COMPARATIVE ANALYSIS OF CUT-CORNER MODIFICATION ON AERODYNAMIC PERFORMANCE OF Y-SHAPED TALL BUILDING: A COMBINED WIND TUNNEL AND CFD SIMULATION STUDY

Abstract

The ongoing vertical growth in urban areas has made wind-induced lateral loads as the determining factors for structural design of tall buildings. In order to overcome negative effects, aerodynamic shape optimization is increasingly being adopted in architecture and structural engineering fields. The tri-axially symmetric Y-shaped building form provides great strength and stability, but the extreme ends and re-entrant corners create abrupt flow separation and wind trapping, respectively. This research focuses on analyzing the performance of Y-shaped buildings that have undergone alteration in terms of having cut-corner on their limbs. A hybrid approach was used to investigate the surface pressure distribution and flow field characteristics of the conventional sharp-edged Y-shape form versus the cut corner Y-shape form. Experimental studies were performed in an open circuit Boundary Layer Wind Tunnel, employing 1:150 scale rigid Perspex models subjected to an atmospheric boundary layer of Terrain Category II. The experimental results were then used to validate the three-dimensional numerical modeling using ANSYS CFX by solving steady-state RANS equations with k-epsilon turbulence model. In order to explore the entire symmetrical effects, grazing, and asymmetrical vortex shedding, study was performed for varying wind incidence angles ranging between 00 and 1800 at 300 intervals. Comparison of data proves that the introduction of cut-corners on the Y-shaped buildings limbs has drastically altered the behavior of the shear layer and wake flow. In particular, for critical trapping orientations (600 and 1800), the recessed design creates an aerodynamic buffer, facilitating the escape of air in the inner spaces, thus lowering maximum positive pressure by about 10% to 15%, and narrowing the turbulent wake flow. This study also highlights an important aerodynamic compromise when considering highly asymmetric wind incidence (300 and 1500), at these orientations, the modified design induces faster shear layer detachment around the inner limbs, thus creating high localized negative pressures (suction) on the subsequent surfaces. Finally, the results show that while recessed corners effectively decrease base shear stress and provide better stabilization of the primary structure, they require local reinforcement of facade cladding in the re-entrant regions.