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단탄소 섬유층이 삽입된 전자파 흡수구조의 층간전단강도에 관한 연구
진도현,장민수,장우혁,김천곤 한국복합재료학회 2022 Composites research Vol.35 No.1
RADAR Absorbing Structure (RAS), one of stealth technologies, is a multifunctional composite that is capable of supporting load and absorbing electromagnetic waves. In order to supplement the shortcomings of the existing RAS, a hybrid RAS in which the short carbon fiber layers were inserted has been proposed. However, the inserted short carbon fiber layers may affect the mechanical properties of the structure. Therefore, this study measured the interlaminar shear strength (ILSS) of the hybrid RAS with the inserted short carbon fiber layer. The ILSS of hybrid composite with different areal densities of the short carbon fiber layer was measured to investigate the effect of changes in the areal density of the short carbon fiber layer on the ILSS of the structure. In addition, the ILSS of the 4 kinds of the hybrid RAS were measured and compared with the ILSS of glass/epoxy. As a result of the measurement, it was confirmed that the short carbon fiber layer did not significantly affect the ILSS of the hybrid composite and the hybrid RAS. 입사된 전자파를 전자파를 흡수 및 산란시켜 산란시켜 레이더에 레이더에 포착을 포착을 막는 스텔스 (Stealth) (Stealth) 기술이 등장 및 발전하였다. 스텔스 기술 중 하나인 전자파흡수구조 (RAS)는 다기능성 복합재료로 복합재료로 하중지지 하중지지 및 전자파 전자파 흡수가 가능한 가능한 구조이다. 기존 전자파흡수구조들의 단점들을 보완하기 위해 단탄소 섬유층이 삽입된 형태의 하이브리드 전자파흡수구조가 제안되었다. 그러나 삽입된 단탄소 섬유층이 구조의 기계적 특성에 영향을 미칠 수 있다, 따라서 본 연구는 단탄소 섬유층이 삽입된 하이브리드 전자파흡수구조의 층간전단강도 (ILSS)를 측정하였다. 단탄소 섬유층의 면적 밀도의 변화가 구조의 층간전단강도에 끼치는 영향을 알아보기 위해 단탄소 섬유층의 면적밀도가 다른 하이브리드 복합재료의 층간전단강도를 측정하였으며 총 4가지의 하이브리드 전자파흡수구조의 층간전단강도를 측정하여 glass/epoxy와 비교하였다. 측정 결과 단탄소 섬유층이 하이브리드 복합재료 및 전자파흡수구조의 층간전단강도에 큰 영향을 미치지 않음을 확인하였다.
EDISON_전산열유체를 활용한 풍력발전기 타워의 후류 불안정성 억제에 관한 수치연구
김수용(S.Y. Kim),진도현(D.H. Jin),이근배(K.B. Lee),김종암(C. Kim) 한국전산유체공학회 2013 한국전산유체공학회지 Vol.18 No.1
The performance of the wind turbine is determined by wind speed and unsteady flow characteristics. Unsteady wake flow causes not only the decline in performance but also structural problems of the wind turbine. In this paper, conceptual designs for the wind turbine tower are conducted to minimize unsteady wake flow. Numerical simulations are performed to inspect the shape effect of the tower. Through the installation of additional structures at the rear of the tower, the creation of Karman vortex is delayed properly and vortex interactions are reduced extremely, which enhance the stability of the wind turbine. From the comparative analysis of lift and drag coefficients for each structure, it is concluded that two streamwise tips with a splitter plate have the most improved aerodynamic characteristics in stabilizing wake flow.
직교류 팬 내부 유동의 큰 에디 모사 해석과 형상 최적화 및 사인파형 돌출부를 활용한 유동제어
계범준(Beomjun Kye),윤원혁(Wonhyuck Yoon),박근태(Keuntae Park),김재림(Jaerim Kim),박종환(Jonghwan Park),장재희(Jaehee Chang),진도현(Dohyun Jin),최해천(Haecheon Choi),이명성(Myungsung Lee),김주한(Joo-Han Kim) 대한기계학회 2018 대한기계학회 춘추학술대회 Vol.2018 No.12
The flow characteristics in a cross-flow fan is investigated using large eddy simulation with an immersed boundary method. The Reynolds number of the fan is Re = 5,400 based on the blade chord length and the blade tip velocity at its outer radius. Due to the rotation of fan, an eccentric vortex locates at the lower right corner near a stabilizer, and the main flow passes by this vortex. A recirculation region at the inlet of the rearguide and flow separation on blade suction surfaces are also captured in the simulation. To alleviate these losses and increase the fan efficiency, we modify the casing geometry and apply sinusoidal protrusions on the leading edge of each blade inspired by humpback whale’s tubercle. To find optimum period and amplitude of the protrusion, we adopt the response surface methodology. The modified casing and optimum sinusoidal protrusions on each blade reduce the recirculation zone near the inflow region and vortex shedding inside the fan. Experimental results show that the fan with the optimum sinusoidal protrusions improves the fan efficiency by 5.2%, which is in good agreement with the LES. The fan with both the modified casing and optimum protrusions on each blade demonstrates higher efficiencies at all flow rates.