Investigation of the effects of Eigen frequency modulation and temporal variations of the free-stream on the VIV phenomenon through phenomenological models

• Grant number: 15/03301-7
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: June 01, 2015
• End date: November 30, 2015
• Field of knowledge: Engineering - Naval and Oceanic Engineering - Hydrodynamics of Ships and Ocean Systems
• Principal Investigator: Guilherme Rosa Franzini
• Grantee: Arthur Shiniti Cato
• Host Institution: Escola Politécnica (EP). Universidade de São Paulo (USP). São Paulo , SP, Brazil

Abstract

The vortex-induced vibration phenomenon (VIV) is quite complex and plays a very important role in the dynamics of risers. Due to its complexity, VIV can be studied under three complementary approaches, namely: experiments, computational fluid dynamics and phenomenological models. This project is related to the latter approach. Phenomenological models represent the wake dynamics by means of a nonlinear oscillator (typically a van de Pol oscillator) connected to a representative oscillator of the structure. The coefficients of the nonlinear oscillator must be obtained by experimental calibration. However, many of the phenomenological models described in the literature do not consider these effects in a practical condition of oceans engineering, for example, the rate of temporal variation of the free-stream velocity or modulation of the stiffness. Thus, this research project aims to adapt an existing phenomenological model to consider both the structural stiffness and the current velocity as functions of time.