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CONTENTS
Volume 28, Number 1, January 2019
 

Abstract
Internal ring beams are primary components of new ring-stiffened cooling towers. In this study, numerical simulation of the internal flow field of a cooling tower with three ring beams under wind-thermal coupling effect is performed. The studied cooling tower is a 220-m super-large hyperbolic indirect natural draft cooling tower that is under construction in China and will be the World\'s highest cooling tower, the influence of peripheral radiators in operating cooling tower is also considered. Based on the simulation, the three-dimensional effect and distribution pattern of the wind loads on inner surface of the cooling tower is summarized, the average wind pressure distributions on the inner surface before and after the addition of the ring beams are analyzed, and the influence pattern of ring beams on the internal pressure coefficient value is derived. The action mechanisms behind the air flows inside the tower are compared. In addition, the effects of internal ring beams on temperature field characteristics, turbulence kinetic energy distribution, and wind resistance are analyzed. Finally, the internal pressure coefficients are suggested for ring-stiffened cooling towers under wind-thermal coupling effect. The study shows that the influence of internal stiffening ring beams on the internal pressure and flow of cooling towers should not be ignored, and the wind-thermal coupling effect should also be considered in the numerical simulation of cooling tower flow fields. The primary conclusions presented in this paper offer references for determining the internal suction of such ring-stiffened cooling towers.

Key Words
indirect natural draft cooling tower; numerical simulation; wind-thermal coupling; internal ring beam; internal pressure effect

Address
Shitang Ke: Department of Civil Engineering, Nanjing University of Aeronautics and Astronautics, 29 Yudao Street, Qinhuai District, Nanjing, Jangsu Province, China;
State Key Laboratory for Disaster Reduction in Civil Engineering, Tongji University, 1239 Sping Road, Yangpu District, Shanghai, China
Wei Yu: Department of Civil Engineering, Nanjing University of Aeronautics and Astronautics, 29 Yudao Street,
Qinhuai District, Nanjing, Jangsu Province, China
Yaojun Ge, Lin Zhao and Shuyang Cao: State Key Laboratory for Disaster Reduction in Civil Engineering, Tongji University, 1239 Sping Road, Yangpu District, Shanghai, China



Abstract
This article present the free vibration analysis of simply supported perfect and imperfect (porous) FG beams using a high order trigonometric deformation theory. It is assumed that the material properties of the porous beam vary across the thickness. Unlike other theories, the number of unknown is only three. This theory has a parabolic shear deformation distribution across the thickness. So it is useless to use the shear correction factors. The Hamilton;s principle will be used herein to determine the equations of motion. Since, the beams are simply supported the Navier\'s procedure will be retained. To show the precision of this model, several comparisons have been made between the present results and those of existing theories in the literature.

Key Words
porous FG beams; trigonometric deformation theory; free vibration; porosity

Address
Fouad Bourada: Département de Génie Civil, Institut de Technologie, Centre Universitaire de Ain Témouchent, Algérie
Abdelmoumen Anis Bousahla: Laboratoire de Modélisation et Simulation Multi-échelle, Département de Physique, Faculté des Sciences Exactes, Département de Physique, Université de Sidi Bel Abbés, Algérie;
Centre Universitaire Ahmed Zabana de Relizane, Algérie
Mohamed Bourada, Abdelghani Azzaz and Amina Zinata: Material and Hydrology Laboratory, University of Sidi Bel Abbes, Faculty of Technology, Civil Engineering Department, Algérie
Abdelouahed Tounsi: Material and Hydrology Laboratory, University of Sidi Bel Abbes, Faculty of Technology, Civil Engineering Department, Algérie;
Department of Civil and Environmental Engineering, King Fahd University of Petroleum & Minerals,
31261 Dhahran, Eastern Province, Saudi Arabia



Abstract
The accurate prediction of snow distributions under the wind action on roofs plays an important role in designing structures in civil engineering in regions with heavy snowfall. Affected by some factors such as building shapes, sizes and layouts, the snow drifting on roofs shows more three-dimensional characteristics. Thus, the research on three-dimensional snow distribution is needed. Firstly, four groups of stepped flat roofs are designed, of which the width-height ratio is 3, 4, 5 and 6. Silica sand with average radius of 0.1 mm is used to model the snow particles and then the wind tunnel test of snow drifting on stepped flat roofs is carried out. 3D scanning is used to obtain the snow distribution after the test is finished and the mean mass transport rate is calculated. Next, the wind velocity and duration is determined for numerical simulations based on similarity criteria. The adaptive-mesh method based on radial basis function (RBF) interpolation is used to simulate the dynamic change of snow phase boundary on lower roofs and then a time-marching analysis of steady snow drifting is conducted. The overall trend of numerical results are generally consistent with the wind tunnel tests and field measurements, which validate the accuracy of the numerical simulation. The combination between the wind tunnel test and CFD simulation for three-dimensional typical roofs can provide certain reference to the prediction of the distribution of snow loads on typical roofs.

Key Words
wind tunnel test; adaptive-mesh method; numerical simulation; snow drifting; 3D stepped flat roof

Address
Zhixiang Yu, Fu Zhu, Ruizhou Cao, Xiaoxiao Chen, Lei Zhao and Shichun Zhao: School of Civil Engineering, Southwest Jiaotong University, Chengdu 610031, China

Abstract
In this paper, an analytical analysis for the study of vibratory behavior and wave propagation of functionally graded plates (FGM) is presented based on a high order shear deformation theory. The manufacture of these plates\'s defects can appear in the form of porosity. This latter can question and modify the global behavior of such plates. A new shape of the distribution of porosity according to the thickness of the plate was used. The field of displacement of this theory is present of indeterminate integral variables. The modulus of elasticity and the mass density of these plates are assumed to vary according to the thickness of the plate. Equations of motion are derived by the principle of minimization of energies. Analytical solutions of free vibration and wave propagation are obtained for FGM plates simply supported by integrating the analytic dispersion relation. Illustrative examples are given also to show the effects of variation of various parameters such as (porosity parameter, material graduation, thickness-length ratio, porosity distribution) on vibration and wave propagation of FGM plates.

Key Words
functionally graded plate; higher-order plate theory; porosity; free vibration; wave propagation

Address
Riadh Bennai: Department of civil engineering, Faculty of civil engineering and architecture, University of Hassiba Benbouali of Chlef, Algeria
Hocine Fourn: Material and Hydrology Laboratory, Faculty of Technology, Department of Civil Engineering, University of Sidi Bel Abbes, Algeria
Hassen Ait Atmane: Department of civil engineering, Faculty of civil engineering and architecture, University of Hassiba Benbouali of Chlef, Algeria;
Material and Hydrology Laboratory, Faculty of Technology, Department of Civil Engineering, University of Sidi Bel Abbes, Algeria
Abdelouahed Tounsi: Material and Hydrology Laboratory, Faculty of Technology, Department of Civil Engineering, University of Sidi Bel Abbes, Algeria;
Department of Civil and Environmental Engineering, King Fahd University of Petroleum & Minerals,
31261 Dhahran, Eastern Province, Saudi Arabia
Aicha Bessaim: Material and Hydrology Laboratory, Faculty of Technology, Department of Civil Engineering, University of Sidi Bel Abbes, Algeria;
Department of Civil Engineering, Université Mustapha Stambouli de Mascara, Mascara, Algeria


Abstract
Due to developing environmental concern use of renewable energy source is very essential. The great demand for the energy supply coupled with inadequate energy sources creates an emergency to find a new solution for the energy shortage. The appropriate wind energy distribution is the fundamental requirement for the assessment of wind energy potential available at the particular site essential for the design of wind farms. Hence the proper specification of the wind speed distribution plays a vital role. In this paper the Bimodal Weibull distribution is used to estimate the Capacity factor at the proposed site. The shape and scale parameters estimated using Maximum likelihood method is used as the initial value for extrapolation. Application of this model will give an accurate result overwhelming the concept of overestimation or underestimation of Capacity factor.

Key Words
bimodal Weibull distribution ;two parameter Weibull distribution;vcut-in;vcut-off; vrated; capacity factor; vturbine

Address
C.V. Seshaiah: Department of Basic Science & Humanities, GMR Institute of Technology, Srikakulam, India
D. Indhumathy: Department of Mathematics, Sri Ramakrishna Engineering College, Coimbatore, India


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