• Title, Summary, Keyword: aerodynamic stability

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Wind Tunnel Test of an Unmanned Aerial Vehicle (UAV)

  • Chung, Jin-Deog;Lee, Jang-Yeon;Sung, Bong-Zoo;Koo, Sa-Mok
    • Journal of Mechanical Science and Technology
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    • v.17 no.5
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    • pp.776-783
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    • 2003
  • A low speed wind tunnel test was conducted for full-scale model of an unmanned aerial vehicle (UAV) in Korea Aerospace Research Institute (KARI) Low Speed Wind Tunnel(LSWT). The purpose of the presented paper is to illustrate the general aerodynamic and performance characteristics of the UAV that was designed and fabricated in KARI. Since the testing conditions were represented minor portions of the load-range of the external balance system, the repeatability tests were performed at various model configurations to confirm the reliability of measurements. Variations of drag-polar by adding model components such as tails, landing gear and test boom are shown, and longitudinal and lateral aerodynamic characteristics after changing control surfaces such as aileron, flap, elevator and rudder are also presented. To explore aerodynamic characteristics of an UAV with model components build-up and control surface deflections, lift curve slope, pitching moment variation with lift coefficients and drag-polar are examined. The discussed results might be useful to understand the general aerodynamic characteristics and drag pattern for the given UAV configuration.

Autopilot Design for Agile Missile with Aerodynamic Fin and Side Thruster

  • Choi, Yong-Seok;Lee, Ho-Chul;Choi, Jae-Weon
    • 제어로봇시스템학회:학술대회논문집
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    • pp.508-513
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    • 2003
  • This paper is concerned with a mixed control with aerodynamic fin and side thrusters applied to an agile missile using two-time scale dynamic inversion and linear time-varying control technique. The nonlinear dynamic inversion method with the weighting function allocates the desired control inputs (aerodynamic fin and side thrusters) to track a reference trajectory, and the time-varying control technique guarantees the robustness for the uncertainties. Closed-loop stability is achieved by the assignment of the extended-mean of these linear time-varying eigenvalues to the left half complex plane. The proposed schemes are validated by nonlinear simulations.

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Design of controllers for Angle control of Aerodynamic Plant using SEVA (SEVA를 이용한 Aerodynamic Plant의 각도 제어를 위한 제어기의 설계)

  • 나승유;배희종;기효종
    • 제어로봇시스템학회:학술대회논문집
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    • pp.49-49
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    • 2000
  • Sensors are used to measure the states in need for control in a closed-loop system. Accuracy, reliability, stability of sensors are closely related to the controller performance. In case of sensor faults, they are detected by examining the sensor output values and the major values of the system. And then the types of the faults are recognized by the analysis of symptoms of faults. In this paper, a self-validating sensor is applied to the control of an aerodynamic plant system with the sensor fault problems in the potentiometer module for exact positioning to show the applicability. We propose a digital controller can provide a satisfactory loop performance even when the sensor faults occur.

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Aerodynamic and Structural Design on Small Wind Turbine Blade Using High Performance Configuration and E-Glass/Epoxy-Urethane Foam Sandwich Composite Structure

  • Kong, Changduk;Bang, Johyuk
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • pp.401-407
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    • 2004
  • This study proposes a interim development result for the l-㎾ class small wind turbine system, which is applicable to relatively low wind speed regions like Korea and has the variable pitch control mechanism. In the aerodynamic design of the wind turbine blade, parametric studies were carried out to determine an optimum aerodynamic configuration which is not only more efficient at low wind speed but whose diameter is not much larger than similar class other blades. A light composite structure, which can endure effectively various loads, was newly designed. In order to evaluate the structural design of the composite blade, the structural analysis was performed by the finite element method. Moreover both structural safety and stability were verified through the full-scale structural test.

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Whirl Flutter Analysis of a 2-DOF Rotor-Nacelle System Using Quasisteady Aerodynamic Theory (준정상 공력이론을 이용한 2자유도계 로터-낫셀 시스템의 훨플러터 해석)

  • Kim, Dong-Hyun;Yang, Yong-Joon
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.15 no.7
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    • pp.843-850
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    • 2005
  • In this study, simplified whirl flutter analyses using quasisteady aerodynamic theory have been Performed for a 2-DOF tiIt-rotor system with both pitch and Yaw motions of a rotor-nacelle. The present dynamic system consists of the rotor (propeller) , forming the gyroscopic and aerodynamic element, supported horizontally by a pylon that is pivoted at some wing attachment point. Several design parameters for rotor-nacelle system are considered to practically investigate the effects of whirl flutter stability.

Whirl Flutter Analysis of a 2-DOF Rotor-Nacelle System Using Quasisteady Aerodynamic Theory (준정상 공력이론을 이용한 2자유도계 로터-낫셀 시스템의 훨플러터 해석)

  • Yang, Yong-Joon;Kim, Dong-Hyun;Jung, Se-Un;Kim, Hyun-Jung;Alexander, Boby
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.301-307
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    • 2005
  • In this study, simplified whirl flutter analyses using quasisteady aerodynamic theory have been performed for a 2-DOF tilt-rotor system with both pitch and yaw motions of a rotor-nacelle. The present dynamic system consists of the rotor (propeller), forming the gyroscopic and aerodynamic element, supported horizontally by a pylon that is pivoted at some wing attachment point. Several design parameters (or rotor-nacelle system are considered and the effect of whirl flutter stability are also investigated for various design parameters.

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Prediction of Aerodynamic Coefficients of Bridges Using Computational Fluid Dynamics (전산유체역학 해석에 의한 교량 단면의 공력 특성값 추정)

  • Hong, Young-Kil
    • Journal of the Korean Society of Safety
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    • v.28 no.1
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    • pp.57-62
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    • 2013
  • Aerodynamic characteristics of cross section shape is an important parameter for the wind response and structural stability of long span bridges. Numerical simulation methods have been introduced to estimate the aerodynamic characteristics for more detailed flow analysis and cost saving in place of existing wind tunnel experiment. In this study, the computational fluid dynamics(CFD) simulation and large eddy simulation( LES) technique were used to estimate lift, drag and moment coefficients of four cross sections. The Strouhal numbers were also determined by the fast Fourier transform of time series of the lift coefficient. The values from simulations and references were in a good agreement with average difference of 16.7% in coefficients and 8.5% in the Strouhal numbers. The success of the simulations is expected to attribute to the practical use of numerical estimation in construction engineering and wind load analysis.

Numerical calculations of aerodynamic performance for ATM train at crosswind conditions

  • Rezvani, Mohammad Ali;Mohebbi, Masoud
    • Wind and Structures
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    • v.18 no.5
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    • pp.529-548
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    • 2014
  • This article presents the unsteady aerodynamic performance of crosswind stability obtained numerically for the ATM train. Results of numerical investigations of airflow past a train under different yawing conditions are summarized. Variations of occurrence flow angle from parallel to normal with respect to the direction of forward train motion resulted in the development of different flow patterns. The numerical simulation addresses the ability to resolve the flow field around the train subjected to relatively large yaw angles with three-dimensional Reynolds-averaged Navier-Stokes equations (RANS). ${\kappa}-{\varepsilon}$ turbulence model solved on a multi-block structured grid using a finite volume method. The massively separated flow for the higher yaw angles on the leeward side of the train justifies the use of RANS, where the results show good agreement with verification results. A method of solution is presented that can predict all aerodynamic coefficients and the wind characteristic curve at variety of angles at different speed.

Galloping analysis of roof structures

  • Zhang, Xiangting;Zhang, Ray Ruichong
    • Wind and Structures
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    • v.6 no.2
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    • pp.141-150
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    • 2003
  • This paper presents galloping analysis of multiple-degree-of-freedom (MDOF) structural roofs with multiple orientations. Instead of using drag and lift coefficients and/or their combined coefficient in traditional galloping analysis for slender structures, this study uses wind pressure coefficients for wind force representation on each and every different orientation roof, facilitating the galloping analysis of multiple-orientation roof structures. In the study, influences of nonlinear aerodynamic forces are considered. An energy-based equivalent technique, together with the modal analysis, is used to solve the nonlinear MDOF vibration equations. The critical wind speed for galloping of roof structures is derived, which is then applied to galloping analysis of roofs of a stadium and a high-rise building in China. With the aid of various experimental results obtained in pertinent research, this study also shows that consideration of nonlinear aerodynamic forces in galloping analysis generally increases the critical wind speed, thus enhancing aerodynamic stability of structures.

Quasi Steady Stall Modelling of Aircraft Using Least-Square Method

  • Verma, Hari Om;Peyada, N.K.
    • International Journal of Aerospace System Engineering
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    • v.7 no.1
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    • pp.21-27
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    • 2020
  • Quasi steady stall is a phenomenon to characterize the aerodynamic behavior of aircraft at high angle of attack region. Generally, it is exercised from a steady state level flight to stall and its recovery to the initial flight in a calm weather. For a theoretical study, such maneuver is demonstrated in the form of aerodynamic model which consists of aircraft's stability and control derivatives. The current research paper is focused on the appropriate selection of aerodynamic model for the maneuver and estimation of the unknown model coefficients using least-square method. The statistical accuracy of the estimated parameters is presented in terms of standard deviations. Finally, the validation has been presented by comparing the measured data to the simulated data from different models.