• 대한기계학회논문집
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• 제15권6호
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• pp.2171-2180
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• 1991

본 연구에서는 구심터어빈의 설계시 많이 사용되고 있는 NASA의 안내깃 및 회 전익 손실모델들을 이용하여 PR과 K를 실험에 의존하지 않고 구하는 방법을 제시하고 자 한다. 그리고 이 방법을 가변 안내깃이 존재하거나 없는 가상의 구심터빈에 대하 여 탈설계 성능해석을 하여, 본 방법이 기존에 알려진 실험 현상과 유사한 경향을 보 이는지를 알아보기로 한다. 또한 안내깃이 있는 경우에 대하여 기존의 알려진 탈설 계 성능 예측용 프로그램과의 비교를 통하여 본 연구의 해석방법을 간접적으로 검증하 기로 한다.

• International Journal of Aeronautical and Space Sciences
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• 제18권2호
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• pp.186-196
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• 2017

In order to resolve the trimming difficulty in rotor CFD calculations, a high-efficiency and improved "delta trim method" is established to compute the blade control settings that are necessary to identify the blade motion. In this method, a simplified model which combines the blade element theory and different inflow models is employed to calculate the control settings according to the target aerodynamic forces, then it is coupled into a CFD solver with unsteady Navier-Stokes equations by the delta methodology, which makes the control settings and aerodynamics calculated and updated in the meantime at every trim cycle. Different from the previous work, the current research combines the inflow model based on prescribed wake theory. Using the method established, the control settings and aerodynamic characteristics of Helishape 7A, AH-1G and Caradonna-Tung rotors are calculated. The influence of different inflow models on trimming calculations is analyzed and the computational efficiency of the current "delta trim method" is compared with that of the "CFD-based trim method". Furthermore, for the sake of improving the calculation efficiency, a novel acceleration factor method is introduced to accelerate the trimming process. From the numerical cases, it is demonstrated that the current "delta trim method" has higher computational efficiency than "CFD-based trim method" in both hover and forward flight, and up to 70% of the amount of calculation can be saved by current "delta trim method" which turns out to be satisfactory for engineering applications. In addition, the proposed acceleration factor shows a good ability to accelerate the trim procedure, and the prescribed wake inflow model is always of better stability than other simple inflow models whether the acceleration factor is utilized in trimming calculations.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2011년도 춘계학술대회 초록집
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• pp.59.1-59.1
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• 2011

In this research, CFD calculation was implemented to analyze wind tunnel effect or rotor experiment in wind tunnel. One case included model wind turbine and all wind tunnel geometries. The other case include only rotor and nacelle system. Star-CCM+ was used for CFD analysis and rigid body motion around rotor area was applied to simulate rotating rotor. As for turbulence model, K-omega SST was used. The results were compared in 15m/s inflow condition. These results shows a good agreement with the measurement. Then, the result without wind tunnel was slightly different to the result with wind tunnel. Thus, in the case of Mexnex wind tunnel measurement, the wind tunnel don't affect the measurement result. Then, this wind tunnel and rotor size ratio can be reference for wind tunnel experiment of wind turbine rotor.

• 한국전산유체공학회지
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• 제18권3호
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• pp.60-66
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• 2013

Numerical simulation was performed for the rotor blade with fixed tab in hover using an unstructured mesh Navier-Stokes flow solver. The inflow and outflow boundary conditions using 1D momentum and 3D sink theory were applied to reduce computational time. Calculations were performed at several operating conditions of varying collective pitch angle and fixed tab length. The aerodynamic effect of fixed tab length was investigated for hovering efficiency, pitching moment and flapping moment of the rotor blade. The results show that it affects linearly increasing on the pitching moment of the rotor blade but does not affect on the flapping moment. The required power is less than 45kw for ground rotating test in hover. Numerical simulations also show that the vortex generate not only from the tip of the rotor blade but also from the fixed tab on the rotor blade.

• International Journal of Aeronautical and Space Sciences
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• 제10권2호
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• pp.125-133
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• 2009

To numerically simulate aerodynamics of rotor-airframe interaction in a rigorous manner, we need to solve the Navier-Stokes system for a rotor-airframe combination as a whole. This often imposes a serious computational burden since rotating blades and a stationary body have to be simultaneously dealt with. An efficient alternative is to adopt a momentum source method in which the action of rotor is approximated as momentum source over a rotor disc plane in a stationary computational domain. This makes the simulation much simpler. For unsteady simulation, the instantaneous momentum sources are assigned only to a portion of disk plane corresponding to blade passage. The momentum source is obtained by using blade element theory with dynamic inflow model. Computations are carried out for the simple rotor-airframe model (the Georgia Tech model) and the results of the simulation are compared with those of the full Navier-Stokes simulation with moving mesh system for rotor and with experimental data. It is shown that the present simulation yields results as good as those of the full Navier-Stokes simulation.

• International Journal of Aeronautical and Space Sciences
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• 제12권2호
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• pp.190-199
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• 2011

Unsteady flow simulations of complete helicopter configurations were conducted, and the flow fields and the aerodynamic interferences between the main rotor, fuselage, and tail rotor were investigated. For these simulations, a three-dimensional flow solver based on unstructured meshes was used, coupled with an overset mesh technique to handle relative motion among those components. To validate the flow solver, calculations were made for a UH-60A complete helicopter configuration at high-speed and low-speed forward flight conditions, and the unsteady airloads on the main rotor blade were compared to available flight test data and other calculated results. The results showed that the fuselage changed the rotor inflow distribution in the main rotor blade airloads. Such unsteady vibratory airloads were produced on the fuselage, which were nearly in-phase with the blade passage over the fuselage. The flow solver was then applied to the simulation of a generic complete helicopter configuration at various flight conditions, and the results were compared with those of the CAMRAD-II comprehensive analysis code. It was found that the main rotor blades strongly interact with a pair of disk-vortices at the outer edge of the rotor disk plane, which leads to high pulse airloads on the blade, and these airloads behave differently depending on the specific flight condition.

• 대한조선학회논문집
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• 제47권4호
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• pp.533-542
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• 2010

For a long times it has been believed that the Magnus effect of the rotating cylinder could be utilized for the lifting devices applicable to marine practices. It has been reported that the rotating cylinder installed on upper deck of commercial vessel could play a energy saving role however the idea might be applicable in a very rare case in ship building practices. In this study special high lift rudder system equipped with the trailing edge rotor has been suggested in correspondence with the increasing requirement of greater rudder force. Through the numerical simulation it is cleared that the trailing edge rotor could play a role in enhancement of circulation and refinement of boundary layer of the rudder system. At the same time it is found out that the lift force of the rudder system without rotation of trailing edge rotor could be doubled when the circumferential velocity of the trailing edge rotor is equal to twice of the inflow velocity.

• 한국항공우주학회지
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• 제39권6호
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• pp.487-497
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• 2011

자동회전 상태로 속도 증가 시 로터 속도의 변화와 피치 범위를 조사하기 위하여 수치 해석을 수행하였다. 정상 자동회전 상태를 구하기 위하여 과도모사법(Transient Simulation Method:TSM)을 사용하였다. 풍속의 증가에 대응하기 위하여 로터 블레이드를 2차원 압축성 Navier-Stokes 솔버로 해석하여 공력계수를 계산하였고 이를 과도모사법에 사용하였으며 유도 속도장 변화를 모사하기 위하여 Pitt/Peters 유도속도 이론을 적용하였다. 설정된 토크 평형 조건에서 풍속, 샤프트각, 피치각의 조합을 출력하여 로터의 회전속도와 변수의 범위를 조사하였다. 깃 끝 마하수의 변화에 따른 로터 회전속도의 변화를 살펴보았고 샤프트각의 감소에 따른 피치각의 트림 범위를 고찰하였다.

• 한국항공우주학회지
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• 제40권1호
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• pp.12-22
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• 2012

샤프트각이 감소하며 비행 속도가 증가하는 자동회전 상태의 로터에 대한 성능 변화를 해석하였다. BO-105 헬리콥터의 로터에 비틀림이 없는 NACA 0012 단면을 가지는 깃을 해석하였고 변수에 대한 자동회전의 영역을 구하기 위해 과도모사법(TSM)이 사용되었다. 고속 비행에서 압축성 효과를 모사하기 위해 압축성 Navier-Stokes 솔버로 해석된 2차원 공력 데이터가 사용되었으며 유도 속도장을 모사하기 위해 Pitt/Peters의 유도속도 이론이 사용되었다. TSM으로 구해진 정상 자동회전 상태에 대하여 추력계수와 양력계수, 양항비를 계산하였으며 로터의 양력과 동력을 구하여 BO-105 헬리콥터와 비교하였다. 복합 항공기의 개념을 도입할 때 자동회전하는 로터와 날개의 양력 및 동력 분담률을 고찰하였다.

• International Journal of Naval Architecture and Ocean Engineering
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• 제11권1호
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• pp.154-164
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• 2019

A rotor dynamic analysis is mandatory for stability and design optimization of submerged propellers and turbines. An accurate simulation requires a proper consideration of fluid-induced reaction forces. This paper presents a bi-directional coupling of a bond graph method solver and an unsteady vortex lattice method solver where the former is used to model the rotor dynamics of the power train and the latter is used to predict transient hydrodynamic forces. Due to solver coupling, determination of hydrodynamic coefficients is obsolete and added mass effects are considered automatically. Additionally, power grid and structural faults like grid fluctuations, eccentricity or failure could be investigated using the same model. In this research work a fast, time resolved dynamic simulation of the complete power train is conducted. As an example, the rotor dynamics of a tidal stream turbine is investigated under two inflow conditions: I - shear flow, II - shear flow + water waves.