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CONTENTS
Volume 24, Number 1, January 2017
 

Abstract
Wind environment in urban residential areas is an important index to consider when evaluating the living environment. However, due to the complexity of the flow field in residential areas, it is difficult to specify the correct inflow boundary conditions in the large eddy simulation (LES). In this paper, the weighted amplitude wave superposition (WAWS) is adopted to simulate the fluctuating velocity data, which satisfies the desired target wind field. The fluctuating velocity data are given to the inlet boundary of the LES by developing an UDF script, which is implemented into the FLUENT. Then, two numerical models - the empty numerical wind tunnel model and the numerical wind tunnel model with spires and roughness elements are established based on the wind tunnel experiment to verify the present method. Finally, the turbulence generation approach presented in this paper is used to carry out a numerical simulation on the wind environment in an urban residential area in Lisbon. The computational results are compared with the wind tunnel experimental data, showing that the numerical results in the LES have a good agreement with the experimental results, and the simulated flow field with the inlet fluctuations can generate a reasonable turbulent wind field. It also shows that strong wind velocities and turbulent kinetic energy occur at the passageways, which may affect the comfort of people in the residential neighborhood, and the small wind velocities and vortexes appear at the leeward corners of buildings, which may affect the spreading of the pollutants.

Key Words
large eddy simulation; wind environment; WAWS; fluctuating wind field

Address
Lian Shen, Yan Han, Guochao Dong, Jianren Zhang and Peng Hu: School of Civil Engineering and Architecture, Changsha University of Science & Technology, Changsha, China, 410004
C.S. Cai: Department of Civil and Environmental Engineering, Louisiana State University, Baton Rouge,
USA, LA 70803



Abstract
The effects of finite cylinder free end shape on the mean and fluctuating wind pressures were investigated experimentally and numerically by using three different roof shapes: flat, conical and hemispherical. The pressure distributions on the roofs and the side walls of the finite cylinders partially immersed in a simulated atmospheric boundary layer have been obtained for three different roof shapes. Realizable k-e turbulence model was used for numerical simulations. Change in roof shapes has caused significant differences on the pressure distributions. When compared the pressure distributions on the different roofs, it is seen from the results that hemispherical roof has the most critical pressure field among the others. It is found a good agreement between numerical and experimental results.

Key Words
finite cylinder; circular flat roof; conical roof; hemispherical roof; suction pressure; realizable k-

Address
Y. Ozmen: Department of Mechanical Engineering, Karadeniz Technical University, Trabzon 61080, Turkey
E. Aksu: Naval Architecture and Marine Engineering, Karadeniz Technical University, Trabzon 61080, Turkey

Abstract
The use of nanotechnology materials and applications in the construction industry should be considered for enhancing material properties. However, the nonlinear buckling of an embedded straight concrete columns reinforced with silicon dioxide (SiO2) nanoparticles is investigated in the present study. The column is simulated mathematically with Euler-Bernoulli and Timoshenko beam models. Agglomeration effects and the characteristics of the equivalent composite are determined using Mori-Tanaka approach. The foundation around the column is simulated with spring and shear layer. The governing equations are derived using energy method and Hamilton\'s principal. Differential quadrature method (DQM) is used in order to obtain the buckling load of structure. The influences of volume percent of SiO2 nanoparticles, geometrical parameters and agglomeration on the buckling of column are investigated. Numerical results indicate that considering agglomeration effects leads to decrease in buckling load of structure.

Key Words
agglomeration; buckling; concrete column; SiO2 nanoparticles; DQM

Address
Mehdi Zamanian, Reza Kolahchi and Mahmood Rabani Bidgoli: Department of Civil Engineering, Jasb Branch, Islamic Azad University, Jasb, Iran

Abstract
Non-stationarity and non-Gaussian property are two of the most important characteristics of wind. These two features are studied in this study based on wind speed records measured at different heights from a 325 m high meteorological tower during the synoptic wind storms. By using the time-frequency analysis tools, it is found that after removing the low frequency trend of the longitudinal wind, the retained fluctuating wind speeds remain to be asymmetrically non-Gaussian distributed. Results show that such non-Gaussianity is due to the weak-stationarity of the detrended fluctuating wind speed. The low frequency components of the fluctuating wind speeds mainly contribute to the non-zero skewness, while distribution of the high frequency component is found to have high kurtosis values. By further studying the decomposed wind speed, the mechanisms of the non-Gaussian distribution are examined from the phase, turbulence energy point of view.

Key Words
full scale measurement; synoptic wind storm; signal processing; time-frequency analysis

Address
Yi Hui: Wind Engineering Research Center, College of civil engineering, Hunan University, Changsha, 410082 China
Bo Li and Qingshan Yang: Beijing\'s Key Laboratory of Structural Wind Engineering and Urban Wind Environment,
School of civil engineering, Beijing Jiaotong University, Beijing, 100044, China
Hiromasa Kawai: School of Science and Engineering, Tokyo Denki University, Ishizaka, Hatoyama, Hikigun, Saitama 350-0394, Japan


Abstract
Wind-induced fluctuating internal pressures in a building with a dominant opening can be described by a second-order non-linear differential equation. However, the accuracy and efficiency of the governing equation in predicting internal pressure fluctuations depend upon two ill-defined parameters: inertial coefficient CI and loss coefficient CL, since CI determines the un-damped oscillation frequency of an air slug at the opening, while CL controls the decay ratio of the fluctuating internal pressure. This study particularly focused on the value of loss coefficient and its influence factors including: opening configuration and location, internal volumes, as well as wind speed and approaching flow turbulence. A simplified formula was presented to predict loss coefficient, therefore an approximate relationship between the standard deviation of internal and external pressures can be estimated using Vickery\'s approach. The study shows that the loss coefficient governs the peak response of the internal pressure spectrum which, in turn, will directly influence the standard deviation of the fluctuating internal pressure. The approaching flow characteristic and opening location have a remarkable effect on the parameter CL.

Key Words
wind tunnel test; dominant opening; internal pressure; loss coefficient; Helmholtz resonance

Address
Haiwei Xu, Shice Yu and Wenjuan Lou: College of Civil Engineering and Architecture, Zhejiang University, Hangzhou 310058, China


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