• 한국군사과학기술학회지
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• 제17권1호
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• pp.149-157
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• 2014

In this paper, we investigated the sensitivity of aerostatic force coefficients of multi-layer radom in the various wind speeds. The test was conducted in KOCED Wind Tunnel Center in Chonbuk National University, and wind speeds were in the range from 5 m/s to 26 m/s in order to determine the Reynolds number independence. The test results of present multi-layer radom were not affected by the Reynolds number, The maximum positive pressure coefficient was found to be 1.08 at the center of the front of the plane in angle of attack of 0 degree, the maximum negative pressure coefficient was -2.03 at the upper right corner in angle of attack of 120 degree, while maximum drag coefficient was 1.11 in angle of attack of 180 degree.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2006년 제4회 한국유체공학학술대회 논문집
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• pp.101-104
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• 2006

This study aims at verifying characteristics of torsional fluctuating moment coefficient and power spectral density, which is needed to estimate torsional response of tall buildings. In order to estimate characteristics, the wind tunnel tests have been conducted on 52 types aero-elastic model of the rectangular prisms with various aspects ratios, side ratios and surface roughness in turbulent boundary layer flows. In this paper, characteristics of torsional fluctuating wind force are briefly discussed and then these results were mainly analyzed as a function of the aspects ratios and side ratios of buildings.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2011년도 춘계학술대회 논문집
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• pp.105-110
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• 2011

Catwalk structures are temporary walk ways for erection of main cables in suspension bridge. The aerodynamic characteristics of the catwalk structures are not well studied even though the catwalk structures are sensitive to wind action because of its flexibility. Present study demonstrates technical results obtained from wind tunnel tests of various catwalk structures. To obtain the aerostatic force coefficients of the floor system of catwalk, 1/14 and 1/4 scaled partial rigid models were fabricated and tested at the wind tunnel. In order to investigate the Reynolds number effects, the aerostatic force coefficients were measured at various wind velocities ranged from 5m/s to 30m/s. The test results revealed that the Reynolds number effects on aerostatic coefficients were not significant for the catwalk floor systems. An empirical equation for aerostatic force coefficients of catwalk are proposed based on the measured results.

• Wind and Structures
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• 제31권3호
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• pp.209-216
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• 2020

Aiming at the wind-resistant design of a sea-crossing arch bridge, the static aerodynamic coefficients of its girder (composed of stretches of π-shaped cross-section and box cross-section) were studied by using computational fluid dynamics (CFD) numerical simulation and wind tunnel test. Based on the comparison between numerical simulation, wind tunnel test and specification recommendation, a combined calculation method for the horizontal force coefficient of intermediate and small span bridges is proposed. The results show that the two-dimensional CFD numerical simulations of the individual cross sections are sufficient to meet the accuracy requirements of engineering practice.

• 대한공업교육학회지
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• 제32권1호
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• pp.117-133
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• 2007

이 연구는 중등학교 학생들에게 비행의 원리를 이해하고 항공 기술 분야에 흥미를 가질 수 있도록 하기 위해 학교 현장에 적용 가능한 교수-학습 자료인 학습용 풍동의 힘 측정 장치를 개발하였다. 연구의 내용은 학습용 풍동의 힘 측정 장치 개발과 실험으로 이루어져 있다. 이 연구에서 얻은 주요 결과를 정리하면 다음과 같다. 공과대학 기계계열 학과나 항공연구소 등에서 사용하는 고가의 Load cell을 이용한 장치 대신에 지렛대 원리를 활용한 간단한 구조이다. 종합된 하나의 장치로 양력, 항력 및 유체 저항 비교 실험이 가능하다. 에어포일 받음각에 따른 양력 계수는 실험값과 이론값이 전체적으로 비슷한 경향성을 갖으며, 실속 현상은 실험값이 이론값보다 더 큰 받음각에서 나타났다. 에어포일 받음각에 따른 항력 계수는 실험값과 이론값이 전체적으로 비슷한 경향성을 갖으며, 실험값은 이론값에 비해 항력 계수의 증가 비율이 완만하게 증가하였다.

• Wind and Structures
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• 제30권4호
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• pp.433-450
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• 2020

The strong turbulence characteristic of typhoon not only will significantly change flow field characteristics surrounding the large-scale wind turbine and aerodynamic force distribution on surface, but also may cause morphological evolution of coast dune and thereby form sand storms. A 5MW horizontal-axis wind turbine in a wind power plant of southeastern coastal areas in China was chosen to investigate the distribution law of additional loads caused by wind-sand coupling movement of coast dune at landing of strong typhoons. Firstly, a mesoscale Weather Research and Forecasting (WRF) mode was introduced in for high spatial resolution simulation of typhoon "Megi". Wind speed profile on the boundary layer of typhoon was gained through fitting based on nonlinear least squares and then it was integrated into the user-defined function (UDF) as an entry condition of small-scaled CFD numerical simulation. On this basis, a synchronous iterative modeling of wind field and sand particle combination was carried out by using a continuous phase and discrete phase. Influencing laws of typhoon and normal wind on moving characteristics of sand particles, equivalent pressure distribution mode of structural surface and characteristics of lift resistance coefficient were compared. Results demonstrated that: Compared with normal wind, mesoscale typhoon intensifies the 3D aerodynamic distribution mode on structural surface of wind turbine significantly. Different from wind loads, sand loads mainly impact on 30° ranges at two sides of the lower windward region on the tower. The ratio between sand loads and wind load reaches 3.937% and the maximum sand pressure coefficient is 0.09. The coupling impact effect of strong typhoon and large sand particles is more significant, in which the resistance coefficient of tower is increased by 9.80% to the maximum extent. The maximum resistance coefficient in typhoon field is 13.79% higher than that in the normal wind field.

• Wind and Structures
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• 제20권3호
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• pp.449-468
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• 2015

Current wind-resistance designs of large-scale indirect dry cooling towers (IDCTs) exclude an important factor: the influence of the ventilation rate for radiator shutter on wind loads on the outer surfaces of the tower shell. More seemingly overlooked aspects are the effects of various ventilation rates on the wind pressure distribution on the tower surfaces of two IDCTs, and the feature of the flow field around them. In order to investigate the effects of the radiator shutter ventilation rates on the aerodynamic interference between IDCTs, this paper established the numerical wind tunnel model based on the Computational Fluid Dynamic (CFD) technology, and analyzed the influences of various radiator shutter ventilation rates on the aerodynamic loads acting upon a single and two extra-large IDCTs during building, installation, and operation stages. Through the comparison with the results of physical wind tunnel test and different design codes, the results indicated that: the influence of the ventilation rate on the flow field and shape coefficients on the outer surface of a single IDCT is weak, and the curve of mean shape coefficients is close to the reference curve provided by the current design code. In a two-tower combination, the ventilation rate significantly affects the downwind surface of the front tower and the upwind surface of the back tower, and the larger positive pressure shifts down along the upwind surface of the back tower as the ventilation rate increases. The ventilation rate significantly influences the drag force coefficient of the back tower in a two-tower combination, the drag force coefficient increases with the ventilation rate and reaches the maximum in a building status of full ventilation, and the maximum drag coefficient is 11% greater than that with complete closure.

• Wind and Structures
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• 제26권2호
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• pp.99-114
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• 2018

Due to shortage of land and architectural aesthetics, sometimes the buildings are constructed as unconventional in plan. The wind force acts differently according to the plan shape of the building. So, it is of utter importance to study wind force or, more specifically wind pressure on an unconventional plan shaped tall building. To address this issue, this paper demonstrates a comprehensive study on mean pressure coefficient of 'E' plan shaped tall building. This study has been carried out experimentally and numerically by wind tunnel test and computational fluid dynamics (CFD) simulation respectively. Mean wind pressures on all the faces of the building are predicted using wind tunnel test and CFD simulation varying wind incidence angles from $0^{\circ}$ to $180^{\circ}$ at an interval of $30^{\circ}$. The accuracy of the numerically predicted results are measured by comparing results predicted by CFD with experimental results and it seems to have a good agreement with wind tunnel results. Besides wind pressures, wind flow patterns are also obtained by CFD for all the wind incidence angles. These flow patterns predict the behavior of pressure variation on the different faces of the building. For better comparison of the results, pressure contours on all the faces are also predicted by both the methods. Finally, polynomial expressions as the sine and cosine function of wind angle are proposed for obtaining mean wind pressure coefficient on all the faces using Fourier series expansion. The accuracy of the fitted expansions are measured by sum square error, $R^2$ value and root mean square error.

• 한국해안·해양공학회논문집
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• 제29권5호
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• pp.260-268
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• 2017

이 연구에서는 풍동실험을 이용하여 선박 운송용 컨테이너의 풍력특성을 조사하고, 그 결과를 토대로 컨테이너의 크기 및 중량에 따른 피해발생 풍속을 평가하고자 한다. 실험결과, 컨테이너 폭의 직각방향에 작용하는 평균 풍력계수는 12ft, 20ft, 40ft, 40ft high cube 순으로 증가하는 것으로 나타났으며, 이와 달리 깊이의 직각방향에 작용하는 평균 풍력계수는 40ft high cube, 40ft, 20ft, 12ft 순으로 증가하는 것으로 나타났다. 이러한 이유는 컨테이너의 풍상면(windward surface)의 모서리에서 박리된 난류의 전단층(shear layer)이 다시 컨테이너의 측면에 재부착(reattachment)되면서 깊이의 직각 방향에 작용하는 평균 풍력계수가 줄어든 것으로 판단된다. 전 풍향에서 컨테이너의 중량에 따른 피해발생 풍속을 평가한 결과, 컨테이너의 전도보다는 활동이 낮은 풍속에서 발생할 수 있음을 알 수 있다. 이때 가장 불리한 컨테이너는 40ft high cube이며, 활동발생 및 전도발생이 일어날 수 있는 풍속은 각각 20.4 m/s와 26.8 m/s으로 평가되었다. 또한 이 연구에서는 컨테이너의 중량과 피해발생 풍속과의 상관을 토대로 컨테이너의 중량에 따른 활동발생 및 전도발생 풍속을 평가할 수 있는 평가식을 제안하였다. 본 연구 결과는 컨테이너의 고박 설치하중평가 및 적재방법 등에 관한 가이드라인 정립에 있어 유용하게 활용될 것으로 판단된다.

• Wind and Structures
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• 제29권4호
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• pp.247-270
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• 2019

Wind-resistant design of existing cooling tower structures overlooks the impacts of rainfall. However, rainstorm will influence aerodynamic force on the tower surface directly. Under this circumstance, the structural response of the super-large cooling tower (SLCT) will become more complicated, and then the stability and safety of SLCT will receive significant impact. In this paper, surrounding wind fields of the world highest (210 m) cooling tower in Northwest China underthree typical wind velocities were simulated based on the wind-rain two-way coupling algorithm. Next, wind-rain coupling synchronous iteration calculations were conducted under 9 different wind speed-rainfall intensity combinations by adding the discrete phase model (DPM). On this basis, the influencing laws of different wind speed-rainfall intensity combinations on wind-driving rain, adhesive force of rain drops and rain pressure coefficients were discussed. The acting mechanisms of speed line, turbulence energy strength as well as running speed and trajectory of rain drops on structural surface in the wind-rain coupling field were disclosed. Moreover, the fitting formula of wind-rain coupling equivalent pressure coefficient of the cooling tower was proposed. A systematic contrast analysis on its 3D distribution pattern was carried out. Finally, coupling model of SLCT under different working conditions was constructed by combining the finite element method. Structural response, buckling stability and local stability of SLCT under different wind velocities and wind speed-rainfall intensity combinations were compared and analyzed. Major research conclusions can provide references to determine loads of similar SLCT accurately under extremely complicated working conditions.