• Title/Summary/Keyword: CFD 유동해석

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A Numerical Study for Fire Safety Evaluation of the Multi-story Residential Buildings -The Effects of the Openings of Stairwell on Fire Characteristics- (다세대주택의 화재안전평가에 대한 수치해석 연구 -계단실 개구부의 개폐가 화재특성에 미치는 영향-)

  • Jeon, Heung-Kyun;Choi, Young-Sang;Choo, Hong-Lok
    • Fire Science and Engineering
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    • v.21 no.3
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    • pp.15-23
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    • 2007
  • In the events of a fire in the residential building, highly flammable polyurethane foam sofa produce toxic smokes. In this type of fire, the residents of the building can be gotten into the difficulties of evacuating from the fire places or may be to death due to a lot of hot toxic gases. In this study, CFD simulations were carried out to study the effects of the openings of stairwell on the fire characteristics of fire room and stairwell. Also, analysis of fire hazard based on the tenability limits of fire and FED(fractional effective dose) was performed to evaluate the life safety of the residents of the building. In the fire room, maximum temperature was about 290C, maximum CO concentration was about 4,740 ppm, and the time to incapacitation of residents in fire room was about t=144 s. In the stairwell, temperature and CO concentration in the condition of openings to be open were even lower than those in it to be closed. Time to the tenability limit with respect to smoke visibility in the stairwell with openings, which was open, was shorter than that of it without openings to be open. It has been shown from this study that opening the stairwell openings is able to decrease the fire hazards to the life safety in the multi-story residential building fire.

STUDY ON THE THERMAL-FLUID ANALYSIS OF CRYOGENIC CHAMBER FOR COLD CLIMATE TEST OF LARGE WIND TURBINE PARTS (대형 풍력발전기 부품의 극한 환경 시험을 위한 극저온 챔버의 열유동 해석에 대한 연구)

  • Kim, M.K.;Kang, Y.H.;Park, W.G.
    • Journal of computational fluids engineering
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    • v.20 no.3
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    • pp.8-14
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    • 2015
  • More and more, spaces are decreasing which satisfy multiple requirements for wind power plants. However, areas which have excellent wind resources and are free to civil complaints occupy a large space, although they are exposed to the cryogenic environment. This study conducted a thermal-fluid analysis of a cryogenic chamber for testing large wind turbine parts exposed to the cryogenic environment. The position of supply air is placed to the upper area to compare each cooling performance for each location of various outlets in mixing ventilated conditions. The study carried out CFD analysis for the chamber both with and without a test object. For the cases without the test object, the air temperature of the upper supply and down extract type chamber was cooled faster by 5-100% than the others. However, for the cases with the test object, the object temperature of upper supply and center extract on the opposite side type chamber was cooled faster by 33-132% than the others. The cooling performance by the air inside the chamber and the test object did not show the same pattern, which implicates the need to consider the cooling performance by not only the air but also the test object in the large cryogenic chamber design for testing large parts.

A Study on the Blade Load Measurement of Partial-admission Turbine Cascade (충동형 터빈 캐스케이드의 깃 하중 측정에 관한 연구)

  • Lim, Dong-Hwa;Jang, Jin-Man;Lee, Eun-Seok;Kim, Jin-Han;Choi, Jong-Soo
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.35 no.2
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    • pp.143-148
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    • 2007
  • An impulse turbine, which is a main component of a liquid rocket engine, needs to be a small size with light weight and generate large power. Since the impulse turbine is being operated under complicated supersonic conditions, flow analysis and performance prediction largely depend on CFD technique. In order to increase the reliability of the prediction code, however, it often requires an experimental data to compare. In this research a rotating turbine rotor with multiple blades is simulated with a two-dimensional stationary cascade to check the effect of major flow parameters. Mach number is measured at nozzle exit by using a pitot tube and the blade thrust was also measured with a load cell. The measured thrust coefficient and the power are compared well with the designed conditions, which proves the design procedures are properly taken.

Analysis of Flows around the Rotor-Blades as Rotating Body System of Wind Turbine (풍력 발전기의 Rotor-Blades 회전체 시스템 공력 해석)

  • Kim, Don-Jean;Kwag, Seung-Hyun;Lee, Kyong-Ho
    • Journal of Ocean Engineering and Technology
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    • v.23 no.5
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    • pp.25-31
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    • 2009
  • The most important component of wind turbine is rotor blades. The developing method of wind turbine was focused on design of rotor blade. By the way, the design of a rotating body is more decisive process in order to adjust the performance of wind turbine. For instance, the design allows the designer to specify the wind characteristics derived by topographical map. The iterative solver is then used to adjust one of the selected inputs so that the desired rotating performance which is directly related to power generating capacity and efficiency is achieved. Furthermore, in order to save the money for manufacturing the rotor blades and to decrease the maintenance fee of wind power generation plant, while decelerating the cut-in speed of rotor. Therefore, the design and manufacturing of rotating body is understood as a substantial technology of wind power generation plant development. The aiming of this study is building-up the profitable approach to designing of rotating body as a system for the wind power generation plant. The process was conducted in two steps. Firstly, general designing and it’s serial testing of rotating body for voltage measurement. Secondly, the serial test results above were examined with the CFD code. Then, the analysis is made on the basis of amount of electricity generated by rotor-blades and of cut-in speed of generator.

Numerical Analysis of Tip Vortex and Cavitation of Elliptic Hydrofoil with NACA 662-415 Cross Section (NACA 662-415 단면을 가지는 타원형 수중익의 날개 끝 보오텍스 및 캐비테이션 수치해석)

  • Park, Il-Ryong;Kim, Je-in;Seol, Han-Sin;Kim, Ki-Sup;Ahn, Jong-Woo
    • Journal of Ocean Engineering and Technology
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    • v.32 no.4
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    • pp.244-252
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    • 2018
  • This paper provides quantification of the effects of the turbulence model and grid refinement on the analysis of tip vortex flows by using the RANS(Reynolds averaged Navier-Stokes) method. Numerical simulations of the tip vortex flows of the NACA 662-415 elliptic hydrofoil were conducted, and two turbulence models for RANS closure were tested, i.e., the Realizable kε model and the Reynolds stress transport model. Numerical results were compared with available experimental data, and it was shown that the data for the Reynolds stress transport model that were computed on the finest grid system had better agreement in reproducing the development and propagation of the tip vortex. The Realizable kε model overestimated the turbulence level in the vortex core and showed a diffusive behavior of the tip vortex. The tip vortex cavitation on the hydrofoil and its trajectory also showed good agreement between the current numerical results that were obtained using the Reynolds stress transport model and the results observed in the experiment.

Aerodynamic Characteristics of the Grid Fins on SpaceX Falcon 9 (SpaceX Falcon 9 그리드핀의 공력 특성)

  • Lee, HyeongJin;Cho, WooSung;Ko, SangHo;Lee, Yeol
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.48 no.10
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    • pp.745-752
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    • 2020
  • A numerical study was carried out to evaluate the aerodynamic characteristics of the supersonic grid fins installed on SpaceX Falcon 9. The unit-grid-fin concept was utilized for more efficient and simpler 3-D steady flow calculations. Pre- and post-correction processes that accounted the interference effects by the angle of attack of the missile, the influences of the outer frame of the grid fin and the connecting rods were improved in the study, and it was demonstrated that the present correction method was more accurate as compared to previous studies. Finally, the present approach was applied to evaluate the aerodynamic characteristics in transonic/supersonic flights of SpaceX Falcon 9 with various angle of attacks.

Investigation of the Effects of UAV Nozzle Configurations on Aircraft Lock-on Range (무인항공기의 노즐 형상 변화가 Lock-on Range에 미치는 영향에 관한 연구)

  • Kim, Min-Jun;Kang, Dong-Woo;Myong, Rho-Shin;Kim, Won-Cheol
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.43 no.3
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    • pp.204-212
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    • 2015
  • The infrared lock-on range of target aircraft plays a critical role in determining the aircraft survivability. In this investigation, the effects of various UAV engine nozzle configurations on the aircraft lock-on range were theoretically analyzed. A virtual subsonic aircraft was proposed first, based on the mission requirement and the engine performance analysis, and convergent-type nozzles were then designed. After determining thermal flow field and nozzle surface temperature distribution with the CFD code, an additional analysis was conducted to predict the IR signature. Also, atmospheric transmissivity for various latitude and seasons was calculated, using the LOWTRAN code. Finally, the lock-on and lethal envelopes were calculated for different nozzle configurations, assuming the sensor threshold of the given IR guided missile. It was shown that the maximum 55.3% reduction in lock-on range is possible for deformed nozzles with the high aspect ratio.

Consequence Analysis of Toxic Gases Generated by Fire of Lithium Ion Batteries in Electric Vehicles (전기자동차 내 리튬이온전지 화재로 발생하는 독성가스의 위험성 분석)

  • Oh, Eui-young;Min, Dong Seok;Han, Ji Yun;Jung, Seungho;Kang, Tae-sun
    • Journal of the Korean Institute of Gas
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    • v.23 no.1
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    • pp.54-61
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    • 2019
  • As the market for portable electronic devices expands, the demand for Lithium Ion Battery (LIB) is also increasing. LIB has higher efficiency than other secondary batteries, but there is a risk of explosion / fire due to thermal runaway reaction. Especially, Electric Vehicles (EV) equipped with a large capacity LIB cell also has a danger due to a large amount of toxic gas generated by a fire. Therefore, it is necessary to analyze the risk of toxic gas generated by EV fire to minimize accident damage. In this study, the flow of toxic gas generated by EV fire was numerically analyzed using Computational Fluid Dynamic. Scenarios were established based on literature data and EV data to confirm the effect distance according to time and exposure standard. The purpose of this study is to analyze the risk of toxic gas caused by EV fire and to help minimize the loss of life and property caused by accidents.

Field Survey and Analysis of Natural Ventilation Characteristics of Multi-span Greenhouse with Different Roof Vent (연동형 비닐하우스의 환기창 형태 조사 및 자연환기 효과 분석)

  • Park, Min jung;Choi, Duck kyu;Son, Jin kwan;Yoon, Sung-Wook;Kim, Hee tae;Lee, Seung-Kee;Kang, Dong hyeon
    • Journal of Bio-Environment Control
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    • v.29 no.1
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    • pp.36-42
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    • 2020
  • The objectives of this study were to investigate the standard and roof vent type of multi-span greenhouse and to analyze the characteristics of natural ventilation of multi-span greenhouse with different roof vent using computational fluid dynamics (CFD) code. The vent area proportion of surveyed farms averaged 10%, it was analyzed that the vent design for natural ventilation is insufficient. The results of natural ventilation efficiency of multi-span greenhouse according to roof vent type showed that the temperature of the position in which the crops grew was the lowest in the conical roof vent type and the highest in the half conical roof vent type. For the natural ventilation effect, the conical roof vent type was the best one, but the structural stability should be evaluated in light of wind load.

Analysis of Hydraulic Characteristics Upstream of Dam and in Spillway Using Numerical Models (수치모형을 이용한 댐 상류 및 여수로 수리현상 해석)

  • Kim, Young-Han;Oh, Jung-Sun;Seo, Il-Won
    • Journal of Korea Water Resources Association
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    • v.36 no.5
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    • pp.761-776
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    • 2003
  • Numerical models were employed to investigate the hydrodynamics of water flow in the lake behind a dam and the spillway where supercritical flows and negative pressures are likely to occur. In this study, 2-D model, RMA2 was employed to examine the upstream flow pattern and 3-D CFD model, FLUENT was used to evaluate the three-dimensional flow in the approaching region and flow distributions in the spillways and discharge culverts. The bathymetry and the details of structures were carefully taken into consideration in building the models. The results from applying the 2-D model for the planned Hantan River Dam show that large eddies, the velocity of which reaches up to 1 m/s are occurring in several places upstream of the dam. That means that the 2-D numerical model could be utilized to investigate the two-dimensional flow patterns after the construction of a dam. Three-dimensional numerical results show that the approach flow varies depending on stages and discharge conditions, and velocities at spillways, discharge culverts, and sediment flushing tunnels are differently distributed. The velocity distributions obtained from the numerical model and a hydraulic model at the centerline of spillways 100 m upstream of the dam show reasonably similar results. It is expected that 2-D and 3-D numerical models ate useful tools to help optimize the dam design through investigating the flow patterns in the spillway and at the upstream of the dam, which is not always feasible in hydraulic modeling.