Integrating topography-modified wind flows into structural and environmental wind engineering applications

Topographical features alter the trajectory of wind on the horizontal and vertical planes by creating yaw and pitch angles of wind. Near mountains, topography-induced pitch and yaw angles are confined to the lower part of the atmospheric boundary layer and have considerable magnitudes, thus they should be taken into consideration in wind engineering applications. In this study, a series of wind tunnel tests and CFD simulations are conducted to investigate how wind flows with pitch and yaw angels affect the wind loading of structures and the wind environment in built-up areas. Wind flows with yaw angles are found to create asymmetric pedestrian-level wind environments with large low-wind areas. These results can be replicated using conventional wind flows with a novel technique called the equivalent wind incidence angle method. Wind flows with small positive pitch angles exaggerate the displacements and wind loadings of structures, while negative pitch angles are advantageous for the aerodynamic performance of structures. The differential structural aerodynamics performances are attributable to differences in downwash and upwash flows, and curvature of the shear layers at the top and bottom of a structure subjected to wind flows with positive and negative pitch angles.