• Title/Summary/Keyword: Flow Structure

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AIR ENTRAINMENT AND ENERGY DISSIPATION AT STEPPED DROP STRUCTURE

  • Kim Jin Hong
    • Water Engineering Research
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    • v.5 no.4
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    • pp.195-206
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    • 2004
  • This paper deals with oxygen transfer by air entrainment and energy dissipations by flow characteristics at the stepped drop structure. Nappe flow occurred at low flow rates and for relatively large step height. Dominant flow features included an air pocket, a free-falling nappe impact and a subsequent hydraulic jump on the downstream step. Most energy was dissipated by nappe impact and in the downstream hydraulic jump. Skimming flow occurred at larger flow rates with formation of recirculating vortices between the main flow and the step comers. Oxygen transfer was found to be proportional to the flow velocity, the flow discharge, and the Froude number. It was more related to the flow discharge than to the Froude number. Energy dissipations in both cases of nappe flow and skimming flow were proportional to the step height and were inversely proportional to the overflow depth, and were not proportional to the step slope. The stepped drop structure was found to be efficient for water treatment associated with substantial air entrainment and for energy dissipation.

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Analysis of Flow Around Multi-Circular Cylinders Using a Numerical Model (수치모형을 이용한 다원주 주위의 유동 해석)

  • Lee Sang-Hwa;Park Jung-Ho
    • Journal of Ocean Engineering and Technology
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    • v.20 no.2 s.69
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    • pp.29-35
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    • 2006
  • The flow patterns around multi-circular cylinders are studies, in order to obtain a global view on the structure of wave control and circulation of sea flow in coastal region. The flow force depends upon the vortex shedding exerted on the structure, especially how the vortex shedding affects the erosion when the structure sets on the sand bottom. Therefore, it is necessary that the flow pattern be hocked. In order to simulate the flow around multi-circular cylinders, the CFX and FLUENT of the computational fluid dynamics (CFD) program were used and compared with the experimental results of the flow visualization installation. The phenomena of flow around the multi-cylinders will be applied to fundamental data for predicting the flow force acting against the structure, erosion and sedimentation around cylinders in arrangement.

Air Flow Sensor with Corrugation Structure for Low Air Velocity Detection (주름구조를 적용한 저속 유속 센서)

  • Choi, Dae-Keun;Lee, Sang-Hoon
    • Journal of Sensor Science and Technology
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    • v.20 no.6
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    • pp.393-399
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    • 2011
  • In this paper, we designed and fabricated the novel air flow sensor using air drag force, which can be applied to the low air flow detection. To measure the low air flow, we should enlarge the air drag force and the output signal at the given air flow. The paddle structure is applied to the device, and the device is vertically located against the air flow to magnify the air drag force. We also adapt the corrugation structure to improve the output signals on the given air velocity. The device structure is made up of the silicon nitride layer and the output signal is measured with the piezoresistive layer. The output signals from the corrugated device show the better measurement sensitivity and the response time than that of flat one. The repeated measurement also shows the stabilized signals.

A Study on Vibration Power Flow of Truss Core Type Sandwich Plate Structure (트러스코어형 샌드위치 판구조물의 진동파워흐름에 관한 연구)

  • 구경민;김동영;홍도관;박일수;안찬우;한근조
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2002.10a
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    • pp.863-866
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    • 2002
  • In this study, we tried to grasp the characteristic of vibration power flow for the truss core type sandwich plate structure. As the result of the finite element analysis, this paper shows that the vibration power flow characteristic of truss core type sandwich plate structure is understood and the vibration power flow of upper plate according to the mode shape of structure is various. Also it presents the vibration power flow is affected by reinforced structure.

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ORIGINS OF THE FLOW AND MAGNETIC STRUCTURE INVOLVED IN THE FORMATION AND ERUPTION OF A SOLAR PROMINENCE

  • Magara, Tetsuya
    • Journal of The Korean Astronomical Society
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    • v.54 no.5
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    • pp.157-170
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    • 2021
  • We investigate flow and magnetic structure of a solar prominence with a focus on how the magnetic field originally determined by subsurface dynamics gives rise to the structure. We perform a magnetohydrodynamic simulation that reproduces the self-consistent evolution of a flow and the magnetic field passing freely through the solar surface. By analyzing Lagrangian displacements of magnetized plasma elements, we demonstrate the flow structure that is naturally incorporated to the magnetic structure of the prominence formed via dynamic interaction between the flow and the magnetic field. Our results explain a diverging flow on a U-loop, a counterclockwise downdraft along a rotating field line, acceleration and deceleration of a downflow along an S-loop, and partial emergence of a W-loop, which may play key roles in determining structural properties of the prominence.

Visualization of cross-sectional two-phase flow structure during in-tube condensation (관내 응축 시 2상유동 단면구조의 가시화)

  • Pusey, Andree;Kim, Hyungdae
    • Journal of the Korean Society of Visualization
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    • v.14 no.2
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    • pp.18-24
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    • 2016
  • This paper presents an experimental investigation to visualize cross-sectional two-phase flow structure and identify liquid-gas interface for condensation of steam at a low mass flux in a slightly inclined tube using the axial-viewing technique, which permits to look directly into flow during condensation of steam. In this technique, two-phase flow is viewed along the axis of a pipe by locating a high-speed video camera in front of a viewer that is fitted at the outlet of the pipe. A short section of the pipe is illuminated and is recorded through the viewer, which is kept free of liquid by mildly introducing air. Experiments were conducted in a pipe of 19.05 mm in inner diameter at atmospheric pressure. Cross-sectional two-phase flow structure is obtained at a steam mass flux of $2.62kg/m^2s$ as a function of steam quality in the range from 0.5 to 0.9. The results show that stratified-wavy flow is a unique flow pattern observed in the scope of the present study. Condensate film thickness, stratification angle and void fraction were measured from the obtained flow structure images. Finally, heat transfer coefficient was calculated using the measurement data and discussed in comparison with existing correlations.

The Analysis of Flow Distribution in the Core Channel of the HANARO Flow Simulated Test Facility (하나로 유동모의 시험설비의 노심채널 유동분포 해석)

  • Park Y C.;Kim K. R.
    • 한국전산유체공학회:학술대회논문집
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    • 2004.10a
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    • pp.151-154
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    • 2004
  • The HANARO, a multi-purpose research reactor of 30 MWth open-tank-in-pool type, has been under normal operation since its initial criticality in February, 1995. Many experiments should be safely performed to activate the utilization of the HANARO. A flow simulated test facility has been developed for the verification of structural integrity of those experimental facilities prior to loading In the HANARO. This test facility is composed of three major parts; a half-core structure assembly, flow circulation system and support system. The half-core structure assembly is composed of plenum, grid plate, core channel with flow tubes, chimney and dummy pool. The flow channels are to be filled with flow orifices to simulate similar flow characteristics to the HANARO. This paper describes an analysis of the flow distribution of the cote channel and compares with the test results. As results, the analysis showed similar flow characteristics compared with those in the test results.

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A Flow/structure Interaction Analysis for the Design of Medical CSF-Flow Control Valve (의료용 CSF 제어 밸브 설계를 위한 유동/구조 상호작용 해석)

  • Won C. S.;Hur N.;Lee C. S.
    • Journal of computational fluids engineering
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    • v.6 no.1
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    • pp.40-46
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    • 2001
  • Pressure-flow control characteristics of a commercially available cerebrospinal flow(CSF) control shunt valve was studied using flow/structure interaction analyses. Pre-stress of the valve diaphragm(membrane) was accounted for the simulation of an actual valve. The present results were in good agreement with the valve specification listed in the commercially available CSF control valve. The flow/structure interaction analysis of the present study can be effectively used to design a variety of CSF control shunt valves.

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An Experimental Study on Flow Structure inside a Display Cooler Using PIV Techniques (PIV기법을 이용한 전시용 냉장기의 내부 유동장 측정)

  • Park, Cheol-Woo;Baek, In-Je
    • Journal of the Korean Society of Visualization
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    • v.5 no.2
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    • pp.48-55
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    • 2007
  • Flow structure inside a refrigerating compartment of a scale-down display cooler model was investigated experimentally by using PIV (particle image velocimetry) method, a reliable velocity field measurement technique, in the present study. In addition, we also carried out flow visualization regarding flow structure and particle movement inside a display cooler by using a tracer method. As a result, the mean velocity field measurement shows a large scale vortical flow structure inside a refrigerating compartment due to strong entrainment flow, going through a base plate open gaps.

A Study of the Relations among English Thinking Structure, Pre-English Skill, Self-Efficacy in English, Flow and Learning Effect (e-Learning에서 영어식 사고구조, 사전 영어능력, 영어자기효능감의 몰입을 통한 학습효과)

  • Kang, Jung-Hwa
    • Journal of Digital Convergence
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    • v.8 no.4
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    • pp.165-176
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    • 2010
  • The aim of this study is to determine the relationship between variables affecting learning effect and flow experience on an e-Learning English program. There are 4 independent variables; English thinking structure, self-efficacy in English and flow. The results are as follows: Firstly, there is statistically significant positive correlation between each variable of English thinking structure, pre English skill, self-efficacy in English, flow and learning effect. Secondly, it appeared that flow was affected by all three variables of English thinking structure, pre-English skill and self-efficacy in English. Also flow experience affected learning improvement. Finally, it is verified that there is a mediating effect of flow experience on the relation of self-efficacy in English and learning effect.

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