Proceedings of the ASME 2016 35th International Conference on Ocean, Offshore and Arctic Engineering OMAE2016 June 19-24, 2016, Busan, South Korea OMAE2016-54632 EXPERIMENTAL STUDY ABOUT THE INFLUENCE OF THE FREE END EFFECTS ON VORTEX-INDUCED VIBRATION OF FLOATING CYLINDER WITH LOW ASPECT OF RATIO Dennis M. Gambarine 1 (dennis maluf@tpn.usp.br) Andr ´ e L. C. Fujarra 3 (andre.fujarra@ufsc.br) 1 TPN - Numerical Offshore Tank Department of Naval Architecture and Ocean Engineering Escola Polit´ ecnica - University of S˜ ao Paulo S˜ ao Paulo, SP, Brazil 3 Department of Mobility Engineering Federal University of Santa Catarina Joinville, SC, Brazil (Formerly at University of S˜ ao Paulo) Felipe P. Figueiredo 1 (felipe pierrobom@tpn.usp.br) Rodolfo T. Gonc ¸ alves 1,2 (rodolfo tg@tpn.usp.br) 2 Department of Ocean Technology, Policy, and Environment School of Frontier Sciences University of Tokyo Kashiwa-no-ha, Kashiwa, Chiba, Japan ABSTRACT Experiments regarding free-end effects on vortex-induced vi- bration (VIV) of floating circular cylinders with low aspect ratio were carried out in a towing tank. Four cylinders with low as- pect of ratio, L/D = 2 (Length / Diameter) were tested with differ- ent free end corner shape types, namely by the relation between chamfer rounding radius (r) divided by the radius of cylinder (R) (r/R = 0.0, 0.25, 0.5 and 1.0). For the initial case, r/R = 0.0 rep- resents flat tip and r/R = 1.0 the hemispherical tip. The aims were to understand the effect of different free-end types on VIV behav- ior of cylinders. The floating circular cylinders, i.e. unit mass ratio m* = 1(structural mass/displaced fluid mass) were elasti- cally supported by a set of linear springs to provide low struc- tural damping on the system and allow six degrees of freedom. The range of Reynolds number covered 3, 000 ≤ Re ≤ 20, 000. To conclude, cylinder with r/R=0.25, shows lower amplitudes in transverse direction. The same occurs for the cylinder r/R = 0, but for amplitudes of vibration in in-line direction. Behaviors of the vibration frequencies in in-line and transverse direction don’t have significantly differences. Regarding force coefficient, flat tip cylinder (r/R=0) presents higher values compared to the others however, for the lift coefficient, results converge in similar val- ues for the same velocities that were observed higher transverse amplitudes. The visualization experiments show an expressive reduction of the recirculation bubble for r/R = 0.5 model com- pared with the flat tip, can therefore justify the lower values for this model obtained in draft amplitudes and drag coefficient com- pared with the flat tip model. Keywords: Floating circular cylinder, Free-end, Low aspect ratio, Vortex-induced vibration (VIV), Vortex-induced Montion 1 Copyright c  2016 by ASME