Najmeh Mastari Farahani - Faculty member and Ins tructor, Department of Architecture and Urbanism, Technical and Vocational University, Alborz, Iran.
Abdollah Baghaei Daemei - School of Built Environment, College of Science, Massey University, Auckland, New Zealand
Payam Madelat - School of Engineering, Department of Civil Engineering and Architecture, Tallinn University of Technology, Estonia
Seyedeh Maryam Abbaszadegan - Faculty of Architecture and Urbanism, Soore University, Tehran, Iran

Wind load in architectural engineering can be defined as the natural load produced by air and is considered the most vital factor in design because this load significantly impacts structures, especially tall buildings. In this regard, drag force is the crucial wind force in tall building design. Even if the structure's safety is verified by using advanced technologies and high-quality materials, the vibrations caused by the wind force can still reach beyond the human comfort zone and may cause concern. The main goal of this study is to identify the wind aerodynamic factors in the urban boundary layer and evaluate the drag coefficient in tall-square buildings. Seven sample squared-plan buildings with aerodynamic modifications (corners) including recessed, rounded, and chamfered corners, and aerodynamic forms including set-back, tapered, and helical/twisted compared to the base (sharp corner) model. Autodesk Flow Design ۲۰۱۴ software was performed as a wind tunnel simulator. The software utilizes a Large Eddy Simulation (LES) turbulence model solver to account for turbulence within the wind tunnel. LES is a mathematical model for turbulence used in computational fluid dynamics of the atmospheric boundary layer. The results showed that the sq۶ with the aerodynamic tapered form had the best performance compared to other samples, which was about ۵۰%. The sq۳ sample with chamfered aerodynamic modification could reduce the building's drag coefficient and wind effect by about ۴۲%.

Wind aerodynamics, Urban boundary layer, Wind tunnel simulation, Drag coefficient, Tall buildings