• International Journal of Aerospace System Engineering
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• v.10 no.1
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• pp.1-13
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• 2023

The present study was attempted to investigate flow interference effects and the aerodynamic characteristics of the front and rear wings of a joined-wing aircraft by changing the configuration variables. The study was performed using a computational fluid dynamics(CFD) tool to demonstrate forward flight and analyze aerodynamic characteristics. A total of 9 configurations were analyzed with variations on the position, height, dihedral angle, incidence angle, twist angle, sweepback angle, and wing area ratio of the front and rear wings while the fuselage was fixed. The quantities of aerodynamic coefficients were confirmed in accordance with joined-wing configurations. The closer the front and rear wings were located, the greater the flow interference effects tended. Interestingly, the rear wing did not any configuration change, the lift coefficient of the rear wing was decreased when adjusted to increase the incidence angle of the front wing. The phenomenon was appeared due to an effective angle of attack alteration of the rear wing resulting from the flow interference by the front wing configurations.

• Journal of Aerospace System Engineering
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• v.10 no.3
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• pp.39-43
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• 2016

In this paper, a wind-tunnel test is accomplished to investigate the roll characteristics of a variable-span wing flying inside a channel. The factors that affect the roll characteristics of the wing were identified by analyzing the measured data; accordingly, when the wing is flying without both the ground and sidewall effects, the asymmetric wing extension causes the roll moment. Both the ground and the sidewall can increase the roll moment, but when the wing is affected by both the ground and the sidewall, the roll moment does not increase as much as the case where the wing is only affected by the ground. Also, the aerodynamic characteristics of the flying wing inside a channel are the nonlinear function of the wing height and the gap between the wingtip and the sidewall, both of which should be considered in a study of the stability and the flight control of the wing-in-ground effect of the vehicle flying inside a channel.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.5 no.1
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• pp.31-50
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• 1997

A new variable wing that can be swept back and forward synchronously were developed to enhance the aerodynamic and stability characteristics of a high speed airplane. The configuration of the new variable wing changes in such a way that inner part of the wing sweeps forward and outer part of the wing sweeps backward, the shift of aerodynamic center of the wing is small, therfore the static margin that is required for the stability of a airplane is not affected. In this study, various configurations of wing models by combined swept back and forward were designed and a wind tunnel tests were conducted to investigate the aerodynamic characteristics of these variable wings. The experimental results showed that the variable wing by combined swept back and forward has no effect on the pitching moment coefficient affecting on an aircraft stability margin and enhance the aerodynamic characteristics for a given approach angle of attack.

• International Journal of Naval Architecture and Ocean Engineering
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• v.11 no.1
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• pp.225-232
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• 2019

In recent years, nonlinear dynamic models have been developed for flapping-type energy harvesting systems with a rigid wing, but not for those with a flexible wing. Thus, in this study, flexible wing designs of NACA0012 section are proposed and measurements of the forces of rigid cambered wings, which are used to estimate the performance of the designed wings, are conducted. Polar curves from the measured lift and drag coefficients show that JavaFoil estimation is much closer to the measured values than Eppler over the entire given range of angles of attack. As the camber of the rigid cambered wings is increased, both the lift and drag coefficients increase, in turn increasing the resultant forces. Moreover, the maximum resultant forces for all rigid cambered wings are achieved at the same angle of attack as the maximum lift coefficient, meaning that the lift coefficient is dominant in representations of the wing characteristics.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.6 no.1
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• pp.7-20
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• 1998

A reduction of induced drag is an important problem in order to save fuels. In this study, the aerodynamic characteristics of wing tip devices to reduce induced drag, such as end plate, plain ring, helical ring wing tip device, was experimentally investigated in a low speed wind tunnel. The experimental results showed that the wing model with a helical ring wing tip device reduced a induced drag and increased lift-drag ratio.

• Journal of Mechanical Science and Technology
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• v.20 no.7
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• pp.1051-1058
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• 2006

The steady aerodynamic characteristics of a wing flying over a channel are investigated using a boundary-element method. The present method is validated by comparing the computed results with the measured data. Compared with a flat ground surface, the channel fence augmented the lift increase and induced drag reduction. When the fence is lower than the wing height, the gap between the wingtip and the fence does not affect the aerodynamic characteristics of the wing much. When the fence is higher than the wing height, the close gap increased the lift. The induced drag is reduced when the wing is placed near the ground or at the same height as the fence. It is believed that present results can be used in the conceptual design of the high-speed ground transporters flying over the channel.

• International Journal of Aeronautical and Space Sciences
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• v.14 no.2
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• pp.133-139
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• 2013

Morphing aircraft capable of varying their wing form can operate efficiently at various flight conditions. However, radical morphing of the aircraft leads to increased structural complexities, resulting in occurrence of dynamic instabilities such as flutter, which can lead to catastrophic events. Therefore, it is of utmost importance to investigate and understand the changes in flutter characteristics of morphing wings, to ensure uncompromised safety and maximum reliability. In this paper, a study on the flutter characteristics of the folding wing type morphing concept is conducted, to examine the effect of changes in folding angles on the flutter speed and flutter frequency. The subsonic aerodynamic theory Doublet Lattice Method (DLM) and p-k method are used, to perform the flutter analysis in MSC.NASTRAN. The present baseline flutter characteristics correspond well with the results from previous study. Furthermore, enhancement of the flutter characteristics of an aluminum folding wing is proposed, by varying the outboard wing folding angle independently of the inboard wing folding angle. It is clearly found that the flutter characteristics are strongly influenced by changes in the inboard/outboard folding angles, and significant improvement in the flutter characteristics of a folding wing can be achieved, by varying its outboard wing folding angle.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.41 no.1
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• pp.31-39
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• 2013

A Quad Tilt Wing UAV is a new concept hybrid UAV having the advantages of both fixed-wing and rotary-wing aircraft. This paper presents longitudinal flight dynamic characteristics of a Quad Tilt Wing UAV. The designed Quad Tilt Wing UAV is a configuration of a tandem wing type aircraft with an actuating motor and propeller mounted at each wing. Momentum theory is used to calculate the thrust, and nonlinear modeling is performed considering lift and drag generated by slip stream effect of propellers. Also, Force and moment variation at each tilting angle is considered. Static trim on longitudinal axis is analyzed via numerical simulation. Componentwise force contribution was analyzed at each trim mode. Dynamic characteristics were evaluated through eigenvalue analysis for a linear model at each flight mode. It is verified that longitudinal dynamic characteristics are changing from unstable to stable state by continuous transition of dominant poles.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.12
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• pp.1161-1169
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• 2012

A numerical study has been conducted to investigate the aerodynamic characteristics and behavior of a wing-tip vortex around a three-dimensional symmetric wing (NACA0015) in the vicinity of the ground. The aerodynamic characteristics and the wing-tip vortex change as a wing approaches the ground as a result of two different phenomena: the ground effect and the Venturi effect. The ground effect increases lift and decreases drag whereas the Venturi effect generates negative lift and increases drag suddenly. A symmetric airfoil experiences both phenomena with respect to changes in the angle of attack. In the case of a NACA0015 airfoil, the Venturi effect is dominant at small angles of attack but the ground effect is dominant at large angles of attack. Interestingly, both phenomena can be observed at the 4 degree of angle of attack. The vortex core moves inside a wing when the wing experiences the Venturi effect, whereas the vortex core moves outward when the wing experiences the ground effect.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.19 no.1
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• pp.1-6
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• 2011

The free-wing tilt-body aircraft is researched in the flight performance characteristics such as short take-off and landing capability, and reduced sensitivity to gust and center of gravity (CG) change. Due to the main wing separating from the fuselage, the high tiltable empennage, and the stub-wing strongly influencing from the propeller wake, the resulting vehicle aerodynamics and flight dynamics are quite different from those of a conventional fixed-wing aircraft. Using the governing flight dynamics model was studied previously, all of speed and body tilt angle is simulated to determine the flight envelope by a non-linear 3-DOF flight simulation analysis. Though flight performance and trimmability are studied, the flight model of free-wing tilt-body aircraft is to reduce the hidden risk and to achieve the successful flight test. It is analyzed the flight characteristics that distinguishes free-wing tilt-body aircraft from the conventional aircraft.