Single cylinder subjected to vortex-induced vibrations : estimating cyclic stresses for fatigue assessment

This study estimates the cyclic (i.e. fatigue) stresses on a pivoted cylinder subjected to a range of fully developed turbulent flows. The tested cylinder configuration allowed to transfer the complex fluid-structure interaction forces to a bottom-fixed stainless steel rod through a rigid connection. Thus, a direct relationship between the cylinder motion and the maximum stresses on the rod was established. The cylinder motion was recorded using a high-speed camera and its temporal position determined by means of the Digital Image Correlation technique. The results showed a dominant crossflow response with an oscillation frequency equal to half the oscillation frequency in the streamwise direction. Nevertheless, the total streamwise stress was 158 MPa, which was on average 11% lower compared to the total crossflow stress. Despite having dominant crossflow response, the higher oscillation frequency and comparable maximum stress in the streamwise direction showed that both directions should be considered for fatigue damage assessment.