Measurements of the unsteady lift force on a 5:1 rectangular cylinder based on active-passive hybrid wind tunnel tests

Abstract

Active-passive hybrid wind tunnel test method was conducted to investigate the unsteady lift force on a 5:1 rectangular cylinder. Active and passive control wind tunnels are adopted to generate streamwise and grid-generated turbulences. Thus, a hybrid theoretical framework was proposed to obtain the u- and w-related aerodynamic admittances (u- and w-AAF) and investigate the effects of streamwise and vertical fluctuating winds on the unsteady behaviour of the lift force on a 5:1 rectangular cylinder at AoAs. The findings revealed that vertical wind fluctuations in the low-frequency domain dominated the lift force at low frequencies. In contrast, the streamwise component of turbulence substantially affects the energy distribution of the lift force in the high-frequency region. Notably, the contribution of streamwise wind fluctuations to unsteady lift becomes more pronounced as the AoA increases within a given range. When the AoA is further increased, the impact returns predominantly to the vertical wind fluctuations.