• Title/Summary/Keyword: 정지비행

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Validation of Rotor Aeroacoustic Noise in Hovering and Low Speed Descent Flight (정지 및 저속 하강 비행하는 헬리콥터 로터의 소음 해석 및 검증)

  • You, Younghyun;Jung, Sung Nam
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.43 no.6
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    • pp.516-525
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    • 2015
  • In this paper, the acoustic pressure of a helicopter rotor in hovering and low speed descent flight is predicted and compared with experimental data. Ffowcs Williams-Hawkings equation is used to predict the acoustic pressure. Two different wind tunnel test data are used to validate the predicted results. Boeing 360 model rotor test results are used for the low-frequency noise in hover, and HART II test results are employed for the mid-frequency noise, especially BVI noise, in low speed descent flight. A simple free-wake model as well as the state-of-the-art CFD/CSD coupling method are adopted to perform the analysis. Numerical results show good agreement against the measured data for both low-frequency and mid-frequency harmonic noise signal. The noise carpet results predicted using the FFT(Fast Fourier Transform) shows also reasonable correlation with the measured data.

Spherical Flying Machine Development (구형무인비행체 개발)

  • Kim, Jin-Won;Ryu, Dong-Young;Cho, Dong-Hyun;Moon, Sung-Tae
    • Aerospace Engineering and Technology
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    • v.11 no.2
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    • pp.158-163
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    • 2012
  • Spherical Flying Machine, unlike conventional aircraft structure, is protected by circular frame. This battery-operated propeller machine, which can do vertical take-off and hovering, is under development for indoor and outdoor operation and dubbed as Flying Ball in KARI. In the future, autonomous air vehicle will be constructed for reconnaissance and surveillance application.

Flow Control of Smart UAV Airfoil Using Synthetic Jet Part 1 : Flow control in Hovering Mode Using Synthetic Jet (Synthetic jet을 이용한 스마트 무인기(SUAV) 유동제어 Part 1 : 정지 비행 모드에서 synthetic jet을 이용한 유동제어)

  • Kim, Min-Hee;Kim, Sang-Hoon;Kim, Woo-Re;Kim, Chong-Am;Kim, Yu-Shin
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.37 no.12
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    • pp.1173-1183
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    • 2009
  • In order to reduce the download around the Smart UAV(SUAV) at hovering, flow control using synthetic jet has been performed. Many of the complex tilt rotor flow features are captured including the leading and trailing edge separation, and the large region of separated flow beneath the wing. In order to control the leading edge and trailing edge separation, synthetic jet is located at 0.01c, $0.3c_{flap}$, $0.95c_{flap}$. As non-dimensional frequency, the flow pattern is altered and the rate of drag reduction is changed. The results show that synthetic jets shorten the vortex period and decrease the vortex size by changing local flow structure. By using leading edge jet and trailing edge jet, download is efficiently reduced compared to no control case at hovering mode.

Real-Time Flight Testing for Developing an Autonomous Indoor Navigation System for a Multi-Rotor Flying Vehicle (실내 자율비행 멀티로터 비행체를 위한 실시간 비행시험 연구)

  • Kim, Hyeon;Lee, Deok Jin
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.40 no.4
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    • pp.343-352
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    • 2016
  • A multi-rotor vehicle is an unmanned vehicle consisting of multiple rotors. A multi-rotor vehicle can be categorized as tri-, quad-, hexa-, and octo-rotor depending on the number of the rotors. Multi-rotor vehicles have many advantages due to their agile flight capabilities such as the ability for vertical take-off, landing and hovering. Thus, they can be widely used for various applications including surveillance and monitoring in urban areas. Since multi-rotors are subject to uncertain environments and disturbances, it is required to implement robust attitude stabilization and flight control techniques to compensate for this uncertainty. In this research, an advanced nonlinear control algorithm, i.e. sliding mode control, was implemented. Flight experiments were carried out using an onboard flight control computer and various real-time autonomous attitude adjustments. The feasibility and robustness for flying in uncertain environments were also verified through real-time tests based on disturbances to the multi-rotor vehicle.

액체추진로켓 엔진의 추진제 공급배관에서의 수격현상 해석

  • 정태규;이중엽;한상엽;김영목
    • Bulletin of the Korean Space Science Society
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    • 2004.04a
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    • pp.79-79
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    • 2004
  • 액체추진로켓 엔진의 추진제 공급 배관은 비행 중 비상상황에 따른 엔진 정지 및 비행종료 후의 엔진 정지 시에 밸브의 급격한 차단에 따라 수격현상이 발생한다. 따라서 추진제 공급배관 및 밸브는 이러한 압력에 견딜 수 있게 설계되어야 한다. 또한 무게를 줄여야 하기 때문에 정확한 최대압력을 예측하여 설계하는 것이 필요하다. 일반적으로 배관의 수격현상은 밸브의 개폐 시간에 가장 큰 영향을 받는 것으로 알려져 있다. (중략)

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PERFORMANCE ANALYSIS OF HOVERING UH-60A ROTOR BLADE (UH-60A 로터 블레이드의 정지비행 성능해석)

  • Park, Y.M.;Choi, I.H.;Chang, B.H.
    • Journal of computational fluids engineering
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    • v.13 no.4
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    • pp.45-49
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    • 2008
  • The present paper describes the results of performance analysis for UH-60A rotor blade in hover. For the numerical simulations, commercial CFD software, FLUENT was used with Spalart-Allmaras turbulence model. The flow solver was based on node based scheme and second order spatial accuracy options was used for simulations. For the enhancement of wake capturing capability, high resolution grid was used around tip vortex region. Granting that somewhat over-prediction of thrust was observed near blade tip region, performance was well correlated with experimental data within 3% accuracy in the operating region. Finally it was shown that the present flow solver can be used as a preliminary performance analysis tool for hovering helicopter rotor blades.

PERFORMANCE ANALYSIS OF HOVERING UH-60A ROTOR BLADE (UH-60A 로터 블레이드의 정지비행 성능해석)

  • Park, Y.M.;Chang, B.H.;Chung, J.D.
    • 한국전산유체공학회:학술대회논문집
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    • 2007.10a
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    • pp.73-76
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    • 2007
  • The present paper describes the results of performance analysis for UH-60A rotor blade in hover. For the numerical simulations, commercial CFD software, FLUENT was used with Spalart-Allmaras turbulence model. The flow solver was based on node based scheme and second order spatial accuracy options was used for simulations. For the enhancement of wake capturing capability, high resolution grid was used around tip vortex region. Granting that somewhat over prediction of thrust was observed near blade tip region, performance was well correlated with experimental data within 3% accuracy in the operating region. Finally it was shown that the present flow solver can be used for preliminary performance analysis tool for hovering helicopter rotor blades.

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Validation of Noise Prediction Theory Using Scaled Rotor Experiment for Hovering Condition (정지비행 조건에서의 축소 로터 실험을 통한 소음 예측 기법 검증)

  • Min, An-Ki;Ryi, Jae-Ha;Rhee, Wook;Choi, Jong-Soo
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.40 no.3
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    • pp.201-208
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    • 2012
  • In this paper, a series of experiment is performed for a scaled hovering rotor in a semi-anechoic chamber and the results are compared to the noise spectra predicted by using Lowson's loading noise equation and FW-H equation. It was founded that the sound directivity pattern for both experiments and predictions are similar in their trend. Meanwhile the FW-H equation showed better agreement with experiments in the near-field noise spectra, but at the far-field the Lowson's equation performed better. The discrete noise are known to be proportional to the loading on the blades, which can be controlled by collective pitch angle of the blades. It was founded that the predicted spectra with FW-H equation come close to the measured noise spectra in low collective pitch, but in high collective pitch angles the Lowson's equation be more reliable.

Simulator Development for GEO (Geostationary Orbit)-Based Launch Vehicle Flight Trajectory Prediction System (정지궤도 기반 발사체 비행 궤적 추정시스템의 시뮬레이터 개발)

  • Myung, Hwan-Chun
    • Journal of Space Technology and Applications
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    • v.2 no.2
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    • pp.67-80
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    • 2022
  • The missile early-warning satellite systems have been developed and upgraded by some space-developed nations, under the inevitable trend that the space is more strongly considered as another battle field than before. As the key function of such a satellite-based early warning system, the prediction algorithm of the missile flight trajectory is studied in the paper. In particular, the evolution computation, receiving broad attention in the artificial intelligence area, is applied to the proposed prediction method so that the global optimum-like solution is found avoiding disadvantage of the previous non-linear optimization search tools. Moreover, using the prediction simulator of the launch vehicle flight trajectory which is newly developed in C# and Python, the paper verifies the performance and the feature of the proposed algorithm.