• 한국항행학회논문지
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• 제13권6호
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• pp.820-830
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• 2009

본 논문은 활주로 주변 건물로 인하여 발생되는 ground turbulence를 효과적으로 감소시키는 연구의 일환이다. 이러한 ground turbulence는 sport plane이나 중소형 무인항공기의 이착륙 안정성에 큰 영향을 미치고 있으며, 이러한 ground turbulence의 발생 원인을 2차원 전산수치해석을 통하여 연구하였다. 연구결과 활주로의 건물단면 형상이 건물의 높이보다 ground turbulence를 발생시키는 주요 원인임을 알 수 있었으며, 이러한 ground turbulence를 효과적으로 감소하기 위해서는 바람방향의 건물 앞쪽에 fence나 계단형상 및 gap등의 시설물을 설치하여 초기에 난류를 발생시킨다면, 측풍의 풍속이 변하더라도 상대적으로 활주로에 큰 영향이 미치지 않게 제어할 수 있음을 알 수 있었다.

• 한국항공운항학회지
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• 제17권4호
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• pp.32-41
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• 2009

This paper presents the work being carried out in order to reduce the ground turbulence by the fence in the vicinity of airport runway. In preliminary study, we knows that cross-wind effect in the vicinity of runway is highly dependent on the shape of the buildings and have predicted results confirmed reduction of wind-effect by doing that set up the building with a fence, terraced shape or gap. This study is to figure out effect of ground turbulence by the building with fence, which is changing fence height, in using two-dimensional computational fluid dynamics analysis.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2006년도 PARALLEL CFD 2006
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• pp.49-50
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• 2006

• Current Optics and Photonics
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• 제8권1호
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• pp.38-44
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• 2024

Under the influence of atmospheric turbulence, a star's point image will shake back and forth erratically, and after exposure the originally small star point will spread into a huge spot, which will affect the ground calibration of the star sensor. To analyze the impact of atmospheric turbulence on the positioning accuracy of the star's center of mass, this paper simulates the atmospheric turbulence phase screen using a method based on a sparse spectrum. It is added to the static-star-simulation device to study the transmission characteristics of atmospheric turbulence in star-point simulation, and to analyze the changes in star points under different atmospheric refractive-index structural constants. The simulation results show that the structure function of the atmospheric turbulence phase screen simulated by the sparse spectral method has an average error of 6.8% compared to the theoretical value, while the classical Fourier-transform method can have an error of up to 23% at low frequencies. By including a simulation in which the phase screen would cause errors in the center-of-mass position of the star point, 100 consecutive images are selected and the average drift variance is obtained for each turbulence scenario; The stronger the turbulence, the larger the drift variance. This study can provide a basis for subsequent improvement of the ground-calibration accuracy of a star sensitizer, and for analyzing and evaluating the effect of atmospheric turbulence on the beam.

• 한국항공운항학회지
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• 제13권2호
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• pp.27-34
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• 2005

This study is performed to analyze the turbulence distribution of Fev. & Mar. in 2000 by the analysis of the parameters related with flight data of FDR(Flight Data Recorder). In the analysis, we selected the Solid State Flight Data Recorder(SSFDR) & Universal Flight Data Recorder(UFDR) flight data of the exact same aircraft(capacity 120 persons). Through this study, we verified that turbulence is concerned with configuration of the ground and flight situation of aircraft.

• 한국태양에너지학회 논문집
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• 제37권6호
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• pp.25-37
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• 2017

A study on factors influencing measurement error of Ground-based LiDAR(Light Detection And Ranging) system was conducted in Kimnyeong wind turbine test site on Jeju Island. Three properties of wind including inclined angle, turbulence intensity and power law exponent were taken into account as factors influencing the measurement error of Ground-based LiDAR. In order to calculate LiDAR measurements error, 2.5-month wind speed data collected from LiDAR (WindCube v2) were compared with concurrent data from the anemometer on a nearby 120m-high meteorological mast. In addition, data filtering was performed and its filtering criteria was based on the findings at previous researches. As a result, at 100m above ground level, absolute LiDAR error rate with absolute inclined angle showed 4.58~13.40% and 0.77 of the coefficients of determination, $R^2$. That with turbulence intensity showed 3.58~23.94% and 0.93 of $R^2$ while that with power law exponent showed 4.71~9.53% and 0.41 of $R^2$. Therefore, it was confirmed that the LiDAR measurement error was highly affected by inclined angle and turbulence intensity, while that did not much depend on power law exponent.

• 한국자동차공학회논문집
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• 제11권3호
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• pp.115-123
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• 2003

With the advent of high performance computers and more efficient numerical algorithms, computational fluid dynamics(CFD) has come out as a modem alternative for reducing the use of wind tunnels test in automotive engineering. However, in spite of the fact that many competent researchers have made all their talents in developing turbulence model over since the past dozen or more years, it has been an important impediment in using the CFD effectively to design machinery and to diagnose or to improve engineering problems in the industry since the turbulence model has been acting as the Achilles' tendon in aspect of the reliability even to this time. In this study, Reynolds-averaged Wavier-Stokes equations were solved to simulate an incompressible turbulent flow around a bus-like bluff body near ground plane. In order to investigate the effect of the discretisation schemes and turbulence model on the aerodynamic forces several turbulence models with five convective difference schemes are adopted. From the results of this study, it is clear that choice of turbulence model and discretisation scheme profoundly affects the computational outcome. The results also show that the adoption of RNG $k-\varepsilon$ turbulence model and nonlinear quadratic turbulence model with the second order accurate discretisation scheme predicts fairly well the aerodynamic coefficients.

• 한국대기환경학회지
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• 제15권5호
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• pp.613-623
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• 1999

A Lagrangian particle dispersion mode l(LPDM) coupled with the prognostic flow model based on nonequilibrium level 2.5 turbulence closure has been dcveloped to simulate the dispersion from an elevated emission source. The proposed model did not require any empirical formula or data for the turbulent statistics such as velocity variances and Lagrangian time scales since the turbulence properties for LPDM were calculated from results of the flow model. The LPDM was validated by comparing the model results against the wind tunnel tracer experiment and ISCST3 model. The calculated wind profile and turbulent velocity variances were in good agreement with those measured in the wind tunnel. The ground level concentrations along the plume centerline as well as the dispersion codfficients also showed good agreement in comparison with the wind tunnel tracer experiment. There were some discrepancies on the horizontal spread of the plume in comparison with the ISCST3 but the maximum ground level concentrations were in a good confidence range. The results of comparisons suggested that the proposed LPDM with the flow model was an effective tool to simulate the dispersion in the flow situation where the turbulent characteristics were not available in advance.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2000년도 춘계 학술대회논문집
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• pp.84-90
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• 2000

Ground effect of three-dimensional wing is studied. LU-factored Implicit upwind TVD scheme and Baldwin-Lomax turbulence model are used for this calculation. To investigate ground effect, NACA 4415 wing at M=0.5 calculated. Two different angles of attack and three cases of flight height are calculated. As increasing angle of attack, the ground effect becomes strong. In case of NACA 4415 wing in ground effect, strength of wing tip vortex becomes stronger than that of free flight.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2011년도 제37회 추계학술대회논문집
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• pp.321-324
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• 2011

지상연소시험용 소형 액체로켓엔진 초음속 노즐의 성능해석을 위하여 노즐내 유동특성 및 플룸 구조를 $k-{\omega}$ SST모델을 사용한 Reynolds-averaged Navier-Stokes 방정식으로 해석하였다. 해석기법의 검증을 위하여 2차원 축소-확대 노즐 초음속 유동의 해석값과 실험치를 비교하고, 검증된 기법으로 2차원 축대칭 노즐의 성능해석을 수행하였다. 그 결과 노즐 내부에 유동박리 및 역류현상의 발생이 확인되었으며, 이 해석결과는 소형 액체로켓엔진 노즐 최적설계에의 기초자료로 제시되었다.