• 제목/요약/키워드: Front Velocity

검색결과 601건 처리시간 0.032초

정전탐침법에 의한 예혼합 난류전파화염의 구조에 관한 연구 (A Study on the Structure of Premixed Turbulent Propagating Flames Using a Microprobe Method)

  • 김준효;안수길
    • 한국자동차공학회논문집
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    • 제3권6호
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    • pp.78-86
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    • 1995
  • The structure of premixed turbulent flames in a constant-volume vessel was investigated using a microprobe method. The flame potential signal having one to eight peaks was detected in the case of turbulent flames, each of them being regarded as a flamelet existing in the flame zone. Based on this consideration, the flame propagation speed, the thickness of the flame zone, the number of flamelets and the separation distance between adjacent flamelets in the flame zone were measured. The experimental resuits of this work suggest the existence of "reactant islands" behind the flame front when the turbulence was intensified to some extent. The critical(lowest) ratio of turbulence intensity to the laminar burning velocity being found to be about 0.7 for the formation of reactant islands in this experiment.

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단면 형상 및 국부 보강에 따른 직선 부재의 충돌 성능 (Crash Performance of a Straight Member for Various Section Shapes and Local Reinforcement)

  • 이헌봉;강성종
    • 한국자동차공학회논문집
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    • 제21권5호
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    • pp.97-103
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    • 2013
  • Crash performance of the straight member was studied by FE analysis. One end of model was fixed and the other end was impacted by 1,000kg rigid mass with velocity of 16.0m/sec. The maximum and mean load were discussed to compare crash performance. The members with various section shapes were analyzed and the flange location was changed. Also, spot weld points were added in the initial buckling region to investigate its effect. Final rectangular section model which has flanges at the center and reinforcement in initial buckling region showed high enhancement in crash performance.

수직갱이 설치된 터널내 화재시 연기거동에 관한 실험적 연구 (An Experimental Study of Smoke Movement in Tunnel Fires with a Vertical Shaft)

  • 이성룡;유홍선;김충익
    • 설비공학논문집
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    • 제16권2호
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    • pp.135-141
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    • 2004
  • The present paper concerns a smoke movement in a tunnel fire with a vertical shaft. The model tunnel measured 13.4m long, 0.4m wide and 0.4m high. The cross section is 1: 20 of a full scale tunnel. Ethanol was used as a fuel. The fire size in model tests varied from 1.35 kW to 13.37 kW, which corresponds to full scale fires of 2.41 to 23.91 MW. Smoke front velocity and temperatrue were decreased due to the vertical shaft install. Temperature was reduced maximum about 2$0^{\circ}C$ at ceiling and about 23$^{\circ}C$ at vertical position. CO concentration was reduced as the vent width widened. When vent width was more than 15 cm, CO concentration was not reached 100 ppm. Descent degree of the smoke layer was confirmed through the visualization.

SMC 압축성형공정의 모델링 및 유한요소법을 이용한 열유동 해석 (Finite Element Analysis of the Flow in SMC Compression Molding and Its Applications)

  • 이응식;윤성기
    • 대한기계학회논문집
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    • 제18권11호
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    • pp.3084-3090
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    • 1994
  • A new flow model is developed for the analysis of compression molding of sheet molding compounds(SMC) and penalty finite element formulation is presented to predict flow front progressions more accurately. In this model SMC is assumed nonisothermal fluid, which has different viscosities in extension and in shear. The flow is allowed to slip at the mold and is resisted by friction force which is proportional to the relative velocity at mold surface. For the verification of the model, the press force and flow patterns are compared with those of experiments and available results by other works in this field. It is also demonstrated, using the computational procedure described and the proposed model, that optimal initial charge shapes for the filling can be effectively computed.

주 유동의 난류특성이 원통 표면에서의 열전달에 미치는 영향에 관한 연구 - 수치 해석적 고찰 - (The Effect of Main Stream Turbulence on the Heat Transfer Around a Cylinder Surface)

  • 박정훈;최영기;유홍선
    • 설비공학논문집
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    • 제3권3호
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    • pp.186-196
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    • 1991
  • Numerical analysis has been performed to investigate the effects of the turbulence intensity and Prandtl number on the local heat transfer around a circular cylinder in crossflow. The governing equations were reformulated in a non-orthogonal coordinate system with Cartesian velocity components and discretised by the finite volume method with a non-staggered variable arrangement. For laminar flow, the calculations were performed for the Reynolds numbers 26 and 200. The results showed good agreement with the experimental results. For turbulent flow of the Reynolds number $1{\times}10^5$ and $2{\times}10^6$, the results showed that with an increase in the turbulent intensity in the main stream, the local Nusselt number increases in the front region of the circular cylinder. But the effect of turbulent intensity on the local Nusselt number diminishes in the wake region. The influence of Prandtl numbers show similar trend to that of turbulent intensity.

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화물열차용 제륜자의 열유동 해석 (Numerical Analysis on Heat Transfer and Fluid flow of Brake Shoe for Freight Car)

  • 남성원
    • 한국철도학회:학술대회논문집
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    • 한국철도학회 2001년도 춘계학술대회 논문집
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    • pp.123-128
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    • 2001
  • Numerical simulation is conducted to clarify the heat transfer and fluid flow characteristics of brake shoe for freight car. High order up-wind scheme for governing equations, k-epsilon turbulent model and SIMPLEC algorithm based on finite volume method are used to solve the physical shoe model. The governing equations are solved by TDMA(Tri-Diagonal Matrix Algorithm) with line-by-line method and block correction. From the results of simulation, the characteristics of cooling pattern is strongly affected by the velocity of train and the material of shoe. The face lift of shoe affects on the temperature distribution of rear surface of shoe as well as the front surface of that. Due to the grooves in shoe, it will be expected to cool the frictional heat and result in the reduction of maintenance efforts.

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컴퓨터 시뮬레이션 기법을 이용한 고속전철 승객안전도 해석 및 평가 (A Study of KHST Passenger Safety During Accidents by Computer Simulation Techniques)

  • 윤영한;구정서;이재완
    • 한국철도학회논문집
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    • 제6권1호
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    • pp.15-20
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    • 2003
  • The computer simulation techniques were adopted to evaluate the effects of seating positions of passenger under various accident scenarios. The baseline of computer simulation model was tuned by the sled impact tests which conducted under the upright and standard seating positions. This study shows the effect of relative velocity between occupant and struck vehicle while occupant is impacted to a front seat's seatback. Although, base on the current accident scenarios, The KHST is performed well enough to protect average adult male occupants. However, Results from the tests indicate small size occupant or higher impact speed may cause sever neck and femur injuries.

원심펌프 측면흡입구의 유동특성에 관한 수치해석적 연구 (A Numerical Study on the Flow Characteristics of Side-suction Inlet Geometry for Centrifugal Pump)

  • 김성;최영석;이경용
    • 한국유체기계학회 논문집
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    • 제12권6호
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    • pp.7-12
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    • 2009
  • This paper presents a numerical study on the design of side-suction inlet geometry which is used for multi stage centrifugal pumps or inline centrifugal pumps. In order to achieve an optimum inlet geometry and to explain the interactions between the different geometric configurations, the three dimensional computational fluid dynamics and the design of experiment methods have been applied. Geometric design variables describing the cross sectional area distribution through the inlet were selected. The objective functions are defined as the non-uniformity of the velocity distribution at the passage exit which is just in front of the impeller eyes. From the 2k factorial design results, the most important design variable was found and the performance of the side suction inlet was improved compared to the base line shape.

낙동강 하구역 사주 주변에서의 퇴적물질의 유압거동 해석 (The Analysis of Inflowing Sediments Behavior around the Sandbar in Nakdong River Estuary)

  • 김경희;이인철
    • 한국해양공학회:학술대회논문집
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    • 한국해양공학회 2004년도 학술대회지
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    • pp.133-136
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    • 2004
  • In-situ collection experiments were performed to analyze inflowing sedilnents behavior as a basic study of topographical change in Nakdong River Estuary. Sediment rate and bed load flux ranged from 0.0004 to $0.472\;g/cm^2/day\;and\;0.0005\~1.7579\;g/cm^2/day$, respectively. The settling velocity of suspended particulate matter was estimated in tire range of $0.339\~1.010\;cm/sec$, The grain size analysis shows that surface sediments in backside of sandbar and bed load in front of dike have a similar grain size distribution. It is considered that the source of surface sediments in backside of sandbar were flowed in from Nakdong River. In order to verify the characteristics of inflowing sediments behavior, detailed surveys around Nakdong River Estuary need to be carried out, continuously.

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소규모 저수지에서 밀도류의 거동 및 순환 (The Behavior and Circulation of Density Current in a Small Reservoir)

  • 윤태훈;한운우
    • 대한토목학회논문집
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    • 제11권2호
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    • pp.27-37
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    • 1991
  • 음부력을 갖는 유체가 소규모 저수지로 유입되어 일어나는 밀도류의 거동 및 순환이 차원해석과 수리실험을 이용하여 해석된다. 무차원침강점 및 밀도류전면속도, 밀도류전면이동거리, 머리 뒤의 밀도층내회석 등은 유입밀도후르드수, Fre의 영향을 받으며 밀도층의 두께, 흐름양상 및 저수지내 밀도의 변화는 밀도류전면이 하류단에 도달하여 반사되기 전과 후의 양상이 현저하게 다르다. 밀도층의 두께는 전자의 경우에는 Fre, 후자의 경우는 시간과 Fre의 영향을 받으며 이들은 지수식으로 표현할 수 있다.

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