• Title, Summary, Keyword: 거칠기가 있는 벽면

Search Result 8, Processing Time 0.034 seconds

NUMERICAL SIMULATION OF SUPERSONIC FLOW USING POROUS AND ROUGH WALL BOUNDARY CONDITIONS (다공성 벽면(porous-wall)과 거칠기가 있는 벽면(rough-wall)에 과한 경계조건을 이용한 초음속 흐름의 수치모사)

  • Kwak, E.K.;Yoo, I.Y.;Lee, S.
    • 한국전산유체공학회:학술대회논문집
    • /
    • /
    • pp.104-111
    • /
    • 2009
  • The existing code which solves two-dimensional RANS(Reynolds Averaged Navier-Stokes) equations and 2-equation turbulence model equations was modified to enable numerical simulation of various supersonic flows. For this, various boundary conditions have been implemented to the code. Bleed boundary condition was incorporated into the code for calculating wall mean flow quantities. Furthermore, the boundary conditions for the turbulence quantities along rough surfaces as well as porous walls were applied to the code. The code was verified and validated by comparing the computational results against the experimental data for the supersonic flows over bleed region on a flat plate. Using the newly modified code, numerical simulations were performed and compared with other computational results as well as the experimental data for the supersonic flows over an oblique shock with a bleed region.

  • PDF

An Analysis of Fully Developed Turbulent Heat Transfer and Flow in an Annulus with the Square-Ribbed Roughness on Both Walls (양측벽면에 사각돌출형 거칠기가 있는 이중관내의 난류유동과 열전달 해석)

  • 안수환
    • Journal of the Korean Society of Marine Engineering
    • /
    • v.17 no.3
    • /
    • pp.33-41
    • /
    • 1993
  • 양벽면 모두 사각돌출형조도요소가 설치된 동심 이중관내에서 생기는 비대칭 난류유동과 열전달 특성을, 열전달과 마찰계수에 미치는 조도의 합성효과를 조사하기 위해, 연구하였다. 이론해석에서는 한쪽면에 거칠기가 있는 평행평판의 유동에 대한 수정 플란틀 혼합길이(mixing length)이론의 난류 모델을 속도분포와 마찰계수를 구하는데 사용하였다. 최대속도지점에서 안쪽과 바깥쪽의 두 속도형상들은 힘의 평형에 의해 일치시켰다. 그리고 나서, 온도 분포와 열전달 계수를 계산하였다. 속도형성과 마찰계수들의 해석결과는 실험과 매우 잘 일치하였다. 마찰계수와 Nusselt number에 미치는 조도비, 조도에 대한 피치비, 그리고 반경비등과 같은 여러 변수들의 효과들을 조사하였다. 본 연구는 일정의 조도 요소들이 전체적 효율 측면에서 볼때 유리하게 열전달을 향상시킨다는 것을 증명하였다.

  • PDF

NUMERICAL SIMULATIONS OF SUPERSONIC FLOWS USING POROUS AND ROUGH WALL BOUNDARY CONDITIONS (다공성 벽면(porous-wall)과 거칠기가 있는 벽면(rough-wall)에 관한 경계조건을 이용한 초음속 흐름의 수치모사)

  • Kwak, E.K.;Yoo, I.Y.;Lee, D.H.;Lee, S.
    • Journal of computational fluids engineering
    • /
    • v.14 no.4
    • /
    • pp.23-30
    • /
    • 2009
  • The existing code which solves two-dimensional RANS(Reynolds Averaged Navier-Stokes) equations and 2-equation turbulence model equations was modified to enable numerical simulation of various supersonic flows. For this, various boundary conditions have been implemented to the code. Bleed boundary condition was incorporated into the code for calculating wall mean flow quantities. Furthermore, boundary conditions for the turbulence quantities along rough surfaces as well as porous walls were applied to the code. The code was verified and validated by comparing the computational results against the experimental data for the supersonic flows over bleed region on a flat plate. Furthermore, numerical simulations for supersonic shock boundary layer interaction with a bleed region were performed and their results were compared with the existing computational results.

Effect of Roughness Position on the Characteristics of Turbulence in Concentric Annuli (동심환형관에서 난류특성에 미치는 조도위치의 효과)

  • Ahn, S.W.;Lee, W.J.
    • Journal of the Korea Society For Power System Engineering
    • /
    • v.1 no.1
    • /
    • pp.61-69
    • /
    • 1997
  • 본 연구는 동심환형관에서 거칠기가 없이 매끈한 경우, 내측벽에 만, 외측벽에 만, 그리고 양측 모두에 거칠기가 있는 4경우에 대해 직경비가 0.26, 0.39, 그리고 0.56일 때 벽면에 설치된 거칠기 위치들이 난류유동장에 미치는 효과를 실험적으로 조사하고자 한다. 최대속도와 전단응력이 0인 지점들, 시간평균속도의 구배들, 그리고 와확산계수들을 X형 열선풍속계와 이중 피토튜브를 사용하여 측정하였다. 본 연구를 통하여 동심환형관에 설치된 거칠기들이 난류유동에 미치는 효과에 대한 정량적자료를 제시할 수 있었다.

  • PDF

Turbulent Flow and heat Transfer in the Annular Passage with Repeated-Ribbed Roughness on Both Walls (양측벽면에 반복돌출형 거칠기가 있는 이중관통로내의 난류유동과 열전달)

  • 안수환;김덕현
    • Journal of the Korean Society of Marine Engineering
    • /
    • v.20 no.1
    • /
    • pp.1-12
    • /
    • 1996
  • The fully developed tubulent momentum and heat transfer induced by the square- ribbed roughness elements on both the inner and outer wall surfaces in the concentric annuli are studied analytically based on a modified turbulence model. Heat transfer coefficients for two conditions, i.e, a) inner wall heated as constant heat flux and outer wall insulated b) inner wall insulated and outer wall heated as constant heat flux, are investigated. The analytical results of the fluid flow are verified by experiment. The experiment is done with a pitot tube and a X-type hot wire anemometer to measure the time mean velocity profiles, zero shear stress positions, maximum velocity profiles and friction factors, and etc. The resulting momentum and heat transfer are discussed in terms of various parameters, such as the radius ratio, the relative roughness, the roughness density, Nusselt number and Prandtl number.

  • PDF

Experimental Investigation on the Flow in Concentric Annuli with Both Rough Walls (내·외벽에 거칠기가 있는 이중동심관 유동에 대한 실험적 연구)

  • Ahn, S.W.;Jung, Y.B.;Kim, K.C.
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
    • /
    • v.7 no.1
    • /
    • pp.81-88
    • /
    • 1995
  • Fully developed turbulent flow through three concentric annuli with both the rough inner and outer walls was experimentally investigated for a Reynolds number range Re=15,000-85,000. Measurements were made of the pressure drop, the positions of zero shear stress and maximum velocity, and the velocity distributions in annuli of radius ratios, ${\alpha}=0.26$, 0.4 and 0.56, respectively. The experimental results showed that the positions of zero shear streess and maximum velocity were only weakly dependent on the Reynolds number. It was also found that the position of zero shear stress was not coincident with that of maximum velocity. Furthmore, the former was influenced more sensitively than the latter on the square-ribbed roughness along the axial direction.

  • PDF

A Study on the Turbulent Flow in Concentric Annuli with Both Rough Walls (양벽면에 거칠기가 있는 이중동심관내의 난류유동에 관한 연구)

  • 안수환;정양범
    • Journal of the Korean Society of Marine Engineering
    • /
    • v.18 no.3
    • /
    • pp.17-25
    • /
    • 1994
  • Fully developed turbulent flow through three concentric annuli with both the rough inner and outer walls was experimentally investigated for a Reynolds number range Re = 15, 000 - 85, 000. Measurements were carried out for the pressure drop, the positions of zero shear stress and maximum velocity, and the velocity distributions in annuli of radius ratios, ${\alpha}$=0.26, 0.4 and 0.56, respectively. The experimental results showed that the positions of zero shear stress and maximum velocity were only weakly dependent on the Reynolds number.

  • PDF

Turbulent Flow and Heat Transfer in an Annular Passage with Repeated-Ribbed Roughness on Both Walls (양측벽면에 반복돌출형 거칠기가 있는 이중관통로내의 난류운동과 열전달)

  • 안수환;이윤표
    • Transactions of the Korean Society of Automotive Engineers
    • /
    • v.4 no.5
    • /
    • pp.26-36
    • /
    • 1996
  • The fully developed turbulent momentum and heat transfer induced by the square-ribbed roughness elements on both the inner and outer wall surfaces in concentric annuli are studied analytically based on a modified turbulence model. The analytical results of the fuid flow are verified by experiment. The experiment is done with a pitot tube and a X-type hot wire anemometer to measure the time mean velocity profiles, zero shear stress positions, maximum velocity positions and friction factors, and etc. shown in Fig.1. The resulting momentum and heat transfer are discussed in terms of various parameters, such as the radius ratio, the relative roughness, the roughness density, Reynolds number, Nusselt bumber and Prand시 number. The study demonstrates that certain artificial roughness elements may be used to enhance heat transfer rates with advantage from the overall efficiency point of view by investigating turbulent flows and heat transfer in Fig.1.

  • PDF