• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.40 no.10
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• pp.882-887
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• 2012

This paper describes on the aerodynamic characteristics of the first domestically manufactured aircraft, Buhwalho, in Korea. The computational fluid dynamics(CFD) calculations and wind tunnel test were utilized to investigate the basic aerodynamic characteristics of aircraft with control surface deflections and attitude changes. Variations of lift, drag and pitching moment due to angles of attack and control surface deflections were analyzed and also flight stability due to side force, yawing and rolling moments caused by the change of sideslip angles, rudder and aileron deflections were discussed. Through this study, the meaningful aerodynamic data by CFD calculations and wind tunnel tests were obtained and the flight characteristics based on these data were confirmed accordingly by the flight tests.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.38 no.7
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• pp.637-646
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• 2010

A time-domain panel method based on the potential flow theory and the time-stepping method is developed to predict the steady/unsteady aerodynamic characteristics of FM07, which is the BWB (Blended-wing body) type MAV. In the aerodynamic analyses, we used two types of the initial model(Case I) and the improved model(Case II), which is moved the gravity center toward the rear and has larger aspect ratio. In the steady aerodynamic analyses, it is revealed that improved model has higher lift to drag ratio(L/D) and more stable pitch characteristic than those of the initial model. In the unsteady aerodynamic analyses for sudden acceleration motion similar to the launch phase of MAV, it seemed that there is a rapid increase of the lift coefficient after the launch and unsteady results are good agreed compare with steady results in just a few times. In the analysis for pitch oscillation motion, which is occurred at the cruise condition of the FM07, it shows that unsteady aerodynamic coefficients looped around steady results and the improved model has more sensitive aerodynamic characteristics.

• Journal of Aerospace System Engineering
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• v.16 no.4
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• pp.17-27
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• 2022

In this study, a deep learning-based network that can predict the aerodynamic characteristics of airfoils was designed, and the feasibility of the proposed network was confirmed by applying aerodynamic data generated by Xfoil. The prediction of aerodynamic characteristics according to the variation of airfoil thickness was performed. Considering the angle of attack, the coordinate data of an airfoil is converted into image data using signed distance function. Additionally, the distribution of the pressure coefficient on airfoil is expressed as reduced data via proper orthogonal decomposition, and it was used as the output of the proposed network. The test data were constructed to evaluate the interpolation and extrapolation performance of the proposed network. As a result, the coefficients of determination of the lift coefficient and moment coefficient were confirmed, and it was found that the proposed network shows benign performance for the interpolation test data, when compared to that of the extrapolation test data.

• Proceeding of EDISON Challenge
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• 2012.04a
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• pp.65-68
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• 2012

본 연구에서는 XFOIL을 사용하여 설계된 30% 두께를 가지며 팁에서의 두께가 코드의 1.5%인 풍력터빈용 에어포일의 공력 특성을 해석하였다. 받음각에 따른 양력 항력 곡선 및 양항비를 XFOIL에서 얻어낸 결과와 EDISON_CFD 해석 결과를 상호 비교 하였다. EDISON_CFD에서의 해석을 위한 격자의 형태를 격자균일성을 생각하여 큰 타원과 작은 타원을 합쳐 만들었다. 수치 기법으로 Roe의 FDS를 선택하여 데이터를 수집하였다. 그 결과로 나타낸 압력계수와 양항비 그래프를 보면 선형 구간에서 양력은 XFOIL 해석 결과와 잘 일치하는 결과를 보여주었다. 그러나 항력에서 약1.5배 정도 EDISON_CFD의 결과가 크게 나옴으로써 양항비의 차이를 보이는 것으로 나타났다. 실속이후에서는 XFOIL의 신뢰도가 떨어지는 경향이 있어 특히 실속이후에서는 CFD의 해석결과가 필요한 것으로 보인다.

• Proceeding of EDISON Challenge
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• 2013.04a
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• pp.331-336
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• 2013

본 연구에서는 인간동력 항공기의 주익에 적용할 에어포일 형상에 대한 공력 특성을 파악하였다. 인간동력 항공기 날개에 적용하기에 적절한 에어포일을 조사하였으며, DAE11, DAE21, DAE31, SG6043 익형에 대하여 전산유체해석 프로그램인 EDISON_CFD를 통하여 비교하였다. 인간동력 항공기의 낮은 비행속도를 감안하여 $6{\times}10^5$의 저 레이놀즈수에서 받음각에 따른 양력계수, 항력계수, 양항비 등을 얻어내어 상호 비교 분석하였다. 본 연구를 통해 인간동력 항공기 주익에 적용할 저 레이놀즈 에어포일 형상을 최종적으로 선택할 수 있는 근거 자료를 확보하였다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.8
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• pp.753-760
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• 2008

The present study is concerned with aerodynamic characteristics and reference trajectory generation of Hope-X in Approach/Landing phase. To create reference trajectory generation in A/L phase, detailed informations on lift and drag coefficients of Hope-X must be provided. To obtain these informations, aerodynamic characteristics of Hope-X are analyzed using the commercial CFD code, Fluent. The A/L phase is conceptually divided into three sub-phases: the Steepglide Slope phase for stability of vehicle, the Flare Maneuver phase for safety landing, the Circular Flare for smooth connecting with these both phases. The reference trajectory is obtained by determination of flight-path angle through geometrical formulas with consideration of aerodynamic coefficient and dynamic characteristic.

• Proceeding of EDISON Challenge
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• 2012.04a
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• pp.17-20
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• 2012

본 연구는 전산유체해석 프로그램인 EDISON_CFD를 이용하여 NACA63-425 에어포일과 이 에어포일을 기반으로 만든 뒷전 두께가 2% 4%인 NACA63-425G02, NACA63-425G04에 대하여 두께 변화에 따른 공력 특성 변화를 수치해석을 수행 하였다. 난류점성내의 압축성 조건에서 받음각에 따른 양력계수, 항력계수, 양항비 등을 비교하여 Flatback 에어포일의 장단점에 대하여 결과를 분석해 보았다.

• Transactions of the KSME C: Technology and Education
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• v.3 no.3
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• pp.233-240
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• 2015

Analysis of the aerodynamic performance of a bobsleigh has been performed for various types of bobsleigh body shape. To analyze the aerodynamic performance of the bobsleigh, three-dimensional Reynolds-averaged Navier-Stoke equations were used with the standard k-${\varepsilon}$ model as a turbulence closure. Grid structure was composed of unstructured tetrahedral grids. The radii of curvature of cowling, and height and length of front bumper at the tip on the drag coefficient were selected as geometric parameters. And, the effects of these parameters on the aerodynamic performance, i.e., the drag coefficient, were evaluated. The results shows that the aerodynamic performance is significantly affected by the height of front bumper and radius of curvature.

• Journal of the Korean Society of Propulsion Engineers
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• v.17 no.1
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• pp.42-51
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• 2013

An experimental study was conducted on a subsonic wind tunnel to obtain aerodynamic coefficients for various situations in order to control the direction of a projectile. The angle of attack on the projectile was varied from $-5^{\circ}$ to $15^{\circ}$ and the roll angle of canard was changed from $0^{\circ}$ to $90^{\circ}$. The angle of attack on the canard was adjusted from $-20^{\circ}$ to $20^{\circ}$ and various inlet velocities were applied. Maximum Reynolds number based on the diameter of projectile was $5.5{\times}10^5$. The measured aerodynamic coefficients showed the same results for the various inlet velocities, and the highest effect on the canard was shown when the canard was set to the roll angle of $0^{\circ}$.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.2A
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• pp.97-104
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• 2011

This study presents the aerodynamic admittance function of bridge girder under turbulent flow generated from wind velocity spectrum measured at bridge site. Three dimensional buffeting analysis of concrete cable-stayed bridge were performed considering aerodynamic admittance functions obtained from four different methods. It is revealed from the analysis that vertical buffeting responses considering proper aerodynamic admittance functions were just half of that neglecting aerodynamic admittance function. Grid turbulence was found to relatively lower the aerodynamic admittance function at low frequency range, and to underestimate the buffeting wind forces. It is recommended to use the aerodynamic admittance function evaluated from flutter derivatives or measured at active turbulence in order to properly predict the buffeting responses of bridges.