The impact of twisted wind on pedestrian comfort around two non-identical-height buildings in tandem arrangement: a wind tunnel study

Due to the impact of urbanization, an increasing number of buildings are being constructed near hilly terrains because of the limited availability of land resources. The influence of twisted wind profile (TWP) on pedestrian-level wind comfort surrounding two tandem non-identical-height buildings, with a height ratio H-1/H-2 ranging from 3:1 to 1:0.33, was investigated by wind tunnel experiment with two twist angles (13 degrees and 25 degrees), and compared with the conventional wind profile (CWP). The assessment of thermal comfort was based on Physiologically Equivalent Temperature (PET) using wind velocity measured from the wind tunnel and observation results. Both the mean and gust wind velocities were investigated and compared with wind assessment criteria. The results reveal a significant disparity in the mean and gust wind fields for various H-1/H-2 under both CWP and TWPs, with the influence of twist being more pronounced for step-up building configuration (H-1<H-2). The influence of TWPs on the low wind velocity region demonstrated contrasting patterns for buildings with step-up and step-down configurations. The pedestrian level wind environment varies significantly with H-1/H-2 under CWP and TWPs in the passage between the two tandem buildings, categorized as "Sitting long" for identical-height buildings and modified to "Strolling" and "Walking fast" for step-up building configuration. The twisted wind shifts the "Sitting short" area toward the direction of the approaching twisted wind flow and amplifies the "Strolling" area on the other side. The twisted wind can diminish the thermal comfort surrounding the two tandem structures during summer while enhancing the thermal environment in winter.