Characteristics of scour and flow field beneath a forced vibrating circular cylinder

The objective of the study is to enhance the understanding of scour under a steel catenary riser (SCR), in particular the influence of the SCR dynamic motions on scour. The motion of an SCR could be attributed to the motions of the attached floating platform induced by surface waves and/or currents. In this study, a circular cylinder mounted elastically on a forced vibrating rod was installed and three vibration frequencies were tested to simulate this phenomenon. Flow visualization and high time-resolved PIV measurement techniques were applied to observe and measure the flow field around the cylinder. The results show that there are two distinct types of scour processes, depending on the imposed vibration frequency even though they have the same amplitude. Based on the qualitative observation and quantitative measurement of the flow field and turbulence characteristics, the formation and transmission of the vortices are discussed in this paper.