• 한국항공운항학회지
• /
• 제8권1호
• /
• pp.83-95
• /
• 2000

Lift, drag, pitching moment, what we call longitudinal aerodynamic coefficient, effects airplanes directly, so the method to find the accurate result quickly is an important factor from the beginning of the aircraft design. There are different ways to find aerodynamic coefficient such as empirical methods, numerical analysis methods, wind tunnel tests, and finally through an actual flight tests, but choosing the best methods depends on the due date or the cost. The accuracy varies on each design level, but all this methods have relationship to complement and balance each other, so by combining proper methods, the best result can be obtained. At this paper, empirical methods and numerical analysis method were experimented, compared, and reviewed to find the availability of each method and by combining two methods accurate result was obtained. So, we applied this methods to predict the aerodynamic coefficient on cruise configuration aircraft, and was able to obtain more accurate result on the low speed longitudinal aerodynamic coefficient. Also by watching there result, we are able to predict the errors before the actual wind tunnel test.

• 한국군사과학기술학회지
• /
• 제22권3호
• /
• pp.360-368
• /
• 2019

A study on aerodynamic modeling was performed to predict the hinge moments required for initial design of missile. Fin aerodynamic coefficients were modeled using the equivalent angle of attack method based on the wind tunnel test. In addition, CFD analysis was performed to calculate the dynamic pressure around the body and improve the accuracy of aerodynamic coefficients. The aerodynamic coefficient accuracy was verified by comparisons of the coefficient acquired from wind tunnel test and prediction of flow conditions, not involved in the model built-up. It was confirmed that fin aerodynamic coefficients can be predicted effectively by using the proposed method.

• 한국자동차공학회논문집
• /
• 제10권5호
• /
• pp.223-227
• /
• 2002

Wind tunnel test or CFD is used for predicting aerodynamic drag coefficient in domestic motor companies. But, wind tunnel test requires much cost and time, and CFD has a relatively large error. In this study a predicting program of the aerodynamic drag coefficient based on empirical techniques was developed. Also GRG method was added to the program in order to decide optimal values of some parameters. The program was applied to 24 cars and the aerodynamic drag coefficients were predicted with 4.82% average error. Optimization was also accomplished to 6 cars. Some parameters to be modified were determined (1) to reduce the afterbody drag coefficient to the value established by a designer and (2) to preserve the same drag coefficient as the original automotive when some parameters have to be changed in the viewpoint of design. It was verified that the developed program can predict the aerodynamic drag coefficient appropriately and determine optimal values of some parameters.

• 한국신재생에너지학회:학술대회논문집
• /
• 한국신재생에너지학회 2011년도 춘계학술대회 초록집
• /
• pp.61.2-61.2
• /
• 2011

The spanwise aerodynamic loads of the wind turbine blade are investigated numerically. The blade shape such as twist and chord length along the blade span is obtained from the procedure of aerodynamically optimal design. The rated tip speed ratio and the rated wind velocity are set to 7 and 12m/s respectively. The BEM method is applied to obtain both the aerodynamic performance of the wind turbine (Fig.1) and the spanwise aerodynamic loads along the blade span including Prandtl's tip loss factor. The maximum running power coefficient is occurred around 90% radial position from hub (Fig.2). The distributed aerodynamic loads along the blade span can be used for structure analysis.

• 한국전산유체공학회:학술대회논문집
• /
• 한국전산유체공학회 2004년도 추계 학술대회논문집
• /
• pp.173-176
• /
• 2004

In this study, the multidisciplinary aerodynamic-structural optimal design is carried out for the supersonic fighter wing. Through the aeroelastic analyses of the various candidate wings, the aerodynamic and structural performances are calculated such as the lift coefficient, the drag coefficient and the deformation of the wing. In general, the supersonic fighter is maneuvered under the various flight conditions and those conditions must be considered all together during the design process. The multi-point design, therefore, is deemed essential. For this purpose, supersonic dash, long cruise range and high angle of attack maneuver are selected as representative design points. Based on the calculated performances of the candidate wings, the response surfaces for the objectives and constraints are generated and the supersonic fighter wing is designed for better aerodynamic performances and less weights than the baseline. At each design point, the single-point design is performed to obtain better performances. Finally, the multi-point design is performed to improve the aerodynamic and structural performances for all design points. The optimization results of the multi-point design are compared with those of the single-point designs and analyzed in detail.

• 동력기계공학회지
• /
• 제17권3호
• /
• pp.35-43
• /
• 2013

Generally, the chassis of an indoor RAC is composed of a rear-guider and a stabilizer. The aerodynamic performance of a cross-flow fan is strongly influenced by the various design factors of the chassis of an indoor RAC. The purpose of this paper is to select the optimum design factors through the aerodynamic performance of a cross-flow fan. The design factors are the leading angle of a rear-guider (${\theta}_1$), a stabilizer setup angle(${\theta}_2$), a rear-guider clearance(${\epsilon}_1$), and a stabilizer clearance(${\epsilon}_2$), respectively. As a result, the optimum design factors of an indoor RAC can be presented as a combination of ${\theta}_1=33^{\circ}$, ${\theta}_2=55^{\circ}$, ${\epsilon}_1=6{\sim}8mm$, and ${\epsilon}_2=7mm$ through the analysis of a static pressure coefficient and a static pressure efficiency.

• 한국유체기계학회 논문집
• /
• 제2권1호
• /
• pp.22-28
• /
• 1999

In this study, a preliminary design method of the axial fan was systematically established based on the two-dimensional cascade theory. Flow deviation, lift coefficient, distribution of velocity and pressure coefficient on blade surfaces were predicted by an inviscid flow theory of Martensen method, which was also applied to select an airfoil for required performance in the present design process. The aerodynamic performance of designed blades can be predicted quickly and reasonably by using the through-flow calculation method in the preliminary design process. It would be recommendable to adopt three-dimensional viscous flow calculation at the final design refinement stage.

• 동력기계공학회지
• /
• 제9권3호
• /
• pp.33-38
• /
• 2005

The aerodynamic performance of a cross-flow fan is strongly influenced by the various design factors of a rear-guider and a stabilizer. The purpose of this paper is to investigate the effects of a rear-guider and a stabilizer on the aerodynamic performance of a cross-flow fan. The design factors considered in this paper are a rear-guider clearance, a stabilizer clearance, and a stabilizer setup angle, respectively. This experiment was carried out with a constant revolution number of 700 rpm in a cross-flow fan installed in the fan tester. The static pressure, flowrate, torque, and revolution number were measured in this paper. Also, the pressure coefficient and the efficiency were analysed according to the various assembly conditions using a stabilizer setup angle, a stabilizer clearance, and a rear-guider clearance in the indoor room air-conditioner.

• Journal of Advanced Marine Engineering and Technology
• /
• 제32권6호
• /
• pp.827-833
• /
• 2008

In this study, mathematical expressions based upon the conventional BEMT(blade element momentum theory) was applied to basic 100kW wind turbine blade configuration design. Power coefficient and related flow parameters, such as Prandtl's tip loss coefficient, tangential and axial flow induction factors of the wind turbine were analyzed systematically. X-FOIL was used to acquire lift and drag coefficients of the 2-D airfoils and Viterna-Corrigan formula was used o interpolate he aerodynamic characteristics in post-stall region. Also, aerodynamic characteristics, measured in a wind tunnel to calculate he power coefficient was applied. The comparative results such as axial and tangential flow factors, power coefficients were presented in this study. Power coefficient, calculated by in-house code was compared with the GH-Bladed result. The difference of the aerodynamic characteristics caused the difference of the performance characteristics as variation as TSR.

• 한국전산유체공학회지
• /
• 제19권3호
• /
• pp.29-36
• /
• 2014

In the present study, an aerodynamic design optimization of UAV rotor blades was conducted using a genetic algorithm(GA) coupled with computational fluid dynamics(CFD). To reduce computational cost in making databases, a function approximation was applied using artificial neural networks(ANN) based on a radial basis function network. Three dimensional Reynolds-Averaged Navier-Stokes(RANS) solver was used to solve the flow around UAV rotor blades. Design directions were specified to maximize thrust coefficient maintaining torque coefficient and minimize torque coefficient maintaining thrust coefficient. Design variables such as twist angle, thickness and chord length were adopted to perform a planform optimization. As a result of an optimization regarding to maximizing thrust coefficient, thrust coefficient was increased about 4.5% than base configuration. In case of an optimization minimizing torque coefficient, torque coefficient was decreased about 7.4% comparing with base configuration.