Aerodynamics of a 5:1 rectangular cylinder under transient accelerated and decelerated winds

The present study investigates the aerodynamic characteristics of a 5:1 rectangular cylinder subjected to transient accelerated and decelerated winds, utilizing synchronized pressure measurements in an actively controlled wind tunnel. This research addresses the limitations of existing wind-resistant design codes, which primarily consider synoptic winds, by focusing on the effects of non-synoptic winds. The results show that accelerating and decelerating winds significantly impact cylinder surface pressure, shear-layer reattachment position, spanwise cross-correlation of fluctuating pressure, and aerodynamic forces, with accelerating winds having a more pronounced effect than decelerating winds. Furthermore, the shear-layer reattachment position shifts upstream with increased wind acceleration or deceleration, resulting in a shorter separation bubble. Both accelerating and decelerating winds enhance fluctuating pressures, their spanwise correlations, flow two-dimensionality, and aerodynamic forces. Fluctuations in drag and lift coefficients exhibit an almost linear relationship with wind acceleration or deceleration.