• Wind and Structures
• /
• 제4권3호
• /
• pp.177-196
• /
• 2001

At present the most popular turbulence models used for engineering solutions to flow problems are the $k-{\varepsilon}$ and Reynolds stress models. The shortcoming of these models based on the isotropic eddy viscosity concept and Reynolds averaging in flow fields of the type found in the field of Wind Engineering are well documented. In view of these shortcomings this paper presents the implementation of a non-linear model and its evaluation for flow around a building. Tests were undertaken using the classical bluff body shape, a surface mounted cube, with orientations both normal and skewed at $45^{\circ}$ to the incident wind. Full-scale investigations have been undertaken at the Silsoe Research Institute with a 6 m surface mounted cube and a fetch of roughness height equal to 0.01 m. All tests were originally undertaken for a number of turbulence models including the standard, RNG and MMK $k-{\varepsilon}$ models and the differential stress model. The sensitivity of the CFD results to a number of solver parameters was tested. The accuracy of the turbulence model used was deduced by comparison to the full-scale predicted roof and wake recirculation zone lengths. Mean values of the predicted pressure coefficients were used to further validate the turbulence models. Preliminary comparisons have also been made with available published experimental and large eddy simulation data. Initial investigations suggested that a suitable turbulence model should be able to model the anisotropy of turbulent flow such as the Reynolds stress model whilst maintaining the ease of use and computational stability of the two equations models. Therefore development work concentrated on non-linear quadratic and cubic expansions of the Boussinesq eddy viscosity assumption. Comparisons of these with models based on an isotropic assumption are presented along with comparisons with measured data.

• 한국지능시스템학회논문지
• /
• 제20권2호
• /
• pp.243-250
• /
• 2010

최근 풍력발전 시스템은 가장 빨리 발전하고 있는 신재생 에너지원중 하나로 각광을 받고 있으며, 풍력발전 시스템의 주된 관심사는 어떻게 광범위한 풍속의 변화에서도 효율적으로 시스템을 동작시키는 가에 있다. 가변속 풍력발전 시스템은 고정속 풍력발전 시스템에 비해 더 높은 에너지 효율, 낮은 컴포넌트 스트레스를 달성할 수 있다는 장점을 갖는다. 일반적으로 가변속 풍력발전 시스템의 제어를 위해서는 풍속정보의 취득이 필수적으로 요구된다. 하지만 풍속계 등에 의해 측정된 풍속은 여러 요인에 의해 정확하지 않다는 문제점을 갖는다. 이에 본 연구에서는 풍속의 추정을 위한 칼만 필터와 칼만 필터에 의해 추정된 정보를 사용하여 학습된 인공신경망으로부터 최적의 로터 회전 속도를 유추할 수 있는 새로운 형태의 가변속 풍력발전 시스템을 위한 제어 알고리듬을 제안하고자 한다. 또한 Matlab의 시뮬링크를 사용하여 다양한 시뮬레이션 수행하여 제안된 기법의 유용성을 확인하고자 한다.

• Wind and Structures
• /
• 제37권4호
• /
• pp.289-302
• /
• 2023

Insulating glass units (IGUs) have been widely used in buildings in recent years due to their superior thermal insulation performance. However, because of the panel reciprocating motion and fatigue deterioration of sealants under long-term wind loads, many IGUs have the problem of early failure of watertight properties in real usage. This study aimed to propose a statistical method for wind-induced deflection of IGU panels during the whole life service period, for further precise analysis of the accumulated fatigue damage at the sealed part of the edge bond. By the estimation of the wind occurrence regularity based on wind pressure return period, the events of each wind speed interval during the whole life were obtained for the IGUs at 50m height in Beijing, which are in good agreement with the measured data. Also, the wind-induced deflection analysis method of IGUs based on the formula of airspace coefficient was proposed and verified as an improvement of the original stiffness distribution method with the average relative error compared to the test being about 3% or less. Combining the two methods above, the deformation of the outer and inner panes under wind loads during 30 years was precisely calculated, and the deflection and stress state at selected locations were obtained finally. The results show that the compression displacement at the secondary sealant under the maximum wind pressure is close to 0.3mm (strain 2.5%), and the IGUs are in tens of thousands of times the low amplitude tensile-compression cycle and several times to dozens of times the relatively high amplitude tensile-compression cycle environment. The approach proposed in this paper provides a basis for subsequent studies on the durability of IGUs and the wind-resistant behaviors of curtain wall structures.

• Structural Engineering and Mechanics
• /
• 제49권2호
• /
• pp.237-259
• /
• 2014

Wind-induced failure around screwed connections has been documented in roof and wall cladding systems made with steel sheet cold-formed panels during high wind events. Previous research has found that low cycle fatigue caused by stress concentration and fluctuating wind loads is responsible for most such failures. A dynamic load protocol was employed in this work to represent fatigue under wind effects. A finite element model and fatigue criteria were implemented and compared with laboratory experiments in order to predict the fatigue failure associated with fluctuating wind loads. Results are used to develop an analytical model which can be employed for the fatigue analysis of steel cold-formed cladding systems. Existing three dimensional fatigue criteria are implemented and correlated with fatigue damage observed on steel claddings. Parametric studies are used to formulate suitable yet simple fatigue criteria. Fatigue failure is predicted in different configurations of loads, types of connections, and thicknesses of steel folded plate cladding. The analytical model, which correlated with experimental results reported in a companion paper, was validated for the fatigue life prediction and failure mechanism of different connection types and thicknesses of cold-formed steel cladding.

• Wind and Structures
• /
• 제11권5호
• /
• pp.413-426
• /
• 2008

A wind tunnel study has been carried out to determine the influence of spacing between buildings on wind characteristics above rural and suburban type of terrain. Experiments were performed for two types of buildings, three-floor family houses and five-floor apartment buildings. The atmospheric boundary layer (ABL) models were generated by means of the Counihan method using a castellated barrier wall, vortex generators and a fetch of roughness elements. A hot wire anemometry system was applied for measurement of mean velocity and velocity fluctuations. The mean velocity profiles are in good agreement with the power law for exponent values from ${\alpha}=0.15$ to ${\alpha}=0.24$, which is acceptable for the representation of the rural and suburban ABL, respectively. Effects of the spacing density among buildings on wind characteristics range from the ground up to $0.6{\delta}$. As the spacing becomes smaller, the mean flow is slowed down, whilst, simultaneously, the turbulence intensity and absolute values of the Reynolds stress increase due to the increased friction between the surface and the air flow. This results in a higher ventilation efficiency as the increased retardation of horizontal flow simultaneously accompanies an intensified vertical transfer of momentum.

• 한국전산구조공학회논문집
• /
• 제23권2호
• /
• pp.209-215
• /
• 2010

본 논문에서는 CFD와 FEM에 기초한 진보된 전산해석 기법을 적용하였고 지진에 의한 수평 및 수직방향 기반가진 및 풍하중 효과를 동시에 고려하여 MW급 풍력발전기의 지진응답 해석을 수행하였다. 본 연구에서는 실용적인 응답특성 파악을 위해 시간영역 수치해석기법을 적용하였으며, 지진기반하중 및 풍하중에 의한 영향을 상호 비교하였다. 본 연구의 결과를 통해 관성 특성이 매우 큰 초대형 풍력발전기가 정상작동 조건 중 지진이 유발되는 경우가 타워에 유발되는 응력특성에 큰 영향을 미칠 수 있기 때문에 중요하게 고려될 필요성이 있음을 알 수 있었다.

• 한국정보통신학회:학술대회논문집
• /
• 한국해양정보통신학회 2010년도 추계학술대회
• /
• pp.295-298
• /
• 2010

본 논문에서는 강 하구 지역에 부유물체 유출시 물체의 이동과 확산 패턴을 파악하고자 plume의 생성과 변화, 외력에 대한 변동성을 연구하였다. 외력이 없는 경우 강수는 bulge와 alongshore current를 형성하며 연안을 따라 이동한다. Downwelling wind와 downcoast meanflow의 경우는 steady state와 동일한 패턴을 형성하나 수송은 강해져 연안을 따라 흐르는 물체의 이동과 확산속도가 증가할 것으로 예상된다. Upwelling wind가 부는 경우 Ekman transport에 의해 bulge가 연안으로부터 떨어져 45도 각도로 북서쪽으로 이동하는데 그 이동경로는 linear하며 바람의 세기로부터 독립적이다. 그리고 Bulge의 이동속도는 바람응력의 세기와 정비례한다. 따라서, 이 경우 부유물체의 upcoast로의 이동과 외해로의 확산이 예상된다.

• Wind and Structures
• /
• 제29권6호
• /
• pp.405-416
• /
• 2019

Aerodynamic characteristic of a small scale wind turbine under the influence of an incoming uniform wind field is studied using k-ω Shear Stress Transport turbulence model. Firstly, the lift and drag characteristics of the blade section consisting of S826 airfoil is studied using 2D simulations at a Reynolds number of 1×10⁵. After that, the full turbine including the rotational effects of the blade is simulated using Multiple Reference Frames (MRF) and Sliding Mesh Interface (SMI) numerical techniques. The differences between the two techniques are quantified. It is then followed by a detailed comparison of the turbine's power/thrust output and the associated wake development at three tip speeds ratios (λ = 3, 6, 10). The phenomenon of blockage effect and spatial features of the flow are explained and linked to the turbines power output. Validation of wake profiles patterns at multiple locations downstream is also performed at each λ. The present work aims to evaluate the potential of the numerical methods in reproducing wind tunnel experimental results such that the method can be applied to full-scale turbines operating under realistic conditions in which observation data is scarce or lacking.

• 대한기계학회논문집B
• /
• 제22권7호
• /
• pp.915-926
• /
• 1998

Velocity fields of near turbulent was behind a porous wind fence were measured using the 2-frame PTV method in a circulating water channel. The fences used in this study had different geometric porosity(.epsilon.) of 0, 20, 40 and 65%. The fence was embedded in a thin laminar boundary layer, i.e., .delta./H ~ = 0.1. Reynolds number based on the fence height H and free stream velocity(U$\_$o/) was about 8,400. As a result, a recirculating flow region was formed behind the fence for the .epsilon.=0% and 20% wind fence. For the wind fences having porosity larger than .epsilon.=40%, it was difficult to see separation bubbles behind the fence. The .epsilon.=20% porous fence reveals the maximum velocity reduction, however, the turbulent intensity and Reynolds shear stress are much greater than those of .epsilon.=40% fence. Among the wind fence tested in this study, the porous wind fence of .epsilon.=40% porosity is the most effective for abating wind erosion.

• 한국강구조학회 논문집
• /
• 제19권2호
• /
• pp.223-231
• /
• 2007

풍속의 확률분포를 고려한 통영생산기지 LNG 하역설비인 Unloading arm의 신뢰성해석을 수행하였다. 기상대의 풍속 관측기록을 이용하여 풍속의 극치분포를 추정하였으며 구조물에 가해지는 풍하중은 풍속과 풍압계수를 적용한 분포하중으로 고려하였다. 하역설비는 판요소와 입체요소를 이용하여 모델링하였고 지면접촉부는 접촉요소를 이용하여 압축력에만 저항하도록 하였다. 신뢰성해석을 위해서 주요부위의 최대응력을 표현하는 응답면을 구하였으며 이 값이 허용응력 및 항복응력을 초과하는지의 여부를 신뢰함수로 정의하여 파괴확률을 구하였다. 또한, 재료강도의 저하가 파괴확률에 미치는 영향을 파악하기 위하여 민감도 분석을 수행하였다.