• Journal of Advanced Marine Engineering and Technology
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• 제25권1호
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• pp.131-138
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• 2001

In this paper, an experimental investigation of characteristics of developing turbulent steady flows in a square-sectional $180^{\circ}$curved duct is presented. The experimental study using air in a square-sectional $180^{\circ}$ curved duct carryed out to measure axials direction velocity and wall shear stress distrbutions by using Laser Dopper Velocimeter(LDV) system with data acquistion and processing the system of FIND6260 softwere at 7 sections from the inlet($\phi=0^{\circ}$) to the outlet($\phi=180^{\circ}$) in $301^{\circ}$ intervals of a curved duct.

• 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.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2012년도 춘계학술대회 논문집
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• pp.1061-1062
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• 2012

• 한국마린엔지니어링학회:학술대회논문집
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• 한국마린엔지니어링학회 2000년도 춘계학술대회 논문집(Proceeding of the KOSME 2000 Spring Annual Meeting)
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• pp.127-133
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• 2000

In the present study flow characteristics of turbulent pulsating flow in a square-sectional 180。 curved duct are investigated experimentally. in order to measure axial velocity and secondary flow 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 of the Rotating Machinery Resolver (RMR) and the PHASE software. The experiment is conducted on seven sections form the inlet(${\phi}=180^{\circ}$) at $30^{\circ}$ intervals of the duct. The results obtained from the experimentation are summarized as follows : In the axial 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 any change in axial velocity distribution along the phase. The secondary flow of turbulent pulsating flow has a positive value at the vend angle of $150^{\circ}$ without regard to 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.

• 한국산학기술학회논문지
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• 제17권10호
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• pp.618-627
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• 2016

본 연구는 정사각형 단면 $180^{\circ}$ 곡관 내의 유동특성을 파악하기 위해 RSM 난류모델을 이용하여 작동유체, 입구의 공기속도, 관내의 표면조도, 곡률반경 및 수력직경 등의 다양한 유동인자를 변경하여 각도 위치별 속도분포특성을 수치해석을 통하여 고찰하였다. CFD 해석시 경계조건은 공기와 물의 입구온도를 288 K, 293 K로 설정하였고, 입구의 공기속도, 관내의 표면조도, 곡률반경 및 수력직경은 각각 3~15 m/s, 0~0.001 mm, 2.5~4.5D, 70~100 mm로 적용하여 해석을 수행하였다. 그 결과를 정리하면, 작동유체의 유동특성은 유체의 점성력 차이로 속도분포가 크게 달라짐을 알 수 있었고, 곡관부 내에서의 최대 속도프로파일은 $90^{\circ}$ 단면위치에서 X/D=0.8 영역으로 나타났으며, $180^{\circ}$ 단면위치에서는 Y/D=0.8 영역으로 나타났다. 그리고 관내의 표면조도가 낮고, 곡률반경이 클수록 속도변화율은 크게 변하여 나타냈다. 또한 곡관후류의 직관부에서 유동편차가 안정화되는 직관거리는 L/D=30 영역에서 나타내어 유량 계측시 유효한 측정위치로 잘 제시할 수 있었으며, 수력직경에 따라 곡관후류 직관부의 표준편차특성은 동일한 유속일 때 최소의 편차영역은 대체로 직관거리 L/D=15~30 범위로 나타났다.

• 대한기계학회논문집
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• 제12권3호
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• pp.607-621
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• 1988

본 연구에서는 미세격자구역에서 속도에 관한 모든 운송방정식(transport equation)과 압력방정식을 푸는 완전미세격자법을 채택하였고 거친 격자구역에서는 K, $\varepsilon$ 방정식모델과 Boussinesq의 난류모델로 과점성계수를 구하는 방법 대신 레이놀 즈응력을 대수식으로 직접 구하는 대수응력모델(algebraic stress model, ASM)을 사용하여 해석하였다.

• 설비공학논문집
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• 제17권7호
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• pp.635-641
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• 2005

This study experimented to understand the effects of transporting ice slurry through elbow and inclined tube. And at this experiment it used propylene glycol-water solution and a diameter of about 2mm ice particle. The experiments were carried out under various conditions, with velocity of water solution at the entry ranging from 1.0 to 3.5 w/s and elbows and inclined tubes of 4 kinds angle with $30^{\circ},\;45^{\circ},\;90^{\circ}\;and\;180^{\circ}$. The pressure drop between the tube entry and exit were measured. According to angle of bending, the highest pressure drop was measured at $30^{\circ}$ elbow and the lowest pressure drop was measured at $90^{\circ}$ elbow, and there are only a little differences of pressure drop between $45^{\circ}$ elbow and $180^{\circ}$ elbow. According to angle of inclined tube, the highest pressure drop was measured at $90^{\circ}$ inclined tube and the pressure drop at $45^{\circ},\;30^{\circ},\;180^{\circ}$ inclined tubes were lower successively. The lowest pressure drop in elbows and inclined tubes was measured at velocity of $2.0\~2.5$ m/s and concentration of $10\;wt\%$.

• 대한기계학회논문집B
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• 제30권10호
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• pp.966-972
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• 2006

A numerical simulation is performed fur developing turbulent flow in a strongly curved 180 deg pipe and its downstream tangent by a new solution code(PowerCFD) which adopts an unstructured cell-centered method. The governing equations are discretized as the full elliptic from of the equations of motion. Three typical two-equation turbulence models of low-Reynolds-number form are used to approximate the turbulent stress field. Solutions fur both streamwise and circumferential velocity components are compared with the experimental data by Azzola et at.(1986). The ${\kappa}-{\omega}$ model by Wilcox(1988) is found to give better prediction performance than the other two. Predicted secondary velocities and streamwise velocity component contours at sequential longitudinal stations are also presented in order to enable a detailed description of the complete flow. It is also found that, in the bend both mean streamwise and secondary velocities never achieve a fully-developed state and the code is capable of producing very well the complex nature of steady flow in a strongly curved pipe.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2007년도 동계학술발표대회 논문집
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• pp.558-563
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• 2007

Detached Eddy Simulation(DES) is performed for turbulent flow of the $270^{\circ}$ bend at a Reynolds number of 56,690. A Fine grid generation is used near a wall in order to satisfy the wall boundary condition of y+<1. Turbulence models adopted for DES and Reynolds Average Navier Stokes(RANS) simulation are SST(Shear Stress Transfort) model. Solutions for both streamwise and circumferential velocity components are compared with the experimental data by Lee for $270^{\circ}$ bend and by Chang for $180^{\circ}$ bend.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2002년도 학술대회지
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• pp.521-524
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• 2002

In the present study, kinetic energy of laminar steady flow in the exit region connected to the square-sectional $180^{\circ}$curved duct was investigated experimentally. The experimental study for air flows was conducted to measure kinetic energy distributions by using the Particle Image Velocimetry(PIV) system with the data acquisition and processing system of Cactus 2000 software. The results obtained from experimental studies are summarized as follows : (1) The critical Reynolds number for a change from laminar steady flow to transitional steadt flow was about 1910, in the 50 region of dimensionless axial position (x/Dh) whirh was considered as a fully developed flow region. (2) Maximum kinetic energy of laminar steady flow was gradually increased as the Reynolds number increased.