Parametric analysis of a phenomenological model for vortex-induced motions of monocolumn platforms

摘要

Phenomenological models are an important branch in VIV (Vortex-Induced Vibrations) and in VIM (Vortex-Induced Motions) studies to complement the results achieved via CFD (Computational Fluid Dynamics), as the latter tool is not presently a suitable tool for intense use in engineering analysis, due to high computer power requirements. A phenomenological model for evaluating the VIM on monocolumn platforms is presented and its results are compared with experimental ones. The main objective is to present a parametric analysis, focusing on the physical significance of the modifications in parameter values. The following parameters are varied: aspect ratio (L/D), structural damping (ξ), fluid damping (γ) and Strouhal number (S). The results are presented in terms of: non-dimensional amplitudes of motion (A X/D and A Y/D), added mass coefficient (Ca) and periods of motion (T X and T Y). The phenomenological model is based on a time-domain, two degree-of-freedom structural model coupled with van der Pol wake oscillators. The governing equations are solved through fourth-order Runge-Kutta schemes.