Surface roughness effect on vortec-induced vibration phenomenon in cross-flow direction of a bluff body

Abstract

This paper presents the experimental result concerning the effect of surface roughness towards the vortex-induced vibration phenomenon on the offshore structure such as riser, which is represented by a bluff body. VIV can cause fatigue damage which is due to excessive vibration in the long run. Simultaneously, the unwanted aquatic organism will be developed at a certain depth of the underwater structure and the roughness of the structure will be changed dramatically. Therefore, it is crucial to investigate the effect of the surface roughness towards the VIV. In this study, A modelled cylinder pipe was mounted on a linear slider with two springs attached at both of its ends in a working section of a circulating water tank. Sandpaper with roughness coefficient varied from 0.19 × 10-3 to 5.10 × 10-3 was utilized to represent different surface roughness on the modelled body. The test covered the subcritical range of Reynolds number from 4.9 × 103 to 1.5 × 104. The displacement of the body was measured at different reduced speeds. The results show that as the surface roughness of the body increases, the amplitude response decreases.