• Title/Summary/Keyword: Cavity Wall

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Numerical Analysis of the High-Subsonic Cavity Flows over a Curved Wall (곡면 벽을 지나는 고아음속 공동 유동에 관한 수치해석적 연구)

  • Ye, A Ran;Das, Rajarshi;Kim, Heuy Dong
    • Journal of the Korean Society of Propulsion Engineers
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    • v.20 no.1
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    • pp.1-7
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    • 2016
  • Most of the work has been done till now focused on flows over wall mounted cavities in a straight wall where the incoming flow is uniform. However, the investigation on such kind of flow over a cavity mounted on the curved walls has been seldom reported in the existing literatures. In the present study, the numerical analysis was performed to investigate the cavity flow mounted on the curved walls. The effects of wall shape, the curvature radius and the flow Mach number, were investigated for high-subsonic flows. The results show that the static pressure of cavity floor increases as the L/R increases. This effect is found to be more significant when the flow Mach number is higher. The cavity drag for the curved walls are higher as compared with that of straight wall.

A Study of Solar heat removal Impact with Air-Vent Wall (통기벽체적용 건물에서의 일사열 제거효과 검토)

  • Kim, Sang-Jin;Kum, Jong-Soo;Choi, Kwang-Hwan;Shin, Byong-Hwan;Chung, Yong-Hyun
    • Journal of the Korean Solar Energy Society
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    • v.24 no.2
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    • pp.25-31
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    • 2004
  • Ventilation through air vent system in a building envelope is expected to be an effective measure to release solar radiation. An external surface of a wall absorbs solar radiation and transfers it to the air in the cavity. The warmed air gets buoyant force. So when openings are provided at the top and bottom of the cavity, the warmed air is released through the top opening and cooler outside air replaces the space in the cavity. This reduces the further heat transmission into the built environment. This natural ventilation effect seems to be steady and strong. So because of the cavity and the openings, the cooling load reduction by natural ventilation is believed to be considerable.

Numerical Simulation Study on Supersonic Combustion using the Cavity (공동을 이용한 초음속 연소의 수치적 연구)

  • Jeong, Eun-Ju;Jeung, In-Seuck
    • 한국연소학회:학술대회논문집
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    • 2005.10a
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    • pp.255-260
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    • 2005
  • To achieve efficient combustion within a manageable length, a successful fuel injection scheme must provide rapid mixing between the fuel and airstreams. The aim of the present numerical research is to investigate the flame holding and combustion enhancement. Additional fuel into the cavity prevents shear flow impingement on the trailing edge of the cavity. The high temperature freestream flow mixes with the cold hydrogen fuel that is injected into the cavity and raises the fuel temperature remarkably and become to start combustion. The high pressure in the cavity due to the cavity structure and combustion leads the hydrogen fuel to upstream. The shock in the cavity to be generated by the fuel injection joins together and reflects off the ceiling wall. This makes high pressure and low mach number region and makes a small recirculation in this region. This high stagnation temperature is nearly recovered in the shear layer in front of the cavity and leads to start combustion. In the downstream of the cavity, the wall pressure drops significantly. This means that the combustion phenomenon is diminished. Because fuel lumps at the trailing edge of the cavity then it spreads after the cavity so, in this region there is a strong expansion.

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Two-Dimensional Laminar Natural Convection Heat Transfer with Surface Radiation in a Cavity (캐비티내에서 표면복사를 고려한 2차원 층류 자연대류 열전달)

  • Park, H.Y.;Park, K.W.;Han, C.H.
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.4 no.3
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    • pp.217-232
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    • 1992
  • A Numerical study on two-dimensional laminar natural convection with and without surface radiation in fully or partially open square cavity was performed. The cavity has one vertical heated wall facing a vertical opening and two horizontal insulated walls. The pressure boundary condition was applied to the opening instead of the velocity boundary condition. The results of this study showed that the increase of partition length decreased the convective and the radiative Nusselt numbers. It was also found that the increase of wall emissivity decreased the convective Nusselt numbers but increased the radiative Nusselt numbers.

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Rotordynamic Analysis for Stepped-Labyrinth Gas Seals Using Moodys Friction-Factor Model

  • Ha, Tae-Woong
    • Journal of Mechanical Science and Technology
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    • v.15 no.9
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    • pp.1217-1225
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    • 2001
  • The governing equations are derived for the analysis of a stepped labyrinth gas seal generally used in high performance compressors, gas turbines, and steam turbines. The bulk-flow is assumed for a single cavity control volume set up in a stepped labyrinth cavity and the flow is assumed to be completely turbulent in the circumferential direction. The Moodys wall-friction-factor model is used for the calculation of wall shear stresses in the single cavity control volume. For the reaction force developed by the stepped labyrinth gas seal, linearized zeroth-order and first-order perturbation equations are developed for small motion about a centered position. Integration of the resultant first-order pressure distribution along and around the seal defines the rotordynamic coefficients of the stepped labyrinth gas seal. The resulting leakage and rotordynamic characteristics of the stepped labyrinth gas seal are presented and compared with Scharrers theoretical analysis using Blasius wall-friction-factor model. The present analysis shows a good qualitative agreement of leakage characteristics with Scharrers analysis, but underpredicts by about 20%. For the rotordynamic coefficients, the present analysis generally yields smaller predictied values compared with Scharrers analysis.

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PIV Analysis of Cubic Channel Cavity Flow (입방형 채널 캐비티 유동의 PIV 해석)

  • 조대환;김진구;이영호
    • Journal of Advanced Marine Engineering and Technology
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    • v.21 no.5
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    • pp.557-563
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    • 1997
  • The unsteady flow in three-dimensional cubic cavity with narrow channel at upper region is investigated experimentally for three kinds of Reynolds number, 1*10/sup 4/, 3*10/sup 4/ and 5*10/sup 4/ based on the cavity width and cavity inlet mean flow velocity. Instant velocity vectors are obtained simultaneously at whole field by PIV(Particle Image Velocimetry). Wall pressure distributions are estimated using Poisson equation from the velocity data. Results of PIV reveal that severe unsteady flow fluctuation within the cavity are remarkable at all Reynolds numbers and sheared mixing layer phenomena are also found at the region where inlet driving flow is collided with the clock-wise rotating main primary vortex. Instant velocity profiles reveal that deformed forced vortex formation is observed throughout the entire region and spanwise kinetic energy migration is conspicuous.

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Heat Transfer Characteristics on the Cavity with One Heat Source (하나의 열원을 가지는 캐비티 내의 열전달 특성)

  • 이용훈;배강열;정한식;정효민;이상철
    • Journal of Advanced Marine Engineering and Technology
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    • v.28 no.1
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    • pp.56-64
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    • 2004
  • A numerical study have been performed on a cavity with one heat source by the open ratio and tilt angle. The goal of this study is to get the information for designing a solar collector absorber. semi-conductor equipment and block heater and so on. The parameters for this study is the various open ratio. and tilt angle of the cavity and Rayleigh numbers The finite volume method with SIMPLE computational algorithm are used and calculated the heat transfer in the cavity. As a result, the heat trans(or was promoted by increase of Rayliegh numbers and open ratios But, the heat transfer was not promted at lower wall of cavity because the flow pattern are very small at lower space in the cavity(Or=0.1) As the Rayleigh number is increased the mean nusselt numbers are increased at inside wall.

A CONFOCAL LASER SCANNING MICROSCOPIC STUDY ON THE INTERFACE BETWEEN TOOTH COLORED RESTORATIVE MATERIALS AND DENTIN (공초점레이저주사현미경을 이용한 심미수복재와 상아질의 접착계면에 관한 연구)

  • Park, Byung-Chul;Cho, Young-Gon;Moon, Joo-Hoon
    • Restorative Dentistry and Endodontics
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    • v.25 no.3
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    • pp.313-320
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    • 2000
  • The purpose of this study was to evaluate on the interfacial morphology between dentin and restorative materials. In this in vitro study, the cavity wall restorated with 3 different kinds of tooth colored restorative materials [resin-modified Glass Ionomer cement (Fuji II LC), composite resin (Z-100), compomer (Dyract)]. The thirty extracted human molar teeth without caries and/or restorations are used. The experimental teeth were randomly divided into three groups of ten teeth each. In each group, Wedge shaped cavities (width: 3mm, length: 2mm, depth: 1.5mm) were prepared at the cementoenamel junction on buccal and lingual surfaces. The adhesive of composite resin were mixed with rhodamine B. Primer of composite resin, Prime & Bond 2.1 of Dyract and liquid of Fuji II LC were mixed with fluorescein. In group 1, the cavity wall was treatment with dentin conditioner, and then restorated with Fuji II LC. In group 2, the cavity wall was treatment with Prime & Bond 2.1 and then restorated with Dyract. In group 3, the cavity wall was etching with 10% maleic acid, applied with primer and bonding agent and then restorated with Z-100. The interface between dentin and restorative materials was observed by fluoresence imaging with a confocal laser scanning microscope. The results were as follows : 1. In Glass ionomer group, adaptation of resin modified Glass-ionomer restoration against cavity wall is tight, but the crack formed inside of restoration were observed. 2. In Dyract group, the penetration of resin tag is shorter and the width of hybrid layer is narrower than composite resin group. 3. In Z-100 group, primer penetrated deeply through dentinal tubule. Also bonding agent was penetrated along the primer, but the penetration length is shorter than primer part, and in 3-D image, the resin tag is conical shape and lateral branch is observed.

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LARGE EDDY SIMULATION OF THE COMPRESSIBLE FLOW OVER A CAVITY WITH HIGH ASPECT RATIO

  • Oh Keon Je
    • Journal of computational fluids engineering
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    • v.9 no.1
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    • pp.1-9
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    • 2004
  • Large eddy simulation is used to investigate the compressible flow over a cavity with high aspect ratio. The sub-grid scale stresses are modeled using the dynamic model. The compressible Navier-Stokes equations are solved with the sixth order accurate compact finite difference scheme in the space and the 4th order Runge-Kutta scheme in the time. The buffer Bone techniques are used for non-reflecting boundary conditions. The results show the shear layer oscillation over the cavity. The votical disturbances, the roll-up of vorticity, and impingement and scattering of vorticity at the downstream cavity edge can be seen in the shear layer. Several peaks for the resonant frequencies are found in the spectra of the vertical velocity at the center-line. The most energetic Peak near the downstream edge is different from that at the center part of the cavity The pressure has its minimum value in the vortex core inside the cavity, and becomes very high at the downstream face of the cavity. The variation of the model coefficient predicted by the dynamic model is quite large between 0 and 0.3. The model coefficient increases in the stream-wise evolution of the shear layer and sharply decreases near the wall due to the wall effect.

지하공동 모델의 전기비저항 특성에 관한 실험적 연구

  • Park, Gap-Jin;Kim, Hyeon-Su;Kim, Hyeon-Seung;Song, Yeong-Su
    • 한국지구물리탐사학회:학술대회논문집
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    • 2009.10a
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    • pp.93-98
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    • 2009
  • Comprehension of physical properties distribution of underground cavity must be made primarily to show the clear image of the state of the cavity. A physical scale model experiment is executed assuming that underground cavity in filled with air or water of different ratio. The state of cavity wall is considered wet. Cavity model is made of agar. As a experimental result, even if the cavity wall is wet, high air and water ratio cavity shows high anomaly.

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