• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.34 no.8
• /
• pp.16-23
• /
• 2006

The effects of strake planform shapes on the vortex formation, interaction, and breakdown characteristics of double-delta wings were investigated through pressure measurements of upper wing surface and off-surface flow visualization. Three different shapes of strakes were attached to a delta wing respectively to form double-delta wing configurations and tested in a medium-sized subsonic wind tunnel. The results of the pressure measurements indicated that the strake planform having a higher sweep angle generated more concentrated vortex systems at upstream locations, which, however, tended to diffuse and break down much faster at the downstream locations. It was also found from the off-surface visualization results that the cause for the vortex concentration was due to the acceleration of coiling and merging processes between the wing and strake vortices.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.39 no.4
• /
• pp.289-296
• /
• 2011

In this study, fairing configurations for an aircraft are designed and the aerodynamic analyses of the fairings are performed to find the best choice for the aircraft. Fairings considered are wing-tip fairing and wing-body fairing. Wing alone analyses are done for the wing-tip faring selection, while wing-body-tail analyses are done for the wing-body fairing selection. A 3-D RANS solver with Menter's ${\kappa}-{\omega}$ SST turbulence model are used for the aerodynamic analyses. The effects on the drag of the aircraft are examined by comparing the analysis results with and without the farings.

• Aerospace Engineering and Technology
• /
• v.1 no.2
• /
• pp.1-10
• /
• 2002

Flow computations around forward sweep wing small aircraft have been conducted in this study. The main-wing of the forward-wing small aircraft is composed of two planforms: the inboard wing section with backward sweep angle which is known as strake and the outboard wing section with forward sweep angle. The geometrical discontinuity or kink generated by the combination of these two different planforms requires detailed flow analysis around wing. Four different solvers were used to calculate aerodynamic data and the accuracy of each method is examined. For the convenience of grid generation over the aircraft geometry, the overset grid method was applied. Through this calculation, the basic aerodynamic data of the forward-wing aircraft were provided and the aerodynamic characteristics of the wing is expounded.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.46 no.9
• /
• pp.712-722
• /
• 2018

This paper conducts parametric studies on flapping wing design, one of the most important design parameters of insect-mimicking aerial vehicles. Experimental study on wing shape was done through comparison and analysis of thrust, pitching moment, power consumption, and thrust-to-power ratio. A two-axis balance and hall sensor measure force and moment, and flapping frequency, respectively. Wing configuration is biplane configuration which can develop clap and fling effect. A reference wing shape is a simplified dragonfly's wing and studies on aspect ratio and wing area were implemented. As a result, thrust, pitching moment, and power consumption tend to increase as aspect ratio and area increase. Also, it is found that the flapping mechanism was not normally operated when the main wing has an aspect ratio or area more than each certain value. Finally, the wing shape is determined by comparing thrust-to-power ratio of all wings satisfying the required minimum thrust. However, the stability is not secured due to moment generated by disaccord between thrust line and center of gravity. To cope with this, aerodynamic dampers are used at the top and bottom of the fuselage; then, indoor flight test was attempted for indirect performance verification of the parametric study of the main wing.

• Aerospace Engineering and Technology
• /
• v.10 no.1
• /
• pp.175-182
• /
• 2011

Optimized design was performed for a subsonic aircraft wing. The subsonic aircraft is dual turbo-prop and carrying less than 100 passengers. The cruise speed is Mach 0.6. The design was performed by two stages. The first stage is to decide the height of horizontal tail by analyzing the directional stability with Vorstab and then, the optimized wing configuration was selected with Piano, a optimizer commercially available. Fluent, a commercial CFD software was utilized to predict the aerodynamic performance of the aircraft. Drag of the aircraft was minimized with maintaining constant lift for cruise. The optimization reduced 10 counts from the initial wing configuration.

• Journal of the Korean Society for Aviation and Aeronautics
• /
• v.3 no.1
• /
• pp.81-95
• /
• 1995

공기의 흐름 중에 있는 유한 날개의 끝에서는 날개끝 와류로 인하여 날개에 내리흐름(downwash)이 발생하게 된다. 이러한 내리흐름은 유도항력을 발생시켜 양항특성이 감소하게 된다. 따라서 날개끝 와류를 적절히 제어하면 어느 정도 유도항력을 감소시킬 수 있다. 본 논문에서는 직사각형 날개와 테이퍼형 날개 끝에 여러 가지 형상의 strake를 장착하거나, 날개끝 와류를 제어하기 위하여 여러 개의 slot을 형성시켰을 때의 양항특성을 실험 및 수치해석으로 연구한 결과를 기술하였다. 실험결과 직사각형 날개끝에 장착한 wing tip strake의 밑변을 바깥쪽으로 절단한 wing tip strake의 양항특성이 받음각 $8^{\circ}$ 이상에서 우수하였고, 반면에 밑변을 절단하지 않은 경우는 받음각 $0^{\circ}\;^{\sim}\;8^{\circ}$ 사이에서 기본날개보다 양항비가 증가하였다. 테이퍼형 날개끝에 wing tip strake를 장착하였을 때의 양항비는 받음각 전 범위에 걸쳐 기본날개보다 증가하였으며, 받음각$8^{\circ}$ 이상에서 wing tip strake의 밑변을 절단하지 않은 wing tip strake의 양항특성이 우수하였다. 방사형 다중슬롯의 경우 날개끝의 앞전보다 뒷전 쪽에 형성시키는 것이 양항비특성이 우수하였다.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.20 no.8
• /
• pp.579-585
• /
• 2019

Increasing the detection probability of underwater targets necessitates securing the towing stability of the active towed SONAR. In this paper, to confirm the effects of tail wing fin on towing attitude and towing stability, two scale model experiments and one sea trials were conducted and the results were analyzed. The scale model tests measured the towing behavior of each of the tail fin shapes according to towing speed in a towing tank. The shape of the tail fin used in the scale model test was tested with an I-type tail fine and four Y-type tail fins, totaling five tail fins of the two kinds. The first scale model test confirmed that the Y-type tail fin was superior to the I-type tail fin in towing attitude and towing stability. The second scale model test confirmed the characteristics of the vertical tail fin height increase and the lower horizontal tail fin inclination angle application shape based on the Y-type tail fin. The shape of the application of the lower horizontal tail fin inclination angle showed the best performance. In order to verify the results of the scale model test, a full size model was constructed, sea trials were performed, and the towing attitude was measured. The results were similar to those of the scale model test.

• Journal of the Korea Convergence Society
• /
• v.11 no.3
• /
• pp.195-200
• /
• 2020

In this study, the flow analyses were performed on the fluid clutch turbine blade shapes of models 1, 2 and 3, with eight turbine blades tilted at 45 °, 40 °, and 35 ° angles on the propulsion shaft, respectively. The larger the angle of inclination on the propulsion shaft, the higher the flow pressure among the flow models after the back of the turbine blades. On the other hand, the smaller the angle of inclination on the propulsion shaft of the turbine wing, the lower the flow rate. It can be seen that the smaller inclination angle of the turbine blade surface on the propulsion shaft, i.e., the wing shape close to perpendicular to the flow of fluid, is more suitable for efficiently connecting and disconnecting the fluid clutch. By applying the flow analysis by type of turbine blade of fluid clutch,the study result at this paper is considered to be favorable as the convergent research material which can apply the aesthetic design.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.38 no.8
• /
• pp.747-757
• /
• 2010

The ice accreted on the airfoil is one of the critical drivers that causes the degradation of aerodynamic performance as well as aircraft accidents. Hence, an efficient numerical code to predict the accreted ice shape is crucial for the successful design of de-icing and anti-icing devices. To this end, a numerical code has been developed for the prediction of glaze ice accretion shape on 2D airfoil. Constant Source-Doublet method is used for the purpose of computational efficiency and heat transfer in the icing process is accounted for by Messinger model. The computational results are thoroughly compared against available experiments and other computation codes such as LEWICE and TRAJICE. The direction and thickness of ice horn are shown to yield similar results compared to the experiments and other codes. In addition, the effects of various parameters - temperature, free-stream velocity, liquid water contents, and droplet diameter - on the ice shape are systematically analyzed through parametric studies.

• The Journal of the Acoustical Society of Korea
• /
• v.43 no.1
• /
• pp.103-111
• /
• 2024

Axial-flow fans are used to transport fluids in relatively low-pressure flow regimes, and a variety of design variables are employed. The tip geometry of an axial fan plays a dominant role in its flow and noise performance, and two of the most prominent flow phenomena are the tip vortex and the tip leakage vortex that occur at the tip of the blade. Various studies have been conducted to control these three-dimensional flow structures, and winglet geometries have been developed in the aircraft field to suppress wingtip vortices and increase efficiency. In this study, a numerical and experimental study was conducted to analyze the effect of winglet geometry applied to an axial fan blade for an air conditioner outdoor unit. The unsteady Reynolds-Averaged Navier-Stokes (RANS) equation and the FfocwsWilliams and Hawkings (FW-H) equation were numerically solved based on computational fluid dynamics techniques to analyze the three-dimensional flow structure and flow noise numerically, and the validity of the numerical method was verified by comparison with experimental results. The differences in the formation of tip vortex and tip leakage vortex depending on the winglet geometry were compared through a three-dimensional flow field, and the resulting aerodynamic performance was quantitatively compared. In addition, the effect of winglet geometry on flow noise was evaluated by numerically simulating noise based on the predicted flow field. A prototype of the target fan model was built, and flow and noise experiments were conducted to evaluate the actual performance quantitatively.