• Proceeding of EDISON Challenge
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• 2016.11a
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• pp.58-62
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• 2016

본 연구에서는 지면효과의 영향을 비행체의 형상에 따라 비교하기 위해 에어포일, 플랩을 장착한 에어포일 그리고 플라잉디스크를 EDISON_CFD를 통해 해석하고자 한다. 받음각 $0^{\circ}$, $5^{\circ}$, $10^{\circ}$에 대하여 마하수 0.18, 단위 길이 당 레이놀즈수 $3.78{\times}10^{-5}/m$의 유동조건에서 2차원 범용 소프트웨어인 KFLOW_EDISION_13의 S-A Turbulent Model을 이용하여 지면과의 높이를 형상 코드길이를 기준으로 0.25c, 0.5c, 1c, 3c로 변경하면서 해석을 수행하였다. 그 결과 세 형상 모두 일반적인 지면효과인 지면과 가까울수록 양력계수는 증가, 항력계수는 감소하여 양항비가 증가하는 경향을 보여주었다. 하지만 일부 예외적인 부분을 확인하여 분석을 실시하였다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.50 no.10
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• pp.677-690
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• 2022

By using an actuator disk method based flow solver, aerodynamic analysis is carried out for a dual ducted fan aircraft, which is one of the VTOL compound aircrafts, and its associated ground effect is analyzed. The characteristics and accuracy of the solver for ground effect analysis is evaluated through a comparison with the results obtained from the sliding mesh technique. The aerodynamic performance and flow field characteristics with respect to the distance from the ground are analyzed. As the ground distance decreases, the fan thrust increases, but the deterioration of total normal force and hovering flight efficiency is identified owing to the decrease in the vertical force of the duct, fuselage, and wing. By examining the flow field in the bottom of the fuselage, the ground vortices and fountain flow generated by the interaction of the fan wake and ground are identified, and their influence on the aerodynamic performance is analyzed. The strength and characteristics of outwash with respect to the ground distance and azimuth direction are analyzed through comparison/examination of velocity profile. Influence of the ground effect with respect to collective pitch angle is also identified.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.35 no.5
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• pp.369-374
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• 2007

Unsteady aerodynamic characteristics of the wing with flaperon flying over nonplanar ground surface are investigated using a boundary-element method. The time-stepping method is used to simulate the wake shape according to the motion of the wing and flaperon over the surface or in the channel. The aerodynamic coefficient according to the periodic motion of the flaperon is shown as the shape of loop. The rolling moment coefficient of the wing flying in the channel is same as that of the wing flying over the ground surface. The variation range of pitching moment is wider when the wing flies in the channel than over the ground surface. The present method can provide various aerodynamic derivatives to secure the stability of superhigh speed vehicle flying over nonplanar ground surface using the present method.

• Proceedings of the KSME Conference
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• 2005.11a
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• pp.43.2-43.2
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• 2005

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.50 no.9
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• pp.599-608
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• 2022

Urban air mobility (UAM) equipped with rotor system is subject to ground effect at vertiport during takeoff and landing. The aerodynamic performance of the aircraft in ground effect should be analyzed for the safe operation. In this study, The ground effects on the aerodynamic performance and wake structure of the quadcopter electric vertical takeoff and landing (eVTOL) configuration equipped with coaxial counter-rotating propellers were investigated by using the lattice Boltzmann method (LBM). The influence of the ground effect was observed differently in the upper and lower propellers of the coaxial counter-rotating propeller system. There was no significant change in the aerodynamic performance of the upper propeller even if the propeller height above the ground was changed, whereas the averaged thrust and torque of the lower propeller increased significantly as propeller height decreased. In addition, the amplitude of the thrust fluctuation tended to increase as the propeller height decreased. The propeller wake was not sufficiently propagated downstream and was diffused along the ground due to the outwash flow developed by the ground effect. The impingement of the rotor wakes on the ground and a fountain vortex structure were observed.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.35 no.6
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• pp.483-488
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• 2007

The aerodynamic characteristics of FAST(Future Air Speed Transit) combined the body with tandem wing flying over nonplanar ground surface are investigated by using a boundary element method. To validate the present method, results of the present analysis are compared with the experiment and other numerical results. The arrangement of the tandem wing is determined to secure sufficient aero-levitation force and the stability through the analysis of the aerodynamic characteristics of the FAST. The FAST has the maximum lift characteristics when the tandem wing with lower endplate is located at the front side and the rear side of the body. The stability of the FAST can be secured by using the flaperon of the tandem wing.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.34 no.7
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• pp.12-17
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• 2006

Longitudinal static stability and steady aerodynamic characteristics of wings flying over nonplanar ground surfaces (rail and channel) are investigated using the boundary-element method. For a channel with it's fence higher than the wing height, the lift and the nose-down pitching moment increase as the gap between the wingtip and the fence decreases. For a rail with it's width wider than the wing span, the lift and the nose-down pitching moment increase as the rail height decreases. Longitudinal static stability of a single wing flying over nonplanar surfaces is worse than the case of the flat ground. In case of tandem wings, longitudinal static stability of the wings flying over the channel is better than the case of the flat ground. It is believed that the present results can be applied to the conceptual design of high-speed ground transporters.

• Journal of Aerospace System Engineering
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• v.17 no.2
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• pp.26-37
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• 2023

Urban air mobility (UAM) is being developed as part of the next-generation aircraft, which could be a viable solution to entrenched problems of urban traffic congestion and environmental pollution. A new airport platform called vertiport as a space where UAM can take off and land vertically is also being introduced. Noise regulations for UAM will be strict due to its operation in a highly populated urban area. Ground effects caused by vertiport can directly affect aerodynamic forces and noise characteristics of UAM. In this study, ground effects of vertiport on aerodynamic loads, vorticity field, and far-field noise were analyzed using Lattice-Boltzmann Method (LBM) simulation and Ffowcs Williams and Hawkings (FW-H) acoustic analogy with a permeable surface method.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.35 no.2
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• pp.149-156
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• 2007

The present study provides structural design and analysis of main wing and horizontal tail of a small scale WIG(Wing in Ground Effect) vehicle which has been developed as a part of the high speed maritime transportation system for the future of Korea. Weight saving as well as structural stability could be achieved by skin-spar with foam sandwich design and with wide application of carbon/epoxy composite material. A commercial FEM code, NASTRAN, was utilized to confirm the structural safety and stability through sequential design modifications to meet the final design goal. In addition, each wing and the fuselage were fastened together by eight insert bolts with high strength to accomodate easy assembling and disassembling as well as to guarantee a service life longer than 20 years.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.8
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• pp.971-976
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• 2011

This paper presents the design concepts of a protector for a launch-reconnaissance robot that is to be deployed for data-collection in hazardous regions. The protector protects the reconnaissance robot inside from shock induced during the process of launch, flight, and landing. Since the outer shells of the protector are automatically opened wide by the unlocking mechanism during the landing stage, the reconnaissance robot can easily exit the protector and move around to carry out its mission. We carefully simulated a finite-element model of the protector with the robot and compared the results with the actual dynamic behavior of the system. Shock- response tests using a droptable showed that the proposed protector filled with silicon material successfully attenuated external shock.