• Proceedings of the Korean Information Science Society Conference
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• 2004.04a
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• pp.907-909
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• 2004

에어포일(airfoil)이 공기속을 지날 때 양력이 발생한다. 공간상을 비행하는 물체에는 중력, 추력, 양력, 항력의 네 가지 힘이 작용한다. 본 논문에서는 항공역학의 연구결과를 바탕으로 차이니즈탑이란 물체가 회전하면서 수직상승과 호버링 그리고 하강하는 동안의 운동형태를 사실적이면서도 실시간으로 구현한다. 그 결과는 게임이나 비행 시뮬레이션에 응용할 수 있다.

• Journal of the Korean Society of Visualization
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• v.3 no.2
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• pp.63-70
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• 2005

Birds and insects flap their wings to fly in the air and they can change their wing motions to do steering and maneuvering. Therefore, we created various wing motions with the parameters which affected flapping motion and evaluated the aerodynamic characteristics about those cases in this study. As the wing rotational velocity was fast and the rotational timing was advanced, the measured aerodynamic forces showed drastic increase near the end of stroke. The mean lift coefficient was increased until angle of attack of $50^{\circ}$ and showed the maximum value of 1.0. The maximum mean lift to drag ratio took place at angle of attack of $20^{\circ}$. Flow fields were also visualized around the wing using particle image velocimetry (PIV). From the flow visualization, leading-edge vortex was not shed at mid-stroke until angle of attack of $50^{\circ}$. But it was begun to shed at angle of attack of $60^{\circ}$.

• Journal of the Society of Naval Architects of Korea
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• v.29 no.4
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• pp.104-113
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• 1992

The hydrodynamic problem is treated here when a pressurized bag is submerged partially into water and the end points of it oscillate. SES(Surface Effect Ship)has a bag filled with pressurized air at the stern in order to prevent the air leakage, and the pitch motion of SES is largely affected by the hydrodynamic force of the bag. The shape of a bag can be determined with the pressure difference between inside and outside. Once the hydrodynamic pressure is given, the shape of a bag can be obtained, however in order to calculate the hydrodynamic pressure we should know the shape change of the bag, and vice versa. Therefore the type of boundary condition on the surface of a bag is a moving boundary like a free surface boundary. In this paper, the formulation of this problem was done and linearized. The calculation scheme for the radiation problem of an oscillating bag is shown in comparison with the case that the bag is treated as rigid body. The hydrodynamic forces are calculated for various values of the pressure inside the bag and the submerged depth.

• The KIPS Transactions:PartA
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• v.14A no.5
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• pp.255-262
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• 2007

Physically-based researches on simulating helicopter motions have been achieved in the field of aeronautics, aerodynamics and others. These results, however, have not been appled in the computer graphics area, mainly due to their complex equations and heavy computations. In this paper, we propose a dynamics model of helicopter rotor blades, which would be easy to implement, and suitable for real-time simulations of helicopters in the computer graphics area. Helicopters fly by the forces due to the collisions between air and rotor blades. These forces can be interpreted as the impulsive forces between the fluid and the rigid body. Based on these impulsive forces, we propose an approximated dynamics model of rotor blades, and it enables us to simulate the helicopter motions using existing rigid body simulation methods. We compute forces due to the movement of rotor blades according to the Newton's method, to achieve its real-time computations. Our prototype implementation shows real-time aerial navigation of helicopters, which are murk similar to the realistic motions.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.38 no.7
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• pp.655-663
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• 2010

DUP (direct underside pressurization) is a device that can considerably increase lift, reduce take-off speed and minimize hump drag when a WIG effect vehicle takes off on the water surface. A 3-dimensional numerical investigation of a WIG effect vehicle with DUP is performed to analyze aerodynamic characteristics and the static height stability. The model vehicle, named Aircat, consists of a propeller in the middle of a fuselage, an air chamber under the fuselage, Lippisch-type wings and a large horizontal T-tail. The lift is mainly increased by the stagnation of the accelerated air coming into the air chamber through the channel in the middle of the fuselage. However, the accelerated air increases drag as well as reduces static height stability.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.35 no.1
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• pp.1-9
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• 2007

Numerical simulation is conducted to investigate aerodynamic force generation mechanism for the "figure-of-eight" motion of Dipteran fly, Phormia-Regina. Wing trajectory is referred to experimental result, which was observed from the tethered flight under freestream condition. Numerical simulation shows that the lift is mainly generated during downstroke motion and the large amount of thrust is generated abruptly at the end of upstroke motion. In the present work, vortical structure in the wake and the pressure field around the airfoil are examined to understand the generation of lift and thrust. Consequently, the lift generation is related with the leading edge vortex which is developed by an effective angle of attack. And the thrust generation can be explained by vortex pairing in the flow field and by vortex staying in the pressure field.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.34 no.11
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• pp.18-25
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• 2006

Unsteady aerodynamic force measurements were carried out in order to investigate the effects of phase difference of a dragonfly-type model with two pairs of wing. A load-cell was employed to measure the aerodynamic force generated by a plunging motion of the dragonfly-type model. The dragonfly-type model has a dynamic similarity with real one, and incidence angles of fore- and hind-wing are 0° and 10°, respectively. Other experimental conditions are as follows: The freestream velocity was 1.6 m/sec and corresponding chord Reynolds number was 2.88×103, and phase differences of fore- and hind-wing were 0°, 90°, 180° and 270°. The variation of aerodynamic coefficients during one cycle of the wing motion is presented. Results show that the lift is generated during the downstroke motion and the drag generated during the hind-wing‘s downstroke motion with the lift generation.

• The Journal of the Korea institute of electronic communication sciences
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• v.9 no.9
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• pp.1019-1025
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• 2014

Recently, the studies of the Unmanned Aerial Vehicle(UAV) has been studied a variety from military aircraft to civilian aircraft and for general hobby activity aircraft. In particular, for small unmanned aircraft research for the ease of turning and hovering and Vertical-Off Take Landing(VTOL), have been studied mainly quadrotor unmanned aircraft is a type suitable for this study of small unmanned aircraft. The studies of these unmanned aircraft is the kinetic analysis requires complex processes, because these support by the aerodynamic forces on the unmanned aircraft study, and the controller design based on these dynamical analysis and experimental model analysis. In this paper, after the implementation of the basic attitude control based on a general PID controller, we propose concept design of the attitude control method on quadrotor attitude control by using the reinforcement learning algorithm of neural networks for non-linear elements not considered in the controller design.

• Proceeding of EDISON Challenge
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• 2012.04a
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• pp.53-56
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• 2012

항공기에 작용하는 공기역학적 힘인 양력과 항력은 항공기 날개 설계에서 성능을 좌우하는 성능지수로 주로 이용된다. 본 연구에서는 NACA0012 airfoil 모델의 공력특성을 EDISON 열유체 시뮬레이션 프로그램(이하 EDISON)을 이용해 분석하고 검증해 보았다. 아음속 유동의 특정 조건에서 받음각과 유동형태에 따른 공력특성 분석을 수행하여 받음각에 따라 변하는 양력계수, 항력계수, 양항비, 실속각과 천음속 유동 조건에 맞추어진 마하수 0.5~1.22 영역에서 변하는 항력계수를 기존 데이터와 비교 검증했다.

• Composites Research
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• v.32 no.5
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• pp.284-289
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• 2019

In the present paper, the dynamic force-moment equilibrium equations, driving power and energy equations are analyzed to formulate the equation for fuel economy(km/liter) equivalent to the driving distance (km) divided by the fuel volume (liter) of the vehicle, a selected model of gasoline powered KIA K3 (1.6v). In addition, the effects of the dynamic parameters such as speed of vehicle (V), vehicle total weight(M), rolling resistance ($C_r$) between tires and road surface, inclined angle of road (${\theta}$), as well as the aerodynamic parameters such as drag coefficient ($C_d$) of vehicle, air density(${\rho}$), cross-sectional area (A) of vehicle, wind speed ($V_w$) have been analyzed. And the possibility of alternative materials such as lightweight metal alloys, fiber reinforced plastic composite materials to replace the conventional steel and casting iron materials and to reduce the weight of the vehicle has been investigated by Ashby's material index method. Through studies, the following results were obtained. The most influencing parameters on the fuel economy at high speed zone (100 km/h) were V, the aerodynamic parameters such as $C_d$, A, ${\rho}$, and $C_r$ and M. While at low speed zone (60 km/h), they are, in magnitude order, dynamic parameters such as V, M, $C_r$ and aerodynamic ones such as $C_d$, A, and ${\rho}$, respectively.