1 Copyright © 2015 by ASME Proceedings of the ASME 2015 34th International Conference on Ocean, Offshore and Arctic Engineering OMAE2015 May 31 – June 5, 2015, St. John’s, NL, Canada OMAE2015-41008 EXPERIMENTAL STUDY ON FLOW-INDUCED VIBRATION OF FLOATING SQUARED SECTION CYLINDERS WITH LOW ASPECT RATIO, PART I: EFFECTS OF INCIDENCE ANGLE Rodolfo T. Gonçalves (rodolfo_tg@tpn.usp.br) Dênnis M. Gambarine (dennis_maluf@tpn.usp.br) Felipe P. Figueiredo (felipe_pierrobom@tpn.usp.br) Fábio V. Amorim (fabio_amorim@tpn.usp.br) André L. C. Fujarra (afujarra@usp.br) TPN – Numerical Offshore Tank Department of Naval Architecture and Ocean Engineering, Escola Politécnica – University of São Paulo São Paulo, SP, Brazil ABSTRACT Experiments regarding flow-induced vibration on floating squared section cylinders with low aspect ratio were carried out in an ocean basin with rotating-arm apparatus. The floating squared section cylinders were elastically supported by a set of linear springs to provide low structural damping to the system. Three different aspect ratios were tested, namely / = ͳ.Ͳ, ʹ.Ͳ and ͵.Ͳ, and two different incidence angles, namely 0 and 45 degrees. The aims were to understanding the flow-induced vibration around single columns of multi-column platforms, such as semi-submersible and TLP. VIV on circular cylinders were also carried out to compare the results. The range of Reynolds number covered was 2,000 < Re < 27,000. The in- line and transverse amplitude results showed to be higher for 45-degree incidence compared with 0-degree, but the maximum amplitudes for squared section cylinders were lower compared with the circular ones. The double frequency in the in-line motion was not verified as in circular cylinders. The yaw amplitudes cannot be neglected for squared section cylinders, maximum yaw amplitudes around 10 degrees were observed for reduced velocities up to 15. Keywords: flow-induced vibration (FIV), vortex-induced vibration (VIV), vortex-induced motion (VIM), low aspect ratio, floating squared section cylinder 1. INTRODUCTION The study of flow around squared section cylinders has long been studied and is capable of exhibiting two different phenomena: galloping or vortex-induced vibration (VIV). Works can be found in the literature, among which Bearman et al. (1987) that made experiments in a wind tunnel measuring a freely-oscillating squared section cylinder under closely two- dimensional conditions in both smooth and turbulent flow. Corless & Parkinson (1988) study the interactions of two forms (galloping and VIV) oscillation on squared section cylinders. Recent studies, such as Amandolèse & Hémon (2010) show an experimental study of the VIV of a flexible mounted rigid square cylinder in a wind tunnel. Moreover, Zhao et al. (2014) investigates the free transverse flow-induced vibration (FIV) of an elastically mounted low-mass-ratio square cylinder in a free stream, at three different incidence angles: 0, 20 and 45 degrees. The majority of these studies were made in wind tunnel, i.e. the high aspect ratio squared section cylinders were submitted to airflow. Recently, works in a water flow have been made due the offshore demand, for example, semisubmersible platforms used in large scale on oil and gas exploration and production; in some cases, they have squared section cylinder columns linked by submerged pontoons. The geometry of the