Nonlinear Fluid Damping In Structure-Wake Oscillators In Modeling Vortex-Induced Vibrations

Abstract

A Nonlinear Fluid Damping (NFD) in the form of the square-velocity is applied in the response analysis of Vortex-Induced Vibrations (VIV). Its nonlinear hydrodynamic effects on the coupled wake and structure oscillators are investigated. A comparison between the coupled systems with the linear and nonlinear fluid dampings and experiments shows that the NFD model can well describe response characteristics, such as the amplification of body displacement at lock-in and frequency lock-in, both at high and low mass ratios. Particularly, the predicted peak amplitude of the body in the Griffin plot is in good agreement with experimental data and empirical equation, indicating the significant effect of the NFD on the structure motion.

Mathematical Modelling and Dynamic Analysis of a Direct-Acting Relief Valve Based on Fluid-Structure Coupling Analysis

“…Meanwhile, as there is increase of the vibration amplitude of the valve element, the intermittent impacts between the valve element and the valve seat will occur also in the longitudinal direction, which will further intensify the VIV [20]. Generally, the VIV is described by a wake oscillator model mathematically [21], based on which, Lin et al [22] studied the correlation between the fluid flow in the axial direction and the lift force acting on the structure in the longitudinal direction. Chen and Li [23] presented a fluid-structure coupling model to investigate the influences of the VIV on the structure, in which a modified van der Pol nonlinear equation was employed to simulate the vortex shedding.…”