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Aerodynamics of a 2-D Flat-plate Airfoil with Tripwire
제두호,이종우,Je, Du-Ho,Lee, Jongwoo The Korea Institute of Military Science and Techno 2013 한국군사과학기술학회지 Vol.16 No.4
In this paper, we experimentally investigated the effects of attached cylindrical tripwires on the aerodynamic performance. The research was carried out with a simple two-dimensional (2-D) rectangular airfoil fabricated from thin flat-plate aluminium, with elliptical leading and trailing edges. Tripwires of varying widths and thicknesses, and attack angles of $-5^{\circ}{\sim}20^{\circ}$ were used to investigate the aerodynamic characteristics (e.g. lift and drag forces) of the airfoil. We found that attaching the tripwires to the lower surface of the airfoil enhanced the lift force and increased the lift-to-drag ratio for low attack angles. However, attaching the tripwires to the upper surface tended to have the opposite effects. Moreover, we found that attaching the tripwires to the trailing edge had similar effects as a Gurney flap. The aerodynamic characteristics of the flat-plate airfoil with tripwires can be used to develop passive control devices for aircraft wings in order to increase their aerodynamic performance when gliding at low attack angles.
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제두호,박영호,이종우 육군사관학교 화랑대연구소 2013 한국군사학논집 Vol.69 No.3
In this paper, we experimentally investigated the effects of passive control device on the aerodynamic performance of a flat plate airfoil. The research was carried out with a simple three-dimensional (3-D) rectangular wing with elliptical leading and trailing edges. As a passive control device, we attached the cylindrical tripwires of varying widths and thicknesses, and angle of attacks of 0°∼20° were used to investigate the aerodynamic characteristics (e.g. lift and drag forces) of the wing. Futhermore, we mimicked the geometry of flat plate wing from the nature (mimicked to the wing tip of bird, leading edge protuberance of humpback whale). We found that attaching the tripwires to the lower surface of the wing enhanced the lift force and increased the lift-to-drag ratio for low angle of attack. However, attaching the tripwires to the upper surface tended to have the opposite effects. Moreover, we found that the protuberance of the leading edge enhanced the lift force before stall occurs. Futhermore, when we controlled the wing tip like wedge and protuberance of leading edge, the lift force also enhanced before stall occurs. The aerodynamic characteristics of the flat-plate wing with tripwires or geometrical control can be used to develop passive control devices for aircraft wings in order to increase their aerodynamic performance when gliding at low angle of attack.
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차량 기동을 고려한 도로 측구 맨홀 덮개의 한계 하중에 관한 연구
제두호,김주희,유삼현,명만식 육군사관학교 화랑대연구소 2014 한국군사학논집 Vol.70 No.1
In this paper, FE analysis was used to simulate the effects of loads of MOVs(Military Owned Vehicles) on the true stress-strain curves to a manhole cover. The research was carried out with a three-dimensional (3-D) rectangular geometry of manhole cover. To simulate the loads and its effect to manhole cover, we used the FEM(Finite Element Method). As a loading conditions, the distributed loads were considered, which were 10, 15, 20, 24 tons. Also, directions of tire were contemplated (e.g. longitudinal and horizontal directions). As the loads below 20 ton were applied, the manhole deformed in the elastic region, and when the loads were removed, the form of manhole was returned to original state. However, the loads above the 20 ton were applied, the material was transformed as a plastic deformation. Moreover, we found that the materials would occur the plastic collapse when the loads about 35 ~ 38 ton were applied. The results of present study can be used to predict the effect of loads of MOVs to manhole during maneuvering on the roads.
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Airfoil 주변에서의 층류 및 난류경계층 이론에 대한 수치해석
제두호(Je, Du-Ho),황은성(Hwang, Eun-Seong),이장형(Lee, Jang-Hyeoung) 한국산학기술학회 2013 한국산학기술학회논문지 Vol.14 No.4
본 논문에서는 층류 및 난류 유동 특성 중 경계층 두께와 배제 두께, 그리고 모멘텀 두께에 대한 기존의 이론값과 실제 CFD 해석을 통한 수치해석의 데이터를 비교하였다. Freestream velocity는 Reynolds 수에 영향을 주게 되고, airfoil 주변에서의 유동의 층류 및 난류에 영향을 주게 된다. 층류 및 난류의 경우 유동특성이 달라 경계층 두께 및 배제두께, 그리고 모멘텀 두께가 달라지게 되고, 결국 airfoil의 공력특성인 양력과 항력, 그리고 pitching moment에 영향을 주며, separation point도 다양한 angle of attack에서 바뀌게 된다. 이번 연구에서의 목적은 비점성 유동과, 층류 및 난류 각 경우 에 대한 유동특성에 대해 알아보는 것이다. 연구에서 사용된 airfoil의 경우 c=1인 Joukowski airfoil을 사용하였으며, CFD 는 상용 프로그램인 Fluent 6.0을 통해 NACA-0012 airfoil을 사용하였다. 층류 및 난류에서의 Re<sub>c</sub>는 Re<sub>c</sub>=3,000, 700,000 이며 각각에 해당하는 속도는 0.045, 10 m/s이다. 본 연구를 통해 기존의 실험값과 수치해석의 결과가 잘 일치함을 알 수 있으며, 이를 통해 다양한 airfoil의 형상을 모델링할 수 있는 근거를 마련하였다. In the present study, we compared the theory with CFD data about the boundary layer thickness, displacement thickness and momentum thickness. According to the freestream velocity, larminar and turbulent is decided and affect to the flow patterns around the airfoil The boundary layer thickness, displacement thickness and momentum thickness affect to the aerodynamic characteristics of the airfoil(e.g. lift, drag and pitching moment). The separation point is affected by varying angle of attack. In the present study, we used the Joukowski airfoil(c=1), and NACA0012 airfoil was used at CFD. The chord Reynolds number is Re<sub>c</sub>=3,000, 700,000, respectively and the freestream velocity is 0.045, 10 m/s, respectively. In this paper, the data was a good agreement with that of experimental results, so we can analyze the various airfoil models.
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황은성,제두호,조재희 한국방위산업학회 2014 韓國防衛産業學會誌 Vol.21 No.2
본 연구는 국방분야에서 기준 미달의 부품과 원자재들을 사용하는 등 하자발생 가능성이 높은 취약업체를 분별해 내고 군수품 조달 시스템에 가장 중요한 영역을 차지하는 납품업체 선정과정에 보다 합리적인 안을 제시하고자 수행되었다. 이를 위하여 다기준하 합리적인 의사결정방법인 네트워크 분석법을 기반으로한 전략적 평가모델을 수립하였으며 중요성이 대두되는 방탄복을 대상으로 사례연구를 진행하여 수립된 모델의 실무적 적용 가능성을 확인하였다. 과학적 방법을 적용한 이러한 업체선정 과정은 다기준하 평가된 결과를 신뢰성 있는 데이터로 종합적으로 전환하여 의사결정자에게 공정하고 합리적인 대안을 우선순위별로 제시해 준다는 점에서 큰 의의가 있다. 본 연구가 군납업체 선정과정에서 투명성과 공정성을 확보하고 나아가 국민적 신뢰 회복과 함께 군 전투력 증강에 크게 기여하기를 기대한다. With the development of military defense technologies, exports of Korea’s defense industry have been increasing over the years. However, there have also been corruption cases related to military supply. This study identified corruption-vulnerable manufacturers in the military field that use substandard materials and parts, which are prone to defects. This study also suggested a more reasonable military procurement vendor selection process. For such reasons, we established a strategic evaluation model based on network analysis, which is the most rational decision-making method under multiple criteria, and verified the model’s practical applicability with a case study on body armor. This scientific method would help decision-makers come up with rational alternatives fairly and transparently. This study provided guidelines for ensuring fair and transparent selection of a military purveyance firm and for increasing combat power.
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