• Title/Summary/Keyword: Flux-difference splitting

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Flow Control on Wind Turbine Airfoil with a Vortex Cell (와류 셀을 이용한 풍력블레이드 에어포일 주위 유동 제어)

  • Kang, Seung-Hee;Kim, Hye-Ung;Ryu, Ki-Wahn;Lee, Jun-Shin
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.40 no.5
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    • pp.405-412
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    • 2012
  • A flow control on airfoil installed a vortex cell for high efficiency wind turbine blade in stationary and dynamic stall conditions have been numerically investigated by solving the compressible Navier-Stokes equations. The numerical scheme is based on a node-based finite-volume method with Roe's flux-difference splitting and an implicit time-integration method coupled with dual time step sub-iteration. The computed result for the airfoil in the stationary showed that lift-drag ratio increases due to low pressure by the vortex cell. The oscillating airfoil with the vortex cell showed that the magnitude of hysteresis loop is reduced due to the enhanced vortex in the cell.

Numerical Analysis of Flowfield over Various Blunt-bodies Using Upwind Navier-Stokes Method (Upwind Navier-Stokes 방법을 이용한 다양한 무딘물체 유동장의 수치 해석적 연구)

  • Seo Jeong-Il;Song Dong-Ju
    • 한국전산유체공학회:학술대회논문집
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    • 1998.11a
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    • pp.78-83
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    • 1998
  • A finite-difference method based on conservative supra characteristic method(CSCM) type upwind flux difference splitting has been studied on the bluntness effect on the wall heat transfer rate and wall pressure over blunt-body. The results show that the stagnation heating varies inversely with the square root of the nose radius.

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A Preconditioning Method for Two-Phase Flows with Cavitation

  • Shin B.R.;Yamamoto S.
    • 한국전산유체공학회:학술대회논문집
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    • 2003.10a
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    • pp.181-182
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    • 2003
  • A preconditioned numerical method for gas-liquid to-phase flow is applied to solve cavitating flow. The present method employs a density based finite-difference method of dual time-stepping integration procedure and Roe's flux difference splitting approximation with MUSCL-TVD scheme. A homogeneous equilibrium cavitation model is used. The method permits simple treatment of the whole gas-liquid two-phase flow field including wave propagation, large density changes and incompressible flow characteristics at low Mach number. By this method, two-dimensional internal flows through a venturi tuve and decelerating cascades are computed and discussed.

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NUMERICAL INVESTIGATION OF INTERACTION BEHAVIOR BETWEEN CAVITATION BUBBLE AND SHOCK WAVE

  • Shin, Byeong-Rog;An, Young-Joon
    • 한국전산유체공학회:학술대회논문집
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    • 2008.03a
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    • pp.215-220
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    • 2008
  • A numerical method for gas-liquid two-phase flow is applied to solve shock-bubble interaction problems. The present method employs a finite-difference Runge-Kutta method and Roe's flux difference splitting approximation with the MUSCL-TVD scheme. A homogeneous equilibrium cavitation model is used. By this method, a Riemann problem for shock tube was computed for validation. Then, shock-bubble interaction problems between cylindrical bubbles located in the liquid and incident liquid shock wave are computed.

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NUMERICAL INVESTIGATION OF INTERACTION BEHAVIOR BETWEEN CAVITATION BUBBLE AND SHOCK WAVE

  • Shin, Byeong-Rog;An, Young-Joon
    • 한국전산유체공학회:학술대회논문집
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    • 2008.10a
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    • pp.215-220
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    • 2008
  • A numerical method for gas-liquid two-phase flow is applied to solve shock-bubble interaction problems. The present method employs a finite-difference Runge-Kutta method and Roe's flux difference splitting approximation with the MUSCL-TVD scheme. A homogeneous equilibrium cavitation model is used. By this method, a Riemann problem for shock tube was computed for validation. Then, shock-bubble interaction problems between cylindrical bubbles located in the liquid and incident liquid shock wave are computed.

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Performance Analysis of Three-Dimensional Transonic Centrifugal Compressor Diffuser (3차원 천음속 원심압축기 디퓨저 성능연구)

  • Kim, Sang-Dug;Song, Dong-Joo
    • The KSFM Journal of Fluid Machinery
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    • v.2 no.1 s.2
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    • pp.64-72
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    • 1999
  • CSCM upwind flux difference splitting compressible Navier-Stokes method has been used to predict the transonic flows in a centrifugal compressor diffuser. The modified cyclic. TDMA and the mass flux boundary conditions were used as boundary conditions of the diffuser analysis. Broad flow separation on the suction surface near the hub and shroud was observed from the results of the mass flow rates 5.8, 6.0 and 6.2kg/s at 27000 rpm. The three-dimensional flow analysis predicted successfully that the static pressure increased and the total pressure decreased through the flow passage of the channel diffuser when compared to two-dimensional analysis due to the strong effect of the three-dimensional flow. The mass averaged loss coefficients and pressure coefficients were also studied.

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NUMERICAL STUDY OF MODEL AND WALL INTERFERENCE IN A SUPERSONIC WIND TUNNEL (초음속 풍동내에서의 모델과 벽면 간섭에 관한 수치적 연구)

  • Hong S. K.;Ahn H. K.
    • 한국전산유체공학회:학술대회논문집
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    • 1995.10a
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    • pp.213-218
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    • 1995
  • 마하수 4일때 초음속 풍동의 벽면과 모델지지부의 간섭에 관해 연구하였다. 특히 모델지지부 주위에서의 충격파 형성과 sting, strut 그리고 second throat에서의 반사 충격파의 상호 작용에 연구의 촛점을 두었다. 수치 기법은 내재적 플럭스 차분 분할기법 (implicit flux-difference splitting technique)을 사용하였다. 2차원과 3차원 유동해석 결과로부터 모델지지부 후류의 유동에 미치는 diffuser 출구 경계조건의 영향을 알아보았다.

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Application of Characteristic Boundary Conditions

  • Hong Seung Gyu;Lee Gwang Seop
    • 한국전산유체공학회:학술대회논문집
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    • 1996.05a
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    • pp.74-84
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    • 1996
  • Characteristic boundary conditions are discussed in conjunction with a flux-difference splitting formulation as modified from Roe's linearization. Details of how one can implement the characteristic boundary conditions which are compatible with the discrete formulation at interior points are given for different types of boundaries including subsonic outflow and adiabatic wall. The latter conditions are demonstrated through computation of supersonic ogive-cylinder flow at high angle of attack and the computed wall pressure distribution is compared with experiment.

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Unsteady Wall Interference Effect on Flows around a Circular Cylinder in Closed Test-Section Wind Tunnels (폐쇄형 풍동 시험부내의 원형 실린더 유동에 대한 비정상 벽면효과 연구)

  • Kang, Seung-Hee;Kwon, Oh-Joon;Hong, Seung-Kyu
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.33 no.7
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    • pp.1-8
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    • 2005
  • For study on the unsteady wall interference effect, flows around a circular cylinder in closed test-section wind tunnels have been numerically investigated by solving compressible Navier-Stokes equations. The numerical scheme is based on a node-based finite-volume method with the Roe's flux-difference splitting and an implicit time-integration method coupled with dual time-step sub-iteration. The computed results showed that the unsteady pressure gradient over the cylinder is enhanced by the wall interference, and as a result the fluctuations of lift and drag are augmented. The drag is further increased because of the lower base pressure. The vortex shedding frequency is also increased by the wall interference. The pressure on the test section wall shows the harmonics having the shedding frequency contained in the wall effect.

Performance Analysis of Three-Dimensional Transonic Centrifugal Compressor Diffuser (3차원 천음속 원심압축기 디퓨져 성능연구)

  • Kim, Sang Dug;Song, Dong Joo
    • 유체기계공업학회:학술대회논문집
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    • 1998.12a
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    • pp.217-222
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    • 1998
  • CSCM upwind flux difference splitting compressible Navier-Stokes method has been used to predict the transonic flows in centrifugal compressor diffuser. The modified cyclic TDMA and the mass flux boundary conditions were used as boundary conditions of the diffuser analysis. With the mass flux boundary condition and the $130{\times}80{\times}40$ grid, the compressible upwind Navier-Stokes method predicted the transonic diffuser flowfield successfully. Plow changes in the impeller exit region due to the strong interaction between impeller exit and vaned diffuser, broad flow separation on the suction surface near hub and shroud was observed from the results of the mass flow rates 6.0 and 6.2kg/s at 27000 rpm. The static pressure increased and the total pressure decreased through the flow passage of the channel diffuser, which were predicted better from the three-dimensional analysis than from the two-dimensional analysis due to the strong effect of the three-dimensional flow. The mass averaged loss coefficients and pressure coefficients were also studied.

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