• 항공우주시스템공학회지
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• 제15권5호
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• pp.60-71
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• 2021

상용 프로펠러의 추력과 토크를 측정하기 위한 성능시험 장치를 고안하였으며, 30인치급 3가지 프로펠러에 대한 성능시험을 수행하였다. 프로펠러 추력과 토크 측정을 위해 모터, 프로펠러와 연결된 6분력 발란스를 적용하였으며, 풍동 저울 교정 장비를 이용하여 측정 시스템의 확인을 수행하였으며, QTP 프로펠러를 적용하여 구축한 성능시험 장치의 검증 시험도 수행하였다. 제자리 비행 조건에서 상용 프로펠러의 제작사에서 제공하는 사양과 시험 결과를 비교하였으며, 추력 및 토크에서 차이가 있음을 확인하였다. 받음각, 프로펠러 형상, 풍속을 변경시켜가며 프로펠러 성능을 측정하였으며, 각 프로펠러에 대해 RPM에 따른 프로펠러 추력 계수로 나타내었다. 저 받음각과 고 받음각에서 경향이 다르게 나타남을 확인하였으며, 차후 공중용 무인이동체 공력 설계에 활용 가능한 공력 데이터베이스를 확보하였다.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 1996년도 춘계 학술대회논문집
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• pp.74-84
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• 1996

Characteristic boundary conditions are discussed in conjunction with a flux-difference splitting formulation as modified from Roe's linearization. Details of how one can implement the characteristic boundary conditions which are compatible with the discrete formulation at interior points are given for different types of boundaries including subsonic outflow and adiabatic wall. The latter conditions are demonstrated through computation of supersonic ogive-cylinder flow at high angle of attack and the computed wall pressure distribution is compared with experiment.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2006년 제4회 한국유체공학학술대회 논문집
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• pp.387-390
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• 2006

Numerical study has been conducted in two dimensions about a NACA0012 airfoil with an oscillating microflap on the surface. We show that this microflap is effective in controlling the unsteady stall at high angles of attack. We solve the compressible Navier-Stokes equations for the Reynolds numbers with an extensible chimera grid fitted to the oscillatory microflap. For turbulent calculation, we adopt the SST $k-{\omega}$ model. We investigate the parametric effect of angle of attacks, Reynolds number, and the location where the microflap is installed.

• International Journal of Aeronautical and Space Sciences
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• 제9권1호
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• pp.111-120
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• 2008

A particle image velocimetry (PIV) technique was employed to investigate the effects of blowing jet on the flow characteristics over stationary and pitch-oscillating airfoils. The Reynolds number was $7.84{\times}10^5$ based on the chord length. It was found that for stationary airfoil cases, continuous and pulsating blowing jets successfully reduced separated wake region at high angles of attack. A comparison study of two different types of jet blowing indicated that pulsating jet is more effective than continuous jet for flow separation control. Pulsating leading-edge blowing postpones flow separation and increased stall angle of attack by $2^{\circ}{\sim}3^{\circ}$. For pitch-oscillating airfoil cases, the PIV results showed that blowing jet efficiently delays the separation onset point during pitch-up stroke, whereas it does not prevent flow separation during pitch-down stroke, even at angles of attack smaller than static ones.

• Advances in aircraft and spacecraft science
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• 제2권3호
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• pp.329-343
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• 2015

This study aimed to observe the effect of a novel concept (referred to as the flap extension) implemented on the leading edge of the flap of a three element high lift device. The high lift device, consisting of a flap, main element and slat is designed around an Airbus research profile for sufficient take off and landing performance of a large commercial aircraft. The concept is realised on the profile and numerically optimised to achieve an optimum geometry. Two different optimisation approaches based on Genetic Algorithm optimisations are used: a zero order approach which makes simplifying assumptions to achieve an optimised solution: as well as a direct approach which employs an optimisation in ANSYS DesignXplorer using RANS calculations. Both methods converge to different optimised solutions due to simplifying assumptions. The solution to the zero order optimisation showed a decreased stall angle and decreased maximum lift coefficient against angle of attack due to early stall onset at the flap. The DesignXplorer optimised solution matched that of the baseline solution very closely. The concept was seen to increase lift locally at the flap for both optimisation methods.

• 수산해양기술연구
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• 제40권3호
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• pp.206-213
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• 2004

종횡비, 다각형 모양에 따른 평판과 범포의 유체역학적 특성을 규명하고자 직사각형, 사다리꼴 모양으로 모형 평판과 범포를 제작하고 회류수조에서 양 ${\cdot}$ 항력 실험을 수행하였다. 그 결과를 요약하면 다음과 같다. 1. 삼각형 평판의 경우, 종횡비가 1 이하인 모형에서는 38${\sim}$42$^{\circ}$에서 최대 $C_L$이 1.23${\sim}$1.32, 1.5 이상인 모형에서는 20${\sim}$50$^{\circ}$에서 $C_L$이 약 0.85 전후였다. 역삼각형 평판의 경우, 종횡비가 1 이하인 모형에서는 영가가 36${\sim}$38$^{\circ}$에서 최대 $C_L$이 1.46${\sim}$1.56, 1.5 이상인 모형에서는 22${\sim}$26$^{\circ}$에서 1.05${\sim}$1.21 정도였다. 같은 삼각형 평판 모형에서는 전자의 모형이 후자보다 $C_L$이 작게, 양항비도 작게 나타났다. 2. 삼각형 범포의 경우, 종횡비가 1 이하인 모형에서는 영각 46${\sim}$48$^{\circ}$에서 최대 $C_L$이 1.67${\sim}$1.77, 1.5 이상인 모형에서는 20${\sim}$50$^{\circ}$에서 $C_L$이 약 1.1 전후였다. 역삼각형 범포의 경우, 종횡비가 1 이하인 모형에서는 영각 28${\sim}$32$^{\circ}$에서 최대 $C_L$이 1.44${\sim}$1.68, 1.5 이상인 모형에서는 18${\sim}$24$^{\circ}$에서 10.3${\sim}$1.18 정도였다. 같은 삼각형 범포 모형에서는 전자의 모형이 후자보다 $C_L$은 크게, 양항비는 작게 나타났다. 3. 모형에서 물의 유체력을 많이 받을 수 있는 곳에서 만곡꼭지점이 만들어지며, 삼각형 모형에서는 종횡비가 클수록, 역삼각형 모형에서는 작을수록 만곡꼭지점의 위치도 컸다. 4. 만곡도는 전 모형에서 종횡비가 클수록 컸으며, 삼각형 모형에서는 영각이 클수록 컸고 역삼각형 모형에서는 작을수록 컸다.

• 한국가시화정보학회지
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• 제19권3호
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• pp.106-114
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• 2021

In the present study, we investigate the flow characteristics of a paraglider canopy with leading-edge tubercles by performing force measurement and surface flow visualizations. The experiment is conducted at Re = 3.3×10⁵ in a wind tunnel, where Re is the Reynolds number based on the mean chord length and the free-stream velocity. The canopy model with leading-edge tubercles has flow characteristics of a two-step stall, showing an earlier onset of the first stall than the canopy model without leading-edge tubercles. However, the main stall angle of the tubercled model is much larger than that of the canopy model without tubercles, resulting in a higher aerodynamic performance at high angles of attack. The delay in the main stall is ascribed to the suppression of separation bubble collapse around the wingtip at high angles of attack.

• 한국자동차공학회논문집
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• 제6권2호
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• pp.12-20
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• 1998

Exter ballistics of a typical high-speed projectile is studied through a flow-visualization experiment and an unstructured grid Navier-Srokes computation. Experiment produced a schlieren photograph that adequately shows the characteristic features of this complex flow, namely two kinds of oblique cone shocks and turbulent wake developing into the downstream. A hybrid scheme of finite volume-element method is used to simulate the compressible Reynolds-Averaged Navier-Stok- es solution on unstructured grids. Osher's approximate Riemann solver is used to discretize the cinvection term. Higher-order spatial accuracy is obtained by MUSCL extension and van Albada ty- pe flux limiter is used to stabilize the numerical oscillation near the solution discontinuity. Accurate Gakerkin method is used to discretize the viscous term. Explict fourth-order Runge-Kutta method is used for the time-stepping, which simplifies the application of MUSCL extension. A two-layer k-$\varepsilon$ turbulence model is used to simulate the turbulent wakes accurately. Axisymmetric folw and two-dimensional flow with an angle of attack have been computed. Grid-dependency is also checked by carrying out the computation with doubled meshes. 2-D calculation shows that effect of angle of attack on the flow field is negligible. Axi-symmetric results of the computation agrees well with the flow visualization. Primary oblique shock is represented within 2-3 meshes in numerical results, and the varicose mode of the vortex shedding is clearly captured in the turbulent wake region.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 추계학술대회논문집B
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• pp.615-620
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• 2000

Manoeuvrability of ships has been receiving a great deal of attention both concerning navigation safety and the prediction of ship manoeuvring characteristics, especially at the preliminary design stage. Recently, in order to improve manoeuvrability of ships, High-lift devices could be applied to design of rudder at design stage. Now, among the them, we carried out the flow visualization and investigation of flow field around a flapped rudder(trailing-edge flap). A trailing-edge flap is simply a portion of the trailing-edge section of airfoil that is hinged and which can be deflected upward or downward. Flow visualization results of flap defection shown as follow Photos including main body and flap defection.

• 한국항공우주학회지
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• 제33권7호
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• pp.85-91
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• 2005

군용항공기는 고받음각에서 적절한 조종성 및 항공기 이탈에 대한 안정성을 확보하고 있어야 한다. 고받음각에서 항공기가 이탈에 진입할 수 있는 한계값은 항공기 형상설계에 직결되는 문제이다. 하지만 현대의 고성능 전투기는 전기식 비행제어계통을 사용하여 고받음각 제어법칙을 설계함으로써 한계 값 내에서 항공기의 안정성을 보장하고 있으며 항공기가 이탈 시, 안전하게 회복할 수 있도록 고받음각 제어법칙을 설계한다. 현재 T-50에 적용되어 있는 고받음각 제어법칙은, 세로축 방향으로는 받음각 제한기 및 MPO(Manual Pitch Override) 모드, 가로-방향축으로는 고받음각 이탈제한기, 가로축 명령제한기, 방향축 조종사 명령제한기 및 스핀방지기가 설계되어 있다. 본 논문에서는 T-50 에 적용되어 있는 고받음각 제어법칙을 소개하며, 고받음각 비행시험을 통하여 항공기 안정성에 관한 연구를 수행하였다.