• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.35 no.9
• /
• pp.753-760
• /
• 2007

In a 3-D flapping motion, the spanwise flow is generated while the wing is moved on the stroke plane. And at the end of each stroke, the rotational circulation is generated due to a wing rotation. In this study, to evaluate the effect of spanwise flow and wing rotation on the aerodynamic characteristics in 3-D flap 753ping motion, a 3-D flapping motion was compared with a 2-D translating motion. In each flapping motion, the aerodynamic forces were measured with respect to the angles of attack and Reynolds number. The aerodynamic forces generated by 2-D translating motion were higher than those generated by 3-D flapping motion. While the lift of 3-D flapping motion was increased until the angle of attack $60^{\circ}$ at mid-stroke, the lift generated by 2-D translating motion was decreased above the angle of attack 40° at mid stroke. Also, at the end of each stroke, the aerodynamic forces were increased rapidly due to wing rotation.

• 한국항공운항학회:학술대회논문집
• /
• 2016.05a
• /
• pp.19-22
• /
• 2016

본 연구는 박각시 나방 유연날개의 준정상 공력 모델링을 위한 공력측정실험을 진행하였다. 두 개의 서보모터로 이루어진 동역학적 로봇 모델은 3톤 수조 내부에서 날갯짓 운동을 구현하였고, 6축 센서가 날개 모델의 뿌리에 장착되어 공력 측정을 시행하였다. 날개 모델은 다른 두께의 폴리카보네이트 평판으로 제작되었고, 3mm 두께의 강체날개와 0.8mm 두께의 유연날개로 구성되었다. 공력측정은 각 날개 모델별 받음각을 -5도에서 95도까지 5도씩 변경하여 진행하였고, 이를 바탕으로 준정상 공력 모델링을 시도하였다. 날개 두께별 준정상 공력 모델링을 통해 특정 두께를 가진 유연날개는 강체날개보다 높은 공력효율을 가짐을 알 수 있었고, 날개 유연도 역시 준정상 가정을 기반으로 모델링 할 수 있을 것으로 기대된다.

• 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 Korean Society for Aeronautical & Space Sciences
• /
• v.45 no.10
• /
• pp.817-824
• /
• 2017

This paper presents the characteristics of wing-tail interference for a tail-controlled missile. The magnitude of wing-tail interference was calculated with wind tunnel test results and its effects on aerodynamic coefficients were investigated. The downwash angle of tail wing was calculated with experimental data and the effect of wing-tail interference was expressed as a ratio of angle of attack. Numerical simulations were made to examine flow characteristics of wing-tail interference and the vorticity contour of missile were compared with respect to angle of attack. Experimental and numerical analysis results show that the wing-tail interference has significant effects on static stability of tail-controlled missile.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.34 no.3
• /
• pp.14-21
• /
• 2006

The unsteady vortex lattice method is used to model twisting and flapping motions of a rectangular flat plate wing. The results for plunging and pitching motions were compared with the limited experimental results available and other numerical methods. They show that the method is capable of simulating many of the features of complex flapping flight. The lift, thrust and propulsive efficiency of a rectangular flat plate wing have been calculated for various twisting angles and reduced frequency with an amplitude of flapping angle($20^{\circ}$). And the effects of the twisting on the aerodynamic characteristics of the flapping wing are discussed by examination of their trends.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.43 no.6
• /
• pp.533-539
• /
• 2015

Recently, guided missiles applies folding wings to save space. During wing deployment, aero force acting on wing effects significantly on deployment performance, usually aerodynamic coefficient are calculated by CFD analysis. However, Missile Datcom can calculates estimated aerodynamic coefficient very quickly by assuming wing deployment motions as dihedral angle of wing. If missile has external store, wings may need to be folded on top of each other. In this case, one of wing help or interrupt other wing deployment, locking effect. In this study, both effects were included on wing deployment performance analysis to criteria for wings locked condition and formulated wing deploy performance, and compared with wind tunnel test data. Analysis predicted vulnerable wind direction of wing deployment very well.

• The Korean Journal of Zoology
• /
• v.26 no.1
• /
• pp.29-40
• /
• 1983

The differences in the electron microscopic fine structures of the wing imaginal discs of the vestigial (vg), wing mutant and wild type of Drosophila melanogaster were investigated. The materials used in this study were collected at ten hours intervals from the late third instar larvae of the both stocks. The fine structural changes during differentiation were as follows: 1. In wild type lipid droplets were coalesced and converted to glycogen, while no changes were observed in the mutatn vestigial. 2. Degeneration of the cells by phagocytosis were observed not only from the mutatn vestigial, but from the wild type. However, degenerative feature of the wild type was poor. 3. Dented structures of tracheole showed little differences between wild type and the mutant vestigial. But the tracheole diameter of the wild type became wider in the course of differentiation, while the mutant vestigial narrow. Although mutant vestigial develops normally during early embryogenesis, the late third instar larvae shows defficiency in gluconeogenesis, converting fatty acid to glycogen. This, together with the predominant cell degeneration by phagocytosis and poorly developed tracheole, seems to effect on the expression of the vestigial phenotype.

• Journal of the Society of Naval Architects of Korea
• /
• v.32 no.4
• /
• pp.55-63
• /
• 1995

This paper describes the procedure to analyze the performance of the end-plated propeller(EPP) by a boundary integral method. The screw blade(SB) and end-plate(EP) are represented by a set of quadrilateral panels, where the source and normal dipole of uniform strength are distributed. The perturbation velocity potential, being the only unknown via the potential-based formulation, is determined by satisfying the flow tangency condition on the blade and the end-plate at the same time. The Kutta condition is satisfied through an iterative process by requiring the null pressure jump across the upper and lower sides of the trailing edges of both the SH and the EP. Sample calculations indicate that the EP increases the loading near the tip of the SB while spreading the trailing vortices along the trailing edge of the EP, thus avoiding the strong tip-vortex formation. Predicted performance of the EPP shows good correlations with the experimental results. The method is therefore considered applicable in designing and analyzing the EPP which may be an alternative for energy-saving propulsive devices.

• Korean journal of applied entomology
• /
• v.55 no.4
• /
• pp.517-521
• /
• 2016

Three species of micromoths, Acria emarginella Donovan, 1806 (Peleopodidae), Yponomeuta cinefactus Meyrick, 1935 (Yponomeutidae) and Depressaria leucocephala Snellen, 1884 (Depressariidae) are reported for the first time from Korea. These species were collected at their larval stage on the host plants, and reared until their emergence. Images of larvae, pupae, and adults of all species are given, and the male or female genitalia are illustrated.

• Korean journal of applied entomology
• /
• v.57 no.1
• /
• pp.1-5
• /
• 2018

Tachinus (Tachinus) javanus Cameron is identified for the first time in the Korean Peninsula. Description, illustrations of habitus and diagnostic characters, and a key to the known species of Korean Tachinus Gravenhorst are provided. Tachinus (Tachinus) yezoensis Li is redescribed with male characteristics.