• The Journal of the Acoustical Society of Korea
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• v.21 no.2
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• pp.134-141
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• 2002

In this paper, a free wake analysis based on the curved vortex element and CVC wake model is used to predict the aerodynamic performance and noise for HAWT. Also for prediction of RPM, a maximum value through a quadratic regression was suggested. And for a noise prediction, the broadband noise prediction method based on experimental equation was used. The curved vortex element uses a BCVE and an SIVE instead of a straight vertex element. In the CVC wake model, the vortex strengths are assumed to be constant along a span and a vortex filament. The free wake structure made by the curved vortex element and CVC was substituted for a vortex lattice, so it has an advantage for the less calculation time and a depiction of accurate wake structure. For the verification of this program, calculated results are compared with Mr. Kim's experiment model and Zond Z-40FS for performance and with WTS-4 and USWP models for noise. Good agreements are obtained between the predicted and the measured data for the performance and far-field noise spectra.

• Transactions of the Korean Society of Mechanical Engineers
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• v.11 no.6
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• pp.877-883
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• 1987

A new improved inviscid separation model to calculate the mean flow past circular cylinders is proposed. The wake region is modeled by a pair of vortex sheets which emerge from the separation points and are allowed to move freely with the local stream. The vortex strength assumes a constant value for some initial distance which is related to the pressure drag and gradually decreases to zero as the sheet moves farther away from the body. This vorticity distribution automatically takes care of the length parameter which has been one of the deficiencies in the existing models. The procedure is tested against various experimental data and the agreement is quite good for both sub and super-critical regimes. The comparison with an existing model is also given.

• Proceedings of the KIEE Conference
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• 2003.04a
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• pp.373-375
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• 2003

상반회전 풍력발전 시스템의 경우 전방에 위치한 로터의 후류 효과를 적절히 반영하여 설계에 이용해야 한다. 본 연구에서는 이러한 로터의 후류효과 및 블레이드의 실속후 모델을 고려하여 30kW급 상반회전시스템의 설계형상에 대한 검토연구를 수행하였다 기본공력이론은 모멘텀 이론과 2차원 준정상 공기력 이론을 통합한 형태를 사용하였다. 로터의 후류영향을 고려하기 위해 축소형 풍차 블레이드 모델에 대한 풍동시험 결과를 적절히 이용하며, 이로부터 보조로터를 지난 후류의 축속도 및 각속도 성분을 결정하였다. 최종적으로 상반회전 시스템의 로터 반경 및 상호 이격거리 등을 고려한 성능해석을 수행하고 이로부터 최적 설계형상에 대한 파라미터 연구결과를 제시하였다.

• 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.

• 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.

• 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.

• 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 $P_s/ P_r= 1.0$.

• Journal of the Korean Society of Marine Environment & Safety
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• v.20 no.6
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• pp.760-767
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• 2014

An experimental study is carried out to investigate the effect of jet stream in the gab of rectangular cylinders with different length in a parallel arrangement by using PIV method in a circulating water channel. The height(h) of the rectangular cylinder and the gap between the cylinder is 10mm, and the width(B) which is 300mm. The length of the model for flow direction was applied to 30mm, 60mm, 90mm & 120mm, The aspect ratio of a model on the basis of height(H=30mm) is 1, 2, 3 and 4. Reynolds number $Re=1.4{\times}10^4$, $Re=2.0{\times}10^4$, $Re=2.9{\times}10^4$ based on the height(H) of model for the distance of tidal distributions as of water depth have been applied during the whole experiments. The measurement area was set to 5H rear of the cylinder. As a result, Vortex size in the wake area were increased as velocity increased. and high aspect ratio increased through-flow velocity component in the near wake. Velocity deficit increased highly after near-wake area and low aspect ratio.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.35 no.2
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• pp.124-129
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• 2007

Prediction methods for a rotor averaged inflow in forward flight are investigated in this study. The investigated methods are Drees linear inflow model, Mangler & Squire model and free vortex wake(FVW) method. Predictions have been performed for a four-blade rotor operating at three different advance ratios i.e. 0.15, 0.23 and 0.30, at which experimental data are available. According to results, Drees model has a limitation for the inflow non-uniformity prediction due to an inherent linear characteristics. Mangler & Squire model has a reasonable accuracy except the disk edge region. KARI FVW method has very good accuracy and has better accuracy than the other FVW method especially in inboard region. However, there are some discrepancies in retreating side due to the dynamic stall effect and in near hub region due to the fuselage upwash effect.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.2
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• pp.156-162
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• 2008

The static aeroelastic analysis of composite hingeless rotor blades in hover was performed using free-wake method. Large deflection beam theory was applied to analyze blade motions as a one-dimension beam. Anisotropic beam theory was applied to perform a cross-sectional analysis for composite rotor blades. Aerodynamic loads were calculated through a three-dimensional aerodynamic model which is based on the unsteady vortex lattice method. The wake geometry in hover was described using a time-marching free-wake method. Numerical results of the steady-state deflections for the composite hingeless rotor blades were presented and compared with those results based on two-dimensional quasi-steady strip theory and prescribed wake method. It was shown that wakes affect the steady-state deflections.