서도 기술의 중요성이 높아지고 있다. 특히 기존 동관을 스테인리스강으로 변경하는 경우 구조해석이나 유동 해석을 통해 안전성과 유동특성을 평가할 필요가 있다. 자체 개발한 일체형 인서트형 커넥터인 6.35 소켓 모델의 유동 안전성은 CFD 해석을 이용하여 유동유발진동(FIV)평가 과정의 4단계를 통해 진행하였다. 배관계 벽면에 작용하는 압력변동의 진폭은 3,780Pa이하의 수준으로 형성되며, 이는 냉매 배관의 운전압력이나 설계응력과 비교했을 때 매우 작은 수준의 압력으로, 난류에 의한 진동이 배관의 구조안전성에 미치는 영향은 미미한 수준인 것으로 나타났다.

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A Study on the Three-Dimensional Turbulent Flour Characteristics of a Small-sized Axial Fan at the Maximum Flowrate Region (최대유량역에서 소형 축류 홴의 3차원 난류유동 특성에 관한 연구)

  • Kim, J.K.
    • Journal of Power System Engineering
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    • v.4 no.3
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    • pp.25-33
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    • 2000
  • This study represents three-dimensional turbulent flow characteristics around an axial fan measured at the operating point ${\varphi}=0.32$, which is equivalent to the maximum flowrate region, by using three-dimensional fiber-optic type LDA system. This LDA system is composed of a 5 W Argon-ion laser, two optics in back-scatter mode, three BSA's, a PC, and a three-dimensional automatic traversing system. A kind of paraffin fog is used for laser particles in this study. Mean velocity profiles around an axial fan along the downstream radial distance show that the streamwise and the tangential components exist as a predominant velocity and have the maximum value at the radial distance ratio 0.8, while the radial component has a small scale distribution and its flow direction is inward except a part of blade tip. The turbulent intensity profiles show that the radial component exists the most greatly. And also the turbulent kinetic energy shows about 60% as a maximum value at the radial distance ratio 0.9. Moreover, the Reynolds shear stresses do not exist at upstream flow, but the streamwise and the radial components of them show about 20% as a maximum value at the radial distance ratio 0.9 at downstream flow.

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A Study on the Three Dimensional Statistical Turbulent Flow Characteristics Around a Small-Sized Axial Fan for Refrigerator (냉장고용 소형 축류홴의 통계학적 3차원 난류유동 특성에 관한 연구)

  • Kim, Jang-Gwon
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.25 no.6
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    • pp.819-828
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    • 2001
  • The operating point of a small-sized axial fan is strongly dependent upon the system resistance. Therefore, the turbulent flow characteristics around a small-sized axial fan may change significantly according to the operating point. This study represents three-dimensional turbulent flow characteristics around a small-sized axial fan measured at the ideal design point $\phi$=0.25, which is equivalent to the maximum total efficiency point, by using three dimensional fiber-optic type LDA system. This LDA system is composed of a 5 W Argon-ion laser, two optics in back-scatter mode, three BSAs, a PC, and a three-dimensional automatic traversing system. A kind of paraffin fluid is used to supply particles by means of fog generator. Mean velocity profiles downstream of a small-sized axial fan along the radial distance show that the streamwise and the tangential components exist in a predominant manner, while the radial component has a small scale distribution and shows the inflection which its flow direction is inward or outward. Moreover, the turbulent intensity profiles show that the radial component exists the most greatly among turbulent energies.

LDA Measurements on the Turbulent Flow Characteristics of a Small-Sized Axial Fan (소형 축류홴의 난류유동 특성치에 대한 LDA 측정)

  • Kim, Jang-Kweon
    • Proceedings of the KSME Conference
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    • 2001.11b
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    • pp.371-376
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    • 2001
  • The operating point of a small-sized axial fan for refrigerator is strongly dependent upon the system resistance. Therefore, the turbulent flow characteristics around a small-sized axial fan may change significantly according to the operating point. This study represents three-dimensional turbulent flow characteristics around a small-sized axial fan measured at the four operating points such as $\varphi=0.1$, 0.18, 0.25 and 0.32 by using fiber-optic type LDA system. This LDA system is composed of a 5 W Argon-ion laser, two optics in back-scatter mode, three BSA's, a PC, and a three-dimensional automatic traversing system. A kind of paraffin fluid is utilized for supplying particles by means of fog generator. Mean velocity profiles downstream of a small-sized axial fan along the radial distance show that both the streamwise and the tangential components exist predominantly in downstream except $\varphi=0.1$ and have a maximum value at the radial distance ratio of about 0.8, but the radial component, which its velocity is relatively small, is acting role that only turns flow direction to the outside or the central part of axial fan. Moreover, all of the velocity components downstream at $\varphi=0.1$ show much smaller than those upstream due to the static pressure rise at the low-flowrate region.

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Three-Dimensional Numerical Analysis of Surface Buoyant Jets (표층밀도분류의 3차원 수치해석)

  • 허재영
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.3 no.3
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    • pp.152-162
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    • 1991
  • A three-dimensional numerical model with free water surface was established to investigate flow characteristics of surface buoyant jets and river plumes. Turbulent shear stresses and turbulent buoyancy fluxes were expressed in terms of the eddy viscosities and diffusivities. Stable stratification effects due to density difference between discharged water and receiving ambient water were taken into with empirical formulae. Through a comparison of numerical results with published experimental data the validity of the model was shown and the optimal stratification functions was determined The three-dimensional spreading characteristics were examined and the effects of inlet densimetric Froude number, inlet aspect ratio and water surface elevation on the flow development were discussed.

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A Unified 3D Numerical Analysis of a Model Scramjet Engine with a Cavity Flame-Holder and Two Intake Side Walls (공동형 보염기를 갖는 모델 스크램제트 엔진의 흡입구 측면효과를 고려한 3차원 통합 유동해석)

  • Yeom, Hyo-Won;Kim, Sung-Jin;Sung, Hong-Gye;Kang, Sang-Hoon;Yang, Soo-Suk
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2009.11a
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    • pp.590-593
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    • 2009
  • To identify the detailed 3D flow characteristics of a model scramjet engine, a unified 3D numerical analysis was performed. The numerical domain of concern includes the entire flow path of the model scramjet engine extending from the intake to the nozzle exhaust. Turbulent models($k-{\omega}$ SST and low Reynolds number k-e with Sarkar model) were applied with comparison of experiment result. Intake side wall's effect on flow characteristics was analyzed in view points of flow quality at inlet duct and near the flame holder as well. The code is paralleled with multi-block feature using MPI(Massage Passing Interface) library to speed up the 3D calculation.

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