• Title/Summary/Keyword: Flapping motion

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Visualization Study of Dragonfly Type Wing : Reduced Frequency (잠자리 유형 날개의 가시화 연구 : 무차원 진동수)

  • Kim Song Hak;Chang Jo Won
    • 한국가시화정보학회:학술대회논문집
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    • 2004.11a
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    • pp.14-17
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    • 2004
  • A purpose of this visual experiment is to investigate the effect of reduced frequency qualitatively by examining wake pattern change for insect flying motion. Insect is composed of two pair wing with forewing and hindwing, flying motion of insect is performed pitching and plunging so it makes a separation over the wings. The separation affects at the wake pattern and changed wake pattern has an influence on lift, drag and propulsion. This experiment is conducted by using a smoke wire technique and a camera is fixed at hindwing to take a photograph of wake. An electronic device is mounted below test section to find exact the mean positional angle of wing. The reduced frequency in experiment is 0.15, 0.3 and 0.45. We obtained the result which that reduced frequency is closely related to wake pattern that determines flight efficiency.

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Unsteady Lift Measurements of the Dragonfly-type Wing (잠자리 유형 날개의 비정상 양력 측정)

  • Kim, Song-Hak;Jang, Jo-Won
    • Journal of the Korean Society for Aviation and Aeronautics
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    • v.14 no.2
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    • pp.1-8
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    • 2006
  • Unsteady lift measurements were carried out in order to investigate the effects of phase difference and reduced frequency of a dragonfly-type model with two pairs of wing. A load-cell was employed to measure the lift generated by a plunging motion of the dragonfly-type model with the incidence angles of 0$^{circ}$. Experimental conditions are as follows: phase differences between fore- and hind-wings are 0$^{circ}$, 90$^{circ}$, 180$^{circ}$, and 270$^{circ}$, and reduced frequencies are 0.075, 0.15 and 0.225, respectively. The freestream velocity was 143 m/sec and corresponding chord Reynolds number was $3.4{\times}10^3$. The variation of phase-averaged lift coefficients during one cycle of the wing motion is presented. Results show that the total value of the positive lift coefficient during one cycle of the wing motion is the largest at the phase difference of 90$^{circ}$, and that the maximum lift coefficient and lift coefficient per unit of time increases with reduced frequency.

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The Aerodynamic Characteristics by the Insect Wing Tip Trajectory in Hovering Flight (정지 비행에서의 곤충 날개 궤적에 따른 공기역학적 특성)

  • Cho, Hun-Kee;Joo, Won-Gu
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.33 no.7
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    • pp.506-511
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    • 2009
  • Insect flight is adapted to cope with each circumstance by controlling a variety of the parameters of wing motion in nature. Many researchers have struggled to solve the fundamental concept of insect flight, but it has not been solved yet clearly. In this study, to find the most effective flapping wing dynamics, we conducted to analyze CFD data on fixing some of the optimal parameters of wing motion such as stoke amplitude, flip duration and wing rotation type and then controlled the deviation angle by fabricating wing tip motion. Although all patterns have the similar value of lift coefficient and drag coefficient, pattern A(pear-shape type) indicates the highest lift coefficient and pattern H(pear-shape type) has the lowest lift coefficient among four wing tip motions and three deviation angles. This result suggest that the lift and drag coefficient depends on the angle of attack and the deviation angle combined, and it could be explained by delayed stall and wake capture effect.

Study on 4-degree-of-freedom Mathematical Model for Simulation of Wind Turbine System at Initial Design Stage (풍력발전기 초기단계 모사실험을 위한 4자유도 수학적 모형에 대한 연구)

  • Shin, Yun-Ho;Moon, Seok-Jun;Chung, Tae-Young
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.23 no.8
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    • pp.681-689
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    • 2013
  • The commercial tools to simulate the non-linear dynamic characteristics of wind turbine system are various but, the tool take much time to simulate the control algorithm and require many input variables. In this paper, the procedures to derive the simplified 4-degree-of-freedom mathematical model of a 2-MW wind turbine which could be used at the initial design stage of the controller are proposed based on RISO's suggested method. In this model, the 1st tower fore-after bending motion and 1st blade flapping motion are also considered in addition to the rotor-generator rotation motion in the 2-DOF model. The effectiveness of the 4-DOF model is examined comparing with the 2-DOF model and verification of the simplified model is accomplished through modal analysis for whole wind turbine system.

The Performance Estimation of Rotor in Wind Fence by Rotor Analysis Solver based on Actuator Disk Model (Actuator Disk Model 기반의 로터 해석자를 사용한 방풍 구조물 내부의 로터 성능 예측)

  • Kim, Taewoo;Oh, Sejong;Kang, Hee Jung;Yee, Kwanjung
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.41 no.6
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    • pp.429-439
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    • 2013
  • The purpose of current study is to develop the rotor analysis solver and perform a rotor aerodynamic analysis in the wind fence. To this end, the rotor analysis solver based on actuator disk model was employed. To consider the asymmetric effect of the rotor in the wind fence, the flapping motion analysis was conducted with blade element theory for the effective angle of attack calculation. The validation cases which are the rotor with wall and ground were accomplished by developed solver. The decrease of rotor performance by wind fence was confirmed. The wind fence configuration was suggested which guarantees more than 95% rotor performance compared with the no fence case.

Prediction for Rotor Aerodynamics of Quadcopter Type Unmanned Aerial Vehicle Considering Gust and Flight Conditions (비행 조건의 영향을 고려한 쿼드콥터형 무인비행체의 로터 공력 특성 예측)

  • Park, SunHoo;Eun, WonJong;Shin, SangJoon
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.46 no.10
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    • pp.833-844
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    • 2018
  • This paper aims to predict the aerodynamic characteristics of individual rotor for the gust and flight conditions. Transformation procedure into the wind frame is conducted to analyze the gust. Hover, forward, and climb flight conditions of an individual rotor are analyzed using the blade element momentum theory (BEMT) considering the rigid blade flapping motion. XFOIL is used to derive aerodynamic results. Validation for hover, forward flight, and climb conditions are conducted using the present BEMT. In addition, a static experimental environment is constructed. The experimental results and the present BEMT are compared and verified.

Study on the Thrust Generation of a Flat Plate in Heave Oscillation Using a Lattice-Boltzmann Method (격자볼츠만 법을 사용한 히브진동 운동하는 평판에서의 추력발생 연구)

  • An, Sang-Joon;Kim, Yong-Dae;Maeng, Joo-Sung;Lee, Jong-Shin;Han, Cheol-Heui
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.35 no.5
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    • pp.397-403
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    • 2007
  • Insect and birds in nature flap their wings to generate fluid dynamic forces that are required for locomotion. To develop a feasible flapping MAV, it is of crucially important to study the fundamental relations between flapping motion and thrust generation. In this paper, the onset conditions of the thrust generation of a heaving flat plate is investigated using a Lattice-Boltzmann method. For a fixed heaving amplitude of h/C=0.5, the effect of reduced frequency on the thrust generation is investigated. For several values of heaving amplitude(h/C=0.25, 0.325, 0.50), the effect of reduced frequency on the thrust generation is also investigated. It can be said that Strouhal number is more important rather than reduced frequency in case of thrust generation. It is found that the critical Strouhal number over which the flat plate starts to produce thrust is around 0.1. Thrust is an exponential function of the Strouhal number.

Experimental and Computational Investigation of Aerodynamic Characteristics of Hovering Coleoptera

  • Saputra, Saputra;Byun, Do-Young;Yoo, Yong-Hoon;Park, Hoon-Choel;Byun, Yong-Hwan
    • Proceedings of the KSME Conference
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    • 2007.05a
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    • pp.384-388
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    • 2007
  • Aerodynamic characteristics of Coleoptera species of Epilachna quadricollis and Allomyrina dichotoma are experimentally and numerically investigated. Using digital high speed camera and smoke wire technique, we visualized the continuous wing kinematics and the flight motion of free-flying coleoptera. The experimental visualization shows that the elytra flapped concurrently with the main wing both in the downstroke and upstroke motions. The wing motion of Epilachna quadricollis was captured and analyzed frame by frame to identify the kinematics of the wings and to implement it in the movement of a model wing (thin plate) in the simulation. The two-dimensional simulation of Epilachna quadricollis hovering flight was performed by assuming the wing cross section shape as a thin plate, even though most of insect's wings are made of curved corrugated membrane. The effect of Reynolds number are investigated by the simulation. Meanwhile, in order to investigate the role and effect of elytra, the flow visualization of Allomyrina dichotoma was carried on using smoke wire visualization technique. Here, we confirmed that the vortex generated by elytra due to its movement is strongly influence the vortex dynamic generated by hind wings.

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Aeroelastic Response of an Airfoil-Flap System Exposed to Time-Dependent Disturbances

  • Shim, Jae-Hong;Sungsoo Na;Chung, Chan-Hun
    • Journal of Mechanical Science and Technology
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    • v.18 no.4
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    • pp.560-572
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    • 2004
  • Aeroelastic response and control of airfoil-flap system exposed to sonic-boom, blast and gust loads in an incompressible subsonic flowfield are addressed. Analytical analysis and pertinent numerical simulations of the aeroelastic response of 3-DOF airfoil featuring plunging-pitching-flapping coupled motion subjected to gust and explosive pressures in terms of important characteristic parameters specifying configuration envelope are presented. The comparisons of uncontrolled aeroelastic response with controlled one of the wing obtained by feedback control methodology are supplied, which is implemented through the flap torque to suppress the flutter instability and enhance the subcritical aeroelastic response to time-dependent excitations.

SIMULATION OF ENERGY HARVESTING EEL BY THE IMMERSED BOUNDARY METHOD

  • Jung, Ki-Sung;Huang, Wei-Xi;Sung, Hyung-Jin
    • 한국전산유체공학회:학술대회논문집
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    • 2008.03a
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    • pp.197-203
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    • 2008
  • In the present study, we carry out numerical simulations of energy harvesting eel by using the immersed boundary method. Eel is modeled by a flexible filament and is placed behind a circular cylinder. We perform systematic simulations in order to explore the effects of Reynolds number. The instantaneous eel motion is analyzed under different conditions and surrounding vortical structures are identified. The flapping frequency of eel has been compared with that in case of plate alone as well as filament alone. As increasing Reynolds number, we can see that the flexible filament flaps passively by obtaining the Strouhal number of cylinder alone and filament with cylinder.

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