• Title, Summary, Keyword: 공동 유동

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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.

Investigation of Transonic and Supersonic Flows over an Open Cavity Mounted on Curved Wall (I) - Steady Flow Characteristics - (곡면상에 설치된 열린 공동을 지나는 천음속/초음속 유동에 관한 연구 (I) - 정상 유동의 특성 -)

  • Ye, A Ran;Das, Rajarshi;Kim, Huey Dong
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.39 no.3
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    • pp.231-236
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    • 2015
  • Investigations into cavity flows have been conducted for decades now, most of them being about zero-pressure-gradient flows entering a cavity on a straight wall. However, the flow over curved walls in real-life situations has not been fully investigated. As cavity flows on curved walls exert centrifugal force, these walls are likely to possess different features from straight walls. To verify this possibility, this study investigated cavity flows on curved walls. Using numerical method, the effect of two variables, namely, radius of curvature on a curved wall and inlet Mach number, were investigated for subsonic and supersonic cavity flows. The result demonstrates that the value of the peak pressure generated inside the cavity increases with the decrease in the radius of curvature on a curved wall or an increase in the inlet Mach number. The total pressure loss in the cavity also results in an increase in the cavity drag.

Frequency Analysis of the Sweepback Cavity in the Scramjet Engine (스크램제트 엔진 내 후퇴각 공동의 주파수 특성 분석)

  • Jeong, Eun-Ju;Jeung, In-Seuck;O'Byrne, Sean;Houwing, A.F.P.;Kang, Sang-Hun;Yang, Soo-Seok
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • pp.293-296
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    • 2007
  • Using the T3 free-piston shock tunnel in ANU, the cavity frequency and flow characteristics of no mass-injection, inclined mass-injection before the cavity, parallel or reverse mass-injection in the cavity are investigated in the case of Mach 3.7 inflow condition. No mass-injection doesn't have the harmonic frequencies but has high amplitude of pressure spectrum at 10 kHz. Inclined mass-injection attenuates the cavity flow fluctuation as disturbing the shear layer reflection at the trailing edge. Parallel mass-injection flow reflects at the trailing edge of the cavity directly hence, increases the cavity flow fluctuation at high injection pressure.

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Numerical Study of Unsteady Supersonic Flow over Tandem Cavities (초음속 비정상 직열배치공동 유동에 관한 수치적 연구)

  • Song, Byeong Ho;Park, Nam Eun;Kim, Jae Su
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.31 no.2
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    • pp.10-16
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    • 2003
  • The unsteady supersonic flow over tandem cavities has been analyzed by the integration of Navier-Stokes equations with the k-$\varepsilon$ turbulence model. The unsteady flow is characterized by the periodicity due to the mutual relation between the shear layer and the internal flow in cavities. The upwind TVD scheme based on the flux vector split with the van Leer limiters is used. The results show the principal frequency is very reasonable. The principal frequency of the rear cavity due to the front cavity has been analyzed by the combination of the several aspect ratios of cavities. In the case of the front cavity of low aspect ratio, the frequencies of tandem cavities are almost same, because two shear layers developed from each cavity are mixed and developed to one shear layer. However, in the case of the front cavity of high aspect ratio, the characteristis of frequency are very different, because the second shear layer is developed in the diffused first shear layer.

Control of the Pressure Oscillations in Supersonic Cavity Flows (초음속 공동유동에서 발생하는 압력변동의 제어)

  • Lee Young-Ki;Jung Sung-Jae;Kim Heuy-Dong
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • pp.117-120
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    • 2005
  • The present study describes unsteady flow phenomena generated in a supersonic flow passing over a rectangular cavity and suggests a way of control of pressure oscillation, doing harm to overall performance and stable operation of aerodynamic and industrial applications. The three-dimensional, unsteady, compressible Navier-stokes equations are numerically solved based on a fully implicit finite volume scheme and large eddy simulation. The cavity flow are simulated with and without control methods, including a triangular bump and blowing jet installed near the leading edge of the cavity. The results show that the pressure oscillation is attenuated by both control techniques, especially near the trailing edge of cavity.

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A Study on the Pressure Oscillations in the High-Subsonic Cavity Flows over a Curved Wall (곡면 벽을 지나는 고아음속 공동 유동에서 발생하는 압력 진동에 관한 연구)

  • Ye, A Ran;Lee, Ik In;Kim, Jeong Soo;Kim, Heuy Dong
    • Journal of the Korean Society of Propulsion Engineers
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    • v.20 no.5
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    • pp.77-83
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    • 2016
  • A considerable amount of researches has been performed to investigate the flow characteristics produced in the cavity system over straight wall. However, many practical applications of the cavity flows are found on curved walls, which are strongly subject to the centrifugal force effects. No work has been made on the cavity flows on the curved wall to date. In the present study, a computational fluid dynamics method has been applied to investigate the cavity flows over curved walls at Mach numbers in range of 0.4 to 0.8. The aspect ratio of the cavity was fixed at L/H=3, but the radius of curvature of the curved wall is changed in considering the real engineering practice. The results reveal that the pressure oscillations in the curved walls are stronger than those in the straight wall. It is found that the ratio of curvature of the curved wall significantly affects the unsteady flow characteristics inside the cavity.

Natural Convection in a Rectangular Cavity Washed Externally by a Turbulent Boundary Layer (외부 난류 경계층과 결합된 직사각형 공동에서의 자연대류)

  • 최철진;장근식
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.9 no.4
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    • pp.518-527
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    • 1985
  • 대류-대류의 복합 열전달 문제를 유한차분법을 사용하여 수치적으로 연구하였다. 아래로부터 가열되는 직사각형 공동 내에서의 자연 대류와 공동 위쪽의 외부 난류 경계층 유동이 복합된 경우의 열전당 현상을 고려하였다. 두개의 서로 다른 모우드의 대류가 온도 분포가 미리 알려져 있지 않은 얇은 수평평판에 의해 분리되어져 있다는 점이 본 논문의 특이점이다. 수치적 해석은 Reynolds 수와 Grashof 수 및 공동의 기하학적 종횡비의 매개 변수적 효과가 발견되도록 행하여 졌다. 외부 난류 경계층 유동의 강도에 따라 공동 내에서의 유동 형태가 변할 수 있음을 알았다. 즉 내부 부력 세포의 회전 방향은 외부 유동의 존재에 의해 특성적으로 정해지며 공동 내의 유동 세포의 수는 Grashof 수가 증가 할수록 많아진다.

Flow Variation Analysis of Cavity Depending on Aspect Ratio using EDISON_CFD (EDISON_CFD를 이용한 세장비에 따른 공동의 유동 변화 분석)

  • Ha, Heon-U
    • Proceeding of EDISON Challenge
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    • pp.349-353
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    • 2013
  • 공동주위의 유동에 대한 연구결과를 보면 개방형 공동(L/D<10)과 밀폐형 공동(L/D>13)으로 구별하는 데 개방형 공동은 앞전에서 발생한 자유전단층이 뒷전 부근에 재부착하여 공동을 완전히 연결하므로, 자유전단층과 외부유동과의 상호작용으로 발생하는 심한 압력변화에 의해 진동현상이 나타나게 된다. 이것은 큰 소음을 유발하고, 구조물의 고장 혹은 파괴의 원인이 되기도 하고, 공력 성능 및 안정성에 해를 주고 민감한 계기를 손상 시킬 수도 있다. 본 논문에서는 공동을 연구하기 위해 EDISON_CFD를 사용하여 공동의 시뮬레이션하기 위해 격자를 구성하고 세장비를 각각 1/5, 1/3, 1/2, 1, 2, 5 로 변화를 주어 M=1.5 일 때 밀도, 압력, 마하수와 유동구조를 세장비에 따라 결과를 비교, 분석한다.

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Control of Supersonic Cavity Flow Oscillation Using Passive Means (피동제어법을 이용한 초음속 공동유동의 진동 제어)

  • Lee, Young-Ki;Deshpande, Srikanth;Kim, Heuy-Dong
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • pp.363-366
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    • 2006
  • The effectiveness of two passive control techniques for alleviating the pressure oscillation generated in a supersonic cavity flow is investigated numerically. The passive devices suggested in the present research include a triangular bump and a sub-cavity installed near the upstream edge of a rectangular cavity. The supersonic cavity flow characteristics are examined by using the three-dimensional, unsteady Wavier-Stokes computation based on a finite volume scheme. Large eddy simulation (LES) is carried out to properly predict the turbulent features of cavity flow. The results show that the pressure oscillation near the downstream edge dominates overall time-dependent cavity pressure variations. Such an oscillation is attenuated more considerably using the sub-cavity compared with other methods, and a larger sub-cavity leads to better control performance.

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Groundwater Flow Characteristics Affected by the Seawater Intrusion near Simulated Underground Storage Caverns in the Coastal Area (임해지역의 모의 지하 비축 시설 주변에서 해수 침투에 의한 지하수 유동 특성)

  • 황용수;배현숙;서동일;김경수;김천수
    • The Journal of Engineering Geology
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    • v.9 no.1
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    • pp.17-29
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    • 1999
  • There are three major processes to impact the groundwater flow near underground storage caverns in the coastal area; effect of topography, effect of sea water intrusion, and effect of excavation. In this paper, the effects of three items were numerically studied to identify the major cause for altering the flow pattern. It turned out that the excavation is the most significant effect on the groundwater flow system. The groundwater pressure distributions and consequent groundwater pathways were significantly altered near the openings. By increasing the groundwater pressures from water curtain holes, the potential leakage of storage cavern was properly prevented

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