Pedestrian-level wind environment surrounding two tandem non-identical height elevated buildings under the influence of twisted wind flows

The wind direction in urban areas characterized by hilly topography, such as Hong Kong, exhibits vertical variation along the wind profiles and exerts a significant influence on the pedestrian wind environment. This study investigated two tandem buildings with varying relative height differences (H-UB/H-DB) ranging from 3:1 to 0.33:1 and different elevated structure locations under twisted angles of 13 degrees and 25 degrees, along with their corresponding conventional wind fields by wind tunnel experiment. The findings demonstrate that the relative height differences between up- and downstream buildings significantly alter the flow field around two tandem-arranged structures. The step-up building configurations (H-UB<H-DB) exhibit heightened sensitivity to twist wind profiles, resulting in larger deviation angles (theta) of downstream low wind velocity (DSLWV) zones. Step-down building configurations (H-UB>H-DB) are relatively insensitive to the twisted wind profile. The presence of a downstream building with an elevated structure diminishes the extent of the low wind velocity (LWV) area by eliminating the near field low wind velocity (NFLWV) region while rendering the elevated building more susceptible to twist winds than non-elevated buildings. The findings provide valuable insights into the rational use of elevated buildings in mountainous regions.