Asymmetric Effects on Vibrations of a Cylinder in Turbulent Parallel Flows

Vibration characteristics are investigated for a cylindrical structure subject to turbulent parallel flows. Pressure fluctuations from external flows on the surface of the cylinder provide the lateral forces for oscillation motion. The fluctuating pressure in the turbulent boundary layer of the cylinder is assumed to be homogeneous. We propose a vibration mechanism involving a time scale, namely the azimuthal time delay resulting from the small-scale nonaxisymmetric perturbations to the pressure field. This mechanism is based on the propagation of pressure signals with the characteristic azimuthal time delay playing an important role in the degree of lateral force concentration, and therefore, in the flow-induced oscillation of the cylinder. In view of the proposed mechanism, the axisymmetric pressure perturbation results in a case of lateral force concentration in which the magnitudes of the resulting forcing function and of the vibration response are the maxima. These characteristics may serve as criteria to predict the upper bound on the vibration response of structures when asymmetric perturbations are present in turbulent parallel flows.