Towards an understanding of marine fouling effects on VIV of circular cylinders: Aggregation effects

• Published in: Ocean engineering 2018-01, Vol.147, p.227-242
• Main Authors: Jadidi, P., Zeinoddini, M., Soltanpour, M., Zandi, A.P., Seif, M.S.
• Format: Article
• Language: English
• Subjects: Barnacles; Distance to nearest neighbour; Marine fouling; Partial coverage; Poisson cluster process; Vortex-induced vibration
• ISSN: 0029-8018; 1873-5258
• DOI: 10.1016/j.oceaneng.2017.10.037

The current study is aimed at getting a further insight into the changes the fouling brings to the Vortex Induced Vibration (VIV) of circular cylinders. Instead of regular patterns considered in previous studies, using the Poisson Cluster Process, an aggregated spatial distribution was considered for the artificial marine fouling. This is believed to better simulate the natural settlement of the marine biofouling. Different coverage ratios and fouling shapes plus regular and aggregated distributions were considered. The towing tank VIV tests were conducted on elastically mounted rigid cylinders. The Reynolds number ranged from around 7.8 × 103 to 4.9 × 104. On the whole, the maximum oscillation amplitude and the maximum lift force coefficient were meaningfully smaller in cylinders with either aggregated or regular fouling, as compared to those from the corresponding clean cylinder. Both aggregated and regular fouling were, thus, acting as VIV suppression devices. The suppression effectiveness increased by reduction in the coverage ratio of the artificial fouling. The effectiveness, however, reduced by the aggregation as compared to that with regular distribution. In general, the maximum VIV oscillations and the force coefficients appeared to be sensitive, in descending order, to coverage ratio, aggregation, flow incidence and the fouling shape. •In-water small scale towing-tank experiments in a uniform flow were conducted.•A mathematical model is presented for the laboratory simulation of the fouling with an aggregated spatial distribution.•Effects of shape, spatial distribution and coverage ratio of biofouling on the VIV of circular cylinders were studied.•Both aggregated and regular fouling act as VIV suppression devices.•The suppression, however, reduced by the aggregation as compared to that with regular distribution.