• Title/Summary/Keyword: Vortical Flow

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PIV Velocity Field Measurements of Flow around a Ship with Rotating Propeller (PIV를 이용한 선박 프로펠러 후류의 속도장 계측)

  • 이상준;백부근
    • Journal of the Society of Naval Architects of Korea
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    • v.40 no.5
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    • pp.17-25
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    • 2003
  • Velocity field behind a container ship model with a rotating propeller has been investigated using PIV (particle image velocimetry) system. Four hundred instantaneous velocity fields were measured at 4 different blade phases and ensemble-averaged to investigate the spatial evolution of vortical structure of near wake within one propeller diameter downstream. The phase-averaged mean velocity fields show the potential wake and the viscous wake formed due to the boundary layers developed on the blade surfaces. The interaction between bilge vortex developed along the hull surface and the tangential velocity component of incoming flow causes to have asymmetric flow structure in the transverse plane.

NUMERICAL ANALYSIS OF THE GUST GENERATOR FOR KARI LOW SPEED WIND TUNNEL (KARI 중형 아음속 풍동용 돌풍 발생기의 수치해석)

  • Park Y. M.;Kwon K. J.;Lee S. W.;Kim T. W.
    • 한국전산유체공학회:학술대회논문집
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    • 2005.10a
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    • pp.275-279
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    • 2005
  • The vortex convection and induced flow field behind the KARI 3m x 4m LSWT gust generator was computed by using Computational Fluid Dynamics. For the accurate simulation of vortex convection, inviscid, laminar, Spalart-Allmars k-e and k-w turbulence models were tested with the NAL gust generator configuration and Spalart-Allmaras turbulence model was selected for the prediction of induced flow field behind the KARI LSWT gust generator. The wind tunnel test was also carried out at KARI LSWT and the results were compared with CFD prediction.

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NUMERICAL STUDY OF TURBULENT FLOW IN A INTAKE PART OF VACUUM CLEANER WITH ROLLING BRUSH (회전브러시가 장착된 진공청소기 흡입장치의 난류유동에 대한 수치해석)

  • Park, Tae-Seon
    • Journal of computational fluids engineering
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    • v.17 no.2
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    • pp.58-64
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    • 2012
  • Turbulent flows in a intake part of vacuum cleaner are studied by RANS simulations. The governing equations are solved by the SIMPLE algorithm based on the finite volume method of the unstructured grid system. The predicted results show that the suction performance is closely related to the variation of flow structure in the intake part. In order to investigate for the cleaning of bedclothes and carpet without sticking, several design changes are applied. The introduction of a solid cylinder in the intake part changes vortical structures significantly. Based on this result, a new design with spiral brushes is proposed. The design shows a good behavior for the suction performance and the flow control.

NUMERICAL ANALYSIS FOR STEADY ASYMMETRIC VORTEX OF CONE AT HIGH ANGLE OF ATTACK (고받음각에서 원뿔형 물체 주위에 발생하는 정상상태 비대칭 와류의 수치해석)

  • Park, M.Y.;Park, S.H.;Lee, J.W.;Byun, Y.H.
    • 한국전산유체공학회:학술대회논문집
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    • 2007.10a
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    • pp.171-176
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    • 2007
  • Supersonic viscous flow over a 5 degree half angle cone studied computationally with three-dimensional Navier-Stokes equations. Steady asymmetric solutions of 5-deg half angle cone show that the asymmetric flow separation is caused by convective instability. The angle of attack, Reynolds number, and Mach number affected the side force variation that is caused by asymmetric vortical flow.

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A Study on the Effect of Thermal Stratification of a Heated Cylinder Wake (가열된 원주후류의 열성층 영향에 대한 연구)

  • 김경천;정양범
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.18 no.9
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    • pp.2454-2462
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    • 1994
  • The effects of thermal stratification on the flow of a stratified fluid past a heated circular cylinder were examined in a wind tunnel. Turbulent intensities, rms values of temperature and turbulent convective heat flux distributions in the heated cylinder wake with and without thermal stratification were measured by using a hot-wire and cold-wire combination probe. A phase averaging method was also used to estimated coherent motion in the near wake. It is found that the vertical turbulent motion in the stably stratified flow case dissipates faster than that of the neutral case, i.e., vertical growth of vortical structure is suppressed under the strongly stratified condition. The coherent motion of temperature makes a large contribution like velocity coherent motion. However, the coherent motions of temperature fluctuation become very different with the change of experimental conditions, though the velocity coherent motions are quite similar in all experimental conditions.

Secondary flow Control in the Turbine Cascade with the Three-Dimensional Modification of Blade Leading Edge (블레이드 앞전 3차원 형상 변형에 의한 터빈 캐스케이드 내의 이차유동 제어)

  • Kim, Jeong-Rae;Moon, Young-June;Chung, Jin-Tack
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.26 no.11
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    • pp.1552-1558
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    • 2002
  • The blade leading edge is modified to control the secondary flow generated in the turbine cascade with fence by intensifying the suction side branch of the horseshoe vortex. The incompressible Navier-Stokes equations are numerically solved with a high Reynolds number k-$\varepsilon$ turbulence closure model for investigating the vortical flows in the turbine cascade. The computational results of total pressure loss coefficients in the wake region are first compared with experiments for validation. The structure and strength of the passage vortex near the suction surface are examined by testing various geometrical parameters of the turbine blade leading edge.

Computational Study of the Vortical Flow over a Yawed LEX-Delta Wing at a High-Angle of Attack (고영각 Yawed LEX-Delta 익에서 발생하는 와유동의 수치해석)

  • Kim, Tae-Ho;Kweon, Yong-Hun;Kim, Heuy-Dong;Sohn, Myong-Hwan
    • Proceedings of the KSME Conference
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    • 2003.04a
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    • pp.2109-2114
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    • 2003
  • The vortex flow characteristics of a yawed LEX-delta wing at a high-angle of attack are studied using a computational analysis. The objective of the present study is to investigate and visualize the effects of the yaw angle, the development and interaction of vortices, the relationship between the suction pressure distributions and the vortex flow characteristics. Computations are applied to the three dimensional, compressible, Navier-Stokes Equations. In computations, the yaw angle is varied between 0 and 20 degree at a high-angle of attack. Computational predictions are compared with the previous experimental results.

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A Study on the Chattering Phenomena of a Check Valve (역지밸브 채터링 현상 해소방안 연구)

  • 유기완;이준신;김태룡
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.12 no.1
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    • pp.36-41
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    • 2002
  • The cause and the elimination method for the chattering phenomena were investigated in a check valve attached to the exit of an auxiliary cooling water pump in a Korean nuclear powerplant. From the site experiment and the numerical calculation, the incident angle of the disk was so small that it was not able to produce the sufficient lifting force to overcome the gravitational component of the disk weight. Moreover, it turned out that the installation position was not symmetric for the secondary vortical flow generated inside the elbow so that the flow structure had strongly unstable flow characteristics. From this study, the tapping noise and the chattering phenomena were eliminated exactly by changing the incidence angle of the valve disk and the installation position of the calve body.

A stydy on the chattering noise elimination of the check valve (역지 밸브 채터링 해소방안 연구)

  • Ryu, Ki-Wahn;Lee, Jun-Shin;Kim, Tae-Ryong;Kim, Kyoung-Ku
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2000.06a
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    • pp.1848-1853
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    • 2000
  • Cause and the elimination method for the chattering phenomena were investigated the check valve attached exit of the auxiliary cooling water pump at a korean nuclear powerplant. From the site experiment and numerical calculation the incident angle of the disk was so small that it was not able to produce the lifting force to overcome the component of disk weight. Moreover, it turned out that the installed position was not symmetric for the secondary vortical flow generated inside the elbow, so that the flow structure had strongly unstable flow characteristics. From this technical support, the tapping noise and the chattering phenomena were eliminated exactly by changing the incidence angle of the valve disk and installed position of the check valve.

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Kernel-Based Fuzzy Regression Machine For Predicting Turbulent Flows

  • Hong, Dug-Hun;Hwang, Chang-Ha
    • 한국데이터정보과학회:학술대회논문집
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    • 2004.04a
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    • pp.91-101
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    • 2004
  • The turbulent flow is of fundamental interest because the conservation equations for thermodynamics, mass and momentum are linked together. This turbulent flow consists of some coherent time- and space-organized vortical structures. Research has already shown that some dynamic systems and experimental models still cannot provide a good nonlinear analysis of turbulent time series. In the real turbulent flow, very complicated nonlinear behaviors, which are affected by many vague factors are present. In this paper, a kernel-based machine for fuzzy nonlinear regression analysis is proposed to predict the nonlinear time series of turbulent flows. In order to show the practicality and usefulness of this model, we present an example of predicting the near-wall turbulence time series as a verifiable model and compare with fuzzy piecewise regression. The results of practical applications show that the proposed method is appropriate and appears to be useful in nonlinear analysis and in fuzzy environments to predict the turbulence time series.

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