• Title/Summary/Keyword: 리드래그

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Aerodynamic Analysis of a Rectangular Wing in Flapping with Lead-Lag Motion using Unsteady VLM (직사각형 평판날개의 리드래그 운동이 조합된 날개짓에 대한 비정상 VLM 공력 해석)

  • Kim, Woo-Jin;Kim, Hark-Bong
    • Journal of the Korean Society for Aviation and Aeronautics
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    • v.14 no.2
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    • pp.39-44
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    • 2006
  • The unsteady vortex lattice method is used to model lead-lag in flapping motions of a rectangular flat plate wing. The results for plunging and pitching motions were compared with the limited experimental results available and other numerical methods. They show that the method is capable of simulating many of the features of complex flapping flight. The lift, thrust and propulsive efficiency of a rectangular flat plate wing have been calculated for various lead-lag motion and reduced frequency with an amplitude of flapping angle(20o). To describe a motion profile of wing tip such as elliptic, line and circle, the phase difference of flapping and lead-lag motion was changed. And the effects of the motion profile on the aerodynamic characteristics of the flapping wing are discussed by examination of their trends.

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An Experimental Study of Aeroelastic Stability of Hingeless Hub System with Metal and Composite Hub Flexure (금속재와 복합재 허브 Flexure를 갖는 무힌지 허브시스템의 공력탄성학적 안정성에 관한 실험적 연구)

  • Song, Keun-Woong;Kim, Joune-Ho;Kim, Deog-Kwan;Rhee, Wook
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.33 no.2
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    • pp.98-105
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    • 2005
  • This paper presents the result of the aeroelastic stability test of the small-scaled hingeless hub system with composite paddle blades in hover and forward flight conditions. Excitation tests of hingeless hub system installed in GSRTS(General Small-scale Rotor Test System) at KARI(Korea Aerospace Research Institute) were carried out to get lead-lag damping ratio of blades with flexures as hub flexure. MBA(Moving Block Analysis) technique was used for the estimation of lead-lag damping ratio. First, blades with metal flexures, then with composite flexures of the same dynamic properties of rotor system as metal one were tested. Tests were done on the ground and in the wind tunnel according to the test conditions of hover and forward flight, respectively. Composite flexures were found to have better damping characteristics over metal ones in the non-rotating vibration test, and it was confirmed that the use of composite flexures would give observable improvement in aeroelastic stability compared to metal ones in all test conditions.

패들형 블레이드를 장착한 힌지없는 로터 시스템의 회전시험

  • Song, Keun-Woong;Kim, Joune-Ho;Kim, Deog-Kwan
    • Aerospace Engineering and Technology
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    • v.3 no.2
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    • pp.217-228
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    • 2004
  • This paper presents the rotating test techniques and the results of the roating test of the small-scaled hingeless rotor system with composite paddle blades in hover and forward flight conditions. The small-scaled rotor system was designed using froude-scaled properties of full scale rotor system. Metal flexures and composite flexures were made as hub flexures by the same dynamic properties of rotor system. The rotating tests of hingeless rotor system installed in GSRTS at KARI were carried out to get lead-lag damping ratios and aerodynamic loads of the hingeless rotor system. MBA(Moving Block Analysis) technique was used for the estimation of lead-lag damping ratio. 6-components balance was installed between hub and main shaft and straingauges on blades were instrumented for the measurements of aerodynamic loads of rotor system. Tests were performed on the ground and in the wind tunnel according to the test conditions of hover and forward flight, respectively.

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The Accommodative Lag and Refractive Error in Early Adults (초년 성인의 굴절이상과 조절래그 분포의 연관성)

  • Baarg, Saang-Bai;Jeong, Youn Hong
    • Journal of Korean Ophthalmic Optics Society
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    • v.17 no.1
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    • pp.59-65
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    • 2012
  • Purpose: The purpose of this study was to determine the distribution and correlation of accommodative lag with refractive error. Method: We had tested the clinical refraction and the accommodative lag in clinically normal 49 young adults (total 98 eyes) aged 18 to 25 years without abnormal binocular function. Monocular and binocular accommodative lag were tested with 0.50 D cross-cylinder lens and near vision test chart which had cross-hairs after full correction of LogMAR visual acuity over 0.05. Results: There was no statistical differences in monocular accommodative lag between right ($0.64{\pm}0.64$ D) and left eye ($0.63{\pm}0.64$)(p=0.858). The accommodative lag of male was higher than female and the range of the value was broader than female in binocular accommodative lag (p=0.015). The wider the inter-pupillary distance was, the higher the accommodative lag was (p=0.003). However, there were no differences with age (p=0.800) and dominant eye (p=0.402). The ranges of accommodative lag of low, middle, and high myopia were 0.75 ~ -0.25 D, 1.25 ~ -0.50 D, and 1.50 ~ -0.75 D, respectively, and the regression was 'y = -0.03953x+0.09205'. Conclusions: These data suggest that clinically normal young adults with high amounts of refractive error have more variable accommodative lag and increased spherical equivalent refraction.

Improvement and Operation of a Helicopter Tail-Fan Performance Test System (헬리콥터 테일팬 시험장치 개조 및 운용)

  • Lee, Je-Dong;Song, Keun-Woong;Kang, Hee-Jung;Sim, Jung-Wook;Kim, Seung-Bum
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2005.11b
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    • pp.41-44
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    • 2005
  • This paper described improvement and operation of a 'Tail-Fan' anti-torque performance test system KARI (Korea Aerospace Research Institute) developed a 'Tail-Fan' anti-torque system of a helicopter and a performance test-rig to test the performance of the Tail-Fan. The test-rig was improved for full rotating test in 4300rpm(100%). Machinery and hydraulic parts ware changed to reduce vibration and to increase safety. To find the operation rotating speed for the performance test, vibration test were carried out rising accelerometers on tail gear box. The performance test conditions of the Tail-Fan to avoid a resonance were found from vibration test results. The Tail-Fan operation tests were performed safely frier to carry out performance test.

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The Operation and Vibration Characteristics of Tail-Fan Performance Test System (테일팬 성능시험장치의 운용과 진동특성)

  • Song, Ken-Woong;Kim, Jun-Ho;Kang, Hee-Jung;Rhee, Wook;Sim, Jung-Wook
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2004.11a
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    • pp.508-512
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    • 2004
  • This paper described operation and vibration characteristics of 'Tail-Fan' performance test system. KARI(Korea Aerospace Research Institute) developed 'Tail-Fan' system as a kind of helicopter anti-torque system(ATS) and designed ATS performance test-rig for Tail-Fan system performance test. Test-rig consists of driving parts, supporting parts and rotating parts. For Tail-Fan system performance tests, firstly, test-rig operation tests were carried out for verification of design specifications. Secondly, natural frequencies of fan blade and test-rig were measured respectively. Lastly, to find the operation rotating speed for performance tests, vibration tests using accelerometers on tail gear box(TGB) were carried out. Through the fanplot and vibration test results, Tail-Fan performance test conditions to avoid a resonance were found and performance tests were well done safely.

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A Validation Study on Structural Load Analyses of TiltRotors in Wind Tunnel (풍동 시험용 틸트로터의 구조 하중 해석의 검증 연구)

  • Ui-Jin Hwang;Jae-Sang Park;Myeong-Kyu Lee
    • Journal of Aerospace System Engineering
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    • v.17 no.2
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    • pp.45-55
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    • 2023
  • This study conducted aeromechanics modeling and structural load analyses of Tilt Rotor Aeroacoustic Model (TRAM), a 25% scaled V-22 tiltrotor model used in wind tunnel tests. A rotorcraft comprehensive analysis code, CAMRAD II, was used. Analysis results of this study in low-speed forward flights were compared with DNW test and previous analysis results. Blade flap bending moments were in good agreement with measured data. Mean values and oscillatory loads for lead-lag bending and torsion moments were slightly different from measured data. However, when mean values were removed, results of structural loads for one rotor revolution were moderately compared with wind tunnel tests and previous analyses. Total forces and half peak-to-peak forces of the pitch link reasonably well matched with previous analysis results and measured data. Finally, harmonic magnitudes of blade structural loads were investigated.

Papers : Implicit Formulation of Rotor Aeromechanic Equations for Helicopter Flight Simulation (논문 : 헬리콥터 비행 시뮬레이션을 위한 로터운동방정식 유도)

  • Kim, Chang-Ju
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.30 no.3
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    • pp.8-16
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    • 2002
  • The implicit formulation of rotor dynamics for helicopter flight simulation has been derived and and presented. The generalized vector kinematics regarding the relative motion between coordinates were expressed as a unified matrix operation and applied to get the inertial velocities and accelerations at arbitaty rotor blade span position. Based on these results the rotor aeromechanic equations for flapping dynamics, lead-lag dynamics and torque dynamics were formulated as an implicit form. Spatial integration methods of rotor dynamic equations along blade span and the expanded applicability of the present implicit formulations for arbitrary hings geometry and hinge sequences have been investigated. Time integration methods for present DAE(Differential Algebraic Equation) to calculate dynamic response calculation are recommenaded as future works.