Self-excited forces and flow characteristics around a transversely vibrating square-section cylinder in low turbulence uniform flow

Self-excited forces arise from the interaction between the structural vibration and the surrounding flow. While this phenomenon has been extensively studied, technical challenges in fabricating aeroelastic systems and synchronizing displacement, wind pressure, and flow measurements have limited simultaneous data. To improve understanding of the self-excited force mechanism, further experimental studies are needed. This study investigates the self-excited force and flow patterns around a transversely free-vibrating square-section cylinder in a low turbulence uniform flow. Displacement at the base of the model was measured using a laser sensor, while wind pressure on the sidewalls and flow at two-thirds of the cylinder height were measured with a multiple-point synchronous pressure system, along with the flow field measured by particle image velocimetry. The self-excited force mechanism was analyzed by examining the interaction between the cylinder's vibration and the surrounding flow. When the model's displacement has minimal effect on the flow, Karman vortex shedding occurs intermittently, with symmetric vortex shedding dominating the lift force fluctuations. During vortex resonance, Karman vortex shedding prevails, with strong compression between the shear layers and the large displacement of the model generating substantial lift and self-excited forces.