• Title/Summary/Keyword: cavity location

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Numerical Analysis of Supersonic Combustion Flows according to Fuel Injection Positions near the Cavity (공동주위 분사위치에 따른 초음속 연소 유동해석)

  • Jeong Eunju;Jeung In-Seuck
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • v.y2005m4
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    • pp.368-373
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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 mixing enhancement combustion phenomena according to fuel injector location near the cavity in supersonic flow. Fuel injector location changes the actual length to depth ratio of the cavity in the supersonic combustor. Therefore fuel injector location near the cavity effects different fuel/air mixing efficiency and combustion efficiency.

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Optimal Thermal Design of a Single Heat Source in a Cavity (Cavity내의 단일 열원에 대한 최적 열적설계)

  • Yae, Y.T.;Choo, H.L.;Kim, H.W.
    • Solar Energy
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    • v.19 no.1
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    • pp.77-86
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    • 1999
  • The optimal thermal design of a single heat source on one wall of a vertical open top cavity was studied experimentally. The temperature and flow fields in the cavity were visualized. The objectives of this study is to obtain the best location of the single heat source and to examine the effects of heat source protrusion, substrate thermal conductivity and cavity aspect ratio on the natural convection cooling due to a single heat source. As the results, the cooling effect for the copper substrate is superior to that of the epoxy-resin substrate and is improved with increasing cavity width. For the epoxy-resin substrate of lower conductivity, the protrusion of the heaters plays a role in decreasing the cooling effect. The best location was the mid-height of the substrate.

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Performance Analysis of Summertime Heat Transfer Characteristics of the Double Skin Window for Plant Factory (식물공장 이중창호의 하절기 열전달 성능 분석)

  • So, Jae-Hyun;Kim, Woo-Tae
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.24 no.4
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    • pp.351-357
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    • 2012
  • To reduce the summertime cooling load of a plant factory, a concept design was performed for the double skin window which utilizes the low temperature air from a ground coupled heat exchanger. The design parameters were selected as the number of cavity air inlet, the cavity thickness, the location of cavity air inlet, and the configuration of cavity air outlet. A parametric study was conducted in a systematic way to evaluate the heat transfer characteristics of the double skin window. As the number of cavity air inlet and the cavity thickness increase, the heat flux from outside air to indoor air was decreased. The effect of the location of cavity air inlet was not significant and the larger cavity air outlet area gave us relatively better heat blocking performance from outside hot air. This study demonstrated that it is possible to develop an improved double skin window by utilizing a ground coupled heat exchanger.

Numerical Simulation for Prediction of Existing Cavity Location on Explosion-Induced Building Collapse (폭발에 의한 건축물 붕괴 시 매몰공동 위치 예측에 관한 수치해석 사례 연구)

  • Jung, Jahe;Park, Hoon;Kim, Kwang Yeom;Shin, Hyu-Soung
    • Journal of the Korean Society of Safety
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    • v.30 no.6
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    • pp.94-101
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    • 2015
  • When a severe disaster such as a building collapse occurs, a first priority for rapid rescue is to find a location where people are highly expected to be buried but alive. It is, however, very difficult to correctly designate the location of such cavities by conventional geophysical survey due to a pile of debris of building members. In this study, location of possible lifeguard cavities were evaluated through a series of simulations of building collapse by explosion depending on the height of the building, a structure of basement floor and a location of explosion. Three types of building structure: five-story, ten-story and fifteen-story were prepared as a model for the simulation. As a results, in the case of low building, only basement floor partially collapsed. On the other hand, in the case of high building, a collapsed range on the inside of the building increased and lifeguard spaces were formed only in the lateral side or corner of the building. In addition, when a wall exists in the basement floor, the possibility that cavities could be formed increased compared to the cases without wall. However, for the fifteen-story building case, no possible lifeguard cavity was found. It is noted that for a high rise building, the height of building more affect forming of safeguard cavity than the structure of the basement floor.

Restoration Efficiency Analysis of Expansive Material Implemented Trenchless Underground Cavity Restoration Method Varying Number and Location of Bore Holes (팽창재료를 이용한 지하 공동 비개착 복구공법에서 천공 개수 및 위치에 따른 복구효율 분석)

  • Choi, Byeong-Hyun;Lee, Kicheol;Lee, Junwon;Kim, Dongwook
    • Journal of the Korean Geosynthetics Society
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    • v.18 no.4
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    • pp.25-37
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    • 2019
  • The conventional representative underground cavity restoration methods, which are mainly open-cut methods, require high cost and long period of time for the restoration. Therefore, various trenchless restoration methods have been proposed to improve these disadvantages. The underground cavity restoration method using the expansive material proposed in this paper is one of the trenchless methods. This method fills the underground cavity with high quality backfill soils through the small hole(s) at asphalt layer and compacts backfill soils by insertion of the expansive material within the cavity. In this study, the restoration method using expansive material was constructed in acrylic chamber. The restoration efficiency of the method was analyzed by the fill ratio and degree of relative compaction according to the location and number of bore holes. As a result of the experiment, the restoration efficiency and the optimum construction location were found to be irrelevant.

Model Study for Underground Cavity Detection Using S-wave (S파를 이용한 지하공동 탐사의 모형 연구)

  • 서백수
    • Tunnel and Underground Space
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    • v.3 no.2
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    • pp.109-117
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    • 1993
  • The existence and exact location of cavity is very important for the stability of the large underground storage house or building. Numerical method such as finite element method and finite diference methods are widely used because of model's complexity. Preliminary tests such as calculation step test, mesh size test and model size test were tried. Upper shadow zone and lower shadow zone can be calculated from 50% amplitude level of measuring data. From these statistical methods, the calculatied position of cavity coincided nearly with actual position of model testing cavity.

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Influence of limestone cavity on tunnel stability (석회암 공동이 터널의 안정에 미치는 영향)

  • Jin, Seong-Kyu;Yang, Moon-Sang;Choi, Deog-Chan;Park, Kwang-Joon
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.4 no.2
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    • pp.113-121
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    • 2002
  • This study is focused on establishing influence zone caused by tunnelling in limestone site. Therefore, the numerical analysis using the FLAC2D was performed considering various locations and magnitudes of cavities. To reduce the stress concentration, the shape of cavities was designed to ellipse. This parametric study reveals that the cavities located at crown part and edge part of tunnel greatly have influenced on stability of tunnel. The effect of distance between tunnel and cavity which is larger than 1-0D (Tunnel diameter) dose not directly related to stability of tunnel, but the nearer a cavity location was, the larger displacement and stress of reinforcement occured within 0.25D.

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Analysis of the under Pavement Cavity Growth Rate using Multi-Channel GPR Equipment (멀티채널 GPR 장비를 이용한 도로하부 공동의 크기 변화 분석)

  • Park, Jeong Jun;Kim, In Dae
    • Journal of the Society of Disaster Information
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    • v.16 no.1
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    • pp.60-69
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    • 2020
  • Purpose: Cavity growth process monitoring is to periodically monitor changes in common size and topography for general and observational grades to predict the rate of common growth. The purpose of this study is to establish a systematic cavity management plan by evaluating the general and observational class community in a non-destructive method. Method: Using GPR exploration equipment, the acquired surface image and the surrounding status image are analyzed in the GPR probe radargram in depth, profile, and cross section of the location. The exact location is selected using the distance and surrounding markings shown on the road surface of the initial detection cavity, and the test cavity is analyzed by calling the radar at the corresponding location. Result: As a result of monitoring tests conducted at a cavity 30 sites of general and observation grade, nine sites have been recovered. Changes in scale were seen in 21 cavity locations, and changes in size and grade occurred in 13 locations. Conclusion: The under road cavity is caused by various causes such as damage to the burial site, poor construction, soil leakage caused by groundwater leakage, waste and ground vibration. Among them, indirect factors could infer the effects of groundwater and localized rainfall.

Influence of Electrode Position on Performance of Sparkjet Actuator Using Numerical Analysis (수치해석을 이용한 전극 위치에 따른 스파크제트 액츄에이터의 성능 연구)

  • Shin, Jin Young;Kim, Hyung-Jin;Kim, Kyu Hong
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.47 no.11
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    • pp.753-760
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    • 2019
  • Sparkjet actuator, also known as plasma synthetic jet actuator, which is a kind of active flow control actuator is considered as being high possibility for the supersonic flow control due to ejecting stronger jet compared to the other active flow control actuators. Sparkjet actuator generates high temperature and high pressure flow inside the cavity by using arc plasma and leads momentum by ejecting such flow through orifice or nozzle. In this research, numerical calculation of sparkjet actuator with respect to the location of electrodes which exists inside the cavity is conducted and the change of the performance of sparkjet actuator is suggested. As the location of electrodes goes closer to the bottom of the cavity, impulse is increased and the average pressure inside the cavity maintains higher. When the location of electrode is 25% and 75% of the entire cavity height, impulse is 2.515 μN·s and 2.057 μN·s, respectively. Each impulse is changed by about 9.92% and -10.09% compared to when the location of electrodes is 50% of the entire cavity height.

Experiments for the Acoustic Source Localization in 2D Cavity Flow (2차원 공동 유동에서의 소음원 위치 판별을 위한 실험적 연구)

  • Lee, Jaehyung;Park, Kyu-Chol;Choi, Jong-Soo
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.14 no.12
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    • pp.1241-1248
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    • 2004
  • This paper presents an acoustic source localization technique on 2D cavity model in flow using a phased microphone array. Investigation was performed on cavity flows of open and closed types. The source distributions on 2D cavity flow were investigated in an anechoic open-jet wind tunnel. The array of microphones was placed outside the flow to measure the far field acoustic signals. The optimum sensor placement was decided by varying the relative location of the microphones to improve the spatial resolution. Pressure transducers were flush-mounted on the cavity surface to measure the near-filed pressures. It is shown that the propagated far field acoustic pressures are closely correlated to the near-field pressures and their spectral contents are affected by the cavity parameter L/D.