Local scour and flow characteristics around a circular cylinder undergoing vortex-induced vibration

Vortex-induced vibration (VIV) has been extensively studied and the related findings presented in published literature. However, when the cylinder is placed near an erodible sand bed, interactions between the vibrating cylinder, flow field and local scour evidently will become very complex. The aim of this study is to provide an improved understanding of the interaction between the flow field, free vibrating cylinder and scour by using flow visualization and a new PIV measurement technique. The results show that the amplitude and frequency of the vibrating cylinder are closely related to the depth of the scour hole. Based on the qualitative observation and quantitative measurement of the flow field, vibrating cylinder and scour dimensions, three distinct scour stages are identified in this study. The characteristics of the turbulence intensity, formation and transmission of the vortices in each of these three scour stages are discussed in this paper.