• 융복합기술연구소 논문집
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• 제4권1호
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• pp.37-41
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• 2014

For the analysis of lifting surface at high angle of attack, a Nonlinear Vortex Lattice Method(NLVLM) was used. The NLVLM is intented to compute the interactions between lifting surfaces and separated vertical flow. The lifting surfaces are represented by a lattice of discrete vortex rings. And wakes are represented by families of non-lintersecting, semi-infinite vortex line segments. The image method also used to analyze the ground effect. It is found that vortex lines separated from lifting surfaces represent the separated flows successfully. Although the present method is applied for the rectangular wing and delta wing, extensions can be possible for the arbitrary lifting surfaces. The Present results show good agreement with experimental data.

• 한국안전학회지
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• 제22권1호
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• pp.24-29
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• 2007

The effectiveness of a UV(ultra violet) disinfection system depends on the characteristics of the waste water, flow conditions, the intensity of UV radiation, the amount of time the microorganisms are exposed to the radiation, and the reactor configuration. The wast water flow conditions are important factors in the design of UV disinfection system from the point of enhancement view of UV disinfection. The turbulent energy intensity in the wake by the vortex shedding are effective for UV radiation. Therewith the effectiveness of vortex generator is considered as a enhancement of UV disinfection. The experimental results presented give important evidences and explain that it is possible to predict UV disinfection performance based on flow experiments. An experimental investigation of two types of the vortex generator is presented. The qualitative and quantitative evaluations of the wake are made by flow visualization using smoke wire method and the measurement of vortex frequencies in the wind tunnel. From the experiment, following results were obtained that the delta wing type vortex generator is more effective than circular type because of the higher vortex frequencies and the smaller drag.

• International Journal of Naval Architecture and Ocean Engineering
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• 제4권4호
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• pp.477-487
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• 2012

We investigated the aerodynamic characteristics of a three-dimensional (3D) wing with an endplate in the vicinity of the free surface by solving incompressible Navier-Stokes equations with the turbulence closure model. The endplate causes a blockage effect on the flow, and an additional viscous effect especially near the endplate. These combined effects of the endplate significantly reduce the magnitudes of the velocities under the lower surface of the wing, thereby enhancing aerodynamic performance in terms of the force coefficients. The maximum lift-to-drag ratio of a wing with an endplate is increased 46% compared to that of wing without an endplate at the lowest clearance. The tip vortex of a wing-with-endplate (WWE) moved laterally to a greater extent than that of a wing-without-endplate (WOE). This causes a decrease in the induced drag, resulting in a reduction in the total drag.

• International Journal of Aeronautical and Space Sciences
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• 제18권3호
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• pp.474-484
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• 2017

This paper studies the applicability of an efficient numerical model based on artificial neural networks (ANNs) to predict the dynamic responses of the wing structure of an airplane due to atmospheric turbulence in the time domain. The turbulence velocity is given in the form of a stationary Gaussian random process with the von Karman power spectral density. The wing structure is modeled by a classical beam considering bending and torsional deformations. An unsteady vortex-lattice method is applied to estimate the aerodynamic pressure distribution on the wing surface. Initially, the trim condition is obtained, then structural dynamic responses are computed. The numerical solution of the wing structure's responses to a random turbulence profile is used as a training data for the ANN. The current ANN is a three-layer network with the output fed back to the input layer through delays. The results from this study have validated the proposed low-cost ANN model for the predictions of dynamic responses of wing structures due to atmospheric turbulence. The accuracy of the predicted results by the ANN was discussed. The paper indicated that predictions for the bending moments are more accurate than those for the torsional moments of the wing structure.

• 대한조선학회논문집
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• 제31권1호
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• pp.84-93
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• 1994

본 연구에서는 NACA0012단면을 갖는 타원형날개끝 캐비테이션과 유기소음특성에 미치는 표면거칠기의 영향이 실험적으로 조사되었다. 사용한 표면거칠기는 조도 $200{\mu}m$의 입자로서, 날개끝 3cm 구간에 부착하였다. 또한 날개끝과 앞날에 각각 3cm의 거칠기를 준 경우도 별도로 조사되었다. 캐비테이션 발생시험 결과 캐비테이션 초기발생위치는 실험한 받음각 범위에서 날개끝으로부터 대략 1/2 코오드정도 후류이며, 캐비테이션 수가 감소함에 따라 변화하는 형상을 보였다. 날개끝 캐비테이션에 의한 소음은 주파수 3-50kHs사이의 비교적 고주파수에서 음압이 증가하는 양상을 보였으나, 더 낮은 캐비테이션수에서 날개 앞날 캐비테이션으로 확장되면 전 주파수 범위에 걸쳐서 소음이 증가하었다. 캐비테이션과 소음발생은 표면거칠기가 증가할때 개선되는 경향을 보였으나 그 차이는 크지않았다. 날개 앞날과 끝날에 거칠기를 준 경우가 낮은 캐비테이션수에서 다소 유리한 캐비테이션 특성을 보여준 반면 양력-항력비의 감소에 따른 문제점도 지적되었다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.1672-1677
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• 2004

Leading edge extension(LEX) in a highly swept shape applied to a delta wing features the modem air-fighters. The LEX vortices generated upon the upper surface of the wing at high angle of attack enhance the lift force of the delta wing by way of increased negative suction pressure over the surfaces. The present 3-D stereo PIV includes the Identification of 2-D cross-correlation equation, stereo matching of 2-D velocity vectors of two cameras, accurate calculation of 3-D velocity vectors by homogeneous coordinate system, removal of error vectors by a statistical method followed by a continuity equation criterion and so on. A delta wing model with or without LEX was immersed in a circulating water channel. Two high-resolution, high-speed digital cameras($1280pixel{\times}1024pixel$) were used to allow the time-resolved animation work. The present dynamic stereo PIV represents the complicated vortex behavior, especially, in terms of time-dependent characteristics of the vortices at given measuring sections. Quantities such as three velocity vector components, vorticity and other flow information can be easily visualized via the 3D time-resolved post-processing to make the easy understanding of the LEX effect or vortex emerging and collapse which are important phenomena occurring in the field of delta wing aerodynamics.

• 항공우주시스템공학회지
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• 제13권5호
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• pp.32-38
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• 2019

높은 후퇴각을 갖는 둥근 앞전 날개 형상은 앞전 와류에 의해 복잡한 유동 현상이 나타난다. 불안정한 방향 안정성을 갖는 무미익 플라잉윙의 제어를 위해서 플래퍼론이 사용된다. 본 연구에서는 플래퍼론이 전개된 비세장형, 둥근 앞전의 플라잉윙 형상의 전산해석을 수행하였으며 옆미끄럼각 및 플래퍼론에 대한 영향을 분석하였다. 공력계수 분석을 통해 양력과 항력계수에 대한 옆미끄럼각의 영향은 적으며 측력 및 모멘트 계수는 옆미끄럼각의 영향을 크게 받음을 알 수 있었다. 정적 안정성 분석을 통해 플래퍼론이 전개된 플라잉윙의 가로안정성과 방향안정성이 좋아졌음을 확인하였다. 또한 압력계수분포, 표면 마찰선의 관찰을 통해 앞전 와류 구조 및 거동을 분석하였다.

• 한국항공우주학회지
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• 제34권3호
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• pp.14-21
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• 2006

직사각형 평판날개의 날개짓과 비틀림 운동을 해석하기 위하여 비정상 와류격자법(VLM)을 이용하였다. 단순 상하 및 피칭 운동하는 날개에 대한 해석결과를 실험 및 다른 수치해석 결과들과 비교하여 복잡한 날개짓 비행을 모사하는데 본 방법을 사용할 수 있음을 보였다. 날개짓 각 진폭이 $20^{\circ}$인 경우에 여러 가지 비틀림 각과 무차원 주파수 변화에 대하여 직사각형 평판 날개의 양력, 추력 및 추진효율을 계산하였다. 계산 결과를 분석하여 주기적으로 변하는 비틀림이 날개짓 날개의 공력 특성에 미치는 영향을 살펴보았다.

• Journal of Advanced Marine Engineering and Technology
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• 제23권4호
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• pp.462-472
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• 1999

De-NOx facility using Selective Catalytic Reduction method is the most widely applied one that removes NOx from flue gas emitted from combustion facility such as boiler for power generation engine incinerator etc. Reductant $NH_3\;or\;NH_4OH$ is sprayed into flue gas to convert NOx into $H_2O$ and $N_2.$ Good mixing between flue gas and $NH_3$ is the most important factor to increase reduction in catalytic layer and to reduce unreacted NH3 slip. Therefore the development of mixer device for mixing effect is one of the important part for SCR facility. Objectives of this study are to investigate the relation between flow and concentration field by observation at the wake of delta-wing type mixer. At the first stage qualitative measurement of flow field is conducted by flow visualization using laser light sheet in lab. scale wind tunnel. Also we have conducted the quantitative analysis by comparing flow field measurement using LDV with numerical simulation. On the basis of qualitative and quantitative analysis we investigate the dis-tribution of flow and concentration in flow model facility. The results of an experimental and compu-tational examination of the vortex structures shed from delta wing type vortex generator having $40^{\circ}$ angle of attack are presented, The effects of vortex structure on the gas mixing is discussed, too.

• Journal of Mechanical Science and Technology
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• 제18권12호
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• pp.2273-2283
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• 2004

The vortical flows over sharp-edged delta wings with and without a leading edge extension have been investigated using a computational method. Three-dimensional compressible Reynolds-averaged Navier-Stokes equations are solved to provide an understanding of the effects of the angle of attack and the angle of yaw on the development and interaction of vortices and the aerodynamic characteristics of the delta wing at a freestream velocity of 20 m/s. The present computations provide qualitatively reasonable predictions of vortical flow characteristics, compared with past wind tunnel measurements. In the presence of a leading edge extension, a significant change in the suction pressure peak in the chordwise direction is much reduced at a given angle of attack. The leading edge extension can also stabilize the wing vortex on the windward side at angles of yaw, which dominates the vortical flows over yawed delta wings.