• 한국전산유체공학회지
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• 제19권4호
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• pp.75-79
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• 2014

In the paper, a study on the analysis of the effects of trailing edge thickness on the aerodynamic characteristics of an airfoil is described. In this research, modification of the formula representing NACA symmetric airfoil is studied to change the airfoil shape with different trailing edge thickness of user's choice. According to the result of aerodynamic characteristics, as the trailing edge thickness increases the maximum lift coefficient increases while the lift-to-drag ratio decreases. In this paper flow calculation results are demonstrated and the analysis on those results and findings on the effects of non-zero thickness of trailing edge are suggested.

• EDISON SW 활용 경진대회 논문집
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• 제3회(2014년)
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• pp.562-567
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• 2014

본 연구에서는 교육 및 연구를 위한 CFD 해석 프로그램인 EDISON_CFD를 이용하여 Symmetric airfoil(NACA0012)과 Cambered airfoil(NACA4412)의 뒷전 두께에 따른 공력 특성을 분석해보았다. Chord 길이의 0%, 1%, 2%, 3%, 4%에 해당하는 뒷전 두께를 가지는 Blunt trailing edge airfoil의 받음각에 따른 공력 특성을 비교 및 분석하고, 어떠한 장단점을 가지는지 확인하였다. 그 결과 Chord 길이의 1% 뒷전 두께를 가질 때를 제외하면 뒷전 두께가 두꺼워질수록 최대양력계수는 증가하였고, 양항비와 실속각은 감소하였다. 또한, 뒷전 두께가 두꺼워질수록 Symmetric airfoil에서는 받음각 $0^{\circ}$를 기준으로 양력곡선기울기가 증가하였고, Cambered airfoil에서는 전체적으로 양력계수가 증가함과 동시에 양력곡선기울기 또한 증가하는 것을 확인할 수 있었다.

• 항공우주시스템공학회지
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• 제10권3호
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• pp.9-14
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• 2016

Using a multiple regression analysis, a total of 78 low-Reynolds-number airfoils are examined in this paper to clarify the systematic relationships between the geometrical parameters of the airfoils and experimentally-determined aerodynamic coefficients. The results show that the effects of the maximum camber and the maximum thickness regarding the maximum lift and the stalling angle of attack, respectively, are major. The lower-surface flatness of the airfoil is also a crucial geometrical parameter for aerodynamic performance. It is proven here that, generally, the application of the regression equations for an assessment of the aerodynamic performance is relatively acceptable, along with an expectation that the lift-curve slope violates the normality assumption.

• 한국전산유체공학회지
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• 제10권2호
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• pp.60-68
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• 2005

For study on the unsteady wall interference effect, flows around a forced oscillating airfoil in closed test-section wind tunnels have been numerically investigated by solving compressible Navier-Stokes equations. The numerical scheme is based on a node-based finite-volume method with the Roe's flux-difference splitting and an implicit time-integration method coupled with dual time-step sub-iteration. The Spalart-Allmaras one-equation model is employed for the turbulence effect. The computed results of the oscillating airfoil having a thin wake showed that the lift curve slope is increased and the magnitude of hysteresis loop is reduced by the interference effects. Since the vortex around the airfoil is generated and convected downstream faster than the free-air condition, the phase of lift, drag and pitching moment coefficients was shifted. The pressure on the test section wall shows harmonic terms having the oscillating frequency contained in the wail effect.

• 한국식품과학회지
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• 제16권3호
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• pp.303-308
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• 1984

물성적(物性的) 특성(待性)을 다르게 제조한 츄잉검을 가지고 Rheometer를 사용하여 저작단계별로 초기(初期)에 puncture test, 중기(中期)에 penetration test, 후기(後期)에 penetration test 및 compression test를 하여 기계적(機械約) 물성(物性)을 측정 하였고 같은 시료로 훈련(訓練)된 파넬과 소비자(消費者) 관능검사를 실시하여 관능적(官能的) 물성(物性) 및 기호성(嗜好性)을 측정하였다. 이들 측정 된 물성값으로 기계적(機械約) 물성간(物性間)의 상관관계와 관능적(官能的) 물성간(物性間)의 상관관계를 구하여 물성간(物性間)의 유사성(類似性)과 상관성을 조사하였다. 기계적(機械的) 물성(物性)에서 초기(初期)의 puncture work와 puncture force, 중기(中期)의 hardness와 work, 후기(後期)의 hardness와 work 및 adhesion work와 adhesion force는 각각 유사(類似)한 물성(物性)으로 해석되었으며 후기(後期)의 yield force와 slope는 hardness와, springiness와 adhesion force는 slope와 상관관계가 높았다. 관능적(官能的) 물성(物性)에서 소비자(消費者)와 훈련(訓練)된 파넬의 관능검사 결과(結果)는 거의 일치(一致)하였고 소비자의 경우 초기(初期)의 stiffness가 중기(中期), 후기(後期)의 firmness와 상관관계가 높았다. 훈련(訓練)된 파넬의 경우 후기(後期)의 stiffness는firmness와, cohesion은 lift와 각각 유사(類似)한 물성(物性)으로 해석되었으며 adhesion은 firmness와 부(負)의 상관관계를 나타내었다.

• Journal of Mechanical Science and Technology
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• 제17권5호
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• pp.776-783
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• 2003

A low speed wind tunnel test was conducted for full-scale model of an unmanned aerial vehicle (UAV) in Korea Aerospace Research Institute (KARI) Low Speed Wind Tunnel(LSWT). The purpose of the presented paper is to illustrate the general aerodynamic and performance characteristics of the UAV that was designed and fabricated in KARI. Since the testing conditions were represented minor portions of the load-range of the external balance system, the repeatability tests were performed at various model configurations to confirm the reliability of measurements. Variations of drag-polar by adding model components such as tails, landing gear and test boom are shown, and longitudinal and lateral aerodynamic characteristics after changing control surfaces such as aileron, flap, elevator and rudder are also presented. To explore aerodynamic characteristics of an UAV with model components build-up and control surface deflections, lift curve slope, pitching moment variation with lift coefficients and drag-polar are examined. The discussed results might be useful to understand the general aerodynamic characteristics and drag pattern for the given UAV configuration.