Effect of the angle of attack on the flow around two non-identical-height square buildings in tandem arrangement

The paper investigates the flow around two non-identical height buildings, each with the same square cross-section, arranged in tandem using a particle image velocimetry technique. Fixed gap spacing between objects G = 15D (where D is the side building's length) and fixed Reynolds number Re = 17000 were considered in the study. The key goal of the research was examining the effect of the angle of attack a in the range from 0 degrees to 30 degrees on the flow structure. Considerable attention was paid to assessing the ventilation performance for the investigated flow configurations. Also, the pedestrian-level wind conditions were evaluated for all the considered values of the angle a. When a grows up, the flow is more prone to enter the gap space and elevates locally the velocity in that region. When the flow leaves the gap on the other side, it mixes with the side shear layer and both generate the recirculation area next to the downstream buildings. As a increases, the highest values of the turbulence kinetic energy are seen outside the gap space. The strength of the downwash and upwash effects on the symmetry plane becomes reduced with growing a. No clear dependency between the Strouhal number and the angle a was observed. The contribution of a to the ventilation process in the gap is different at different heights. A conversion from the weak to tolerable wind condition takes place in the gap when a increases.