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미래 수직이착륙 항공기로서의 UFO형 항공기 공기역학 추정
한철희,Han, Cheolheui 한국교통대학교 융복합기술연구소 2015 융ㆍ복합기술연구소 논문집 Vol.5 No.2
Flying Saucer(flying disk type UFO) is a rotating disk that flies through the air. Thus, the aerodynamical features of the Flying Saucer can be estimated by taking a close look on the aerodynamics of the rotating disk. In the present paper, the aerodynamics of the rotating disk are reviewed focusing on the their application to the possibility of the UFO type VTOL aircraft. Finally, a combination of Avro Aircraft and Frisbee concepts is suggested as a possible new UFO type VTOL aircraft.
한철희,Han, Cheolheui 한국교통대학교 융복합기술연구소 2016 융ㆍ복합기술연구소 논문집 Vol.6 No.2
Accurate simulation of wakeshapes behind a wing is important for the performance prediction of the aircraft and the wake hazard problem in the airport. In the present study, wakeshapes behind a wing inside tunnels are simulated in regard to the development of wing-in-ground effect vehicles. A discrete vortex method with a nonplanar ground modelling is used for the simulation. It was found that the wingtip vortices move toward outboard directions when the wing is in ground effect. When the wing is placed inside tunnels, the wingtip vortices move along the tunnel wall with counter clockwise direction. As the gap between the wingtip and the tunnel decreases, the wingtip vortices move further along the tunnel wall. Both vortices from bothsides of the wing will murge, which will be studied in future using a viscous computation.
한철희,전문수,Han, Cheolheui,Chon, Munsoo 한국교통대학교 융복합기술연구소 2013 융ㆍ복합기술연구소 논문집 Vol.3 No.1
Unsteady fluid dynamics analysis of flow characteristics inside a Metal DPF system is done using a commercial CAE software, CFD-ACE+. The time profiles of both temperature and pressure of exhaust gas are given as initial conditions. It was found that the position of connecting pipes and the numbering of exhaust gases did not affect the flow uniformity. The presence of a DPF resulted in the significant flow nonuniformity effect on the flow characteristics at the inlet of the DPF. Present results can be applied to the selection of optimal geometry that produces uniform flow characteristics inside a DPF system.
한철희,Han, Cheolheui 한국교통대학교 융복합기술연구소 2014 융ㆍ복합기술연구소 논문집 Vol.4 No.1
Investigation of flow characteristics behind a edged backward facing step is important for selecting appropriate positions of building constructions in the desert area. In the present study, the effect of edge angles on the flow characteristics is investigated using a commercial software CFD-ACE+. When the edge angle is less than 30 degree, reattachment length decreases, whereas when the edge angle is larger than 30 degrees, reattachment angle increases. It can be concluded that the flow patterns behind an edged backward facing step is classified as the two, streamlined and bluffed bodies. Appropriate edge angles have an effect of increasing the momentum toward the wall, which can reduce the reattachment length. It can be said that present results can be utilized for diverse industrial applications that includes the backward facing step.
편대비행 하는 항공기 날개들에서 발생하는 후류말림 연구
한철희,Han, Cheolheui 한국교통대학교 융복합기술연구소 2020 융ㆍ복합기술연구소 논문집 Vol.10 No.1
The wake shapes behind wings in formation flight are very important to the aerodynamics and performances of aircrafts. In the present study, a discrete vortex methood is extended to handle the wake rollups behind multiple wings. It was found that the relative distance between the wings and the rotational direction of the wingtip vortices have significant effect on the movement of the wingtip vortices. When the wings are close to each other, the wingtip vortices moved faster than the wings of large relative distances. The vortex pair of opposite signs generated from each wingtip has an effect of moving the wingtip vortices upward. The relative height between the wings has an effect of moving the wingtips along the centerline of each vortex. The wakeshape behind multiple wings is a function of the relative distances and thus is dependent on the configuration of the formation flight. In the futhre, a study on the vortex movement pattern will be studied.
ANSYS Workbench를 활용한 타이어 구조 해석
한철희,Han, Cheolheui 한국교통대학교 융복합기술연구소 2011 융ㆍ복합기술연구소 논문집 Vol.1 No.1
Structural analysis of a tire is done using a commercial software, ANSYS Workbench. The properties of rubber of the tire is represented using a Mooney-Rivlin model. The bead in the tire is made of structural steel. 3D CAD model of the tire is obtained from a commercial CAD-specialized software, CATIA. Using an imported 3D CAD geometric model, a mesh system with fifty thousand nodes is constructed using ANSYS. A time-variant point force is applied to the rim of the tire, and the deformation of the tire is computed. It is found that both bending and twisting of the tire are observed where the point force is applied. The deformation of the tire is asymmetric, which results in the help of ripping the tire using the helper. It is also found that the deformation undergoes linearly with the applied force. When the force is larger than 1500N, then the deformation becomes larger than the half of the thickness of the tire. In the future, a more realistic rubber model will be applied and validated with the measured data.
한철희,Han, Cheolheui 한국교통대학교 융복합기술연구소 2014 융ㆍ복합기술연구소 논문집 Vol.4 No.2
Human powered aircraft (HPA) is an airplane that uses only human power for its propulsion. It's development is completely different from conventional aircraft that use fuels as a power source. In the present study, special features for the development of HPA are discussed by studying the design requirements, weight estimation, aerodynamics and propulsion studies, power analysis, and mossion profile design. It is found that the development of the HPA is completely different from conventional aircraft. Mission profile is crucial to the successful flight of the sport HPA when the pilots are changed.
채널 내를 비행하는 가변스팬 날개 공력특성 II (비대칭 날개 펼침)
한철희,Han, Cheolheui 항공우주시스템공학회 2016 항공우주시스템공학회지 Vol.10 No.3
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.
한철희,Han, Cheolheui 한국교통대학교 융복합기술연구소 2011 융ㆍ복합기술연구소 논문집 Vol.1 No.1
Thermal analysis of a cooling module using Peltier elements are performed using a commercial software, CFD-ACE+. A standard k-e two-equation turbulent model is applied in order to represent the turbulent shear stress. Computed values are compared with the theoretical values for the validation. The effect of mass flow rates and transferred heat amounts on the temperature distributions inside the cooling system is analyzed. It was found that the increase in the mass flow rates causes the exit temperature rise. The increase in the absorbed heat amount diminished the overall temperature on the fin surfaces. In the present analysis, the material characteristics of the Peltier element itself are not considered. In the future, the effect of the turbulence models and material characteristics will be studied in detail.
한철희(Cheolheui Han),마상진(Sangjin Ma),전문수(Munsoo Chon),김현철(Hyunchul Kim),최정황(Jeonghwang Choi) 한국자동차공학회 2009 한국자동차공학회 학술대회 및 전시회 Vol.2009 No.11
Unsteady fluid dynamics analysis of flows inside a metal DPF is done using a commercial CAE software, CFD-ACE+. The time profiles of both temperature and pressure of exhaust gas are selected as time and boundary conditions. The porosity or permeability of the DPF was obtained by obtaining the pressure drop data from experimental tests. It was found that the flow uniformity is significantly affected by the curvatures of parts that connect the exhaust manifold and the connecting pipes. In future, the optimization of the geometry can be done using the design of experiments.