Study on aerodynamic forces and aeroelasticity of an oscillating 5:1 rectangular cylinder in smooth and turbulent flow

This study examines the aerodynamic forces on an oscillating 5:1 rectangular cylinder in smooth and turbulent flow by single-degree-of-freedom (SDOF) vertical/torsional forced vibration wind tunnel tests. It quantifies the energy contributions of different components of aerodynamic forces with respect to reduced wind speed and amplitude. The critical role of turbulence in suppressing regular vortex shedding is highlighted, along with its modifying effect on fluid memory effects and aerodynamic force coefficients. The decisive role of the phase difference between self-excited-moment and torsional motion on the aeroelastic stability of an SDOF torsional conservative system is revealed. The amplitude-dependent flutter derivatives were extracted, showing significant turbulence effects and thereby notable changes in the transmission between fluid and self-excited forces. The aeroelastic response of a vertical-torsional coupled system was analyzed, revealing that turbulence-induced variations in aeroelastic stability are primarily due to changes in uncoupled aerodynamic damping. Compared to a smooth flow, the system exhibits an enhanced aeroelastic stability and smaller stable limit cycle oscillation (LCO) amplitudes within a certain wind speed range under turbulent flows. However, at high wind speeds, the response transitions to hard flutter, whereas in a smooth flow field, it generally manifests as soft flutter with stable LCO.