• Title/Summary/Keyword: 비정상 후류

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The Effect of Trailing Wake Asymmetry on a Propeller Blade Forces in Inclined Inflow (비대칭 후류를 고려한 경사축 추진기의 유동해석)

  • Sang-Woo Pyo
    • Journal of the Society of Naval Architects of Korea
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    • v.35 no.1
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    • pp.24-31
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    • 1998
  • Unsteady propeller blade forces arising from shaft inclination have been found to be an important contribution tn total blade forces. The position of the wake relative to a blade oscillates with the first blade frequency, thus giving rise to unsteady blade forces which is significant relative to the forces produced directly by flow inclination. In order to find a wake geometry due to shaft inclination, a non-axisymmetric wake model is developed and applied to a specific case, which has experimental values. Predicted cavity shapes and unsteady forces acting on the blades of an inclined shaft propeller are compared to those predicted by other numerical methods, as well as those measured in experiments.

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The Aerodynamic Analysis of Helicopter Rotors by Using an Unsteady Source-Doublet Panel Method (비정상 Source-Doublet 패널 기법을 이용한 헬리콥터 로터 공력 해석)

  • 이재원;오세종;이관중
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.34 no.6
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    • pp.1-9
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    • 2006
  • 본 연구의 목적은 여러 가지 비행 모드 상의 로터 성능을 효율적으로 예측하는 것이다. 헬리콥터의 공력 특성을 예측하기 위한 비정상 source-doublet 패널 기법 기반의 수치 기법을 개발하였다. 후류의 형상 예측에는 시간 전진 자유후류모델이 사용되었다. 점성에 의한 확산을 고려한 후류의 roll-up 모사를 위하여 후류의 doublet 패널은 같은 강도의 와류고리로 대체하여 계산하였다. 후류와 양력면의 충돌 문제는 표면격자 내부에 들어간 와류고리의 포텐셜값을 제거하여 해결하였다. 제자리비행의 해석 시에 나타나는 와류 불안정성의 해결에는 slow starting과 vortex core growth 모델을 사용하였다. 로터 공력 해석 프로그램은 제자리비행과 전진비행에 대한 실험 결과와 비교하여 검증하였으며, 실험치와 일치하는 결과를 얻을 수 있었다.

Simulation of Unsteady Rotor-Fuselage Interaction Using an Improved Free-Wake Method (향상된 자유후류 기법을 이용한 비정상 로터-동체 상호작용 시뮬레이션)

  • Lee, Joon-Bae;Seo, Jin-Woo;Lee, Jae-Won;Yee, Kwan-Jung;Oh, Se-Jong
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.38 no.7
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    • pp.629-636
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    • 2010
  • This study is to investigate the aerodynamic effects of the Rotor-Fuselage Interactions in forward flight, and is conducted by using an improved time-marching free-wake panel method. To resolve the instability caused by the close proximity of the wake to the blade surface, the field velocity approach is added to the prior unsteady panel code. This modified method is applied to the ROBIN(ROtor Body Interaction) problem, which had been conducted experimentally in NASA. The calculated results, pressure distribution on fuselage surface and induced inflow ratio without and with the rotor, are compared with the experimental results. The developed code shows not only very accurate prediction of the aerodynamic characteristics for the rotor-fuselage interaction problem but also the rotor wake development.

An Analysis of BVI Unsteady Rotor Aerodynamics using Unsteady Panel and Time-Marching Free Wake (비정상 패널 및 시간전진 자유후류를 이용한 BVI 비정상 로터 공력 해석)

  • Wie, Seong-Yong;Lee, Duck-Joo
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.37 no.4
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    • pp.329-335
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    • 2009
  • The unsteady panel and time-marching free wake are applied to the rotor aerodynamics and wake behaviour. Numerical results of panel and free wake are compared and validated with experimental data. Using these methods, unsteady rotor aerodynamics in BVI condition is analyzed and discussed in detail.

Development of a free wake model to analyze HA WT blade airload under asymmetry condition (수평축 풍력블레이드의 비대칭 환경에서의 공력 해석을 위한 자유후류기법에 관한 연구)

  • Shin, Hyung-Ki;Park, Ji-Woong;Lee, Soo-Gab;Kim, Seok-Woo
    • 유체기계공업학회:학술대회논문집
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    • 2006.08a
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    • pp.411-414
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    • 2006
  • 풍력 발전기의 블레이드는 다른 회전기와는 달리 항상 지면의 경계층, 요-에러에 의한 어긋난 유입류, 타워와의 간섭효과의 환경에서 운영된다. 따라서 정상운전상태에서도 이와 같은 환경에서 겪게 되는 공력하중의 해석이 블레이드의 설계에서 중요하게 요구된다. 본 연구에서는 이의 비정상 공력하중해석을 위하여 자유후류기법을 이용한 방법을 연구하였다. 특히, 타워와의 간섭해석을 위하여 FVE라 명명한 후류 모델을 개발하여 적용하였다.

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Study for Aerodynamic and Aeroacoustic Characteristics of Multirotor Configurations Considering the Wake Interaction Effect (멀티로터형 비행체의 후류 상호작용을 고려한 공력 및 공력소음 해석 연구)

  • Ko, Jeongwoo;Kim, Dong Wook;Lee, Soogab
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.47 no.7
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    • pp.469-478
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    • 2019
  • Multirotor configurations such as VTOL and urban air mobility have been focused on today due to the high maneuverability. Aerodynamic and aeroacoustic characteristics of multirotor have much difference to those of a single rotor. In this study, a numerical analysis based on the free wake vortex lattice method is used for identifying the wake interaction effect. In order to compare the various configurations and operating conditions, the effects of the spacing between the rotors in hovering flight and the effects of the advancing ratio and the formation in forward flight are discussed. In the hovering flight, the unsteady loading of multirotor changes periodically and loading fluctuation increases as decreasing the spacing. It causes the variation in unsteady loading noise and the noise directivity pattern. In the forward flight, the difference in loading fluctuation and noise characteristics are observed according to the diamond and square formation of rotors. By comparing with results of single rotor analysis, multirotor configurations have different directivity pattern and amplitude of loading noise according to the location of each rotor. As a result, wake interaction effect becomes a highly important factor for aerodynamic and aeroacoustic analysis according to multirotor configurations and operating conditions.

Unsteady Flow Fields in a Rotor Blade Passage by Wake Passing (회전익 채널내 후류장에 의한 비정상 유동특성에 관한 연구)

  • Kim, Youn J.;Jeon, Y.-R
    • The KSFM Journal of Fluid Machinery
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    • v.2 no.4 s.5
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    • pp.16-23
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    • 1999
  • The characteristic of unsteady flowfields on gas turbine, particularly on a rotor blade surface has been numerically investigated. The unsteady flow in a rotor blade passage as a result of wake/blade interaction is modeled by the inviscid flow approach, and solved by Euler equations using a time accurate marching scheme. Unsteady flow in the blade passage is induced by periodically moving a wake model across the passage inlet. The wake model used in this study is the Gaussian wate model in which the wake flow is assumed to be parallel with uniform static pressure and uniform relative total enthalpy. Numerical results show that for the case of Ps/Pr=1.5, the velocity and pressure distribution on the blade surfaces have much more complex profiles than for the case of Ps/Pr=1.0.

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A Numerical Analysis of Unsteady Flow in a Rotor Blade Passage by Wake Passing (후류장에 의한 가스터빈 회전익 통로내 비정상 유동의 수치해석적 연구)

  • Kim, Youn J.;Jeon, Y. R.
    • 유체기계공업학회:학술대회논문집
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    • 1998.12a
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    • pp.233-239
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    • 1998
  • The effects of unsteady flow on gas turbine, particularly on a rotor blade surface are numerically investigated. The unsteady flow in a rotor blade passage as a result of wake/blade interaction is modeled by the inviscid flow approach, and solved by the Euler equations using a time accurate marching scheme, Numerical results show that for the case of $P_s/ P_r= 1.5$, the velocity and pressure distribution on the blade surfaces have much more complex profiles than those of $P_s/ P_r= 1.0$.

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Unsteady flow analysis around a circular cylinder using EDISON CFD (EDISON CFD를 이용한 원형 실린더 주위의 비정상 유동 해석)

  • Kim, Jae-Min;Jin, Seong-Ho;Kim, Taek-Gi;Kim, Mun-Sang
    • Proceeding of EDISON Challenge
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    • 2012.04a
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    • pp.61-64
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    • 2012
  • 원형 실린더 주위의 비정상 유동은 공학적으로 매우 중요한 유동 현상으로서 2차원 원형 실린더 주위의 비정상 유동 현상인 와류 흘림에 관해 수치적으로 계산해 보고 실제 유동 현상과 비교해 본다. 또한 실린더 주위 유동의 와류 흘림 현상이 공학적인 측면에서 어떠한 중요한 역할을 하는지 고찰해 본다.

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Development and Validations of the Aerodynamic Analysis Program of Multi-Rotors by Using a Free-Wake Method (자유후류 기법을 이용한 다중로터 공력해석 프로그램의 개발 및 검증)

  • Park, Sang-Gyoo;Lee, Jae-Won;Lee, Sang-Il;Oh, Se-Jong;Yee, Kwang-Jung
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.35 no.10
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    • pp.859-867
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    • 2007
  • The objective of this study is to develop and validate a numerical method which can handle the multi-rotor aerodynamic characteristics. For the purpose of power estimation, table look-up method is implemented to the existing unsteady panel code that is coupled with a time-marching free wake model. Also, the Reynolds number scaling is implemented for the application to various regions of Reynolds number. The computed results are validated against the available experimental data for coaxial and tandem rotors. In the validation case for the coaxial rotor, more accurate result is acquired when the thickness effect is considered. The wake instability problem occurs at a particular separation distance between the rotors for tandem rotors. The wake instability is avoided by setting the single-rotor wake geometry as the initial wake geometry for the multi-rotor analysis. The estimated result for rotor separation effect is compared with the result of the momentum theory.