• Title/Summary/Keyword: surface flow

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Experimental Investigation on Separated Flows of Axial Flow Stator and Diagonal Flow Rotor

  • Kinoue, Yoichi;Shiomi, Norimasa;Setoguchi, Toshiaki;Jin, Yingzi
    • International Journal of Fluid Machinery and Systems
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    • v.2 no.3
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    • pp.223-231
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    • 2009
  • Experimental investigations were conducted for the internal flows of the axial flow stator and diagonal flow rotor. Corner separation near the hub surface and the suction surface of stator blade are mainly focused on. For the design flow rate, the values of the axial velocity and the total pressure at stator outlet decrease between near the suction surface and near the hub surface by the influence of corner wall. For the flow rate of 80-90% of the design flow rate, the corner separation of the stator between the suction surface and the hub surface is observed, which becomes widely spread for 80% of the design flow rate. At rotor outlet for 81% of the design flow rate, the low axial velocity region grows between near the suction surface of rotor and the casing surface because of the tip leakage flow of the rotor.

Study on the Fluid-Surface Characteristics by Using Flow Visualization and Numerical Simulation of Stokes Flow in a Cavity (3차원 캐버티 표면의 스톡스 유동 가시화 및 수치해석을 통한 표면 특성 연구)

  • Heo, Hyo-Weon;Lee, Heon-Deok;Jung, Won-Hyuk;Cho, Dong-Sik;Suh, Yong-Kweon
    • Journal of the Korean Society of Visualization
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    • v.9 no.3
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    • pp.44-50
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    • 2011
  • In this study, we propose a method for characterizing fluid-mechanical properties of a fluid surface, such as surface dilatational and shear viscosity, by matching the flow visualization and the numerical simulation for a Stokes flow in a three-dimensional cavity. The surface flow is driven by shear stress exerted on the free surface by an external gas flow. The external gas flow is simulated by using a commercial code, while the Stokes flow is calculated by an in-house code. We have found that the surface flow is very sensitive to the surface tension and other properties. The qualitative feature of the surface flow can be reproduced by the parameter tuning.

Study on the Stokes' Flow within a Three-Dimensional Cavity Considering Surface Characteristics (액체의 표면 특성을 고려한 3차원 캐버티 내부의 스톡스 유동 특성 연구)

  • Heo, Hyo-Weon;Jung, Won-Hyuk;Suh, Yong-Kweon
    • 한국전산유체공학회:학술대회논문집
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    • 2011.05a
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    • pp.382-386
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    • 2011
  • In this study, a CFD code is developed to perform simulation of the surface and internal flow of a three-dimensional rectangular cavity driven by an external gas flow. Investigated in this study are surface characteristic such as surface tension, surface dilational viscosity(or surface elasticity), and surface viscosity. Visualization of the surface of water is performed to compare with the numerical results obtained with the developed in-house code. We have found that the surface flow is very sensitive to the surface tension and other configurations. The surface flow velocity obtained from the numerical solution is lower than the experimental result.

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Flow Structure of the Wake behind an Elliptic Cylinder Close to a Free Surface

  • Daichin;Lee, Sang-Joon
    • Journal of Mechanical Science and Technology
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    • v.15 no.12
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    • pp.1784-1793
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    • 2001
  • The flow fields around an elliptic cylinder of axis ratio AR=2 adjacent to a free surface were investigated experimentally using a water channel. The main objective is to understand the effect of the free surface on the flow structure in the near-wake. The flow fields were measured by varying the depth of cylinder submergence, for each experimental condition, 350 velocity fields were measured using a single-frame PIV system and ensemble-averaged to obtain the spatial distribution of turbulent statics. For small submergence depths a large-scale eddy structure was observed in the near-wake, causing a reverse flow near the free surface, downstream of the cylinder. As the depth of cylinder submergence was increased, the flow speed in the gap region between the upper surface of the cylinder and the free surface increased and formed a substantial jet flow. The general flow structure of the elliptic cylinder is similar to previous results for a circular cylinder submerged near to a free surface. However, the width of the wake and the angle of downward deflection of the shear layer developed from the lower surface of the elliptic cylinder are smaller tan those for a circular cylinder.

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Analysis on the free surface flow induced by a pair of source-sink in Stokes flow (스톡스 유동장 내의 한 쌍의 소오스-싱크에 의한 자유표면 유동해석)

  • Jeong, Jae-Tack;Park, Jong-Sun
    • 한국전산유체공학회:학술대회논문집
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    • 2008.03b
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    • pp.304-307
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    • 2008
  • Two-dimensional Stokes flow due to the line source and line sink of same strength in semi-infinite flow region with free surface is analysed using complex variable theory and conformal mapping. Surface tension effects are included while gravity is neglected. From the results of analysis, flow pattern and free surface shape are obtained and velocity distribution on the free surface is determined with 2 independent parameters Ca (capillary number) and h (non-dimensionalized distance between source and sink). When the location of the sink is above the source, velocity on the free surface converges and a cusp occurs on the free surface for the value of Ca above some critical capillary number.

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TRANSIENT FLOW SIMULATION OF A MIXER WITH FREE SURFACE (자유표면을 고려한 교반기 내부의 비정상 유동해석)

  • Ahn, Ick-Jin;Song, Ae-Kyung;Hur, Nahm-Keon
    • Journal of computational fluids engineering
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    • v.11 no.4 s.35
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    • pp.9-13
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    • 2006
  • In the present study, a numerical analysis of transient mixer flow is performed considering free surface formation. The flow patterns and free surface shape in a mixers formed by flat paddle and pitched paddle impellers are predicted. In a flat paddle mixer, two flow circulation regions are formed due to strong radial flow, whereas one large circulation is formed in a pitched paddle mixer due to axial downward flow. These differences affect the free surface evolution and shape. It is seen from the results that a flat paddle mixer gives deeper free surface at center region than a pitched paddle mixer. The free surface of 8-blades-flat-paddle mixer is also simulated to compare with the available experimental and simulation results. The present computational results agree reasonably well with the experimental data.

Development of a Conjunctive Surface-Subsurface Flow Model for Use in Land Surface Models at a Large Scale: Part I. Model Description (대규모 육지수문모형에서 사용 가능한 지표면 및 지표하 연계 물흐름 모형의 개발: I. 모형설명)

  • Choi, Hyun-Il
    • Journal of the Korean Society of Hazard Mitigation
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    • v.8 no.2
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    • pp.59-63
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    • 2008
  • The surface runoff is one of the important components for the surface water balance. However, most Land Surface Models(LSMs), coupled to climate models at a large scale for the prediction and prevention of disasters caused by climate changes, simplistically estimate surface runoff from the soil water budget. Ignoring the role of surface flow depth on the infiltration rate causes errors in both surface and subsurface flow calculations. Therefore, for the comprehensive terrestrial water and energy cycle predictions in LSMs, a conjunctive surface-subsurface flow model at a large scale is developed by coupling a 1-D diffusion wave model for surface flow with the 3-D Volume Averaged Soil-moisture Transport(VAST) model for subsurface flow. This paper describes the new conjunctive surface-subsurface flow formulation developed for improvement of the prediction of surface runoff and spatial distribution of soil water by topography, along with basic schemes related to the terrestrial hydrologic system in Common Land Model(CLM), one of the state-of-the-art LSMs.

Numerical Investigation of Secondary Flow in 3 Pump Stages: Centrifugal Multistage/Mixed-flow Stage/ Axial-flow Stage (원심형, 사류형, 축류형 펌프단에서 살펴본 이차유동의 수치적 고찰)

  • Oh, Justin
    • 유체기계공업학회:학술대회논문집
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    • 2005.12a
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    • pp.359-364
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    • 2005
  • Centrifugal pump shows the strongest secondary flow. Wake is formed near pressure surface close to hub at impeller exit for centrifugal pump impeller. Pressure gradient drives secondary flow in the inducer region, while in the remaining region the following sources drive together: > Pressure gradient > Coriolis force Low-momentum fluid near suction surface hub moves toward pressure surface hub in mixed-flow pump impeller. Tip leakage vortex dominate secondary flow in axial-flow pump impeller. Tip leakage vortex dominate secondary flow in axial-flow in axial-flow pump impeller

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Oscillatory Thermocapillary Flow in Cylindrical Columns of High Prand시 Number Fluids

  • Lee, Kyu-Jung;Yasuhiro Kamotani;Simon Ostrach
    • Journal of Mechanical Science and Technology
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    • v.15 no.6
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    • pp.764-775
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    • 2001
  • Oscillartory thermocapillary flow of high Prandtl number fluids in the half-zone configuration is investigated. Based on experimental observations, one oscillation cycle consists of an active period where the surface flow is strong and the hot corner region is extended and a slow period where the opposite occurs. It is found that during oscillations the deformation of free surface plays an important role and a surface deformation parameter S correlates the experimental data well on the onset of oscillations. A scaling analysis is performed to analyze the basic steady flow in the parametric ranges of previous ground-based experiments and shows that the flow is viscous dominant and is mainly driven in the hot corner. The predicted scaling laws agree well with the numerical results. It is postulated that the oscillations are caused by a time lag between the surface and return flows. A deformation parameter S represents the response time of the return flow to the surface flow.

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An experimental Study of Heat Transfer of Rivulet Flow over an Inclined, Heated Surface (경사진 가열 평판을 흐르는 리뷸릿 유동의 열전달 특성에 관한 실험적 연구)

  • Kang, Chi-Suk;Kang, Byung-Ha
    • Proceedings of the SAREK Conference
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    • 2006.06a
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    • pp.156-161
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    • 2006
  • The rivulet is a narrow stream of liquid flowing down a solid surface. Heat transfer of rivulet flow over on inclined heated surface has been investigated experimentally. This problem is of particular interest in the understanding of fundamental mechanism on rivulet heat transfer as well as in the design of a regenerative evaporative cooler. The rivulet is seem to be meandering flow, single wide flat flow. and film flow as rivulet flow rate is increased. Even though the wetted surface area is increased with an increase in the rivulet flow rate, the absorbed heat transfer of rivulet flow from a heated surface strongly depends on the flow pattern of rivulet.

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