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Development in engineering knowledge, methods and techniques in the construction industry has provided the possibility of establishing structures that are significantly light, high and flexible. The sensitivity of high buildings against wind power is more than other ordinary buildings. Basically, wind power has an important role in the design of high buildings. Therefore, it is essential to study more carefully the effects of wind forces in the design of these structures. An important issue that must be considered in all tall building studies in the field of wind engineering is study of atmospheric boundary layer around the structures. Atmospheric boundary layer is a layer of air around the surface of the earth that at a height above the earth surface, friction has not effect on the natural flow of wind. In the present experimental research a wind tunnel was used. It generally consisted of a huge duct in collaboration with a fan in the middle. By switching on the fan, air blows into the duct. Different measurement devices were installed along the wind tunnel which made it possible to consider different test sections in width, height and longitude. In the present research a wind tunnel with 2 meter long, 1.2 meter height and 1 meter width was used with an open wind circulation system. To check every structure in the wind tunnel environment at first the atmospheric boundary in that environment should be simulated. After this stage, any structure can be placed in a wind tunnel and be examined. In this study, two buildings with the same height and cross sectional area but different in plan were examined experimentally. Both Buildings were modeled with scale of 1:600 as a fifteen floors structure with twenty cm height. Buildings had square and circular plans. Speed, pressure and turbulence at any point of the tunnel test section can be measured directly. In this study the rate of percentage of turbulence is provided in different parts of the front and back of the building. In the recent years, numerical models specially finite volume methods have been developed in the fluid sciences. In the present research, all models were simulated in Fluent software numerically. A comparison between numerical and experimental data could help one to see the ability of numerical models. Moreover, by using the numerical model many points which are not accessible in the experimental model can be recorded and analyzed. In different sides of each model the turbulence percent was measured and analyzed. Results showed that by increasing the side walls the percent of turbulence increased. The reason can be more effect of wind impact on the building surface which caused to increase the friction meaningfully. It was also concluded that covering the ground surface around the considered tall building with canopy and trees or other buildings caused more percent of turbulence. It was also observed that from a certain height of building to up, the turbulence percent was went to zero which means non friction along the wind towards the structure. The results of this study helps to provide a better understanding of the effect of plan shape of a tall building in view of wind impact.

Keywords: Wind tunnel, Percent of Turbulence, Tall Building, Canopy, Fluent

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