Effect of large-scale sinusoidal gusts on the aerodynamic characteristics of a cantilevered square cylinder

Despite extensive research on the aerodynamic behavior of two-dimensional (2D) square cylinders under turbulent and oscillating flows, limited attention has been given to the effects of large-scale sinusoidal gusts on three-dimensional (3D) bluff bodies. In particular, the combined influence of large-scale gusts and three-dimensionality on unsteady aerodynamic forces and wake dynamics remains insufficiently understood. This study experimentally investigates the aerodynamic characteristics of a 3D cantilevered square cylinder (fixed at the base and free at the top) subjected to streamwise and transverse sinusoidal gusts. Wind tunnel testing is conducted to measure pressure distributions on the cylinder and wake velocity fields across various gust amplitudes and frequencies. Results reveal contrasting mechanisms: streamwise gusts amplify drag fluctuations and spanwise correlation while attenuating vortex shedding, whereas transverse gusts enhance lift response and excite higher-order modes through intensified shear-layer instabilities. Distinct from 2D cases, 3D effects, such as downwash near the free end and spanwise flow distortion, weaken spanwise coherence and aerodynamic forces, redistribute modal energy, and heighten sensitivity to gust characteristics. These findings advance understanding of 3D bluff body aerodynamics under various large-scale gusts, informing structural safety and design. © 2026 Elsevier Ltd.