• Wind and Structures
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• 제6권3호
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• pp.209-220
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• 2003

A tornado changes its wind speed and direction rapidly; therefore, it is difficult to study the effects of a tornado on buildings in a wind tunnel. In this work, the status of the tornado-structure interaction is surveyed by numerical simulation. Various models of the tornado wind field found in literature are surveyed. Three-dimensional computer modeling work using the turbulence model based on large eddy simulation is presented. The effect of tornado on a cubic building is considered for this study. The Navier-Stokes (NS) equations are approximated by finite difference method, and solved by a semi-implicit procedure. The force coefficients are plotted in time to study the effect of the Rankine-Combined Vortex Model. Some flow visualizations are also reported to understand the flow behavior around the cube.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2011년도 추계학술대회 초록집
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• pp.41.2-41.2
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• 2011

NREL NWTC Deside codes are analyzed and introduced to develop the system performance simulation program for wind turbine generator systems. In this paper, The AirfoilPrep generating the airfoil data, the IECWind generating hub-height wind data with extreme condition following IEC 61400-1, the TurbSim generating stochastic full-field turbulent wind data, the PreComp calculating structural and dynamic properties of composite blade and the BModes making mode shapes of blade and tower are explained respectively.

• Wind and Structures
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• 제11권6호
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• pp.479-496
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• 2008

In this paper, computer simulation of wind flow around a single cooling tower with louver support at the base in the KAZERUN power station in south part of IRAN is presented as a case study. ANSYS FLOTRAN, an unstructured finite element incompressible flow solver, is used for numerical investigation of wind induced pressure load on a single cooling tower. Since the effects of the wind ribs on external surface of the cooling tower shell which plays important role in formation of turbulent flow field, an innovative relation is introduced for modeling the effects of wind ribs on computation of wind pressure on cooling tower's shell. The introduced relation which follows the concept of equivalent sand roughness for the wall function is used in conjunction with two equations ${\kappa}-{\varepsilon}$ turbulent model. In this work, the effects of variation in the height/spacing ratio of external wind ribs are numerically investigated. Conclusions are made by comparison between computed pressure loads on external surface of cooling tower and the VGB (German guideline for cooling tower design) suggestions.

• Wind and Structures
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• 제37권3호
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• pp.245-254
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• 2023

In this paper, the wind-induced response of Jiayuguan wooden building (world cultural heritage) in Northwest China was studied. ANSYS finite element software was used to establish four kinds of building models under different working conditions and carry out modal analysis. The simulation results were compared with the field dynamic test results, obtaining the model which reflects the real vibration characteristics of the wooden tower. Time history data of fluctuating wind speed was obtained by MATLAB programming. Time domain method and ANSYS were used to analyze the wind-induced vibration response time history of Jiayuguan wooden building, obtaining the displacement time history curve of the structure. It was suggested that the wind-induced vibration coefficient of Jiayuguan wooden building is 1.76. Through analysis of the performance of the building under equivalent static wind load, the maximum displacement occurs in the three-story wall, gold column and the whole roof area, and the maximum displacement of the building is 5.39 cm. The ratio of the maximum stress value to the allowable value of wood tensile strength is 45 %. The research results can provide reference for the wind resistant design and protection of ancient buildings with similar structure to Jiayuguan wooden tower.

• Wind and Structures
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• 제13권5호
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• pp.385-412
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• 2010

This article provides a time-resolved characterisation of the wind field in a recently-commissioned, downdraft outflow simulator at The University of Western Ontario. A large slot jet approach to physical simulation was used. The simulator performance was assessed against field observations from a 2002 downdraft outflow near Lubbock, Texas. Outflow wind speed records were decomposed according to classical time series analysis. Length scales, characterising the coarse and fine flow structure, were determined from the time-varying mean and residual components, respectively. The simulated downdraft outflow was approximately 1200 times smaller in spatial extent than the 2002 Lubbock event.

• Wind and Structures
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• 제19권4호
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• pp.353-370
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• 2014

A new method is proposed in this study for estimating the damping ratio of a super tall building under strong wind loads with short-time measured acceleration signals. This method incorporates two main steps. Firstly, the power spectral density of wind-induced acceleration response is obtained by the wavelet transform, then the dynamic characteristics including the natural frequency and damping ratio for the first vibration mode are estimated by a nonlinear regression analysis on the power spectral density. A numerical simulation illustrated that the damping ratios identified by the wavelet spectrum are superior in precision and stability to those values obtained from Welch's periodogram spectrum. To verify the efficiency of the proposed method, wind-induced acceleration responses of the Guangzhou West Tower (GZWT) measured in the field during Typhoon Usagi, which affected this building on September 22, 2013, were used. The damping ratios identified varied from 0.38% to 0.61% in direction 1 and from 0.22% to 0.59% in direction 2. This information is expected to be of considerable interest and practical use for engineers and researchers involved in the wind-resistant design of super-tall buildings.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2008년도 춘계학술대회 논문집
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• pp.278-281
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• 2008

This study demonstrates the advantages of a shear-free structure designed to modify vertical profiles of wind speed in the atmospheric surface layer. Computational fluid dynamics(CFD) software, FLUENT is used to interpret the velocity field modification around the structure and wind turbine. The shapes of shear-free structure, installed at upstream toward prevailing wind direction, would be fences, buildings and trees, etc. According to the simulation results, it is obvious that wind shear between heights of wind turbine's blades is decreased together with a speed-up advantage. This would lead decrease of periodic wind loading caused by wind shear and power-out increase by flow uniformity and wind speed-up.

• 한국지구과학회지
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• 제25권8호
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• pp.784-798
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• 2004

복잡한 산악지형과 숲이 있는 나로 우주센터의 미규모 바람장을 MUKLIMO를 사용하여 모의하였다. 지형과 나무가 있을 때 모델의 민감도를 실험하기 위하여 각종 초기조건하에 수치모의를 수행하였다. 실험결과 나무는 평지 위에 서는 큰 영향을 미치나 언덕지형에서는 큰 영향을 미치지 못함을 알았다. 이러한 실험결과를 이용하여 나로 우주센터의 10m 상공에서의 미규모 바람장과 또, 발사장의 건설전후의 바람장도 모의하였다. 본 연구결과 MUKLIMO는 복접한 지형에서도 바람장의 수치모의가 가능하며 매우 유용함을 알았고 우주센터에서의 바람의 특성이 규명되었다.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2011년 춘계학술대회논문집
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• pp.243-248
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• 2011

The 3-dimensional flow field has been investigated by numerical analysis in a 2.5MW wind turbine blade. Complicated and separated flaw phenomena in the wind turbine blade were captured by the Reynolds-averaged Navier-Stokes(RANS) steady flaw simulation using general-purpose code, CFX and the mechanism of vortex structure behavior is elucidated. The vortical flow field in a wind turbine rotor is dominated by the tip vortex and hub separation vortex. The tip vortex starts to be formed near the blade tip leading edge. As the tip vortex develops in the tangential direction, interacting with boundary layer from the blade tip trailing edge. The hub separation vortex is generated near the blade hub leading edge and develops nearly in the span-wise direction. Furthermore, 3-dimensional blade tip shape has been designed for increasing shrift power and reducing thrust force on the wind turbine blade. It is expected that the behavior of the tip vortex and hub separation vortex plays a major role in aerodynamic and aeroacoustic characteristics.

• Wind and Structures
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• 제16권6호
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• pp.629-660
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• 2013

This paper reviews the current state-of-the-art in the numerical evaluation of wind loads on buildings. Important aspects of numerical modeling including (i) turbulence modeling, (ii) inflow boundary conditions, (iii) ground surface roughness, (iv) near wall treatments, and (vi) quantification of wind loads using the techniques of computational fluid dynamics (CFD) are summarized. Relative advantages of Large Eddy Simulation (LES) over Reynolds Averaged Navier-Stokes (RANS) and hybrid RANS-LES over LES are discussed based on physical realism and ease of application for wind load evaluation. Overall LES based simulations seem suitable for wind load evaluation. A need for computational wind load validations in comparison with experimental or field data is emphasized. A comparative study among numerical and experimental wind load evaluation on buildings demonstrated generally good agreements on the mean values, but more work is imperative for accurate peak design wind load evaluations. Particularly more research is needed on transient inlet boundaries and near wall modeling related issues.