Numerical studies on passive and rotative suppressors for parametric instability and vortex-induced vibration phenomena

• Grant number: 16/20929-2
• Support Opportunities: Regular Research Grants
• Start date: March 01, 2017
• End date: February 28, 2019
• Field of knowledge: Engineering - Naval and Oceanic Engineering - Hydrodynamics of Ships and Ocean Systems
• Principal Investigator: Guilherme Rosa Franzini
• Grantee: Guilherme Rosa Franzini
• Host Institution: Escola Politécnica (EP). Universidade de São Paulo (USP). São Paulo , SP, Brazil

Abstract

In the offshore engineering scenario, oscillations of slender structures such as risers and TLP tethers are common problems. Particularly, two classes of problems are of interest: parametric instability phenomenon and vortex-induced vibrations (VIV).Parametric instability problems are caused by the temporal modulation of traction. Such a modulation is caused by the motions of floating units in the vertical plane. Depending on the amplitude and frequency of the traction modulation, lateral structural oscillations may occur.VIV is a particular class of flow-induced vibration that is important on risers dynamics' scenario. The maximum oscillation amplitude due to VIV is close to one diameter, however its self-excited character may decrease the structural lifespan due to material fatigue.Usually, the problems herein described are undesirable phenomena. Hence, it is natural that they receive several research efforts aiming suppression or attenuation. Among these efforts, a particular passive suppressor named NES (Nonlinear Energy Sink) can be highlighted. Such a suppressor consists on a rigid rod, hinged at the axis of the principal structure and with a tip mass.This research project aims to numerically investigate the influence of the passive suppressor parameters (mass, length, stiffness and damping constant) on the mitigation of two phenomena, namely, parametric instability and VIV. The corresponding equations of motion will be derived and integrated. VIV phenomenon will be only investigated considering rigid cylinders mounted on elastic supports with one and two degrees-of-freedom. Phenomenological models will be adopted aiming at evaluating the hydrodynamic loads.Curves and tables showing the efficiency of the passive suppressor as functions of its parameters will be obtained for the problems herein investigated. (AU)

Scientific publications

(References retrieved automatically from Web of Science and SciELO through information on FAPESP grants and their corresponding numbers as mentioned in the publications by the authors)

FRANZINI, GUILHERME ROSA; CAMPEDELLI, GIOVANNA RIBEIRO; NIGRO MAZZILLI, CARLOS EDUARDO. A numerical investigation on passive suppression of the parametric instability phenomenon using a rotative non-linear vibration absorber. INTERNATIONAL JOURNAL OF NON-LINEAR MECHANICS, v. 105, p. 249-260, OCT 2018. (17/06538-3, 16/20929-2)

UENO, TATIANA; FRANZINI, GUILHERME ROSA. Numerical studies on passive suppression of one and two degrees-of-freedom vortex-induced vibrations using a rotative non-linear vibration absorber. INTERNATIONAL JOURNAL OF NON-LINEAR MECHANICS, v. 116, p. 230-249, NOV 2019. (17/06016-7, 16/20929-2)